JPH073241B2 - Electro-hydraulic servo actuator dynamic characteristic compensator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a dynamic characteristic compensating device for an electrohydraulic servo actuator, and more particularly to a device using pressure feedback.

[Conventional technology]

In general, it is desirable that the servo mechanism respond with ideal fidelity to a target value and be insensitive to disturbances. Therefore, in the conventional servo mechanism, an electro-hydraulic servo actuator is used, and in order to stabilize the system against disturbances, etc., the pressure fluctuation in the hydraulic working chamber of the actuator is detected and the differential value of this is responded to the input signal. There is a so-called pressure feedback type dynamic characteristic compensating device that controls so as to cancel the above fluctuation by using a feedback signal.

As a conventional dynamic characteristic compensating device of this type, as shown in FIG. 3, for example, a cushion chamber 101 communicating with the actuator 100 and an orifice 102 in a passage connecting the actuator 100 and the cushion chamber 101 are provided. There is a pure hydraulic system in which the pressure fluctuation in the hydraulic working chamber 103 of the actuator 100 is hydraulically differentiated and the leakage valve 104 or the feedback link (not shown) is operated by the differentiated hydraulic signal.
Further, as shown in FIG. 4, the pressure in the hydraulic working chamber 201 of the actuator 200 is electromechanically converted using a strain gauge 202 or the like,
There is an electric one in which this is fed back to the electric signal input section (adder 206) via the demodulator 203, the filter 204 and the differentiator 205.

[Problems to be Solved by the Invention]

However, in the above-mentioned pure hydraulic dynamic characteristic compensator, since the orifice 102 is used, when the air unavoidably mixed in the hydraulic oil stays in the orifice 102, an extremely large error signal is generated. It is easy to cause instability of the system. Further, since the leakage valve 104 or the pressure feedback plunger is required, not only the structure becomes complicated, but also they are likely to become inoperable directly or indirectly due to the mixture of hydraulic oil. As described above, the conventional pure hydraulic differential type dynamic characteristic compensating device lacks reliability and has a complicated structure.

Further, in the electrical compensation device as described above, the strain gauge 20
Since the output signal due to electromechanical conversion such as 2 is weak, it is not only susceptible to so-called noise, but also an auxiliary electronic device such as a demodulator 203 and a drive power supply or power cable for these are required, which is also reliable. It was lacking and had a complicated structure.

The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide a dynamic characteristic compensation device for an electrohydraulic servo actuator having a simple structure and high reliability.

[Means for Solving the Problems]

In order to achieve the above object, the present invention detects a differential pressure detection piston that is displaced in proportion to the differential pressure of a hydraulic working chamber partitioned by a main piston of an actuator, and detects the speed of the differential pressure detection piston to generate an electric voltage. A speed detector for converting into a signal, and an output signal of the speed detector is fed back to a control signal input side of an electro-hydraulic servo valve for controlling oil supply / discharge of the hydraulic working chamber. Preferably, a speed transducer is used for the speed detector, and the output signal of the speed transducer is directly fed back to the compensation control coil on the control signal input circuit side of the electrohydraulic servo valve via the phase compensation coil. Alternatively, the output signal of the speed detector is fed back to the adder on the control signal input circuit side of the electrohydraulic servo valve via the first-order lag element.

[Action]

According to the present invention, when disturbance or vibration occurs in the actuator, the pressure difference between the hydraulic working chambers on both sides of the main piston fluctuates, and the speed fluctuation of the differential pressure detection piston caused by this differential pressure sliding action is detected as the speed. It is converted into an electric signal by the device and fed back to the electric signal input side of the electro-hydraulic servo valve. At this time, the feedback signal is generated as a signal obtained by differentiating the differential pressure signal by detecting the speed of the differential pressure detecting piston with a speed detector, so that it is different from the conventional hydraulic differential system using an orifice. It does not cause a problem such as generating an erroneous signal under the influence of air in the hydraulic oil and causing system instability, and because it does not require a leakage valve or pressure feedback plunger, it causes inoperability due to foreign matter caught in the hydraulic oil. In addition, the structure of the device is simplified.

In addition, the fluctuation of the differential pressure between the hydraulic working chambers is output as an electric signal of the speed detector via the differential pressure detection piston, so that the differential pressure fluctuation detection signal output is output to the one that is detected by a strain gauge or the like. It can be remarkably large, and is less susceptible to noise as compared with the conventional electrical differentiation method. Further, by using a speed transducer as the speed detector, it is possible to eliminate the need for a demodulator and a driving power supply.

〔Example〕

 The present invention will be described below with reference to the illustrated embodiments.

FIG. 1 shows an embodiment in which the present invention is applied to a system including an electrohydraulic servo valve having an auxiliary control coil (commonly called a dual coil type).

In the figure, reference numeral 1 denotes a load to be controlled, which is driven by this load 1 hydraulic actuator 2. Reference numeral 3 is an electrohydraulic servo valve for controlling the flow rate and direction (pressure supply / discharge amount and supply / discharge direction) of pressure oil to the actuator 2. The servo valve 3 includes a main control coil 4 and an auxiliary control coil 5 that operate a flapper (not shown). 6 is a hydraulic pressure source for supplying / discharging hydraulic fluid to / from the servo valve, 7 is a differential transformer (LVDT) as a position detector for detecting displacement of the output piston 8 (main piston) of the actuator 2, and 9 is a differential transformer. 7 is a position feedback circuit that transmits a position signal from the device 7. The feedback circuit 9 is provided with a demodulator 10 and a filter 11. Reference numeral 12 is an input signal generation circuit, and an input signal from the signal generator 12 is transmitted to the main control coil 4 of the servo valve 3 through the signal circuit 13. In the input circuit 13, an adder 14 for calculating the deviation between the signal from the input signal generator 12 and the signal from the position feedback circuit 9 is added.
, A response compensating element 15 for compensating the transmission delay of the servo valve 3, and a servo amplifier 16.

The reference numeral 17 denotes a differential pressure detection housed in a cylinder 20 so that it can slide in a liquid-tight manner so that it can be displaced in proportion to the differential pressure between the hydraulic working chambers 18 and 19 partitioned by the main force piston 8 of the actuator 2. It is a piston. In this differential pressure detection piston 17,
The force of the springs 21 and 22 acts so as to hold this in the neutral position. When the differential pressure detecting piston 17 is displaced by the differential pressure, the differential pressure speed is converted by the speed transducer 23 into an electric signal which is a differential signal of the differential pressure, and the servo valve 3 is controlled through the pressure feedback circuit 24. The signal is input to the auxiliary coil 5 on the signal input circuit side. In addition, the pressure feedback circuit 24
The auxiliary coil 5 and the auxiliary coil 5 receive the signal from the input signal generator 12 and the position feedback circuit 9 by the input to the auxiliary coil 5.
Are connected so as to adjust the magnetic flux generated by the main control coil 4 corresponding to the deviation from the signal from the servo valve 3 so that the differential pressure fluctuation due to the above disturbance between the hydraulic working chambers 18 and 19 is suppressed. The supply and discharge of pressure oil is controlled by. Furthermore, in the pressure feedback circuit 24, a phase compensation coil is used to compensate for system stabilization in a predetermined load frequency range.
25 are provided.

Next, the operation of this embodiment will be described.

When the command signal from the input signal generator 12 is input to the main control coil 4 of the servo valve 3 via the servo amplifier 16, the servo valve 3 operates to supply / discharge the hydraulic oil from the hydraulic source 6 to the actuator 2. (Inflow / outflow) is controlled, and the actuator 2 operates. And the output piston 8 of the actuator 2
Is detected by the differential transformer 7, and the displacement detection signal which is an electric signal is fed back to the adder 14. At this time,
Ideally, the actuator 2 should completely follow the command signal regardless of the disturbance or inertial force acting on it.
Actually, they are affected by such disturbances.

When a disturbance or the like acts on the actuator 2, the differential pressure between the hydraulic working chambers 18 and 19 partitioned by the output piston 8 fluctuates rapidly. At this time, the differential pressure detection piston 17 is displaced corresponding to the differential pressure fluctuation. And its displacement speed is
The signal corresponding to the differential value of the differential pressure fluctuation, which is the output signal thereof, is fed back from the speed transducer 23 to the auxiliary coil 5 of the servo valve 3 via the phase compensation coil 25 of the pressure feedback circuit 24. Then, by adjusting the magnetic flux of the main control coil 4 by the auxiliary coil 5 according to the feedback signal, the differential pressure is restored to a stable state to some extent, and the output of the speed transducer 23 decreases.
The control amount by the main control coil 4 is adjusted so as to suppress the differential pressure fluctuation. The effect of dynamic characteristic compensation by suppressing such differential pressure fluctuation in the present embodiment is equivalent to the conventionally known case of acceleration feedback, and will not be further described.

In the present embodiment, in generating a signal that is obtained by differentiating the differential pressure between the hydraulic working chambers 18 and 19, the differential pressure detection piston 17 that is displaced in proportion to the differential pressure as described above and the speed detection that detects the speed thereof. Since the device is used, unlike the conventional hydraulic pressure differential system using the cushion chamber and the orifice, an extreme false signal is not generated by the air in the hydraulic oil and the system is not destabilized. Further, since there is no need for a driven member such as a leakage valve or a pressure feedback plunger driven by a differentiated signal, the problem that the foreign matter in the hydraulic oil becomes trapped can cause the inoperability to be solved. It will be greatly simplified. Therefore, the structure is simple and excellent in reliability as compared with the conventional dynamic characteristic compensator using the hydraulic pressure differential method.

Further, the displacement amount of the differential pressure detection piston 17 can be remarkably larger than the deformation amount of the strain gauge or the like for the same differential pressure by appropriately selecting the pressure receiving area of the piston 17 and the pressing force of the springs 21 and 22. Since it can be increased, the detection signal output of the differential pressure fluctuation from the speed detector can be remarkably increased, and it is extremely less susceptible to noise compared to the one using the conventional electrical differentiation method. . Further, since a speed transducer 23 that does not require a power supply or a power cable is used as a speed detector, and the speed transducer 23 outputs a DC voltage signal, it is possible to use a pressure detection unit like a conventional electric differential method. No power supply, power cable, demodulator, filter, etc. are required. Therefore, the structure is simpler and more reliable than the conventional dynamic characteristic compensator using the electrical differentiation method.

Further, as described above, the output of the speed transducer 23 can be increased, and its output signal can be set to several milliamperes, which is approximately the same as the drive current of the servo valve 3, and this output signal can be directly output to the auxiliary coil 5 of the servo valve 3. Since it can be returned, this also simplifies the configuration and improves reliability.

FIG. 2 shows the configuration of the second embodiment of the present invention.

In this embodiment, the same components as those shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

The servo valve 3 of this embodiment is not provided with the auxiliary coil 5 of the first embodiment, but a speed transducer is used.
The output signal from 23 is input to the adder 14 on the control signal input circuit side of the servo valve 3. Further, the pressure feedback circuit 24 is provided with a first-order delay circuit 26 for compensating the stability of the system in a predetermined load frequency range.

Also in this embodiment, the dynamic characteristic compensating device for the electro-hydraulic servo actuator, which has a simple structure and is excellent in reliability, can be obtained by substantially the same operation as in the first embodiment.

〔effect〕

As described above, according to the present invention, the differential value of the differential pressure in the hydraulic differential chamber partitioned by the main piston of the actuator is detected by detecting the displacement speed of the differential pressure detecting piston. It is possible to solve the problem that a false signal is generated due to the influence of air in oil to cause system instability, and mechanical driven parts for differential signals such as leakage valves and pressure feedback plungers are unnecessary. Thus, it is possible to solve the problem that the foreign matter in the hydraulic oil is caught and cause the inoperability, and the structure of the device can be greatly simplified. In addition, by obtaining the differential signal of the differential pressure between the hydraulic working chambers as the electric signal output of the speed detector, the output can be significantly increased compared to the conventional electric signal output by a strain gauge or the like. It is possible to make it much less susceptible to the influence of noise as compared with the one using the dynamic differentiation method. Further, by using a speed transducer as the speed detector, the demodulator and the drive power source for the differential pressure detection unit can be eliminated. As a result, the structure of the dynamic characteristic compensating device can be simplified and its reliability can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention, FIG. 2 is a block diagram showing a second embodiment of the present invention, and FIGS. 3 and 4 are main parts of a conventional dynamic characteristic compensating apparatus. It is a schematic block diagram. 1 ... Load, 2 ... Hydraulic actuator, 3 ... Electro-hydraulic servo valve, 4 ... Main control coil, 5 ... Auxiliary coil (control signal input circuit side), 7 ... Differential transformer (position detector) ), 8 ... Output piston (main piston), 9 ... Feedback circuit, 12 ... Input signal generator, 13 ... Input circuit, 14 ... Adder (control signal input circuit side), 15 ... Responsiveness Compensation element, 16 …… Servo amplifier, 17 …… Differential pressure detection piston, 18,19 …… Hydraulic chamber, 21,22 …… Spring, 23
...... Velocity transducer (velocity detector), 24 ...... Pressure feedback circuit, 25 …… Phase compensation coil, 26 …… Primary delay circuit.

Claims (3)

[Claims] 1. A differential pressure detecting piston which is displaced in proportion to a differential pressure in a hydraulic working chamber partitioned by a main piston of an actuator, and a speed which detects the speed of the differential pressure detecting piston and converts it into an electric signal. A detector, and the output signal of the speed detector is fed back to the control signal input circuit side of the electro-hydraulic servo valve that controls the supply and discharge of oil to and from the hydraulic working chamber. Dynamic characteristic compensator for electro-hydraulic servo actuator. 2. A speed transducer is used as a speed detector, and an output signal of the speed transducer is directly fed back to an auxiliary control coil on a control signal input circuit side of an electrohydraulic servo valve through a phase compensation coil. A dynamic characteristic compensation device for an electrohydraulic servo actuator according to claim 1. 3. The electric device according to claim 1, wherein the output signal of the speed detector is fed back to the adder on the side of the control signal input circuit of the electrohydraulic servo valve through the first-order lag element. Dynamic characteristic compensator for hydraulic servo actuator.