JPS6229778A - Static oil hydraulic pressure driving control device - Google Patents

Abstract

PURPOSE:To stably control the pressure of a static oil hydraulic pressure driving gear and its speed, by performing positive feedback control of a speed signal of an oil hydraulic actuator to promote a stable control objective thereafter performing a feedback control of the pressure and the speed. CONSTITUTION:A function generator 14, inputting by controlling a control lever 6 a deviation DELTAomega between a speed command signal omegas of an oil hydraulic actuator and its actual speed signal omegam, outputs a difference pressure preset value Ps. A control arithmetic device 16, inputting a deviation DELTAP of said difference pressure preset value Ps from a difference pressure P of the oil hydraulic actuator, outputs a pressure control signal epsilonp. While the device 16 outputs a signal epsilonm applying a feedback gain 17 to the actual speed signal omegam. And the control arithmetic device 16 outputs a signal, performing a positive feedback control of the signal epsilonm to add it to the pressure control signal epsilonp, so as to control a swash plate driving servo system 11A of an oil hydraulic pump.

Description

[Detailed Description of the Invention] [Industrial Field of Application] Construction machines such as hydraulic cylinders and bells according to the present invention, or the like [Prior Art] An example of a conventional hydrostatic drive device is one constructed as shown in Fig. 5. be.

In FIG. 5, reference numeral 1 denotes a hydraulic pump driving prime mover (hereinafter referred to as prime mover), zn a variable displacement hydraulic pump (hereinafter referred to as hydraulic pump) driven by this prime mover 1, a hydraulic actuator such as an sFi hydraulic motor, 4 5 is a swash plate that sets the discharge flow rate of the hydraulic pumper 2; 5 is a hydraulic I pump swash plate control device;
6 is an operating lever, 7a and 7b are crossover relief valves, and 8 is a load driven by the hydraulic actuator 3. As shown in Fig. 5, hydraulic cylinder f2 and hydraulic actuator 3
are directly connected by a pipe L1t12 to form a closed circuit.

The operation of the hydrostatic drive device configured as above will be explained. In FIG. 5, the discharge flow rate of the hydraulic pumper 2 driven by the prime mover 1 is controlled by a swash plate 4 controlled by a swash plate control device 5, and returns to the hydraulic pump suction side.

Now, when you operate -6 and move it to the right side, the swash plate control device 5 operates the swash plate 4 in the direction of the arrow ■ in the figure, and the pressure oil discharged from the port 2IL of the hydraulic input f2 flows into the pipe. The hydraulic actuator 3t (f3) enters the $-t Ja of the hydraulic actuator 3 through the path t1 and drives the load 8 in the direction of the arrow.Furthermore, the oil discharged from the hydraulic actuator 3 returns to the port 2b of the hydraulic pump 2 through the pipe t2.

When the par 6 is returned from the position ■ to the neutral position after 10,000 operations, the swash plate 4 moves in the direction of the arrow e, and pressure oil is discharged from the port 3b of the hydraulic actuator 3 due to the inertial energy of the load 8, and from the pipe t2. It is supplied to the port 2b of the hydraulic cylinder f2, drives the hydraulic actuator 3, and can be recovered as energy 1 - prime mover 1 during braking of the load 8. Operation lever 6
When is operated to the e side, the movement of the swash plate 8 and the movement of the hydraulic actuator 3 are in the O direction, but the same process is performed.

The characteristics of the hydrostatic drive system described above are that there is no directional control valve or relief valve in the main circuit, so there is no throttling loss or bleed-off loss, so there is little energy loss, and when controlling the load or when a negative load is applied. The advantage is that energy can be recovered into the prime mover.

To achieve the above features, the cross-over relief valve 7m is used by controlling the swash plate 4.

It is necessary to control the pressure so that the circuit pressure does not rise above the set pressure 7b, and to control the steady rotational angular velocity of the hydraulic actuator 3 so that it is in a proportional relationship with the operating lever 6.

[Problem that the invention seeks to solve]

By the way, a commonly thought method for controlling pressure is a method of detecting the circuit pressure P1sP2 and controlling the swash plate 4 so that the circuit differential pressure P does not exceed the set pressure. However, with a simple pressure feed system, problems may occur depending on the characteristics of the hydraulic load system.

When the swash plate 4 is controlled, it oscillates and becomes unstable.

The reason for this will be explained below with reference to FIGS. 6 and 7.

FIG. 6 shows a model of the hydraulic drive system of the hydrostatic drive device when accelerating the hydraulic actuator 3. Ignoring the viscous resistance of the load system and the pipe resistance, the characteristic equation of the hydraulic drive system is given by the following equation.

dP −1=Dωφ−Dmω□−KLP (1)
βdt PPP = DyrlP ... (2) t
JP=P, -p2...(3)P
l, P2: Circuit pressure (kg/FI) β: Bulk modulus of oil (kg/cm) D,: Hydraulic pump capacity (ec/rid) Dm: Hydraulic actuator capacity (cc/rad) Li: Hydraulic pump swash plate Tilt angle (
−) ω, angular velocity of rotation of two hydraulic pumps (rad/see)
0m: Hydraulic actuator rotation angular velocity (raφee)
J: Load inertia factor (kytYnsec) V
:One gA1g between the hydraulic pump and hydraulic actuator
Product (CC) ++ -J +-M customer /
−−/−−//+−−/ 2X) Above (1) #
From equation (2), find the transfer function from φ to P. However, according to equation 4, the swash plate tilt angle φ in the hydraulic drive system.

The transfer function between P and circuit differential pressure P is expressed as the product of a second-order lag element and a differential element. Figure 7 shows the pressure feeder, evening type, where P is the circuit setting differential pressure, 9 is the feeder and summation point of the circuit differential pressure, 10 is the proportional gain, and 11
is the swash plate drive servo system transfer function and the xzFi hydraulic drive system transfer function, and the output of this hydraulic drive system transfer function 12 is the circuit differential pressure P.

The hydraulic drive system transfer function 12 to be controlled has a differential element as shown in equation (4) above, and the natural frequency of the second-order lag element is as low as about ωxll-t2Hz, and the damping stop is C-ke0.
In the case where the circuit is heated at a temperature of about -2, the circuit differential pressure P cannot be set to an arbitrary pressure and oscillates.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an entire hydrostatic drive control device that can eliminate the above-mentioned problems and stably control pressure and speed.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention is constructed as follows. That is, in a hydrostatic drive device in which a variable displacement hydraulic pump and a hydraulic actuator such as a hydraulic motor are directly connected through a pipe to form a closed circuit, a function that takes as input the deviation between the speed command and the actual speed of the hydraulic actuator is used. The differential pressure of the hydraulic actuator is set by a generator, the deviation compared with the actual differential pressure of the hydraulic actuator is inputted to a control calculator, and the control calculation signal obtained here is added to the speed signal of the hydraulic actuator. The combined signal controls all of the swash plates of the variable displacement hydraulic pump.

[Effect]

The hydraulic drive system to be controlled contains differential elements and vibration roots with poor damping, and the pressure cannot be controlled by simple pressure feedback control. Differential elements and vibration roots are removed to stabilize the controlled object, followed by pressure feedback and velocity feed feedback.

〔Example〕

Hereinafter, one embodiment of the hydrostatic drive control device of the present invention will be described with reference to FIGS. 1 to 4. First, the control circuit diagram will be explained with reference to FIG.

In the figure, reference numeral 6 denotes the above-mentioned operating lever from which a hydraulic actuator-23 degree rotation angular velocity command signal is output. 13 is the addition point of the feedback signal of this rotational angular velocity command signal ω and the actual rotational angular velocity ω of the hydraulic motor; 14 is the rotational angular velocity deviation Δω from the addition point 13; the differential pressure setting value P; A function generator 15 outputs the differential pressure set value P output from the function generator 14 and the actual circuit differential pressure P,
Here, the addition point that outputs the differential pressure difference ΔP'c between the two is 1
6a is a proportional dyne, 16b is an integrator, 16c is a point where the output from the proportional dyne 16a and the output from the integrator 16b are added, 16*, 16b, 16c''f, collectively the control calculator 16. 17 is the feedback dyne, 18 is the addition point of the tip feedback of the signal radiation multiplied by the rotational angular velocity ω□ of the hydraulic actuator, 11A is the swash plate drive serve system, and 19 is the hydraulic drive system. It shows.

Next, an example of the function generator I4 will be explained with reference to FIG. That is, the input of the function generator 14 is the rotational angular velocity deviation Δ between the rotational angular velocity command ω and the actual rotational velocity ω.
ω, and the output is the differential pressure set value P3, and the rotational angular velocity deviation Δω is −ω. When the pressure difference is between ω and ω, the differential pressure setting value P6 is the rotational angular velocity/Fl ”I'r Jl,,
1/rL+-rKill I Roko--/'P
I '7F #G /Pi YuteIt, +
Jy? z, + Ill τ-Rumor is -P
P for 1ω or more. 1X is the differential pressure setting value P, binding max
c and output.

The operation of one embodiment of the hydrostatic drive control device according to the present invention constructed as described above will be explained with reference to FIGS. 3 and 4. In FIG. 1, when the operating lever 6 is operated, a rotational angular velocity command signal ω of the hydraulic actuator is output, and at a summing point 13, the actual rotational angular velocity ω of the hydraulic actuator is output. is fed, and the rotational angular velocity deviation Δω is input to the function generator 14. This function generator 14 outputs a differential pressure set value P according to the value of the rotational angular velocity deviation Δω, which is compared with the actual circuit differential pressure P at a summing point 15, and this differential pressure deviation ΔP is input to the control calculator 16. The pressure control signal 1 is the rotational angular velocity ω of the hydraulic actuator. signal 8n1 multiplied by feedback dyne 17 and summation point 1
8 and is applied to the swash plate drive servo system 11k to move the swash plate 4 of the hydraulic pump and the pressure Pm of the hydraulic actuator 3
One rotation angular velocity ωmK-control.

In a personal opinion, the hydraulic actuator rotation angular velocity command signal ω is set when the operating lever 6 is operated in a stopped state. The rotational angular velocity deviation Δω at the first summing point 13 becomes larger than the value ω at the bending point of the function generator 14, and the differential pressure setting value P from the function generator 14 becomes the positive maximum differential pressure value Pn1□. , hydraulic actuator 3t - Actual circuit differential pressure P on the accelerating side rises and settles to the positive maximum differential pressure value Pm□, and continues accelerating the hydraulic actuator 3. Next, the hydraulic actuator rotation angular velocity ω approaches the command speed ω, and the rotation angular velocity deviation Δω at the summing point 13 becomes ω. Below, the differential pressure set value P from the function generator 14 decreases in proportion to the rotational angular velocity deviation Δω, and accordingly, the circuit differential pressure P that drives the hydraulic actuator 3 decreases, and the rotational angular velocity ω of the hydraulic actuator 3 decreases. When the rotational angular velocity deviation Δω gradually increases and reaches O, the differential pressure setting value PII becomes 0, and the hydraulic actuator 3 is no longer accelerated and rotates at the rotational angular velocity command signal ω.

Next, when the operating lever 6 is returned to neutral, the rotational angular velocity command signal ω
, becomes 0, and the rotational angular velocity deviation Δω at the summing point 13 is the value of the bending point of the function generator 14 -ω.

The differential pressure set value p, t' output from the function generator 14- is set to the negative maximum differential pressure value -Pma! Therefore, the circuit differential pressure P stands on the side that decelerates the hydraulic actuator 3, and at the negative maximum differential pressure value -Ptn,Lx, the hydraulic actuator 3'f
c Continue to decelerate. Rotational angular velocity ω of the hydraulic actuator 3.

approaches O, and the rotational angular velocity deviation Δω at the summing point 13
One ω. When the value is between 0 and 0, the differential pressure setting value P decreases in proportion to the rotational angular velocity deviation Δω, and the hydraulic actuator 3 gradually decelerates and stops.

■Positive feed of hydraulic actuator rotational angular velocity, Figure 4 shows hydraulic actuator rotational angular velocity ω. ni r in 17
Multistable control can be obtained by giving positive feedback to the multiplied signal.

This is a professional line diagram for explaining everything. In FIG. 4, 20 is a load transfer function. Feedback dyne 17 is given by the following equation.

Dm/D, ω, ... (5) Organize the professional line diagram in Figure 4 and find the transfer function between the swash plate φ and the circuit differential pressure P. However, from equation 6), the control target Hydraulic actuator rotational angular velocity ω
. It can be proven that by positively feeding back the signal obtained by multiplying the input signal by FUG-IN 17, the differential element and the vibrator with poor damping can be removed from the hydraulic drive system which is the controlled object, and the vibrator with poor damping can be replaced with a stable controlled object.

■Speed control As shown in FIG. 1, the output of the operating lever 6 corresponds to the hydraulic actuator rotational angular velocity command ω3, which corresponds to the actual hydraulic actuator 30 rotational speed ω. and is compared at addition point 13, and the rotational angular velocity deviation Δω is calculated.
IPM! Mouth: Where cb
6 Divination n Coffin IJ4 → ] -r 4 橢 7. Since the function generator 14 has the characteristic shown in Fig. 2 that when the rotational angular velocity deviation Δω approaches 0, the differential pressure setting value P becomes 0. The rotational angular velocity ω of the hydraulic actuator 3 is set to the rotational angular velocity command ω3. A steady rotational angular velocity of the hydraulic actuator 3 is obtained that is proportional to the amount of operation of the tab 9 operation lever 6.

■Pressure control The actual circuit differential pressure P is compared with the differential pressure set value P8 output from the function generator 14 at the summing point 15, and the differential pressure deviation ΔP
The swash plate drive servo system 1 is calculated and used as a pressure control signal.
Differential pressure Pk given to 1A crossover relief valve 7m.

If the opening pressure is set below the opening pressure of ax 2b, the crossover relief valves 7m and 7b will not operate, so there will be no energy loss in the crossover relief valves 7h and 7b, and the original objective of energy saving can be achieved.

〔Effect of the invention〕

The present invention described above provides a hydrostatic drive device in which a variable displacement hydraulic pump and a hydraulic actuator such as a hydraulic motor are directly connected through a conduit to form a closed circuit, in which a deviation between a speed command and an actual speed of the hydraulic actuator is provided. The differential pressure of the above-mentioned hydraulic actuator is set by a function generator that takes as input, and the deviation compared with the actual differential pressure of the above-mentioned hydraulic actuator is inputted to a control calculator, and the control calculation signal obtained here and the above-mentioned hydraulic pressure are The present invention is characterized in that the swash plate of the variable displacement hydraulic pump is entirely controlled by a signal obtained by adding the speed signal of the actuator.

Therefore, it is possible to provide a hydrostatic drive control device that can stably control pressure and speed.

[Brief explanation of drawings]

Fig. 1 is a control circuit diagram showing an embodiment of the hydrostatic drive control device according to the present invention, Fig. 2 is a characteristic diagram for explaining the function of the function generator shown in Fig. 1, and Fig. 3 is a diagram similar to the one shown in Fig. 1. FIG. 4 is a diagram for explaining the operation and effect of FIG. 1, FIG. 5 is a schematic configuration diagram showing an example of a conventional hydrostatic drive device, and FIG. FIG. 7 is a modeled diagram of a hydraulic drive system for explaining the problems in the figure, and FIG. 7 is a diagram for explaining the problems in FIG. DESCRIPTION OF SYMBOLS 1... Hydraulic pump drive prime mover, 2... Variable displacement hydraulic pump, 3... Hydraulic actuator, 4... Swash plate, 5... Hydraulic Dengue swash plate control device, 6... Operation Lever, 7m, 7b...Riq suono relief valve, 8.
...Load, 1...Swash plate drive serve system, J3゜15.
16c, IIJ... Addition point, 14... Function generator, 161... Proportional gain, 16b... Integrator, 1
7...Feedback dyne, 19...Hydraulic drive system. 11'', Applicant's representative Patent attorney Suzue Takehiko

Claims (1)

[Claims] In a hydrostatic drive system in which a variable displacement hydraulic pump and a hydraulic actuator that drives a load are directly connected via a pipe to form a closed circuit, a function is generated that takes as input the deviation between the speed command of the hydraulic actuator and the actual speed. The difference between the set value of the differential pressure of the hydraulic actuator and the actual differential pressure of the hydraulic actuator is input into the control calculator, and the control calculation signal obtained here is added to the speed signal of the hydraulic actuator. A hydrostatic drive control device, characterized in that the swash plate of the variable displacement hydraulic pump is controlled by the combined signals.