CN105422521B - A servo pump controlled hydraulic linear drive system and control method - Google Patents

Abstract

The invention discloses a hydraulic linear drive system based on control of servo pumps, and a control method. A rodless cavity and a rod cavity of a hydraulic cylinder of the system are connected with hydraulic pumps A and B respectively, and the two pumps are controlled by servo drivers A and B, and servo motors A and B respectively; a movement control unit is connected with the two servo drivers; pressure sensors A and B on pipelines of the rodless cavity and the rod cavity are connected with the two servo drivers respectively; and a displacement sensor on a push rod of the hydraulic cylinder is connected to the movement control unit. The control method is that when the motor and the pump at the side A positively run, the push rod moves forwards, and meanwhile, the motor and the pump at the side B reversely run, and the rod cavity drains; conversely, the motor and the pump at the side B positively run, and the motor and the pump at the side A reversely run. Process data and control requirements are stored in the movement control unit, running mode instructions, and speed and pressure setting instructions of the two servo drivers are obtained according to the process data, the control requirements and the current displacement signal of the push rod, and the speed and the position of the push rod are accurately controlled. According to the invention, high response frequency and precise position control are realized; and the system is simple in structure, low in cost, and high in reliability.

Description

A servo pump controlled hydraulic linear drive system and control method

technical field

The present invention relates to a hydraulic transmission device, specifically a servo pump-controlled hydraulic linear drive system and a control method. In the present invention, two servo motors each drive an oil pump to cooperate to control the power output of the hydraulic cylinder and realize the control of linear reciprocating motion. .

Background technique

It is a common mechanical structure to control linear motion and power output through a hydraulic cylinder. The traditional hydraulic linear drive system is a motor-driven hydraulic pump that runs continuously. The oil circuit composed of various valve groups, sensors and pipelines controls the flow of hydraulic oil. Flow rate, pressure, and then the drive of the hydraulic cylinder. When it is necessary to control the moving speed of the hydraulic cylinder, a proportional directional valve or a proportional directional servo valve is required to adjust the liquid rate entering the hydraulic cylinder; when it is necessary to control the driving force of the hydraulic cylinder, it is necessary to control the overflow pressure of the overflow valve or according to the pressure sensor Feedback and through the proportional pressure valve or proportional pressure servo valve to control the pressure of the liquid entering the hydraulic cylinder, thereby controlling the thrust of the hydraulic cylinder.

This type of traditional hydraulic linear drive system has the following shortcomings: 1. The motor driving the hydraulic pump must run continuously. Even when the hydraulic cylinder movement does not need to be adjusted and controlled, the motor cannot be stopped. It returns to the fuel tank through the valve group again, wasting electric energy. Especially when the hydraulic cylinder outputs thrust but the displacement of the piston is very small or the displacement speed is very low, the high-pressure throttling increases the power consumption of the motor and wastes electric energy; The aging of the seal is accelerated, and the failure rate increases; 3. When the hydraulic oil reciprocates between the rod chamber and the rodless chamber of the hydraulic cylinder, various valve actions need to be controlled, and overflow and liquid filling actions are continuously generated, which increases the System loss, valve failure rate is relatively high; 4. In fast and precise control, it is necessary to use P/Q valve (pressure flow control valve) or servo valve to participate in the control, especially the servo valve is expensive and difficult to maintain, resulting in system failure. The purchase, use and maintenance costs of the equipment have increased significantly; 5. Since the mechanical actions of various valves take a long time to complete, it is impossible to further speed up the switching of various actions in the oil circuit, which directly affects the working rhythm of the equipment.

Contents of the invention

The object of the present invention is to address the deficiencies in the prior art, and propose a servo pump-controlled hydraulic linear drive system. The liquid outlets of the two hydraulic pumps A and B are respectively connected to the rodless cavity and the rod cavity of the hydraulic cylinder. The two servo motors of B are respectively connected to the hydraulic pumps of A and B, and the two servo drivers of A and B connected to the motion control unit control the two servo motors of A and B respectively, and are installed in the rodless chamber and the rod chamber of the hydraulic cylinder The signals of the two pressure sensors A and B inside are respectively connected to the two servo drivers A and B, and the signal end of the displacement sensor installed on the push rod of the hydraulic cylinder is connected to the motion control unit.

Another object of the present invention is to propose a control method for the above-mentioned servo pump-controlled hydraulic linear drive system. The A and B servo drivers drive the A and B hydraulic pumps respectively, and one of the servo motors and the connected hydraulic pump run forward, and the other servo motor The motor and the connected hydraulic pump run in reverse to relieve pressure. According to the motion position and speed control requirements of the push rod and the current displacement signal of the push rod, the motion control unit calculates and obtains the operation mode command, speed setting command and pressure setting command of the second servo drive, and sends them to the A servo drive and the B servo drive respectively. driver. The control modes include speed closed-loop mode and speed-pressure double closed-loop mode. The movement mode of the hydraulic cylinder is divided into three types: forward mode, return mode and high-speed reciprocating mode, to realize the high-speed and precise reciprocating motion of the hydraulic cylinder push rod.

A servo pump-controlled hydraulic linear drive system designed by the present invention includes a hydraulic cylinder, two hydraulic pumps, a liquid filling valve, an overflow valve, a piston connected to a push rod, and a hydraulic cylinder cavity divided into a rod cavity and a rodless cavity. The pipeline is connected to the liquid inlet and the liquid storage tank of the two hydraulic pumps, and the pipeline is respectively connected to the liquid outlet of the two hydraulic pumps and the rod chamber and the rodless chamber of the hydraulic cylinder. The two motors are respectively connected and drive two A hydraulic pump has a liquid filling valve and an overflow valve on the pipeline; the rodless chamber of the hydraulic cylinder of the present invention is connected with the liquid outlet of the A hydraulic pump, and the rod chamber of the hydraulic cylinder is connected with the liquid outlet of the B hydraulic pump. The liquid inlet ends of the A hydraulic pump and the B hydraulic pump are connected to the liquid storage tank. The A servo motor is connected to the A hydraulic pump, and the A servo driver is connected to control the A servo motor; the B servo motor is connected to the B hydraulic pump, and the B servo driver is connected to control the B servo motor. The control end of the motion control unit is connected with A and B servo drives. Installed on the pipe connecting the rodless chamber of the hydraulic cylinder and the liquid end of the hydraulic pump A. The signal output end of the A pressure sensor is connected to the A servo drive; installed on the pipe connecting the rod chamber of the hydraulic cylinder and the liquid end of the hydraulic pump B. The signal output end of the sensor is connected to the B servo driver. The displacement sensor is installed on the push rod of the hydraulic cylinder, and its signal output end is connected to the input end of the motion control unit.

The motion control unit is a central processor equipped with a communication interface and a man-machine interface.

The pipeline is connected to the liquid storage tank and the rodless chamber of the hydraulic cylinder through the liquid filling valve. The liquid filling valve is a one-way valve. Otherwise the valve remains closed. When the push rod of the hydraulic cylinder quickly moves to the direction of the rod chamber, the pressure of the rodless chamber drops rapidly, and the filling valve automatically opens to replenish liquid to the rodless chamber.

A hydraulic pump’s liquid outlet is connected to the hydraulic cylinder’s non-rod cavity, and the A relief valve is connected to the pipeline, and the B hydraulic pump’s liquid end is connected to the hydraulic cylinder’s rod chamber, and the pipeline connected to the B relief valve, A and B relief valves The liquid outlets are all connected to the liquid storage tank. When the liquid pressure in the pipeline exceeds the upper limit of the output pressure of the connected pump, it will be released from the connected overflow valve for pressure limiting protection.

One of the schemes of the present invention is to install a power-off brake on the shaft of the B servo motor. When the system fails to protect the shutdown or power failure, the power-off brake locks the shaft of the B servo motor, and the B hydraulic pump connected to the B servo motor stops rotating. , to prevent the push rod of the hydraulic cylinder and the piston workpiece installed on it from falling rapidly due to gravity, so as to ensure the safety of the system equipment.

In another scheme of the present invention, the B servo motor is a three-phase permanent magnet synchronous servo motor, and its three-phase winding is equipped with a power-off normally closed contactor or a power-off normally closed relay. The winding is short-circuited by a de-energized normally closed contactor or a de-energized normally closed relay. When the push rod of the hydraulic cylinder and the piston workpiece installed on it are pulled down by gravity, the hydraulic oil pushes the B hydraulic pump to rotate in the reverse direction, thereby driving the rotor of the B servo motor to rotate in the reverse direction, which is caused by the short circuit of the three-phase winding of the B servo motor Damping torque, the B hydraulic pump can only rotate slowly, so that the push rod and piston of the hydraulic cylinder slowly slide to the mechanical limit position to protect the safety of the system equipment.

In another solution of the present invention, a protection valve that automatically closes when the power is off is installed on the pipeline connecting the rod cavity of the hydraulic cylinder to the B hydraulic pump. The hydraulic oil in the cavity will not leak out, which can prevent the push rod of the hydraulic cylinder from falling due to the gravity of the workpiece installed on it, and play a role of safety protection.

The control method of the servo pump-controlled hydraulic linear drive system proposed by the present invention is that the A and B servo drivers respectively drive the respectively connected A and B servo motors, when the A servo motor is running forward, and the A hydraulic pump connected to it is running forward, The A hydraulic pump supplies pressure liquid to the rodless chamber of the hydraulic cylinder, the piston of the hydraulic cylinder moves in the direction of the rod chamber, and the push rod outputs power; at the same time, the B servo motor and the B hydraulic pump connected to it run in reverse, The rod cavity of the hydraulic cylinder releases liquid through the B hydraulic pump. Conversely, when the B servo motor and the B hydraulic pump are running forward, the B hydraulic pump supplies pressure liquid to the rod chamber of the hydraulic cylinder, and the piston of the hydraulic cylinder moves toward the rod chamber. At the same time, the A servo motor and the A hydraulic pump reverse Running in the opposite direction, the rodless chamber of the hydraulic cylinder is depressurized by the A hydraulic pump.

The motion control unit stores the process data of the system and the relationship data between the push rod displacement signal and the control commands of A and B servo drivers under different control modes. The motion control unit accepts the control requirements input by the man-machine interface, and the control requirements are based on the work requirements Set the speed corresponding to the movement of the hydraulic cylinder push rod to a certain moment or the corresponding speed when the push rod moves to a certain position, and the motion control unit performs logical judgment and position closed loop according to the control requirements and the current displacement signal of the push rod received from the displacement sensor Operation mode command, speed setting command and pressure setting command of A and B servo drivers are obtained, and sent to A servo driver and B servo driver respectively. Thereby adjusting the rotation of 2 servo motors and 2 hydraulic pumps, and then adjusting the position and speed of the push rod, so as to realize the precise speed control and position control of the push rod.

The control modes include speed closed-loop mode and speed-pressure double closed-loop mode.

The A and B servo drives receive the speed setting command or the speed and pressure setting command of the motion control unit, as well as the control mode command, and respectively receive the current pressure feedback from the rodless chamber or the rod chamber of the hydraulic cylinder of the A and B pressure sensors value. When the control mode instruction of the motion control unit is the speed closed-loop mode, the speed closed-loop of the servo driver controls the connected servo motor according to the speed setting instruction of the motion control unit, and drives it to run completely according to the speed setting instruction of the motion control unit; When the control mode instruction of the motion control unit is speed and pressure double closed-loop mode, the pressure closed-loop of the servo driver controls the rotation speed of the connected servo motor according to the pressure setting instruction of the motion control unit and the current pressure feedback value. If the current pressure feedback value reaches or exceeds the set pressure value, then reduce the forward speed setting of the servo motor coaxial with the hydraulic pump that is pumping in the forward direction or increase the reverse speed setting of the servo motor coaxial with the hydraulic pump that is draining in the reverse direction If the current pressure feedback value is less than the set pressure value, then raise the forward speed setting of the servo motor coaxial with the hydraulic pump that is pumping liquid in the forward direction or reduce the servo motor coaxial with the hydraulic pump that is draining liquid in the reverse direction The reverse speed setting of the motor, the current servo motor speed setting value determined by the servo drive pressure closed loop is compared with the speed setting command from the motion control unit, and the smaller absolute value of the two values is taken as the speed command of the servo drive Send to the connected servo motor for execution.

According to the above control method, the high-speed and precise reciprocating motion of the hydraulic cylinder push rod can be realized. The specific push rod motion modes are divided into three types: forward mode, return mode and high-speed reciprocating mode.

Ⅰ. Way forward

The forward mode refers to the movement of the hydraulic cylinder push rod to the direction of the rod cavity, which is divided into two types: fast forward mode (empty travel) and working mode.

Ⅰ-1. Fast forward mode

At this time, the bottom end of the hydraulic cylinder push rod does not bear the resistance of the workpiece, and the movement speed is usually high to improve work efficiency. The motion control unit sends an instruction to the B servo driver connected to the rod chamber side of the hydraulic cylinder to run in the speed closed-loop mode, and sends out a speed setting instruction. Driven by the B servo driver, the B servo motor and the B hydraulic pump react at the set speed. To rotate, there is liquid leakage in the rod cavity. At the same time, the motion control unit sends an instruction to the A servo driver connected to the rodless chamber side of the hydraulic cylinder to run in the speed closed-loop mode, and sends out a speed setting instruction. Driven by the A servo driver, the A servo motor and the A hydraulic pump operate at the set speed. Forward running, supply pressure liquid into the rodless cavity, and push the push rod of the hydraulic cylinder forward at a predetermined speed.

When the weight of the tooling on the push rod of the hydraulic cylinder exerts enough pressure on the liquid in the rod chamber and the downstream pipeline to make the B hydraulic pump on the side of the rod chamber in the reverse and pressure relief state, if the A hydraulic pump on the rodless chamber side And the rotation speed of the A servo motor cannot meet the oil supply requirements when the push rod advances, and the hydraulic pressure on the side of the rodless chamber decreases or even becomes negative pressure. The liquid valve is automatically opened to replenish liquid to the rodless cavity. The maximum speed of the fast forward mode is determined by the maximum reverse speed of the B hydraulic pump and the B servo motor on the side of the rod chamber.

When the fast-forward mode ends and the work-forward mode is changed, the motion control unit sends a reduced speed setting value or a speed lock zero signal to the B servo driver, so that the speed of the B servo motor and the B hydraulic pump decreases, and the leakage of the rod chamber The pressure slows down or stops, at this time, the pressure in the rodless chamber rises, and the filling valve automatically closes.

Ⅰ-2. Working method

At this time, the bottom end of the push rod of the hydraulic cylinder bears the resistance of the workpiece, and its movement overcomes the resistance and does work.

The motion control unit issues an instruction to the A servo driver on the side of the rodless cavity to run in the speed closed-loop mode, and sends out a speed setting instruction. Driven by the A servo driver, the A servo motor and the A hydraulic pump follow the speed setting instruction of the motion control unit, That is to push the push rod of the hydraulic cylinder forward according to the predetermined working speed; at the same time, the motion control unit sends an instruction to the B servo driver on the side of the rod chamber to run in the speed and pressure double closed-loop mode, and sends out the reverse speed setting and pressure setting Command, B servo driver determines the speed of B servo motor according to the speed and pressure double closed-loop mode according to the speed setting command and pressure setting command of the motion control unit, the pressure setting command and the current pressure feedback value of the B pressure sensor, and the B hydraulic pump reverses to release pressure.

Ⅱ. Return method

The return stroke means that the push rod of the hydraulic cylinder moves in the direction of the rodless cavity. The motion control unit sends an instruction to the B servo driver on the side of the rod cavity to run in the speed closed-loop mode, and sends out a speed setting instruction. Driven by the B servo driver, the B servo motor and the B hydraulic pump run forward at a predetermined speed to push the piston. The push rod returns to the direction of the rodless chamber; at the same time, the motion control unit sends an instruction to the A servo driver on the side of the rodless chamber to run in the double closed-loop mode of speed and pressure, and sends a reverse speed setting and pressure setting instruction, and the A servo driver According to the speed setting command and pressure setting command of the motion control unit and the current pressure feedback value of the A pressure sensor, the speed of the A servo motor is determined according to the speed and pressure double closed-loop mode, and the A hydraulic pump reverses and discharges liquid.

In the return mode and the forward mode, the motion control unit adjusts the control mode and speed command of the A and B servo drives in real time according to the control requirements and the displacement feedback value of the displacement sensor, and controls the speed of the A and B servo motors, so as to realize the hydraulic cylinder push rod. Precise control of position and speed.

Ⅲ. High-speed reciprocating mode

The high-speed reciprocating mode is the high-speed repetition of the above-mentioned working mode and return mode. At this time, there is no fast-forward mode, and the hydraulic cylinder is in the reciprocating motion state of "working-returning-working...". The motion control unit predetermines the arrival position and/or arrival time of the push rod as the judgment basis for the end of the work progress or the end of the return journey. The motion control unit judges the end of the work progress or the end of the return journey according to the displacement signal and/or time of the displacement sensor, that is, transfers to the return journey way or way of working. Since the response frequency of the servo motor driven by the servo driver is very high, it can realize fast forward and reverse switching. The servo drive device of this system can realize high-precision and high-repeatability reciprocating motion of more than ten to tens of hertz.

Compared with the prior art, the beneficial effects of a servo pump-controlled hydraulic linear drive system and control method of the present invention are as follows: 1. Two servo motors drive two oil pumps to act in concert to control the power output of the hydraulic cylinder and realize linear reciprocation. Precise control of movement; 2. The response frequency of servo motor and servo driver is high, so the system can achieve a response frequency of up to tens to tens of Hz and position control with precision of tens of microns or even microns; 3. The hydraulic pressure in the system pipeline The valves are only two overflow valves for hydraulic protection and one one-way filling valve for liquid replenishment, without solenoid valves, P/Q valves or servo valves. The system is simple in structure, low in cost and high in reliability.

Description of drawings

Fig. 1 is a schematic structural diagram of an embodiment of the servo pump-controlled hydraulic linear drive system.

Marks in the figure: 1. Liquid filling valve (YF); 2. Hydraulic cylinder; 3. A relief valve (AF); 4. A pressure sensor (AP); 5. A hydraulic pump (AU); 6. A servo Motor (AM); 7. A Servo Driver (AS); 8. B Hydraulic Pump (BU); 9. B Servo Motor (BM); 10. B Servo Driver (BS); 11. B Pressure Sensor (BP); 12. Protection valve; 13. B overflow valve (BF); 14. Displacement sensor.

detailed description

The technical solutions of the present invention will be further described below in conjunction with the embodiments shown in the accompanying drawings.

Embodiment of Servo Pump Control Hydraulic Linear Drive System

The embodiment of the servo pump-controlled hydraulic linear drive system is shown in Figure 1. The solid line connecting the components in the figure indicates the oil pipeline connecting the components, and the dotted line indicates the signal line of the sensor and the control signal line of the motion control unit. The thick solid lines of the servo motor and the hydraulic pump indicate that they are coaxial. The hydraulic medium in this example is hydraulic oil, the liquid storage tank in this example is an oil tank, the hydraulic cylinder is an oil cylinder, and the hydraulic pump is an oil pump.

The piston of the hydraulic cylinder 2 is connected to the push rod, and the inner cavity of the hydraulic cylinder is divided into a rod cavity and a rodless cavity. The rod chamber of the cylinder 2 is connected with the liquid outlet of the B hydraulic pump 8 (BU shown in the figure). The liquid inlet ports of the A hydraulic pump 5 and the B hydraulic pump 8 are connected to the liquid storage tank, namely the oil tank in this example. In Figure 1, in order to avoid confusion on the drawing, multiple fuel tanks are drawn in different parts, but they are actually the same fuel tank. A servo motor 6 (shown as AM in the figure) is connected with A hydraulic pump 5, and A servo driver 7 (shown as AS in the figure) is connected to control A servo motor 6; B servo motor 9 (shown as BM in the figure) ) is connected to the B hydraulic pump 8, and the B servo driver 10 (shown as BS in the figure) is connected to control the B servo motor 9. The control end of the motion control unit is connected with the A servo driver 7 and the B servo driver 10 . Installed on the pipeline connecting the rodless chamber of hydraulic cylinder 2 and the liquid end of A hydraulic pump 5, the signal output end of A pressure sensor 4 (AP shown in the figure) is connected to the A servo driver 7; connected to the rod chamber of hydraulic cylinder 2 and The signal output end of the B pressure sensor 11 (BP shown in the figure) installed on the pipeline at the outlet of the B hydraulic pump 8 is connected to the B servo driver 10 . The displacement sensor 14 is installed on the push rod of the hydraulic cylinder, and its signal output end is connected to the input end of the motion control unit.

In this example, the motion control unit is a central processor, equipped with a communication interface and a man-machine interface.

The pipeline is connected to the oil tank and the rodless chamber of the hydraulic cylinder 2 through the filling valve 1 (YF shown in the figure). In this example, the filling valve 1 is a one-way valve. , the valve opens automatically, otherwise the valve remains closed. When the push rod of hydraulic cylinder 2 quickly moves toward the rod chamber, if the hydraulic oil pumped into the rod chamber by A hydraulic pump 5 cannot quickly fill the rod chamber inner chamber, the pressure in the rod chamber drops rapidly, and the filling valve Automatically open to add liquid to the rodless cavity.

The liquid outlet of A hydraulic pump 5 is connected to the pipeline of hydraulic cylinder 2 without the rod chamber and connected to A relief valve 3 (shown as AF in the figure), and the liquid outlet of B hydraulic pump 8 is connected to the pipe with rod chamber of hydraulic cylinder 2 The road is connected to the B relief valve 13 (shown as BF in the figure), and the liquid outlets of the A and B relief valves 3 and 13 are all connected to the oil tank.

In this example, on the pipeline connecting the rod chamber of the hydraulic cylinder 2 and the B hydraulic pump 8, a protection valve 12 (BB shown in the figure) that is automatically closed when the power is off is installed. When the system fails to protect the shutdown or power failure, the protection valve 12 can cut off the oil passage from the rod cavity of the hydraulic cylinder 2 to the B hydraulic pump 8, thereby playing a protective role.

Other protection schemes can also be used: a power-off brake is installed on the shaft of the B servo motor 9, and when the system fails to protect the shutdown or power failure, the power-off brake locks the shaft of the B servo motor.

Alternatively, the B servo motor 9 is a three-phase permanent magnet synchronous servo motor, and its three-phase winding is equipped with a power-off normally closed contactor or a power-off normally closed relay. The normally closed contactor or the normally closed relay is shorted.

Embodiment of the control method of the servo pump-controlled hydraulic linear drive system

This embodiment is the control method of the above embodiment of the servo pump-controlled hydraulic linear drive system. The A servo driver 7 and the B servo driver 10 respectively drive the A servo motor 6 and the B servo motor 9 connected respectively. When the A servo motor 6 runs forward, the A hydraulic pump 5 connected to it runs forward, and the A hydraulic pump 5 The pressure liquid is provided in the rodless cavity of the hydraulic cylinder 2, the piston of the hydraulic cylinder 2 moves in the direction of the rod cavity, and the push rod outputs power; at the same time, the B servo motor 9 and the B hydraulic pump 8 connected to it run in reverse, The rod chamber of the hydraulic cylinder 2 discharges liquid through the B hydraulic pump 8 . Conversely, when the B servo motor 9 and the B hydraulic pump 8 are running forward, the B hydraulic pump 8 supplies pressure liquid to the rod chamber of the hydraulic cylinder 2, and the piston of the hydraulic cylinder 2 moves toward the rod chamber. At the same time, the A servo motor 6 and A hydraulic pump 5 run in reverse, and the rodless cavity of hydraulic cylinder 2 is depressurized by A hydraulic pump 5 .

The motion control unit stores the process data of the system, the relationship data between the push rod displacement signal and the control commands of A and B servo drives under different control modes, and the motion control unit accepts the control requirements input by the man-machine interface, and the control requirements are based on the work requirements Set the corresponding speed when the hydraulic cylinder push rod moves to a certain moment or the corresponding speed when the push rod moves to a certain position, and the motion control unit performs logical judgment and position according to the control requirements and the current displacement signal of the push rod received from the displacement sensor 14. The closed-loop operation obtains the operation mode instructions, speed setting instructions and pressure setting instructions of the A and B servo drivers, and sends them to the A servo driver 7 and the B servo driver 10 respectively.

The control modes include speed closed-loop mode and speed-pressure double closed-loop mode.

The A and B servo drivers 7, 10 receive the speed setting command or the speed and pressure setting command of the motion control unit, as well as the control mode command, and receive the rodless chamber of the hydraulic cylinder 2 from the A and B pressure sensors 4, 11 respectively Or the current pressure feedback value of the rod cavity. When the control mode instruction of the motion control unit is the speed closed-loop mode, the speed closed-loop of the servo driver controls the connected servo motor according to the speed setting instruction of the motion control unit, and drives it to run completely according to the speed setting instruction of the motion control unit; When the control mode command of the control unit is speed and pressure double closed loop mode, the pressure closed loop of the servo driver controls the speed of the connected servo motor according to the pressure setting command of the motion control unit and the current pressure feedback value. If the current pressure feedback value reaches or exceeds To set the pressure value, reduce the forward speed setting of the servo motor coaxial with the hydraulic pump that is pumping oil in the forward direction or increase the reverse speed setting of the servo motor coaxial with the hydraulic pump that is draining oil in the reverse direction; If the current pressure feedback value is less than the set pressure value, increase the forward rotation speed setting of the servo motor coaxial with the hydraulic pump that is pumping oil in the forward direction or decrease the servo motor coaxial with the hydraulic pump that is draining oil in the reverse direction Reverse speed setting; compare the current servo motor speed setting value determined by the servo drive pressure closed-loop with the speed setting command from the motion control unit, and take the smaller absolute value of the two values as the speed command of the servo drive and send it to The connected servo motor executes.

According to the above control method, the high-speed and precise reciprocating motion of the hydraulic cylinder push rod can be realized. The specific push rod motion modes are divided into three types: forward mode, return mode and high-speed reciprocating mode.

Ⅰ. Way forward

The forward mode refers to the movement of the hydraulic cylinder push rod to the direction of the rod cavity, which is divided into two types: fast forward mode (empty travel) and working mode.

Ⅰ-1. Fast forward mode

At this time, the bottom end of the push rod of the hydraulic cylinder 2 does not bear the resistance of the workpiece, and the motion control unit sends an instruction to the B servo drive 10 connected to the rod cavity side of the hydraulic cylinder 2 to operate in the speed closed-loop mode, and sends a speed setting instruction. Driven by the B servo driver 10, the B servo motor 9 and the B hydraulic pump 8 reverse at a set speed, and the rod chamber leaks liquid. At the same time, the motion control unit sends an instruction to the A servo driver 7 connected to the rodless chamber side of the hydraulic cylinder 2 to run in the speed closed-loop mode, and sends a speed setting instruction, and the A servo motor 6 and the A hydraulic pump are driven by the A servo driver 7 5. Run forward at the set speed, supply pressure liquid into the rodless cavity, and push the push rod of the hydraulic cylinder 2 forward at the predetermined speed.

When the pressure in the rodless chamber of the hydraulic cylinder 2 is lower than the side pressure of the liquid storage tank, the filling valve 1 connected to the rodless chamber is automatically opened to replenish the rodless chamber. The maximum speed of the fast-forward mode is determined by the maximum reverse speed of the B hydraulic pump 8 and the B servo motor 9 on the rod chamber side.

When the fast-forward mode ends and the work-forward mode is switched, the motion control unit sends a reduced speed setting value or a speed lock zero signal to the B servo driver 10, so that the speeds of the B servo motor 9 and the B hydraulic pump 8 decrease, and the rod The pressure relief of the cavity slows down or stops. At this time, the pressure of the rodless cavity rises, and the filling valve 1 automatically closes.

Ⅰ-2. Working method

At this time, the bottom end of the hydraulic cylinder 2 push rod bears the resistance of the workpiece.

The motion control unit issues an instruction to the A servo driver 7 on the side of the rodless cavity to run in the speed closed-loop mode, and sends out a speed setting instruction. Driven by the A servo driver 7, the A servo motor 6 and the A hydraulic pump 5 follow the speed of the motion control unit. Set the instruction and push the push rod of the hydraulic cylinder 2 forward according to the predetermined working speed; at the same time, the motion control unit issues an instruction to the B servo driver 10 on the side of the rod chamber to operate in the double closed-loop mode of speed and pressure, and sends a reverse speed setting Constant and pressure setting instructions, B servo driver 10 determines the speed of B servo motor 9 according to the speed and pressure double closed-loop mode according to the speed setting instruction of the motion control unit, the pressure setting instruction and the current pressure feedback value of B pressure sensor 11, B The hydraulic pump 8 reverses to relieve pressure.

Ⅱ. Return method

The return stroke means that the push rod of the hydraulic cylinder 2 moves in the direction of the rodless chamber.

The motion control unit issues an instruction to the B servo driver 10 on the side of the rod cavity to run in the speed closed-loop mode, and sends a speed setting instruction. Driven by the B servo driver 10, the B servo motor 9 and the B hydraulic pump 8 move forward at a predetermined speed. Run, push the piston push rod to return to the direction of the rodless chamber; at the same time, the motion control unit sends an instruction to the A servo drive 7 on the side of the rodless chamber to run in the speed and pressure double closed-loop mode, and sends reverse speed setting and pressure setting Command, A servo driver determines the speed of A servo motor according to the speed and pressure double closed-loop mode according to the speed setting command and pressure setting command of the motion control unit, the pressure setting command and the current pressure feedback value of the A pressure sensor, and the A hydraulic pump reverses to drain oil.

Ⅲ. High-speed reciprocating mode

The high-speed reciprocating mode means that the hydraulic cylinder 2 is in the reciprocating motion state of "working forward - return - working forward...". The motion control unit predetermines the arrival position and/or arrival time of the push rod as the judgment basis for the end of the work progress or the end of the return journey. Return way or working way.

In this example, the hydraulic linear drive system realizes the motion control of the push rod through the motion control unit. According to the control requirements of the push rod of this system and the displacement data from the displacement sensor 14, the motion control unit obtains the speed setting, pressure setting and operation mode command of the A and B servo drives through calculation, and sends them to the A servo drive 7 and B Servo driver 10 realizes precise control of the position and speed of the push rod.

The above-mentioned embodiments are only specific examples for further specifying the purpose, technical solutions and beneficial effects of the present invention, and the present invention is not limited thereto. Any modifications, equivalent replacements, improvements, etc. made within the disclosed scope of the present invention are included in the protection scope of the present invention.

Claims (9)

1. A servo pump-controlled hydraulic linear drive system, including a hydraulic cylinder, two hydraulic pumps, a filling valve, an overflow valve, a piston connected to a push rod, and the inner chamber of the hydraulic cylinder is divided into a rod chamber and a rodless chamber, The pipeline connects the liquid inlet and the liquid storage tank of the two hydraulic pumps, and the pipeline connects the liquid outlet of the two hydraulic pumps and the rod chamber and the rodless chamber of the hydraulic cylinder respectively, and the two motors are respectively connected and drive two hydraulic pumps. The pump has a filling valve and an overflow valve on the pipeline; it is characterized in that: The rodless chamber of the hydraulic cylinder (2) is connected with the liquid outlet of the A hydraulic pump (5), and the rod chamber of the hydraulic cylinder (2) is connected with the liquid outlet of the B hydraulic pump (8); the A hydraulic pump ( 5) The liquid inlet end of the B hydraulic pump (8) is connected to the liquid storage tank; the A servo motor (6) is connected to the A hydraulic pump (5), and the A servo driver (7) is connected to control the A servo motor (6); B The servo motor (9) is connected to the B hydraulic pump (8), and the B servo driver (10) is connected to control the B servo motor (9); the control end of the motion control unit is connected to the A servo driver (7) and the B servo driver (10) ; Installed on the connecting hydraulic cylinder (2) rodless cavity and A hydraulic pump (5) on the liquid outlet pipeline, the signal output end of A pressure sensor (4) is connected to A servo drive (7); installed on connecting hydraulic cylinder (2) ) The signal output end of the B pressure sensor (11) on the rod cavity and the B hydraulic pump (8) liquid end pipeline is connected to the B servo driver (10); the displacement sensor (14) is installed on the hydraulic cylinder (2) push rod , the signal output end of which is connected to the input end of the motion control unit; The motion control unit is a central processor equipped with a communication interface and a man-machine interface. 2. The servo pump-controlled hydraulic linear drive system according to claim 1, characterized in that: The pipeline connects the liquid storage tank and the rodless chamber of the hydraulic cylinder (2) through the filling valve (1). The filling valve (1) is a one-way valve. When the pressure is lower than the side pressure of the liquid storage tank, the filling valve (1) is automatically opened, otherwise the filling valve (1) remains closed. 3. The servo pump-controlled hydraulic linear drive system according to claim 1, characterized in that: The liquid outlet of the A hydraulic pump (5) is connected to the hydraulic cylinder (2) and the rodless cavity is connected to the A relief valve (3), and the liquid outlet of the B hydraulic pump (8) is connected to the hydraulic cylinder (2) with The pipeline of the rod cavity is connected to the B overflow valve (13), and the liquid outlets of the A overflow valve (3) and the B overflow valve (13) are connected to the liquid storage tank. 4. The servo pump-controlled hydraulic linear drive system according to claim 1, characterized in that: A power-off brake is installed on the shaft of the B servo motor (9), and when the system failure protection shutdown or power failure occurs, the power-off brake locks the shaft of the B servo motor (9). 5. The servo pump-controlled hydraulic linear drive system according to claim 1, characterized in that: The B servo motor (9) is a three-phase permanent magnet synchronous servo motor, and its three-phase winding is equipped with a power-off normally closed contactor or a power-off normally closed relay. The winding is short-circuited by a power-off normally closed contactor or a power-off normally closed relay. 6. The servo pump-controlled hydraulic linear drive system according to claim 1, characterized in that: On the pipeline connected between the rod chamber of the hydraulic cylinder (2) and the B hydraulic pump (8), a protection valve (12) that is automatically closed when the power is off is installed. When the system fails to protect the shutdown or power failure, the protection valve (12) ) automatically closes. 7. The control method of the servo pump-controlled hydraulic linear drive system according to any one of claims 1 to 6, characterized in that: The A and B servo drivers (7, 10) respectively drive the A and B servo motors (6, 9) connected respectively, and when the A servo motor (6) runs forward, the A hydraulic pump (5) connected to it is forward. The hydraulic pump (5) supplies pressure liquid to the rodless cavity of the hydraulic cylinder (2), the piston of the hydraulic cylinder (2) moves in the direction of the rod cavity, and the push rod outputs power; at the same time, the B servo motor (9) and the B hydraulic pump (8) connected to it run in reverse, and the rod chamber of the hydraulic cylinder (2) discharges liquid through the B hydraulic pump (8); otherwise, when the B servo motor (9) and the B hydraulic pressure The pump (8) runs in the forward direction, the B hydraulic pump (8) provides pressure liquid to the rod cavity of the hydraulic cylinder (2), and the piston of the hydraulic cylinder (2) moves toward the rod cavity, and at the same time, the A servo motor (6 ) and the A hydraulic pump (5) run in reverse, and the rodless cavity of the hydraulic cylinder (2) is depressurized through the A hydraulic pump (5); The motion control unit stores the process data of the system and the relationship data between the push rod displacement signal and the control commands of A and B servo drives (7, 10) under different control modes, and the motion control unit accepts the control requirements input by the man-machine interface, and the control The requirement is to set the speed corresponding to the movement of the hydraulic cylinder push rod to a certain moment or the corresponding speed when the push rod moves to a certain position according to the work requirements, and the motion control unit is based on the control requirements and the received push rod current Logical judgment and position closed-loop calculation are performed on the displacement signal to obtain the operating mode instructions, speed setting instructions and pressure setting instructions of A and B servo drivers (7, 10), and send them to A servo driver (7) and B servo driver respectively (10), thereby adjusting the position and speed of the push rod, realizing the precise speed control and position control of the push rod; The control modes include a speed closed-loop mode and a speed-pressure double closed-loop mode; A and B servo drivers (7, 10) receive speed setting commands or speed and pressure setting commands, and control mode commands from the motion control unit, and receive hydraulic cylinders from A and B pressure sensors (4, 11) respectively (2) The current pressure feedback value of the rodless cavity or the rod cavity; when the control mode command of the motion control unit is the speed closed loop mode, the speed closed loop of the servo driver controls the connected servo motor according to the speed setting command of the motion control unit , drive it to run completely according to the speed setting command of the motion control unit; when the control mode command of the motion control unit is the speed and pressure double closed-loop mode, the pressure closed loop of the servo driver is based on the pressure setting command of the motion control unit and the current pressure feedback value Control the speed of the connected servo motor. If the current pressure feedback value reaches or exceeds the set pressure value, then reduce the forward speed setting of the servo motor coaxial with the hydraulic pump that is pumping fluid in the forward direction or increase the speed in the reverse direction. The reverse speed setting of the servo motor coaxial with the hydraulic pump that is draining; if the current pressure feedback value is less than the set pressure value, the positive speed setting of the servo motor coaxial with the hydraulic pump that is pumping liquid is raised Or reduce the reverse speed setting of the servo motor coaxial with the hydraulic pump that is draining in the reverse direction; compare the current servo motor speed setting value determined by the closed-loop pressure of the servo driver with the speed setting command from the motion control unit, and take The smaller absolute value of the two values is sent to the connected servo motor as the speed command of the servo driver for execution. 8. The control method of the servo pump-controlled hydraulic linear drive system according to claim 7, characterized in that: The push rod movement mode is divided into three types: forward mode, return mode and high-speed reciprocating mode; Ⅰ. Way forward The forward mode refers to the movement of the push rod of the hydraulic cylinder (2) to the direction of the rod cavity, which is divided into two types: fast forward mode and working mode; Ⅰ-1. Fast forward mode At this time, the bottom end of the push rod of the hydraulic cylinder (2) does not bear the resistance of the workpiece, and the motion control unit sends an instruction to the B servo driver (10) connected to the rod cavity side of the hydraulic cylinder (2) to operate in the speed closed-loop mode, and sends Speed setting command, driven by the B servo driver (10), the B servo motor (9) and the B hydraulic pump (8) reverse at the set speed, and the rod cavity leaks; at the same time, the motion control unit is connected to the hydraulic cylinder ( 2) The A servo driver (7) on the side of the rodless cavity issues an instruction to run in the speed closed-loop mode, and sends out a speed setting instruction. Driven by the A servo driver (7), the A servo motor (6) and the A hydraulic pump (5 ) run forward at a set speed, supply pressurized liquid into the rodless cavity, and push the push rod of the hydraulic cylinder (2) forward at a predetermined speed; Ⅰ-2. Working method At this time, the bottom end of the hydraulic cylinder (2) push rod bears the resistance of the workpiece; The motion control unit sends an instruction to the A servo driver (7) on the side of the rodless cavity to run in the speed closed-loop mode, and sends a speed setting instruction, and the A servo motor (6) and the A hydraulic pump are driven by the A servo driver (7) (5) Push the push rod of the hydraulic cylinder (2) forward according to the working speed set by the speed of the motion control unit; at the same time, the motion control unit sends a signal to the B servo driver (10) on the side of the rod cavity to run in the double closed-loop mode of speed and pressure command, and issue reverse speed setting and pressure setting commands, the B servo drive (10) according to the speed setting command of the motion control unit, the pressure setting command and the current pressure feedback value of the B pressure sensor (11) according to the speed The pressure double closed-loop mode determines the speed of the B servo motor (9), and the B hydraulic pump (8) reverses to relieve pressure; Ⅱ. Return method The return stroke means that the push rod of the hydraulic cylinder (2) moves in the direction of the rodless chamber; The motion control unit issues an instruction to the B servo driver (10) on the side of the rod chamber to run in the speed closed-loop mode, and sends a speed setting instruction, and the B servo motor (9) and the B hydraulic pump are driven by the B servo driver (10) (8) Run in the forward direction at a predetermined speed, push the piston push rod to return to the direction of the rodless chamber; at the same time, the motion control unit sends an instruction to the A servo driver (7) on the side of the rodless chamber to run in the double closed-loop mode of speed and pressure, and Send reverse speed setting and pressure setting commands, A servo drive (7) according to the speed setting command, pressure setting command of the motion control unit and the current pressure feedback value of A pressure sensor (4) according to the speed and pressure double closed-loop mode Determine the speed of the A servo motor (6), and the A hydraulic pump (5) reverses to discharge liquid; Ⅲ. High-speed reciprocating mode For the high-speed repetition of the above-mentioned working mode and returning mode, the hydraulic cylinder (2) is in the reciprocating motion state of "working-returning-working..."; the motion control unit according to the displacement signal and/or time of the displacement sensor (14) Judging the end of the work progress or the end of the return journey, that is, transfer to the return mode or the work progress mode. 9. The control method of the servo pump-controlled hydraulic linear drive system according to claim 8, characterized in that: The pipeline connects the liquid storage tank and the rodless chamber of the hydraulic cylinder (2) through the filling valve (1). The filling valve (1) is a one-way valve. When the pressure is lower than the side pressure of the liquid storage tank, the filling valve (1) is automatically opened, otherwise the filling valve (1) remains closed; In Ⅰ-1 fast-forward mode, if the rotational speed of the A hydraulic pump (5) and the A servo motor (6) on the side of the rodless chamber cannot meet the oil supply requirements when the push rod moves forward, the hydraulic pressure on the side of the rodless chamber will decrease. When the pressure in the rodless chamber is lower than the side pressure of the liquid storage tank, the liquid filling valve (1) connected to the rodless chamber is automatically opened to replenish the rodless chamber; When the fast-forward mode ends and the work-forward mode is switched, the motion control unit reduces the speed setting values of the B servo motor (9) and the B hydraulic pump (8) on the side of the rod chamber or sends a speed lock zero signal, so that the B servo motor ( 9) and B hydraulic pump (8) speeds down, the pressure relief of the rod cavity slows down or stops, at this time, the pressure of the rodless cavity rises, and the filling valve (1) automatically closes.