JPS63103303A - Feedback controller - Google Patents

Abstract

PURPOSE:To improve the stability of a feedback controller by reducing the gradient of the diode rectifying characteristics immediately before the end of the rise and fall of a deviation control signal. CONSTITUTION:A feedback controller for flow rate and pressure of a variable capacity type hydraulic pump contains the feedback control systems for both flow rate and pressure, the changeover switches for both feedback control systems, and the compensating circuits 10 and 11 including a phase advance compensating circuit 12 and a phase delay compensating circuit 13. A 1st diode D1 and a 2nd diode D2 are provided to the circuit 12. The phase of the deviation control signal supplied from a control element is controlled by both circuits 12 and 13. Then the deviation control signal gives the feedback control to a controlled system. In this phase control process, the diode D1 is turned off by a large potential difference at the rise of the deviation control signal. Thus the diode D1 has a quick rise and is turned off immediately before the end of its rise to reduce the overshoot.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a feedback control device for a variable displacement hydraulic pump or the like, and particularly to an improvement in a feedback control system equipped with a compensation circuit for improving the characteristics of the system.

(Prior Art) Conventionally, for example, in a feedback control system of a variable displacement hydraulic pump, a pump swash plate as a controller, operating means such as an electric circuit or a hydraulic actuator for operating the pump swash plate, and This operating means is equipped with a feedback control element such as a control circuit that outputs a deviation control signal equal to the deviation from the target value, and the inclination angle of the pump swash plate is controlled by #I in response to this deviation control signal. By squeezing, you can control the oil flow rate and working pressure to the actuator connected to the hydraulic pump! Feedback ilu to target value υ] Do as I say.

By the way, the above L! ] In a feed-balance control system, a phase lead compensation circuit and a phase lag compensation circuit are generally provided to improve the abnormality (transient response) of the main system, and these compensation circuits can be operated from the control element. By intervening in the output path of the deviation control signal to the element and changing the deviation control signal Tachikawa appropriately, the characteristics of the feedback control system in A can be realized almost as expected; i! I try to do that.

(Problem to be solved by the invention) However, when the compensation circuit is provided as described above, in the phase lead compensation circuit, the parallel circuit of the capacitor and the resistor is
By setting the value of this resistor low, it is desirable to perform the rise and fall of the deviation control signal with good responsiveness, but in this case, due to this good responsiveness, , overshoots and undershoots tend to occur after the rise and fall of the deviation control signal, resulting in a disadvantage of reduced stability.

The present invention was developed based on this idea, and takes into consideration the rectifying characteristics of diodes, and when the potential difference between the two ends becomes less than the forward voltage drop value, the current flow is stopped by turning 4. The purpose of this is to reduce the slope of the rising edge and falling edge of the deviation control signal, thereby ensuring good response to the rising edge and falling edge. At the same time, the objective is to improve stability by preventing subsequent overshoots and undershoots.

In order to achieve the above object, the solution means of the present invention, as described above, includes a control object (1) and an operating element (1) for operating the control object (1). 2) and a control element (5) that outputs a deviation control signal to the operating element (2), and constitutes a feedback control system <8.9> for the control object (1). Assumes @. A phase lead compensation circuit (12) and a phase lag compensation circuit for improving the characteristics of the feedback control system (8, 9>) are provided in the output path of the deviation control signal from the control element (5) to the operation element (2). (13), and this phase lead compensation circuit (12) is connected to the capacitor (C1) and the above-mentioned operating element.
) side, the first diode (Dl) allows current to flow to the
A first resistor (R1) with a low resistance value connected in series with the second diode (Dl) that allows current to flow to the control element (5) side. One bridge is formed by a parallel circuit (19) in which two resistors (R2) and a third resistor (R1) having a high resistance value are connected in parallel.

(Function) With this configuration, in the present invention, the phase of the deviation control signal from the shij'm element (5) is appropriately adjusted by the phase lead compensation circuit (12) and the phase lag compensation circuit (13). I! is input to the operating element, and the operating element (2) causes I!
By repeating feedback control of Ill6i1 object (1), Ill of oil and flI of pressure etc.
III I will converge to the target value.

At that time, deviation! IHa signal phase lead compensation circuit (12)
In the syntax adjustment process, the deviation ~j control signal turns off the first diode (Dl) due to the large potential difference at its rising edge, and the first resistor (R1) with a low resistance value is turned off.
Therefore, the deviation control signal after passing through the phase lag compensation circuit (13) has a large change in current value and rises quickly, and good response is obtained, and the deviation control signal passes through the phase lag compensation circuit (13) immediately before the end of this rise. Then, the potential difference becomes less than the voltage drop value in the direction around 1 of the first diode (Dl),
The first diode (Dl) is turned off, and the current flows through the third resistor (R3), which has a high resistance value, so that the 1l
The iFIt change becomes steep, and the rise ends with good stability without overshooting.

Similarly, in the falling part of the deviation control signal, the second diode (<02) is turned on due to a large potential difference, and the signal flows through the second resistor (R2) with a low resistance value, so the falling part becomes quick and good. Responsiveness is obtained, and just before the end of this fall, the second diode (Dl) turns off as the potential difference decreases, and the current flows through the third resistor (R3) with a high resistance value. As a result, the current changes rapidly and the trailing edge ends with good stability without undershooting.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a flow Φ and pressure feedback control device of a variable displacement hydraulic pump. In the figure, <1) is a pump swash plate of a hydraulic pump that is a single control target in feedback control of both flow rate and pressure, and (2) is an operation for adjusting the inclination angle of the pump swash plate (1). It is an amplifier circuit as a means, and in the circuit (2), each deviation control signal of flow rate and pressure (described later) is provided.
The main amplifier <
2a) is provided.

Further, (3) is a swash plate angle sensor that detects the inclination angle of the pump swash plate (1), that is, the discharge flow rate of oil, and (4) is an actuator (not shown) that receives oil supply from the pump swash plate (1). ), a pressure sensor detecting the working pressure of the oil at (5)
receives the output signal of the swash plate angle sensor 1) and calculates the angle difference between the actual tilt angle value of the pump swash plate 1) and the target tilt angle corresponding to the target flow rate, that is, the flow rate. Zuru 1st
A subtraction circuit (5a) receives the output of the pressure sensor (4) and calculates the pressure deviation between the actual working pressure value of the oil and its target value. Kanara system 4
A reduction circuit as an element, comprising a flow deviation control signal (voltage signal) from the first reduction circuit (5a) of the subtraction circuit (5) and pressure deviation control from the second reduction circuit (5b). The signals (voltage signals and voltage signals) can be output to the amplifier circuit (2) through the inverting amplifier circuits <6) and <7), respectively, and the amplifier circuit (2) has a flow rate deviation of 1! When you receive the jiJ signal,
A flow rate feedback control system (8) is configured to increase or decrease the inclination angle of the pump swash plate (1) in accordance with the flow rate deviation control signal value to increase or decrease the discharge flow rate to its target value. When the amplifier circuit (2) receives a pressure difference control signal from the time reduction circuit (5), it adjusts the inclination angle of the pump swash plate 1) according to the pressure difference control signal value to control the discharge. A pressure feedback control system (9) is configured to adjust the working pressure of oil by adjusting the flow rate.

Furthermore, (10) is the flow rate feedback control system (8).
) is a compensation circuit for flow @ control in which the compensation constant is appropriately adjusted to improve the characteristics (frequency response), (11) is a compensation constant to similarly improve the characteristics of the pressure feedback control system (9). is a compensation circuit for pressure control in which Fl is appropriately adjusted, and each compensation constant is selected to be a different value depending on the difference in the width of the control loop for flow rate control and pressure control. .

And each feedback of al and pressure! ff1IW
Sometimes each compensation circuit (10), (11) is connected to said attenuation circuit (5) in order to connect the respective compensation circuit (10) or (11) to the control loop of the pump swash plate (1). The inverting WI width circuits (15) and (16) are connected in series, and then connected in parallel with each other, with first and second changeover switches (17) at both ends of the parallel circuits.
, (1g) is connected, and the camphor reduction circuit (5) 11!
The first changeover switch (17) of
0), (11) are selectively switched between the first dimming circuit (5a) side and the second subtracting circuit (<5b)ffllll of the dimming circuit (5), and the second changeover switch ( 18) is for selectively connecting a compensation circuit (10) for flow 1 control and a compensation circuit (11) for pressure control to the amplifier circuit (2).

In addition, (20) is the aforementioned two changeover switches (17).

(18) is controlled by 17J ~], the deviation amount determining circuit (20) is a flow rate deviation control circuit that controls the flow rate deviation from the -th subtraction circuit (5a) of the above-mentioned flow rate reduction circuit (5). signal and second
Receives the pressure slight difference control signal from the reduction circuit (5b), determines the control system that has a larger feedback amount (sensor output) with respect to the target value from the difference value between the two, and performs flow rate or pressure feedback. ! It has the ability to detect when control is required, and when flow control is required, both changeover switches (17), (18) are configured to switch the first and second changeover switches (17), (18) to the flow rate side. 18), the flow rate deviation control signal from the reduction circuit 5 is output to the compensation circuit (1) for general dragon control corresponding to the flow rate feedback control system.
0) to the amplifier circuit 2. On the other hand, when the pressure secondary side is required, a switching signal is applied to switch the changeover switch (17L (181) to the pressure side), and a pressure deviation control signal from the subtraction circuit 5 is output. The output is made to the inflator circuit 2 via a pressure control compensation circuit (11) corresponding to the pressure feedback control system.

Each of the compensation circuits (101, (11) for the above-mentioned flow rate shift [JtI17T] and pressure control) is a phase lead compensation circuit (12) for improving responsiveness, as shown in Fig. @2, respectively.
At the subsequent stage of the phase lead compensation circuit (12), a phase lag compensation circuit (13) that increases the loop gain by J times without significantly affecting the transient response;
) and an amplifier (14) that increases the signal width by #1 at the subsequent stage
The phase lead compensation circuit (12) includes a capacitor (01)
, a first variable resistor (R1) whose resistance value is adjusted low, and a second variable resistor (R2) whose resistance value is similarly adjusted low.
), a third resistor (R3) with a high resistance value, and a first resistor (R3) that allows current to flow from the book reduction circuit (5) to the amplifier (2).
A diode (Dl) and a second die (D2) that allows current to flow from the amplifier (2) to the subtraction circuit (5) conversely.
), the first diode (Dl) is connected in series to the first resistor (<R+), and the second
The second diode (2) is connected in series to the resistor (R2), and these two resistors (R+), <R2) each have the diodes (D+) and (02) connected in series. Then, connect the third resistor (: (R3)) and the capacitor (
A parallel circuit M(19> is formed by connecting the first and second diodes (C1) in parallel with
The rectification characteristics of D+ ) and (02) are such that when a head voltage is applied, the j-term direction pressure value is the forward voltage drop value, that is, the voltage value at which the forward current begins to flow (for example, 0.6 V).
It turns off in the following cases, and turns on when the voltage exceeds the voltage drop in the direction below, and also turns on when the reverse voltage is detected tIf:! Sometimes it becomes a constant turn-off.

Further, the phase lag compensation circuit (13) is composed of a series circuit of another capacitor (C2) and a resistor (R4).

Therefore, in the above embodiment, the swash plate angle sensor (3
) and the working pressure signal of the oil from the hydraulic pump detected by the pressure sensor (4) are constantly input to the reduction circuit (5). The deviations between the detected values of flow rate and pressure and their respective target values are constantly displayed in this true control circuit (5), and the deviation i judgment circuit (20 ) for example the flow rate! 9. If it is determined that JS is necessary, the first
and the second changeover switches (17) and (1B) are respectively switched to the flow rate side, and the compensation circuit (10) for flow rate control is connected to the control loop of the pump swash plate (1), and the p reduction circuit is connected to the control loop of the pump swash plate (1). (5) The flow rate deviation signal of the first reduction circuit <58) is inputted to the amplifier circuit (2) via this flow rate control compensation circuit (10), 4
Since the inclination angle of the ζ pump swash plate (1) is feedback-controlled, the characteristics of the flow rate feedback system I'a system are realized to almost the desired values by the compensation circuit (10) for flow rate control, and the hydraulic pump The oil discharge flow rate can be adjusted to the target value.

At this time, if the flow rate deviation control signal from the subtraction circuit 5 has a pulse waveform in which the voltage value exceeds the predetermined value Vo for a predetermined period of time as shown in FIG. As soon as the first diode (Dl) is turned on due to the large potential difference before and after the lead compensation circuit (12), this small difference signal flows through the first resistor (R1) with a low resistance value.
After that, compensation episode 1 (12) 1! When the potential after ``I'' becomes smaller and becomes less than the 11j direction voltage drop value (for example, 0°6V) of the first diode (Dl), this first diode (D+) turns off. The signal will flow through the third resistor (R3) with a high resistance value.

In this way, in the early and middle stages of the rise, the flow passes through a path with low resistance, and at the end of the rise, it flows through a path with high resistance, so the deviation after passing through the phase lag compensation circuit ((13)!
! As shown in the same figure (b), the IIJ control signal rises quickly in the early and middle stages of the rising part, providing good response, and its slope becomes sharp at the end of the rising part. As a result, the predetermined value Vo is reached with good stability without overshooting, as shown by the rectangular line in the figure.

In addition, the action of the phase lead compensation circuit (12) at the falling part of the flow rate deviation body signal is the same as above, and at the beginning and middle of the falling part, the second diode (Dl
) turns off, while at the end of the falling part, the second diode (Dl) turns off as the potential difference decreases,
As a result, the flow MfH difference control signal flows through the second resistor 1 (R2:') with a low resistance value in the early and middle stages of the falling part.
At the end of the falling part, the flow passes through the third resistor (R3) with a high resistance value, so if it rises with good response, it changes violently and reaches zero value with good stability without undershooting. will reach. Therefore, it is possible to prevent overshoot and undershoot and improve stability while ensuring good responsiveness.

In addition, since the first and second resistors (R+) and (R2) are each composed of variable resistors, the response speeds of the rising portion and the initial and middle periods of the rising portion can be adjusted depending on the flow rate and pressure feedback control system, respectively. can be changed.

The above explanation took the flow rate feedback control l1 as an example, but 1. At the time of ejection feedback ffi' control, the compensation circuit only replaces the compensation circuit for pressure ˜I (11), and its operation is the same.

In the above embodiment, the case where the flow rate and working pressure to the actuator connected to the hydraulic pump are feedback-controlled was explained, but the present invention is not limited to this, and in addition, the horsepower It goes without saying that a device with M control can be used in the same way, and it can be applied not only to the control of hydraulic pumps but also to the wholesale of feed valves such as motors.

(Effects of the Invention) As explained above, according to the feedback control device of the present invention, when a compensation circuit for improving characteristics is provided in the output path of the deviation control signal from the control element to the operation element, The resistance for the phase lead compensation circuit is configured with one with a low resistance value and one with a high resistance value, and the deviation control signal is set to a low resistance value according to the rectification characteristics of the diode in the early and middle stages of the rising and falling parts. By passing it through a resistor with a high resistance value at the final stage, we aim to lower the response speed only in this long period, so that we can ensure good response and prevent the occurrence of bassute or undershoot. It is possible to prevent this and improve stability.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and Fig. 1 is a block diagram of a hydraulic pump in which the pump is used for feed-packed control of the flow rate and pressure of two oils, and Fig. 2 shows specific information of the compensation circuit. FIG. 3 is an electrical circuit diagram showing the operation. 1)...pump swash plate, (2)...increase, aphrodisiac circuit,
(3)...Swash plate angle sensor, (4;1...pressure sensor, 5)...culm reduction circuit, 8)...flow rate feedback control system, (9)...pressure feedback control system,
(10)...Compensation circuit for flow rate control, (11)...Compensation circuit for pressure control, (12)...Phase lead compensation circuit,
(13)... Phase lag compensation circuit, (C1)... Capacitor, <R+)... First resistor, (R2)... Second resistor, (R3)... Third resistor, ( Dl)...1st
Diode, (Dl)...second diode. Figure 3 El? Fl'1 Figure 2

Claims (1)

[Claims] (1) comprising a controlled object (1), an operating element (2) for operating the controlled object (1), and a control element (5) for outputting a deviation control signal to the operating element (2); Controlled object (1
), in which the output path of the deviation control signal from the control element (5) to the operating element (2) includes the feedback control system (8, 9). The phase lead compensation circuit (12) is equipped with a phase lead compensation circuit (12) and a phase lag compensation circuit (13) that improve the characteristics of the capacitor (
C_1), a first resistor (R_1) with a low resistance value connected in series with the first diode (D_1) that allows current to flow to the operating element (2) side, and the control element (5) side. A second resistor (R_2) with a low resistance value connected in series to a second diode (D_2) that allows current to flow to the second diode (D_2) and a third resistor (R_3) with a high resistance value are connected in parallel. A feedback control device comprising a circuit (19).