JPH0338441B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a digital control method for a hydraulic actuator used for controlling control equipment of an automobile.

[Conventional technology]

FIG. 5 is a system diagram showing a conventional digital control device for a hydraulic actuator.

In FIG. 5, an engine 1 drives a hydraulic pump 2, and the pressure oil discharged from the hydraulic pump 2 is delivered to a pipe line 2.
Pressure oil is supplied to the solenoid valve 4 through the solenoid valve 4 and discharged from the solenoid valve 4, and returns to the reservoir 2c through the conduit 2d, and a safety valve 2b is provided between the conduit 2a and the conduit 2d. I am intervening.

The solenoid valve 4 connects the pipe line 2a to the pipe line 4a (reciprocating pipe line)
The pressure oil flowing to the hydraulic actuator 5 via
By controlling the hydraulic actuator 5 to one side or the other side, the hydraulic actuator 5 is configured to be operated and controlled to one side or the other side.
is configured to operate and control the fuel injection timing of a fuel injection pump in a load 6, for example, the engine 1, via means 5a.

The operation of the conventional configuration described above will be explained below.

The computer 3 calculates the state quantity to be set for the load 6,
For example, the command value co of the electric wire 3a that commands the fuel injection timing of the fuel injection pump, and the feedback signal value f (signal value output to the wire 6c) from the detector 6b that detects the current state quantity of the load 6. ) is calculating the deviation Er=co−f.

When a deviation occurs in the deviation Er, the computer 3 instructs the direction and amount of correction to correct the deviation, and the solenoid valve 4 operates the hydraulic actuator 5 according to the instruction. load 6
For example, the direction of advancing or delaying the fuel injection timing and its magnitude are corrected.

Conventionally, as a method of converting an electrical command signal from the computer 3 into a hydraulic energy command and operating the hydraulic actuator 5 according to the hydraulic energy command, the electrical signal is converted into a nozzle/flatter movement. There is an electro-hydraulic servo valve that converts the hydraulic energy into the hydraulic power and controls the level of hydraulic energy by its movement.

However, this electro-hydraulic servo valve is expensive.

For this reason, a method has emerged that uses inexpensive solenoid valves for electro-hydraulic conversion.

The most well-known control method using these solenoid valves is the so-called PWM method, in which the on-off (on-off) of the solenoid valve is constantly turned on and off in an oscillatory manner, and the on-off duty ratio is changed. In this manner, the direction and magnitude of the state quantity under the load are controlled.

However, this method also has major drawbacks. The reason is that the solenoid valve is constantly turned on and off vibratingly, so the durability of the solenoid valve is considerably reduced.

As a result, some devices employ the following control method to control the configuration shown in FIG. 5 above.

The basic idea is to first, under certain conditions, experimentally determine the relationship between the on or off time of the pulse signal applied to the solenoid valve 4 and the amount by which the load 6 is modified during that time. and store this in the computer 3. In actual control, the computer 3 calculates the driving time of the solenoid valve 4 corresponding to the deviation Er by referring to the stored value, and drives the solenoid valve 4 according to the calculated time. do.

That is, each time the computer 3 detects the deviation Er, the computer 3 stores the time width of a single pulse corresponding to the magnitude of the deviation Er in the storage device of the computer 3.
The pulse is drawn from the ROM, and the time width of the output single pulse is set to the time width of the drawn value, and then output to the load side.

As a result, the deviation Er should originally be corrected by only one single pulse transmission. However, if an error in the correction still occurs after that one correction, the same control may be repeated for a new deviation Er corresponding to the error.

Therefore, compared to a method such as the PWM method, which constantly vibrates the solenoid valve on and off as described above, the number of times the solenoid valve 4 is turned on and off in Fig. 5 is extremely small. .

[Problem to be solved by the invention]

However, in this control method, the drive time of the solenoid valve 4 is determined in advance based on experimental values under certain conditions, so for example, when the engine speed changes, the flow rate of the hydraulic pump changes accordingly. When the conditions become different, such as when the load changes, it becomes difficult to correct the load deviation with only one command signal of a single pulse. That is, in order to correct the deviation, it is necessary to drive the solenoid valve 4 by outputting a pulse signal two or more times.

This means that compared to the case where the load deviation can be corrected with a single pulse signal, multiple pulse signals must be output to correct the load deviation, which means that unnecessary operations are performed and the control becomes more difficult. There are problems such as decreased responsiveness.

Particularly in the control of an on-vehicle hydraulic actuator, a problem arises when the fixed displacement hydraulic pump 2 is driven by the engine 1, as in the case shown in FIG. 5 above.

It is the rotational speed n in engine 1
[rev./min.] and the displacement D [lit./rev.] of the hydraulic pump 2 is the product of the displacement D [lit./rev.] of the hydraulic pump 2.
Pressure oil flow rate per unit time discharged from Q [lit./
min.], so when the rotational speed of engine 1 changes, the pressure oil flow rate per unit time Q
This is because it changes.

In particular, when the engine 1 is used as a car engine, the change in rotational speed during driving is 10 to 10% compared to when the engine is idling.
It changes by a factor of 15.

Therefore, when the hydraulic actuator is digitally controlled using the pressure oil from the hydraulic pump 2 driven by the engine whose rotation speed changes in this way, the control sensitivity changes significantly. .

Also, when the control sensitivity changes greatly like that,
If the control sensitivity becomes excessively large, the control result tends to overshoot excessively, and conversely, if the control sensitivity decreases, the control result becomes dull.

An object of the present invention is to provide a digital control method for a hydraulic actuator, which controls the solenoid valve 4 infrequently on and off, and does not change the control sensitivity of the control system even if the rotational speed of the engine 1 changes as described above. Our goal is to provide the following.

[Means to solve the problem]

The hydraulic actuator 5 that operates the load 6 is operated by a solenoid valve 4 that controls the flow of pressure oil from the hydraulic pump 2 driven by the engine 1 to the hydraulic actuator, and the solenoid valve is controlled by: One or the other single pulse signal from the computer 3 selectively pumps the hydraulic fluid to one side or the other during the application of that signal, thereby causing the hydraulic actuator to move to one side or the other. or the other side, and the transmission of the pulse signal is performed when the deviation Er between the specified target value for the load and the set value of the load controlled by the operation of the hydraulic actuator is The application time width T _S of the single pulse signal, which is transmitted when the target tolerance deviation is outside of −Ero to +Ero, is the sum of the basic application time width To and the auxiliary application time width proportional to the deviation. It is characterized by the following improvements over the conventional control method described above.

When transmitting the signal, a correction coefficient c that is inversely proportional to the rotational speed of the engine is determined, and the basic application time width is calculated by multiplying the basic application time by the correction coefficient c. It is used by modifying it from time to time.

[Effect]

In the above-mentioned conventional digital control of the hydraulic actuator, when a deviation Er occurs in the control, as in the explanation of the above-mentioned conventional technology,
By transmitting only one pulse signal, the deviation
This is what we are trying to fix. Also,
In the conventional technique, the application time width of one pulse signal is the sum of the basic application time width To and the auxiliary application time width proportional to the deviation Er, as described above.

Here, the one pulse signal, that is, the single pulse signal, is a command signal to the solenoid valve that controls the transmission of pressure to the hydraulic actuator, and the application time width of the signal is the one that controls the solenoid valve. Open the valve,
This is the time width for operating the hydraulic actuator.

Further, among the application time widths, the basic application time width To is the time width from when the signal transmission starts until the hydraulic actuator starts operating.

On the other hand, within the application time width, the deviation
The auxiliary application time width proportional to Er is exactly the deviation Er with only one transmission of that single pulse signal.
This is the time span required for the hydraulic actuator to operate so as to be controlled within the permissible target range.

Here, the proportional value proportional to the deviation Er required for setting the auxiliary application time width is as described above.
This is determined experimentally or theoretically in advance.

Further, the pressure oil supplied to the electromagnetic valve is the pressure oil discharged from a fixed displacement hydraulic pump driven by the engine.

In such a conventional control method, the control of the present invention calculates a correction coefficient c that is inversely proportional to the rotational speed of the engine when transmitting the single pulse signal, and calculates the correction coefficient c that is inversely proportional to the rotational speed of the engine, and adjusts the application time T _S of the signal. Among them, the basic application time is replaced with a value obtained by multiplying the conventional basic application time by the correction coefficient c.

This means the following.

Usually, the hydraulic pump that supplies pressure oil to the vehicle-mounted hydraulic actuator is often of the fixed displacement type, as described above.

In addition, when the control solenoid valve is in its neutral position, the discharge pressure is adjusted so that the pressure oil discharge pressure from the hydraulic pump is at its lowest state in order to reduce the power loss of driving the hydraulic pump. It is often used in an unloaded state.

In this case, in order to actuate the solenoid valve to move the hydraulic actuator to one side or the other, the pressure that has been unloaded to the lowest pressure since the solenoid valve is actuated is required to actuate the hydraulic actuator. Time is required for the pressure to rise to a predetermined level.

According to experiments, the time for this pressure increase is
It is related to the pressure oil discharge flow rate per unit time of the hydraulic pump, and is roughly inversely proportional to the discharge flow rate.

Further, the above-mentioned auxiliary application time width, which is related to the pulse application time after the hydraulic actuator starts moving, is also influenced by the above-mentioned discharge flow rate. However, when follow-up control is considered as a commonly used form of control, the deviation Er in this control is usually not so large because the load always operates in accordance with the command value. Therefore, the deviation
The auxiliary application time width, which has a value proportional to Er, is often not greatly affected by control sensitivity.

In this case, the pressure oil discharge flow rate per unit time, which affects the control sensitivity, changes in proportion to the engine rotation speed, that is, the rotation speed of the hydraulic pump.

For this reason, the application time to the solenoid valve is corrected by the amount that the pressure oil discharge flow rate affects the control sensitivity as the engine rotational speed changes.

〔Example〕

Hereinafter, the present invention will be explained based on Examples.

FIG. 1 shows a system diagram of a hydraulic control device for carrying out the digital control method for a hydraulic actuator according to the present invention.

The differences between FIG. 1 and the conventional FIG. 5 are as follows.

A disk 1b for detecting rotational speed is fixed to the drive shaft 1a of the engine, and an electric wire 1d is inputted to the computer 3 from a detector 1c that detects the rotational speed of the disk 1b.The remaining configuration is shown in FIG. is the same as

The operation of the configuration of the embodiment of the present invention described above will be explained below.

FIG. 2 shows a flowchart of the calculations used by the computer 3 in FIG. 1, and the calculations are as follows.

Calculation L1: When the control device shown in FIG. 1 is turned on, the computer 3 starts this calculation.

Operation L2: Set the initial value to be used in the following calculations.

Calculation L2a: The rotational speed n of the engine 1 is detected by the detector 1c.

Calculation L2b: Coefficient c inversely proportional to its rotational speed n
Calculate.

Calculation L3: Detect the command signal from the electric wire 3a.

Operation L4: Detect the feedback signal from the detector 6c.

Calculation L5: Calculate the deviation Er between the value of the command signal detected above and the value of the feedback signal.

Calculation L6: It is determined whether a pulse signal voltage as an instruction signal is output from the calculator 3 to the electric wire 3b.

When it is determined in calculation L6 that the pulse voltage is being output (yes), the process proceeds to calculation L6a.

This means that the pulse signal being applied to the electric wire 3b drives the solenoid valve 4 while the signal is being applied, and as a result of this driving, the hydraulic pressure from the hydraulic pump 2 flows to the hydraulic actuator 5.
This means that the state of the load 6 is being changed.

Calculation L6a: Determine whether the absolute value of the deviation Er is larger than the absolute value of the target predetermined tolerance Ero, and determine the sign of the deviation and the sign of the driving direction during the control. Determine whether or not they match.

This judgment determines whether the deviation is overshooting, that is, whether the deviation has become the opposite side of the deviation from the deviation at the time of the signal transmission, exceeding the target allowable deviation Ero. .

In this case, no overshoot
If it is determined that the control is within the range of the allowable deviation Ero, or the control is insufficient, that is, the deviation Er in the control result is still on the deviation side at the time of the signal generation and is within the target allowable deviation Ero. This means that it has not been reached.

Therefore, when the determination is no, the process returns to calculation L2a to monitor the next deviation Er.

On the other hand, if the judgment in operation L6a has already been determined to be overshoot, the operation
Proceed to L6b.

Calculation L6b: As described above, when the deviation Er has already overshot, the control for correcting the deviation Er has become excessive, and the operation of the solenoid valve 4 must be stopped.

Therefore, calculation L6b makes the instruction signal output to electric wire 3b zero, eliminates the current flowing to the solenoid in electromagnetic valve 4, and returns to calculation L2a again.

Calculation L7: When it is determined in calculation L6 that the electric wire 3b and the pulse voltage are not output (no), the calculation shifts from calculation L6 to calculation L7.

In this calculation L7, the time Tf after the pulse voltage on the electric wire 3b disappears is a predetermined time.
It is determined whether or not it is greater than Td.

Here, the predetermined time Td is set to the delay time from when the pulse voltage in the electric wire 3b disappears until the solenoid valve 4 closes, or to a longer time.

Therefore, Tf being larger than Td means that the solenoid valve 4 has already been completely closed, and as a result, the operation of the hydraulic actuator 5 has also stopped. Conversely, Tf being smaller than Td means that the solenoid valve 4 is still open in either direction, and as a result, the hydraulic actuator 5 is still operating in either direction. There is.

In the above calculation L7, when Tf is smaller than Td (judgment is no), the hydraulic actuator 5 continues to operate for the above reason, and therefore the change in deviation Er due to this operation is further monitored. ,
The calculation returns to calculation L2a again.

In the calculation of calculation L7, when it is determined that Tf is larger than Td (determination is yes), the calculation shifts from calculation L7 to calculation L8.

Calculation L8: Absolute value of deviation Er is target allowable deviation Ero
Determine whether it is greater or less than the absolute value of.

When the determination is small (no), the operation returns to operation L2a again.

Here, the determination of no in calculation L8 means that the computer 3 applied a single pulse voltage signal to the wire 3b in the previous calculation L9, as will be described later.
This means that the deviation Er of the control result was within the desired allowable deviation range -Ero to +Ero as a result of the control performed at that time by transmitting only pulses.

In the calculation of calculation L8, when it is determined that the absolute value of the deviation Er is larger than the absolute value of the allowable deviation Ero (yes), that is, the control is overshoot or insufficient, the overshoot or the control deficiency is corrected. In order to return the deviation Er in the direction, it is necessary to drive the solenoid valve 4.

Therefore, when this determination is made, the process moves from calculation L8 to calculation L9.

Operation L9: Perform the following operation using the subroutine program shown in Figure 3.

Operation L9a: Starts subroutine operation.

Calculation L9b: Calculate the overshoot amount e or the undercontrol amount e (the difference between the absolute value of the deviation Er and the absolute value of the allowable deviation Ero).

Calculation L9c: Find the product (c×Bo) of the basic value Bo and the coefficient c found in the above calculation L2b, add the product and the overshoot amount e or the control deficiency amount e, and set this as ps. That is, ps=(c×Bo)+e (1).

Here, the basic value Bo in equation (1) is a value proportional to the basic application time TOR or TOL in FIG. 4.

Therefore, ps in equation (1) is a value proportional to the slope portion AR or AL in FIG.

Also, in this case, since the coefficient c is inversely proportional to the rotational speed n of the engine 1 as described above, its AR or
When the rotational speed n of the engine 1 decreases, the AL part moves upward like AR1 or AL1,
Conversely, when the rotational speed n of the engine 1 increases, it moves downward.

Furthermore, _the characteristics on the left side of _{the T S axis} in FIG. It shows the characteristics of the single pulse signal application time T _S when actuating the valve 4 to the other side.

Operation L9d: Multiply ps in equation (1) by a constant Ct, and set this as the application time T _S. That is, T _S =Ct×{(c×Bo)+e} (2), and T _S in this equation (2) becomes the application time T _S of the single pulse signal in FIG. 4.

Operation L9e: Set the value of T _S obtained from equation (2) above in the timer.

Calculation L9f: Set the value of the application time T _S in the timer and at the same time output a pulse signal voltage to the electric wire 3b (Fig. 1).

Note that the output is obtained by subtracting the elapsed time from the value of the application time T _S by the timer after calculation L9g.
This subtraction is performed until the result is zero. When the subtraction result becomes zero, an interrupt signal is generated from the timer, and the computer 3 temporarily interrupts the processing that was being performed up to that point and stops outputting the pulse signal.

The computer 3 then returns to the interrupted process and continues executing the process.

Operation L9g: The operation returns to operation L2a of the main routine program again, and the above-mentioned operation is repeated again.

In this way, the following can be understood from the above routine calculations.

As can be understood from the operation of the timer, the output of the pulse signal in calculation L9f of the subroutine in FIG. 3 is such that only a single continuous pulse for the T _S time is output.

In addition, after outputting a signal of a single pulse, the calculation returns to calculation L2a, and the new deviation Er after outputting the single pulse is monitored in calculation L5. No new pulse signal is output until L5.

Furthermore, when the new deviation Er does not overshoot, the monitoring of the deviation Er continues from the new calculation L6a back to calculation L2a.

Furthermore, when the new deviation Er is within the allowable deviation Ero, monitoring of the deviation Er continues from operation L8 to operation L2a again.

In monitoring such deviation Er, then,
When the calculation shifts to calculation L9f again and opens the solenoid valve 4, it must be done after confirming that the solenoid valve 4 is completely closed in calculation L7, and when the deviation Er deviates from the allowable deviation Ero. If not, the solenoid valve 4 will not be opened next.

For this reason, the solenoid valve 4 is designed to open to the minimum extent necessary, and the solenoid valve 4 is not constantly turned on and off vibratingly. .

Furthermore, a particularly important point in the above control is that the coefficient c in equation (1) or equation (2) is used, and its meaning is as follows.

Since the hydraulic pump 2 is of a fixed displacement type, the rotation speed of the hydraulic pump 2 increases (or decreases).
Then, the flow rate of pressurized oil per unit time from the pipe line 2a increases (or decreases).

On the other hand, when the deviation Er is within the allowable deviation Er and the solenoid valve 4 is not driven, the discharge pressure of the hydraulic pump 2 is unloaded, but the deviation Er increases and the solenoid valve 4 is not driven. At this time, the pressure increases from the lowest unloaded pressure to the pressure necessary to operate the hydraulic actuator 5, and the actual transition of the hydraulic actuator 5 begins from there.

In this case, the time required for the pressure to rise until the hydraulic actuator 5 starts moving depends on the pressure oil flow rate from the hydraulic pump 2, and is roughly inversely proportional to the flow rate, so it depends on the amount of change. The single pulse application time T _S is corrected.

In other words, since the flow rate of pressurized oil per unit time from the hydraulic pump 2 affects the control sensitivity as the engine speed changes, the basic application time component (ct x Bo) of the single pulse application time is This is what is being corrected.

Here, the correction is made by multiplying the basic application time component (ct×Bo) by a coefficient c that is inversely proportional to the value of the rotational speed n of the engine 1, and then applying the new basic The application time c×(ct×Bo) is used as the basic application time component of the present invention. As a result, the product of the pressure oil flow rate and the single pulse application time, that is, the control sensitivity, can always be kept constant for pulse generation at the same deviation Er.

〔Effect of the invention〕

As is clear from the above description, the effects of the present invention are as follows.

1) Even if the pressure oil flow rate per unit time, which affects control sensitivity, changes due to a change in the rotational speed of the engine 1 that drives the hydraulic pump 2, the application time T, which also affects control sensitivity, changes. On _{the S} side, the basic application time component of the application time T _S is modified in accordance with changes in the rotational speed of the engine 1. Therefore,
In the digital control method of a hydraulic actuator according to the present invention, it is possible to always maintain the control sensitivity at an appropriate constant value, and it is possible to maintain high control responsiveness without excessive overshoot. .

2) When the digital control method for a hydraulic actuator according to the present invention is used in a control device of an automobile, and when the automobile engine is used to drive the hydraulic pump 2 as its oil pressure source, the engine has a rotational speed of 10%. This can greatly contribute to eliminating the influence of changing the control sensitivity by approximately 15 times.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing a control device when using the digital control method for a hydraulic actuator according to the present invention.
FIG. 2 is a flowchart of a calculation program that implements the digital control method for a hydraulic actuator according to the present invention, and FIG.
The program is shown in a flowchart, and the fourth
The figure shows the basic characteristics of the application time T _S of the single pulse signal output to the electric wire 3b in FIG.
The figure shows a system diagram of a conventional digital control device for a hydraulic actuator. The main symbols used in the examples are as follows. 1: Engine, 1b: Disk, 1c: Detector, 1
d: Electric wire, 2: Hydraulic pump, 3: Computer, 4: Solenoid valve, 5: Hydraulic actuator, 6: Load, 6
b: detector, T _S : application time of single pulse signal,
Er: Deviation.

Claims (1)

[Claims] 1. The hydraulic actuator 5 that operates the load 6 includes:
It is operated by a solenoid valve 4 that controls the flow of pressure oil from a fixed displacement hydraulic pump 2 driven by an engine 1 to the hydraulic actuator, and the solenoid valve is controlled by one or the other from a computer 3. selectively pumps the hydraulic fluid to one side or the other during the application of the signal, thereby causing the hydraulic actuator to move to one side or the other. The control and the transmission of the pulse signal are performed when the deviation Er between the commanded target value for the load and the set value of the load controlled by the operation of the hydraulic actuator is equal to the allowable deviation of the target - Ero The application time width T _S of the single pulse signal is the sum of the basic application time width T ₀ and the auxiliary application time width proportional to the deviation. In control, when transmitting the signal, a correction coefficient c that is inversely proportional to the rotational speed of the engine is obtained, and the basic application time width is a new value obtained by multiplying the basic application time by the correction coefficient c. A digital control method for a hydraulic actuator that is used by modifying the basic application time.