JPH10159743A - Hydraulic control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make hydraulic control with stable operation. SOLUTION: A hydraulic control system is composed of a hydraulic pump 3, a servo motor 2 coupled directly with the input shaft of the pump 3 and giving rotation to the shaft, and a servo motor drive control device 11 which make drive control of the servo motor and controls the liquid pressure generated by the pump 3, wherein further an oscillation signal generator 10 is furnished, and the servo motor drive control device 11 is equipped with an adder to add the oscillation signal generated by the generator 10 to the signal about the control input in accordance with the deviation of the pressure feedback value of liquid pressure given by the pump 3 from a specified pressure command value, and this oscillation signal is added to the signal about the control input.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an input shaft of a hydraulic pump which performs inflow and outflow of liquid by rotating a shaft provided with power as rotation, by using a rotary shaft of a servomotor directly connected to the shaft. The present invention relates to a hydraulic control system that controls the pressure (torque) of hydraulic fluid transferred by a hydraulic pump by rotating the servomotor and controlling the drive of the servomotor by a servomotor drive control device.

[0002]

2. Description of the Related Art As a conventional hydraulic pressure control system using a servo motor drive control device for driving a hydraulic pump of this type, there is, for example, the one shown in FIG. In FIG. 5, a pressure (torque) command value and a speed (rotation speed) command value are input to a servo motor drive control device 1 to drive and control a servo motor 2, and a hydraulic pressure directly connected to a rotation shaft of the servo motor 2. In order to control the pressure and flow rate of the hydraulic fluid transferred by the pump 3, the servomotor 2 detects the rotational angular velocity (rotation speed), and the hydraulic pump 3 detects the hydraulic pressure (torque) from the hydraulic fluid generating side. Are fed back to the servo motor drive control device 1.

FIG. 6 is a block diagram showing this hydraulic pressure control system including a configuration example of a servo motor drive control device. The servo motor drive control device 1 in the hydraulic control system shown in FIG. 6 inputs the pressure (torque) command value and the pressure (torque) feedback value to the subtractor 4 and compensates the deviation signal by the compensation circuit 5. The amount multiplied is the manipulated variable. By inputting the operation amount to an inverter 6 including a servo motor sub-control circuit, the servo motor 2 is driven and controlled, and a hydraulic pump 3 directly connected to its rotary shaft is controlled.
Is controlled so that the generated hydraulic pressure coincides with the pressure command value. Reference numeral 7 denotes a load device such as an actuator that is operated by the hydraulic fluid transferred by the hydraulic pump 3.

[0004]

However, the conventional hydraulic control system using such a servo motor drive control device for driving a hydraulic pump has the following problems. When performing hydraulic control for keeping the hydraulic pressure or torque generated from the hydraulic pump 3 constant, when the servo motor 2 is stationary or rotating at a low speed, steady rotation due to dynamic frictional force during rotation of the hydraulic pump 3 is performed. The main problem is that the static torque due to the static friction force at the time of stop is larger than the torque, and the following problem occurs.

In the state where the hydraulic pump 3 is stopped, the rotating shaft of the hydraulic pump 3 does not start rotating even if the servo motor 2 generates a torque equal to the steady rotation torque.
Therefore, in order to change the hydraulic pump 3 from the stopped state to the rotating state, it is necessary to generate a torque exceeding the static torque from the servomotor 2.

[0006] The hydraulic pump 3
When it starts to rotate on the axis of rotation, the hydraulic pump 3
The torque required to drive the motor decreases to a steady rotation torque. At this time, the energy corresponding to the torque reduction is accelerated by the rotating body of the servomotor 2 and the hydraulic pump 3 and is converted into kinetic energy, which is stopped again by a certain rotation.

[0007] Due to the occurrence of the stick-slip phenomenon which repeats this, the hydraulic pressure fluctuates at a low frequency during the hydraulic pressure control. The present invention has been made in view of such a conventional problem. In the hydraulic control system using the servo motor drive control device for driving the hydraulic pump as described above, stable hydraulic pressure control is performed. The purpose is to be able to do so.

[0008]

SUMMARY OF THE INVENTION The present invention provides a hydraulic pump for transferring a hydraulic fluid having a flow rate corresponding to the rotation speed by applying rotation to an input shaft, and a hydraulic pump directly connected to the input shaft of the hydraulic pump. A hydraulic motor control system comprising: a servomotor for rotating the shaft; and a servomotor drive control device for controlling the pressure of the hydraulic pressure generated by the hydraulic pump by controlling the servomotor. In order to achieve the object, an oscillation signal generator is provided, and the servo motor drive control device is provided with a signal of an operation amount corresponding to a deviation between a pressure command value and a pressure feedback value of a hydraulic pressure generated by the hydraulic pump. And an adder for adding the oscillation signal generated by the oscillation signal generator.

As described above, by adding an oscillation signal of an appropriate frequency and amplitude to the signal of the operation amount of the servo motor drive control device, it is possible to prevent the rotating body of the hydraulic pump from completely stopping and to avoid a static friction state. it can. by this,
Fluctuations in the pressure of the hydraulic fluid transferred by the hydraulic pump can be reduced, and stable hydraulic pressure control can be performed.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a hydraulic control system showing one embodiment of the present invention, and FIG. 2 is a block diagram showing a configuration of a servo motor drive control device 11 together with signals. In these drawings, the same parts as those in FIGS. 5 and 6 are denoted by the same reference numerals, and the description thereof will be omitted.

The hydraulic pressure control system shown in FIG. 1 is different from the conventional hydraulic pressure control system shown in FIG. 6 in that an oscillation signal generator 10 is provided and the oscillation signal is given to a servo motor drive control device 11. , The operation amount.

The servo motor drive controller 11 shown in FIG. 2 inputs the pressure (torque) command value and the pressure (torque) feedback value to the subtractor 4, and compensates for the deviation signal by the compensation circuit 5, The operation amount a, which is the output signal of the compensation circuit 5, is input to the adder 12, where the oscillation signal from the oscillation signal generator 10 is added to obtain the operation amount b. The operation amount b is input to the inverter 6 including the servo motor sub-control circuit, and the drive of the servo motor 2 is controlled.

As described above, in the conventional servo motor drive control device 1 shown in FIG. 6, the operation amount output from the compensation circuit 5 is directly controlled by the inverter 6 including the servo motor sub-control circuit.
In contrast, in the servo motor drive control device 11 according to the present invention, the operation amount b obtained by adding the oscillation signal to the output signal of the compensation circuit 5 becomes the input of the inverter 6 including the servo motor sub-control circuit. As a result, pressure fluctuations during hydraulic control can be reduced.

FIG. 3 shows the waveforms of the signal of the operation amount a output from the compensation circuit 5, the oscillation signal output from the oscillation signal generator 10, and the signal of the operation amount b obtained by adding them. The oscillation signal is a signal of a waveform such as a sine wave, a triangular wave, and a rectangular wave having a constant period and a constant amplitude.

FIG. 4 is a block diagram of a servo motor drive control device in a hydraulic control system showing another embodiment of the present invention. As in the servo motor drive control device 21 shown in FIG. 4, the oscillation signal output from the oscillation signal generator 10 is input to the inverter 6 including the servo motor sub-control circuit, and is added to the servo motor drive signal. With this, the same effect as in the above-described embodiment can be obtained.

The control circuit of the servo motor drive control device of each of the above-described embodiments can be constituted by hardware or software, or by a combination of hardware and software.

[0017]

As described above, according to the hydraulic control system of the present invention, the hydraulic pressure generated by the hydraulic pump and the torque generated by the servomotor, particularly the instability generated at the time of standstill and low rotation. Thus, pressure fluctuations during hydraulic pressure control can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of a hydraulic control system showing an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration example of a servo motor drive control device 11 in FIG. 1 together with signals.

FIG. 3 is a waveform diagram showing a relationship between an operation amount a, an oscillation signal, and an operation amount b obtained by adding them in FIG. 2;

FIG. 4 is a block diagram of a servo motor drive control device in a hydraulic control system showing another embodiment of the present invention.

FIG. 5 is a block diagram showing an example of a hydraulic control system using a conventional servo motor controller for driving a hydraulic pump.

FIG. 6 is a block diagram including a configuration example of the servo motor drive control device 1.

[Explanation of symbols]

 1, 11, 21: Servo motor drive control device 2: Servo motor 3: Hydraulic pump 4: Subtractor 5: Compensation circuit 6: Inverter including servo motor sub-control circuit 7: Load device 10: Oscillation signal generator 12: Adder

Claims (1)

[Claims] A hydraulic pump for transferring a hydraulic fluid having a flow rate corresponding to a rotation speed of the input shaft by rotating the input shaft;
A servo motor directly connected to the input shaft of the hydraulic pump to rotate the shaft, and a servo motor drive control device that drives and controls the servo motor to control the pressure of the hydraulic pressure generated by the hydraulic pump. An oscillation signal generator is provided, and an operation signal corresponding to a deviation between a pressure command value and a pressure feedback value of a hydraulic pressure generated by the hydraulic pump is provided to the servo motor drive control device. A hydraulic pressure control system, further comprising an adder for adding an oscillation signal generated by the oscillation signal generator.