High-precision anti-backlash servo control system based on virtual shaft transmission structure

Abstract

The application discloses a high-precision anti-backlash servo control system based on a virtual shaft transmission structure and belongs to the technical field of servo control systems.The application comprises left and right circular arc tracks, a pitch gear ring, a speed reducer, a motor, a coarse / fine channel synchronous gear train, coarse / fine channel rotary transformers, an angle code acquisition box, a load, a main control module and an anti-backlash driver; the coarse / fine channel rotary transformers respectively output a pitch angle analog voltage signal of the load to the angle code acquisition box and output a pitch angle digital value of the load in real time; the main control module receives the pitch angle digital value of the load, generates a pitch rotation speed instruction value in real time through antenna angle position closed-loop control and transmits the pitch rotation speed instruction value to the anti-backlash driver; the anti-backlash driver generates a driving instruction through motor current closed-loop control to drive the left and right motors to rotate, thereby realizing the rotation of the load. The application can effectively suppress eccentricity, friction and unknown ship rocking interference through an anti-interference strategy, thereby realizing high-precision servo positioning control.

Description

Technical Field

[0001] This invention belongs to the field of servo control system technology, specifically relating to a high-precision backlash-free servo control system based on a virtual shaft transmission structure. Background Technology

[0002] Large, heavy-duty servo transmission mechanisms inevitably have eccentricity. Even with the addition of counterweights, it is difficult to achieve a completely eccentric balance. The combined loads of eccentric torque, dynamic friction torque, and ship sway will have an adverse effect on high-precision servo control.

[0003] Furthermore, traditional anti-interference strategies, such as using interference observers to estimate and suppress external interference, often fail to differentiate between different types of interference. In reality, due to the limited bandwidth of interference observers, they cannot effectively suppress high-frequency interference. Therefore, it is necessary to design appropriate anti-interference controllers to overcome the effects of these combined interferences. Summary of the Invention

[0004] The purpose of this invention is to provide a high-precision backlash-free servo control system based on a virtual shaft transmission structure for large, heavy-duty virtual shaft transmission mechanisms. This system can effectively suppress interference from eccentricity, friction, and unknown ship sway through anti-disturbance strategies, thereby achieving high-precision servo positioning control.

[0005] Specifically, the present invention provides a high-precision backlash-eliminating servo control system based on a virtual shaft transmission structure, including a left circular arc track, a left pitch gear ring, a left reducer, a left motor, a coarse channel synchronous gear train, a coarse channel rotary transformer, a right circular arc track, a right pitch gear ring, a right reducer, a right motor, a fine channel synchronous gear train, a fine channel rotary transformer, a corner code acquisition box, a load, a main control module, and a backlash-eliminating driver;

[0006] The left and right circular arc tracks support the load; the coarse channel rotary transformer and the coarse channel synchronous gear train are coaxially mounted, and the fine channel rotary transformer and the fine channel synchronous gear train are coaxially mounted; the coarse channel synchronous gear train and the fine channel synchronous gear train are respectively meshed with the left pitch gear ring and the right pitch gear ring through gears; the left motor and the right motor are respectively coaxially mounted with the input shafts of the left reducer and the right reducer, and the output shafts of the left reducer and the right reducer are respectively meshed with the left pitch gear ring and the right pitch gear ring through gears; the coarse channel rotary transformer and the fine channel rotary transformer respectively output the pitch angle analog voltage signal of the load to the angle code acquisition box, and after combined calculation and zero value input, output the pitch angle digital value of the load in real time;

[0007] The main control module receives the pitch angle digital value of the load, generates a pitch rotation speed command value in real time through antenna angle position closed-loop control, and transmits it to the backlash elimination driver.

[0008] After receiving the pitch rotation speed command value, the backlash-free driver generates a drive command through motor current closed-loop control to drive the left and right motors to rotate, thereby realizing the rotation of the load.

[0009] Furthermore, the backlash elimination driver includes a speed loop correction module, a first speed feedback module, a second speed feedback module, an electrical backlash elimination control module, a first current loop correction module, a first current feedback module, a first PWM power amplifier, a first motor, a second current loop correction module, a second current feedback module, a second PWM power amplifier, and a second motor;

[0010] The first speed feedback module and the second speed feedback module respectively collect the rotational speeds of the first motor and the second motor, take the average speed, and calculate the error value between the average speed and the pitch rotation speed command value received in real time from the main control module. The error value is input to the speed loop correction module, and the control current I is calculated through motor speed closed-loop control. c ;

[0011] The electrical gap elimination control module calculates the bias current values ​​I of the first motor and the second motor based on the outputs of the first current feedback module and the second current feedback module, respectively. p The current settings for the first and second motors are respectively: I p +I c I c -I p ;

[0012] The first current loop correction module is based on the current given by the first motor I. p +I c The error between the current and the current of the first current feedback module is used to control the first PWM power amplifier in real time, and the first PWM power amplifier outputs the drive command to the first motor;

[0013] The second current loop correction module is based on the current input I of the second motor. c -I p The error between the current from the second current feedback module and the current is used to control the second PWM power amplifier in real time. The second PWM power amplifier outputs the drive command to the second motor, thus completing the closed-loop control of the motor speed.

[0014] Furthermore, the corner code acquisition box includes: an RDC module, a combination calculation module, a zero-value input module, and a data output module;

[0015] The RDC module converts the pitch angle analog voltage signal generated by the coarse-channel rotary transformer and the fine-channel rotary transformer into a digital pitch angle value. The combined calculation module calculates the digital pitch angle value in real time. Then, the zero-value input module receives the zero-deduction angle value input from the field CAN bus and subtracts it from the digital pitch angle value obtained by the combined calculation module to obtain the true pitch angle value, thus completing the zero-point calibration. Finally, the data output module outputs the true pitch angle value in real time as the digital pitch angle value of the load.

[0016] Furthermore, the RDC module adopts a 14-bit solution module, and the speed ratio of the coarse synchronization gear train and the fine synchronization gear train is selected as 16.

[0017] Furthermore, the main control module also includes an active disturbance rejection controller and a known interference compensation module;

[0018] The active disturbance rejection controller includes a PI controller and a second-order extended state observer. The PI controller is a position loop controller that performs closed-loop control of the antenna angle position. The second-order extended state observer estimates and compensates for ship roll interference. Specifically, the main control module periodically receives the digital value of the load's pitch angle θ from the angle code acquisition box and calculates in real time the estimated load angle z1 and the estimated ship roll angular velocity interference z2 from the second-order extended state observer, as well as the target angle θ. in The error e between the load angle estimate z1 and the PI controller and the second-order extended state observer outputs the pitch rotation speed command value u. The backlash elimination driver receives the pitch rotation speed command value and performs motor speed closed-loop control through the speed loop correction module and motor current closed-loop control through the current loop correction module, thereby realizing antenna angle position closed-loop control and compensation of ship roll angular velocity interference estimate.

[0019] The known interference compensation module realizes the eccentric torque M 偏心 With dynamic friction torque M 摩擦 Compensation;

[0020] Through the combined action of the speed loop correction module and the known interference compensation module, the input control current of the current loop correction module is I′. c ,

[0021] I' c =I c +I 补偿 (5)

[0022] Among them, I 补偿 Given the interference compensation current, I c This is the output of the speed loop correction module;

[0023] The input control current I′ of the current loop correction module c The bias current values ​​I are superimposed respectively p Or subtract the bias current value I p The current command I for the first motor and the second motor are obtained respectively. p +I′ c 、I′ c -I p Then, through the first current loop correction module, the first PWM power amplifier, the second current loop correction module, and the second PWM power amplifier, respectively, drive commands are output to drive the motor to complete rotation.

[0024] Furthermore, the PI controller expression is as follows:

[0025]

[0026] Where u0 is the output of the PI controller, k p Here, e is the proportional gain of the PI controller, e is the angle error term of the PI controller, and k is the angular gain of the PI controller. i is the integral coefficient of the PI controller, and s is the integral term of the PI controller;

[0027] The second-order extended state observer is as follows:

[0028]

[0029] Where e is the angle error term of the PI controller, z1 is the estimate of the angle state quantity x1 by the second-order extended state observer, y is the output angle of the high-precision backlash-free servo control system based on the virtual shaft transmission structure, z2 is the estimate of the speed disturbance by the second-order extended state observer, β1 and β2 are the coefficients of the second-order extended state observer, b0 is the speed coefficient, and u is the pitch rotation speed command value.

[0030] The pitch rotation speed command value u output by the active disturbance rejection controller is

[0031]

[0032] Furthermore, β1 = 2ω g β2=ω g 2 ω g This represents the observer bandwidth.

[0033] Furthermore, the known interference compensation module realizes the compensation of the eccentric torque M. 偏心 With dynamic friction torque M 摩擦 The compensation specifically includes:

[0034] The main control module receives the pitch angle digital value θ of the load output by the angle code acquisition box at set intervals and calculates the pitch rotation speed command value u in real time. When u is greater than 0, the eccentric torque M... 偏心 With dynamic friction torque M 摩擦 The compensation value is M 摩擦 -εmgcos(θ+φ); when u is less than 0, the eccentric torque M 偏心 With dynamic friction torque M 摩擦 The compensation value is εmgcos(θ+φ)+M 摩擦 Where ε is the load eccentricity, mg is the gravity acting on the load, and φ is the load eccentricity angle; the eccentric torque M 偏心 With dynamic friction torque M 摩擦 The compensation value is multiplied by the compensation coefficient and then directly compensated to the output of the speed loop correction module. The compensation coefficient is the ratio of the load torque to the motor current.

[0035] Furthermore, the load eccentricity ε, load eccentricity angle φ, and dynamic friction torque M 摩擦 Obtained through the following methods:

[0036] In a windless environment, the first and second motors were rotated in both forward and reverse directions. The current of each motor was recorded at equally spaced angles, and curves showing the relationship between the motor current and the angle were plotted for forward rotation from 0° to 90° and reverse rotation from 90° to 0°. Based on the known torque coefficients of each motor, torque curves for forward and reverse rotation were plotted, and the eccentric torque M was calculated. 偏心 With dynamic friction torque M 摩擦 By analyzing the sum and difference of the load eccentricity ε, the load eccentricity angle φ, and the dynamic friction torque M, we can obtain the following values: 摩擦 .

[0037] The beneficial effects of the high-precision backlash-free servo control system based on the virtual shaft transmission structure of the present invention are as follows:

[0038] To achieve high-precision servo control of the virtual shaft transmission system, this invention optimizes the design from three aspects: backlash elimination drive scheme, angle measuring device, and control strategy.

[0039] This invention employs a novel virtual shaft structure for its transmission mechanism. This structure has no physical rotating central shaft; instead, it uses a circular arc track to support the load, and a discontinuous large gear ring drives the load's rotation, offering advantages such as high support rigidity and high precision. A pair of large gear rings are symmetrically arranged, with the drive motors symmetrically positioned left and right, and an electrical backlash elimination scheme is used to eliminate the influence of backlash.

[0040] The angle measuring device of this invention employs a combination of coarse and fine resolver angle measurement. The coarse channel resolver and the fine channel resolver mesh with two large gear rings through synchronous gear trains, thereby improving the angle measurement accuracy. The control scheme of this invention, based on a virtual shaft structure and combining backlash-free drive with coarse and fine resolver angle measurement, provides both high-rigidity, backlash-free transmission power for the drive transmission link and high-precision real-time measurement values ​​of the load angle, thus laying a solid foundation for the construction of high-precision servo control systems in large-scale, heavy-load applications.

[0041] This invention classifies load interference into known eccentric torque, dynamic friction torque, and unknown ship rocking interference, and calculates the values ​​of eccentric torque and dynamic friction torque by using the motor current curves when rotating in different directions. The operation is convenient and simple.

[0042] This invention employs a comprehensive disturbance control strategy, which uses the load angle and rotation direction to calculate and compensate for known disturbance torque in real time, and uses an active disturbance rejection controller to estimate and compensate for unknown ship rocking disturbance in real time, thereby achieving high-precision servo positioning control. Attached Figure Description

[0043] Figure 1 This is a system principle block diagram of an embodiment of the present invention.

[0044] Figure 2 This is a control block diagram of the backlash-eliminating driver according to an embodiment of the present invention.

[0045] Figure 3 These are force analysis diagrams of the virtual axis structure and motor current curves during forward and reverse rotation according to an embodiment of the present invention. In this diagram, a) is a schematic diagram of the force analysis results of the virtual axis structure, b) is a schematic diagram of the eccentric torque variation curve with pitch angle, c) is a schematic diagram of the motor current variation curve with pitch angle during forward rotation from 0° to 90°, and d) is a schematic diagram of the motor current variation curve with pitch angle during reverse rotation from 90° to 0°.

[0046] Figure 4 This is a control block diagram of the comprehensive interference suppression strategy according to an embodiment of the present invention.

[0047] The diagram is labeled as follows: 1-Virtual shaft transmission structure, 101-Left circular arc track, 102-Left pitch gear ring, 103-Left reducer, 104-Left motor, 105-Coarse channel synchronous gear train, 106-Coarse channel rotary transformer, 201-Right circular arc track, 202-Right pitch gear ring, 203-Right reducer, 204-Right motor, 205-Fine channel synchronous gear train, 206-Fine channel rotary transformer, 3-Load. Detailed Implementation

[0048] The present invention will now be described in further detail with reference to the embodiments and the accompanying drawings.

[0049] Example 1:

[0050] One embodiment of the present invention is a high-precision backlash-free servo control system based on a virtual axis transmission structure, used to achieve high-precision servo positioning control for large, heavy-duty servo transmission mechanisms. The virtual axis is a non-physical rotating central axis, with a circular arc track supporting the load, and a discontinuous rotating large gear ring driving the load to rotate.

[0051] To achieve high-precision servo control of the virtual axis structure, this invention optimizes the design from the aspects of backlash elimination control, high-precision angle measurement, and disturbance rejection control strategies. Specifically:

[0052] like Figure 1 As shown, the high-precision backlash-eliminating servo control system based on the virtual shaft transmission structure of the present invention includes a left circular arc track, a left pitch gear ring, a left reducer, a left motor, a coarse channel synchronous gear train, a coarse channel rotary transformer, a right circular arc track, a right pitch gear ring, a right reducer, a right motor, a fine channel synchronous gear train, a fine channel rotary transformer, a corner code acquisition box, a load, a main control module, and a backlash-eliminating driver.

[0053] The left and right circular arc tracks serve as load-bearing components, providing support during the load's pitch and rotational motion. The coarse-channel rotary transformer and the coarse-channel synchronous gear train are coaxially mounted, as are the fine-channel rotary transformer and the fine-channel synchronous gear train. The coarse-channel and fine-channel synchronous gear trains mesh with the left and right pitch large gear rings, respectively, via gears. The left and right motors are coaxially mounted with the input shafts of the left and right reducers, respectively. The output shafts of the left and right reducers mesh with the left and right pitch large gear rings, respectively, via gears. The lengths of the left and right circular arc tracks, the left and right pitch large gear rings are determined based on the pitch rotation angle range, allowing for a certain margin, generally not exceeding 180°. Therefore, the circular arc tracks and pitch large gear rings of this invention are non-continuous rotating components.

[0054] The pitch angle change can be reflected by the sine and cosine analog voltage signals of the coarse-channel rotary transformer and the fine-channel rotary transformer, respectively. The coarse-channel rotary transformer and the fine-channel rotary transformer output the pitch angle analog voltage signal of the load to the angle code acquisition box, and after combination calculation and zero value input, the digital value of the pitch angle of the load is output in real time, realizing the measurement and output of the pitch angle.

[0055] The main control module receives the pitch angle digital value of the load output by the angle coder through the field CAN bus, generates the pitch rotation speed command value in real time through the antenna angle position closed-loop control, and transmits it to the gap-free driver.

[0056] After receiving the pitch and rotation speed command value, the backlash-free drive generates a drive command through motor current closed-loop control to drive the left and right motors to rotate, thereby realizing the rotation of the load.

[0057] By adopting a symmetrical layout of a pair of large gear rings (left pitch gear ring and right pitch gear ring) and a dual-motor drive scheme (left motor and right motor), the difficulties caused by the limited power of a single motor drive to the transmission mechanism design can be avoided. At the same time, with the backlash elimination driver, the backlash elimination drive of the left and right dual motors can be realized, effectively eliminating transmission backlash and improving servo control accuracy.

[0058] like Figure 2 As shown, the backlash elimination driver includes a speed loop correction module, a first speed feedback module, a second speed feedback module, an electrical backlash elimination control module, a first current loop correction module, a first current feedback module, a first PWM power amplifier, a first motor, a second current loop correction module, a second current feedback module, a second PWM power amplifier, and a second motor.

[0059] The backlash-free drive receives pitch and rotation speed commands from the main control module in real time. Through closed-loop motor speed control and a preset backlash-free bias current, it achieves zero-backlash, angular-second-level precision control of the load. Details are as follows:

[0060] The first and second speed feedback modules respectively collect the rotational speeds of the first and second motors. After taking the average speed, they calculate the error value between this average speed and the pitch rotation speed command value received in real time from the main control module. The error value is input to the speed loop correction module, and the control current I is calculated through motor speed closed-loop control. c The backlash elimination control module calculates the bias current values ​​I of the first motor and the second motor based on the outputs of the first current feedback module and the second current feedback module, respectively. p The current settings for the first and second motors are respectively: I p +I c I c -I p .

[0061] The first current loop correction module is based on the current given by the first motor I. p +I c The error between the current from the first current feedback module and the current from the second current feedback module is used to control the first PWM power amplifier in real time. The first PWM power amplifier outputs the drive command to the first motor. The second current loop correction module adjusts the current according to the current given by the second motor. c -I p The error between the current and the current of the second current feedback module is used to control the second PWM power amplifier in real time. The second PWM power amplifier outputs the drive command to the second motor, thereby ensuring that the motor current changes in real time with the change of the current given, completing the closed-loop control of the motor current, and then realizing the closed-loop control of the motor speed by the servo control of the current.

[0062] Preferably, the angle measuring device of the present invention adopts a combination of coarse and fine rotary angle measuring methods, which can increase the number of angle measuring bits to more than 18 bits, achieving angle measuring accuracy at the arcsecond level, thereby laying the foundation for high-precision servo control. Figure 1 As shown, the coarse-channel rotary transformer and the fine-channel rotary transformer mesh with the left and right pitch ring gears through the coarse-channel synchronous gear train and the fine-channel synchronous gear train, respectively. The load angle is transmitted to the coarse-channel rotary transformer and the fine-channel rotary transformer in the synchronous gear train. The angle code acquisition box includes: an RDC (Resolver-to-Digital Converter) module, a combined solution module, a zero-value input module, and a data output module.

[0063] The RDC module converts the pitch angle analog voltage signals generated by the coarse-channel and fine-channel rotary transformers into digital angle values. The combined calculation module then calculates the digital pitch angle value in real time, achieving arcsecond-level angle measurement. The zero-value input module receives the zero-deduction angle value from the field CAN bus and subtracts it from the digital pitch angle value obtained from the combined calculation module to obtain the true pitch angle value, completing zero-point calibration. The data output module then outputs the true pitch angle value in real time as the digital pitch angle value for the load, realizing the measurement and output of the pitch angle. The main control module receives the true pitch angle value output from the angle code acquisition box via the fieldbus and completes closed-loop angle control.

[0064] Preferably, the RDC module uses a 14-bit calculation module, and the coarse and fine synchronous gear train speed ratio is selected as 2^4 = 16. Then the angle measurement accuracy can achieve an accuracy of 14 + 4 = 18 bits or more, corresponding to 360° / 2^18 × 3600 = 4.9 arcseconds. Even considering the transmission error, the angle measurement accuracy is still in the arcsecond range.

[0065] To optimize the design of disturbance rejection control strategies, this invention analyzes the disturbances experienced by the servo control system. The force analysis results of the servo control system employing a virtual shaft drive structure are as follows: Figure 3 As shown in a), the external disturbances to the servo control system mainly include the eccentric torque M. 偏心 Dynamic friction torque M 摩擦 Unknown interference M 未知 Comprehensive interference, etc.

[0066] Due to the eccentric moment M 偏心 This is mainly caused by the deviation between the center of mass and the center of rotation. When the load rotates from 0° to 90°, the eccentric torque M 偏心 The eccentric torque M varies cosinely with the angle. 偏心 =εmgcos(θ+φ), where ε is the load eccentricity, mg is the gravity acting on the load, and φ is the load eccentricity angle. The curve of eccentric torque as a function of pitch angle is shown below. Figure 3As shown in b), the gravity mg can generally be accurately known during design and installation, but the eccentricity ε and eccentricity angle φ are difficult to determine in terms of specific values ​​during design and installation.

[0067] If structural deformation and other factors are not considered, the dynamic friction torque M of the circular arc track is... 摩擦 It can be considered a constant, and it is opposite to the direction of rotation.

[0068] For shipborne servo systems, without considering wind load, the unknown interference M 未知干扰 The main issue is ship rolling interference. Ship rolling interference M 船摇 This is caused by the swaying of the moving platform under the influence of waves, etc. For example... Figure 4 As shown, ship rocking interference M 船摇 This will superimpose a sinusoidal curve onto the angle feedback, causing the load normal to oscillate periodically, affecting positioning accuracy. (Boat rocking interference M) 船摇 It can be considered as random interference, and its amplitude and period cannot be known in advance, but the characteristics of ship rocking interference determine that its frequency is low.

[0069] Due to the eccentric moment M 偏心 Dynamic friction torque M 摩擦 The interference acts directly on the torque end and has a high frequency, making it difficult to effectively suppress using interference suppression strategies based on interference observers. However, the eccentric torque M... 偏心 and kinetic friction torque M 摩擦 Measurements can be performed directly. In a windless environment, the first and second motors can be rotated in both forward and reverse directions. By recording the current of each motor at equally divided angles, curves showing the relationship between the motor current and the angle can be plotted for forward rotation from 0° to 90° and reverse rotation from 90° to 0°. Figure 3 As shown in c) and d), based on the known torque coefficients of each motor, the torque curves for forward and reverse rotation are plotted respectively, and the eccentric torque M is calculated. 偏心 With dynamic friction torque M 摩擦 The sum and difference of these values ​​can be used to analyze and determine the load eccentricity ε, load eccentricity angle φ, and dynamic friction torque M. 摩擦 To avoid measurement errors, multiple measurements can be recorded and the average value taken.

[0070] Preferably, considering the characteristics of different types of interference, and in order to effectively suppress combined interference and achieve high-precision servo control, in another embodiment, a method for combined interference suppression is proposed, the control block diagram of which is shown below. Figure 4 As shown. The high-precision backlash-free servo control system based on the virtual shaft transmission structure of the present invention also includes an active disturbance rejection controller and a known interference compensation module.

[0071] The active disturbance rejection controller completes the closed-loop position control of the servo control system and estimates and compensates for ship rolling disturbances. The known disturbance compensation module compensates for the aforementioned known eccentric torque M.偏心 and kinetic friction torque M 摩擦 Compensation. The speed loop correction module and the current loop correction module, in situations such as... Figure 2 The backlash-free actuator shown implements closed-loop control of motor speed and closed-loop control of motor current, respectively. The transmission chain consists of a motor, a reducer, and a pitch ring gear, completing the rotational power transmission from the motor to the load. A detailed explanation follows:

[0072] The active disturbance rejection controller (ADRC) comprises a PI controller and a second-order extended state observer. The PI controller is a position loop controller, performing closed-loop control of the antenna angle position; the second-order extended state observer estimates and compensates for ship roll disturbances. Specifically, it includes:

[0073] The main control module periodically receives the digital value of the pitch angle θ of the load output by the angle code acquisition box, and calculates in real time the estimated load angle z1 and the estimated ship roll rate disturbance z2 of the second-order extended state observer, as well as the target angle θ. in The error e between the estimated load angle z1 and the PI controller and the second-order extended state observer outputs the pitch rotation speed command value u. The backlash-free driver receives the pitch rotation speed command value and performs closed-loop control of motor speed through the speed loop correction module and closed-loop control of motor current through the current loop correction module, thereby realizing closed-loop control of antenna angle position and compensation of the estimated ship roll rate interference.

[0074] When designing a second-order extended state observer, the following state-space model of the servo system needs to be established first:

[0075]

[0076] Where x1 is the angle state quantity of the high-precision backlash-free servo control system (hereinafter referred to as the system) based on the virtual shaft transmission structure of this invention, b0 is the speed coefficient, u is the pitch rotation speed command value, w0 is the speed disturbance, b1 is the torque coefficient, and F e w1 is the system control torque, w1 is the external disturbance torque, and y is the system output angle, i.e., y = θ, where θ is the digital value of the pitch angle of the load output by the angle code acquisition box.

[0077] As can be seen from the above analysis, under windless conditions, w1 can be approximated as the eccentric moment M. 偏心 With dynamic friction torque M 摩擦 The superposition of these factors will be compensated by the known interference compensation module, and its influence can be ignored here. The speed interference w0 is mainly the ship's roll angular velocity interference, i.e.

[0078] The second-order extended state observer is designed as follows:

[0079]

[0080] Where e is the angle error term of the PI controller, z1 is the estimate of the angle state quantity x1 by the second-order extended state observer, y is the output angle of the high-precision backlash-free servo control system based on the virtual shaft transmission structure, z2 is the estimate of the speed disturbance w0 by the second-order extended state observer, β1 and β2 are the coefficients of the second-order extended state observer, b0 is the speed coefficient, and u is the pitch rotation speed command value. According to the pole placement method, β1 can be set to 2ω. g β2=ω g 2 ω g The observer bandwidth is typically 3-5 times the position loop bandwidth.

[0081] The PI controller, acting as a position loop controller, achieves closed-loop angle control. The PI controller expression is as follows:

[0082]

[0083] Where u0 is the output of the PI controller, k p Here, e is the proportional gain of the PI controller, e is the angle error term of the PI controller, and k is the angular gain of the PI controller. i is the integral coefficient of the PI controller, and s is the integral term of the PI controller.

[0084] Therefore, the pitch rotation speed command u output by the active disturbance rejection controller in the main control module is:

[0085]

[0086] Where, k p k i Parameter values ​​can be selected based on engineering experience.

[0087] Preferably, in another embodiment, the design process of the integrated disturbance rejection control strategy is as follows:

[0088] The angle closed-loop control cycle of the main control module is set to 10ms. First, it receives the high-precision digital value of the load's pitch angle θ from the angle code acquisition box at 10ms intervals. Within the 10ms interval, it calculates in real-time the load angle z1 and the estimated ship roll rate disturbance z2 from the second-order extended state observer, as well as the target angle θ. inThe error e between the estimated load angle z1 and the position loop PI controller is converted into a pitch rotation speed command u through the coordinated action of the position loop PI controller and the second-order extended state observer. The backlash-free driver receives the pitch rotation speed command u from the main control module and achieves closed-loop control of the antenna angle position and compensation for ship roll angular velocity interference through precise control of the motor speed. Under sea state 5, the amplitude and period of ship roll interference are generally 3-10° and 10-20s, respectively. Therefore, based on the inherent structural characteristics of the virtual shaft drive structure, if the structural resonant frequency is 5Hz, the bandwidth of the extended state observer of the active disturbance rejection controller can be designed to be 3-5Hz, and the bandwidth of the position loop PI controller can be designed to be 0.6-1Hz, which can effectively suppress ship roll interference.

[0089] For the eccentric moment M 偏心 and kinetic friction torque M 摩擦 To compensate for known interference, based on the above analysis, the sign of the motor speed command can be used to determine the antenna's rotation direction, and the eccentric torque M of the known interference can be calculated in real time. 偏心 and kinetic friction torque M 摩擦 The compensation value for known interference is as follows:

[0090] The main control module periodically receives the pitch angle digital value θ of the load output by the angle code acquisition box and calculates the pitch rotation speed command value u in real time. When u is greater than 0, the eccentric torque M... 偏心 With dynamic friction torque M 摩擦 The compensation value is M 摩擦 -εmgcos(θ+φ); when u is less than 0, the eccentric torque M 偏心 With dynamic friction torque M 摩擦 The compensation value is εmgcos(θ+φ)+M 摩擦 Where ε is the load eccentricity, mg is the gravity acting on the load, and φ is the load eccentricity angle; the eccentric torque M 偏心 With dynamic friction torque M 摩擦 The compensation value, multiplied by the compensation coefficient, is directly applied to the output of the speed loop correction module, improving the accuracy of tracking motor speed commands. The compensation coefficient can be the ratio of the load torque to the motor current. Through the combined action of the speed loop correction module and the known interference compensation module, the input control current of the current loop correction module is reduced from I... c Transform into I′ c , is represented as:

[0091] I' c =I c +I 补偿 (5)

[0092] Among them, I 补偿 Given the interference compensation current, I cThis is the output of the speed loop correction module.

[0093] Finally, as Figure 2 As shown, the control current command I′ c Superimposed bias current I p Or subtract the bias current I p The current command I for the first motor and the second motor can be obtained respectively. p +I′ c 、I′ c -I p Then, through the current loop correction module and PWM power amplifier, the PWM control quantity is output to drive the motor to complete the rotation action, thus completing the high-precision anti-interference closed-loop control process. Through the above design process, an isolation effect of about 30 to 100 times against ship rocking interference can be achieved, and the positioning control accuracy reaches the arcsecond level, thereby realizing high-precision closed-loop control of the virtual shaft transmission system.

[0094] The high-precision backlash-eliminating servo control system based on a virtual axis transmission structure of the present invention adopts a novel virtual axis structure transmission mechanism. This structure has no physical rotating central shaft, uses an arc track to support the load, and a discontinuous large gear ring drives the load to rotate, which has the advantages of good support rigidity and high precision. A pair of large gear rings are symmetrically arranged, the drive motors are symmetrically arranged on the left and right, and the influence of backlash is eliminated through an electrical backlash elimination scheme.

[0095] The angle measuring device of this invention employs a combination of coarse and fine resolver angle measurement. The coarse channel resolver and the fine channel resolver mesh with two large gear rings through synchronous gear trains, thereby improving the angle measurement accuracy. The control scheme of this invention, based on a virtual shaft structure and combining backlash-free drive with coarse and fine resolver angle measurement, provides both high-rigidity, backlash-free transmission power for the drive transmission link and high-precision real-time measurement values ​​of the load angle, thus laying a solid foundation for the construction of high-precision servo control systems in large-scale, heavy-load applications.

[0096] This invention classifies load interference into known eccentric torque, dynamic friction torque, and unknown ship rocking interference, and calculates the values ​​of eccentric torque and dynamic friction torque by using the motor current curves when rotating in different directions. The operation is convenient and simple.

[0097] This invention employs a comprehensive disturbance control strategy, which uses the load angle and rotation direction to calculate and compensate for known disturbance torque in real time, and uses an active disturbance rejection controller to estimate and compensate for unknown ship rocking disturbance in real time, thereby achieving high-precision servo positioning control.

[0098] While the present invention has been disclosed above with reference to preferred embodiments, these embodiments are not intended to limit the invention. Any equivalent changes or modifications made without departing from the spirit and scope of the invention are also within the scope of protection of the invention. Therefore, the scope of protection of the present invention should be determined by the claims of this application.

Claims

1. A high-precision backlash-free servo control system based on a virtual shaft transmission structure, characterized in that, It includes a left circular arc track, a left pitch gear ring, a left reducer, a left motor, a coarse channel synchronous gear train, a coarse channel rotary transformer, a right circular arc track, a right pitch gear ring, a right reducer, a right motor, a fine channel synchronous gear train, a fine channel rotary transformer, a corner code acquisition box, a load, a main control module, and a backlash elimination driver; the backlash elimination driver includes a speed loop correction module, a first speed feedback module, a second speed feedback module, an electrical backlash elimination control module, a first current loop correction module, a first current feedback module, a first PWM power amplifier, a first motor, a second current loop correction module, a second current feedback module, a second PWM power amplifier, and a second motor; The left and right circular arc tracks support the load; the coarse channel rotary transformer and the coarse channel synchronous gear train are coaxially mounted, and the fine channel rotary transformer and the fine channel synchronous gear train are coaxially mounted; the coarse channel synchronous gear train and the fine channel synchronous gear train are respectively meshed with the left pitch gear ring and the right pitch gear ring through gears; the left motor and the right motor are respectively coaxially mounted with the input shafts of the left reducer and the right reducer, and the output shafts of the left reducer and the right reducer are respectively meshed with the left pitch gear ring and the right pitch gear ring through gears; the coarse channel rotary transformer and the fine channel rotary transformer respectively output the pitch angle analog voltage signal of the load to the angle code acquisition box, and after combined calculation and zero value input, output the pitch angle digital value of the load in real time; The main control module receives the digital value of the pitch angle of the load, generates a pitch rotation speed command value in real time through closed-loop control of the antenna angle position, and transmits it to the backlash-free driver. The main control module also includes an active interference rejection controller and a known interference compensation module. The active interference rejection controller includes a PI controller and a second-order extended state observer. The PI controller is a position loop controller that completes closed-loop control of the antenna angle position. The second-order extended state observer estimates and compensates for ship roll interference. Specifically, the main control module periodically receives the digital value of the pitch angle of the load output from the angle code acquisition box. It also calculates in real time the load angle estimate z1 and the ship roll rate disturbance estimate z2 of the second-order extended state observer, as well as the target angle. The error e between the estimated load angle z1 and the PI controller and the second-order extended state observer outputs the pitch rotation speed command value. The backlash-eliminating driver receives the pitch rotation speed command value and performs closed-loop control of the motor speed through the speed loop correction module and closed-loop control of the motor current through the current loop correction module, thereby achieving closed-loop control of the antenna angle position and compensation for the estimated value of the ship roll angular velocity interference; the known interference compensation module realizes the compensation of the eccentric torque M. 偏心 With dynamic friction torque M 摩擦 The compensation; through the combined action of the speed loop correction module and the known interference compensation module, the input control current of the current loop correction module is , （5） in, Given the known interference compensation current, This is the output of the speed loop correction module; The input control current of the current loop correction module Superimpose bias current values ​​respectively Or subtract the bias current value The current commands for the first motor and the second motor are obtained respectively. , Then, after passing through the first current loop correction module, the first PWM power amplifier, the second current loop correction module, and the second PWM power amplifier respectively, a drive command is output to drive the motor to complete rotation; the known interference compensation module realizes the correction of the eccentric torque M 偏心 With dynamic friction torque M 摩擦 The compensation specifically includes: The main control module periodically receives the pitch angle digital values ​​of the load output by the angle code acquisition box. And calculate the pitch and rotation speed command value in real time. ,when When greater than 0, the eccentric torque M 偏心 With dynamic friction torque M 摩擦 The compensation value is M 摩擦 -εmgcos(θ+ϕ); when When less than 0, the eccentric torque M 偏心 With dynamic friction torque M 摩擦 The compensation value is εmgcos(θ+ϕ)+M 摩擦 Where ε is the load eccentricity, mg is the gravity acting on the load, and ϕ is the load eccentricity angle; the eccentric torque M 偏心 With dynamic friction torque M 摩擦 The compensation value is multiplied by the compensation coefficient and then directly compensated to the output of the speed loop correction module. The compensation coefficient is the ratio of the load torque to the motor current. After receiving the pitch rotation speed command value, the backlash-free driver generates a drive command through motor current closed-loop control to drive the left and right motors to rotate, thereby realizing the rotation of the load.

2. The high-precision backlash-free servo control system based on a virtual shaft transmission structure according to claim 1, characterized in that, The first speed feedback module and the second speed feedback module respectively collect the rotational speeds of the first motor and the second motor, take the average speed, and calculate the error value between the average speed and the pitch rotation speed command value received in real time from the main control module. The error value is input to the speed loop correction module, and the control current is calculated through motor speed closed-loop control. ; The electrical gap elimination control module calculates the bias current values ​​of the first motor and the second motor based on the outputs of the first current feedback module and the second current feedback module, respectively. The current settings for the first and second motors are as follows: , ; The first current loop correction module is based on the current given by the first motor. The error between the current and the current of the first current feedback module is used to control the first PWM power amplifier in real time, and the first PWM power amplifier outputs the drive command to the first motor; The second current loop correction module is based on the current given by the second motor. The error between the current from the second current feedback module and the current is used to control the second PWM power amplifier in real time. The second PWM power amplifier outputs the drive command to the second motor, thus completing the closed-loop control of the motor speed.

3. The high-precision backlash-free servo control system based on a virtual shaft transmission structure according to claim 1, characterized in that, The corner code acquisition box includes: an RDC module, a combination calculation module, a zero value input module, and a data output module; The RDC module converts the pitch angle analog voltage signal generated by the coarse-channel rotary transformer and the fine-channel rotary transformer into a digital pitch angle value. The combined calculation module calculates the digital pitch angle value in real time. Then, the zero-value input module receives the zero-deduction angle value input from the field CAN bus and subtracts it from the digital pitch angle value obtained by the combined calculation module to obtain the true pitch angle value, thus completing the zero-point calibration. Finally, the data output module outputs the true pitch angle value in real time as the digital pitch angle value of the load.

4. The high-precision backlash-free servo control system based on a virtual shaft transmission structure according to claim 3, characterized in that, The RDC module uses a 14-bit solution module, and the speed ratio of the coarse synchronization gear train and the fine synchronization gear train is selected as 16.

5. The high-precision backlash-free servo control system based on a virtual shaft transmission structure according to claim 1, characterized in that, The PI controller expression is as follows: （3） in, For PI controller output, Here, e represents the proportional gain of the PI controller, and 'e' represents the angle error term of the PI controller. The integral coefficient of the PI controller. For the integral term of the PI controller; The second-order extended state observer is as follows: （2） Where e is the angle error term of the PI controller, and z1 is the estimate of the angle state variable x1 by the second-order extended state observer. Let z1 be the output angle of the high-precision backlash-free servo control system based on the virtual shaft transmission structure, and z2 be the estimate of the speed disturbance by the second-order extended state observer. , These are the coefficients of the second-order extended state observer. For speed coefficient, This is the pitch and rotation speed command value; The pitch rotation speed command value output by the active disturbance rejection controller for （4）。 6. The high-precision backlash-free servo control system based on a virtual shaft transmission structure according to claim 5, characterized in that, β1=2ω g β2=ω g 2 ω g This represents the observer bandwidth.

7. The high-precision backlash-free servo control system based on a virtual shaft transmission structure according to claim 1, characterized in that, The load eccentricity ε, load eccentricity angle ϕ, and dynamic friction torque M 摩擦 Obtained through the following methods: In a windless environment, the first and second motors were rotated in the forward and reverse directions respectively. By recording the current of each motor at equally divided angles, the relationship curves between the current of each motor and the angle were plotted when rotating forward from 0° to 90° and when rotating in the reverse direction from 90° to 0°. Based on the known torque coefficients of each motor, torque curves for forward and reverse rotation are plotted, and the eccentric torque M is calculated. 偏心 With dynamic friction torque M 摩擦 By analyzing the sum and difference of the load eccentricity ε, the load eccentricity angle ϕ, and the dynamic friction torque M, we can obtain the load eccentricity ε, the load eccentricity angle ϕ, and the dynamic friction torque M. 摩擦 .

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