Electric cylinder control method based on PID-NFTSM algorithm

Abstract

The invention discloses an electric cylinder control method based on a PID-NFTSM algorithm. The electric cylinder control method comprises the following steps that 1, state parameters of an electric cylinder are collected; 2, a position ring, a speed ring and a current ring of the electric cylinder are sequentially adjusted according to the state parameters of the electric cylinder; the position loop is adjusted through a PID control algorithm, the speed loop is adjusted through an NFTSM algorithm, and the current loop is adjusted through a DPCC algorithm. The method has the characteristics that the control accuracy of the electric cylinder is improved, the response speed is increased, and buffeting caused by external interference is weakened.

Description

Technical Field

[0001] This invention relates to the field of electric cylinder technology, and more specifically, to an electric cylinder control method based on the PID-NFTSM algorithm. Background Technology

[0002] Electric cylinders, as a high-precision and high-efficiency linear motion transmission device, are widely used in many fields such as industrial automation, military equipment, medical equipment, automotive testing, logistics and transportation, and environmental protection. With their advantages of high-precision control, energy saving and environmental protection, and low maintenance costs, they are gradually replacing traditional hydraulic and starting systems.

[0003] As a key component of electric cylinders, permanent magnet synchronous motors exhibit strong coupling and nonlinearity, requiring closed-loop control to ensure accuracy. Existing closed-loop control methods include adaptive control, fuzzy control, and sliding mode control. Adaptive control requires dynamic parameter adjustment, resulting in poor stability. This issue necessitates optimization using a multi-level dynamic force control system. Fuzzy control performs well in controlling ordinary electric cylinders, but its insufficient dynamic processing capability makes it prone to control deviations when high-precision control is required. Sliding mode control is highly susceptible to high-frequency chattering on the sliding surface and is easily affected by external interference due to its sensitivity to system parameter changes, exhibiting weak robustness.

[0004] Therefore, in order to improve the control accuracy of electric cylinders, the control method of electric motors is improved based on the existing control methods. Summary of the Invention

[0005] The purpose of this invention is to design and develop an electric cylinder control method based on the PID-NFTSM algorithm. By sequentially controlling the permanent magnet synchronous motor in three loops, the control accuracy and response speed can be effectively improved, and chattering can be reduced.

[0006] The technical solution provided by this invention is as follows: An electric cylinder control method based on the PID-NFTSM algorithm includes the following steps: Step 1: Collect the state parameters and motion parameters of the electric cylinder; Step 2: Adjust the position loop, speed loop, and current loop of the electric cylinder in sequence according to the state parameters of the electric cylinder; The velocity loop is adjusted using the NFTSM algorithm. The output of the velocity loop is: ; In the formula, For torque shaft current, The number of magnetic pole pairs, It is a permanent magnet flux chain. This is the equivalent rotational inertia of the motor. Let be the derivative of the target mechanical angular velocity of the permanent magnet synchronous motor. For the velocity slip surface switching function, The first sliding mode coefficient, This is the second sliding mode coefficient. , All are constants greater than 0. It is a constant, and , This is the difference between the desired angular velocity and the actual angular velocity of the motor. , It is an odd number and , This is the motor load torque. This refers to the disturbance torque, which includes damping, friction, and disturbance.

[0007] Preferably, the state parameters include the lead of the ball screw pair, the transmission ratio of the reduction gear pair, the idle stroke of the motor pressure build-up cylinder, the flux linkage of the permanent magnet, the number of pole pairs of the motor, and the equivalent moment of inertia of the motor.

[0008] Preferably, the motion parameters of the electric cylinder include the actual rotation angle and the actual rotation speed of the permanent magnet synchronous motor.

[0009] Preferably, the position loop is adjusted using a PID control algorithm.

[0010] Preferably, the output of the position loop is: ; In the formula, The target mechanical angular velocity of the permanent magnet synchronous motor. The scaling factor for the position loop. For the integral coefficients of the position loop, This is the actual rotation angle of the permanent magnet synchronous motor. To eliminate the rotation angle of the permanent magnet synchronous motor corresponding to the idle stroke of the motor's pressure-building cylinder.

[0011] Preferably, the rotation angle of the permanent magnet synchronous motor corresponding to the elimination of the idle stroke of the motor pressure-building cylinder satisfies: ; In the formula, For the lead of the ball screw assembly, This represents the transmission ratio of the reduction gear pair. The idle stroke of the motor's pressure cylinder.

[0012] Preferably, the velocity loop further includes an extended state observer: ; In the formula, For the observation error of the extended state observer, This refers to the actual speed of the motor. As the first intermediate parameter, As the second intermediate parameter, for The derivative of for The derivative of , The gain coefficient of the extended state observer. It is a nonlinear function.

[0013] Preferably, the nonlinear function satisfies: ; In the formula, , A constant greater than 0 It is a symbolic function.

[0014] Preferably, the current loop is adjusted using the DPCC algorithm.

[0015] Preferably, the output of the current loop is: ; In the formula, for Excitation shaft voltage at time _____ Stator voltage, for The excitation shaft current at any given time, for electric angular velocity at time t, For torque shaft inductance, for Torque shaft current at time t, For the excitation shaft inductance, For the target excitation shaft current, The sampling period is for Torque shaft voltage at time t, The target torque shaft current.

[0016] The beneficial effects of this invention are as follows: The electric cylinder control method based on the PID-NFTSM algorithm designed and developed in this invention can effectively and precisely control the electric cylinder by controlling the three loops of the permanent magnet synchronous motor in sequence, thereby improving control accuracy and response speed, enhancing the robustness of the electric cylinder to external disturbances, reducing chattering caused by external disturbances, and improving the stability of the electric cylinder. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the electric cylinder control method based on the PID-NFTSM algorithm described in this invention.

[0018] Figure 2 This is a schematic diagram of the actual assembly of the data acquisition system for the electric cylinder described in this invention.

[0019] Figure 3 This is a schematic diagram comparing the electric cylinder stroke simulation experiment based on the PID-NFTSM algorithm and the sliding mode control algorithm described in this invention. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0021] like Figure 1 As shown, the present invention provides an electric cylinder control method based on the PID-NFTSM algorithm, which specifically includes the following steps: Step 1: Collect the state parameters and motion parameters of the electric cylinder; The state parameters include the lead of the ball screw pair, the transmission ratio of the reduction gear pair, the idle stroke of the motor pressure cylinder, the flux linkage of the permanent magnet, the number of pole pairs of the motor, and the equivalent moment of inertia of the motor. The motion parameters of the electric cylinder include the actual rotation angle and the actual speed of the permanent magnet synchronous motor, such as... Figure 2 As shown, in this embodiment, the motion parameters of the electric cylinder are obtained by electromagnetic induction detection of a photoelectric encoder mounted on the shaft of the electric cylinder.

[0022] Step 2: Adjust the position loop, speed loop, and current loop of the electric cylinder in sequence according to the state parameters of the electric cylinder; The control strategy of the position loop satisfies: For a given motor-driven pressure-building cylinder, its idle stroke is fixed, and the corresponding rotation angle to eliminate the idle stroke is:

[0023] In the formula, To eliminate the rotation angle of the permanent magnet synchronous motor corresponding to the idle stroke of the motor's pressure-building cylinder, For the lead of the ball screw assembly, This represents the transmission ratio of the reduction gear pair. The idle stroke of the motor's pressure cylinder; The position loop is regulated using a PID control algorithm; therefore, the output of the position loop controller is:

[0024] In the formula, The target mechanical angular velocity of the permanent magnet synchronous motor. The scaling factor for the position loop. For the integral coefficients of the position loop, This is the actual rotation angle of the permanent magnet synchronous motor; The control strategy of the speed loop satisfies: Using the angular velocity deviation of the permanent magnet synchronous motor as the input to the speed loop, the control variables and their derivatives for the speed loop slip diaphragm variable structure control are:

[0025] In the formula, This is the difference between the desired angular velocity and the actual angular velocity of the motor. The actual mechanical angular velocity of a permanent magnet synchronous motor, This is the derivative of the difference between the desired angular velocity and the actual angular velocity of the motor. Let be the derivative of the target mechanical angular velocity of the permanent magnet synchronous motor. This is the derivative of the actual mechanical angular velocity of the permanent magnet synchronous motor; The electromagnetic torque equation of the motor is:

[0026] In the formula, For electromagnetic torque, The number of magnetic pole pairs, It is a permanent magnet flux chain. For torque shaft current; The mechanical motion equation of the electric motor is:

[0027] In the formula: This is the equivalent rotational inertia of the motor. This is the motor load torque. This includes the disturbance torque, which incorporates damping, friction, and disturbances. Combining equations (2) and (4), we can obtain:

[0028] Based on the requirements of sliding mode control, the sliding surface switching function of Non-Singular Fast Terminal Sliding Mode Control (NFTSM) is designed as follows:

[0029] In the formula, For the velocity slip surface switching function, The first sliding mode coefficient, It is the second sliding mode coefficient, and , All are constants greater than 0. , It is an odd number and ; The symbolic function satisfies:

[0030] Differentiating equation (6) yields:

[0031] Introducing the exponential reaching law:

[0032] In the formula, , All are constants greater than 0; After the system enters steady state, the switching items This is the main source of chattering; therefore, the improved exponential approach law is:

[0033] In the formula, It is a constant, and ; Compared to the switching function sgn(s) and the saturation function sat(s), the hyperbolic tangent function tanh(s) switches more smoothly near the sliding surface during the control process. , It continuously decreases until it stabilizes at the origin, making the switching term... By continuously reducing the value to near zero, chattering in sliding mode control is suppressed, thereby improving the performance of the sliding mode controller.

[0034] Combining equations (5), (8), and (10), the output of the speed loop sliding mode controller can be obtained as follows:

[0035] As can be seen from equation (11), the changes in motor load torque and system parameters have a significant impact on the speed loop control performance. An extended state observer is used to observe the load torque and system parameters and compensate them to the sliding mode controller to improve the anti-interference capability of the control system.

[0036] set up , ,but:

[0037] In the formula, This is the sum of the disturbances caused by changes in motor load torque and system parameters; Establish the following extended state observer:

[0038] Among them, nonlinear The function is as follows:

[0039] In the formula, For the observation error of the extended state observer, This refers to the actual speed of the motor. , The gain coefficient of the extended state observer. , A constant greater than 0; use The function can avoid high-frequency chatter, where , The design is based on the concept of observer bandwidth, i.e. , ,in The bandwidth of the observer is used; a larger bandwidth can suppress disturbances. An extended state observer, through careful design, can... , And compensate for it to the speed ring slip mode controller.

[0040] The control strategy of the current loop satisfies: The voltage equation for a permanent magnet synchronous motor is:

[0041] In the formula, For torque shaft voltage, This is the excitation shaft voltage. Stator voltage, For excitation shaft current, For electric angular velocity, Torque shaft inductance, For the excitation shaft inductance; Formula (1) is discretized using the first-order Taylor formula:

[0042] In the formula, The sampling period is for Excitation shaft voltage at time _____ for Torque shaft voltage at time t, for The excitation shaft current at any given time, for Torque shaft current at time t, for electric angular velocity at time t, for The excitation shaft current at any given time, for Torque shaft current at any given moment; For the predicted current value at the next moment to track the reference current, the following must be satisfied:

[0043] In the formula, The target excitation shaft current, and , The target torque shaft current; The output of the current loop controller is:

[0044] The PID-NFTSM algorithm and traditional sliding mode control algorithm described in this invention were simulated using MATLAB software. Under no-load start-up conditions, the target stroke of the electric cylinder push rod was 70 mm. After the system reached steady state, a constant thrust of 10 kN was applied to the end of the push rod at 0.4 s. Figure 3 As shown, when using the traditional sliding mode control algorithm, the electric cylinder deviates to a certain extent due to the thrust. However, when using the electric cylinder push rod stroke based on the PID-NFTSM algorithm described in this invention, the stroke is basically stable. Compared with the traditional sliding mode control algorithm, it is more stable and has a smaller deviation, proving that the control based on the PID-NFTSM algorithm described in this invention is more accurate, has a faster response, and makes the electric cylinder more stable.

[0045] This invention presents a control method for an electric cylinder based on the PID-NFTSM algorithm. By sequentially controlling the three loops of the permanent magnet synchronous motor, this method can effectively and precisely control the electric cylinder, improving control accuracy and response speed, enhancing the robustness of the electric cylinder to external disturbances, reducing chattering caused by external disturbances, and improving the stability of the electric cylinder.

[0046] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for controlling an electric cylinder based on a PID-NFTSM algorithm, characterized in that, Includes the following steps: Step 1: Collect the state parameters and motion parameters of the electric cylinder; Step 2: Adjust the position loop, speed loop, and current loop of the electric cylinder in sequence according to the state parameters of the electric cylinder; The velocity loop is adjusted using the NFTSM algorithm. The output of the velocity loop is: ； wherein, is the torque axis current, is the number of pole pairs, is the permanent magnet flux linkage, is the equivalent moment of inertia of the motor, is the derivative of the target mechanical angular velocity of the permanent magnet synchronous motor, is the switching function of the speed loop sliding mode surface, is the first sliding mode coefficient, is the second sliding mode coefficient, , are constants greater than 0, is a constant, and , is the difference between the desired angular velocity and the actual angular velocity of the motor, , is an odd number and , is the load torque of the motor, is the disturbance torque including damping, friction, and disturbances, etc.

2. The electric cylinder control method based on the PID-NFTSM algorithm as described in claim 1, characterized in that, The state parameters include the lead of the ball screw pair, the transmission ratio of the reduction gear pair, the idle stroke of the motor pressure build-up cylinder, the flux linkage of the permanent magnet, the number of pole pairs of the motor, and the equivalent moment of inertia of the motor.

3. The electric cylinder control method based on the PID-NFTSM algorithm as described in claim 2, characterized in that, The motion parameters of the electric cylinder include the actual rotation angle and the actual speed of the permanent magnet synchronous motor.

4. The electric cylinder control method based on the PID-NFTSM algorithm as described in claim 3, characterized in that, The position loop is adjusted using a PID control algorithm.

5. The electric cylinder control method based on the PID-NFTSM algorithm as described in claim 4, characterized in that, The output of the position loop is: ； In the formula, The target mechanical angular velocity of the permanent magnet synchronous motor. This is the scaling factor for the position loop. For the integral coefficients of the position loop, This is the actual rotation angle of the permanent magnet synchronous motor. To eliminate the rotation angle of the permanent magnet synchronous motor corresponding to the idle stroke of the motor's pressure-building cylinder.

6. The electric cylinder control method based on the PID-NFTSM algorithm as described in claim 5, characterized in that, The permanent magnet synchronous motor rotation angle corresponding to the elimination of the idle stroke of the motor pressure build-up cylinder satisfies: ； In the formula, For the lead of the ball screw assembly, This represents the transmission ratio of the reduction gear pair. The idle stroke of the motor's pressure cylinder.

7. The electric cylinder control method based on the PID-NFTSM algorithm as described in claim 6, characterized in that, The velocity loop also includes an extended state observer: ； In the formula, For the observation error of the extended state observer, This is the actual speed of the motor. As the first intermediate parameter, As the second intermediate parameter, for The derivative, for The derivative, , The gain coefficient of the extended state observer. It is a nonlinear function.

8. The electric cylinder control method based on the PID-NFTSM algorithm as described in claim 7, characterized in that, The nonlinear function satisfies: ； In the formula, , A constant greater than 0 It is a symbolic function.

9. The electric cylinder control method based on the PID-NFTSM algorithm as described in claim 8, characterized in that, The current loop is adjusted using the DPCC algorithm.

10. The electric cylinder control method based on the PID-NFTSM algorithm as described in claim 9, characterized in that, The output of the current loop is: ； In the formula, for Excitation shaft voltage at time _____ Stator voltage, for The excitation shaft current at any given time, for electric angular velocity at time t, For torque shaft inductance, for Torque shaft current at time t, For the excitation shaft inductance, For the target excitation shaft current, The sampling period is for Torque shaft voltage at time t, The target torque shaft current.

Images