CN110966270B - Digital electro-hydrostatic actuator system - Google Patents
Digital electro-hydrostatic actuator system Download PDFInfo
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- CN110966270B CN110966270B CN201911347751.XA CN201911347751A CN110966270B CN 110966270 B CN110966270 B CN 110966270B CN 201911347751 A CN201911347751 A CN 201911347751A CN 110966270 B CN110966270 B CN 110966270B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
- F15B11/08—Servomotor systems without provision for follow-up action; Circuits therefor with only one servomotor
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B1/00—Installations or systems with accumulators; Supply reservoir or sump assemblies
- F15B1/02—Installations or systems with accumulators
- F15B1/04—Accumulators
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B13/00—Details of servomotor systems ; Valves for servomotor systems
- F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
- F15B13/023—Excess flow valves, e.g. for locking cylinders in case of hose burst
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
- F15B21/08—Servomotor systems incorporating electrically operated control means
Abstract
The invention provides a digital electro-hydrostatic actuator system, which comprises: the servo motor is connected with the hydraulic pump; the high-speed switch valve group is connected with the hydraulic pump; the hydraulic cylinder is connected with the high-speed switch valve bank, and a piston rod of the hydraulic cylinder is connected with a load; a signal processor which receives signals and parameters of the sensor; and the system state control unit is connected with the signal processor and controls the actions of the servo motor and the high-speed switch valve group according to the feedback signal or parameter information so as to form differential control and load independent control. The system has the advantages of larger control freedom degree, higher control precision, energy conservation and reliable action.
Description
Technical Field
The invention belongs to the technical field of electro-hydraulic control, and particularly relates to a digital electro-hydrostatic actuator system.
Background
With the increasing requirements on flexible use and low energy consumption of driving mechanisms in the fields of aerospace and traditional industries, electro-hydrostatic actuators are widely adopted in high-power servo mechanisms of aircrafts in the future.
The electro-hydrostatic actuator is a system which highly integrates elements such as a motor, a hydraulic pump, a hydraulic valve, an energy accumulator, a hydraulic cylinder and the like, and has the advantages of higher power-weight ratio and higher transmission efficiency. However, conventional electro-hydrostatic actuators generally reverse the direction of the pump-controlled hydraulic cylinder, and thus the system response is slow. When the actuator is an asymmetric cylinder, the control accuracy of the hydraulic system is low under the influence of the flow imbalance characteristic of the asymmetric cylinder. When the control element is a hydraulic control one-way valve, the opening and closing time of the valve port is long and cannot meet the requirement of a hydraulic system on high frequency response, and although the electro-hydraulic servo valve has short response time and can obtain high control precision, the electro-hydraulic servo valve has poor anti-pollution capability and large heating. Various problems limit the development of the electro-hydrostatic actuator towards high efficiency, energy conservation, high frequency response, high control precision and high reliability.
Disclosure of Invention
Aiming at part or all of the technical problems in the prior art, the invention provides a digital electro-hydrostatic actuator system which has the advantages of higher control freedom degree, higher control precision, energy conservation and reliable action.
In order to achieve the above object, the present invention provides a digital electro-hydrostatic actuator system, comprising:
the servo motor is connected with the hydraulic pump;
the high-speed switch valve group is connected with the hydraulic pump;
the hydraulic cylinder is connected with the high-speed switch valve bank, and a piston rod of the hydraulic cylinder is connected with a load;
a signal processor which receives signals and parameters of the sensor;
and the system state control unit is connected with the signal processor and controls the actions of the servo motor and the high-speed switch valve group according to the feedback signal or parameter information so as to form differential control and load independent control.
In one embodiment, the system further comprises a pressure protection valve, wherein the pressure protection valve comprises a first pressure protection valve, a second pressure protection valve and a third pressure protection valve, wherein an oil inlet of the first pressure protection valve is communicated with the high-pressure oil port of the pump, and an oil outlet of the first pressure protection valve is communicated with the oil filling port of the hydraulic pump; an oil inlet of the second pressure protection valve is communicated with a rodless cavity of the hydraulic cylinder, and an oil outlet of the second pressure protection valve is communicated with a system oil return path; an oil inlet of the third pressure protection valve is communicated with a rod cavity of the hydraulic cylinder, and an oil outlet of the third pressure protection valve is communicated with a system oil return circuit.
In one embodiment, the set pressure of the first pressure protection valve is higher than the second pressure protection valve and the third pressure protection valve.
In one embodiment, the system further comprises an accumulator connected to the main oil return line of the system, and the accumulator is connected to the oil charge port of the hydraulic pump.
In one embodiment, a first pressure sensor is connected to an oil inlet and outlet of the accumulator; a second pressure sensor is connected to an oil inlet and outlet path of a rod cavity of the hydraulic cylinder; a third pressure sensor is connected to an oil inlet and outlet path of the rodless cavity of the hydraulic cylinder; and a hydraulic cylinder piston rod of the hydraulic cylinder is connected with a displacement sensor.
In one embodiment, the high-speed switch valve group comprises a first high-speed switch valve, a second high-speed switch valve, a third high-speed switch valve and a fourth high-speed switch valve, and the first high-speed switch valve is arranged between a high-pressure oil port of the bidirectional quantitative hydraulic pump and a rodless cavity of the single-rod hydraulic cylinder; the second high-speed switch valve is arranged between a rod cavity of the single-rod hydraulic cylinder and a high-pressure oil port of the bidirectional quantitative hydraulic pump; the third high-speed switch valve is arranged between the rodless cavity of the single-rod hydraulic cylinder and the oil filling port of the bidirectional quantitative hydraulic pump; and the fourth high-speed switch valve is arranged between a rod cavity of the single-rod hydraulic cylinder and an oil filling port of the bidirectional quantitative hydraulic pump.
In one embodiment, a high-pressure oil port of the bidirectional quantitative hydraulic pump is communicated with a first high-speed switch valve, an oil charging port of the bidirectional quantitative hydraulic pump is communicated with an energy accumulator, and the reversing action of the hydraulic cylinder is realized by alternately opening and closing the first high-speed switch valve and a second high-speed switch valve; when the first high-speed switching valve and the second high-speed switching valve are simultaneously opened and the third high-speed switching valve and the fourth high-speed switching valve are simultaneously closed, the system becomes a differential state.
In one embodiment, the signal processor comprises a displacement-rotation speed calculation unit, a speed gradient selection unit, a servo driver, a speed encoder, a differential state control unit, a load independent control unit, a displacement deviation detection unit, a signal acquisition and processing unit and a system state monitoring unit.
In one embodiment, the signal acquisition and processing unit is used for acquiring a rotating speed signal, an energy accumulator pressure signal, a hydraulic cylinder rod cavity pressure signal, a hydraulic cylinder rodless cavity pressure signal and a hydraulic cylinder piston rod displacement signal of a servo motor output by the speed encoder, the first pressure sensor, the second pressure sensor, the third pressure sensor and the displacement sensor, the rotating speed signal, the energy accumulator pressure signal, the hydraulic cylinder rod cavity pressure signal, the hydraulic cylinder rodless cavity pressure signal and the hydraulic cylinder piston rod displacement signal are received and stored in the system state control unit after being processed, and displacement and pressure deviation are judged respectively after difference processing is carried out in the control unit so as to execute a next command.
In one embodiment, the servo driver outputs a driving signal to control the servo motor to rotate, meanwhile, the rotating speed of the servo motor is received by the speed encoder and then fed back to the servo driver, the servo driver completes accurate closed-loop control on the rotating speed of the servo motor and drives the bidirectional quantitative hydraulic pump to output pressure and flow; the high-speed switch valve controls the opening and closing time of the valve port according to the PWM command signal output by the signal processor, so that the pressure and flow control of oil output by the valve port are realized; the pressure and the flow of the oil output by the bidirectional quantitative hydraulic pump and the high-speed switch valve jointly influence the pressure and the flow of a rodless cavity and a rod cavity of the hydraulic cylinder, and finally the displacement of a piston rod of the hydraulic cylinder is controlled.
Compared with the prior art, the invention has the advantages that:
the invention realizes the digital control of the electro-hydrostatic actuator by introducing the high-speed switch valve; the load independent technology is added, so that the energy saving performance and the control precision of the system are improved; the high-speed switch valve can realize the state switching between the normal work and the differential work of the hydraulic cylinder by alternately switching on and off, thereby realizing the flow regeneration; the hydraulic cylinder adopts position-pressure combined control, namely a rodless cavity is in position closed-loop control during pushing, a rod cavity is in pressure closed-loop control, a rod cavity is in position closed-loop control during returning, and a rodless cavity is in pressure closed-loop control, so that the control precision is improved, and the influence caused by pressure fluctuation of the hydraulic cylinder is reduced; the control unit and the signal processor coordinate the work of each part of elements, so that the invention has the characteristics of large control freedom degree, high precision, obvious energy-saving effect and reliable action.
Drawings
Preferred embodiments of the present invention will be described in detail below with reference to the attached drawing figures, wherein:
FIG. 1 is a hydraulic system schematic of the digital electro-hydrostatic actuator system of the present invention.
Fig. 2 is a control schematic of the digital electro-hydrostatic actuator system of the present invention.
In the drawings, like parts are provided with like reference numerals. The figures are not drawn to scale.
Detailed Description
In order to make the technical solutions and advantages of the present invention more apparent, exemplary embodiments of the present invention are described in further detail below with reference to the accompanying drawings. It is clear that the described embodiments are only a part of the embodiments of the invention, and not an exhaustive list of all embodiments. And the embodiments and features of the embodiments may be combined with each other without conflict.
The inventor notices in the invention process that the traditional electro-hydrostatic actuator has the problems of small control freedom degree, low precision, slow reversing response and low action reliability.
In view of the above disadvantages, embodiments of the present invention provide a digital electro-hydrostatic actuator system, which will be described in detail below.
Fig. 1 illustrates one embodiment of the digital electro-hydrostatic actuator system of the present invention. In this embodiment, the digital electro-hydrostatic actuator system mainly comprises: the servo motor 1, a hydraulic pump 2, a high-speed switch valve group 5, a hydraulic cylinder 6, a sensor, a signal processor 9 and a control unit 10. Wherein, the servo motor 1 is connected with the hydraulic pump 2. The high-speed switch valve group 5 is connected with the hydraulic pump 2. The hydraulic cylinder 6 is connected with the high-speed switch valve group 5, and a piston rod of the hydraulic cylinder 6 is connected with a load. The signal processor 9 receives signals and parameters from various sensors. The system state control unit 10 is connected with the signal processor 9, and controls the actions of the servo motor 1 and the high-speed switch valve group 5 according to the feedback signal or parameter information, so as to form various working states such as differential control and load independent control.
In a preferred embodiment, as shown in fig. 1 and 2, the digital electro-hydrostatic actuator system mainly comprises a servo motor 1, a bidirectional quantitative hydraulic pump 2, an accumulator 3, a pressure protection valve 4, a high-speed switch valve group 5, a hydraulic cylinder 6, a displacement sensor 7, a pressure sensor 8, a signal processor 9 and a system state control unit 10. The power output shaft of the servo motor 1 is connected with the power input shaft of the bidirectional quantitative hydraulic pump 2, and the servo motor 1 drives the hydraulic pump 2 to finish oil absorption and oil discharge processes. The high-pressure oil port 201 of the bidirectional quantitative hydraulic pump 2 is communicated with the first high-speed switch valve 501, and the oil filling port 202 of the bidirectional quantitative hydraulic pump 2 is communicated with the energy accumulator 3. The digital electro-hydrostatic actuator is configured to extend and retract a piston rod of the hydraulic cylinder 6 by alternately opening and closing the first high-speed switching valve 501 and the second high-speed switching valve 502. In addition, the system assumes a differential state when the first high-speed switching valve 501 and the second high-speed switching valve 502 are simultaneously opened and the third high-speed switching valve 503 and the fourth high-speed switching valve 504 are simultaneously closed.
In a preferred embodiment, as shown in fig. 1, there are 4 high-speed switch valves 5, wherein the first high-speed switch valve 501, the second high-speed switch valve 502, the third high-speed switch valve 503 and the fourth high-speed switch valve 504 are all two-way valves, and the valve ports are kept closed in the power-off state. Wherein the first high-speed switch valve 501 connects the pump high-pressure port 201 and the rodless chamber 601 of the hydraulic cylinder 6. The second high-speed on-off valve 502 connects the pump high-pressure port 201 and the rod chamber 603 of the hydraulic cylinder 6. The third high-speed switch valve 503 is connected to the rodless chamber 601 of the hydraulic cylinder 6 and the pump oil charge port 202 of the hydraulic pump, and the fourth high-speed switch valve 504 is connected to the rod chamber 603 of the hydraulic cylinder 6 and the pump oil charge port 202.
In an embodiment not shown, four high-speed switch valves can be respectively replaced by parallel high-speed switch valve groups according to different system flow rates so as to realize control of large flow rate. The function of each group of valves is the same as that of a single valve, and the opening and closing actions of each valve port are controlled by signals sent by the signal processor 9, so that the on-off and the size adjustment of the flow are realized.
In one embodiment, as shown in fig. 1, the system is provided with three pressure protection valves 4. An oil inlet of the first pressure protection valve 401 is communicated with the high-pressure oil port 201 of the hydraulic pump 2, an oil outlet of the first pressure protection valve 401 is communicated with the oil filling port 202 of the hydraulic pump 2, and the first pressure protection valve 401 is used for limiting the safety pressure of the system. The second pressure protection valve 402 and the third pressure protection valve 403 are respectively connected to the two chambers of the hydraulic cylinder 6 and the oil filling port 202 of the hydraulic pump 2, and the pressure setting values of the second pressure protection valve 402 and the third pressure protection valve 403 are the same and are the highest pressures of the two chambers (i.e., the rodless chamber 601 and the rod chamber 602) when the hydraulic cylinder 6 works. When the system is in normal operation, the valve ports of the first pressure protection valve 401, the second pressure protection valve 402 and the third pressure protection valve 403 are closed. When the pressure of the system rises suddenly, the corresponding pressure protection valve opens the overflow valve, and the pressure of the system and the hydraulic cylinder is ensured not to exceed the highest allowable pressure. It is noted that the set pressure of the first pressure protection valve 401 should be higher than the second pressure protection valve 402 and the third pressure protection valve 403 to achieve a double protection of the system.
In one embodiment, as shown in fig. 1, the accumulator 3 is installed on the system main oil return line, and a first pressure sensor 801 is connected to the oil inlet and outlet of the accumulator 3. A second pressure sensor 802 is connected to an oil inlet/outlet passage of the rod chamber 603 of the hydraulic cylinder 6. A third pressure sensor 803 is connected to the oil inlet and outlet of the rodless chamber 603 of the hydraulic cylinder 6. The output signals of the pressure sensors 801, 802 and 803 are received by the signal processor 9 and transmitted to the control unit 10, so as to realize real-time monitoring of the pressure state of the system.
In one embodiment, as shown in fig. 1, the cylinder piston rod 603 of the hydraulic cylinder 6 is connected with a displacement sensor 7. The output signal of the displacement sensor 7 is received and processed by the signal processor 908. The system state control unit 10 realizes instruction input and system state display of the entire system.
Fig. 2 illustrates the control system principle of the digital electro-hydrostatic actuator system of the present invention. In the embodiment shown in fig. 2, the signal processor 9 mainly includes a displacement/rotation speed calculation unit 901, a speed gradient selection unit 902, a servo driver 903, a speed encoder 904, a differential state control unit 905, a load independent control unit 906, a displacement deviation detection unit 907, a signal processor 908, and a system state monitoring unit 909. The signal processor 908 is configured to collect a rotation speed signal of the servo motor 1, a pressure signal of the accumulator 3, a pressure signal of the rod cavity 603 of the hydraulic cylinder 6, a pressure signal of the rod-free cavity 601 of the hydraulic cylinder 6, and a piston rod displacement signal of the hydraulic cylinder 6, which are output by the speed encoder, the first pressure sensor 401, the second pressure sensor 402, the third pressure sensor 403, and the displacement sensor 7, receive the signals through the system state monitoring unit 909 and store the signals in the system state control unit 10 after processing, and determine displacement and pressure deviation after performing difference processing in the control unit 10, so as to execute a next command. The servo driver outputs a driving signal to control the servo motor 1 to rotate, meanwhile, the rotating speed of the servo motor 1 is received by the speed encoder and then fed back to the servo driver, the servo driver completes accurate closed-loop control on the revolution number of the servo motor 1, and the servo driver drives the bidirectional quantitative hydraulic pump 2 to output pressure and flow. The high-speed switch valve 5 controls the opening and closing time of the valve port according to the PWM command signal, and realizes the pressure and flow control of the oil output from the valve port. The pressure and flow of the output oil of the bidirectional quantitative hydraulic pump 2 and the high-speed switch valve 5 jointly influence the pressure and flow of the rodless cavity 601 of the hydraulic cylinder 6 and the pressure and flow of the rod cavity 602 of the hydraulic cylinder 6, and finally the displacement of the piston rod 603 of the hydraulic cylinder is controlled. The above process is the working process in one working cycle of the invention, and the above processes are performed in sequence in each working cycle and are continuously circulated until the output signals of the displacement sensor and the pressure sensor are the same as the displacement command signal and the pressure command signal and are not changed any more.
In a preferred embodiment, in fig. 1, the functions of the first high-speed switch valve 501, the second high-speed switch valve 502, the third high-speed switch valve 503 and the fourth high-speed switch valve 504 are all realized by one high-speed switch valve 5, and the hydraulic cylinder 6 is in the form of a single-rod asymmetric hydraulic cylinder, that is, a hydraulic cylinder piston rod extends out at one end only, and the hydraulic pressure acting areas at two ends of the hydraulic cylinder piston 602 are not equal.
In one embodiment, as shown in fig. 2, the digital electro-hydrostatic actuator system of the present invention can achieve load independent control, hydraulic cylinder differential control, system displacement and pressure control. The working process of the present invention under different control methods will be described separately below. It should be noted that, in different operating states of the system, the control unit 10 and the signal processor 9 output signals to always make the servo motor drive the hydraulic pump 2 to rotate in the forward direction, and the oil enters the system from the high-pressure oil port 201 of the bidirectional fixed displacement pump 2. The energy accumulator 4 is arranged at the position of the main oil return path close to the pump source, so that oil is automatically supplemented into the system or redundant oil is absorbed, and the oil absorption flow and the oil discharge flow of the bidirectional quantitative hydraulic pump 2 are equal.
In one embodiment, as shown in fig. 1 and 2, the load independent control process of the present invention: the first high-speed switch valve 501 and the third high-speed switch valve 503 on the oil inlet and outlet paths of the rod cavity 603 of the hydraulic cylinder are connected in parallel, and the second high-speed switch valve 502 and the fourth high-speed switch valve 504 on the oil inlet and outlet paths of the rod cavity 603 of the hydraulic cylinder are connected in parallel. In the process of pushing out the piston rod of the hydraulic cylinder, the control unit 10 and the signal processor 9 output signals to open the first high-speed switch valve 501 and the fourth high-speed switch valve group 504, and close the second high-speed switch valve group 502 and the third high-speed switch valve group 503. In the starting stage of the hydraulic cylinder, the backpressure value can be reduced through the high-speed switch valve 5, so that the starting performance of the system is improved, and the smoothness of the system movement can be realized through the increase of the backpressure in the working process. Further, the high-speed switching valve 5 can control the flow rate ratio of the first high-speed switching valve 501 and the fourth high-speed switching valve 504 to be equal to the area ratio of the cylinder rodless chamber 601 and the cylinder rod chamber 603 by a PWM (pulse width modulation) signal, thereby suppressing pressure pulsation due to the flow rate imbalance characteristic of the asymmetric cylinder and improving the control accuracy. Similarly, in the retraction process of the piston rod of the hydraulic cylinder, the control unit 10 and the signal processor 9 output signals to open the second high-speed switching valve set 502 and the third high-speed switching valve set 503, and close the first high-speed switching valve set 501 and the fourth high-speed switching valve set 504. In addition, the high-speed switching valve 5 can achieve the flow ratio of the third high-speed switching valve 503 and the second high-speed switching valve 502 equal to the area ratio of the cylinder rodless chamber 601 and the cylinder rod chamber 603 by PWM signal control, thereby suppressing pressure pulsation due to the flow imbalance characteristic of the asymmetric cylinder and improving the control accuracy.
In one embodiment, as shown in fig. 1 and 2, the hydraulic cylinder differential control process of the present invention includes: adopt the asymmetric pneumatic cylinder of single play pole, when the pneumatic cylinder piston need satisfy the operating mode condition that stretches out fast, system control unit and signal processor output signal control first high speed ooff valve 501 and second high speed ooff valve group 502 open, control third high speed ooff valve group 503 and fourth high speed ooff valve group 504 simultaneously and close, the system switches over to differential fast-forward mode, has realized flow regeneration, and then has improved the work efficiency of pneumatic cylinder 6.
In one embodiment, as shown in fig. 1 and 2, the hydraulic cylinder displacement control process includes: in the invention, the hydraulic cylinder 6 adopts a position-pressure combined control method in a working state, when a piston rod is pushed out, a rodless cavity 601 of the hydraulic cylinder adopts position closed-loop control, and a rod cavity 603 of the hydraulic cylinder adopts pressure closed-loop control. The detailed control process is as follows: the system state control unit 10 receives a displacement command of the piston rod and a pressure command of the rod cavity, and the displacement command signal determines the movement direction and the position of the piston rod. The displacement deviation signal and the pressure deviation signal are obtained by comparing the position of the piston rod and the pressure of the rod cavity in the initial state respectively. Further, the displacement deviation signal is received by the flow-rotation speed calculation unit 901, the rotation speed of the servo motor 1 is calculated by a pre-embedded algorithm, the rotation speed signal is transmitted to the speed gradient selection unit 902, so that a proper rotation speed is selected and output to the servo motor 1, meanwhile, the rotation speed of the servo motor 1 is received by the speed encoder 904 and then fed back to the servo driver, and the servo driver completes closed-loop control on the rotation number of the servo motor 1. In this process, the displacement deviation detecting unit 907 also receives the displacement deviation command and determines the state of the piston rod, and if the piston rod is in a push stroke and the displacement deviation is greater than or equal to a deviation determination value (for example, the deviation determination value is set to 5mm), the differential state control unit sends a corresponding PWM signal to the high-speed switch valve blocks 501 and 502 to realize differential fast forward. If the piston rod is in return stroke or the displacement deviation is smaller than the deviation judgment value, the load independent control unit sends out corresponding signals to control the four high-speed switch valves to realize slow feeding. Meanwhile, the displacement sensor 7 feeds back the piston rod displacement to the system state control unit 10, continues to perform deviation detection and system state selection, and works in a circulating mode until the displacement reaches a set value and is not changed any more.
In one embodiment, as shown in fig. 1 and 2, the pressure control process of the hydraulic cylinder 6 includes: the pressure can be controlled while the piston of the hydraulic cylinder 6 is positioned, the pressure deviation signal is directly input into the load independent control unit to be processed and then output PWM signals, the opening and closing time of each high-speed switch valve 5 is controlled, the pressure of the rod cavity 603 is adjusted, the pressure feedback channel selects the pressure value of the corresponding sensor and feeds the pressure value back to the system state control unit 10 for next comparison until the pressure value of the rod cavity 603 reaches a set value and is not changed. When the piston rod retracts, the principle is basically consistent with that of the method, and only the pressure feedback channel needs to select and feed back the pressure value of the rodless cavity 601 of the hydraulic cylinder, so that displacement and pressure control is realized.
By combining the control modes, the invention can monitor the real-time state of the system and change the output flow of the hydraulic pump 2 and the opening and closing time of the high-speed switch valve 5 in the working process, thereby realizing the accurate control of the action of the hydraulic cylinder 6.
In one embodiment, as shown in fig. 1 and 2, the high-speed switching valve 5 can realize precise adjustment of the opening and closing time under the control of the PWM signal. Meanwhile, the addition of the load independent technology enables the oil inlet and the oil return paths of the hydraulic cylinder 6 to realize flow regulation, realizes series composite throttling speed regulation, increases the speed rigidity and stability, and can be widely popularized in application to engineering machinery.
In one embodiment, as shown in fig. 1 and fig. 2, the rotation speed of the servo motor 1 can be controlled by an embedded speed gradient algorithm, the control unit 10 receives the signal of the working position of the hydraulic cylinder 6, and by comparing and selecting the rotation speed value which is not lower than and closest to the flow rate required by the system in the rotation speed gradient and driving the bidirectional quantitative hydraulic pump 2 to output pressure and flow rate, and the valve port regulation of the high-speed switch valve 5 is combined to realize accurate control of the output flow rate, thereby ensuring the reliability of the control on the premise of reducing the overflow loss of the system. Meanwhile, the energy accumulator 3 finishes the recovery and release processes of system energy while absorbing and discharging oil, and the energy-saving effect is achieved.
In the invention, the load port independent control technology utilizes double valve cores or multiple valve cores, thereby removing the linkage between the inlet and the outlet of the actuating element, leading the speed control of the system to be more stable and accurate by the oil inlet and return series composite throttling speed regulation, and improving the matching property of the equipment. The high-speed switch valve is a novel digital electro-hydraulic conversion control element, and has the advantages of simple structure, low price, small pressure loss, low energy consumption, insensitivity to pollution, reliable work, higher response speed, small repeated error, high working precision and the like. Therefore, compared with the traditional electro-hydrostatic actuator, the electro-hydrostatic actuator system integrating the high-speed switch valve and the load independent technology can better meet the requirements of modern industry on multiple degrees of freedom, high automation and high control precision.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, the appended claims are intended to be construed to include preferred embodiments and all such changes and/or modifications as fall within the scope of the invention, and all such changes and/or modifications as are made to the embodiments of the present invention are intended to be covered by the scope of the invention.
Claims (9)
1. A digital electro-hydrostatic actuator system, comprising:
the servo motor is connected with the hydraulic pump;
the high-speed switch valve group is connected with the hydraulic pump;
the hydraulic cylinder is connected with the high-speed switch valve bank, and a piston rod of the hydraulic cylinder is connected with a load;
a signal processor which receives signals and parameters of the sensor; and
a system state control unit which is connected with the signal processor and controls the actions of the servo motor and the high-speed switch valve group according to the feedback signal or parameter information so as to form differential control, load independent control and system displacement and pressure control,
the high-speed switch valve group comprises a first high-speed switch valve, a second high-speed switch valve, a third high-speed switch valve and a fourth high-speed switch valve, and the first high-speed switch valve is arranged between a high-pressure oil port of the bidirectional quantitative hydraulic pump and a rodless cavity of the single-rod hydraulic cylinder; the second high-speed switch valve is arranged between a rod cavity of the single-rod hydraulic cylinder and a high-pressure oil port of the bidirectional quantitative hydraulic pump; the third high-speed switch valve is arranged between the rodless cavity of the single-rod hydraulic cylinder and the oil filling port of the bidirectional quantitative hydraulic pump; the fourth high-speed switch valve is arranged between a rod cavity of the single-rod hydraulic cylinder and an oil filling port of the bidirectional quantitative hydraulic pump, in the process of load independent control of the digital electro-hydrostatic actuator system, the high-speed switch valve group can be controlled according to a PWM (pulse-width modulation) instruction signal output by the signal processor to enable the flow ratio of the high-speed switch valve group to be equal to the area ratio of a rodless cavity and a rod cavity of the hydraulic cylinder, so that pressure pulsation caused by the flow imbalance characteristic of the asymmetric hydraulic cylinder is restrained, and the hydraulic cylinder adopts a position-pressure combined control method in a working state.
2. The digital electro-hydrostatic actuator system of claim 1, further comprising pressure protection valves, wherein the pressure protection valves comprise a first pressure protection valve, a second pressure protection valve and a third pressure protection valve, wherein an oil inlet of the first pressure protection valve is communicated with the high-pressure oil port of the pump, and an oil outlet of the first pressure protection valve is communicated with the oil charge port of the hydraulic pump; an oil inlet of the second pressure protection valve is communicated with a rodless cavity of the hydraulic cylinder, and an oil outlet of the second pressure protection valve is communicated with a system oil return path; an oil inlet of the third pressure protection valve is communicated with a rod cavity of the hydraulic cylinder, and an oil outlet of the third pressure protection valve is communicated with a system oil return circuit.
3. The digital electro-hydrostatic actuator system of claim 2, wherein the first pressure protection valve has a set pressure that is higher than the second and third pressure protection valves.
4. The digital electro-hydrostatic actuator system of any one of claims 1-3, further comprising an accumulator connected to a main system oil return line, the accumulator being connected to an oil charge port of the hydraulic pump.
5. The digital electro-hydrostatic actuator system of claim 4, wherein a first pressure sensor is coupled to an oil inlet and outlet of the accumulator; a second pressure sensor is connected to an oil inlet and outlet path of a rod cavity of the hydraulic cylinder; a third pressure sensor is connected to an oil inlet and outlet path of the rodless cavity of the hydraulic cylinder; and a hydraulic cylinder piston rod of the hydraulic cylinder is connected with a displacement sensor.
6. The digital electro-hydrostatic actuator system according to claim 5, wherein a high-pressure oil port of the bidirectional quantitative hydraulic pump is communicated with a first high-speed switch valve, an oil charging port of the bidirectional quantitative hydraulic pump is communicated with an energy accumulator, and reversing action of the hydraulic cylinder is realized by alternately opening and closing the first high-speed switch valve and a second high-speed switch valve; when the first high-speed switching valve and the second high-speed switching valve are simultaneously opened and the third high-speed switching valve and the fourth high-speed switching valve are simultaneously closed, the system becomes a differential state.
7. The digital electro-hydrostatic actuator system of claim 6, wherein the signal processor comprises a displacement-rotation speed calculation unit, a speed gradient selection unit, a servo driver, a speed encoder, a differential state control unit, a load independent control unit, a displacement deviation detection unit, a signal acquisition and processing unit, and a system state monitoring unit.
8. The digital electro-hydrostatic actuator system of claim 7, wherein the signal acquisition and processing unit is configured to acquire a rotation speed signal of the servo motor, an energy storage device pressure signal, a hydraulic cylinder rod cavity pressure signal, a hydraulic cylinder rod-free cavity pressure signal, and a hydraulic cylinder piston rod displacement signal output by the speed encoder, the first pressure sensor, the second pressure sensor, the third pressure sensor, and the displacement sensor, and the processed signals are received by the system state monitoring unit and stored in the system state control unit, and after performing difference processing in the control unit, displacement and pressure deviation are determined respectively, and a next command is executed.
9. The digital electro-hydrostatic actuator system of claim 8, wherein the servo driver outputs a driving signal to control the rotation of the servo motor, and the rotation speed of the servo motor is received by the speed encoder and fed back to the servo driver, so that the servo driver performs precise closed-loop control on the rotation speed of the servo motor and drives the bidirectional quantitative hydraulic pump to output pressure and flow; the high-speed switch valve controls the opening and closing time of the valve port according to the PWM command signal output by the signal processor, so that the pressure and flow control of oil output by the valve port are realized; the pressure and the flow of the oil output by the bidirectional quantitative hydraulic pump and the high-speed switch valve jointly influence the pressure and the flow of a rodless cavity and a rod cavity of the hydraulic cylinder, and finally the displacement of a piston rod of the hydraulic cylinder is controlled.
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| CN111622996B (en) * | 2020-04-27 | 2022-05-24 | 江苏科技大学 | Heterogeneous multi-valve parallel drive electro-hydraulic servo system and control method |
| CN112727821B (en) * | 2021-01-05 | 2023-10-27 | 中冶南方连铸技术工程有限责任公司 | Single-rod electrohydraulic direct-drive servo cylinder device |
| CN113417896B (en) * | 2021-06-04 | 2022-05-10 | 燕山大学 | Pump-controlled hydraulic system of press machine and control method thereof |
| CN113251013B (en) * | 2021-06-07 | 2022-08-12 | 中冶赛迪技术研究中心有限公司 | Electro-hydraulic direct-drive servo closed differential control driving system of stepping lifting mechanism |
| CN113534658A (en) * | 2021-08-25 | 2021-10-22 | 广东电网有限责任公司广州供电局 | Double closed-loop control system and method |
| CN116480660A (en) * | 2023-05-25 | 2023-07-25 | 华东交通大学 | Flow self-balancing closed pump control system adopting four electromagnetic valves to actively and independently control oil paths |
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