JP2007307940A - Electric power steering device - Google Patents

Abstract

An electric power steering apparatus capable of selecting an optimal rotor position estimation algorithm of a brushless motor for assisting steering is provided.
First estimation means (S8) for injecting a high-frequency voltage (or high-frequency current) into a brushless motor for assisting steering and estimating the rotor position of the brushless motor based on the response current (or response voltage); Based on the detected phase voltage and phase current, second estimation means (S6) for estimating the rotor position and determination means (S4) for determining whether the steering torque (S2) detected by the torque sensor is equal to or greater than a threshold value. ), And when the determination means determines that it is not greater than or equal to the threshold value, the rotor position estimated by the first estimation means (S8) is determined. When the determination means determines that it is equal to or greater than the threshold value, the second estimation means (S6) The brushless motor is driven based on the estimated rotor position.
[Selection] Figure 3

Description

  The present invention includes a torque sensor that detects a steering torque applied to a steering member of a vehicle, and a brushless motor for assisting steering, and is based on the estimated rotor position of the brushless motor and according to the steering torque detected by the torque sensor. The present invention relates to an electric power steering device that drives a brushless motor so as to allow a current to flow.

  An electric power steering device mounted on a vehicle assists the steering force of the vehicle with an electric motor, and detects a steering torque applied to the steering wheel to a steering mechanism connected to the steering wheel via a steering shaft. A torque sensor and an electric motor that assists the operation of the steering mechanism are provided, and the operation force to the steering wheel is reduced by driving the electric motor according to the steering torque detected by the torque sensor.

  In recent years, brushless motors have been adopted for steering assisting electric motors provided in the electric power steering apparatus in order to cope with higher output. A brushless motor is a motor that rotates a rotor by controlling a waveform forming circuit that includes a permanent magnet in the rotor and generates a rotating magnetic field in the stator based on the (rotation) position of the rotor. Loss, mechanical noise, and electrical noise from the brush do not occur.

A brushless motor requires a sensor to detect the position of the rotor, but with the development of a control algorithm that estimates the rotor position, a sensorless brushless motor that does not use the rotor position sensor has been adopted. It is coming.
There are roughly two types of control algorithms for estimating the rotor position. One is to inject a high-frequency voltage (high-frequency current) superimposed on the voltage of the brushless motor and estimate the rotor position based on the amplitude change of the response current (response voltage) due to the magnetic flux change of the permanent magnet of the rotor. Is the method. The other is a method for estimating the rotor position based on the phase voltage and phase current of the brushless motor.

  In Patent Document 1, the DC motor is driven for a driving time set so that the angular acceleration of the DC motor is substantially constant by a predetermined driving torque, and the driving time of the DC motor and the generated voltage of the DC motor after the driving are calculated. Discloses a DC motor rotation angle and load torque detection method, a DC motor control device, and an electric power steering device that estimate the rotation angle during driving of the DC motor.

Non-Patent Document 1 describes an example of a method for estimating a rotor position by injecting a high-frequency voltage into a brushless motor. Non-Patent Document 2 describes a phase voltage and a phase current detected by the brushless motor. An example of a method for estimating the rotor position (observer method) is described.
Japanese Patent Laid-Open No. 9-331693 “A New Initial Position Estimation Method for SPM Synchronous Motors by Rotating High-Frequency Voltage Application” IEICE Transactions D, Vol. "Sensorless control of salient pole type permanent magnet synchronous motor based on extended induced voltage model" IEICE Transactions D, Vol. 122, No. 12, 2002

As described above, in the sensorless brushless motor, the rotor position is obtained by the estimation algorithm. However, the stability of the estimated rotor position differs depending on the number of rotations of the motor and the output torque. However, there is a problem that it is necessary to select an optimal rotor position estimation algorithm.
For example, in a method of injecting a high-frequency voltage or high-frequency current into a brushless motor, the injected voltage or current can adversely affect the operation of the brushless motor. It is desirable to use the method based on stopping at low speed and low speed rotation.
In addition, when the rotor position estimation algorithm fails, there is a problem that the behavior of the motor becomes unstable and the steering assist force is lost, or in the worst case, the motor may be locked.

The present invention has been made in view of the above-described circumstances, and the first to fourth inventions provide an electric power steering apparatus that can select an optimal rotor position estimation algorithm for a brushless motor for steering assistance. The purpose is to do.
According to a fifth aspect of the present invention, there is provided an electric power steering device that does not cause unstable behavior of the motor, loss of steering assist force, and lock of the motor even when the rotor position estimation algorithm of the brushless motor for assisting steering is in trouble. For the purpose.

  An electric power steering apparatus according to a first aspect of the present invention includes a torque sensor that detects a steering torque applied to a steering member of a vehicle, a single-phase or multiple-phase brushless motor for assisting steering, and a voltage that detects a phase voltage of the brushless motor. Detecting means; current detecting means for detecting a phase current of the brushless motor; and a high frequency voltage (or high frequency current) is injected into the brushless motor, and the rotor position of the brushless motor is based on the response current (or response voltage). First estimation means for estimating the rotor position, and second estimation means for estimating the rotor position based on the phase voltage and phase current detected by the voltage detection means and the current detection means, and the first estimation means or the second estimation means. Based on the rotor position estimated by the estimating means, the brushless motor is supplied such that a current corresponding to the steering torque detected by the torque sensor flows. In the electric power steering apparatus for driving the motor, a determination means for determining whether or not the steering torque detected by the torque sensor is equal to or greater than a threshold is provided. The brushless motor is configured to be driven based on the rotor position estimated by the second estimating means when the determining means determines that the rotor position estimated by the first estimating means is greater than or equal to a threshold value. It is characterized by.

  An electric power steering apparatus according to a second aspect of the present invention is a torque sensor that detects a steering torque applied to a steering member of a vehicle, a single-phase or multiple-phase brushless motor for assisting steering, and a voltage that detects a phase voltage of the brushless motor. Detecting means; current detecting means for detecting a phase current of the brushless motor; and a high frequency voltage (or high frequency current) is injected into the brushless motor, and the rotor position of the brushless motor is based on the response current (or response voltage). First estimation means for estimating the first position, second estimation means for estimating the rotor position based on the phase voltage and phase current detected by the voltage detection means and the current detection means, and vehicle speed acquisition means for acquiring the speed of the vehicle A steering torque detected by the torque sensor based on a rotor position estimated by the first estimating means or the second estimating means, In the electric power steering apparatus that drives the brushless motor so as to flow a current according to the speed acquired by the vehicle speed acquisition means, it is determined whether or not the speed acquired by the vehicle speed acquisition means is greater than or equal to a threshold value. Provided with a determination means, and when the determination means determines that it is not greater than or equal to the threshold value, the second estimation means includes the rotor position estimated by the first estimation means when the determination means determines that the value is greater than or equal to the threshold value. The brushless motor is configured to be driven based on the estimated rotor position.

  An electric power steering apparatus according to a third aspect of the present invention is a torque sensor that detects a steering torque applied to a steering member of a vehicle, a single-phase or multiple-phase brushless motor for assisting steering, and a voltage that detects a phase voltage of the brushless motor. Detecting means; current detecting means for detecting a phase current of the brushless motor; and a high frequency voltage (or high frequency current) is injected into the brushless motor, and the rotor position of the brushless motor is based on the response current (or response voltage). First estimation means for estimating the rotor position, and second estimation means for estimating the rotor position based on the phase voltage and phase current detected by the voltage detection means and the current detection means, and the first estimation means or the second estimation means. Based on the rotor position estimated by the estimating means, the brushless motor is supplied such that a current corresponding to the steering torque detected by the torque sensor flows. An electric power steering apparatus for driving the vehicle, comprising: means for acquiring the engine speed of the vehicle; and determination means for determining whether the engine speed acquired by the means is greater than or equal to a threshold value. When it is determined that the means is not equal to or greater than the threshold, the rotor position estimated by the first estimation means is based on the rotor position estimated by the second estimation means when the determination means is determined to be equal to or greater than the threshold, The brushless motor is configured to be driven.

  An electric power steering apparatus according to a fourth aspect of the present invention is a torque sensor that detects a steering torque applied to a steering member of a vehicle, a single-phase or multiple-phase brushless motor for assisting steering, and a voltage that detects a phase voltage of the brushless motor. Detecting means; current detecting means for detecting a phase current of the brushless motor; and a high frequency voltage (or high frequency current) is injected into the brushless motor, and the rotor position of the brushless motor is based on the response current (or response voltage). First estimation means for estimating the rotor position, and second estimation means for estimating the rotor position based on the phase voltage and phase current detected by the voltage detection means and the current detection means, and the first estimation means or the second estimation means. Based on the rotor position estimated by the estimating means, the brushless motor is supplied such that a current corresponding to the steering torque detected by the torque sensor flows. In the electric power steering apparatus for driving the motor, the means includes: a means for detecting the steering angle of the steering member; and a determination means for determining whether the steering angle detected by the means is equal to or greater than a threshold value. Is determined to be not greater than or equal to the threshold value, the rotor position estimated by the first estimation means, and when the determination means is determined to be greater than or equal to the threshold value, based on the rotor position estimated by the second estimation means, The brushless motor is configured to be driven.

  An electric power steering apparatus according to a fifth aspect of the present invention is a torque sensor that detects a steering torque applied to a steering member of a vehicle, a single-phase or multiple-phase brushless motor for assisting steering, and a voltage that detects a phase voltage of the brushless motor. Detection means; current detection means for detecting a phase current of the brushless motor; and a high frequency voltage (or high frequency current) is injected into the brushless motor, and based on the response current (or response voltage), or the voltage detection means and Estimation means for estimating the rotor position of the brushless motor based on the phase voltage and phase current detected by the current detection means, and according to the steering torque detected by the torque sensor based on the rotor position estimated by the estimation means. In the electric power steering apparatus for driving the brushless motor so as to flow a current, Means for detecting the rudder angle of the rudder member, computing means for computing the rotor position based on the rudder angle detected by the means, the rotor position estimated by the estimating means, and the rotor position computed by the computing means Means for calculating the difference, and means for determining whether or not the difference calculated by the means is greater than or equal to a predetermined value. When the means is determined to be greater than or equal to the predetermined value, the estimation means is abnormal. It is determined that the brushless motor is driven based on the rotor position calculated by the calculation means.

  According to the electric power steering apparatus of the first invention, the first estimating means estimates the rotor position based on the response current (or response voltage) of the high-frequency voltage (or high-frequency current) injected into the brushless motor, and the second The estimation means estimates the rotor position based on the detected phase voltage and phase current. It is determined whether or not the steering torque detected by the torque sensor is equal to or greater than a threshold value. When it is determined that the steering torque is not equal to or greater than the threshold value, the rotor position estimated by the first estimation means is determined to be equal to or greater than the threshold value. Since the brushless motor is driven based on the rotor position estimated by the second estimating means, it is possible to realize an electric power steering apparatus that can select an optimal rotor position estimation algorithm for a steering-assisting brushless motor.

  According to the electric power steering apparatus of the second invention, the first estimating means estimates the rotor position based on the response current (or response voltage) of the high-frequency voltage (or high-frequency current) injected into the brushless motor, and the second The estimation means estimates the rotor position based on the detected phase voltage and phase current. It is determined whether or not the speed acquired by the vehicle speed acquisition means is equal to or greater than a threshold. When it is determined that the speed is not equal to or greater than the threshold, the rotor position estimated by the first estimation means is determined to be equal to or greater than the threshold. Since the brushless motor is driven based on the rotor position estimated by the second estimating means, it is possible to realize an electric power steering apparatus that can select an optimal rotor position estimation algorithm for a steering-assisting brushless motor.

  According to the electric power steering apparatus of the third invention, the first estimating means estimates the rotor position based on the response current (or response voltage) of the high-frequency voltage (or high-frequency current) injected into the brushless motor, and the second The estimation means estimates the rotor position based on the detected phase voltage and phase current. It is determined whether or not the acquired engine speed is equal to or higher than a threshold value. When it is determined that the position is equal to or greater than the threshold value, the brushless motor is driven based on the rotor position estimated by the second estimating means based on the detected phase voltage and phase current. An electric power steering apparatus capable of selecting a position estimation algorithm can be realized.

  According to the electric power steering apparatus of the fourth invention, the first estimating means estimates the rotor position based on the response current (or response voltage) of the high-frequency voltage (or high-frequency current) injected into the brushless motor, and the second The estimation means estimates the rotor position based on the detected phase voltage and phase current. It is determined whether or not the detected steering angle is greater than or equal to a threshold value, and when it is determined that the detected steering angle is not greater than or equal to the threshold value, the rotor position estimated by the first estimation means based on the response of the high frequency voltage (or high frequency current) injected into the brushless motor When the brushless motor is driven based on the rotor position estimated by the second estimating means based on the detected phase voltage and phase current when it is determined that the value is equal to or greater than the threshold value, the optimal rotor position of the brushless motor for steering assistance is determined. An electric power steering apparatus capable of selecting an estimation algorithm can be realized.

  According to the electric power steering apparatus of the fifth aspect of the invention, the rotor position is calculated based on the detected steering angle of the steering member, the difference between the estimated rotor position and the calculated rotor position is calculated, and the calculated difference is predetermined. If it is determined whether or not the value is equal to or greater than the predetermined value, and it is determined that the value is equal to or greater than the predetermined value, it is determined that the rotor position estimating means is abnormal, and the brushless motor is driven based on the calculated rotor position. Even when the rotor position estimation algorithm of the auxiliary brushless motor is in trouble, it is possible to realize an electric power steering device that does not cause unstable behavior of the motor, disappearance of steering auxiliary force, and lock of the motor.

Hereinafter, the present invention will be described with reference to the drawings showing embodiments thereof.
(Embodiment 1)
FIG. 1 is a block diagram showing the main configuration of the first embodiment of the electric power steering apparatus according to the present invention. In this electric power steering apparatus, a torque detection signal detected and output by a torque sensor 12 that detects torque applied to a handle (steering member (not shown)) is output to a microcomputer (hereinafter referred to as a microcomputer) via an interface circuit 11. And a speed signal detected and output by the vehicle speed sensor 20 that detects the speed of the vehicle is provided to the microcomputer 19 via the interface circuit 21.

Further, the steering angle signal detected and output by the steering angle sensor 22 for detecting the steering angle of the steering wheel is given to the microcomputer 19 via the interface circuit 23, and detected by the engine speed sensor 25 for detecting the engine speed of the vehicle. The output engine speed signal is supplied to the microcomputer 19 via the interface circuit 26.
The rudder angle sensor 22 is provided as necessary, and the engine speed signal is supplied to the microcomputer 19 as necessary.

A relay control signal output from the microcomputer 19 is input to the relay drive circuit 15, and the relay drive circuit 15 turns the fail-safe relay contact 15a on or off according to the relay control signal.
The microcomputer 19 refers to a torque / current table 18a in the memory 18 based on a torque detection signal, a speed signal, and a motor current signal, which will be described later, thereby outputting an output level that is a current value to be supplied to the brushless motor 24 for assisting steering. Create a command value. The PWM control unit 16 in the microcomputer 19 performs a PWM calculation based on the generated output level command value and a rotor position to be described later, generates a PWM control signal, and supplies it to the motor drive circuit 13.

The motor drive circuit 13 is applied with the power supply voltage of the in-vehicle battery P through the fail-safe relay contact 15a, generates a three-phase sine wave voltage based on the given PWM control signal, and rotates the brushless motor 24.
Each phase current flowing through the brushless motor 24 is detected by the motor current detection circuit 17 and given to the microcomputer 19, and the terminal voltage of each phase of the brushless motor 24 is detected by the motor voltage detection circuit 14 and given to the microcomputer 19. .
The microcomputer 19 estimates the rotor position of the brushless motor 24 based on the given phase current and voltage of the brushless motor 24, and gives the estimated rotor position to the PWM control unit 16.

  FIG. 2 is a block diagram illustrating a configuration example of the brushless motor 24, the motor drive circuit 13, the motor voltage detection circuit 14, and the motor current detection circuit 17. The brushless motor 24 includes a stator 24a in which one terminal of each of the coils A, B, and C is star-connected, and a rotor 24b that is rotated by a rotating magnetic field generated by the coils A, B, and C.

  The motor drive circuit 13 includes a switching circuit 8. The switching circuit 8 includes transistors Q1 and Q2 connected in series between a positive terminal and a ground terminal and diodes D1 and D2 connected in series in the opposite direction in parallel. The transistors Q3 and Q4 connected in series and the diodes D3 and D4 connected in series in the reverse direction are connected in parallel. The transistors Q5 and Q6 connected in series and the diode D5 connected in series in the reverse direction are connected. D6 is connected in parallel.

  The other connection terminal U of the star-connected coil A is connected to the common connection node of the transistors Q1, Q2 and the common connection node of the diodes D1, D2, and the common connection node of the transistors Q3, Q4 and the diode D3, The other terminal V of the star-connected coil B is connected to the common connection node of D4, and the star connection is made to the common connection node of the transistors Q5 and Q6 and the common connection node of the diodes D5 and D6. The other terminal W of the coil C is connected.

  The motor drive circuit 13 includes a gate control circuit 9, and the gate control circuit 9 is supplied with a PWM control signal for each phase of the three-phase sine wave voltage from the microcomputer 19, and in accordance with each supplied PWM control signal, a transistor Each gate of Q1-Q6 is turned on / off. At that time, for example, terminal pairs U-V (coils A, B), U-W (coils A, C), V-W (coils B, C), V-U (coils B, A), W-U As in (coils C, A), W-V (coils C, B), and U-V (coils A, B), the path of the current flowing through the stator 24a is switched to generate a rotating magnetic field.

The rotor 24b includes a permanent magnet, and rotates by receiving a rotational force from the rotating magnetic field. The gate control circuit 9 also controls increase / decrease of the rotational torque of the brushless motor 24 by PWM control of on / off of the transistors Q1 to Q6.
The diodes D1 to D6 are for absorbing noise generated by turning on / off the transistors Q1 to Q6.
The motor current detection circuit 17 detects each phase current flowing through the terminals U, V, and W of the brushless motor 24 and applies it to the microcomputer 19. The motor voltage detection circuit 14 detects the terminals U, V, and W of the brushless motor 24. Each phase voltage is detected and applied to the microcomputer 19.

Below, the operation | movement which estimates the rotor position of a brushless motor of the electric power steering apparatus of such a structure is demonstrated, referring the flowchart of FIGS. 3-5 which shows it.
When estimating the rotor position of the brushless motor, the microcomputer 19 first reads the steering torque (S2), and determines whether the read steering torque is equal to or greater than a predetermined torque (S4).

If the read steering torque is equal to or greater than the predetermined torque (S4; YES), the microcomputer 19 estimates the rotor position using the rotor position estimation algorithm B (S6) and returns. If the read steering torque is not equal to or greater than the predetermined torque (S4; NO), the rotor position is estimated using the rotor position estimation algorithm A (S8), and the process returns.
In the electric power steering apparatus, torque fluctuation and efficiency are regarded as important. Therefore, in the low torque range where torque fluctuation needs to be suppressed, the response current is small, and the high frequency voltage (current) injection method that can be executed even when the rotation is stopped is used in the high torque range where high efficiency is required. Select an observer method that can suppress the injected energy.

  When the microcomputer 19 estimates the rotor position using the rotor position estimation algorithm B (S6), first, each phase current of the brushless motor 24 detected by the motor current detection circuit 17 and the motor voltage detection circuit 14 detect it. The terminal voltage of each phase of the brushless motor 24 is read (S10). Next, based on the read phase currents of the brushless motor 24 and the terminal voltages of the respective phases, the state or disturbance observer (observer) estimates the N pole position of the rotor 24b (S12) and returns.

The microcomputer 19 can also estimate the rotor position using another rotor position estimation algorithm B (S6).
In another rotor position estimation algorithm B, as shown in FIG. 4B, the microcomputer 19 first detects each phase current of the brushless motor 24 detected by the motor current detection circuit 17 and the motor voltage detection circuit 14. The terminal voltage of each phase of the brushless motor 24 is read (S14). Next, from the difference between the read current of each phase of the brushless motor 24 and the current of the next sample calculated from the terminal voltage of each phase and the current of each phase of the brushless motor 24 detected by the motor current detection circuit 17, the rotor 24 b The N pole position is estimated (S16) and the process returns.

  When estimating the rotor position using the rotor position estimation algorithm A (S8), the microcomputer 19 first injects a high frequency voltage superimposed on the voltage of the brushless motor 24 (S18), and the response current of the injected high frequency voltage. Is measured by the motor current detection circuit 17 (S20). Next, the N pole position of the rotor 24b is estimated from the measured response current amplitude change due to the magnetic flux change of the permanent magnet of the rotor 24b (S22), and the process returns.

The microcomputer 19 can also estimate the rotor position using another rotor position estimation algorithm A (S8).
In the other rotor position estimation algorithm A, as shown in FIG. 5B, the microcomputer 19 first injects a high frequency current superimposed on the voltage of the brushless motor 24 (S24), and the response voltage of the injected high frequency current. Is measured by the motor voltage detection circuit 14 (S26). Next, the N pole position of the rotor 24b is estimated from the change in the amplitude of the measured response voltage due to the magnetic flux change of the permanent magnet of the rotor 24b (S28), and the process returns.

In the embodiment described above, the steering torque is read (S2). If the steering torque is equal to or greater than the predetermined torque (S4; YES), the rotor position estimation algorithm B is used (S6). (S4; NO), the rotor position estimation algorithm A is used (S8), but it is also possible to use detection values of other operation states.
For example, if the vehicle speed is read and the vehicle speed is equal to or higher than a predetermined speed, the rotor position estimation algorithm B can be used, and if not higher than the predetermined speed, the rotor position estimation algorithm A can be used.

It is also possible to read the engine speed of the vehicle and use the rotor position estimation algorithm B if the engine speed is equal to or higher than the predetermined speed, and use the rotor position estimation algorithm A if it is not higher than the predetermined speed. It is.
It is also possible to read the steering angle of the steering wheel and use the rotor position estimation algorithm B if the steering angle of the steering wheel is equal to or greater than a predetermined angle, and use the rotor position estimation algorithm A if the steering angle is not greater than the predetermined angle. .

(Embodiment 2)
FIG. 6 is a flowchart showing the operation of the second embodiment of the electric power steering apparatus according to the present invention. The main configuration and other operations of the electric power steering apparatus are the same as the main configuration and operation described in the first embodiment, and thus description thereof is omitted.
When executing the failure determination of the rotor position estimation operation, the microcomputer 19 first obtains the rotor position estimated by the rotor position estimation operation shown in the flowcharts of FIGS. 4 and 5 (S30), and then the steering torque and the steering angle. Is read (S32).

  Next, the microcomputer 19 calculates the rotor position of the brushless motor 24 based on the read steering angle, steering torque (S32), and the gear ratio of the reduction mechanism (not shown) of the brushless motor 24 (S34). Next, a deviation between the acquired rotor position estimated value (S30) and the calculated rotor position calculated value (S34) is calculated (S36), and it is determined whether or not the absolute value of the calculated deviation is greater than or equal to a threshold value (S36). S38).

  If the calculated absolute value of the deviation is not greater than or equal to the threshold value (S38; NO), the microcomputer 19 returns to the normal operation with the rotor position estimation operation being normal. If the calculated absolute value of the deviation is equal to or greater than the threshold value (S38; YES), it is determined that the rotor position estimation operation has failed (S40), and the brushless motor 24 is calculated using the calculated rotor position calculation value (S34). (S42) and return.

It is a block diagram which shows the principal part structure of embodiment of the electric power steering apparatus which concerns on this invention. It is a block diagram which shows the structural example of the brushless motor shown in FIG. 1, a motor drive circuit, a motor voltage detection circuit, and a motor current detection circuit. It is a flowchart which shows the operation | movement which estimates the rotor position of a brushless motor of the electric power steering apparatus which concerns on this invention. It is a flowchart which shows the operation | movement which estimates the rotor position of a brushless motor of the electric power steering apparatus which concerns on this invention. It is a flowchart which shows the operation | movement which estimates the rotor position of a brushless motor of the electric power steering apparatus which concerns on this invention. It is a flowchart which shows the operation | movement which determines the failure of rotor position estimation operation | movement of the electric power steering apparatus which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 9 Gate control circuit, 12 Torque sensor, 13 Motor drive circuit, 14 Motor voltage detection circuit, 16 PWM control part, 17 Motor current detection circuit, 18a Torque / current table, 19 Microcomputer (microcomputer), 20 Vehicle speed sensor, 22 Rudder Angle sensor, 24 brushless motor, 24a stator, 24b rotor, 25 engine speed sensor, A, B, C coil, Q1-Q6 transistor

Claims (5)

A torque sensor for detecting a steering torque applied to a steering member of the vehicle, a single-phase or multiple-phase brushless motor for assisting steering, a voltage detection means for detecting a phase voltage of the brushless motor, and a phase current of the brushless motor. Current detecting means for detecting; first estimating means for injecting a high frequency voltage (or high frequency current) into the brushless motor; and estimating a rotor position of the brushless motor based on the response current (or response voltage); and the voltage Second estimation means for estimating the rotor position based on the phase voltage and phase current detected by the detection means and the current detection means, and based on the rotor position estimated by the first estimation means or the second estimation means, In the electric power steering apparatus that drives the brushless motor so that a current corresponding to the steering torque detected by the torque sensor flows. Te,
A determination means for determining whether or not the steering torque detected by the torque sensor is equal to or greater than a threshold value. When the determination means determines that the steering torque is not equal to or greater than the threshold value, the rotor position estimated by the first estimation means is An electric power steering apparatus configured to drive the brushless motor based on the rotor position estimated by the second estimation unit when the determination unit determines that the value is greater than or equal to a threshold value. A torque sensor for detecting a steering torque applied to a steering member of the vehicle, a single-phase or multiple-phase brushless motor for assisting steering, a voltage detection means for detecting a phase voltage of the brushless motor, and a phase current of the brushless motor. Current detecting means for detecting; first estimating means for injecting a high frequency voltage (or high frequency current) into the brushless motor; and estimating a rotor position of the brushless motor based on the response current (or response voltage); and the voltage Based on the phase voltage and the phase current detected by the detection means and the current detection means, the second estimation means for estimating the rotor position, and the vehicle speed acquisition means for acquiring the speed of the vehicle, the first estimation means or the first 2 Based on the rotor position estimated by the estimating means, the electric power corresponding to the steering torque detected by the torque sensor and the speed acquired by the vehicle speed acquiring means. As flow in the electric power steering apparatus for driving the brushless motor,
A determination unit that determines whether or not the speed acquired by the vehicle speed acquisition unit is equal to or greater than a threshold value. When the determination unit determines that the speed is not equal to or greater than the threshold value, the rotor position estimated by the first estimation unit is An electric power steering apparatus configured to drive the brushless motor based on the rotor position estimated by the second estimation unit when the determination unit determines that the value is greater than or equal to a threshold value. A torque sensor for detecting a steering torque applied to a steering member of the vehicle, a single-phase or multiple-phase brushless motor for assisting steering, a voltage detection means for detecting a phase voltage of the brushless motor, and a phase current of the brushless motor. Current detecting means for detecting; first estimating means for injecting a high frequency voltage (or high frequency current) into the brushless motor; and estimating a rotor position of the brushless motor based on the response current (or response voltage); and the voltage Second estimation means for estimating the rotor position based on the phase voltage and phase current detected by the detection means and the current detection means, and based on the rotor position estimated by the first estimation means or the second estimation means, In the electric power steering apparatus that drives the brushless motor so that a current corresponding to the steering torque detected by the torque sensor flows. Te,
When it is determined that the means for acquiring the engine speed of the vehicle and the determination means for determining whether the engine speed acquired by the means is greater than or equal to a threshold, the determination means is not greater than or equal to the threshold. The brushless motor is configured to be driven based on the rotor position estimated by the second estimation unit when the determination unit determines that the determination unit is greater than or equal to a threshold at the rotor position estimated by the first estimation unit. An electric power steering device characterized by that. A torque sensor for detecting a steering torque applied to a steering member of the vehicle, a single-phase or multiple-phase brushless motor for assisting steering, a voltage detection means for detecting a phase voltage of the brushless motor, and a phase current of the brushless motor. Current detecting means for detecting; first estimating means for injecting a high frequency voltage (or high frequency current) into the brushless motor; and estimating a rotor position of the brushless motor based on the response current (or response voltage); and the voltage Second estimation means for estimating the rotor position based on the phase voltage and phase current detected by the detection means and the current detection means, and based on the rotor position estimated by the first estimation means or the second estimation means, In the electric power steering apparatus that drives the brushless motor so that a current corresponding to the steering torque detected by the torque sensor flows. Te,
When the means for detecting the steering angle of the steering member and the determination means for determining whether or not the steering angle detected by the means is equal to or greater than a threshold, The brushless motor is configured to be driven based on the rotor position estimated by the second estimating means when the determining means determines that the rotor position estimated by the first estimating means is greater than or equal to a threshold value. An electric power steering device characterized by being. A torque sensor for detecting a steering torque applied to a steering member of the vehicle, a single-phase or multiple-phase brushless motor for assisting steering, a voltage detection means for detecting a phase voltage of the brushless motor, and a phase current of the brushless motor. Current detection means to detect, and a high-frequency voltage (or high-frequency current) injected into the brushless motor, and the phase voltage and phase current detected based on the response current (or response voltage) or detected by the voltage detection means and the current detection means Based on the rotor position of the brushless motor, and based on the rotor position estimated by the estimation means, the brushless motor is configured to flow a current corresponding to the steering torque detected by the torque sensor. In the electric power steering device to drive,
Means for detecting the steering angle of the steering member, calculation means for calculating the rotor position based on the steering angle detected by the means, rotor position estimated by the estimation means, and rotor position calculated by the calculation means And a means for determining whether or not the difference calculated by the means is greater than or equal to a predetermined value. When the means is determined to be greater than or equal to a predetermined value, the estimation means is abnormal. The electric power steering apparatus is configured to drive the brushless motor based on the rotor position calculated by the calculation means.

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