JP2020155065A - Liquid pressure system control device - Google Patents

Abstract

To provide a liquid pressure system control device that is able to execute highly accurate, stable positional control for mechanical load in a liquid pressure system that operates the mechanical load by means of the pressure of a hydraulic fluid.SOLUTION: A liquid pressure system control device 100 operates a cylinder 23, serving as an actuator, by means of the pressure of a hydraulic fluid by driving a pump 20 through control of a servo motor 24. The liquid pressure system control device 100 comprises: a position control unit 2 that, on the basis of a position command 7 for the actuator, a position detection value 10 that is a detection result of the position of the actuator, and a control gain 12, causes the position command 7 to follow the position detection value 10 by generating a pressure command 8 for adjustment of the pressure; and a gain adjustment unit 6 that identifies the characteristic of transmission from the pressure command 8 to the operating speed of the actuator on the basis of a command value for the pressure in an operation for identifying the characteristic of the transmission and the speed value of the operating speed of the actuator, and adjusts the control gain 12 on the basis of the characteristic of the transmission.SELECTED DRAWING: Figure 1

Description

The present invention relates to a hydraulic system control device that operates a mechanical load by using the pressure of a hydraulic fluid sent from a pump under the control of a servomotor.

In industrial machines such as various molding machines or press machines, hydraulic actuators that operate the mechanical load by the pressure of the hydraulic fluid may be used. Further, in a hydraulic system which is a system for operating a hydraulic actuator, a servomotor may be used as a power source of a pump for delivering a hydraulic fluid.

Patent Document 1 discloses that in a hydraulic system having a servomotor which is an operating source of a hydraulic pump, the discharge pressure of the hydraulic pump is controlled by controlling the rotation speed of the servomotor.

JP-A-2007-160356

In a conventional control device that controls a hydraulic system as disclosed in Patent Document 1, a position command, a detection value of the actuator position, and a control gain are used in order to make the position command of the actuator follow the position command of the actuator. A pressure command may be generated based on. However, in the conventional control device, the control gain may be determined based on the experience of the operator of the hydraulic system, so that it may be difficult to control the position of the actuator with high accuracy. In addition, since the mode of operation of the actuator differs depending on each industrial machine, it has been difficult to adjust the control gain according to the control of each hydraulic system with the conventional control device. Therefore, according to the control of the hydraulic system by the conventional control device, there is a problem that it is difficult to control the position of the mechanical load with high accuracy and stability.

The present invention has been made in view of the above, and in a hydraulic system in which a mechanical load is operated by the pressure of a hydraulic fluid, a hydraulic system control device capable of highly accurate and stable position control of a mechanical load is provided. The purpose is to get.

In order to solve the above-mentioned problems and achieve the object, the hydraulic system control device according to the present invention drives the pump by the control of the servomotor and operates the actuator by the pressure of the hydraulic fluid sent from the pump. The mechanical load is operated by the power transmitted from. The hydraulic pressure system control device according to the present invention generates a position command for adjusting the pressure based on the position command for the actuator, the position detection value which is the detection result of the position of the actuator, and the control gain. The position control unit that controls to follow the position detection value, the transmission characteristic from the pressure command to the operating speed of the actuator, the command value of the pressure in the operation for identifying the transmission characteristic, and the speed value of the operating speed of the actuator. It is provided with a gain adjusting unit that identifies the group and adjusts the control gain based on the transmission characteristics.

According to the present invention, in a hydraulic system in which a mechanical load is operated by the pressure of a hydraulic fluid, there is an effect that highly accurate and stable position control of the mechanical load becomes possible.

The figure which shows the hydraulic pressure system control apparatus which concerns on Embodiment 1 of this invention, and the hydraulic pressure system controlled by the hydraulic pressure system control apparatus. The figure which shows an example of the position control part which the hydraulic pressure system control device shown in FIG. A flowchart illustrating identification of transmission characteristics and adjustment of control gain by the hydraulic system control device shown in FIG. The figure which shows the 1st example of the identification pressure command generated in the hydraulic pressure system control apparatus shown in FIG. The figure which shows the 2nd example of the identification pressure command generated in the hydraulic pressure system control apparatus shown in FIG. The figure which shows the transition of the pressure command for identification and the operation speed of an actuator shown in FIG. The figure which shows the transition of the pressure command for identification and the operation speed of an actuator shown in FIG. The figure explaining an example of the calculation of the control gain by the gain adjustment part which has the hydraulic pressure system control device shown in FIG. The first figure which shows an example of the hardware configuration of the hydraulic system control device which concerns on Embodiment 1. FIG. 2 shows another example of the hardware configuration of the hydraulic system control device according to the first embodiment. The figure which shows the hydraulic pressure system control apparatus which concerns on Embodiment 2 of this invention, and the hydraulic pressure system controlled by the hydraulic pressure system control apparatus. A flowchart illustrating an operation procedure for storing a table showing the relationship between the temperature of the hydraulic fluid and the control gain in the hydraulic system control device shown in FIG. The figure which shows an example of the table stored in the storage part of the hydraulic pressure system control device shown in FIG. The figure which shows the hydraulic pressure system control apparatus which concerns on Embodiment 3 of this invention, and the hydraulic pressure system controlled by the hydraulic pressure system control apparatus. A flowchart illustrating an operation procedure for storing a table showing the relationship between the load amount and the control gain in the hydraulic system control device shown in FIG.

Hereinafter, the hydraulic system control device according to the embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment.

Embodiment 1.
FIG. 1 is a diagram showing a hydraulic system control device 100 according to the first embodiment of the present invention and a hydraulic pressure system 200 controlled by the hydraulic system control device 100. The hydraulic system 200 has an actuator that operates under the pressure of oil, which is a hydraulic fluid. Although not shown, in industrial machines, actuators are usually fitted with a mechanical load. The mechanical load operates by receiving the power transmitted from the actuator. For example, in a molding machine, which is one of industrial machines, a machine load is a mechanism for press-fitting a material into a mold. The mechanical load that operates by receiving power from the hydraulic system 200 may be a mechanical load of an industrial machine such as a molding machine and a press machine, or a mechanical load of a machine such as an elevator.

The hydraulic system 200 includes a pump 20 that sends out a hydraulic fluid, a tank 21 that stores the hydraulic fluid, a pipe 22 through which the hydraulic fluid flows, and a cylinder 23 that is an actuator. The pipe 22 connects the pump 20, the tank 21, and the cylinder 23. The pump 20, the tank 21, the pipe 22, and the cylinder 23 form a hydraulic circuit, which is a circuit through which the hydraulic fluid flows.

The cylinder 23 has a piston 23a that operates under the pressure of the hydraulic fluid. The pump 20 controls the flow of the hydraulic fluid in the direction in which the hydraulic fluid flows into the cylinder 23 and the flow of the hydraulic fluid in the direction opposite to the direction in which the hydraulic fluid flows out of the cylinder 23. It is a switchable double-rotation pump. The position detector 27 detects the position of the piston 23a and outputs the position detection value 10 which is the detection result to the hydraulic system control device 100.

The hydraulic system 200 includes a servomotor 24 that is a power source of the pump 20 and a servo amplifier 25 that operates the servomotor 24 in accordance with the pressure command 9. The pressure detector 26 detects the pressure of the hydraulic fluid flowing through the pipe 22, and outputs the pressure detection value 28, which is the detection result, to the servo amplifier 25. The servo amplifier 25 adjusts the current value of the current 29 supplied to the servomotor 24 so that the pressure detection value 28 follows the pressure command value which is the pressure command 9. The servomotor 24 generates a torque 30 by receiving a current 29 and driving the servomotor 24, and applies the torque 30 to the pump 20.

The hydraulic pressure system 200 controls the pressure of the hydraulic fluid by operating the pump 20 using the servomotor 24 and feeding back the pressure of the hydraulic fluid sent from the pump 20 to change the rotation speed of the pump 20. Such a control method is called a servo pump method. By adopting the servo pump method, the hydraulic system 200 can stop the pump 20 and the servo motor 24 when the actuator is stopped. For this reason, the hydraulic pressure system 200 reduces energy consumption and makes noise as compared with a system that constantly rotates the hydraulic pump at the maximum speed to allow the hydraulic fluid to flow at the maximum flow rate and controls the flow rate through the hydraulic valve. Can be reduced. Further, the hydraulic system 200 is also characterized in that by using the servomotor 24 as the power source of the pump 20, the responsiveness of the position control is higher than that of the system adopting the control method other than the servo pump method.

The hydraulic system control device 100 controls the position of the mechanical load by adjusting the pressure of the hydraulic fluid delivered from the pump 20. FIG. 1 shows a functional configuration of the hydraulic system control device 100. The hydraulic system control device 100 includes a position command generation unit 1 that generates a position command 7, a position control unit 2 that generates a pressure command 8, and an identification pressure command generation unit 4 that generates an identification pressure command 13. Have. Further, the hydraulic system control device 100 adjusts a switching unit 3 for switching between the output of the pressure command 8 and the output of the identification pressure command 13, a speed detection unit 5 for detecting the operating speed of the piston 23a, and a control gain 12. It has a gain adjusting unit 6 to perform.

The position command generation unit 1 outputs a position command 7 that serves as a reference signal for the mechanical load or the position where the cylinder 23 should operate. As a specific example of the position command 7, the position command 7 whose position changes stepwise, ramp-like, or S-shaped during the movement from the current position to the desired position at the time when the mechanical load and the cylinder 23 are desired to be operated. Can be mentioned. Step-by-step position change means that the position changes discretely from the current position at a certain timing, so that the position changes stepwise from the current position to the desired position and stays at the desired position. Point to that. Ramp-like position change means that the position changes with a certain inclination and stays at the desired position from the current position until the desired position is reached. The change in the position in an S-shape means that the position changes in an S-shaped curve from the current position until the desired position is reached and stays at the desired position. In addition, the transition of the position means the transition of the position when the relationship between the time and the position is represented by a graph. The position control unit 2 compares the position command 7 and the position detection value 10 every moment, for example, every predetermined control sampling cycle, and outputs a pressure command 8 every moment based on the control gain 12.

FIG. 2 is a diagram showing an example of the position control unit 2 included in the hydraulic system control device 100 shown in FIG. The position control unit 2 obtains the pressure command 8 which is the pressure command value by multiplying the difference between the position command 7 and the position detection value 10 by Kp which is the value of the control gain 12. The position control unit 2 generates a pressure command 8 for making the position detection value 10 follow the position command 7. The position control unit 2 outputs the obtained pressure command 8.

A position detection value 10 is input to the speed detection unit 5 shown in FIG. The speed detection unit 5 calculates the operating speed of the piston 23a by the differential processing or the difference processing of the position detection value 10. The speed detection unit 5 outputs the calculated speed value 11 to the gain adjustment unit 6.

A speed value 11 and a pressure command 9 which is an output from the switching unit 3 are input to the gain adjusting unit 6. The gain adjusting unit 6 adjusts the control gain 12 based on the transmission characteristic from the pressure command 8 to the operating speed of the piston 23a.

The identification pressure command generation unit 4 generates an identification pressure command 13 which is a pressure command for identifying the transmission characteristic, and outputs the generated identification pressure command 13 to the switching unit 3. The identification pressure command 13 is a pressure command value when the hydraulic pressure system control device 100 performs an operation for identifying the transmission characteristic. A pressure command 8 and an identification pressure command 13 are input to the switching unit 3. The switching unit 3 outputs one of the pressure command 8 and the identification pressure command 13. Further, the switching unit 3 switches between the output of the pressure command 8 and the output of the identification pressure command 13. The switching unit 3 outputs the identification pressure command 13 during the operation for identification. The switching unit 3 outputs the pressure command 8 at the time of an operation other than the operation for identification. The pressure command 9 is a command output from the switching unit 3, and is one of the pressure command 8 and the identification pressure command 13. The switching unit 3 outputs the pressure command 9 to the servo amplifier 25.

The hydraulic pressure system 200 may be provided with a check valve in the pipe 22. In such a hydraulic system 200, it is common to close the check valve when holding the position of the mechanical load for a long period of time, particularly when it is desired to hold the position of the mechanical load when an external force is applied to the mechanical load. is there. When the check valve is closed, the flow of the hydraulic fluid is blocked by closing the pipe 22. In this case, the hydraulic system 200 can maintain the position of the cylinder 23 without generating torque in the servomotor 24 to resist the external force. When the check valve is closed, the hydraulic fluid cannot circulate in the pipe 22. When the hydraulic system 200 is provided with a check valve, the hydraulic system control device 100 according to the first embodiment controls the position of the cylinder 23 with the check valve open. Further, the hydraulic system control device 100 operates for identifying the transmission characteristic in a state where the check valve is open. That is, the gain adjusting unit 6 performs an operation for identifying the transmission characteristic in a state where the flow of the hydraulic fluid is not blocked. As a result, the hydraulic system control device 100 identifies the transmission characteristics when the hydraulic fluid can flow in the pipe 22 and when the operation for identifying the transmission characteristics is possible.

If the control gain 12 is not properly adjusted in the hydraulic system control device 100, vibration or overshoot in the actuator may affect the accuracy of the position control of the mechanical load. The decrease in the accuracy of position control causes deterioration of quality in products produced by industrial machines and deterioration of production efficiency of industrial machines. The hydraulic system control device 100 can appropriately adjust the control gain 12 by identifying the transmission characteristic and adjusting the control gain 12 based on the transmission characteristic in the gain adjusting unit 6.

Next, identification of the transmission characteristic and adjustment of the control gain 12 will be described. FIG. 3 is a flowchart illustrating identification of transmission characteristics and adjustment of control gain 12 by the hydraulic system control device 100 shown in FIG.

When the hydraulic system control device 100 performs normal pressure control, the switching unit 3 is in a state of outputting a pressure command 8. As a result, the hydraulic system control device 100 adjusts the pressure of the hydraulic fluid in a closed loop in which the function of the position control unit 2 is effective. When the hydraulic system control device 100 performs an operation for identifying the transmission characteristic, the switching unit 3 switches from the state of outputting the pressure command 8 to the state of outputting the identification pressure command 13. By switching the switching unit 3, the hydraulic pressure system control device 100 adjusts the pressure of the working fluid in a state in which the position control loop is temporarily disabled, that is, in an open loop state in which the function of the position control unit 2 is disabled. ..

In step S1, the identification pressure command generation unit 4 outputs the identification pressure command 13 in the open loop state. The hydraulic system control device 100 outputs the pressure command 9 which is the identification pressure command 13 to the servo amplifier 25.

The hydraulic system control device 100 operates the pump 20 by the output of the identification pressure command 13, and obtains a position detection value 10 according to the operation of the pump 20. The gain adjusting unit 6 identifies the transmission characteristic based on the velocity value 11 corresponding to the position detection value 10 and the identification pressure command 13. The signal of the identification pressure command 13 is zero at the start and end of a certain time, and becomes non-zero at the certain time. The command value of the pressure in the operation for identifying the transmission characteristic is zero at the start and end of a certain time, and becomes a non-zero value at a certain time.

Here, a specific example of the identification pressure command 13 will be described. FIG. 4 is a diagram showing a first example of the identification pressure command 13 generated by the hydraulic system control device 100 shown in FIG. FIG. 5 is a diagram showing a second example of the identification pressure command 13 generated by the hydraulic pressure system control device 100 shown in FIG. In FIG. 4, the transition of the signal which is the identification pressure command 13 is shown on the time axis.

In the case of the first example shown in FIG. 4, the identification pressure command 13 changes from an initial value of zero to a certain value at the start of time T, and is maintained at a constant value at time T. The identification pressure command 13 returns to the initial value of zero at the end of time T. In the first example, the signal waveform is rectangular. In the first example, the command value of the pressure according to the identification pressure command 13 is zero at the start and end of the time T, and becomes a constant value at the time T.

In the case of the second example shown in FIG. 5, the identification pressure command 13 is increased from the initial value of zero by the start of time T. The identification pressure command 13 decreases after reaching a certain value, and returns to the initial value of zero at the end of time T. In the second example, the signal waveform is triangular. In the second example, the identification pressure command 13 continuously increases from zero and then continuously decreases from the peak to zero. The command value of the pressure according to the identification pressure command 13 continuously increases gradually from zero, and then gradually decreases from the peak to zero.

The hydraulic system 200 operates the piston 23a by driving the servomotor 24 in accordance with the pressure command 9 which is the identification pressure command 13. The speed detection unit 5 outputs the speed value 11 based on the position detection value 10 to the gain adjustment unit 6. The speed value 11 from the speed detection unit 5 and the pressure command 9 from the switching unit 3 are input to the gain adjusting unit 6.

In step S2, the gain adjusting unit 6 stores the pressure command 9 and the speed value 11 which are the pressure command values. The gain adjusting unit 6 stores the time-series data of the pressure command 9 and the speed value 11 in time synchronization.

In step S3, the gain adjusting unit 6 identifies the transmission characteristic based on the stored pressure command 9 and the velocity value 11. The transfer function representing the transfer characteristic is composed of a gain and a delay element. The transfer function representing the transfer characteristic from P, which is the pressure command 9, to V, which is the speed of the piston 23a, is expressed by the following equation (1).
V = K ・ exp (−L ・ s) ・ P ・ ・ ・ (1)

In the equation (1), K is a parameter indicating a gain element in the transmission characteristic, and L is a parameter indicating a delay element in the transmission characteristic. s is a Laplace operator. The formula (1) means that the signal is delayed by the time corresponding to L by exp (−L · s). The gain adjusting unit 6 can uniquely identify the transmission characteristics by determining K and L. In step S3, the gain adjusting unit 6 calculates K and L based on the stored pressure command 9 and the speed value 11.

Here, a method of calculating K and L by the gain adjusting unit 6 will be described. A roughly proportional relationship holds between the commanded pressure and the speed of the piston 23a. Further, when the transition of the speed of the piston 23a is represented on the time axis, the waveform showing the transition of the speed is a waveform having a delay with respect to the signal waveform of the pressure command 9.

FIG. 6 is a diagram showing the transition of the identification pressure command 13 shown in FIG. 4 and the operating speed of the actuator. The timing at which the speed of the piston 23a rises from the initial value of zero is a timing delayed from the rise of the signal of the pressure command 9. Based on the stored pressure command 9 and the speed value 11, the gain adjusting unit 6 obtains L, which is the delay time of the speed rise of the piston 23a from the rise of the signal of the pressure command 9.

Assuming that the value of the identification pressure command 13 from the rise to the fall of the pressure command 9 is A and the value of the speed of the piston 23a from the rise to the fall is B, K = B / A due to the above proportional relationship. The relationship holds. The gain adjusting unit 6 obtains A and B from the stored pressure command 9 and the speed value 11, and obtains K by dividing B by A.

FIG. 7 is a diagram showing the transition of the identification pressure command 13 shown in FIG. 5 and the operating speed of the actuator. The timing at which the speed of the piston 23a peaks is a timing delayed from the peak of the pressure command 9 which is the identification pressure command 13. The gain adjusting unit 6 obtains L, which is the delay time of the peak speed of the piston 23a from the peak of the pressure command 9, based on the stored pressure command 9 and the speed value 11.

Assuming that the value at the peak of the pressure command 9 is A and the value at the peak of the speed of the piston 23a is B, the relationship of K = B / A is established by the above-mentioned proportional relationship. The gain adjusting unit 6 obtains A and B from the stored pressure command 9 and the speed value 11, and obtains K by dividing B by A. In this way, the gain adjusting unit 6 calculates K and L based on the transition of the pressure command 9 which is the identification pressure command 13 and the transition of the operating speed of the piston 23a according to the pressure command 9. To do.

In step S4, the gain adjusting unit 6 calculates the control gain 12 based on the transmission characteristics identified in step S3. The gain adjusting unit 6 obtains the control gain 12 from the difference between the value of the command position and the value indicating the position of the actuator based on the open-loop transfer function to the value indicating the position of the actuator.

Here, a method of calculating the control gain 12 by the gain adjusting unit 6 will be described. FIG. 8 is a diagram illustrating an example of calculation of the control gain 12 by the gain adjusting unit 6 included in the hydraulic system control device 100 shown in FIG. FIG. 8 shows a block that is a component of the open-loop transfer function for the open-loop transfer function from the difference 31 between the value of the position command 7 and the value indicating the position of the piston 23a to the value 32 indicating the position of the piston 23a. Is shown. The open-loop transfer function is composed of the product of Kp, which is a control gain 12, the transfer function obtained in step S3, and 1 / s, which is an integrator. The integrator 1 / s is a transfer function from the operating speed of the piston 23a to the position of the piston 23a.

The gain adjusting unit 6 calculates Kp for which the gain margin of the open-loop transfer function is a gain margin that is theoretically valid for automatic control, for example, a gain margin of 10 dB or more, or the phase margin of the open-loop transfer function. However, a phase margin that is theoretically valid for automatic control, for example, Kp with a phase margin of 30 degrees or more is calculated.

In step S5, the gain adjusting unit 6 outputs the control gain 12 calculated in step S4 to the position control unit 2. The switching unit 3 switches from the state of outputting the identification pressure command 13 to the state of outputting the pressure command 8. By switching the switching unit 3, the hydraulic system control device 100 is in a state where the position control can be performed in a closed loop in which the function of the position control unit 2 is effective. As a result, the hydraulic system control device 100 ends the operation shown in FIG.

Here, in the first embodiment, the effect of identifying the transmission characteristics including the gain element and the delay element will be described. The servo amplifier 25 supplies a current 29 to the servomotor 24 so as to follow the given pressure command 9. By applying the torque 30 by the servomotor 24, the pump 20 applies pressure to the hydraulic fluid of the hydraulic circuit. In the hydraulic circuit, according to Pascal's principle, a force for operating the piston 23a is generated from the cylinder 23 according to the pressure received by the hydraulic fluid and the cross-sectional area of the piston 23a. This force accelerates the operation of the piston 23a.

The piston 23a accelerates due to the pressure of the hydraulic fluid, but the speed does not increase infinitely. When the hydraulic fluid flows through the hydraulic circuit, the piston 23a receives friction, which is the flow resistance of the hydraulic fluid. When the piston 23a is accelerated from the stopped state by a force of a certain magnitude, the piston 23a reaches a certain speed except when the shut valve is closed and the pipe 22 is blocked to block the flow of the hydraulic fluid. Sometimes the force that operates the piston 23a and the frictional force of the hydraulic fluid are balanced. The acceleration of the piston 23a due to such a force is said to be acceleration until the frictional force and the force generated in the piston 23a are balanced. In this way, the speed of the piston 23a is determined according to the pressure generated by the pump 20.

Most of the flow resistance of the hydraulic circuit is viscous friction proportional to the operating speed generated when the piston 23a passes through the hydraulic fluid. Therefore, a proportional relationship is generally established between the operating speed of the piston 23a and the pressure of the hydraulic fluid. This proportionality constant corresponds to K, which is a constant in the transfer characteristic. The hydraulic system 200 causes a certain delay from the time when the servo amplifier 25 receives the pressure command 9 until the operating speed of the piston 23a becomes the speed according to the pressure command 9. This delay is due to the delay due to the feedback processing and the time from the start of applying the pressure to the hydraulic fluid until the pressing force and the frictional force are balanced. This delay corresponds to L in the transmission characteristics.

From the above description, the hydraulic system 200 adopting the servo pump method has a physical property that the operating speed of the piston 23a changes in proportion to the pressure command 9 after a delay time from the time when the pressure command 9 is received. Have. As shown in the above equation (1), the gain adjusting unit 6 uses the transmission characteristics including the gain element and the delay element, except when the shut valve is closed and the flow of the working fluid is blocked. , It becomes possible to identify the transfer characteristics suitable for the physical properties of the hydraulic system 200.

The ARX (Auto Regressive eXogenous) model, which is one of the common models used in the identification of transfer characteristics, has a large number of parameters as compared with the model shown in the above equation (1). By using a model in which only the gain element and the delay element based on the physical properties are used as parameters, the gain adjusting unit 6 can improve the accuracy of identification as compared with the case of using the above ARX model. Further, the gain adjusting unit 6 can reduce the load of arithmetic processing when calculating the control gain 12 by reducing the number of parameters as compared with the case of using the above ARX model.

The delay element included in the transmission characteristic in the first embodiment becomes a factor that delays the phase characteristic among the frequency characteristics in the feedback control. In the high frequency band, the lag element changes the phase characteristic by 180 degrees or more. When considering feedback control with respect to the transmission characteristic in which the phase characteristic rotates 180 degrees, if the control gain 12 is made too large, the stability of the position control loop deteriorates, and vibration or overshoot occurs. By adopting the transmission characteristic including the delay element, the control gain 12 can be adjusted in consideration of the occurrence of vibration and overshoot. On the contrary, when the change of the phase characteristic is a change of less than 180 degrees, for example, the transmission characteristic of the first-order lag element, the transmission characteristic does not make the position control loop unstable, so that vibration or overshoot is prevented. It is not possible to obtain an appropriate control gain 12.

The hydraulic system control device 100 according to the first embodiment stabilizes the control loop by adjusting the control gain 12 by using the transmission characteristic including the delay element as shown in the above equation (1). It is possible to obtain a control gain 12 that can reduce the occurrence of vibration and overshoot.

Next, the effect of using the signal as shown in FIGS. 4 and 5 as the identification pressure command 13 in the first embodiment will be described. The identification pressure command 13 shown in FIGS. 4 and 5 is a signal having a value other than zero at a certain time T and being zero at the start and end of the time T.

As described above, the hydraulic pressure system 200 has a physical property that the operating speed of the piston 23a changes in proportion to the pressure command 9 after a delay time from the time when the pressure command 9 is received. The transition of the speed of the piston 23a is such that the initial value is zero, the value becomes non-zero in a certain period of time, and then the speed returns to zero again. Since the value indicating the position of the piston 23a is the result of integrating the speed of such a transition, it does not become infinitely large, but is a value indicating a specific position. The movement of the piston 23a is the movement to such a specific position. Thereby, the hydraulic system 200 can avoid the situation where the piston 23a continues to move beyond the permissible range in the operation for identifying the transmission characteristic. Further, since the mechanical load does not continue to move beyond the permissible range, the hydraulic system 200 can avoid a situation in which the mechanism comes into contact with the stroke end.

The identification pressure command 13 is not limited to the signals shown in FIGS. 4 and 5. The identification pressure command 13 shown in FIG. 5 continuously gradually increases from zero along a straight line, and continuously decreases along a straight line from reaching a peak to zero. The identification pressure command 13 may be continuously increasing along a curve and then continuously decreasing. As the curve, a curve such as a curve of a trigonometric function graph or a curve of an exponential function graph can be used.

In the hydraulic system 200, as shown in the above equation (1), a proportional relationship is established between the commanded pressure and the operating speed of the piston 23a. By using a signal for the identification pressure command 13 that continuously increases from zero and then continuously decreases, the operating speed of the piston 23a also changes in the same manner as the identification pressure command 13. Thereby, the hydraulic system 200 can prevent the sudden operation of the actuator from occurring in the operation for identifying the transmission characteristic. The hydraulic system 200 prevents the actuator from suddenly moving in both the case where the identification pressure command 13 changes along a straight line and the case where the identification pressure command 13 changes along a curve. be able to.

The position control unit 2 generates the pressure command 8 by multiplying the difference between the position command 7 and the position detection value 10 by the control gain 12. The hydraulic system control device 100 adopts a control method based on P (Proportional) control, which is proportional control. The control method adopted by the hydraulic system control device 100 may be a control method other than proportional control. The control methods are PI (Proportional Integral) control, which is proportional and integral control, PID (Proportional Integral Differential) control, which is proportional, integral and differential control, and IP (Integral Proportional) control, which is integral and proportional control. It may be any of.

The hydraulic system control device 100 is not limited to the one that switches the output of the pressure command 8 and the output of the identification pressure command 13 by the switching unit 3. The hydraulic system control device 100 may not be provided with the switching unit 3 and may leave the operation of the position control unit 2 enabled even when identifying the transmission characteristics. In this case, the hydraulic system control device 100 applies the position command 7 generated by the position command generation unit 1 to the position control unit 2, and sets the pressure command 8 and the speed of the cylinder 23 in time during the position control operation. It is stored synchronously, and these are used to identify the transmission characteristic from the pressure command 8 to the operating speed of the cylinder 23. At this time, the value of the control gain 12 input to the position control unit 2 is set to a very small value. This makes it possible to identify the transfer characteristics without causing vibration or overshoot, although the responsiveness is considerably reduced. A position command 7 is given from the position command generation unit 1 to the position control unit 2, and the pressure command 8 generated at this time and the operating speed of the cylinder 23 are stored in time synchronization, and the pressure command 8 is stored based on the stored data. The control gain 12 output to the position control unit 2 may be adjusted based on the identification of the transmission characteristic to the operating speed of the cylinder 23.

Next, the hardware configuration of the hydraulic system control device 100 will be described. The function of the hydraulic system control device 100 is realized by using a processing circuit. The processing circuit is dedicated hardware mounted on the hydraulic system control device 100. The processing circuit may be a processor that executes a program stored in memory.

FIG. 9 is a first diagram showing an example of the hardware configuration of the hydraulic system control device 100 according to the first embodiment. FIG. 9 shows a hardware configuration when the function of the hydraulic system control device 100 is realized by using dedicated hardware. The hydraulic system control device 100 includes a processing circuit 61 that executes various processes, an external storage device 62 that stores various information, and an input / output interface 63 that is a connection interface between an external device of the hydraulic system control device 100. To be equipped with. The input / output interface 63 may have an input device for information input such as a keyboard or a pointing device, or an output device for information output such as a display. Each part of the hydraulic system control device 100 shown in FIG. 9 is connected to each other via a bus.

The processing circuit 61, which is dedicated hardware, is a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or these. It is a combination. Each function of the position command generation unit 1, the position control unit 2, the switching unit 3, the identification pressure command generation unit 4, the speed detection unit 5, and the gain adjustment unit 6 shown in FIG. 1 is realized by using the processing circuit 61. .. The external storage device 62 is an HDD (Hard Disk Drive) or an SSD (Solid State Drive).

FIG. 10 is a second diagram showing another example of the hardware configuration of the hydraulic system control device 100 according to the first embodiment. FIG. 10 shows a hardware configuration when the function of the hydraulic system control device 100 is realized by using hardware for executing a program. The processor 64 and the memory 65 are interconnected with the external storage device 62 and the input / output interface 63.

The processor 64 is a CPU (Central Processing Unit), a processing unit, an arithmetic unit, a microprocessor, a microcomputer, or a DSP (Digital Signal Processor). The functions of the position command generation unit 1, the position control unit 2, the switching unit 3, the identification pressure command generation unit 4, the speed detection unit 5, and the gain adjustment unit 6 shown in FIG. 1 are the processor 64 and software, firmware, or It is realized by the combination of software and firmware. The software or firmware is described as a program and stored in the memory 65, which is a built-in memory. The memory 65 is a non-volatile or volatile semiconductor memory, such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory) or EEPROM® (Electrically Erasable). Programmable Read Only Memory).

According to the first embodiment, the hydraulic system control device 100 adjusts the control gain 12 for adjusting the pressure of the hydraulic fluid by the gain adjusting unit 6. The gain adjusting unit 6 stabilizes the control loop by adjusting the control gain 12 based on the transmission characteristic representing the relationship between the operating speed of the actuator and the pressure command 9 which is the identification pressure command 13, thereby stabilizing the control loop and vibrating and overshooting. It is possible to obtain a control gain 12 that can reduce the occurrence of shoots. As a result, the hydraulic system control device 100 has the effect of enabling highly accurate and stable position control of the mechanical load in the hydraulic system 200 in which the mechanical load is operated by the pressure of the hydraulic fluid.

Embodiment 2.
FIG. 11 is a diagram showing a hydraulic system control device 101 according to a second embodiment of the present invention and a hydraulic system 200 controlled by the hydraulic system control device 101. In the second embodiment, the gain adjuster 6 identifies the transfer characteristics associated with the temperature of the hydraulic fluid. In the second embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and the configurations different from those in the first embodiment will be mainly described.

The hydraulic system control device 101 has a storage unit 40 that stores the control gain 12 adjusted by the gain adjustment unit 6. The temperature detector 41 detects the temperature of the hydraulic fluid flowing through the pipe 22. At the time of identification of the transmission characteristic, the temperature detector 41 outputs the temperature value 42, which is the detection result, to the storage unit 40. The gain adjusting unit 6 outputs the control gain 12 to the storage unit 40. The storage unit 40 stores the temperature value 42 and the control gain 12 in association with each other. As a result, the storage unit 40 stores the table in which the temperature of the hydraulic fluid and the control gain 12 are associated with each other.

When the pressure of the hydraulic fluid is adjusted by the pressure command 8, the temperature detector 41 outputs the temperature value 42 to the position control unit 2. The position control unit 2 reads out the control gain 12 corresponding to the input temperature value 42 from the storage unit 40. The position control unit 2 generates a pressure command 8 based on the position command 7 and the read control gain 12.

Next, the memory of the table showing the relationship between the temperature of the hydraulic fluid and the control gain 12 will be described. FIG. 12 is a flowchart illustrating an operation procedure for storing a table showing the relationship between the temperature of the hydraulic fluid and the control gain 12 in the hydraulic system control device 101 shown in FIG.

In step S11, the gain adjusting unit 6 identifies the transmission characteristic at the temperature of the current hydraulic fluid at the start of the operation of storing the table, and calculates the control gain 12. The method of calculating the control gain 12 is the same as that of the first embodiment. In step S12, the storage unit 40 stores the temperature value 42 of the hydraulic fluid and the control gain 12 in association with each other. In step S13, the position control unit 2 reads out the control gain 12 stored in the storage unit 40 in step S12.

In step S14, the hydraulic system control device 101 raises the temperature of the hydraulic fluid to perform position control of the piston 23a. A method of raising the temperature of the hydraulic fluid includes performing an aging operation of the hydraulic pressure system 200. Specifically, the hydraulic system control device 101 continuously executes position control to cause the hydraulic system 200 to be operated for aging. When the aging operation is continued, the temperature of the hydraulic fluid gradually rises due to the friction of the hydraulic fluid in the hydraulic circuit.

In step S15, the position control unit 2 determines whether or not the position control characteristic has deteriorated based on the measurement result of the position control characteristic in the position control in the aging operation. The position control characteristics are measured by measuring the state waveform of the piston 23a or the mechanical load in the position control. The position control unit 2 determines whether or not the position control characteristic has deteriorated depending on whether or not the overshoot or vibration satisfies a predetermined control specification.

When it is determined that the position control characteristics have deteriorated (steps S15, Yes), the hydraulic system control device 101 repeats the procedure from step S11. In step S11, the gain adjusting unit 6 identifies the transmission characteristic at the current temperature of the hydraulic fluid during the aging operation, and calculates the control gain 12.

When it is determined that the position control characteristics have not deteriorated (steps S15 and No), in step S16, the position control unit 2 determines whether or not the temperature of the hydraulic fluid has reached a preset upper limit. The upper limit of temperature is the upper limit of the temperature at which the hydraulic fluid can be used. The upper limit of the temperature may be the upper limit of the temperature of the hydraulic fluid capable of operating the mechanical load.

When it is determined that the temperature of the hydraulic fluid has not reached the upper limit (steps S16, No), the hydraulic system control device 101 repeats the procedure from step S14. When it is determined that the temperature of the hydraulic fluid has reached the upper limit (step S16, Yes), the hydraulic system control device 101 ends the operation according to the procedure shown in FIG. As a result, the hydraulic system control device 101 creates a table showing the relationship between the temperature of the hydraulic fluid and the control gain 12 capable of suppressing deterioration of the position control characteristics.

FIG. 13 is a diagram showing an example of a table stored in the storage unit 40 included in the hydraulic system control device 101 shown in FIG. The table is associated with the temperature of the hydraulic fluid and a control gain 12 capable of suppressing deterioration of the position control characteristics.

The hydraulic system control device 101 creates a table at the time of manufacturing or starting up the mechanical load. When the position control unit 2 adjusts the pressure of the hydraulic fluid by the pressure command 8, the position control unit 2 reads out the relationship between the temperature of the hydraulic fluid and the control gain 12 from the storage unit 40, and the control gain corresponding to the input temperature value 42. Find 12 The position control unit 2 may determine the control gain 12 corresponding to the input temperature value 42 based on the relationship obtained by linear interpolation between the stored temperature value 42 and the control gain 12.

The table is not limited to the table shown in FIG. The table may be one in which the temperature of the hydraulic fluid and the control gain 12 are associated with each preset temperature, for example, every degree. According to the procedure shown in FIG. 12, the table is obtained by gradually increasing the temperature of the hydraulic fluid and calculating the control gain 12 when the position accuracy characteristic deteriorates. In this case, the time required to create the table can be shortened and the capacity of the table can be reduced as compared with the case of creating the table having the association for each set temperature.

The hydraulic system control device 101 has the same hardware configuration as the hydraulic system control device 100 according to the first embodiment. The storage unit 40 is realized by using the external storage device 62 shown in FIGS. 9 and 10.

According to the second embodiment, the hydraulic system control device 101 has the same configuration as the hydraulic system control device 101 according to the first embodiment, so that highly accurate and stable position control of the mechanical load becomes possible. .. Further, the hydraulic system control device 101 identifies the transmission characteristics of the hydraulic fluid at each temperature in the gain adjusting unit 6. The position control unit 2 can generate the pressure command 8 by obtaining the control gain 12 capable of suppressing the deterioration of the position control characteristics based on the temperature value 42. As a result, the hydraulic system control device 101 can perform highly accurate and stable position control of the mechanical load even when the temperature of the hydraulic fluid changes.

Embodiment 3.
FIG. 14 is a diagram showing a hydraulic system control device 102 according to the third embodiment of the present invention and a hydraulic system 200 controlled by the hydraulic system control device 102. In the third embodiment, the gain adjusting unit 6 identifies the transmission characteristic associated with the load amount under the mechanical load. In the third embodiment, the same components as those in the first and second embodiments are designated by the same reference numerals, and the configurations different from those of the first and second embodiments will be mainly described.

The hydraulic system control device 102 has a storage unit 50 that stores the control gain 12 adjusted by the gain adjustment unit 6, and a data acquisition unit 51 that acquires a load value 52 indicating a load amount under a mechanical load. The load amount information is input to the data acquisition unit 51 by the operation of the operator. The load amount is, for example, the weight of the work. As a result, the data acquisition unit 51 acquires the load value 52.

At the time of identification of the transmission characteristic, the data acquisition unit 51 outputs the acquired load value 52 to the storage unit 50. The gain adjusting unit 6 outputs the control gain 12 to the storage unit 50. The storage unit 50 stores the load value 52 and the control gain 12 in association with each other. As a result, the storage unit 50 stores a table showing the relationship between the load amount and the control gain 12.

When the pressure of the hydraulic fluid is adjusted by the pressure command 8, the data acquisition unit 51 acquires the load value 52 and outputs the load value 52 to the position control unit 2. The position control unit 2 reads out the control gain 12 corresponding to the input load value 52 from the storage unit 50. The position control unit 2 generates a pressure command 8 based on the position command 7 and the read control gain 12.

Next, the memory of the table showing the relationship between the load amount and the control gain 12 will be described. FIG. 15 is a flowchart illustrating an operation procedure for storing a table showing the relationship between the load amount and the control gain 12 in the hydraulic system control device 102 shown in FIG.

Information on the load amount at the start of the operation of storing the table is input to the data acquisition unit 51. In step S21, the hydraulic system control device 102 sets an initial load, which is an initial value of the load value 52, based on such an input. The initial load shall be the minimum load of the machine load.

In step S22, the gain adjusting unit 6 identifies the transmission characteristic at the current load, that is, the initial load, which is the start of the operation of storing the table, and calculates the control gain 12. The method of calculating the control gain 12 is the same as that of the first embodiment. In step S23, the storage unit 50 stores the load value 52 and the control gain 12 in association with each other. In step S24, the position control unit 2 reads out the control gain 12 stored in the storage unit 50 in step S23.

Next, in step S25, the hydraulic system control device 102 increases the load and executes the position control of the piston 23a. In step S25, the load of the machine load is increased, and the information of the increased load amount is input to the data acquisition unit 51.

In step S26, the position control unit 2 determines whether or not the position control characteristic has deteriorated based on the measurement result of the position control characteristic in the position control in the state where the load is increased. The position control characteristics are measured by measuring the state waveform of the piston 23a or the mechanical load in the position control. The position control unit 2 determines whether or not the position control characteristic has deteriorated depending on whether or not the overshoot or vibration satisfies a predetermined control specification.

When it is determined that the position control characteristic has deteriorated (step S26, Yes), the hydraulic system control device 102 repeats the procedure from step S22. In step S22, the gain adjusting unit 6 identifies the transmission characteristic at the current load value 52 and calculates the control gain 12.

When it is determined that the position control characteristics have not deteriorated (steps S26 and No), in step S27, the position control unit 2 determines whether or not the load has reached a preset upper limit. The upper limit of the load is the maximum load allowed for the mechanical load.

If it is determined that the load has not reached the upper limit (steps S27, No), the hydraulic system control device 102 repeats the procedure from step S25. When it is determined that the load has reached the upper limit (step S27, Yes), the hydraulic system control device 102 ends the operation according to the procedure shown in FIG. As a result, the hydraulic system control device 102 creates a table showing the relationship between the load amount and the control gain 12 capable of suppressing deterioration of the position control characteristics.

When the position control unit 2 adjusts the pressure of the hydraulic fluid according to the pressure command 8, the position control unit 2 reads out the relationship between the load amount and the control gain 12 from the storage unit 50, and obtains the control gain 12 corresponding to the input load value 52. Ask. The position control unit 2 may determine the control gain 12 corresponding to the input load value 52 based on the relationship obtained by linear interpolation between the stored load value 52 and the control gain 12.

The hydraulic system control device 102 has the same hardware configuration as the hydraulic system control device 100 according to the first embodiment. The data acquisition unit 51 is realized by using the input / output interface 63 shown in FIGS. 9 and 10. The storage unit 50 is realized by using the external storage device 62 shown in FIGS. 9 and 10.

According to the third embodiment, the hydraulic system control device 102 has the same configuration as the hydraulic system control device 100 according to the first embodiment, so that highly accurate and stable position control of the mechanical load becomes possible. .. Further, the hydraulic system control device 102 identifies the transmission characteristic corresponding to the load amount in the gain adjusting unit 6. Based on the load value 52, the position control unit 2 can obtain a control gain 12 capable of suppressing deterioration of the position control characteristics and generate a pressure command 8. As a result, the hydraulic system control device 102 has the effect of enabling highly accurate and stable position control of the mechanical load even when the load amount changes.

The configuration shown in the above-described embodiment shows an example of the content of the present invention, can be combined with another known technique, and is one of the configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

1 Position command generator, 2 Position control unit, 3 Switching unit, 4 Identification pressure command generator, 5 Speed detection unit, 6 Gain adjustment unit, 7 Position command, 8, 9 Pressure command, 10 Position detection value, 11 Speed Value, 12 control gain, 13 pressure command for identification, 20 pump, 21 tank, 22 piping, 23 cylinder, 23a piston, 24 servo motor, 25 servo amplifier, 26 pressure detector, 27 position detector, 28 pressure detection value, 29 Current, 30 Torque, 31 Difference, 32 Value, 40, 50 Storage Unit, 41 Temperature Detector, 42 Temperature Value, 51 Data Acquisition Unit, 52 Load Value, 61 Processing Circuit, 62 External Storage Device, 63 I / O Interface, 64 processors, 65 memories, 100, 101, 102 hydraulic system controllers, 200 hydraulic systems.

Claims (6)

A hydraulic system control device that drives a pump under the control of a servomotor, operates an actuator by the pressure of a hydraulic fluid sent from the pump, and operates a mechanical load by the power transmitted from the actuator.
Control that causes the position command to follow the position detection value by generating a pressure command for adjusting the pressure based on the position command for the actuator, the position detection value that is the detection result of the position of the actuator, and the control gain. Position control unit to perform and
The transmission characteristic from the pressure command to the operating speed of the actuator is identified based on the command value of the pressure in the operation for identifying the transmission characteristic and the speed value of the operating speed of the actuator, and the transmission characteristic is obtained. A gain adjustment unit that adjusts the control gain based on
A hydraulic system control device characterized by comprising. The gain adjusting unit obtains a gain element and a delay element in the transmission characteristic based on the command value of the pressure in the operation for identifying the transmission characteristic and the speed value of the operation speed of the actuator, and obtains the gain element and the delay element in the transmission characteristic. The hydraulic system control device according to claim 1, wherein the transmission characteristic including the element and the delay element is identified. A claim characterized in that the command value of the pressure in the operation for identifying the transmission characteristic is zero at the start and end of the fixed time and becomes a non-zero value at the fixed time. Item 2. The hydraulic system control device according to item 1 or 2. The liquid according to claim 3, wherein the command value of the pressure in the operation for identifying the transmission characteristic is continuously gradually increased from zero and continuously gradually decreased from reaching a peak to zero. Pressure system controller. A storage unit for storing the temperature of the working fluid and the control gain in association with each other is provided.
The hydraulic system control device according to any one of claims 1 to 4, wherein the position control unit generates the pressure command based on the control gain read from the storage unit. A storage unit for storing the load amount of the mechanical load and the control gain in association with each other is provided.
The hydraulic system control device according to any one of claims 1 to 4, wherein the position control unit generates the pressure command based on the control gain read from the storage unit.

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