WO2002045998A2

WO2002045998A2 - Ultrasonic collision warning system and method for a vehicle

Info

Publication number: WO2002045998A2
Application number: PCT/US2001/046962
Authority: WO
Inventors: Umraan Hasan; Sridhar Madala; Shankar Rajgopalan
Original assignee: Smartbumper, Inc.
Priority date: 2000-12-05
Filing date: 2001-12-05
Publication date: 2002-06-13
Also published as: WO2002045998A3; AU2002228857A1

Abstract

A collision warning system (32) for a vehicle (30) comprises an ultrasound transducer (34) and a processing system (58). The processing system (58) is electrically coupled to the ultrasound transducer (34) for receiving ultrasound signals from it. The processing system (58) comprising a computer program. The computer program is adapted to be executed by the processing system (58), and when executed by the processing system (58), the computer program is adapted to provide instructions to: filter out unwanted portions of the ultrasound signal corresponding to sound waves not originating from a certain transducer on the vehicle (30), to produce a filtered ultrasound signal; determine a distance and relative velocity between the vehicle (30) and one or more objects being within the distance range from the vehicle based on the filtered ultrasound signal; determine a current level of severity for a external condition within the distance range based on the relative velocity and the distance; and control the output of a warning system (38) or control a safety device (214) based on the current level of severity.

Description

SMB-001

PCT International Patent Application

ULTRASONIC COLLISION WARNING SYSTEM AND METHOD FOR A VEHICLE

by

Umraan Hasan

Sridhar Madala

Shankar Rajgopalan for Smartbumper, Inc.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of commonly owned U.S. Provisional Application having Serial Number 60/251,678 entitled SMARTBUMPER: COLLISION WARNING DEVICE filed on December 5, 2000, which is also hereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to an ultrasonic collision warning system and method for a vehicle.

BACKGROUND OF THE INVENTION

Many automakers and suppliers are developing systems using technology to better improve the safety of vehicles. Some systems being developed are inactive and merely inform a driver of possible dangers, while others being developed actively avoid or lessen the danger of a collision by overriding the driver and controlling some aspect of the vehicle control systems. Using such technologies as radar, infrared, laser, and ultrasound, many systems are designed to detect objects in front of, along side (e.g., in a blind spot), and/or behind a vehicle.

Many of the automakers and suppliers developing such systems are focusing on electromagnetic- radiation-based systems, such as radar, microwave, laser, and optical systems. However, there are many drawbacks, for example, to using radar-based systems for detecting objects near a vehicle. One disadvantage is the high energy levels involved when using radar relative to ultrasound. Due to the high energy levels of radar systems, as well as the nature of radar signals, such radar systems are regulated and restricted by the FCC, which has created a major stumbling block in getting such systems to market. Another disadvantage of radar- based systems is their cost. Radar-based systems typically cost about three times more than ultrasound systems, for example. Still another disadvantage of radar-based systems is the problem of electromagnetic radiation hazards, which must be considered and limited to safe levels. Yet another disadvantage of radar-based systems, which is related again to their high energy levels, is the problem of interference. Due to the potentially large number of vehicle radar systems coexisting on the roads if radar-based systems saturate the market, interference among radar systems of different vehicles presents numerous problems. These same disadvantages often plague microwave-based systems as well. Hence, there is a need for a better alternative than radar or microwave for detecting objects near a vehicle.

An ultrasound-based system will likely not be subject to the same FCC hindrance due to minute energy emission levels relative to radar, and because such system is not relying on electromagnetic radiation for its operation. But even with ultrasound, there is still the problem of interference, i.e., receiving a reflected ultrasound signal at one car that was emitted from another nearby car. It is generally due to, at least in part, the relatively lower power levels of ultrasound compared to radar, the shorter range of ultrasound relative to radar, the difficulty of using ultrasound in all weather conditions, and the interference issues, that many have focused on radar- and laser-based systems instead of ultrasound-based systems. Thus, there is a need for way to improve the use of ultrasound for such detection systems so that they can be effectively implemented into production vehicles and/or added as an aftermarket safety feature for existing vehicles.

BRIEF SUMMARY OF THE INVENTION

The problems and needs outlined above are addressed by the present invention. In accordance with one aspect of the present invention, a collision warning system for a vehicle is provided, which comprises: an ultrasound transducer, a processing system, and a computer program. The ultrasound transducer is adapted to receive ultrasonic sound waves and to transform the received ultrasonic sound waves to an ultrasound signal. The processing system is electrically coupled to the ultrasound transducer for receiving the ultrasound signal. The processing system comprising the computer program. The computer program is adapted to be executed by the processing system, and when executed by the processing system, the computer program is adapted to provide instructions to: filter out unwanted portions of the ultrasound signal corresponding to sound waves not originating from one or more predetermined transducers on the vehicle, to produce a filtered ultrasound signal; determine a distance between the vehicle and the one or more objects within a distance range based on the filtered ultrasound signal; determine a relative velocity between the vehicle and one or more objects being within the distance range from the vehicle based on the filtered ultrasound signal; determine a current level of severity for a external condition within the distance range based on the relative velocity and the distance; and control the output of a warning system based on the current level of severity.

In accordance with another aspect of the present invention, a collision warning system for a vehicle is provided, which comprises: an ultrasound transducer, a processing system, and a computer program. The ultrasound transducer is adapted to receive ultrasonic sound waves and to transform the received ultrasonic sound waves to an ultrasound signal. The processing system is electrically coupled to the ultrasound transducer for receiving the ultrasound signal. The processing system comprises the computer program. The computer program is adapted to be executed by the processing system, and when executed by the processing system, the computer program is adapted to provide instructions to: filter out unwanted portions of the ultrasound signal corresponding to sound waves not originating from one or more predetermined transducers on the vehicle, to produce a filtered ultrasound signal; determine a distance between the vehicle and the one or more objects within a distance range based on the filtered ultrasound signal; determine a relative velocity between the vehicle and one or more objects being within the distance range from the vehicle based on the filtered ultrasound signal; determine a current level of severity for a external condition within the distance range based on the relative velocity and the distance; and control the output of a warning system based on the current level of severity; and if the current level of severity exceeds a predetermined threshold level, log the occurrence of the current severity level in a memory device.

In accordance with yet another aspect of the present invention, a collision warning system for a vehicle is provided, which comprises: an ultrasound transducer, a processing system, and a computer program. The computer program is adapted to be executed by the processing system, and when executed by the processing system, the computer program is adapted to provide instructions to: filter out unwanted portions of the ultrasound signal corresponding to sound waves not originating from one or more predetermined transducers on the vehicle, to produce a filtered ultrasound signal; determine a distance between the vehicle and the one or more objects within a distance range based on the filtered ultrasound signal; determine a relative velocity between the vehicle and one or more objects being within the distance range from the vehicle based on the filtered ultrasound signal; determine a current level of severity for a external condition within the distance range based on the relative velocity and the distance; and if the current level of severity exceeds a predetermined threshold level, activate a safety device on the vehicle. The safety device may be an external air bag, an internal air bag, and/or a seat belt restraint system.

In accordance with still another aspect of the present invention, a collision warning system for a vehicle is provided, which comprises: an ultrasound transducer, a processing system, and a computer program. The computer program is adapted to be executed by the processing system, and when executed by the processing system, the computer program is adapted to provide instructions to: filter out unwanted portions of the ultrasound signal corresponding to sound waves not originating from one or more predetermined transducers on the vehicle, to produce a filtered ultrasound signal; determine a distance between the vehicle and the one or more objects within a distance range based on the filtered ultrasound signal; determine a relative velocity between the vehicle and one or more objects being within the distance range from the vehicle based on the filtered ultrasound signal; determine a current level of severity for a external condition within the distance range based on the relative velocity and the distance; if the current level of severity exceeds a first predetermined threshold level but is less than a second predetermined threshold level, activate a first warning signal to alert a vehicle occupant of the current level of severity and deactivate other previously activated warning signals, if any; if the current level of severity exceeds the second predetermined threshold level but is less than a third predetermined threshold level, activate a second warning signal to alert the vehicle occupant of the current level of severity and deactivate other previously activated warning signals, if any; if the current level of severity exceeds the third predetermined threshold level but is less than a fourth predetermined threshold level, activate a third warning signal to alert the vehicle occupant of the current level of severity, deactivate other previously activated warning signals, if any, and log in a memory module the occurrence of the current severity level exceeding the third predetermined threshold level; if the current level of severity exceeds the fourth predetermined threshold level, activate an external airbag, activate a safety device on the vehicle, deactivate other previously activated warning signals, if any, and log in a memory module the occurrence of the current severity level exceeding the fourth predetermined threshold level; and if the current level of severity is below the first predetermined threshold level, deactivate previously activated warning signals, if any. The one or more predetermined transducers may comprise the receiving ultrasound transducer so that there is a pulse-echo configuration. The one or more predetermined transducers may be another ultrasound transducer so that there is a pitch-catch configuration. The ultrasound transducer may be part of an array of ultrasound transducers.

In accordance with another aspect of the present invention, a method of measuring and reacting to a time of impact between a vehicle and an object within a predetermined proximity of the vehicle is provided. The method comprises the following steps, the order of which may vary: (i) emitting ultrasound from a transmitting transducer; (ii) listening for a reflection of the emitted ultrasound with a receiving transducer; (iii) receiving ultrasound with the receiving transducer to produce a received ultrasound signal; (iv) identifying hits corresponding to portions of the ultrasound signal exceeding a predetermined amplitude level within a predetermined time of flight range; (v) storing time of flight data for each hit in current class interval; (vi) adding current time of flight data to histogram of data from prior class intervals; (vii) identifying current peak on histogram; (viii) filtering and storing data corresponding to current peak in histogram from other data; (ix) computing and storing current distance to detected object; (x) computing the current relative velocity measurement between the vehicle and the detected object; (xi) computing a current time of impact measurement; (xii) determining the current level of severity for current condition based on current time of impact measurement and stored threshold levels, (a) if the current level of severity is less than the uppermost threshold level, (1) deactivating other previously activated severity level indicators and alerts, if any, (2) delaying for a random period of time, and (3) repeating the entire process again beginning at the emitting ultrasound step, (b) if the current level of severity is not less than the uppermost threshold level, (1) activating a severity level alert corresponding to the current level of severity, and (2) deactivating other previously activated severity level alerts, if any.

In accordance with yet another aspect of the present invention, a method of measuring and reacting to a time of impact between a vehicle and an object within a predetermined proximity of the vehicle is provided. The method comprises the following steps, the order of which may vary: (i) emitting ultrasound from a transmitting transducer; (ii) listening for a reflection of the emitted ultrasound with a receiving transducer; (iii) receiving ultrasound with the receiving transducer and producing an analog ultrasound signal corresponding to the received ultrasound; (iv) filtering out any parts of the analog ultrasound signal outside a predetermined bandwidth range corresponding to the receiving transducer's frequency range; (v) amplifying filtered analog ultrasound signal; (vi) increasing gain of filtered analog ultrasound signal as a function of time of flight; (vii) converting filtered analog ultrasound signal to a digital ultrasound signal; (viii) identifying hits corresponding to portions of the digital ultrasound signal exceeding a predetermined amplitude level within a predetermined time of flight range; (ix) storing time of flight data for each hit in current class interval; (x) adding current time of flight data to histogram of data from prior class intervals; (xi) identifying current peak on histogram; (xii) separating and storing data corresponding to current peak in histogram from other data; (xiii) multiplying current time of flight data by velocity of sound in air constant to compute current distance to detected object measurement; (xiv) storing current distance to detected object measurement; (xv) subtracting the current distance to detected object measurement by a prior distance to detected object measurement to compute a change in distance between measurements; (xvi) determining time between current distance measurement and the prior distance measurement; (xvii) dividing the change in distance by the time between distance measurements to compute the current relative velocity measurement between the vehicle and the detected object; (xviii) dividing the current distance to detected object measurement by the current relative velocity measurement to compute a current time of impact measurement; and (xix) determining whether the current time of impact measurement is less than an uppermost threshold setting, (a) if the current time of impact measurement is not less than the uppermost threshold setting, (1) deactivating other previously activated severity level indicators and alerts, if any, (2) delaying for a random period of time, (3) storing the period of time delayed, and (4) repeating the entire process again beginning at the emitting ultrasound step, (b) if the current time of impact measurement is less than the uppermost threshold setting, (1) comparing the current time of impact measurement to a set of stored threshold settings to determine the current level of severity for the current condition, (1.1) if the current time of impact measurement exceeds a first threshold level but is less than a second threshold level, (1.1.1) displaying a first level indicator on a severity meter display, and (1.1.2) alerting a driver that the current level of severity corresponds to a first severity level, (1.2) if the current time of impact measurement exceeds the second threshold level but is less than a third threshold level, (1.2.1) displaying a second level indicator on the severity meter display, (1.2.2) deactivating other previously activated severity level indicators and alerts, if any, and (1.2.3) alerting the driver that the current level of severity corresponds to a second severity level, (1.3) if the current time of impact measurement exceeds the third threshold level but is less than a fourth threshold level, (1.3.1) displaying a third level indicator on the severity meter display, (1.3.2) deactivating other previously activated severity level indicators and alerts, if any, (1.3.3) alerting the driver that the current level of severity corresponds to a third severity level, and (1.3.4) logging in a memory that an event corresponding to a third level of severity was detected, and (1.4) if the current time of impact measurement exceeds the fourth threshold level, (1.4.1) activating a vehicle safety device, (1.4.2) deactivating other previously activated severity level indicators and alerts, if any, and (1.4.3) logging in the memory that an event corresponding to a fourth level of severity was detected.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon referencing the accompanying drawings, in which:

FIG. 1 is a perspective view of a vehicle incorporating a first embodiment of the present invention;

FIG. 2 is a top view of the vehicle of FIG. 1;

FIG. 3 is front view of a control unit for the first embodiment; FIG.4 is a simplified schematic illustrating a block diagram for some of the hardware for the first embodiment;

FIG. 5 shows timing diagrams for sample signals from the first embodiment;

FIG. 6 is a histogram of a series of class intervals of data from the first embodiment;

FIG. 7 is flowchart illustrating a method of warning a driver of a detected object on the side of the vehicle in accordance with the first embodiment;

FIG. 8 is a flowchart for the main process of the first embodiment for a ranging ultrasound transducer;

FIG. 9 is a flowchart for the process of filtering and processing the ultrasound received, which is called upon by the flowchart of FIG. 8;

FIG. 10 is a flowchart for the process of developing and analyzing a histogram, which is called upon by the flowchart of FIG. 9;

FIG. 11 is a flowchart for the process of computing a current time of impact, which is called upon by the flowchart of FIG.9;

FIG. 12 is a flowchart for the process of computing a distance to a detected object, which is called upon by the flowchart of FIG. 11;

FIG. 13 is a flowchart for the process of computing a relative velocity between a detected object and the vehicle, which is called upon by the flowchart of FIG. 11;

FIG. 14 is a simplified schematic illustrating a block diagram for some of the hardware for a second embodiment of the present invention;

FIG. 15 is a simplified schematic illustrating a block diagram for some of the hardware for a third embodiment of the present invention;

FIG. 16 shows timing diagrams for sample signals from a fourth embodiment of the present invention;

FIG. 17 shows more timing diagrams corresponding to the timing diagrams of FIG. 16;

FIG. 18 shows timing diagrams for sample signals from a fifth embodiment of the present invention;

FIG. 19 shows more timing diagrams corresponding to the timing diagrams of FIG. 18; and

FIG. 20 shows timing diagrams for sample signals from a sixth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, wherein like reference numbers are used herein to designate like elements throughout the various views, embodiments of the present invention are illustrated and described. The figures are not necessarily drawn to scale, and in some instances the drawings have been exaggerated and/or simplified in places for illustrative purposes only. One of ordinary skill in the art will appreciate the many possible applications and variations of the present invention based on the following examples of possible embodiments of the present invention.

The term "computer program" as used herein in refers to any combination of logic sequences, algorithms, decisions, action instructions, mathematical operations or transformations, processed, methods, or steps, that are adapted to be executed by a processing system. For example, a computer program as used herein may be software adapted to be executed on a multipurpose processor (e.g., a computer); a computer program may be firmware; a computer program may be software adapted to be executed by a digital signal processor; a computer program may be hardwired into a dedicated, limited functionality hardware circuitry, burned into a dedicated circuitry, designed into a dedicated digital processing circuitry, or embedded in hardware; or a computer program may be a combination of these examples. For example, a filtering function may be performed by a dedicated filter device or dedicated filtering circuitry. For example, a mathematical operation or computation of a computer program may be performed by a comparator, an arithmetic unit, or a combination thereof. The computer program may be separable from the processing system, such as the case where the processing system is a computer and the computer program is software stored on a disc. Or, the computer program may be inseparable from the operable processing system, such as a dedicated hardwired circuitry. Or the computer program may be only partially separable from the processing system, such as a case where there is a combination of software, firmware, and dedicated hardwired circuitry.

An embodiment of the present invention provides a way to determine the relative closing rate between a vehicle and another object (e.g., another vehicle) using ultrasound. In another aspect, an embodiment of the present invention provides a way to warn a driver of a potential collision, and/or to help mitigate damages of an imminent collision, in light of the relative closing rate and distance or time to impact provided by ultrasonic readings processed in accordance with the embodiment of the present invention. Also, an embodiment of the present invention provides a way to discriminate between ultrasound emitted from another source (e.g., another vehicle) and reflected ultrasound emitted from the driver's vehicle.

The following description and FIGs. 1-13 pertain to a first embodiment of the present invention.

FIGs. 1 and 2 show a vehicle 30 having therein an ultrasonic collision warning system 32 in accordance with the first embodiment. In this example, the vehicle 30 has a front ranging ultrasonic transducer 34, which is a pulse- echo transducer. Also, as best seen in FIG.2, the vehicle 30 has two side ultrasonic transducers 36 one on each side, near the rear bumper facing towards the blind spots for the vehicle 30. The two side ultrasonic transducers 36 are also pulse-echo transducers. There is a control unit 38 mounted on the dashboard of the vehicle 30, as seen through the front windshield in FIGs. 1 and 2. The face 40 of the control unit 38 is shown in FIG. 3. In this example, the display on the face 40 of the control unit 38 comprises a speaker 42, light-emitting diode (LED) indicators 46, 48, 50, 52, and adjustment knobs 54, 56. Referring to FIG. 3, there are left and right LED indicators 46 corresponding to the left and right side ultrasonic transducers 36, respectively. The left and right LED indicators 46 can alternate between green and red. In this example, green indicates that there is no object detected by the corresponding transducer 36, and red indicates that there is an object detected within the predetermined range of the corresponding side sensor 36. Also on the face 40 of the control unit 38, there is a set of central bar LED indicators 48, 50, 52 for the front ranging ultrasonic transducer 34. These LED indicators 48, 50, 52 can vary in color also. The speaker 42 provides audible alerts and/or messages. The volume adjustment knob 54 on the left controls the speaker volume. The threshold adjustment knob 56 on the right allows a driver to adjust the minimum threshold level within a limited range, as described further below.

The control unit 38 shown in FIG. 3 is just one possible example among many. The configuration and choice of indicators, buttons, and knobs for the control unit face 40 may vary. The first embodiment is a universal aftermarket type application that is designed to allow it to mount in any vehicle. In other embodiments, the control unit 38 may be an integral part of the instrument panel or dash layout as an OEM part installed at the factory as standard equipment or installed at a car dealer as an option, for example.

FIG. 4 is simplified schematic illustrating some of the functional components of the system 32 for the first embodiment. In FIG. 4, only the circuit for the front ranging ultrasound transducer 34 is shown for illustration purposes. The control unit 38 of the first embodiment comprises a processing system 58 and the display 60 (example display shown on the face 40 of the control unit 38 in detail in FIG. 3). The processing system 58 comprises a digital signal processor (DSP) 62, a memory device 64, a device for generating the pseudo-random delay 66, a transducer driver 68, two transducer squelches 70, 72, a fast analog to digital converter 74, an amplifier 76, and a bandpass filter 78. The DSP 62 is the heart of the processing system 58 and it handles most of the processing of digital signals. The transducer driver 68 generates the signals to drive the transducer 34 and the transducer squelch 70 reduces the low level noise to clean up the signals, which are sent to the. ultrasound transducer 34 along a wire 80 to stimulated the transducer 34. The ultrasound transducer 34 then emits a burst of ultrasound in a focused beam manner 82, as illustrated in FIG.2. In the first embodiment, the ultrasound transducer 34 is designed to emit a waveform at about 40 kHz. Preferably, the ultrasound transducer 34 has a focusing cone so that the ultrasound beam 82 emitted is focused at about 10 meters from vehicle 30 with about a 1 meter diameter at 10 meters. Ultrasound focusing and the design of ultrasound transducers for emitting a specific frequency range at a chosen distance are known to those of ordinary skill in the art, and are thus not discussed in detail herein.

When the ultrasound transducer 34 receives an ultrasound signal, it passes through a bandpass filter 78 to filter out portions of the signal that are out side of a predetermined range of frequency corresponding to the receiving transducer design. Because in this example, the transmitting transducer 34 is also the receiving transducer 34, the bandpass filter 78 will filter out frequencies below about 35 kHz and above about 45 kHz, which corresponds to the frequency range that the transducer 34 is tuned to in this case. Next, the signal is amplified and the gain is increased as a function of the time of flight (e.g., more gain as time of flight increases) by the amplifier 76, as is commonly done in the field of ultrasound. Then, a transducer squelch 72 is applied on the signal to eliminate low amplitude noise. The fast analog to digital converter 74 digitizes the analog ultrasound signal at a rate of about 200-400 kHz, for example. Now that the signal is digital, the DSP 62 can readily process the ultrasound signal further. In this example, a memory device 64 is shown electrically coupled to the DSP 62. However, in some cases the separate memory device 64 may not be needed because some DSP 62 chips incorporate sufficient memory integrally within the DSP chip. The memory device 64 may also be needed to store data for long term (e.g., for logging severe events detected by the system, as described further below), as opposed to temporarily storing data for processing events and developing histograms. As will be apparent to one of ordinary skill in the art, there may be many different variations for the arrangement and configuration of the electronic components within the processing system 58.

One of the technical issues surrounding the implementation of an ultrasound detection system 32 for a vehicle 30 is that of interference among vehicles. In other words, if there are numerous vehicles within the same proximity of each other using the same make or type of ultrasound system, it presents the potential problem of one vehicle's ultrasound signal being received by another vehicle's transducer, which could interfere with the readings. To address this interference issue, the first embodiment uses randomized interpulse timing to establish a code or unique signature for the ultrasound signals emitted from the vehicle. FIG. 5 shows some example timing diagrams to help explain the randomized interpulse timing and how it is implemented and used in the first embodiment to reduce or eliminate interference from the ultrasound of other vehicles.

Randomized interpulse timing can be used to distinguish between the pulse echo ultrasound resulting from the original source versus other transmitting units, such as other vehicles equipped with similar apparatus. To distinguish the signals, the time between successive transmit pulse bursts is varied in a pseudo-random fashion. The return echo from a target will change slightly between successive transmits. However, interference from other sources, which are operating with different pseudo-random sequences, will appear to vary erratically over a wide range. By computing a histogram of the readings, as shown in FIG. 6, it is possible to easily distinguish the dominant peak 84 in the histogram corresponding to signals received from the original source. Interfering readings will appear as base line noise in the histogram and can be discarded as invalid readings. Note that the histogram has to be computed using a sliding window of the most recent readings so that new targets that appear in the path can be quickly recognized. The sliding window for the continuously updated histogram may have range of about 5-8 pulse bursts, for example. Hence, the histogram may contain the most recent eight readings at all times.

Referring to the timing diagrams of FIG. 5, Tj represents transmitting pulse bursts from a first vehicle. The length of time between each pulse burst (ti¹, ti², and t_! ³) varies randomly within a predetermined or programmed range. Rι(T represents the received signals for the first vehicle when only signals originating from Ti are received. The sequence of received pulses shown for

in FIG. 5 represents a case where the pulses of T_! are reflected from an object and received by the receiving transducer Ri. Note that the length of time between the reflections of the Ti signal have about the same pattern of the original signal T Hence, the difference or shift between the transmitted signal Ti and the received signal Rι(Tι) — t_rl — is about the same along the time axis when comparing the two signals.

In FIG. 5, T₂ represents transmitting pulse bursts from a second vehicle with the same system as the first vehicle, i.e., using the same randomized interpulse timing for its bursts of pulses. As with the first vehicle, R₂(T₂) represents the received signals for the second vehicle when only signals originating from T₂ are received. But, if the first and second vehicles are in close proximity to one another and the first vehicle receives ultrasound signals originating from the first vehicle (T and from the second vehicle (T₂), then the received signal (R^ may look like that shown as Rι(Tι & T₂). Hence, the first vehicle may receive signals from the second vehicle mixed in with signals originating from its own transducer. Without filtering the received signal with a sophisticated processing technique, the unfiltered data could be very misleading.

But, if a histogram is developed, as shown in FIG. 6, the signals originating from the first vehicle can be distinguished from those of other vehicles. If a numerous timing scales are established with their origins aligned with the signal T_b as shown in FIG. 5 below the Rι(Tj & T₂) signal, and the time of flight for each detected hit on ι(Tι & T₂) is noted on a histogram, as in FIG. 6, a peak 84 begins to emerge, which unlocks the signature code of the originally transmitted pseudo-randomly timed signal T^ Because the rate of change in the time of flight for a reflected signal from another object will vary slowly with respect to the speed of pulsing and data acquisition, a sliding window of about 5-8 pulse bursts should (when echoes are received) continuously reveal a peak 84 in the histogram to reveal the signals originating from the first vehicle. This is because the pseudo-random pattern of the interpulse timing will vary differently for each vehicle, and it can be tracked using the method just described. Hence, the pseudo-random interpulse timing provides a continuously generated and random key or signature for the signal emitted from each vehicle. Thus, the potential problems of interference among different vehicles using the same type of system are substantially reduced or eliminated by coding and tracking the signal with randomized interpulse timing.

Note that the pulse bursts emitted by the ultrasound transducer 34 may contain one pulse or many pulses. In the first embodiment it is preferred to emitted about 5-8 pulses per burst emitted. One advantage of emitting multiple pulses per burst, as is done in the first embodiment, is the increased energy level for the ultrasound, which is beneficial for obtaining a longer range of detection. Another advantage of using multiple pulses per burst of ultrasound is that it allows each burst to have a signature waveform, as discussed further below with respect to the fourth, fifth, and sixth embodiments (see, e.g., FIGs. 16-20).

FIG. 7 is a flowchart representing a simple method of processing ultrasound signals for the side ultrasound transducers 36 in accordance with the first embodiment. The flowchart of FIG. 7 describes just one side, but the other side will be the same. After the start of the process (block 86), the flowchart of FIG. 7 is a continuous loop that will repeat until interrupted (e.g., by turning off the system 32, or by turning off the vehicle ignition switch). Using a pulse-echo detection technique, the side ultrasound transducer 36 first emits an ultrasound signal (action block 88), as illustrated in FIG. 2 as ultrasound beam 90, and then listens in a receive mode for reflections of the ultrasound signal (action block 92). If no reflected signal is received, the LED indicator 46 on the control unit 38 is green (display block 94), which indicates that there is not an object detected by the side transducer 36 within a predetermined range (e.g., 3 meters for this example). This will indicate to the driver that there is probably not another vehicle within the blind spot on that side of the vehicle 30. And the loop will repeat itself (returning to action block 88). If a reflected signal is received by the transducer (decision block 96), it is then determined whether the reflected signal is within the predetermined range (decision block 98). If the received signal is not within the predetermined range, then it is disregarded, the LED indicator 46 is keep green (or changed to green if it is currently red) (display block 94), and the loop is repeated (returning to action block 88). If the received signal is within the predetermined range, then it is determined whether the LED indicator 46 is currently green (decision block 100). If the LED indicator is currently green, the LED indicator 46 is changed to red (display block 102), a single audible beep or voice message is played (action block 104) on the speaker 42, and the loop is repeated (returning to action block 88). If the LED indicator 46 is not currently green, then the LED indicator 46 is keep red (display block 106) and the loop is repeated (returning to action block 88). Thus, when an object is first detected by a side transducer 36, the control unit 38 beeps once or plays a voice message once to make the driver aware of the change in condition in the blind spot, and the LED indicator 46 is red instead of green. The LED indicator 46 then remains red as long as an object within range is detected by the side sensor.

FIGs. 8-13 are flowcharts representing a method of processing ultrasound signals for the front ranging ultrasound transducer 34 in accordance with the first embodiment. In application, the method illustrated in the flowcharts of FIGs. 8-13 is implemented by a computer program or programs and the hardware of the system 32. The flowchart of FIG. 8 is the main process 108. After beginning at the start block 110, the main process 108 is a continuous loop that will continue until ihterrupted (e.g., system turned off, vehicle ignition switched off). First, a burst of ultrasound pulses are emitted (action block 112) by the front ultrasound transducer 34. Using a pulse-echo detection technique, the front transducer 34 then listens in a receive mode for reflections of the ultrasound signal (action block 114). Upon receipt of ultrasound, the received ultrasound is then filtered and processed (subprogram block 116). The flowchart of FIG. 9 is a flowchart of the subroutine or process called upon at the filter and process ultrasound received subroutine block 116. Referring to FIG. 9, next a bandpass filter 78 removes any parts of the received ultrasound signal outside of a predetermined bandwidth or frequency range (action block 118). The filtered frequency range corresponds to the receiving transducer's frequency range. Hence, in the first embodiment with the front transducer tuned to about 40 kHz, the filtered frequency range is chosen to be about 35-45 kHz. Note that for other embodiments or variations on the first embodiment, these frequency levels and ranges may differ.

Next, the filtered analog signal is amplified (action block 120) and the gain is increased as a function of time (action block 122). The gain is increased more as the time of flight increases to compensate for loss of energy in the signal at greater distances of travel, which is a commonly known concept in the field of ultrasound. Next, the filtered and amplified analog signal is converted to a digital signal (action block 124) so that the DSP 62 can process the data. The digital signal is analyzed to identify hits (detected objects) within a predetermined range (e.g., 10 meters for example) (action block 126). Then, the time of flight information for each hit within range is stored for the current class interval (action block 128). Each cycle through the loop of the main process 108 is a class interval. The next step is to develop and analyze the current histogram (subprogram block 130), which is illustrated in the flowchart of FIG. 10. Only the most recent class intervals (e.g., last ten cycles) of data are retained in memory 64 for developing the histogram.

In FIG. 10, it is next determined whether a histogram has been started yet (decision block 132). This is most relevant when first starting up the looping of the main process 108 for a session of use (e.g., first 5-8 cycles). If there is not a histogram yet for the current session, the processing system 58 then formats and prepares an array for the histogram (action block 134). In developing the current histogram (after a histogram has been started already), the current class is stacked on or added to the most recent class intervals (action block 136) (e.g., prior 5-8 cycles through main process 108). Thus, as described above regarding FIGs. 5 and 6, due to the cycle rate of the main process loop 108, changes in the histogram should occur very gradually relative to the actual changes in the condition in front of the vehicle 30 being detected by the ultrasound transducer 34. Again as described above regarding FIGs. 5 and 6, the current peak 84 of the current histogram is identified or the tracking of the peak 84 is continued (action block 138). After identifying the peak 84 and "decoding" the data corresponding to the ultrasound signal originating from the system 32 of the vehicle 30, the data corresponding to the peak 84 is separated or filtered from any other data (e.g., signals originating from another vehicle or another source) (action block 140). Then the separated current data corresponding to the peak 84 of the histogram is stored for use in subsequent calculations (write data block 142).

After finishing the process 130 of the FIG. 10 flowchart and returning to the FIG. 9 flowchart, the next step is to compute the current time of impact (subprogram block 144), which leads to the flowchart of FIG. 11. The time of impact can be estimated based on the distance and relative velocity measurements between the vehicle 30 and the detected object obtained from the ultrasound data. Thus upon starting the process 144 of computing the current time of impact in FIG. 11, the first step is to compute the distance to the detected object (subprogram block 146), which leads to the flowchart of FIG. 12. To compute the distance using the ultrasound data, the time of flight (read data block 148) is multiplied by the velocity of sound in air (read data block 150) and divided by two (action block 152). The time of flight is the time it takes for the ultrasound signal to leave the transducer 34, reflect off of the detected object, and travel back to the transducer 34. The velocity of sound in air is a constant for purposes of the calculations. The product is divided by two because the travel time of the sound is the round trip time. Half of the round trip time is approximately the time it took to travel the distance of interest, i.e., the distance between the detected object and the vehicle 30. The resulting of this computation for the distance measurement is stored for subsequent use (write data block 154).

Returning to the flowchart of FIG . 11 , the current distance measurement is now known (data block 156). The next step is to compute the relative velocity between the vehicle 30 and the detected object (subprogram block 158), which leads to the flowchart of FIG. 13. The relative velocity is more relevant than the velocity of the vehicle 30 because the detected object may be another vehicle in motion (e.g., a second vehicle driving ahead of the first vehicle 30). The relative velocity can be obtained by dividing the change in distance between the vehicle and the detected object by the time period between the distance measurements. The time between the current distance measurement and the immediately prior distance measurement will vary due to the randomized interpulse timing, but these values are stored during each loop through the main process 108. After obtaining the current relative velocity measurement between the vehicle and the detected object (action block 160), the current relative velocity measurement is stored for subsequent use (write data block 162).

Returning to the flowchart of FIG. 11 again, the current relative velocity measurement is now known (data block 164). The next step is to compute the current estimated time of impact based on the current distance and current relative velocity measurements (action block 166). Dividing the current distance measurement by the current relative velocity measurement (action block 166) provides the current time of impact measurement, which is stored for subsequent use (write data block 168).

For the first embodiment, the closest object detected will likely be most relevant. However, the largest relative velocity measurement will also likely be most relevant in the first embodiment. However, in some cases an object farther away from the vehicle may have such a large relative velocity that it may end up having a small estimated time to impact than a slow-moving cautious. Thus in another embodiment, it may be best in some circumstances to calculate multiple time to impact values using different combinations of distance (closer, farther) and relative velocity (for an object closer or farther) to determine the shortest estimated time to impact.

Returning to the process 116 of FIG. 9, which is now complete, and then returning to the main process 108 of FIG. 8, the current time of impact measurement is now known (data block 170), which will be used in the main process 108 to determine the current level of severity for the condition in front of the vehicle 30. Hence the next step in the main process 108 of FIG. 8 is to determine whether the time of impact measurement is less than an uppermost threshold setting for the system (decision block 172). By turning the threshold adjustment knob 56 on the face 40 of the control unit 38, a driver of the vehicle 30 may adjust or alter the uppermost threshold level (manual input block 174), within predefined limits, for the time of impact. The uppermost threshold level (data block 176) for the time of impact corresponds the minimum level of severity where the driver will be warned of the condition. Hence, the driver can adjust the threshold to match his her driving style or safety preference (manual input block 174). If the driver adjusts the threshold level (manual input block 174), the stored threshold data is altered accordingly (access and update data block 178). Note also that the threshold adjustment knob 56 may be within the control unit 38, not readily accessible to the driver, to allow a manufacturer, distributor, and/or installer to adjust the thresholds as desired. In determining whether the current time of impact value is less than an uppermost threshold setting, the upper threshold data (data block 176) is accessed from memory 64 and compared to the time of impact measurement (decision block 172).

If the time of impact measurement is not less than the uppermost threshold setting, then there is no indication of a need for warning the driver. At this point the processing system 32 generates or has already generated the next delay value for the random period of time between emitting bursts of ultrasound (action block 180). If it has not already begun the delay process (action block 180) in parallel with other operations, the processing system 58 now begins the current delay period. The current pseudo-random period of time between ultrasound emissions is stored for subsequent use (i.e., for developing the histogram) (write data block 182). After the current pseudo-random delay period expires, the main loop 108 begins to repeat again at action block 112. If the time of impact measurement is less than the uppermost threshold setting (decision block 172), then the next step is to determine the current level of severity for the current condition in front of the vehicle 30 ' based on the estimated time to impact measurement (decision block 184). This determination (decision block 184) is made by comparing the current time of impact measurement to the threshold settings data (data block 186) stored in memory 64. In this example, there are four levels of warning, and hence four threshold levels. However, these levels of warning can be divided more ways or less ways, depending on the preference of the market or the buyer of the system 32.

If the current time of impact measurement exceeds a first threshold level but is less than a second threshold level, then there is a "Level 1" level of severity (condition 188). For Level 1, the level of severity based on the estimated time of impact is such that the driver needs to pay attention and be aware of the current situation ahead. The driver may already be aware of the situation ahead, but the system 32 really plays its role best in the situation where the driver is not paying attention and is not aware of the current situation ahead on the road. For Level 1 (condition 188), the first or bottom LED indicator 48 is lit (action block 190) on a severity meter display 192, which is on the face 40 of the control unit 38 (see FIG. 3). Also, for Level 1 (condition 188), an audible beeping noise and/or a voice message is emitted (action block 194) from the speaker 42 in the control unit 38 (see FIG. 3) to further alert the driver that the current level of severity corresponds to a first severity level. These Level 1 indicators and alerts continue as long as the Level 1 situation is detected.

If the current time of impact measurement exceeds the second threshold level but is less than a third threshold level, then there is a "Level 2" level of severity (condition 196). For Level 2 (condition 196), the level of severity based on the estimated time of impact is such that there is an unacceptable closing rate between the vehicle and the detected object and the driver needs to slow the vehicle or take some other action. For Level 2 (condition 196), the second or middle LED indicator 50 is lit (action block 198), along with the first LED indicator 48, on the severity meter display 192 (see FIG. 3). Also, for Level 2 (condition 196), a faster and louder (relative to Level 1) audible beeping noise and/or a voice message is emitted (action block 200) from the speaker 42 in the control unit 38 to further alert the driver that the current level of severity corresponds to a second severity level (condition 196). These Level 2 indicators and alerts continue as long as the Level 2 situation is detected.

When transitioning from Level 1 to Level 2, the Level 1 indicators and alerts are deactivated when the Level 2 indicators and alerts are activated. If for example the situation had just progressed from Level 2 to Level 1, then the Level 2 indicators and alerts would need to be deactivated when the Level 1 indicators are activated. Likewise, when transitioning from Level 3 to Level 2, from Level 3 to Level 1, etc., any other previously activated severity level indicators and alerts will need to be deactivated accordingly.

If the current time of impact measurement exceeds the third threshold level but is less than a fourth threshold level, then there is a "Level 3" level of severity (condition 202). For Level 3 (condition 202), the level of severity based on the estimated time of impact is such that the driver will have an impact if action is not taken immediately. For Level 3 (condition 202), the third or top LED indicator 52 is lit (action block 204), along with the first and second LED indicators 48, 50, on a severity meter display 192 (see FIG. 3). Also, for Level 3 (condition 202), the fastest and loudest (relative to Level 1 and Level 2) audible beeping noise and/or a voice message is emitted (action block 206) from the speaker 42 in the control unit 38 to further alert the driver that the current level of severity corresponds to a third severity level. Because Level 3 (condition 202) is presumed to be a dangerous situation, in addition to the indicators and alerts, the Level 3 event is logged in memory 64 for long term storage (write data block 208). Log information may include, for example, duration of Level 3 event, date, time, and current speed of the vehicle 30 (from the vehicle speedometer), for example. As systems become more sophisticated, other information may be logged as well, such as identity of current driver (e.g., if multiple drivers per vehicle) and location of the event (e.g., from GPS information).

The logging of Level 3 events (write data block 208) may be useful to insurance companies, for example, in determining the past driving behavior of a driver. The control unit 38 may have a socket (not shown) to allow an authorized person (e.g., government official, insurance agent) to download the log for view on a laptop computer or palm-size user interface device, for example. Such a log feature may even become a mandatory safety feature that a law or regulation could required automakers to implement in all new cars. Such log data could also be encrypted and write protected to prevent tampering or altering the data by unauthorized persons.

If the current time of impact measurement exceeds the fourth threshold level, then there is a "Level 4" level of severity (condition 210). For Level 4 (condition 210), the level of severity based on the estimated time of impact is such that an impact with the detected object is imminent and action is needed immediately to mitigate damages and/or decrease potential injury levels. For Level 4 (condition 210), an external airbag 214 is deployed (action block 212) from the front bumper 215 of the vehicle 30 (deployed configuration not shown). Also, other active safety features may be activated at this time automatically. For example, an internal airbag may deploy (not shown), the seatbelt mechanism may tighten the seat belts (not shown), and/or full brakes may be applied (not shown). Because Level 4 (condition 210) is also presumed to be a dangerous situation, the Level 4 event is logged in memory 64 for long term storage (write data block 216). In other embodiments, the external air bag 214 (see FIG. 1) may not be used or deployed, and another alternative vehicle safety device may be activated or initialized in preparation for an imminent impact. Also, in other embodiments, the external airbag may be located at another location on the vehicle 30, such as in the door or on the back bumper.

In the first embodiment of the present invention, the processing system 58 in the control unit 38 initiates and controls all functions of the collision warning system 32, processes received signals, and stores data. However, other configurations may also form other embodiments of the present invention.

For example, FIG. 14 is a simplified schematic illustrating a second embodiment of the present invention having a different hardware configuration. In the second embodiment, there is a processing system 218 located at each fransducer module 220. Hence, the ultrasound signals can be filtered, converted to digital, and processed at independently at each transducer module 220. Each transducer module 220 comprises a processing system 218, an ultrasound transducer 222, and a Controller Area Network (CAN) bus 224. The display also has a CAN bus 224. Each CAN bus 224 is electrically coupled to a serial line 226. Thus, only digital data is transmitted along the serial line 226. Because the ultrasound is not being transmitted across the vehicle 30 before being processed, as in the first embodiment (see FIGs. 1 and 2), there is less concern about noise interference and no need for expensive shielded wires to carry the ultrasound across the vehicle 30 to the processing system 58. Using CAN bus technology, less wires are required for the system 32.

FIG. 15 is a simplified schematic illustrating a third embodiment of the present invention having still another different hardware configuration. In the third embodiment, like the second embodiment, each transducer module 220 has an independent processing system 218. However, each transducer module 220 of the third embodiment comprises a wireless transmitter 228. The display 60 comprises a wireless receiver 230. Thus, the data from each transducer module 220 is sent via wireless communication to the display 60. Because there are no wires to install, the third embodiment would be great for aftermarket applications due to the ease of installation. Therefore, as will be apparent to one of ordinary skill in the art after having read this disclosure, there are many different variations of hardware that may be used in different configurations to provide other embodiments of the present invention.

The first embodiment of the present invention described above uses a randomized interpulse timing to "code" the transmitted ultrasound signal or to give it a unique signature that can be recognized in the received ultrasound signals to filter out interference from other sources and ultrasound signals transmitted by other vehicles (discussed above in conjunction with FIGs. 5 and 6). In a fourth embodiment of the present invention, a randomized chirp signal transmission method is used to "code" or place a unique signature on the transmitted ultrasound. FIG. 16 shows an example timing diagram for an ultrasound signal transmitted using the fourth embodiment.

By using randomized chirp signal transmission, spurious signals can be filtered out by encoding the transmit signal with a signature chirp signal. One way of accomplishing this is to send a chirp signal (a signal whose frequency varies with time) and process the received signal to identify the presence of a chirp signal in the received signal having the same rate or slope of frequency change as the transmitted signal. By randomizing the chirp rate and the duration and start and stop frequency settings for the chirp, it is possible to identify the unique echoes originating from the transmitter mounted on the same vehicle. For example, in FIG. 16, there are three ultrasound signal bursts A, B, and C shown on the timing diagram, each having a randomly varying frequency so that each has a unique signature. Because the processing system expects any echoed ultrasound signal received that originates from the transmitting transducer to have the same signature signals, other signals originating from other sources can be filtered out. In FIG. 16, the received timing diagram shows four ultrasound signals received A', B', Y, and C . FIG. 17 shows a timing diagram that shows the corresponding change in frequency (rate and slope) for each transmitted signal A, B, and C. Note that A has a linearly increasing frequency rate with an increasing slope. Referring to FIG. 16 again, the received signal A' also has a linearly increasing slope (see FIG. 17) that is the same as that of the transmitted signal A. The transmitted signal B in FIG. 16 has a linearly decreasing frequency rate with a decreasing slope, as shown in FIG. 17. However the next received signal Y shown in FIG. 16 has a flat slope (no change in frequency over time), as shown in FIG. 17. Because the received signal Y does not have the expected linearly decreasing frequency slope of transmitted signal B, this indicates that the received signal Y is from another source. Hence, the received signal Y can be filtered out. The subsequent received signal B' does match the frequency rate of change and slope of the transmitted signal B (see FIG. 17). Thus, the received signal B' corresponds to the transmitted signal B, as anticipated.

The fourth embodiment accounts for possible Doppler shifts induced by a moving target when processing the return chirp signal. One way of doing this easily is to select a chirp signal which is invariant in some sense to Doppler shift, such as a linear chirp. Another way is to use the velocity estimate computed during an earlier reading to correct for the Doppler shift. As shown in FIG. 17 on the receive timing diagram, for the received signal A' has a first phantom line slope 232 above a solid line slope 234, and a second phantom line slope 236 below the solid line slope 234. The first phantom line slope 232 is shifted up relative to the solid line slope 234, which indicates an upward Doppler shift. For the case of the first phantom line slope 232 that is shifted upward, this indicates that the detected object is coming towards the vehicle 30. For the case of the solid line slope 234 without a Doppler shift, the detected object is not moving relative to the vehicle 30. For the case of the second phantom line slope 236 that is Doppler shifted downward, this indicates that the detected object is moving away from the vehicle 30. Such possible Doppler shifts are also shown in phantom lines for the received signals B' and C in FIG. 17.

In a fifth embodiment of the present invention, an amplitude modulation method is used to "code" or place a unique signature on the transmitted ultrasound. FIG. 18 shows an example timing diagram for an ultrasound signal transmitted using the fifth embodiment. Using an amplitude modulation method, spurious signals can be filtered out by encoding the transmit signal with an amplitude signature having a random digital bit pattern (such as high, low, high). The received ultrasound signals are processed to look for this unique pattern. By randomizing the pattern it is possible to discard signals from other sources. For example, in FIG. 18 the transmitted ultrasound signal first has high amplitude, then low amplitude, then high amplitude, and then low amplitude again. By viewing the amplitude level of the peaks in a digital bit pattern, as shown in FIG. 19, the pattern is more apparent. Thus, the processing system is expecting the next echoed signal from the same vehicle to follow the same digital bit pattern. Thus, the first received signal matches the transmitted signal (see FIGs. 18 and 19). But, the second received signal having the digital bit pattern of low, high, low, high, high, does not match a signal transmitted by the same vehicle, and thus it originated from another source and should be filtered out.

FIG. 20 shows timing diagrams for a transmitted signal from a sixth embodiment of the present invention that uses a combination of randomized interpulse timing, randomized chirp signal transmission, and amplitude modulation to encode a unique signature on the transmitted ultrasound signal. Hence, there may be other embodiments using any combination of these coding techniques to provide a unique signature on the transmitted signal, which will allow received ultrasound signals from other sources to be filtered out.

Although in the first embodiment, the ranging ulfrasound transducer is mounted on the front of the vehicle, one or more of such ranging ultrasound transducers may be mounted, in alternative or in addition, on another portion of the vehicle aimed in another direction (e.g., back, side). It should be noted that a pitch-catch transducer configuration may also be used in alternative to a pulse-echo transducer. Also, an array of transmitting and/or receiving transducers may be used at a single location instead of a single fransducer. Such variations in the present invention will be apparent to one of ordinary skill in the art.

Although the vehicle shown in FIGs. 1 and 2 is a car, an embodiment of the present invention may be used for or applied to many other vehicles as well, including but not limited to the following examples: a track; a bus; a tractor; a trailer; a tractor frailer; a crane; a bulldozer; a plow; a train; a metro rail; a motorcycle; bicycle; a tricycle or three-wheeler; a tank; a two-wheeled self-righting vehicle (e.g., self-balancing scooter, IT, Segway vehicle); an unmanned vehicle; an autonomous robot; a remote controlled robot; a hovercraft; a boat; and a personal watercraft.

It will be appreciated by those skilled in the art having the benefit of this disclosure that embodiments of this invention provide ways to use an ultrasound system to measure relative velocity and distance between a vehicle and an object to obtain the estimated time to impact, to classify the conditions detected under one of several severity levels or danger levels, to alert or warn a driver of the level of severity, and if needed, activate an active safety device. It should be understood that the drawings and detailed description herein are to be regarded in an illustrative rather than a restrictive manner, and are not intended to limit the invention to the particular forms and examples disclosed. On the contrary, the invention includes any further modifications, changes, rearrangements, substitutions, alternatives, design choices, and embodiments apparent to those of ordinary skill in the art, without departing from the spirit and scope of this invention, as defined by the following claims. Thus, it is intended that the following claims be interpreted to embrace all such further modifications, changes, rearrangements, substitutions, alternatives, design choices, and embodiments.

Claims

CLAIMS:

1. A collision warning system for a vehicle, comprising: an ultrasound transducer adapted to receive ultrasonic sound waves and to transform the received ultrasonic sound waves to an ultrasound signal; a processing system electrically coupled to the ultrasound transducer for receiving the ultrasound signal, the processing system comprising: a computer program adapted to be executed by the processing system, and when executed by the processing system, the computer program being adapted to provide instructions to: filter out unwanted portions of the ultrasound signal corresponding to sound waves not originating from one or more predetermined fransducers on the vehicle, to produce a filtered ultrasound signal, determine a distance between the vehicle and the one or more objects within a distance range based on the filtered ultrasound signal, determine a relative velocity between the vehicle and one or more objects being within the distance range from the vehicle based on the filtered ultrasound signal, determine a current level of severity for a external condition within the distance range based on the relative velocity and the distance, and control the output of a warning system based on the current level of severity.

2. A collision warning system for a vehicle, comprising: an ultrasound transducer adapted to receive ultrasonic sound waves and to transform the received ultrasonic sound waves to an ultrasound signal; a processing system electrically coupled to the ultrasound fransducer for receiving the ulfrasound signal, the processing system comprising: a computer program adapted to be executed by the processing system, and when executed by the processing system, the computer program being adapted to provide instructions to: filter out unwanted portions of the ultrasound signal corresponding to sound waves not originating from one or more predetermined transducers on the vehicle, to produce a filtered ultrasound signal, determine a distance between the vehicle and the one or more objects within a distance range based on the filtered ulfrasound signal, determine a relative velocity between the vehicle and one or more objects being within the distance range from the vehicle based on the filtered ultrasound signal, determine a current level of severity for a external condition within the distance range based on the relative velocity and the distance, control the output of a warning system based on the current level of severity, and if the current level of severity exceeds a predetermined threshold level, log the occurrence of the current severity level in a memory device.

3. A collision warning system for a vehicle, comprising: an ultrasound transducer adapted to receive ultrasonic sound waves and to transform the received ultrasonic sound waves to an ultrasound signal; a processing system electrically coupled to the ultrasound fransducer for receiving the ulfrasound signal, the processing system comprising: a computer program adapted to be executed by the processing system, and when executed by the processing system, the computer program being adapted to provide instructions to: filter out unwanted portions of the ultrasound signal corresponding to sound waves not originating from one or more predetermined transducers on the vehicle, to produce a filtered ultrasound signal, determine a distance between the vehicle and the one or more objects within a distance range based on the filtered ulfrasound signal, determine a relative velocity between the vehicle and one or more objects being within the distance range from the vehicle based on the filtered ultrasound signal, determine a current level of severity for a external condition within the distance range based on the relative velocity and the distance, and if the current level of severity exceeds a predetermined threshold level, activate a safety device on the vehicle.

4. The collision warning system of claim 3, wherein the safety device is an external air bag.

5. The collision warning system of claim 3, wherein the safety device is an internal air bag.

6. The collision warning system of claim 3, wherein the safety device is a seat belt restraint system.

7. A collision warning system for a vehicle, comprising: an ultrasound transducer adapted to receive ultrasonic sound waves and to transform the received ultrasonic sound waves to an ultrasound signal; a processing system electrically coupled to the ulfrasound transducer for receiving the ulfrasound signal, the processing system comprising: a computer program adapted to be executed by the processing system, and when executed by the processing system, the computer program being adapted to provide instructions to: filter out unwanted portions of the ultrasound signal corresponding to sound waves not originating from one or more predetermined transducers on the vehicle, to produce a filtered ultrasound signal, determine a distance between the vehicle and the one or more objects within a distance range based on the filtered ultrasound signal, determine a relative velocity between the vehicle and one or more objects being within the distance range from the vehicle based on the filtered ultrasound signal, determine a current level of severity for a external condition within the distance range based on the relative velocity and the distance, if the current level of severity exceeds a first predetermined threshold level but is less than a second predetermined threshold level, activate a first warning signal to alert a vehicle occupant of the current level of severity and deactivate other previously activated warning signals, if any, if the current level of severity exceeds the second predetermined threshold level but is less than a third predetermined threshold level, activate a second warning signal to alert the vehicle occupant of the current level of severity and deactivate other previously activated warning signals, if any, if the current level of severity exceeds the third predetermined threshold level but is less than a fourth predetermined threshold level, activate a third warning signal to alert the vehicle occupant of the current level of severity, deactivate other previously activated warning signals, if any, and log in a memory module the occurrence of the current severity level exceeding the third predetermined threshold level, if the current level of severity exceeds the fourth predetermined threshold level, activate an external airbag, activate a safety device on the vehicle, deactivate other previously activated warning signals, if any, and log in a memory module the occurrence of the current severity level exceeding the fourth predetermined threshold level, and if the current level of severity is below the first predetermined threshold level, deactivate previously activated warning signals, if any.

8. The collision warning system of claim 7, wherein the one or more predetermined transducers comprises the ultrasound fransducer so that there is a pulse-echo configuration.

9. The collision warning system of claim 7, wherein the one or more predetermined fransducers is another ultrasound transducer so that there is a pitch-catch configuration.

10. The collision warning system of claim 7, wherein the ultrasound transducer is part of an array of ultrasound fransducers.

11. A method of measuring and reacting to a time of impact between a vehicle and an object within a predetermined proximity of the vehicle, the method comprising the steps of: emitting ultrasound from a transmitting transducer; listening for a reflection of the emitted ulfrasound with a receiving fransducer; receiving ultrasound with the receiving transducer to produce a received ultrasound signal; identifying hits corresponding to portions of the ultrasound signal exceeding a predetermined amplitude level within a predetermined time of flight range; storing time of flight data for each hit in current class interval; adding current time of flight data to histogram of data from prior class intervals; identifying current peak on histogram; filtering and storing data corresponding to current peak in histogram from other data; computing and storing current distance to detected object; computing the current relative velocity measurement between the vehicle and the detected object; computing a current time of impact measurement; determining the current level of severity for current condition based on current time of impact measurement and stored threshold levels, if the current level of severity is less than the uppermost threshold level, deactivating other previously activated severity level indicators and alerts, if any, delaying for a random period of time, and repeating the entire process again beginning at the emitting ulfrasound step, if the current level of severity is not less than the uppermost threshold level, activating a severity level alert corresponding to the current level of severity, and deactivating other previously activated severity level alerts, if any.

12. A method of measuring and reacting to a time of impact between a vehicle and an object within a predetermined proximity of the vehicle, the method comprising the steps of: emitting ultrasound from a transmitting transducer; listening for a reflection of the emitted ultrasound with a receiving transducer; receiving ultrasound with the receiving transducer and producing an analog ultrasound signal corresponding to the received ultrasound; filtering out any parts of the analog ultrasound signal outside a predetermined bandwidth range corresponding to the receiving transducer's frequency range; amplifying filtered analog ultrasound signal; increasing gain of filtered analog ultrasound signal as a function of time of flight; converting filtered analog ulfrasound signal to a digital ultrasound signal; identifying hits corresponding to portions of the digital ultrasound signal exceeding a predetermined amplitude level within a predetermined time of flight range; storing time of flight data for each hit in current class interval; adding current time of flight data to histogram of data from prior class intervals; identifying current peak on histogram; separating and storing data corresponding to current peak in histogram from other data; multiplying current time of flight data by velocity of sound in air constant to compute current distance to detected object measurement; storing current distance to detected object measurement; subtracting the current distance to detected object measurement by a prior distance to detected object measurement to compute a change in distance between measurements; determining time between current distance measurement and the prior distance measurement; dividing the change in distance by the time between distance measurements to compute the current relative velocity measurement between the vehicle and the detected object; dividing the current distance to detected object measurement by the current relative velocity measurement to compute a current time of impact measurement; determining whether the current time of impact measurement is less than an uppermost threshold setting, if the current time of impact measurement is not less than the uppermost threshold setting, deactivating other previously activated severity level indicators and alerts, if any, delaying for a random period of time, storing the period of time delayed, and repeating the entire process again beginning at the emitting ultrasound step, if the current time of impact measurement is less than the uppermost threshold setting, comparing the current time of impact measurement to a set of stored threshold settings to determine the current level of severity for the current condition, if the current time of impact measurement exceeds a first threshold level but is less than a second threshold level, displaying a first level indicator on a severity meter display, and alerting a driver that the current level of severity corresponds to a first severity level, if the current time of impact measurement exceeds the second threshold level but is less than a third threshold level, displaying a second level indicator on the severity meter display, deactivating other previously activated severity level indicators and alerts, if any, and alerting the driver that the current level of severity corresponds to a second severity level, if the current time of impact measurement exceeds the third threshold level but is less than a fourth threshold level, displaying a third level indicator on the severity meter display, deactivating other previously activated severity level indicators and alerts, if any, alerting the driver that the current level of severity corresponds to a third severity level, and logging in a memory that an event corresponding to a third level of severity was detected, and if the current time of impact measurement exceeds the fourth threshold level, activating a vehicle safety device, deactivating other previously activated severity level indicators and alerts, if any, and logging in the memory that an event corresponding to a fourth level of severity was detected.