JPH0374612A - Flow control device for valve - Google Patents

Abstract

PURPOSE:To prevent the hunting and response delay of a valve and stabilize the flow control by adding devices measuring the fluid pressure at the inlet and outlet of the valve, and multiplying a command signal by the inverse number of the square root of the difference between the inlet pressure and the outlet pressure. CONSTITUTION:Pressure gauges 5-7 measuring the fluid pressure are provided at the inlet and the outlet of a valve 1. An arithmetic device 9 determines the difference DELTAP between inlet pressures 6 and 7 and the outlet pressure 5 and calculates the inverse number of its square root. It multiplies a deviation signal between the command flow and the measured flow or a command signal PID-controlled with the deviation signal by the inverse number. The stable flow control can be continued without causing the hunting and response delay of the valve 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tMm control device for a valve, and particularly to a flow rate control device for a valve used to drive a hydraulic/pneumatic actuator.

[Prior Art] A device that controls the flow rate of fluid that passes through a directional valve (hereinafter referred to as a valve) provided between a pressure source and an actuator in order to control the operation of a hydraulic or pneumatic actuator to a desired speed. As shown in Figure 6, the flow rate that actually flows through the valve is measured and fed back to the command flow rate, and the flow deviation between the command flow rate and the measured flow rate is calculated using PID.
The control outputs a command signal to the valve controller, and the valve controller outputs an electric current tIL proportional to the input command signal to the valve solenoid, drives the valve, and adjusts the valve entrance area to control the flow rate. A controlling structure is used.

[Problems to be Solved by the Invention] However, in the tfA amount control device for a valve having the above structure, even if the PID control gain is set to an optimal value when the actuator is under no load, the actuator is subject to an external load. When this occurs, the differential pressure Δp before and after the valve changes, and the gain of the entire control system changes in proportion to the square root FΔ of the differential pressure. When the above-mentioned F∆-lower becomes large, hunting occurs in the valve, and when the F∆-lower becomes small, the settling time of the valve becomes longer, resulting in problems such as poor response.

The present invention has focused on the above-mentioned conventional problems, and has developed a system that allows optimal flow control at all times without changing the flow control characteristics due to changes in the load applied to the actuator, that is, changes in the differential pressure between the inlet and outlet of the valve. The purpose of the present invention is to provide a valve flow control device.

[Means for Solving Problem 11] In order to achieve the above object, the valve flow rate control device according to the present invention measures and feeds back the actual flow rate with respect to the commanded flow rate to the valve, and calculates the difference between the commanded flow rate and the measured flow rate. A command signal is output by controlling the flow rate deviation by PID control (including P control, PI control, and PD control), and the pressure of the fluid at the inlet and outlet of the valve is measured in the flow control device of the valve that drives the valve. A device is added and the command signal obtained by PID control of the deviation signal between the command flow rate and the measured flow rate or the deviation signal is multiplied by the reciprocal of the square root of the difference between the inlet pressure and the outlet pressure. In place of the fluid pressure measuring device installed at the port and outlet, a device for calculating the opening area of the valve is added, and instead of the reciprocal of the square root of the difference between the inlet pressure and the outlet pressure, the quotient of the opening area divided by the measured flow rate is calculated. The configuration is such that a deviation signal between the command flow rate and the measured flow rate or a deviation signal is multiplied by the command signal obtained by PID control.

[Operation] According to the above configuration, the flow rate deviation is multiplied by the reciprocal of the square root of the differential pressure across the valve or the quotient of the opening area of the valve divided by the measured flow rate, and this is input to the valve controller as a command signal. Therefore, the gain of the entire control system is constant regardless of differential pressure fluctuations before and after the valve, and if the PID control gain is set so that it is in the optimum state, the valve's gain will be constant regardless of fluctuations in the load applied to the actuator. Stable flow control can be maintained without hunting or response delays.

[Example] Hereinafter, an example of the valve flow rate control device according to the present invention will be described in detail with reference to the drawings.

FIGS. 1 and 2 show an embodiment according to claim (1). In FIG. 1, valve 1 with a meter-out pattern is a 4-point, 3-position switch with boat P connected to hydraulic pressure R2, bows A and B connected to actuator 3, and boat T connected to hydraulic oil tank 4. With the valve, the return circuit from the actuator 3 is throttled. T of this hydraulic circuit,
A; Pressure gauge near boat B5. 6.
7. is installed, and a flow meter 8 is installed in the hydraulic circuit extending from the T-boat to the hydraulic oil tank 4. Further, the computing device 9 is connected to the valve controller 10, and the wiring of the valve controller 10 is connected to both ends of the valve 1.

Said pressure gauge5. 6. 7. Let p+ and p2+ ps be the detected pressures, respectively. When the hydraulic oil flows from P→A−)B→T, the differential pressure Δp before and after the valve l becomes ΔI)=p3−p1. Also, the hydraulic oil is P
→ If it flows as B+A-1-T, ΔI):p2-1)
It becomes 1.

The command flow rate, the total flow rate 11 detected by the flowmeter 8, and the pressure pl+92+93 are input as electrical signals to the calculation device 9, and the calculation device 9 determines the flow direction of the hydraulic oil based on the sign of the command flow rate, etc. , Δp, and then calculate the reciprocal 1/7 Δ of its square root.

In addition, the flow rate deviation is determined from the command flow rate and the measured flow rate, and as shown in Fig. 2, the calculation result of multiplying this value by 1/7∆ is processed using the PID control method, and is sent as a command signal to the valve controller 10. Output. The valve controller 10 outputs a command current proportional to the input command signal to the solenoid of the valve 1 to adjust the opening area of the valve 1. By multiplying the flow rate deviation by 1/7Δ in this way, the influence of the differential pressure before and after the valve is eliminated on the entire transfer function, and the flow rate can always be controlled in an optimal state.

1/v/''-Δ may be multiplied by a command signal calculated by PID control of the flow rate deviation.Also, when using a meter-in throttle valve, P and A in FIG.

Install pressure gauges near each boat in B.

31st! 1 and FIG. 4 are embodiments according to claim (2). As shown in FIG. 3, a differential transformer is used to detect the stroke of the valve 1, that is, the amount of displacement from the reference position. A stroke position sensor 11 is installed at one end of the valve 1, and a flow meter 8 is installed in the hydraulic circuit extending from the valve 10T boat to the hydraulic oil tank d.

There is a 5th rl between the valve stroke S
! As shown in J, there is a relationship A=f(s), and the opening area can be calculated using the measured value of the valve stroke. Therefore, the command flow rate, the stroke signal of the valve l output by the stroke position sensor 11, and the flow meter 8
A signal of the measured flow rate outputted by is inputted to the calculation device 9, and the calculation device 9 calculates the flow rate deviation from the command flow rate and the measured flow rate. Also, from the stroke of the valve 1 and the measured flow rate, A,
/Q is calculated, the flow rate deviation is multiplied by this value, and the result of the calculation is subjected to PID control and output as a command signal to the valve controller 10. The valve controller 10 outputs a command current proportional to the command signal to the solenoid of the valve 1, and adjusts the opening area of the valve 1.

The flow rate Q passing through the valve 1 is expressed as follows, where C is the flow coefficient, A is the opening area of the valve, ρ is the density of the hydraulic oil, and Δp is the differential pressure before and after the valve. Therefore, C and ρ can be considered constants, so by multiplying the flow rate deviation by A/Q, as shown in Figure 4, the influence of the differential pressure across the valve can be reduced on the entire transfer function. Therefore, control can always be maintained in an optimal state.

In this way, in the present invention, the measured flow rate data includes an element below the square root FK of the differential pressure across the valve, which changes the gain of the entire transfer function and causes hunting of the valve spool and response delay. It is estimated that FΔ
When we took steps to remove the effects below, we found that the experimental results were in agreement with the estimation.

In this embodiment, a differential transformer is used as the valve stroke position sensor, but the present invention is not limited to this, and a magnetic sensor, magnetostrictive sensor, etc. may also be used.

Furthermore, in the case of a valve whose spool is driven by a stepping motor, the number of rotational steps of the stepping motor is proportional to the valve stroke, so the valve stroke can be calculated by counting the number of rotational steps. Therefore, a stroke position sensor is not required.

[Effects of the Invention] As explained above, according to the present invention, the flow deviation calculated from the command flow rate and the measured flow rate detected by the flowmeter is determined by the reciprocal of the square root of the differential pressure before and after the valve or by the opening area of the valve. Since this is multiplied by the quotient of the measured flow rate and inputted to the valve controller as a command signal, the gain of the entire control system remains constant regardless of differential pressure fluctuations before and after the valve, resulting in an optimal state of - degrees. If the PID control gain is set so that the flow rate control can be maintained stably without causing valve hunting or response delay, regardless of changes in the load applied to the actuator.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram showing the configuration of a valve flow rate control device according to an embodiment of claim (1), FIG. 2 is a plot diagram of flow rate control in the flow rate control device of FIG. 1, and FIG. is a hydraulic circuit diagram showing the configuration of the valve flow rate control device according to the embodiment of claim (2), FIG. 4 is a block diagram of flow rate control in the flow rate control device of FIG. 3, and FIG. 5 is a valve stroke; FIG. 6, which is a diagram showing the relationship with the opening area of the valve, is a block diagram of flow rate control in a conventional valve flow rate control device. 1◆O◆◆・Valve 3...◆◆・Actuator 5, 6. 7...Pressure gauge 8...Flow meter 10◆・◆◆...Valve controller

Claims (2)

[Claims] (1) Measure and feed back the actual flow rate relative to the command flow rate to the valve, and calculate the flow rate deviation between the command flow rate and the measured flow rate by P
In a valve flow rate control device that outputs a command signal through ID control (including P control, PI control, and PD control) and drives the valve, a device that measures fluid pressure is added to the inlet and outlet of the valve. Flow rate control of a valve, characterized in that the deviation signal between the command flow rate and the measured flow rate or the command signal obtained by PID control of the deviation signal is multiplied by the reciprocal of the square root of the difference between the inlet pressure and the outlet pressure. Device. (2) Adding a device to calculate the opening area of the valve in place of the fluid pressure measuring device installed at the inlet and outlet of the valve,
Instead of the reciprocal of the square machine of the difference between the inlet pressure and the outlet pressure, the quotient obtained by dividing the opening area by the measured flow rate is used as the deviation signal between the command flow rate and the measured flow rate, or the command signal obtained by PID control of the deviation signal. 2. The valve flow rate control device according to claim 1, wherein said multiplication is performed.