Multi-servo electric cylinder synchronous lifting motion control system and control method

Abstract

The invention discloses a multi-servo-electric-cylinder synchronous lifting motion control system and method, and belongs to the technical field of servo electric cylinder control systems.The multi-servo-electric-cylinder synchronous lifting motion control system comprises a controller, a plurality of servo drivers, a plurality of servo electric cylinders and a plurality of displacement sensors; the controller is used for generating a digital motion control instruction and receiving and processing a digital displacement feedback signal; the control signal input end of the servo driver is connected with the instruction output end of the controller through an Ethernet bus and a CAN bus. A traditional hydraulic scheme is replaced by an all-electric servo control system, the system monitors the position of each electric cylinder in real time through a high-precision displacement sensor, and a controller executes a high-speed closed-loop control algorithm and dynamically adjusts an instruction, so that ultrahigh-precision synchronous lifting motion of a plurality of servo electric cylinders is realized, and the synchronous lifting motion of the servo electric cylinders is realized. And the problems of asynchronization, clamping stagnation, inaccurate positioning and the like are thoroughly eliminated.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of servo cylinder control system, and particularly relates to a multi-servo cylinder synchronous lifting motion control system and a control method. BACKGROUND

[0002] In the prior art, the lifting of the shooting platform component of the magnesium alloy semi-solid forming equipment is usually driven by a hydraulic system, that is, the combination of a hydraulic pump, a synchronization valve and multiple hydraulic cylinders is used to achieve the lifting. This technology has inherent and fundamental defects: due to the length difference of the hydraulic oil circuit, the uneven load of each hydraulic cylinder and the precision limitation of the synchronization valve itself, the system is difficult to realize true synchronous motion, resulting in problems such as jamming and shaking during lifting. In addition, this system is an open-loop control and cannot monitor and correct the position deviation in real time, resulting in poor positioning accuracy, slow response speed, high energy consumption, and as the load increases and the number of hydraulic cylinders increases, the synchronization performance will be further deteriorated, which seriously restricts the production efficiency and reliability of the equipment. SUMMARY

[0003] The technical problem to be solved by the application is to overcome the shortcomings of the prior art and provide a multi-servo cylinder synchronous lifting motion control system and a control method.

[0004] The technical solution adopted to solve the above technical problems is: a multi-servo cylinder synchronous lifting motion control system, comprising a controller, a plurality of servo drives, a plurality of servo cylinders and a plurality of displacement sensors, the controller is used to generate digital motion control instructions and receive and process digital displacement feedback signals; the control signal input end of the servo drive is connected with the instruction output end of the controller through an Ethernet bus and a CAN bus; the power input end of the servo motor of the servo cylinder is connected with the power output end of the servo drive through a three-phase power cable, and the mechanical execution end of the servo cylinder is used to jointly articulate a load platform.

[0005] Through the above technical solution, the system realizes the synchronous lifting motion of multiple servo cylinders with ultra-high precision by real-time monitoring of the position of each cylinder by a high-precision displacement sensor and dynamic adjustment of the instructions by the controller executing a high-speed closed-loop control algorithm, thereby completely eliminating problems such as asynchrony, jamming and inaccurate positioning. At the same time, the system has the advantages of fast response speed, smooth motion, digital precise parameter setting, energy saving and high efficiency, simple structure and easy maintenance, etc., which significantly improves the performance, automation level and reliability of the equipment, and is particularly suitable for high-demand industrial application scenarios such as magnesium alloy semi-solid forming equipment.

[0006] Further, the displacement sensors are rigidly mounted inside and outside the piston rod of the servo cylinders respectively, for measuring the absolute displacement of each servo cylinder in real time at a sampling frequency greater than 100 Hz, and transmitting the displacement measurement signals to the controller through an analog or digital interface.

[0007] Through the above technical solution, the accuracy and timeliness of data collection for servo cylinder movement can be ensured, which is beneficial to the system to obtain accurate and timely data during adjustment, greatly improving the precision of system adjustment.

[0008] Further, the controller is built-in with a multi-axis synchronous control algorithm, which is programmed to perform the following operations: simultaneously sending motion instructions containing target position, target speed and target acceleration to all servo drives at a period greater than 1 kHz; synchronously receiving real-time displacement data uploaded by all displacement sensors; calculating the real-time displacement deviation between any two servo cylinders; when the absolute value of the displacement deviation exceeds the preset synchronization tolerance threshold, immediately recalculating and outputting the corrected motion instructions to the corresponding servo drives.

[0009] Through the above technical solution, the accuracy and synchronization of servo cylinder movement are ensured.

[0010] Further, the controller includes a programmable logic controller integrated with motion control function, an industrial computer and an embedded motion control card, and the displacement sensors include absolute value encoders, grating rulers and magnetic grating rulers, with a measurement accuracy greater than ±0.01 mm.

[0011] Through the above technical solution, an accurate and reliable feedback data source is provided for closed-loop control.

[0012] Further, it also includes a touch screen type human-machine interface connected with the controller through RS-485, Ethernet and PROFINET bus, for operators to input digital target position values, speed values and acceleration values, and to display the displacement, speed and synchronization error of all servo cylinders in the form of waveform chart or digital table in real time, the system is specifically integrated on the rack of a magnesium alloy semi-solid forming device, the load platform is the shooting table component of the device, and the number of servo cylinders is four, arranged respectively below the four corners of the shooting table component.

[0013] Through the above technical solution, the operation convenience and state visualization of the system are greatly improved. Operators can accurately set parameters digitally, avoiding the experience and inaccuracy of adjusting valves in traditional hydraulic systems. At the same time, real-time data is displayed in the form of waveform chart, etc., which is convenient for quickly diagnosing problems, monitoring the production process and performing equipment maintenance.

[0014] A control method for a multi-servo electric cylinder synchronous lifting motion control system includes the following specific steps: Step 1: Power on and initialize the system. Set the absolute target position for this lifting and lowering motion through the human-machine interface. (Unit: mm) Maximum speed (Unit: mm / s) and maximum acceleration (Unit: mm / s) 2 ); Step 2: The controller performs a zeroing operation, controlling all servo electric cylinders to move to the mechanical zero position and resetting the current readings of all displacement sensors to zero; Step 3: The controller simultaneously sends the same motion command to all servo drives. The command content is: accelerate... Accelerate to speed Move at a constant speed until approaching the target position, then accelerate. Decelerate and eventually stop at the target location. ; Step 4: During the motion, the controller synchronously samples the real-time displacement values ​​fed back by all displacement sensors at a period of 1 millisecond. , ,..., ; Step 5: Within each control cycle, the controller calculates the difference between each pair of displacements of all servo electric cylinders. =| - Find the maximum value among them. ; Step Six: With the preset synchronization tolerance threshold (Values ​​ranging from 0.1 mm to 1.0 mm) are compared; Step Seven: If The controller maintains the original motion command unchanged; Step 8: If The controller immediately starts the PID correction algorithm. For servo cylinders with lag in displacement, it calculates the speed feedforward compensation amount and generates a new, higher target speed command to send to its corresponding servo driver. For servo cylinders with lead in displacement, it calculates the speed reduction amount and generates a new, lower target speed command to send to its corresponding servo driver. Step 9: Repeat steps 4 to 8 until the controller determines that the deviation between the current position and the target position of all servo cylinders is less than the positioning accuracy threshold. Then, control all servo motors to stop and complete the lifting motion.

[0015] By the technical scheme, the accuracy of the synchronization effect is ensured, the adaptability of the synchronization method is high, the disturbance can be effectively inhibited, and the lifting process is stable, efficient and accurate.

[0016] Further, the proportional coefficient Kp, the integral coefficient Ki and the differential coefficient Kd of the PID correction algorithm in the eighth step are adaptively adjusted online according to the load mass and the motion speed of the servo cylinder.

[0017] By the technical scheme, the adaptability and robustness of the control system are significantly improved.

[0018] Further, the motion parameter further includes the deceleration, and the absolute value of the deceleration is equal to the absolute value of the acceleration The method is specially used for controlling the lifting motion of the injection platform component of the magnesium alloy semi-solid forming equipment in the injection, barrel replacement and maintenance processes.

[0019] By the technical scheme, the symmetry of the acceleration and the deceleration is defined, the motion trajectory planning is simplified, the positioning accuracy and the stability when the motion stops are improved, the symmetrical acceleration and deceleration make the whole motion process smoother, the impact on the mechanical structure is reduced, and problems such as overshoot or positioning time extension caused by too rapid or too slow deceleration are avoided.

[0020] The beneficial effects of the present application are as follows: the present application adopts a full-electric servo control system to replace the traditional hydraulic scheme, the system monitors the positions of the electric cylinders in real time through a high-precision displacement sensor, and a high-speed closed-loop control algorithm is executed by a controller to dynamically adjust the instructions, so that the synchronous lifting motion of multiple servo cylinders is realized, and the problems such as asynchronization, sticking and inaccurate positioning are completely eliminated. At the same time, the system has the advantages of fast response speed, smooth motion, digital accurate parameter setting, energy saving, high efficiency, simple structure and easy maintenance, and significantly improves the device performance, automation degree and reliability, and is particularly suitable for high-demand industrial application scenarios such as magnesium alloy semi-solid forming equipment. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is the system principle diagram of the present application; Figure 2 is the system architecture diagram of the present application. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0023] As Figure 1 and Figure 2As shown, the multi-servo cylinder synchronous lifting motion control system and control method of the embodiment comprises a controller, a plurality of servo drives, a plurality of servo cylinders and a plurality of displacement sensors. The controller is used to generate digital motion control instructions and receive and process digital displacement feedback signals. The control signal input end of the servo drive is connected with the instruction output end of the controller through an Ethernet bus and a CAN bus. The servo motor power input end of the servo cylinder is connected with the power output end of the servo drive through a three-phase power cable. The mechanical execution end of the servo cylinder is used to jointly articulate a load platform. The system monitors the positions of the cylinders in real time through high-precision displacement sensors and dynamically adjusts the instructions by executing a high-speed closed-loop control algorithm by the controller, thereby realizing the ultra-high-precision synchronous lifting motion of the plurality of servo cylinders and completely eliminating problems such as asynchronization, sticking and inaccurate positioning. At the same time, the system has the advantages of fast response speed, stable motion, digitalized and accurate parameter setting, energy saving and high efficiency, simple structure and easy maintenance, etc. The system significantly improves the performance, automation level and reliability of the equipment and is particularly suitable for high-demand industrial application scenarios such as magnesium alloy semi-solid forming equipment.

[0024] The displacement sensors are rigidly installed inside and outside the piston rods of the servo cylinders and are used to measure the absolute displacement of each servo cylinder in real time at a sampling frequency of more than 100 Hz and transmit the displacement measurement signals to the controller through an analog or digital interface, which can ensure the accuracy and timeliness of the data collection of the servo cylinder movement and is beneficial to obtaining accurate and timely data during the adjustment of the system and greatly improving the accuracy of the system adjustment.

[0025] The controller has a multi-axis synchronous control algorithm built in and is programmed to perform the following operations: simultaneously sending motion instructions containing target positions, target speeds and target accelerations to all servo drives at a period of more than 1 kHz; synchronously receiving real-time displacement data uploaded by all displacement sensors; calculating the real-time displacement deviation between any two servo cylinders; when the absolute value of the displacement deviation exceeds a preset synchronization tolerance threshold, immediately recalculating and outputting the corrected motion instructions to the corresponding servo drives, thereby ensuring the accuracy and synchronization of the servo cylinder movement.

[0026] The controller comprises a programmable logic controller integrated with a motion control function, an industrial computer and an embedded motion control card. The displacement sensors comprise absolute value encoders, grating rulers and magnetic grating rulers, and the measurement accuracy is greater than ±0.01 mm, which provides an accurate and reliable feedback data source for closed-loop control.

[0027] Also included is a touch screen human-machine interface connected with the controller through RS-485, Ethernet and PROFINET bus, which is used for operator to input digital target position value, speed value and acceleration value, and to display displacement, speed and synchronization error of all servo cylinders in the form of waveform chart or digital table in real time. The system is specifically integrated on the rack of a magnesium alloy semi-solid forming device, the load platform is the shooting platform component of the device, and the number of servo cylinders is four, which are arranged below the four corners of the shooting platform component, greatly improving the operation convenience and state visualization of the system. The operator can accurately set the parameters digitally, avoiding the experience and inaccuracy of adjusting the valve in the traditional hydraulic system. At the same time, real-time data is displayed in the form of waveform chart, which is convenient for quickly diagnosing problems, monitoring the production process and maintaining the equipment.

[0028] A control method of a multi-servo cylinder synchronous lifting motion control system, comprising the following specific steps: Step one: system power-on initialization, set the absolute target position of this time lifting motion through the human-machine interface (unit: millimeter), maximum motion speed (unit: millimeter / second) and maximum acceleration (unit: millimeter / second 2 ); Step two: the controller performs zero reset operation, controls all servo cylinders to move to mechanical zero position, and resets the current reading of all displacement sensors to zero; Step three: the controller simultaneously issues the same motion instruction to all servo drives, the instruction content is: accelerate to speed with acceleration , uniform motion to approach the target position, decelerate with acceleration , and finally stop at the target position ; Step four: in the motion process, the controller synchronously samples the real-time displacement values of all displacement sensors feedback with 1 millisecond period , ,..., ; Step five: in each control period, the controller calculates the difference between the displacements of all servo cylinders =| - |, finds the maximum value ; Step six: compare with the preset synchronization tolerance threshold (value range 0.1mm to 1.0mm); Step seven: if The controller maintains the original motion instruction unchanged; Step eight: if The controller immediately starts the PID correction algorithm, calculates the speed feedforward compensation amount for the servo cylinder with displacement lag, generates a new higher target speed instruction and sends it to the corresponding servo driver; for the servo cylinder with displacement advance, calculates the speed reduction amount, generates a new lower target speed instruction and sends it to the corresponding servo driver; Step nine: repeat steps four to eight until the controller determines that the deviation of the current position of all servo cylinders from the target position is less than the positioning accuracy threshold, then stop all servo motors to complete the lifting motion, ensuring the accuracy of the synchronization effect, making the synchronization method self-adaptive, effectively suppressing disturbances and ensuring smooth, efficient and accurate lifting process.

[0029] The proportional coefficient Kp, integral coefficient Ki and differential coefficient Kd of the PID correction algorithm in step eight are adjusted online according to the load mass and motion speed of the servo cylinder, significantly improving the adaptive ability and robustness of the control system.

[0030] The motion parameters also include deceleration, and the absolute value of the deceleration is equal to the absolute value of the acceleration The method is specifically used for controlling the lifting motion of the injection platform component of the magnesium alloy semi-solid forming equipment during injection, barrel replacement and maintenance, clearly defining the symmetry of acceleration and deceleration, simplifying the motion trajectory planning, improving the positioning accuracy and stability when the motion stops, and making the entire motion process smoother, reducing the impact on the mechanical structure, and avoiding problems such as overshoot or prolonged positioning time caused by too rapid or too slow deceleration.

[0031] The above is only a preferred embodiment of the present application, and is not intended to limit the protection scope of the present application.

Claims

1. A multi-servo electric cylinder synchronous lifting motion control system, characterized in that, The system includes a controller, several servo drives, several servo cylinders, and several displacement sensors. The controller generates digital motion control commands and receives and processes digital displacement feedback signals. The control signal input terminals of the servo drives are connected to the command output terminals of the controller via Ethernet and CAN buses. The servo motor power input terminals of the servo cylinders are connected to the power output terminals of the servo drives via three-phase power cables. The mechanical actuators of the servo cylinders are used to jointly hinge and connect to the load platform.

2. The multi-servo electric cylinder synchronous lifting motion control system according to claim 1, characterized in that, The displacement sensors are rigidly mounted inside and outside the piston rod of the servo cylinder, respectively, and are used to measure the absolute displacement of each servo cylinder in real time at a sampling frequency greater than 100Hz, and transmit the displacement measurement signal to the controller through an analog interface or a digital interface.

3. The multi-servo electric cylinder synchronous lifting motion control system according to claim 2, characterized in that, The controller has a built-in multi-axis synchronous control algorithm and is programmed to perform the following operations: simultaneously send motion commands containing target position, target velocity, and target acceleration to all servo drives at a period greater than 1 kHz; synchronously receive real-time displacement data uploaded by all displacement sensors; calculate the real-time displacement deviation between any two servo cylinders; and when the absolute value of the displacement deviation exceeds a preset synchronization tolerance threshold, immediately recalculate and output the corrected motion command to the corresponding servo drive.

4. The multi-servo electric cylinder synchronous lifting motion control system according to claim 3, characterized in that, The controller includes a programmable logic controller with integrated motion control functions, an industrial computer, and an embedded motion control card. The displacement sensor includes an absolute encoder, an optical encoder, and a magnetic encoder, with a measurement accuracy greater than ±0.01 mm.

5. The multi-servo electric cylinder synchronous lifting motion control system according to claim 4, characterized in that, It also includes a touch screen human-machine interface, which is connected to the controller via RS-485, Ethernet and PROFINET bus. The interface is used for the operator to input digital target position values, velocity values ​​and acceleration values, and displays the displacement, velocity and synchronization error of all servo electric cylinders in real time in the form of waveform graphs or digital tables. The system is specifically integrated on the frame of the magnesium alloy semi-solid forming equipment. The load platform is the injection stage component of the equipment. There are four servo electric cylinders, which are respectively arranged under the four corners of the injection stage component.

6. The control method for a multi-servo electric cylinder synchronous lifting motion control system according to claim 5, characterized in that, The specific steps include the following: Step 1: Power on and initialize the system. Set the absolute target position for this lifting and lowering movement through the human-machine interface. (Unit: mm) Maximum speed (Unit: mm / s) and maximum acceleration (Unit: mm / s) 2 ); Step 2: The controller performs a zeroing operation, controlling all servo electric cylinders to move to the mechanical zero position and resetting the current readings of all displacement sensors to zero; Step 3: The controller simultaneously sends the same motion command to all servo drives. The command content is: accelerate... Accelerate to speed Move at a constant speed until approaching the target position, then accelerate. Decelerate and eventually stop at the target location. ; Step 4: During the motion, the controller synchronously samples the real-time displacement values ​​fed back by all displacement sensors at a period of 1 millisecond. , ,..., ; Step 5: Within each control cycle, the controller calculates the difference between each pair of displacements of all servo electric cylinders. =| - Find the maximum value among them. ; Step Six: With the preset synchronization tolerance threshold (Values ​​ranging from 0.1 mm to 1.0 mm) are compared; Step Seven: If The controller maintains the original motion command unchanged; Step 8: If The controller immediately starts the PID correction algorithm. For servo cylinders with lag in displacement, it calculates the speed feedforward compensation amount and generates a new, higher target speed command to send to its corresponding servo driver. For servo cylinders with lead in displacement, it calculates the speed reduction amount and generates a new, lower target speed command to send to its corresponding servo driver. Step 9: Repeat steps 4 to 8 until the controller determines that the deviation between the current position and the target position of all servo cylinders is less than the positioning accuracy threshold. Then, control all servo motors to stop and complete the lifting motion.

7. The control method for a multi-servo electric cylinder synchronous lifting motion control system according to claim 6, characterized in that, In step eight, the proportional coefficient Kp, integral coefficient Ki, and derivative coefficient Kd of the PID correction algorithm are adaptively adjusted online based on the load mass and movement speed of the servo electric cylinder.

8. The control method for a multi-servo electric cylinder synchronous lifting motion control system according to claim 7, characterized in that, The motion parameters also include deceleration, and the absolute value of the deceleration is related to the acceleration. The absolute values ​​are equal, and the method is specifically used to control the lifting and lowering movement of the injection stage components of magnesium alloy semi-solid forming equipment during injection, barrel replacement and maintenance processes.

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