A High-Speed Turntable Variable Load Adaptive Control Method

Abstract

The present invention discloses a variable-load adaptive control method for a high-speed turntable. The method is based on a closed-loop control mode and combines a fuzzy PID control algorithm to achieve the adaptive regulation of the rotational speed and position of a servo motor by a microprocessor, reducing the adjustment response time and error of the high-speed turntable and improving the operation stability of the turntable system. A displacement sensor is used to feedback the rotated angle of the high-speed turntable to the microprocessor to form a closed-loop control system, and an error compensation model of the displacement sensor based on improved barycentric Lagrange interpolation-Fourier harmonic synthesis is established, so that the high-speed turntable can still obtain high-precision displacement measurement results in a variable-load processing working environment. A software operating system is designed to control the multi-task operation such as starting, initializing, and command importing of the turntable, improving the real-time performance and detectability of the high-speed turntable system. The present invention can be used for the adaptive control in the case of a variable-load high-speed turntable, and has the characteristics of high precision, fast response, and good robustness.

Description

Technical Field

[0001] The present invention belongs to the field of mechatronic system control design, and particularly relates to a variable load adaptive control method for a high-speed turntable. Background Art

[0002] High-end equipment such as precision instruments and machine tools plays an important role in modern manufacturing. As an important part of precision measuring instruments and precision machining equipment, high-speed turntables have a wide range of applications in aspects such as aircraft design and research and development, aerospace, inertial navigation testing, and the manufacturing of advanced weapon systems. The operating performance of high-speed turntables under variable load conditions will directly affect the use effect and machining quality of high-precision systems. Therefore, it is of great significance to intensify the research on the control method of variable load high-speed turntables.

[0003] A high-performance turntable control system depends on reliable motor hardware, precision measuring devices, reasonable hardware design, and control strategies. After the hardware is determined, adopting a better control algorithm and control mechanism is an effective method to improve the system accuracy. Currently, industrial turntable control systems mainly adopt algorithms such as PID control, compound control, and Smith prediction. These traditional algorithms are based on mature theories. By establishing an accurate mathematical model and compensating for interference signals, control links are designed to improve control accuracy and performance. However, in practice, the turntable works in a complex working condition environment and is affected by non-linear factors such as motor friction, electromagnetic transition, and torque coupling. Moreover, the change of the turntable load will cause a change in the moment of inertia, making it difficult to establish an accurate model and affecting the control effect. To adapt to internal and external disturbances and parameter changes of the system, advanced technologies such as neural networks and fuzzy control are gradually applied to high-speed turntable control systems. A servo motor is used to replace the stepping motor as the driving device to solve the problems of motor speed and subdivision. Detection elements are introduced to form a closed-loop detection system to provide position information and ensure the rotation accuracy. With the rapid development of fields such as precision manufacturing and pose detection, the requirements for control feedback such as the position and angle of the turntable are gradually increasing. As an important measure to improve the sensing accuracy, common methods for error compensation include establishing an error compensation model using genetic algorithms, error fitting, deep training, etc. However, the misalignment error introduced during continuous dynamic detection of sensors is ignored, affecting the error compensation effect of the sampling period and resulting in the lag of the turntable feedback control. Therefore, developing a variable load adaptive control method for high-speed turntables with high accuracy, fast response, strong robustness, and wide adaptability has great practical value. Summary of the Invention

[0004] The present invention proposes a variable load adaptive control method for a high-speed turntable, which realizes high-precision, fast-response, strong-robustness, and real-time adaptive control of the high-speed turntable under disturbance environments and variable load conditions based on a closed-loop control method combined with a fuzzy PID control algorithm and a displacement sensor error compensation model.

[0005] To achieve the above object, the present invention adopts the following technical solutions to solve the problem:

[0006] A high-speed turntable variable-load adaptive control method, comprising the following steps:

[0007] Step 1: Obtain the initial states of the high-speed turntable and the controller, and send closed-loop commands for the required position and speed;

[0008] Step 2: Establish the motor transfer function of the turntable drive servo system;

[0009] Step 3: The displacement sensor detects the angular displacement of the high-speed turntable, and obtains the interpolation function values of each point of the data according to the interpolation principle;

[0010] Step 4: Reconstruct the interpolation curve in Step 3 to obtain the amplitude and phase information of each harmonic, and construct a sensor error compensation model;

[0011] Step 5: Set the closed-loop control process of the turntable to make the transfer function still stable after parameter transformation;

[0012] Step 6: Compare the actual speed and the desired speed of the high-speed turntable motor obtained in Step 4, and input the error e and the error change rate to the fuzzy PID controller;

[0013] Step 7: Detect the turntable error and output the self-adjusting parameters of the fuzzy control for correcting the control parameters;

[0014] Step 8: Adjust the driving state of the servo motor according to the PID control parameters given in Step 7, and further realize the continuous adaptive control of the speed of the high-speed turntable.

[0015] Furthermore, in Step 1, the host computer obtains the relevant basic information of the high-speed turntable and the servo motor, including speed limit, torque limit and safety operation parameters, executes the initialization process such as checking the hardware connection, calibrating the sensor, and setting the initial parameters, and sends the closed-loop control commands for the required position and speed to the actuating element according to the requirements of the workpiece processed by the machine tool, and drives the motor to start the high-speed turntable via the servo amplifier.

[0016] Furthermore, in Step 2, the motor transfer function of the turntable drive servo system is established, and the specific implementation is as follows:

[0017] Assume that the masses and shapes of the components in the turntable system are uniform, and the friction in the system is a function of the actual position and speed, and the torque balance equation of the servo system can be obtained as:

[0018] (1)

[0019] where, is the moment of inertia, is the actual angular displacement of the system, is the rotational speed of the system, is the output torque, is the system load, set is the theoretical angular displacement of the system, then the motor transfer function can be regarded as and the ratio of, if is the Laplace variable, is the motor reduction ratio, and the changed motor transfer function is:

[0020] (2)

[0021] Take the changed motor transfer function as the basis for subsequent feedback control.

[0022] Furthermore, the displacement sensor in step 3 detects the angular displacement of the high-speed turntable, and obtains the interpolation function values of each node of the data according to the interpolation principle. The specific implementation is as follows:

[0023] Use the improved barycentric Lagrange interpolation method to calculate the values near the discrete displacement angle points of the high-speed turntable recorded by the displacement sensor; take K + 1 nodes on the data interval [a, b] , then the displacement angle values of the corresponding nodes are:

[0024] (3)

[0025] Define the Lagrange basic polynomial and the barycentric weight according to formula (4), and calculate and obtain the values near the displacement points of the finite nodes (K + 1 nodes) based on the improved Lagrange interpolation method, that is, the interpolation polynomial near the endpoints of the data interval should handle the problem of displacement curve oscillation caused by load changes, and the displacement angle value is:

[0026] (4)

[0027] Thus, the position information of the displacement sensor and the corresponding sensor angle information are obtained.

[0028] Furthermore, in step 4, reconstruct the interpolation curve in step 3 to obtain the amplitude and phase information of each harmonic, and construct a sensor error compensation model. The specific implementation is as follows:

[0029] Based on the Fourier expansion and convergence theorem, reconstruct the interpolation curve as a finite sine wave according to the relationship between phase, amplitude and frequency, and decompose the sensor displacement error value as:

[0030] (5)

[0031] (6)

[0032] Among them, k is the harmonic order, is the constant term coefficient, is the cosine-sine wave coefficient, is the sine wave frequency information of the error value, is the harmonic amplitude. The phase can be obtained by calculating the arctangent of the ratio of the harmonic coefficients of the displacement error. According to the sampling theorem, k + 1 nodes are extracted within the curve period. Assuming the maximum number of fitting period terms is n(k + 1), the coefficient values of the inverse Fourier series fitting error function are:

[0033] (7)

[0034] Thus, the sine and cosine harmonic coefficients of each order of the interpolation curve are obtained. After comparison and screening the harmonics with numerical values greater than the set threshold and having an impact on the error result exceeding the set error threshold, namely the 0th, 2nd, and 4th harmonics, are used to realize the compensation and reconstruction of the error data of the displacement sensor.

[0035] Furthermore, in step 5, the closed-loop control process of the turntable is set to make the transfer function still stable after parameter transformation. The specific implementation is as follows: Assume that R is the input signal, C is the output signal, and N is the interference signal related to system friction and variable load. is the pre-control link, is the controlled object, and H is the transfer function of the closed-loop control system. According to the system signal superposition principle, the total output signal is:

[0036] (8)

[0037] Calculating the interpolation of the theoretical angular displacement and the actual angular displacement of the system can obtain the system error as , the error change rate , and respectively represent and the first-order derivatives.

[0038] Furthermore, in step 6, the actual rotational speed of the high-speed turntable motor obtained in step 4 is compared with the desired rotational speed, and the system error e and the error change rate are input into the fuzzy controller. The specific implementation is as follows:

[0039] The fuzzy controller uses the output to correct the parameters of the PID controller online to achieve the expected control effect. If the system error e and the error change rate As the input variable of the fuzzy PID controller, the proportional coefficient is set according to the quantization factor and the domain of the proportional factor. The fuzzy domain is {-3, -2, -1, 0, 1, 2, 3}, and the integral coefficient is set. and the differential coefficient The fuzzy domain is {-0.3, -0.2, -0.1, 0, 0.1, 0.2, 0.3}, and the fuzzy sets describing the input and output are {NB, NM, NS, Z, PS, PM, PB}. According to engineering common practice, the membership functions of the fuzzy controller are combined with trigonometric functions and Gaussian membership functions.

[0040] Furthermore, in step 7, the fuzzy control rules of the parameters are respectively combined with the minimum operation algorithm for reasoning to obtain the fuzzy result. where represents the error e and the error change rate the intermediate value after fuzzy reasoning, and then defuzzification is performed based on the centroid method to obtain Taking the proportional coefficient as an example, we can get:

[0041] (9)

[0042] where the solution of is the same as that of ;

[0043] Based on the fuzzy controller, the adjusted parameters are obtained, and the original control parameters of the PID controller are corrected to obtain , , and represent the PID parameters obtained from the previous correction. Continuously adjust the response rate, oscillation amplitude, and settling time of the variable load turntable system.

[0044] Furthermore, in step 8, the corrected PID parameter signal is transmitted to the servo motor driver to adjust the output current of the servo motor to compare the torque, speed, and position of the turntable system, so as to realize the continuous adaptive control of the high-speed turntable speed.

[0045] The beneficial effects of the present invention compared with the prior art are as follows:

[0046] First, the present invention proposes to perform error compensation on the output angular displacement of the displacement sensor to avoid control lag caused by misalignment error during continuous dynamic detection. As Figure 4 shown, this method can better control the angular displacement error when the turntable rotates at high speed;

[0047] Second, the present invention is based on fuzzy PID servo control, effectively avoiding the problem that it is impossible to establish an accurate mathematical model of the servo control system in a disturbance environment and a variable load complex working condition environment, asFigure 6 , 7 As shown in Figure 8, this method has better fast response, anti-interference and robust performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is a flowchart of a high-speed turntable variable-load adaptive control method.

[0049] Figure 2 is a structural function block diagram of a high-speed turntable control system.

[0050] Figure 3 is a mathematical model diagram of a high-speed turntable adaptive control method.

[0051] Figure 4 is a comparison diagram of angular displacement measurement errors between the present invention and existing methods under high-speed rotation.

[0052] Figure 5 is a distribution curve diagram of a membership function combining the error e trigonometric function and the Gaussian membership function.

[0053] Figure 6 is a comparison diagram of fast response angular velocities between the present invention and existing methods.

[0054] Figure 7 is a comparison diagram of anti-interference angular velocities between the present invention and existing methods.

[0055] Figure 8 is a comparison diagram of the robust angular velocity of following a gradually changing sine signal between the present invention and existing methods. DETAILED DESCRIPTION OF THE INVENTION

[0056] The present invention will be specifically described below with reference to the drawings and embodiments.

[0057] An embodiment of the present invention relates to a high-speed turntable variable-load adaptive control method, which realizes high-precision, fast-response and strong-robustness adaptive control of a high-speed turntable in a disturbance environment and a variable-load working condition environment.

[0058] As Figure 1 shown, a high-speed turntable variable-load adaptive control method should include the following steps:

[0059] Step 1: Obtain the initial states of the high-speed turntable and the controller, and send closed-loop commands for the required position and speed. The specific operation is that the upper computer obtains the relevant basic information of the high-speed turntable and the servo motor, including speed limit, torque limit and safety operation parameters, performs initialization processes such as checking hardware connections, calibrating sensors, and setting initial parameters, and sends closed-loop control commands for the required position and speed to the actuator according to the requirements of the workpiece processed by the machine tool, and drives the motor to start the high-speed turntable through the servo amplifier.

[0060] Step 2: Establish the motor transfer function of the turntable drive servo system. The specific implementation is as follows. Assume that the masses and shapes of all components in the turntable system are uniform, and the friction within the system is a function of the actual position and speed. The torque balance equation of the servo system can be obtained as:

[0061] (1)

[0062] Among them, is the moment of inertia, is the actual angular displacement of the system, is the rotational speed of the system, is the output torque, is the system load. Set as the theoretical angular displacement of the system. Then the motor transfer function G(s) can be regarded as the ratio of . If s is the Laplace variable, is the motor reduction ratio. The motor function after changing the formula is:

[0063] (2)

[0064] Obtain the changed motor transfer function as the basis for subsequent feedback control.

[0065] Step 3: The displacement sensor detects the angular displacement of the high-speed turntable, and obtains the interpolation function values of each data node according to the interpolation principle. Specifically, the improved barycentric Lagrange interpolation method is used to calculate the values near the discrete displacement angle error points of the high-speed turntable recorded by the displacement sensor; take K + 1 nodes on the data interval [a, b] , then the corresponding displacement angle values are:

[0066] (3)

[0067] Define the Lagrange basic polynomial and the barycentric weight according to formula (4). Calculate and obtain the values near the finite nodes (K + 1 nodes) based on the improved Lagrange interpolation method. That is, near the endpoints of the data interval, the interpolation polynomial should address the problem of the oscillation of the displacement error curve caused by the load change. The displacement angle value is:

[0068] (4)

[0069] Thus, the position information of the displacement sensor and the corresponding sensor angle information are obtained.

[0070] Step 4: Reconstruct the interpolation curve in Step 3 to obtain the amplitude and phase information of each harmonic, and construct a sensor error compensation model. Specifically, based on the Fourier expansion and convergence theorem, the error curve is reconstructed as a finite sine wave according to the relationship between phase, amplitude, and frequency, and the sensor displacement error value is decomposed into:

[0071] (5)

[0072] (6)

[0073] where k is the harmonic order, is the constant term coefficient, is the cosine and sine wave coefficient, is the frequency information of the error value sine wave, is the harmonic amplitude. The phase can be obtained by calculating the arctangent of the ratio of the harmonic coefficients of the displacement error. According to the sampling theorem, k + 1 nodes are extracted within the curve period. Assuming the maximum number of fitting period terms is n(k + 1), the coefficient values of the inverse Fourier series fitting error function are:

[0074] (7)

[0075] Thus, the cosine and sine harmonic coefficients of each order of the displacement error curve are obtained. After comparison and screening, the harmonics with numerical values greater than the set threshold and having an impact on the error result exceeding the set error threshold, namely the 0th, 2nd, and 4th harmonics, are used to achieve the compensation and reconstruction of the displacement sensor error data, Figure 4 showing the angular displacement error compensation effect of this method during the high-speed rotation of the turntable.

[0076] Step 5: Set the closed-loop control process of the turntable to ensure that the transfer function remains stable after parameter transformation. Assume that R is the input signal, C is the output signal, and N is the interference signal related to system friction and variable load. is the pre-control link, is the controlled object, and H is the transfer function of the closed-loop control system. According to the system signal superposition principle, the total output signal is:

[0077] (8)

[0078] Calculating the interpolation between the theoretical angular displacement and the actual angular displacement of the system can obtain the system error as , and the error change rate , and respectively represent and the first derivatives.

[0079] Step 6: Compare the actual rotational speed and the desired rotational speed of the high-speed turntable motor obtained in Step 4, and input the error e and the error change rate To the fuzzy controller, specifically, the fuzzy controller uses the output to correct the parameters of the PID controller online to achieve the expected control effect. If the error e and the error change rate Are used as the input variables of the fuzzy PID controller. According to the domain of the quantization factor and the proportionality factor, the proportionality coefficient is set The fuzzy universe of discourse is {-3, -2, -1, 0, 1, 2, 3}, and the integral coefficient is set And the differential coefficient The fuzzy universe of discourse is {-0.3, -0.2, -0.1, 0, 0.1, 0.2, 0.3}. The fuzzy sets describing the input and output are {NB, NM, NS, Z, PS, PM, PB}. According to the engineering common combination of trigonometric functions and Gaussian membership functions, the membership functions for the fuzzy controller are Figure 5 Display the distribution curve of the membership function combining the trigonometric function and the Gaussian membership function of the error e

[0080] Step 7: Detect the turntable error and output the fuzzy control self-adjusting parameters Used to correct the control parameters. The specific method is to perform reasoning respectively according to the fuzzy control rules of the parameters in combination with the minimum operation method to obtain the fuzzification result Among them Represents the error e and the error change rate The intermediate value after fuzzy reasoning, and then defuzzification is performed based on the centroid method to obtain Taking the proportionality coefficient as an example, it can be obtained:

[0081] (9)

[0082] Based on the fuzzy controller, the adjustment parameters are obtained, and the original control parameters of the PID controller are corrected to obtain , , And Represents the PID parameters obtained from the previous correction. Continuously adjust the response rate, oscillation amplitude and stabilization time of the variable load turntable system.

[0083] Step 8: According to the PID control parameters given in Step 7, adjust the driving state of the servo motor, transmit the corrected PID parameter signal to the servo motor driver, adjust the output current of the servo motor to compare the torque, speed and position of the turntable system, and then realize the continuous adaptive control of the high-speed turntable speed.

[0084] Figure 6 It is shown that under the action of the pulse signal, the response time of this method is shorter and the overshoot influence is weaker compared with the traditional method; Figure 7 It is shown that when a disturbance signal is given to the system, this method has stronger anti-interference ability and more stable system output compared with the traditional method.Figure 8 It shows that when continuously maintained as a sine signal, the system output under the action of this method is more in line with the set signal, and has better followability compared with the traditional method.

[0085] The embodiments described above are only a preferred solution of the present invention, but they are not intended to limit the present invention. Those of ordinary skill in the relevant technical field can also make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all technical solutions obtained by adopting the means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A high-speed turntable variable load adaptive control method, characterized in that: Based on the closed-loop control method combined with the fuzzy PID control algorithm and the displacement sensor error compensation model, the adaptive control of the high-speed turntable in the disturbance environment and the variable load working environment is realized, which specifically includes the following steps: Step 1: Get the initial state of the high-speed turntable and controller, and send closed-loop instructions for the required position and speed; Step 2: Establish the motor transfer function of the turntable drive servo system; Step 3: The displacement sensor detects the angular displacement of the high-speed turntable, obtains the interpolation function value of each data point according to the interpolation principle, and obtains the interpolation curve of the data; Step 4: Reconstruct the interpolation curve in step 3 to obtain the amplitude and phase information of each order harmonic and construct the sensor error compensation model; Step 5: Set the turntable closed-loop control process so that the transfer function remains stable after parameter transformation; Step 6: Compare the actual speed of the high-speed turntable motor obtained in step 4 with the expected speed, and input the error e and error change rate to fuzzy PID controller; Step 7: Detect turntable error and output fuzzy control self-adjustment parameters Used to modify control parameters; Step 8: Adjust the driving state of the servo motor according to the PID control parameters given in step 7 to achieve continuous adaptive control of the high-speed turntable speed.

2. The variable load adaptive control method for a high-speed turntable according to claim 1 is characterized in that: Step 1 is as follows: The host computer obtains basic information related to the high-speed turntable and servo motor, including speed limit, torque limit and safe operating parameters; performs the initialization process of checking hardware connections, calibrating sensors, and setting initial parameters; sends closed-loop control instructions of the required position and speed to the actuator according to the requirements of the machine tool processing workpiece, and starts the high-speed turntable through the servo amplifier drive motor.

3. A high-speed turntable variable load adaptive control method according to claim 1 or 2, characterized in that: Step 2 is as follows: Assuming that the mass and shape of each component in the turntable system are uniform, the friction force in the turntable system is As a function of the actual position and speed, the torque balance equation of the servo system is: (1) in, is the moment of inertia, is the actual angular displacement of the system, is the system speed, is the output torque, For system load, set is the theoretical angular displacement of the system, then the motor transfer function Can be considered as and If the ratio is the Laplace variable, is the motor reduction ratio, and the changed motor transfer function is: (2) The changed motor transfer function is used as the basis for subsequent feedback control.

4. The variable load adaptive control method for a high-speed turntable according to claim 3 is characterized in that: Step 3 is as follows: The improved center-of-gravity Lagrange interpolation method is used to calculate the values ​​near the discrete displacement angle points of the high-speed turntable recorded by the displacement sensor; K+1 nodes are taken on the data interval [a, b] , then the displacement angle value of the corresponding node for: (3) According to formula (4), the Lagrange basic polynomial is defined as and center of gravity , according to the improved Lagrange interpolation method, the values ​​near the K+1 finite node displacement points are calculated, that is, the interpolation polynomial near the end point of the data interval is used to deal with the problem of displacement curve oscillation caused by load changes, and the displacement angle value can be obtained for: (4) Thus, the displacement sensor position information and the corresponding sensor angle information are obtained.

5. The variable load adaptive control method for a high-speed turntable according to claim 4, characterized in that: Step 4 is as follows: Based on Fourier expansion and convergence theorem, the interpolation curve is reconstructed into a finite sine wave according to the relationship between phase, amplitude and frequency, and the sensor displacement error value is decomposed. for: (5) (6) in, is the harmonic order, is the constant term coefficient, is the cosine wave coefficient, is the error value sine wave frequency information, is the harmonic amplitude, and the phase can be obtained by calculating the inverse tangent of the ratio of the displacement error harmonic coefficients; according to the sampling theorem, k+1 nodes are extracted within the curve period, and the maximum number of fitted periodic terms is set to n(k+1), then the coefficient value of the Fourier series fitting error function is inversely calculated as: (7) Thus, the sine and cosine harmonic coefficients of each order of the interpolation curve are obtained. The harmonics whose values ​​are greater than the set threshold and whose influence on the error result exceeds the set error threshold, namely the 0th, 2nd and 4th order harmonics, realize the compensation reconstruction of the displacement sensor error data.

6. A high-speed turntable variable load adaptive control method according to claim 4, characterized in that: Step 5 is as follows: Assume that R is the input signal, C is the output signal, and N is the interference signal related to system friction and variable load. For the front control link, is the controlled object, H is the transfer function of the closed-loop control system, and according to the system signal superposition principle, the total output signal can be obtained as follows: (8) The interpolation of the theoretical angular displacement and the actual angular displacement of the calculation system can obtain the system error: , error change rate , and Respectively and The first derivative of .

7. A high-speed turntable variable load adaptive control method according to claim 6, characterized in that: Step 6 is as follows: The fuzzy controller uses the output to perform online correction on the parameters of the PID controller to achieve the desired control effect. If the system error e and the error change rate As the input variable of the fuzzy PID controller, the proportional coefficient is set according to the definition domain of the quantization factor and the proportional factor. The fuzzy domain is {-3,-2,-1,0,1,2,3}, and the integral coefficient is set and the differential coefficient The fuzzy domain is {-0.3, -0.2, -0.1, 0, 0.1, 0.2, 0.3}, the fuzzy set describing the input and output is {NB, NM, NS, Z, PS, PM, PB}, and the membership function of the fuzzy controller is a combination of trigonometric functions and Gaussian membership functions commonly used in engineering.

8. The variable load adaptive control method for a high-speed turntable according to claim 6, characterized in that: Step 7 is as follows: According to the fuzzy control rules of the parameters combined with the minimum operation algorithm, the fuzzy result is obtained. ,in Represents the system error e and the error change rate After the intermediate value of fuzzy inference, it is defuzzified based on the centroid method to obtain , proportionality coefficient We can get: (9) in, The solution and same; Based on the adjustment parameters obtained by the fuzzy controller, the original control parameters of the PID controller are corrected to obtain , , and Indicates the PID parameters obtained from the previous calibration.

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