JPH04298668A - Feedback control device - Google Patents

Abstract

PURPOSE:To shorten processing time for computing a control quantity to improve responsiveness of control by controlling feedback for an engine. CONSTITUTION:For feedback controlling an engine control quantity according to deviation between a target value and an actually measured value so as to settle the result of combustion of an engine in the target value, it is constituted by providing a data conversion means G to convert figures of data used for computing a control quantity to be shorter as the deviation above-mentioned is smaller, at the prior stage of a control quantity computing means F to compute the feedback control quantity.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feedback control device that performs feedback control so that engine idle speed, air-fuel ratio, and other combustion results converge to target values.

0002

[Prior Art] Conventionally, when determining the amount of fuel injection, as shown in Japanese Patent Publication No. 58-45582, when controlling various types of engines, it has been necessary to The calculation frequency of the basic injection amount is increased, the correction injection amount for parameters with small fluctuations such as the water temperature correction amount is calculated less frequently, and the calculation speed of sequentially performing various control calculations is increased.
Techniques for increasing control responsiveness are known.

[0003] In other words, when the control amount is determined by calculations performed by a microcomputer, the shorter the calculation interval, the more precise control can be performed in response to the fluctuation amount. The control accuracy is ensured by giving priority to these calculations.

0004

[Problem to be Solved by the Invention] However, even if the frequency of calculation is changed as described above, the calculation time required to obtain one control amount is the same, and it is possible to further improve the control accuracy. When calculation processing of other control variables is added, there is a problem of insufficient calculation processing power or memory capacity.

[0005] Taking idle rotation control as an example of engine feedback control, the deviation between the target rotation speed and the actual engine rotation speed is a large value at the beginning of the feedback, but becomes a small value when the feedback is stable. , even at the maximum value, the deviation when this feedback is stable is ±
At 50 rpm, the required data accuracy (resolution) is 1r.
If it is pm, the binary code is ±32H (hexadecimal display)
, which can be sufficiently handled with an 8-bit data length (number of digits).

However, if a disturbance is applied at the beginning of the feedback, the deviation becomes a large value, and the 8-bit data length may overflow, and a longer data length (for example, 16 bits) is required. Furthermore, 8-bit data length is originally insufficient for data processing of the target rotational speed and actual engine rotational speed, and it is necessary to process with 16-bit data length. The result of subtraction for the deviation between the two is a 16-bit data length, and when calculating the feedback control amount based on this deviation, addition, subtraction, multiplication, and division operations are performed in the 16 digits, so the program length This significantly increases the number of calculations and lengthens the calculation time, which becomes an obstacle to improving control speed, that is, feedback responsiveness, and requires a large capacity memory in the control system.

Therefore, in view of the above-mentioned circumstances, the present invention focuses on the fact that in feedback control, when the control is stabilized, the deviation between the target value, which is the basis for calculation of the control amount, and the actual value becomes small, and the calculation of the feedback control amount is performed. It is an object of the present invention to provide a feedback control device that speeds up processing.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the feedback control device of the present invention, as shown in the basic configuration in FIG.
Combustion control means A for controlling combustion such as air-fuel ratio is provided, and combustion result detection means B detects actual combustion results such as idle rotation speed and air-fuel ratio associated with combustion of engine E adjusted by combustion control means A. . The actual value detected by the combustion result detection means B is set in advance by the target value setting means C.
Feedback control is performed to converge to the target value set by .

A deviation calculating means D calculates the deviation between the actual measured value from the combustion result detecting means B and the target value from the target value setting means C. The deviation calculated by this deviation calculation means D is input to the control amount calculation means F via the data conversion means G, which will be described later.
Then, a feedback control amount is calculated according to the deviation so that the actual measurement value matches the target value, and is outputted to the combustion control means A to feedback-control the combustion state of the engine E.

[0010]The data converting means G installed before the controlled variable calculating means F converts the number of data digits into a shorter number as the deviation between the target value and the actual measured value is smaller. This is what is output to F.

[0011]

[Function and Effect] In the feedback control device as described above, basically, the control amount calculation means calculates the feedback control amount according to the deviation between the two so that the actual measured value such as the idle rotation speed converges to the target value. , which adjusts the combustion state of the engine, and when the deviation becomes smaller as a result of feedback control by the control amount calculating means, the data converting means converts the number of data digits indicating the deviation to a shorter number. , the calculation processing speed of various calculations such as multiplication for determining the control amount in the control amount calculation means becomes faster, the calculation time is shortened, and there is a margin for calculation processing, and the control is improved by increasing the calculation frequency or adding various correction calculations, etc. Accuracy can be improved, and control responsiveness can also be improved.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. FIG. 3 is an overall configuration diagram of an engine equipped with a feedback control device according to an embodiment. This embodiment concerns an example in which the idle speed of the engine is feedback-controlled.

An intake port 4 and an exhaust port 5 are opened in communication with a combustion chamber 3 formed above the piston 2 of the engine body 1 so as to have a variable volume. It is opened and closed.

An intake passage 8 connected to the intake port 4
is equipped with an air flow sensor 11 and a throttle valve 12 that detect the amount of intake air from the upstream side, and a surge tank 1.
A downstream portion of the cylinder 3 is branched into each cylinder, and an injector 14 for injecting and supplying fuel is disposed there.

Further, a bypass air passage 15 is formed in the intake passage 8, which bypasses the throttle valve 12 and is connected to the intake passage 8 above and below the intake passage 8. A control valve 16 is provided to adjust the amount of air. Further, an ignition plug 17 is disposed facing the combustion chamber 3, and a discharge voltage is applied to the ignition plug 17 via an ignition coil 18 and a distributor 19 to adjust the ignition timing.

A control signal is outputted from the controller 20 to the control valve 16 of the bypass air passage 15, and during idle, idle rotation speed control is performed in which the idle rotation speed by this bypass air control is feedback-controlled to the target rotation speed. be exposed. Further, ignition timing control for the ignition coil 18 and fuel injection control for the injector 14 are similarly performed according to the operating state by control signals from the controller 20.

In order to detect the operating state, the controller 20 receives a rotation signal from the distributor 19 for detecting the engine rotation speed, an intake air amount signal from the air flow sensor 11, an engine water temperature signal from the water temperature sensor 22, and a signal from the throttle valve 12. Signals and the like from the idle switch 23, which operates in the fully closed state, are respectively input.

Furthermore, as shown in the block diagram of FIG. 2, the controller 20 adjusts the feedback control amount (correction amount) to a predetermined value by PID calculation based on the deviation e between the target idle speed No. and the detected idle speed Ne. A front-stage bit shift 26 and a rear-stage bit shift 27 are provided before and after a PID calculating section 25 that calculates the opening degree signal θ of the control valve 16 of the bypass air passage 15 based on the characteristics of The target idle rotation speed No. and the detected idle rotation speed Ne are input as 16-bit data, and the deviation e (16-bit data) is bit-shifted by the pre-stage bit shift 26 to reduce the number of data digits to 8-bit data and perform PID calculation. The control unit 25 calculates the control amount θ by performing calculations based on the 8-bit data, and the control amount θ (8-bit data) is bit-shifted by the subsequent bit shift 27 and the number of data digits is expanded to 16-bit data and output. It is something.

Note that the proportional term P in the calculation of the feedback control amount θ in the PID calculation section 25 is calculated using 8-bit data, but in the calculation of the integral term I and the differential term D, the data of the previous control cycle is used. Part 1 because it is necessary
Prepare 6-bit data.

The processing of the controller 20 will be explained with reference to the flowchart of FIG. This flowchart only shows the main parts of the bit shift and PID calculation. After the control starts, the target idle rotation speed No. and the detected idle rotation speed Ne are input in step S1, and the deviation e between the two is calculated in step S2. Set e in register e16 as a basic value for bit shifting (S3).

[0021] In step S4, it is determined whether the sign bit set in the most significant digit of the deviation e16 is 0 or not. If the sign bit is set to 0 and is a positive number,
In step S5, a number obtained by subtracting 1 from the number of consecutive 0's from the top of the deviation e16 is set in S. On the other hand, if the determination in step S4 is NO and the sign bit is set to 1, which is a negative number, then in step S6 the deviation e16
Set S to the number obtained by subtracting 1 from the number of consecutive 1's from the top.

Then, in step S7, the deviation e16 is shifted to the left by S bits based on the value of S, thereby creating data in which a significant digit immediately follows the sign bit. In step S8, the shifted deviation e16 is converted into 8-bit data by moving its upper 8-bit data to e8. Subsequently, in step S9, this 8-bit deviation e8
and P gain Kp set with 8 bits (proportional term constant)
The value of the proportional term P8 is determined by 8-bit operation.

Next, in steps S10 to S14, the integral term I is calculated. First, in step S10, the previous integral term I(
16 bits) to the left by S bits, and step S11
Then, the upper 8 bits of the shifted integral term I are transferred to I8 and converted into 8-bit data. Subsequently, in step S12, the I gain Ki set in 8 bits for the deviation e8 is added to the 8-bit integral term I8.
By adding and accumulating the products multiplied by (integral term constant), the current value of the integral term I8 is determined by 8-bit operation. After this,
In step S13, in order to convert the current integral term I8 to 16 bits, this integral term I8 is set to the upper 8 bits of the 16-bit integral term I, and the lower 8 bits are set to 0 (positive number) or 1 (negative number). After setting, in step S14
By rotating the bits to the right, it is converted into a 16-bit integral term I.

[0024] Also, in steps S15 to S18, the differential term D
Perform the calculation. First, in step S15, the previous deviation e'
(16 bits) to the left by S bits, step S1
In step 6, the upper 8 bits of the shifted deviation e' are transferred to e'8 and converted into 8-bit data. Subsequently, in step S17, this 8-bit deviation e′8
The differential term D8 is obtained by multiplying the difference between the deviation e8 and the deviation e8 by the D gain Kd (differential term constant) set in 8 bits.
Find the value of using 8-bit arithmetic. After this, step S18
In step S2, the previous value e' is updated with the current deviation e obtained in step S2.

In step S19, the feedback control amount θ8 is determined using the proportional term P8, the integral term I8, and the differential term D8 by 8-bit calculation. Then, in step S20, this feedback control amount θ8
In order to make 16 bits, this control amount θ8 is changed to 16 bits.
Set the upper 8 bits of the bit control amount θ, set 0 (positive number) or 1 (negative number) to the lower 8 bits, and then
By rotating the S bit to the right in step S21,
This is converted into a 6-bit feedback control amount θ. This feedback control amount θ is outputted to the control valve 16 in step S22 to perform feedback control to converge the idle rotation speed to the target rotation speed.

According to the above-described processing, the basic calculations of the feedback control amount, especially the multiplication, are performed using 8-bit calculations, thereby reducing the processing steps compared to the case where the entire calculation is performed using 16-bit data digits. The number of calculations can be significantly reduced, and the calculation time for determining the overall control amount can be shortened. That is, for example, when executing the flowchart shown in FIG. 4, when calculating the feedback control amount θ using 16 bits, the number of processing steps is 341 steps, whereas the number of processing steps is 8 bits. In the case of the present invention in which the shift is performed, the number of steps becomes 194, which is a reduction of 147 steps, and the processing time can be reduced by that amount. Note that the number of processing steps described above varies depending on the type of CPU, program architecture, and data content, but the above value indicates an approximate value for an average 8-bit CPU. Also, when calculating directly with 16 bits,
In order not to reduce calculation accuracy, a 24-bit result is required, and in other words, in 16-bit calculation, the number of processing steps increases because digit loss occurs when the deviation e is small.

[0027] In the above embodiment, the case of feedback control of the idle rotation speed was explained, but as this feedback control, an air-fuel ratio sensor is disposed in the exhaust passage of the engine, and the air-fuel ratio detected by this air-fuel ratio sensor is set to the target. It can also be applied to feedback control of the fuel supply amount so that it converges to the air-fuel ratio, and it can also be applied to other feedback controls where the deviation is small by correspondingly shortening the number of data digits. Applicable. In addition, although the above embodiment shows an example of shortening 16 bit data to 8 bit data, there are other cases where 32 bits are shortened to 16 bits or 8 bits to 4 bits depending on the size of deviation and resolution. The same is true for

[Brief explanation of drawings]

FIG. 1 is a basic configuration diagram for clearly showing the configuration of a feedback control device of the present invention.

[Figure 2] Block diagram of main parts of controller

FIG. 3 is a schematic configuration diagram of an engine equipped with a feedback control device according to an embodiment of the present invention.

[Figure 4] Flowchart diagram for explaining the processing of the controller

[Explanation of symbols]

E engine B Combustion result detection means C Target value setting means D Deviation calculation means F Controlled amount calculation means G Data conversion means 1 Engine body 20 Controller 25 PID calculation section 26 Pre-stage bit shift 27 Later bit shift

Claims (2)

[Claims] Claim 1: Feedback control that compares this target value with an actual combustion result value so that the combustion result of the engine converges to a preset target value, and performs feedback control of the engine control amount according to the deviation between the two. In the device,
A feedback control device characterized in that a data conversion means is provided upstream of the control amount calculation means for calculating the feedback control amount, for converting the number of data digits used for the control amount calculation into a shorter value as the deviation is smaller. 2. Feedback control of the engine control amount is performed using at least one of a proportional term and an integral term or a differential term, and the data conversion means shortens the number of data digits for the proportional term. The feedback control device according to claim 1, characterized in that the feedback control device performs conversion.