JPH0419401B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a digital valve closed loop control device in which an actuator is driven by a digital valve and the operation of the actuator is controlled by a feedback control method. (Conventional Example) A conventional closed loop control device is shown in FIG. In the figure, reference numeral 1 denotes a calculation means, which detects a difference between the value of an input instruction signal S for instructing the operation of the actuator to be controlled and the value of a feedback signal F, which will be described later, and generates a difference signal corresponding to the difference. Outputs V. A servo amplifier 2 has a constant amplification factor A, and outputs a drive signal AV obtained by multiplying the difference signal V by A. 3 is an electric/hydraulic servo valve, 4 is a fluid pressure source, and 5 is an actuator. The servo valve 3 has an internal torque motor that operates in response to a drive signal Av.
A combination mechanism of a nozzle and a flapper is used to convert it into a hydraulic pressure signal, and the hydraulic pressure signal is used to move the spool to adjust the hydraulic pressure supplied from the fluid pressure source 4 to the actuator 5. A sensor 6 detects the amount of operation of the actuator 5, and supplies the detection result to the calculation means 1 as a feedback signal F. Such a feedback control method uses electrical analog signals as the input instruction signal S and the feedback signal F, and amplifies the difference signal V between them in an analog manner with a servo amplifier 2 and supplies it to the torque motor of the servo valve 3. or input instruction signal S
, the feedback signal F, and the difference signal V are processed using digital signals, and a D/A converter (not shown) is used.
-analog converter) etc., the signal is converted into an analog signal and supplied to the torque motor of the servo valve 3. Then, the control is performed so that the difference between the input instruction signal S supplied to the actuator 5 to perform a predetermined operation and the feedback signal F indicating the actual amount of operation of the actuator 5, that is, the value of the difference signal V, is made zero. is performed, causing the actuator 5 to perform the operation instructed by the input instruction signal S. (Problem to be Solved by the Invention) However, in a closed loop control device using such a conventional servo valve, the flapper, spool, etc. inside the servo valve cannot be operated even by minute dust particles. Maintenance and management are complicated due to the occurrence of stagnation, and servo valves have drawbacks such as being large and expensive. Incidentally, there has been an attempt to improve this problem by using a digital valve that is resistant to dust, does not require special management of hydraulic fluid, and is inexpensive, instead of the servo valve shown in Fig. 6 above. However, in a closed-loop control device that uses such a digital valve, the response characteristic of the digital valve is determined by the maximum response pulse frequency Fmax of the pulse motor, so the response is relatively poor, and the servo control device shown in Figure 4 When the amplification factor of the amplifier 2 is increased, oscillations occur in the actuator output, and when the amplification factor of the amplifier 2 is decreased, the difference between the input signal S and the output of the actuator 5, that is, the steady-state deviation becomes large, making it impossible to obtain sufficient performance. Nakatsuta. That is, according to the feedback control method using this type of digital valve, the difference signal V from the calculation means 1 in FIG. The digital valve is opened and closed according to the value. However, if this amplification factor is increased too much in order to reduce the steady-state deviation between the output F of the actuator 5 and the input instruction value S and further improve the output response time, as shown in FIG. In response to the input instruction signal S, the opening degree θ of the variable throttle of the digital valve and the operation η of the actuator become unstable, and so-called overshoot and undershoot become large, resulting in a stable state, which is indicated by the input instruction signal S. There are problems in that the output exceeds the set target value H, which adversely affects the equipment, it takes time to settle down to the target value, and in the worst case, an oscillation state occurs. On the other hand, when the operation is stabilized and overshoot etc. are eliminated by lowering the amplification factor, the error between the output F of the actuator 5 and the input instruction value S, that is, the steady-state deviation δ increases, and satisfactory performance is obtained. Therefore, there was a problem in that the sufficient effect of feedback control could not be obtained. (Means for Solving the Problem) The present invention has been made in view of the above problems, and uses a digital valve to drive and control an actuator, detects the amount of movement of the actuator, and sends a feedback signal. The sensor that generates
The present invention is a digital valve closed loop control device comprising calculation means for detecting a difference between an input instruction signal instructing the operation of the actuator and the feedback signal to generate a difference signal. Here, the response performance of a digital valve has a characteristic determined by the highest response frequency of the pulse motor that drives the digital valve, and the response time at large amplitudes is slow, but the response time at small amplitudes is extremely fast. ,
For example, the maximum response frequency of a pulse motor is
If it is 4000pps, when opening and closing for 200 pulses,
50mS is required, but opening/closing for 10 pulses requires
2.5mS, 250μS for one pulse, and the response speed changes extremely depending on the amount of opening/closing. The present invention, which focuses on these characteristics, further includes a compression signal conversion means for converting the difference signal into a compression signal having logarithmic characteristics, 1/N power characteristics, etc. in the digital valve closed-loop control device, and an opening signal generating means for outputting an opening control signal based on the difference signal from the compression signal converting means and the compression signal from the compression signal converting means; The technical point is that the valve is provided with a pulse motor driving means for driving the pulse motor of the valve and instructing the valve opening degree. That is, the compressed signal converting means generates a compressed signal with a high compression rate in order to stabilize the operation of the closed loop device when the value of the difference signal is large, and generates a compressed signal with a high compression ratio when the difference signal is small. By generating a compression signal with a small ratio, the response of the entire control system is improved to realize a closed-loop control system with low steady-state deviation.On the other hand, the difference output from the calculation means is If the signal is integrated and the pulse motor is controlled to open and close in accordance with the integrated value, the steady-state deviation can be improved, although the response speed will be reduced. In order to utilize the advantages of these two, the opening control signal that satisfies stability and responsiveness is generated based on the difference signal output from the calculation means and the compression signal from the compression signal conversion means. It is characterized by being generated by means. (Embodiment) FIG. 1 is a block diagram showing an embodiment of a digital valve closed loop control device according to the present invention. First, to explain the configuration, numeral 10 denotes a calculation means, which detects the difference between an input instruction signal S supplied from the outside to instruct the actuator to perform a predetermined operation and a feedback signal F, which will be described later, and converts it into a difference signal V.
Output as . 11 is a compressed signal converting means, which amplifies the difference signal V and outputs a compressed signal W. Here, if the input/output characteristics of the compressed signal converting means 11 are expressed by the compressed signal W for the difference signal V=SF, then
As shown in the following equations (1), (2), or (3), the compression ratio is set so that the larger the difference signal V is, the higher the compression ratio is, and the smaller the difference signal V is, the smaller the compression ratio is. W=K・｜V｜ ^1/n =K・｜S−F｜ ^1/n …(1) W=K・S・(|S=F|/S) ^1/n …(2) W =L・log _a {|S−F|/S} …(3) However, in the above formulas (1) and (2), the constant S−F≧
If O, K is a positive coefficient; if SF<O, K is a negative coefficient, n is a real constant, and in the above equation (3),
L is a negative coefficient and a is a real constant, and the characteristics can be set by appropriately changing these coefficients. In order to realize this characteristic, the compressed signal converting means 11 is equipped with a device having an arithmetic function such as a microcomputer, and performs an arithmetic operation based on any one of the above equations (1) to (3). Or the above formula
A ROM that stores in advance data equivalent to the calculation result of one of the above formulas in order to obtain the same result as the calculation based on any of the formulas (1) to (3).
(read only memory), and the storage address of the ROM is designated according to the magnitude of the difference signal V to obtain the data. In addition, in devices that handle digital signals such as microcomputers and ROM, the difference signal V is converted into A/
The compressed signal W is converted into a digital signal by a D converter or the like, and the compressed signal W is also a digital signal. FIG. 2 shows a specific configuration of the integrating means 12, which includes a frequency converter 12a and an up/down counter 12b.
It is equipped with The frequency converter 12a determines the positive or negative polarity of the difference signal V, and generates a frequency signal with a frequency according to the magnitude |V| of the absolute value of the difference signal, and if the difference signal V has a positive value, the frequency signal fw , if it is negative, it is output as a frequency signal fcw. That is, the value of the difference signal V is +
If φ, the frequency signal of φ pulses per unit time
If the value of the difference signal V is -φ, a frequency signal fcw of φ pulses per unit time is generated.
The maximum frequency of the frequency signals fw and fcw is set to be equal to or lower than the maximum response speed of a pulse motor PM built in the digital valve 17, which will be described later. The up-down counter 12b counts the pulse trains fw and fcw from the frequency converter 12a, performs an up count when the pulse train fw is supplied, performs a down count when the pulse train fcw is supplied, and sends the counting result to the integral value signal R. Output as . 13 is an opening signal generating means, which generates an integral value signal R.
and the compression signal W, and generate the opening control signal SV based on the addition result. That is, the calculation according to the following equation (4) is executed. SV=K・(W+R)...(4) Note that k is a count value set as appropriate. Reference numeral 14 denotes a pulse motor drive means 3, which includes an excitation signal generation circuit 15 and a drive circuit 16, and controls the operation of the pulse motor PM of the digital valve 17 to adjust the opening degree of the variable diaphragm 18. The excitation signal generation circuit 15 determines the magnitude of the opening control signal SV, and generates an excitation signal to rotate the pulse motor in the closing direction if the current pulse motor position, that is, the valve opening is larger than the command value, and in the opening direction if the opposite is true. Outputs φ1 to φ4. FIG. 3 is a block diagram showing the configuration of the excitation signal generation circuit 15, including a comparator 15a, a discriminator 15b,
It is equipped with an oscillator 15c, a position counter 15d, and a pulse motor excitation phase conversion circuit 15e. A compression signal w is input to the comparator 15a, and the pulse motor excitation phase conversion circuit 15e outputs excitation signals φ1 to 1 to control each excitation coil of the pulse motor. φ4 is now occurring. The details are in the ``1982'' application previously filed by the inventor of the present application.
However, to give an overview here, the oscillator 15c generates a reference clock signal CL consisting of a pulse train, and adjusts the frequency to drive the pulse motor PM at the maximum response speed. are set equal. The comparator 15a is connected to a pulse motor PM supplied from a position counter 15d using an addition/subtraction counter.
detects the magnitude of the current position signal A and the opening control signal SV, and when the current position signal A is larger than the opening control signal SV, that is, when A>SV, generates an output Q1,
When the current position signal A is smaller than the opening degree control signal SV, that is, when A<SV, an output Q2 is generated. The determination circuit 15b specifies the addition/subtraction operation of the position counter 15d based on the outputs Q1 and Q2. When the output Q1 is input, the reference clock signal CL from the oscillator 15c is supplied to the position counter 15d as a subtraction pulse DOWN, and the position counter 15d performs a counting operation until A=SV.
The difference correction signal cw consisting of the subtraction result |A-SV| pulses is sent to the pulse motor excitation phase conversion circuit 15.
Output to e. Pulse motor excitation phase conversion circuit 15
e converts the difference correction signal CW into an excitation signal of φ1 to φ4 in the case of a four-phase pulse motor, and drives the pulse motor to rotate in a direction to close the variable diaphragm 18 of the digital valve 17 via the drive circuit 16. On the other hand, when the output Q2 is input, the reference clock signal CL from the oscillator 15c is supplied to the position counter 15d as an addition pulse UP, and the position counter 15d performs a counting operation until A=SV.
The difference correction signal ccw consisting of the addition result |SV-A| pulses is sent to the pulse motor excitation phase conversion circuit 15.
Output to e. Pulse motor excitation phase conversion circuit 15
When e is a 4-phase pulse motor, the difference correction signal ccw is φ
The signal is converted into an excitation signal of 1 to φ4, and the pulse motor PM is rotationally driven in a direction to increase the opening degree of the variable throttle 18 of the digital valve 17 via the drive circuit 16. Furthermore, when the signals Q1 and Q2 from the comparator 15a are not supplied, that is, when the current position signal A and the opening degree control signal SV are equal, the discrimination circuit 15b stops supplying the reference pulse CL of the oscillator 15c to the position counter 15d. Stop. Therefore, the position counter 15d does not perform addition/subtraction operations, the excitation signals cw and cw are not supplied to the pulse motor excitation phase conversion circuit 15e, and the pulse motor PM is not driven. In FIG. 1, the drive circuit 14 amplifies the drive signals φ1 to φ4 and supplies them to each excitation coil of the pulse motor. In this way, the pulse motor PM is controlled to drive by the difference between the current position signal A and the opening control signal SV, so it always follows the opening position instructed by the opening control signal SV. . 19 is a fluid pressure source, 20 is an actuator, and working fluid pressure according to the opening degree of the variable throttle 18 is supplied from the fluid pressure source 19 to the actuator 20;
Driven. 21 detects the amount of movement of the actuator 20;
The detected value is supplied to the calculation means 10 as a feedback signal F. The operation of the digital valve closed loop control device having such a configuration will be explained. In the calculation means 10, a sensor 21 indicating the input instruction signal S and the actual operation amount of the actuator 20 is provided.
The difference with the feedback signal F from is detected,
The difference signal V is converted by the compressed signal converting means 11 into any one of the above equations (1), (2), or (3), for example, the equation (1).
It is processed based on the formula and output as a compressed signal w. On the other hand, the difference signal V is separately processed by an integrating means 12, and an integral value signal R is output. The opening signal generating means 13 performs an addition operation on the integral value signal R and the compression signal w based on the above equation (4), and generates an opening control signal SV. The opening control signal SV is compared with the current position of the pulse motor PM by the excitation signal generation circuit 15, and excitation signals φ1 to φ4 are driven to drive the pulse motor PM by the difference between the current position and the opening control signal SV. The current is amplified by the circuit 14 and supplied to the pulse motor PM, causing the pulse motor PM to equally follow the opening control signal SV. The pulse motor PM adjusts the opening degree of the variable throttle 18 by rotating forward or reverse according to the excitation signals φ1 to φ4, and operates the actuator 20 from the fluid pressure source 19.
Adjust the hydraulic pressure supplied to the FIG. 4 shows that this feedback control improves the steady-state deviation and responsiveness of the actuator 20 to the input instruction signal S. Here, FIG. 4 shows the characteristics of this embodiment, and when compared with FIG. 7, FIG.
1 and the opening signal generating means 13 are not used, but the difference signal V from the calculation means 1 is amplified using a servo amplifier having a constant amplification factor to control the operation of the pulse motor PM. As shown in the figure, the amplification factor G of the amplifier is 2000,
This is a case where the input instruction signal S is set at 0.4 m/sec and the input instruction signal S is supplied in a stepwise manner. In FIG. 7, large overshoot and undershoot occur in the opening degree θ of the variable throttle 18 of the digital valve 17 in response to the input instruction signal S, and it takes a long time to stabilize at a constant value.
Furthermore, the operation η of the actuator 20 is unstable due to the instability of the opening degree θ, and it takes a long time to stabilize. The difference δ from the instructed target value H is extremely large. Therefore, it can be said that the actuator 20 cannot be made to quickly perform the desired operation, resulting in poor control performance. On the other hand, FIG. 4 uses the digital valve 17, fluid pressure source 19, actuator 20, etc. under the same conditions as in FIG. 13 is used. In addition, in the above formula (2), n=8, K=400,
The input instruction signal S is set to 0.4 m/sec, and the lowest amplification factor is set to 400.The amplification factor G ^* =W/V of the compressed signal converting means 11 at this time is shown in the following table as an example. It changes with respect to the difference signal as follows.

[Table] As shown in FIG. 3, the opening degree θ ^* of the variable throttle 18 of the digital valve 17 in response to the input instruction signal S stabilizes at a constant value in a very short time, and this opening degree θ ^*
Since the operation of the actuator 20 is also stable, η ^*
will stabilize in a short period of time. Moreover, actuator 2
The difference between the value in a state where 0 is stable (stable state) and the target value H indicated by the input instruction signal S, that is, the steady-state deviation δ ^*, is extremely small. Thus, compared to conventional amplifiers, the difference signal V
Since the amplification factor of the opening control signal SV can be increased overall, the difference δ ^* between the target value H and the set value of the actuator 20 can be made extremely small. Even if the rate is increased, an unstable state such as oscillation does not occur, so the actuator 20 can quickly perform the desired operation, and responsiveness is improved. Incidentally, in the compressed signal converting means 11 of this embodiment,
Although the above formulas (1) to (3) are used, the present invention is not limited to this. As the value of the input difference signal increases, the compression ratio increases, and as the value of the difference signal decreases, the compression ratio decreases. Any material having such characteristics can be applied. FIG. 5 is a block diagram showing another embodiment. First, if the configuration is shown corresponding to the block diagram of FIG. 1, the difference is that the detection signal from the sensor 21 is converted to a feedback signal FD consisting of a digital signal through the A/D converter 22, and this is calculated. The signal is supplied to the means 10A, and a difference signal V, which is the difference between the signal and the input instruction signal SD, which is a digital signal, is generated as a digital signal. The compressed signal generating means 11A is the compressed signal generating means 11 of FIG.
The opening signal generating means 13A corresponds to the opening signal generating means 13 in FIG.
It is made up of memory elements such as (Only Memory). The compressed signal conversion means 11A converts the above formula (1) into the so-called address area specified by the value (numerical value) of the difference signal V.
Numerical data corresponding to the compressed signal w resulting from the calculation is stored in advance. When the difference signal v is supplied, the difference signal v becomes a so-called address signal, and a compressed signal (numerical value) w corresponding to the magnitude of the difference signal v is output from the address area. Similarly, the opening signal generating means 13A is composed of a ROM or the like having a storage area arranged in a matrix, and the compressed signal w from the compressed signal converting means 11A converts the column address of the storage area into the integral from the integrating means 12. The configuration is such that the value signal R becomes the row address of the storage area. In the address area specified by the compression signal w and the integral signal R, a predetermined opening control signal SV obtained by the opening signal generating means 13 in FIG. An opening control signal that is stored in advance and corresponds to the compression signal w and the integral value signal R.
It is designed to output SV. This embodiment also achieves the same effects as the first embodiment, and also simplifies and downsizes the circuit configuration. (Effects of the Invention) As explained above, according to the present invention, the compression signal conversion means stabilizes the operation of the closed loop device when the value of the difference signal due to the difference between the feedback signal and the input instruction signal is large. A compressed signal with a large compression ratio is generated in order to improve the response of the entire control system by generating a compression signal with a large compression ratio when the difference signal is small, thereby creating a closed loop with small steady-state deviation. On the other hand, if the above-mentioned difference signal is supplied as a control signal to the pulse motor as it is, there will be problems with stability, etc., but the response speed is fast, so the opening signal generating means is used to generate these two signals.
The system generates an optimal opening control signal to take advantage of the strengths of the operator, and drives and controls the digital valve based on this opening control signal, thereby providing a digital valve closed-loop control device that satisfies stability and responsiveness. can do.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of the amplification means in FIG. 1, and FIG. 3 is a block diagram showing the configuration of the excitation signal generating means in FIG. 1. , FIG. 4 is a characteristic diagram showing the effects of the present invention, FIG. 5 is a block diagram showing another embodiment of the present invention, FIG. 6 is a block diagram showing a conventional example, and FIG. 7 is a drawback of the conventional example. FIG. 10, 10A... calculation means, 11, 11A...
Compressed signal conversion means, 12... Integration means, 13, 1
3A...Opening degree signal generation means, 14...Pulse motor drive means, 15...Excitation signal generation circuit, 16...
... Drive circuit, 17 ... Digital valve, 18 ... Variable throttle, 19 ... Liquid pressure source, 20 ... Actuator, 21 ... Sensor, 22 ... A/D converter.

Claims (1)

[Scope of Claims] 1. A digital valve that controls a working fluid from a fluid pressure source driven by a pulse motor and drives an actuator with the working fluid, and a digital valve that detects the amount of operation of the actuator and generates a feedback signal. comprising a sensor and a calculation means for detecting a difference between an input instruction signal instructing the operation of the actuator and the feedback signal and generating a difference signal, and is driven by a working fluid controlled by the digital valve. In a digital valve closed loop control device that detects the operating amount of an actuator and performs feedback control of the actuator, the compression ratio increases as the value of the difference signal increases, and the compression ratio decreases as the value of the difference signal decreases. Compressed signal converting means for generating a small compressed signal; Integrating means for performing time integral calculation of the difference signal from the calculating means and outputting an integral value signal; and performing an addition operation based on the compressed signal and the integral value signal. an opening signal generating means for generating a degree control signal value; and a pulse motor driving means for driving a pulse motor in the digital valve to set the valve opening degree based on the opening degree control signal from the opening degree signal generating means. A digital valve closed loop control device characterized by comprising: