JP2510186B2 - Control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an idle speed control of an internal combustion engine, which controls the intake air amount to control the idle speed to a target speed during idling, for example. More specifically, the present invention relates to an idle speed control device for an internal combustion engine that can control the idle speed with good response.

[Conventional Technology] Conventionally, this type of idle speed control device detects the rotational speed of the internal combustion engine and feedback-controls the intake air amount, and so-called PID (proportional, integral, differential) is used for the control. The control was widely applied. However, in such control, since the intake air amount is controlled only after the rotational speed changes, the responsiveness, particularly the transient responsiveness, is not sufficient, and a load change (for example, on / off of the air conditioner) occurs in the internal combustion engine. However, there was a problem that it took a considerable time for the idle speed to stabilize.

Therefore, in recent years, a dynamic model of a system for controlling the idle speed of an internal combustion engine is considered, the internal state is estimated, the idle speed is feedback-controlled, and the response of the control is dramatically improved. Proposals have been made (for example, Japanese Patent Laid-Open No. 59-7752, Japanese Patent Laid-Open No. 59-43942, and Japanese Patent Laid-Open No. 59-145339, "Method for controlling idle speed of internal combustion engine").

[Problems to be Solved by the Invention] Such control of the idle speed is to perform a control by constructing a precise control model based on so-called modern control theory, but there are the following problems and There has been a strong demand for improvement.

(1) In modern control, the internal state of the system that controls the idle speed is represented by a state variable amount, and the necessary control input (here, the control amount of intake air) is determined by knowing this, but such state change The quantity is a state observer (observer)
Have to build and ask. Although various designing methods for this observer have been proposed, there has been a problem that enormous simulations must be performed to select appropriate parameters and the like, which requires a great deal of time and labor.

(2) Further, since the observer is constructed corresponding to the dynamic model of the controlled object, the observer can only be operated with certainty depending on the accuracy when constructing the dynamic model of the system that controls the idle speed. The variable quantity cannot be observed. Therefore, in order to increase the accuracy of observation of the state variable amount by the observer, the controlled object must be modeled with high accuracy, the model becomes complicated, and the load of calculation etc. in the actual control becomes large. The problem was that it could not be used for control of.

The present invention has been made for the purpose of solving such a problem, and provides a control device that knows the state variable amount without using an observer and controls an actuator for idle speed control of an internal combustion engine with good responsiveness. is there.

Structure of the Invention [Means for Solving Problems] In order to achieve the above object, the present invention has the following structures as means for solving the problems. That is, as illustrated in FIG. 1, a detection unit that detects an output value related to the operating state of the controlled object, an actuator that adjusts the operating state of the controlled object, and a control amount of the actuator are determined. A control means for controlling the actuator according to the control amount, the control means comprising a storage means for storing the output value detected by the detection means and the determined control amount; and a predetermined feedback gain and state. And a control amount calculation unit that newly calculates the control amount of this time based on a variable, the feedback gain depends on a dynamic model that approximates the operating state of the control target, and the state variable is the storage unit. The configuration of the control device is characterized in that it is configured as a vector value that directly uses the past output value and the past control amount stored in That's it.

Here, the control target is idle air amount control means for controlling the intake air amount during idling of the internal combustion engine, and the detection means is rotational speed detection means for detecting the rotational speed during idling of the internal combustion engine. It can be a device.

Further, the dynamic model has a dead time p (p = 0,1,2,
…) With an order [n, m] (n = 1,2,3, ..., m = 1,2,3, ...)
May be approximated by the autoregressive moving average model and further constructed by considering the disturbance.

Here, an autoregressive moving average model of order [n, m] having a dead time P (≧ 1) is Ne (k) = a ₁ · Ne (k−1) + a ₂ · Ne (k−2). _{+ ...... + a n · Ne (} k-n) + b 1 · u (k-1-P) + b 2 · u (k-2-P) + ...... + b m · u (k-m-P) ...... When the idle speed Ne is determined in the form of (1), the idle speed control system is approximated. Further, in the present invention, the disturbance d is taken into consideration, Ne (k) = a ₁ · Ne. _{(k-1) + a 2} · Ne (k-2) + ...... + a n · Ne (k-n) + b 1 · u (k-1-P) + b 2 · u (k-2-P) + ... A dynamic model of the system for controlling the idle speed is constructed as + b _m · u (k−m−P) + d (k + 1) (2).

As a result, When using the display, Next to As Can be used.

Further, an autoregressive moving average model considering the disturbance d when the dead time P = 0 is Ne (k) = a ₁ · Ne (k−1) + ... + a _n · Ne (k−m + 1) + b ₁ · u (k-1) + ... + b m · u (k-m + 1) + d (k-1) construction of a dynamic model of the system for controlling the idle speed as ......... (2 ') is made.

As a result, When using the display, Next to As Can be used.

When the dead time P ≧ 1, Ne (K), Ne (k−1) ... Ne (K−n + 1), u (k−) used in the control up to now.
1), u (k−2), ... u (k−m−P + 1) are stored and output, and the dead time P =
When set to 0, Ne used in control up to now
(K), Ne (k-1), ... Ne (k-n + 1), u (k-
1), u (k−2), ... U (k−m + 1) are stored and output.

[Action]

The output value related to the operating state of the controlled object is detected by the detection means, and the control amount of the actuator for adjusting the operating state of the controlled object is determined by the control means to control the actuator. The control means stores the output value detected by the detection means and the determined control amount in the storage means, and newly determines the control amount of this time by the control amount calculation means based on a predetermined feedback gain and a state variable. Along with the calculation, the feedback gain is made to depend on a dynamic model that approximates the operating state of the controlled object, and the state variable is configured as a vector value that directly uses the past output value and the past control amount stored in the storage means. The state observer is no longer needed.

Example In order to further clarify the configuration of the present invention described above,
Next, an idle speed control device as a preferred embodiment of the present invention will be described. FIG. 2 is a schematic configuration diagram showing the engine 10 and its peripheral devices in which the idle speed control described below is performed. As shown in the figure, in the present embodiment, the control of the ignition timing of the engine 10, the fuel injection amount, and the idle speed are each performed by the electronic control unit 20, but the control of the idle speed will be mainly described here.

The engine 10 is mounted on a vehicle and is of a 4-cylinder 4-cycle spark point type, as shown in FIG. 2, and its intake air is taken from the upstream side of an air cleaner 21, an air flow meter 22, an intake pipe 23, Fuel is sucked into each cylinder via a surge tank 24 and an intake branch pipe 25, while fuel is pressure-fed from a fuel tank (not shown) to provide a fuel injection valve 26 provided in the intake branch pipe 25.
It is configured to be injected and supplied from a, 26b, 26c, and 26d. Further, the engine 10 is supplied with a high voltage electric signal supplied from the ignition circuit 27 by the spark plugs 28a, 28b, 28c, 28 of each cylinder.
a distributor 29 for distributing to the d, a revolution sensor 30 provided in the distributor 29 for detecting the revolution speed Ne of the engine 10, a throttle sensor 32 for detecting the opening TH of the throttle valve 31, and a cooling water temperature Thw of the engine 10. A warm-up sensor 33 for detecting and an intake air temperature sensor 34 for detecting the intake air temperature Tam are also provided. The rotation speed sensor 30 is provided so as to face a ring gear that rotates in synchronization with the crank shaft of the engine 10. One rotation of the engine 10 is proportional to the rotation speed of the engine 10, that is, 24 pulse signals at 720 ° C. Is output. The throttle sensor 32 is a throttle valve
An on / off signal from an idle switch that detects that the throttle valve 31 is almost fully opened is output together with an analog signal corresponding to the opening TH of 31.

On the other hand, the intake system of the engine 10 has a throttle valve 31
Intake air amount when the engine 10 is idle
A bypass passage 40 for controlling the AR is provided. The bypass passage 40 is composed of air conduits 42 and 43 and an air control valve (hereinafter referred to as ISC valve) 44. This ISC valve 4
Reference numeral 4 is basically a proportional solenoid (linear solenoid) control valve, and the air passage area between the air conduits 42 and 43 can be changed by the position of the plunger 46 that is movably set in the housing 45. To control. ISC valve 44
Normally, the plunger 46 is set by the compression coil spring 47 to a state where the air passage area becomes zero, but by supplying an exciting current to the exciting coil 48,
46 is configured to be driven to open the air passage.
That is, the bypass air flow rate is controlled by continuously changing and controlling the exciting current to the exciting coil 48. In this case, the exciting current for the exciting coil 48 is
It is controlled by performing so-called pulse width modulation PWM that controls the duty ratio of the pulse width applied to the exciting coil 48.

The ISC valve 44 is driven and controlled by the electronic control unit 20 similarly to the fuel injection valves 26a to 26d and the ignition circuit 27, and in addition to the above-mentioned ones, a diaphragm control type valve, a step motor control valve, etc. Used as appropriate.

The electronic control unit 20 includes a well-known central processing unit (CPU) 51 and read-only memory (R).
OM) 52, random access memory (RAM) 53, backup RAM 54, etc. as an arithmetic logic operation circuit, and an input port for inputting from each sensor described above.
Output port that outputs control signals to 56 and each actuator
58 and the like are connected to each other via a bus 59. The electronic control unit 20 inputs the intake air amount AR, the intake air temperature Tam, the throttle opening TH, the cooling water temperature Thw, the rotation speed Ne, etc. via the input port 56, and based on these inputs, the fuel injection amount τ, the ignition timing. Ig, ISC valve opening θ, etc. are calculated, and fuel injection valves 26a to 26d, ignition circuit 31, ISC valve 4 are output via the output port 58.
Output a control signal to each of the four. Of these controls,
The idle speed control will be described below.

The electronic control unit 20 is designed in advance by the following method in order to perform idle speed control.

(1) Modeling of controlled object An autoregressive moving average model of order [2,2] is used with n = m = 2 as a system for controlling the idle speed, and a delay P due to sampling time (dead time) is added to this. = 1, from the above-mentioned formula (1), Ne (k) = a ₁ · Ne (K-1) + a ₂ · Ne (k-2) + b ₁ · u (k-2) + b ₂ · u (K-3) ... (5) is obtained. Further models of the systems taking into account the disturbance d for controlling the idle speed to _{this, Ne (k) = a 1} · Ne (K-1) + a 2 · Ne (k-2) + b 1 · u (k- 2) + b ₂ · u (k-3) + d (k-1)
… Approximate as (6). Here, u indicates the control amount of the ISC valve 44, and corresponds to the duty ratio of the pulse signal applied to the exciting coil 48 in this embodiment. Also,
K is a variable indicating the number of times of control from the start of the first sampling.

For the model thus approximated, the transfer function G of the system for controlling the idle speed is obtained by using the step response, and the constants a ₁ , a ₂ , b ₁ , b ₂ of the above model are experimentally determined from this. It's easy. By defining the constants a ₁ , a ₂ , b ₁ , and b ₂ , the model of the system that controls the idle speed is determined.

Equation (6) Rewriting using, from equation (3), Get. Therefore, without taking any measures Is Becomes

(3) Design of additional integral type regulator When the additional integral type regulator is designed with respect to the above equations (7) and (8) in consideration of the integral term for absorbing the error, as shown in FIG. State variable quantity to enlarge _{[Z (k) X 1 (k} ) X 2 (k) X 3 (k) X 4 (k) ] ^T = [Z (k) Ne (k) Ne (k-1) u (k-1) u (k-2)] ^T and As a result, the control amount u (k) of the ISCV valve 44 can be obtained. Here, Z (k) is a cumulative value of deviation ΔZ (K) = Ne (*) − Ne (k) between the target speed Ne (*) at the time of idling and the actual speed Ne (k). And Z (k + 1) = Z (k) + ΔZ (k) ... (10) Further, in FIG. 3, the controlled variable u (K-
In order to derive 1) from u (k), it was displayed using the Z ⁻¹ conversion amount. This is because the past control amount u (k−1) was stored in RAM 53 and read at the time of the next control. Equivalent to use. FIG. 4 is a block diagram rewritten based on the expressions (9) and (10). In the figure, P1 corresponds to the state variable amount output unit, P2 corresponds to the accumulation unit, and P3 corresponds to the control amount calculation unit.

(4) Optimal feedback gain Determining the optimal feedback gain Can be determined, for example, by the following method.

(Optimal servo system) Optimal feedback gain Is the evaluation function, Is determined to be a minimum. Here, the evaluation function J is the minimum deviation of the idle speed Ne (k) as the control output from the target speed Ne (*) while limiting the movement of the control amount u (k) of the ISC valve 44. The weighting of the constraint on the control amount u (k) can be changed by the values of the weighting parameters Q and R.
Therefore, the simulation is repeated until the optimum control characteristics are obtained by changing the values of the weighting parameters Q and R, Should be set.

And above Depends on the model constants a ₁ , a ₂ , b ₁ , b ₂ . Therefore, when trying to guarantee the stability (robustness) of the system against fluctuations (parameter fluctuations) of the system that controls the actual idle speed, fluctuations of the model constants a ₁ , a ₂ , b ₁ , b ₂ are expected. Optimal feedback gain at Need to be designed. Therefore, the simulation is performed by taking into consideration the actual fluctuations of the model constants a ₁ , a ₂ , b ₁ , and b ₂ , and the optimum feedback gain that satisfies the stability is obtained. Determine. As the fluctuation factors, it is possible to consider changes due to time, such as fatigue of the ISCV valve 44 and clogging of the bypass passage, and load fluctuations.

As above, the modeling of the controlled object, the method of displaying the state variable amount, the design of the additional integral type regulator, and the determination of the optimum feedback gain have been described, but these are determined and obtained in advance, and as a result thereof inside the electronic control unit 20. That is, the actual control is performed using only the expressions (9) and (10).

Therefore, next, the process actually performed by the electronic control unit 20 will be described with reference to the flowchart of FIG.

When the power is turned on, the electronic control unit 20 executes the ISCV control routine shown in FIG. 5 together with other control routines such as fuel injection control. First, a so-called initialization process is performed immediately after starting (step 100). Here, the initialization process means, for example, setting the variable K indicating the number of samplings to zero and setting the ISC
The initial values u (-1) and u (-2) of the control amount of the valve 44 are set to constants ui1 and ui2, respectively, and the accumulated Z of the deviation between the target speed Ne (*) and the actual idle speed Ne (k) is set. (0) is a constant Zi
The process of setting each in a predetermined area of the RAM 53.

Then, the actual idle speed Ne (k) is read from the speed sensor 30 via the input port 56 (step 11
0), the control amount u (k) of the ISC valve 44 is set to the optimum feedback gain. And the amount of state variables Then, the processing required from and is performed (step 120). In the first processing of step 120 after the initialization processing, Ne (k) = Ne (k-1) is set. The control amount (duty ratio in this embodiment) thus obtained u
(K) is used to control the ISCV valve 44 via the output port 58 (step 130), and this control amount u (k) is stored in the RAM 53 in preparation for the next processing (as u (k-1)). Processing for storing / updating in a predetermined area is performed (step 14
0).

Next, the idle speed Ne from the target speed Ne (*)
The deviation ΔZ (k) of (k) is obtained (step 150), and a process of accumulating this is performed (step 160). After that, the value of the variable k is incremented by 1 (step 17
0), the process returns to step 110, and the processes of steps 110 to 170 described above are repeatedly executed.

The idle speed control device of the present embodiment configured as described above, the state variable amount representing the internal state of the system for controlling the idle speed of the engine 10 The past input / output Ne of the system that controls the idle speed
(K), Ne (k-1), u (k-1), u (k-2) and the cumulative value Z (k) of the deviation between the target speed and the actual speed.
This state variable quantity is constructed by using the raw value of For each value that makes up Since the control amount u (k) of the ISC valve 44 can be determined by adding the respective values multiplied by each other, the engine 10 can be extremely accurately and stably provided with a simple configuration that does not require an observer or the like. The idle speed can be controlled.

FIG. 6 and FIG. 7 show that the disturbance (here, the disturbance due to the turning on and off of the compressor of the air conditioner) that changes the idle speed Ne (k) by 375 [rpm] and 187 [rpm], respectively. 6 is a graph comparing the control of the idle rotation speed when added with the conventional PI control and the control in the present embodiment. In both figures, broken lines C and c represent changes in the control amount u (k) and idle speed Ne (k) of the ISC valve 44 by the conventional PI control, respectively, while solid lines G and g represent the present embodiment. Control amount u (k) of ISC valve 44 by control
And the idle speed Ne (k) are shown respectively. As is clear from the drawing, according to the idle speed control of the present embodiment, the response (rise, fall) which is extremely faster than that of the conventional PI control is realized, and the fluctuation of the idle speed is extremely small. I keep it to. Also,
It can be appreciated that an improvement of one digit or more has been realized by comparing the time taken for the idle speed Ne (k) of the engine 10 to stabilize. Therefore, according to the idle speed control device of the present embodiment, the idle speed Ne (k) can be stably controlled with high responsiveness, so that the idle speed can be set low, which contributes to the improvement of fuel consumption. it can.

And, in particular, in this embodiment, the state variable amount Is configured by using the past input / output and the cumulative value of the deviation between the target speed and the actual speed as it is, no observer is required, and therefore the model of the system for controlling the idle speed is extremely simple. It has the advantages that it can be configured, the design time can be shortened, and the specification change can be easily dealt with.

In the above embodiment, (4) optimum feedback gain Although the determination has been made by the optimum servo system, it can be determined by other methods. In order to simplify the description, an autoregressive moving average model of degree [1,1] will be used here, and the case of dead time P = 1 will be described.

In this case, the model of the system for controlling the idle speed is Ne (k) = a.Ne (k-1) + b.u (k-2) + d (k-1).
……… (6 ′), Is Therefore, the expanded state variable quantity becomes [Z (k), Ne (k), u (k-1)] ^T.

And by the above-mentioned optimal servo system, The result of obtaining is using model constants a and b, Is defined as Here, a · b · R · ² + (R−a ² · R + b ² · Q) · −a ·
The solution is b · Q = 0 (however,> 0).

Next, a case where a finite settling servo system, which is one of the other methods, is used will be described.

Here, when the equation (9) is applied to this example, Is expressed as, the third (3), (8 '),
From equations (9 ') and (10), the state equation of the entire ISC system is Becomes Here, when the characteristic polynomial of the equation (13) is calculated, Becomes A finite settling servo system can be constructed by determining the coefficient so that the equation (14) = Z ³ . That, F2 = a + 1, F1 = 1 / b (a 2 + a + 1), F0 = 1 / b ... (1
Optimal feedback gain that 2 ') should determine Becomes

Next, a case where eigenvalue designation which is another method is used will be described.

Let Z ^{P + 2} + α _{P + 1} Z ^{P + 1} + α _P Z ^P + ... + α Z + α ₀ be the target characteristic polynomial, compare the coefficient with the equation corresponding to equation (14), and obtain the optimum feedback gain. Ask for. Considering the case of this example, when the target characteristic polynomial is Z ³ + α ₂ Z ² + α ₁ Z + α ₀ (15), the coefficients of the equations (14) and (15) are compared. And this is the optimal feedback gain to be determined. Becomes

Although one embodiment of the present invention has been described above, the present invention is not limited to such an embodiment, and does not deviate from the gist of the present invention, for example, a system other than the delay P = 1 is used in system modeling. It goes without saying that it can be implemented in various modes within the scope.

EFFECTS OF THE INVENTION As described in detail above, according to the control device of the present invention, it is possible to realize, with a simple configuration, high responsiveness and stability that could not be realized by the conventional control device. It has an excellent effect. Further, since the structure is simplified and no observer is required, the number of manufacturing steps and costs can be reduced, the calculation time can be shortened, and the control characteristics can be further improved.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a basic configuration of the present invention, and FIG. 2 is a schematic configuration diagram showing an engine and its peripheral devices to which an idle speed control device according to an embodiment of the present invention is applied,
3 and 4 are block diagrams of a system for controlling the idle speed, FIG. 5 is a flowchart showing an ISCV control routine in the embodiment, and FIGS. 6 and 7 show control characteristics according to the embodiment. Graph shown in comparison with the conventional example,
Is. 10 …… Internal combustion engine 20 …… Electronic control unit 30 …… Rotational speed sensor 44 …… Air control valve (ISC valve) 51 …… CPU

Claims (3)

(57) [Claims] 1. A detection means for detecting an output value related to an operating state of a controlled object, an actuator for adjusting an operating state of the controlled object, a control amount of the actuator, and an actuator according to the control amount. And a storage means for storing the output value detected by the detection means and the determined control amount, and a control means for controlling the current value based on a predetermined feedback gain and a state variable. With the control amount calculation means for newly calculating the control amount, the feedback gain depends on a dynamic model that approximates the operating state of the controlled object, and the state variable is the past stored in the storage means. A control device configured as a vector value that directly uses an output value and a past control amount. 2. The control target is an idle air amount control means for controlling an intake air amount when the internal combustion engine is idle, and the detection means is a rotation speed detection means for detecting an idle speed of the internal combustion engine. The control device according to claim 1. 3. The dynamic model is characterized by a dead time p (p = 0,
1,2, ...) with an order [n, m] (n = 1,2,3, ..., m = 1,2,3,
The control device according to claim 1 or 2, wherein the control device is approximated by an autoregressive moving average model of () and is constructed in consideration of disturbance.