Device and method for improving contour accuracy of direct-drive xy motion platform servo system

Abstract

This invention provides a device and method for improving the contour accuracy of a direct-drive XY motion platform servo system, relating to the field of CNC motion control technology. The device includes a rectifier filter circuit, an IPM inverter circuit, a detection circuit, a DSP processor, an IPM isolation protection drive circuit, a host computer, and a direct-drive XY motion platform. The method first calculates the contour error using a reference-adjusted contour error estimation method, which serves as the input to an adaptive nonlinear sliding mode contour controller. Then, the adaptive nonlinear sliding mode contour controller is used to control the contour error, and a nonlinear sliding surface is designed to improve the system's dynamic response speed and contour tracking accuracy. To further reduce the error between the reference model and the actual object, an uncertainty compensator is designed to compensate for uncertainties such as parameter changes, external disturbances, and friction, thereby improving the system's robustness.

Description

Technical Field

[0001] This invention relates to the field of CNC motion control technology, and in particular to a device and method for improving the contour accuracy of a direct-drive XY motion platform servo system. Background Technology

[0002] The rapid development of information technology, biotechnology, aerospace, and other scientific and technological fields has brought about a tremendous transformation in the manufacturing industry. CNC machine tools are the "mother machines" of manufacturing, and the CNC system is the brain of these machine tools, a key factor determining their performance, functionality, reliability, and cost. The current global trend in CNC technology development is towards high speed, high precision, intelligence, grid-based systems, flexibility, and environmental friendliness. However, compared with advanced machine tool manufacturing levels abroad, my country's high-end CNC machine tools still need further improvement in quality and performance. Therefore, focusing on overcoming the high-precision technological bottlenecks in high-end CNC systems and functional components, and developing strategic technologies and products, will not only meet market demand but also enhance national economic strength and international competitiveness.

[0003] The direct-drive XY motion platform is a key functional component for realizing planar XY coordinate motion in multi-axis high-end CNC machine tools. It consists of two orthogonally placed permanent magnet linear synchronous motors and boasts advantages such as high speed, high precision, and high efficiency. It is widely used in high-speed precision measurement systems, electronic and semiconductor processing equipment, and automation equipment. The permanent magnet linear synchronous motor uses linear transmission, replacing the traditional "rotary motor + ball screw" transmission method, offering advantages such as high thrust, low friction, low loss, fast response, and high precision. However, the inherent end effect and magnetic circuit interruption phenomenon of the permanent magnet linear synchronous motor cause fluctuations in its thrust. Furthermore, because the direct-drive transmission system eliminates intermediate transmission links such as gears and couplings, achieving rigid coupling between the power source and the load, uncertainties such as nonlinear friction, end effect, external disturbances, and cogging effect directly act on the motor mover, thus affecting the single-axis position tracking accuracy. Furthermore, contour error is also a crucial indicator for evaluating the machining accuracy of direct-drive XY motion platforms and a significant measure of the surface quality of workpieces machined by the platform. It is primarily affected by single-axis tracking error and multi-axis linkage coordination, directly influencing the shape of the machined contour. Mechanical coupling issues and parameter mismatches between the two linear motors can reduce the contour tracking accuracy of the direct-drive XY motion platform, resulting in contour machining performance that fails to meet the requirements of practical applications. Therefore, reducing or minimizing contour error while ensuring single-axis position tracking accuracy and solving the challenge of precise contour tracking control is a vital task for the multi-axis machining industry.

[0004] In summary, to improve the contour tracking performance of the direct-drive XY motion platform servo system, it is necessary to design a contour tracking control strategy suitable for the direct-drive XY motion platform, so as to meet the high-precision and robust servo system performance requirements of CNC technology. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a device and method for improving the contour tracking accuracy of a direct-drive XY motion platform servo system.

[0006] On the one hand, a device for improving the contour tracking accuracy of a direct-drive XY motion platform servo system includes a rectifier filter circuit, an IPM inverter circuit, a detection circuit, a DSP processor, an IPM isolation protection drive circuit, a host computer, and a direct-drive XY motion platform;

[0007] The rectifier and filter circuit and the IPM inverter circuit together form the power supply section. The input terminal of the rectifier and filter circuit is connected to the three-phase AC power supply, and the output terminal of the rectifier and filter circuit is connected to the IPM inverter circuit. The output terminal of the IPM inverter circuit is connected to and supplies power to the permanent magnet linear synchronous motor.

[0008] The detection circuit includes a current detection circuit, a Hall sensor, a position and speed detection circuit, and a linear grating ruler; wherein the input terminal of the current detection circuit is connected to the output terminal of the IPM inverter circuit through the Hall sensor, and the output terminal of the current detection circuit is connected to one signal input terminal of the DSP processor; the input terminal of the position and speed detection circuit is connected to the output terminal of the permanent magnet linear synchronous motor through the linear grating ruler, and the output terminal of the position and speed detection circuit is connected to another signal input terminal of the DSP processor;

[0009] The DSP processor is a DSP processor chip and its peripheral circuits. The PWM port of the DSP processor is connected to another input terminal of the IPM inverter circuit through the IPM isolation protection drive circuit.

[0010] The direct-drive XY motion platform consists of a marble base, two permanent magnet linear synchronous motors, a linear motor mounting bed, a motor mounting bracket, a mover worktable, linear guides, and a grating detection device. The two permanent magnet linear synchronous motors are mounted on the linear motor mounting bed in an XY orthogonal configuration via the motor mounting bracket. The lower motor is the X-axis motor, and the upper motor is the Y-axis motor. The stators of the permanent magnet linear synchronous motors are alternately equipped with N-pole and S-pole permanent magnets, and the movers are equipped with armature windings. The linear motor mounting bed is fixed to the marble base. The material is cast iron, and shims for adjusting height and balance are set under the linear motor mounting bed. The motor mounting bracket is made of aluminum alloy, and the grating detection device is attached to its surface. The reading head of the grating detection device is bolted to the movers of the X-axis motor and the Y-axis motor. The Y-axis motor is mounted on the mover platform of the X-axis motor. At the same time, the mover worktable is connected to the mover coil of the Y-axis, thereby realizing the movement of the XY motion platform. The mover coils of the X-axis motor and the Y-axis motor are both supported by the linear guide rails. Both axes adopt a double rolling guide rail design.

[0011] The host computer processes the data collected by the current, position, and speed detection circuits through a control program. Then, it calculates the difference between the collected data and the desired command signal and inputs it into the reference adjustment contour error model. The contour error is then calculated as the input variable of the adaptive nonlinear sliding mode contour controller. The adaptive nonlinear sliding mode contour control algorithm is executed, and an uncertainty compensator is designed. Finally, the core algorithm based on the adaptive nonlinear sliding mode contour control and the uncertainty compensator is written as a C language program and downloaded to the DSP processor via the SCI serial port bus. This drives the two permanent magnet linear synchronous motors in the direct drive XY motion platform servo system.

[0012] On the other hand, a method for improving the contour tracking accuracy of a direct-drive XY motion platform servo system, based on the aforementioned apparatus and method for improving the contour tracking accuracy of a direct-drive XY motion platform servo system, specifically includes the following steps:

[0013] Step 1: Input the desired position signals of the X-axis motor and Y-axis motor in the direct drive XY motion platform. The two permanent magnet linear synchronous motors receive the desired position and start moving.

[0014] Step 2: Collect the actual position, speed, and current of the movers of the two permanent magnet linear synchronous motors, specifically:

[0015] After the two motors in the direct-drive XY motion platform are running, the current of the mover is collected by the Hall sensor; the linear grating ruler outputs two-phase orthogonal square wave pulse signals and zero-position pulse signals through the position and speed detection circuit, for a total of three pulse signals; the pulse signals are sent to the orthogonal encoding pulse input unit EQEP of the DSP processor chip, and the encoder resolution is improved by four-fold frequency multiplication. At the same time, the general-purpose timer is set to directional increment / decrement counting mode. The position offset of the mover is obtained from the number of pulses of the two-phase orthogonal square wave pulse signals, and the direction of rotation of the mover is obtained from the lead relationship of the two-phase pulses, thus obtaining the actual position and speed of the mover.

[0016] Step 3: Using the actual positions of the two permanent magnet linear synchronous motors acquired in Step 2, the single-axis position tracking error is first calculated in the DSP. The equivalent contour error is then calculated by referencing the contour error model and input into the adaptive nonlinear sliding mode contour controller to reduce the contour error. An uncertainty compensator is designed to compensate for external disturbances, parameter changes, and nonlinear friction. Based on the influence of uncertainties on the system, the overall control law, i.e., the current control signal, based on the adaptive nonlinear sliding mode contour control and the uncertainty compensator, is finally calculated. The specific steps are as follows:

[0017] Step 3.1: Establish a servo system model for the direct-drive XY motion platform, including the dynamic model of the direct-drive XY motion platform and the reference adjustment profile error model;

[0018] The dynamic model of the direct-drive XY motion platform is represented as follows:

[0019]

[0020] In the formula, q = [q x ,q y ] T This represents the actual position of the mover of the linear motor in the direct-drive XY platform. These are the first and second derivatives of q, respectively; M = diag[m x ,m y [] represents the mass of the mover, and the subscripts x and y represent the X-axis motor and Y-axis motor, respectively. diag[·] represents a diagonal matrix; C = diag[c x ,c y [d] represents the coefficient of viscous friction; D = [d] x ,d y ] T The system's overall uncertainty dynamics include parameter variations, external disturbances, and frictional forces; F e =[F ex ,F ey ] T The electromagnetic thrust of the motor is represented as...

[0021] F e =K f i q (2)

[0022] In the formula, K f =diag[K fx ,K fy [i] represents the electromagnetic thrust coefficient; q =[i qx i qy ] T This is the q-axis current;

[0023] Combining equation (2), equation (1) can be rewritten as follows:

[0024]

[0025] In the formula, u=[u x ,u y ] T This is the system's main control input;

[0026] The reference adjustment contour error model specifically uses Ω as a fixed coordinate system, with its horizontal and vertical axes being X and Y, respectively, representing the two feed drive axes of the direct-drive XY platform. In this coordinate system, curve c represents the desired contour curve of the machined part point driven by the feed axes; r = [r x ,r y ] T Let q be the desired position of the linear motor mover in the direct-drive XY platform at time t in the Ω coordinate system; q = [q x ,q y ] T This indicates the actual position of the mover of the linear motor in the direct-drive XY platform; e c The contour error, i.e., the distance between q and c, is calculated by subtracting the actual positions of the two permanent magnet linear synchronous motors detected in step 2 from their expected positions, yielding the single-axis position tracking error e. t for

[0027] e t =qr=[e tx ,e ty ] T (4)

[0028] According to e t Find e c Establish a local coordinate system Ω p Its axis p1 is tangent to r at c, and its axis p2 is perpendicular to p1. Through coordinate transformation, e in the Ω coordinate system... t Convert to Ω p In coordinate system, we get

[0029] ep =[e px ,e py ] T =Λ T e t (5)

[0030]

[0031] In the formula, θ represents Ω and Ω p The angle of inclination between; e p Ω p Single-axis position tracking error in the coordinate system; Λ is the direction matrix.

[0032] Establish coordinate system Ω a Its coordinate axes are a1 and a2, and its origin is r. a Ω is the position on the desired contour curve c that is closest to point q. a The tilt angle relative to Ω is θ a Assuming along position r and position r a If the required speed for the trajectory between these points is almost constant, then the time t required to traverse this segment is... g Estimated as

[0033]

[0034] According to equation (7), r is obtained. a and θ a The estimated values ​​are respectively

[0035]

[0036] In the formula, For r a The estimated value; For θ a The estimated value.

[0037] According to equation (8), the corrected desired position r is obtained. n Represented as

[0038]

[0039]

[0040] In the formula, The transformation matrix; For in Ω a The approximation of the rotation matrix at that point is obtained by... Substituting into equations (5) and (6) to obtain r n Find the first and second derivatives, respectively.

[0041]

[0042]

[0043] Similar to equation (4), we obtain the corrected tracking error e under Ω. tn for

[0044] e tn =qr n (13)

[0045] Through coordinate transformation, e in the Ω coordinate system tn Convert to Ω n In coordinate system, we get

[0046]

[0047] Based on equation (13), find the second derivative of equation (14) and apply the property of rotation matrices. and have to

[0048]

[0049] At this point, the equivalent contour error e is used. ny Replace contour error e c The design of the contour error model was completed with reference to the model.

[0050] Step 3.2: Calculate the equivalent profile error e based on Step 3.1. ny The system executes a control algorithm based on an adaptive nonlinear sliding mode profile controller and an uncertainty compensator, specifically including three parts: the overall control law design of the direct drive XY motion platform servo system, the design of the adaptive nonlinear sliding mode profile controller, and the design of the uncertainty compensator.

[0051] 1) Design of the overall control law for the direct-drive XY motion platform servo system

[0052] Design an adaptive nonlinear sliding mode profile control method and an uncertainty compensator control method;

[0053] First, according to equation (3), neglecting the total uncertainty dynamics D of the system, we get

[0054]

[0055] In the formula, The control input for adaptive nonlinear sliding mode profile control is applied to the linear reference model of the system, resulting in the output position of the linear reference model as follows:

[0056] Secondly, considering that the actual system model contains total uncertainty dynamics D, an uncertainty compensator is designed to compensate for the influence of the system. The control input of the uncertainty compensator is υ = [υ x ,υ y ] T Therefore, the overall control law of the direct-drive XY motion platform servo system is:

[0057]

[0058] In the formula, u is the overall system control law, which is also the current control signal;

[0059] 2) Design of an adaptive nonlinear sliding mode profile controller;

[0060] The nonlinear sliding surface is selected as

[0061]

[0062] Ξ=diag(λ j +ψ j γ j (19)

[0063] In the formula, Ξ is the sliding surface; λ is a positive definite matrix; j The linear gain of the sliding surface is given by γ, where the subscript j indicates the X-axis or Y-axis. j ψ is a symmetric positive definite matrix used to adjust the final damping ratio. j To the contour error e n The relevant nonnegative differentiable nonlinear function has an upper bound of ψ. j ≤ψ jmax Designed for

[0064]

[0065]

[0066] In the formula, β j , and e jmax These are the positive tuning parameters, β j and Used to adjust ψ j The final damping ratio and rate of change amplitude; sgn(e nj ) represents the error signal e nj The sign function, when the system state point reaches the sliding surface, has According to equation (18), we get

[0067]

[0068] To prove the stability of the control system, the Lyapounov function is chosen as...

[0069]

[0070] Substituting equation (22) into equation (23) and taking the derivative, we get

[0071]

[0072] Since Ξ is a positive definite matrix, the system is asymptotically stable.

[0073] Based on the sliding surface designed by equations (18)-(21), the system dynamic equation shown in equation (16), and equation (15), the control law of the adaptive nonlinear sliding profile controller is designed as follows:

[0074]

[0075]

[0076] In the formula, To achieve adaptive gain, an adaptive law estimation is designed. Represented as

[0077]

[0078] In the formula, ε j , ζ j and ξ j It is a positive number.

[0079] 3) Uncertainty Compensator Design

[0080] In a fixed coordinate system Ω, the model uncertainty is defined as follows:

[0081]

[0082] In the formula, κ t =[κ tx ,κ ty ] T The actual position q and the position under the linear model The difference between them is the same as in equation (14), and κ is... t Transform from Ω coordinate system to Ω n In coordinate system, we get

[0083]

[0084] In the formula, κ n =[κ nx ,κ ny ] T When the desired position r is corrected nWhen the desired position r is exactly reached, the model uncertainty κ is corrected. tn =κ t Assume κ n If it is a second-order nonlinear dynamic, then it is expressed as:

[0085]

[0086] In the formula, υ=[υ x ,υ y ] T σ is the control input signal for the uncertainty compensator. j For unknown dynamics of the system, and |σ j |≤σ jmax , σ jmax It is its maximum value.

[0087] The tracking error of model uncertainty is defined as

[0088]

[0089] In the formula, and In Ω and Ω respectively n Tracking error due to uncertainties in the coordinate system; κ rtn =[κ rtnx ,κ rtny ] T The expected value is subject to uncertainty;

[0090] To eliminate the impact of uncertainties on the system, a linear sliding mode control method is used for dynamic compensation, and the sliding surface s is designed as follows:

[0091]

[0092] In the formula, α j =diag[α x ,α y [ is a diagonal matrix with constants.] Taking the derivative of equation (31) yields...

[0093]

[0094] In the formula,

[0095] Define the Lyapounov function V s for

[0096]

[0097] When s = 0, the control law of the uncertainty compensator is obtained as follows:

[0098]

[0099] In the formula, μ j =diag[μ x ,μ y ] is a diagonal matrix with positive constants.

[0100] Step 3.4: The total control law of the direct drive XY motion platform servo system output by equations (17), (25) and (34) in step 3.3 is u, which is the current control signal;

[0101] Step 4: The DSP processor generates six corresponding PWM pulse signals to drive the direct-drive XY motion platform.

[0102] The beneficial effects of adopting the above technical solution are as follows:

[0103] This invention provides an apparatus and method for improving the contour tracking accuracy of a direct-drive XY motion platform servo system. The reference adjustment contour error model can estimate a more accurate contour error, suitable for complex contour reference trajectories. The adaptive nonlinear sliding mode contour controller uses a nonlinear sliding surface, which improves the system's dynamic response speed and contour tracking accuracy. The introduction of an uncertainty compensator reduces the difference between the reference model and the actual model, compensating for the impact of uncertainty on the direct-drive XY motion platform servo system, thereby further improving the system's robustness. Using the above method, the direct-drive XY motion platform servo system can achieve high precision and strong robustness, which is an effective method for improving contour tracking accuracy and has certain engineering value. Attached Figure Description

[0104] Figure 1 A structural diagram of the direct-drive XY motion platform servo control system provided in an embodiment of the present invention;

[0105] Figure 2 A schematic diagram of the main circuit of a permanent magnet linear synchronous motor provided in an embodiment of the present invention;

[0106] Figure 3 This is a schematic diagram of the peripheral circuit connection of the DSP processor provided in an embodiment of the present invention;

[0107] Figure 4 A circuit schematic diagram of a DSP power supply level conversion circuit provided in an embodiment of the present invention;

[0108] Figure 5 A circuit schematic diagram of the Fault signal acquisition circuit provided in an embodiment of the present invention;

[0109] Figure 6 The circuit schematic diagram of the DSP crystal oscillator circuit provided in the embodiment of the present invention;

[0110] Figure 7The circuit schematic diagram of the JTAG circuit provided in the embodiments of the present invention;

[0111] Figure 8 The circuit schematic diagram of the DSP reset circuit provided in the embodiment of the present invention;

[0112] Figure 9 The circuit schematic diagram of the IPM protection isolation drive circuit provided in the embodiment of the present invention;

[0113] Figure 10 The circuit diagram of the current detection circuit provided in the embodiment of the present invention;

[0114] Figure 11 A circuit diagram of the position and velocity detection circuit provided in an embodiment of the present invention;

[0115] Figure 12 A schematic diagram illustrating the tracking error and contour error of a direct-drive XY motion platform servo system provided in an embodiment of the present invention;

[0116] Figure 13 This is a schematic diagram of an algorithm for improving the contour tracking accuracy of a direct-drive XY motion platform servo system, provided in an embodiment of the present invention.

[0117] Figure 14 The figure shows the contour error curve of the direct-drive XY motion platform servo system based on an adaptive nonlinear sliding mode contour controller under the desired trajectory of an ellipse at low speed, provided in an embodiment of the present invention.

[0118] Figure 15 The contour error curve of the direct-drive XY motion platform servo system based on an adaptive nonlinear sliding mode contour controller and an uncertainty compensator under low-speed tracking of the desired elliptical trajectory is provided in the embodiments of the present invention.

[0119] Figure 16 The contour error curve of the direct-drive XY motion platform servo system based on an adaptive nonlinear sliding mode contour controller under high-speed tracking of the desired elliptical trajectory is provided in an embodiment of the present invention.

[0120] Figure 17 The contour error curve of the direct-drive XY motion platform servo system based on an adaptive nonlinear sliding mode contour controller and an uncertainty compensator under high-speed tracking of the desired elliptical trajectory is provided in the embodiments of the present invention.

[0121] Figure 18 The contour error curve of the direct-drive XY motion platform servo system based on an adaptive nonlinear sliding mode contour controller under the desired four-leaf clover trajectory provided in the embodiment of the present invention;

[0122] Figure 19The diagram shows the contour error curve of the direct-drive XY motion platform servo system based on an adaptive nonlinear sliding mode contour controller and an uncertainty compensator under the desired trajectory of a four-leaf clover ellipse, as provided in this embodiment of the invention. Detailed Implementation

[0123] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0124] On the one hand, a device for improving the contour tracking accuracy of a direct-drive XY motion platform servo system, such as... Figure 1 As shown, the device realizes contour control of the direct-drive XY motion platform servo system based on an adaptive nonlinear sliding mode controller and an uncertainty compensator. It includes a rectifier filter circuit, an IPM inverter circuit, a detection circuit, a DSP processor, an IPM isolation protection drive circuit, a host computer, and a direct-drive XY motion platform.

[0125] The detection circuit includes a current detection circuit, a Hall sensor, a position and speed detection circuit, and a linear encoder. The input of the current detection circuit is connected to the output of the IPM inverter circuit via the Hall sensor, and the output of the current detection circuit is connected to one signal input of the DSP processor. The Hall sensor acquires the current of the permanent magnet linear synchronous motor's rotor and converts the acquired analog current into a digital quantity recognizable by the DSP processor. The input of the position and speed detection circuit is connected to the output of the permanent magnet linear synchronous motor via the linear encoder, and the output of the position and speed detection circuit is connected to another signal input of the DSP processor. The linear encoder acquires the position and speed signals of the permanent magnet linear synchronous motor's rotor and converts the acquired analog position and speed signals into digital quantities recognizable by the DSP processor.

[0126] The main circuit schematic of the permanent magnet linear synchronous motor is as follows: Figure 2 As shown, the power supply section consists of a rectifier circuit and an IPM inverter circuit. The rectifier circuit serves as the input to the entire control device, receiving the signal indicating the final position of the permanent magnet linear synchronous motor as given by the user. The input of the rectifier circuit is connected to a three-phase AC power supply, converting the changing AC power into stable DC power. Its output is connected to the IPM inverter circuit. The IPM inverter circuit converts the DC power output from the rectifier circuit back into AC power, and its output is connected to the permanent magnet linear synchronous motor, supplying power to the motor.

[0127] In the rectifier circuit, the anode of the rectifier bridge is connected to the N terminal of the IPM inverter circuit, and its cathode is connected to the P terminal of the IPM inverter circuit. The three-phase current output by the IPM inverter circuit is connected to the permanent magnet synchronous linear motor through the output terminals U, V, and W. P and N are the input terminals of the IPM inverter circuit after rectification, smoothing, and filtering by the frequency converter; P is the positive terminal, and N is the negative terminal. The rectifier unit adopts a bridge uncontrolled rectification method with large capacitor filtering, which can obtain a constant voltage suitable for IPM operation.

[0128] In this embodiment, the motor's start and stop are controlled by normally open contact switch A and normally closed contact switch B, respectively. During circuit operation, the three-phase AC power is converted from 220V to a three-phase AC power with an effective value approximately equal to the input voltage of the IPM inverter circuit via a transformer. This is then passed through a rectifier bridge transistor circuit to obtain a pulsating DC voltage. Next, the DC voltage is smoothed by capacitor filtering, and a stable voltage is applied across the PN terminals of the IPM inverter circuit. The converted DC power is then inverted into frequency-converted three-phase AC power by the IPM inverter circuit, thereby driving the permanent magnet linear synchronous motor. The IGBTs in the IPM inverter circuit are controlled by a PWM pulse sequence output from the control circuit to ensure that the required amplitude and phase of the three-phase AC power are achieved.

[0129] The DSP processor includes a DSP processor chip and its peripheral circuits. It calculates the difference between the desired position signal and the X-axis and Y-axis position signals of the permanent magnet linear synchronous motors detected by the grating ruler, thereby obtaining the X-axis and Y-axis position tracking errors of the permanent magnet linear synchronous motors. Then, it calculates the contour error of the direct-drive XY motion platform using a reference adjustment contour error estimation method, and uses this as the input to an adaptive nonlinear sliding mode contour controller. The adaptive nonlinear sliding mode contour control algorithm improves the contour machining accuracy of the system. The control law of the system is derived using the Lyapounov function. An uncertainty compensator is designed to overcome the effects of uncertainties such as parameter changes, external disturbances, and nonlinear friction in the system, thus obtaining the overall control law based on adaptive nonlinear sliding mode contour control and the uncertainty compensator. The current control signal is calculated, and the current control signal generates a PWM signal via the DSP processor to servo drive the two permanent magnet linear synchronous motors. The PWM port of the DSP processor is connected to another input terminal of the IPM inverter circuit through the IPM isolation protection drive circuit. The IPM isolation drive protection circuit is mainly used to electrically isolate the IPM inverter circuit from external circuits, i.e., opto-isolate, and drive the six IGBTs in the IPM inverter circuit.

[0130] In this embodiment, the DSP model selected is TMS320F28335, and its peripheral circuit connection structure schematic diagram is as follows. Figure 3As shown. The peripheral circuitry of the DSP processor includes level conversion circuitry, such as... Figure 4 As shown, the Fault signal acquisition circuit, such as Figure 5 As shown, the DSP crystal oscillator circuit is as follows: Figure 6 As shown, the JTAG circuit is as follows: Figure 7 As shown, the DSP reset circuit is as follows: Figure 8 As shown, the IPM isolation drive protection circuit, such as Figure 9 As shown, the current detection circuit is as follows: Figure 10 The position and velocity detection circuit shown is as follows: Figure 11 As shown. The level conversion circuit converts the 5V power supply voltage to the 3.3V operating voltage for the DSP processor. The fault signal acquisition circuit is connected to the external interrupt pin of the DSP processor, and the DSP processor's interrupt program handles the fault. The DSP crystal oscillator circuit provides the DSP processor with a 30MHz operating frequency. Pins 1 and 4 of the crystal oscillator circuit are connected to the DSP's X1 (pin 104) and X2 (pin 102) interfaces, respectively. The JTAG circuit is used to test the chip's electrical characteristics and detect whether there are any problems with the chip. Pins 1, 2, 3, 7, 9, 11, 13, and 14 of the JTAG interface circuit are connected to the DSP's pins 79, 78, 76, 77, 87, 87, 85, and 86, respectively. The reset circuit is used to restore the entire circuit to its initial state. Pin 1 of the reset circuit is connected to pin 80 of the DSP.

[0131] The direct-drive XY motion platform consists of a marble base, two permanent magnet linear synchronous motors, a linear motor mounting bed, a motor mounting bracket, a mover worktable, linear guides, and a grating detection device. The two permanent magnet linear synchronous motors are mounted on the linear motor mounting bed in an XY orthogonal configuration via the motor mounting bracket. The lower motor is the X-axis motor, and the upper motor is the Y-axis motor. The stators of the permanent magnet linear synchronous motors alternately mount N-pole and S-pole permanent magnets, while the armature windings are mounted on the movers. The linear motor mounting bed, made of cast iron, is fixed to the marble base and has a smooth, flat mounting surface. Height and balance shims are installed under the linear motor mounting bed to ensure motor accuracy. The motor mounting bracket is made of aluminum alloy, and the grating detection device is attached to its surface. The reading head of the grating detection device is bolted to the movers of the X-axis and Y-axis motors for detecting motor speed and position. The Y-axis motor is mounted on the moving platform of the X-axis motor, and the moving platform is connected to the moving coil of the Y-axis, thereby realizing the movement of the XY motion platform. The moving coils of the X-axis motor and the Y-axis motor are both supported by the linear guide rails, and both axes adopt a double rolling guide rail design.

[0132] The host computer uses a control program written in C language and Code Composer Studio 6.1.3 software, which is stored in the host computer. The control program processes the data information collected by the current, position, and speed detection circuits, then calculates the difference between the collected data and the expected command signal, and inputs it into the reference adjustment contour error model. It then calculates the contour error as the input variable of the adaptive nonlinear sliding mode contour controller, executes the adaptive nonlinear sliding mode contour control algorithm, designs an uncertainty compensator, and finally downloads the core algorithm based on the adaptive nonlinear sliding mode contour control and uncertainty compensator as a C language program to the DSP processor via the SCI serial port bus. This drives the two permanent magnet linear synchronous motors in the direct drive XY motion platform servo system.

[0133] In this embodiment, the IPM isolation drive protection circuit, such as Figure 9 As shown, this is used for opto-isolation and to drive the six IGBTs in the IPM inverter circuit. The IPM protection and isolation drive circuit replaces the power devices as the power supply. After being processed by the IPM, the current is fed into the permanent magnet linear synchronous motor, enabling the motor to move.

[0134] Current detection circuit, such as Figure 10 As shown, its input terminal is connected to the output terminal of the IPM inverter circuit via a Hall sensor, and the output terminal of the current detection circuit is connected to the ADC port of the DSP processor. This is used to acquire the mover current of the permanent magnet linear synchronous motor via the Hall sensor and convert the acquired analog current into a digital quantity that the DSP processor can recognize. Since the system in this embodiment is a three-phase balanced system, i.e., the vector sum of the three-phase currents is zero, it is only necessary to detect the current of two phases to calculate the three-phase current. This embodiment uses an LTS25-NP type sensor to detect the current.

[0135] Position and velocity detection circuit, such as Figure 11 As shown, the input of the position and speed detection circuit is connected to the output of the permanent magnet linear synchronous motor via a grating ruler. The output is connected to the EQEP port of the DSP processor. This circuit is used to acquire the position and speed signals of the permanent magnet linear synchronous motor's mover via the grating ruler and convert them into digital quantities that the DSP processor can recognize. The position and speed detection circuit sends two orthogonal square wave pulse signals A and B to the two capture units EQEP1 (pin 90) and EQEP2 (pin 91) of the DSP processor via a high-speed optocoupler LTV-341W. The capture units inside the DSP processor can be defined by software as orthogonal encoded pulse input units. The pulses can then be counted, and the direction, position, and speed of the permanent magnet linear synchronous motor can be determined based on the pulse sequence.

[0136] The control program, written in C language, was written using Code Composer Studio 6.1.3 software and stored on the host computer. The control program first processes the data collected by the detection circuit, then inputs the difference between the collected data and the reference command signal into the reference adjustment contour error model to obtain the contour error, which is then used as the input for adaptive nonlinear sliding mode contour control. An uncertainty compensator is designed, and finally, the C language program, which is based on the adaptive nonlinear sliding mode contour control algorithm of the uncertainty compensator, is downloaded to the DSP processor via the SCI serial port bus and run to drive the direct drive XY motion platform servo system.

[0137] On the other hand, a method for improving the contour tracking accuracy of a direct-drive XY motion platform servo system is implemented based on the aforementioned apparatus and method for improving the contour tracking accuracy of a direct-drive XY motion platform servo system, such as... Figure 13 As shown, the specific steps include:

[0138] Step 1: Input the desired position signals of the X-axis motor and Y-axis motor in the direct drive XY motion platform. The two permanent magnet linear synchronous motors receive the desired position and start moving.

[0139] Step 2: Collect the actual position, speed, and current of the movers of the two permanent magnet linear synchronous motors, specifically:

[0140] After the two motors in the direct-drive XY motion platform are running, the current of the mover is collected by the Hall sensor; the linear grating ruler outputs two-phase orthogonal square wave pulse signals and zero-position pulse signals through the position and speed detection circuit, for a total of three pulse signals; the pulse signals are sent to the orthogonal encoding pulse input unit EQEP of the DSP processor chip, and the encoder resolution is improved by four-fold frequency multiplication. At the same time, the general-purpose timer is set to directional increment / decrement counting mode. The position offset of the mover is obtained from the number of pulses of the two-phase orthogonal square wave pulse signals, and the direction of rotation of the mover is obtained from the lead relationship of the two-phase pulses, thus obtaining the actual position and speed of the mover.

[0141] Step 3: Using the actual positions of the two permanent magnet linear synchronous motors acquired in Step 2, the single-axis position tracking error is first calculated in the DSP. Then, the equivalent contour error is calculated by referencing the contour error model. Figure 12 As shown, the input is then fed into an adaptive nonlinear sliding mode profile controller to reduce the profile error. An uncertainty compensator is designed to compensate for external disturbances, parameter changes, and nonlinear friction forces of the system. Based on the influence of uncertainty factors on the system, the overall control law based on adaptive nonlinear sliding mode profile control and uncertainty compensator, i.e., the current control signal, is finally calculated. The specific steps are as follows:

[0142] Step 3.1: Establish a servo system model for the direct-drive XY motion platform, including the dynamic model of the direct-drive XY motion platform and the reference adjustment profile error model;

[0143] The dynamic model of the direct-drive XY motion platform is represented as follows:

[0144]

[0145] In the formula, q = [q x ,q y ] T This represents the actual position of the mover of the linear motor in the direct-drive XY platform. These are the first and second derivatives of q, respectively; M = diag[m x ,m y [] represents the mass of the mover, and the subscripts x and y represent the X-axis motor and Y-axis motor, respectively. diag[·] represents a diagonal matrix; C = diag[c x ,c y [d] represents the coefficient of viscous friction; D = [d] x ,d y ] T The system's overall uncertainty dynamics include parameter variations, external disturbances, and frictional forces; F e =[F ex ,F ey ] T The electromagnetic thrust of the motor is represented as...

[0146] F e =K f i q (2)

[0147] In the formula, K f =diag[K fx ,K fy [i] represents the electromagnetic thrust coefficient; q =[i qx i qy ] T This is the q-axis current;

[0148] Combining equation (2), equation (1) can be rewritten as follows:

[0149]

[0150] In the formula, u=[u x ,u y ] T This is the system's main control input;

[0151] The reference adjustment contour error model is specifically defined as follows: In the machining application of a direct-drive XY motion platform, since the machining quality of the workpiece is closely related to the magnitude of the contour error, the inter-axis contour error is more important than the single-axis tracking error. Contour error refers to the shortest distance between the actual position and the desired contour. However, when the desired contour is complex, it is difficult to directly obtain the real-time contour error value. Therefore, the equivalent contour error can be calculated based on the tracking error. Ω is selected as a fixed coordinate system, with its horizontal and vertical axes being X and Y, respectively, representing the two feed drive axes of the direct-drive XY platform. In this coordinate system, curve c represents the desired contour curve of the machining part point driven by the feed axis; r = [r x ,r y ] T Let q be the desired position of the linear motor mover in the direct-drive XY platform at time t in the Ω coordinate system; q = [q x ,q y ] T This indicates the actual position of the mover of the linear motor in the direct-drive XY platform; e c The contour error, i.e., the distance between q and c, is calculated by subtracting the actual positions of the two permanent magnet linear synchronous motors detected in step 2 from their expected positions, yielding the single-axis position tracking error e. t for

[0152] e t =qr=[e tx ,e ty ] T (4)

[0153] According to e t Find e c Establish a local coordinate system Ω p Its axis p1 is tangent to r at c, and its axis p2 is perpendicular to p1. Through coordinate transformation, e in the Ω coordinate system... t Convert to Ω p In coordinate system, we get

[0154] e p =[e px ,e py ] T =Λ T e t (5)

[0155]

[0156] In the formula, θ represents Ω and Ω p The angle of inclination between; e p Ω p Single-axis position tracking error in the coordinate system; Λ is the direction matrix.

[0157] Establish coordinate system Ωa Its coordinate axes are a1 and a2, and its origin is r. a Ω is the position on the desired contour curve c that is closest to point q. a The tilt angle relative to Ω is θ a Assuming along position r and position r a If the required speed for the trajectory between these points is almost constant, then the time t required to traverse this segment is... g Estimated as

[0158]

[0159] According to equation (7), r is obtained. a and θ a The estimated values ​​are respectively

[0160]

[0161] In the formula, For r a The estimated value; For θ a The estimated value.

[0162] According to equation (8), the corrected desired position r is obtained. n Represented as

[0163]

[0164]

[0165] In the formula, The transformation matrix; For in Ω a The approximation of the rotation matrix at that point is obtained by... Substituting into equations (5) and (6) to obtain r n Find the first and second derivatives, respectively.

[0166]

[0167]

[0168] Similar to equation (4), we obtain the corrected tracking error e under Ω. tn for

[0169] e tn =qr n (13)

[0170] Through coordinate transformation, e in the Ω coordinate system tn Convert to Ω n In coordinate system, we get

[0171]

[0172] Based on equation (13), find the second derivative of equation (14) and apply the property of rotation matrices. and have to

[0173]

[0174] At this point, the equivalent contour error e is used. ny Replace contour error e c The design of the contour error model was completed with reference to the model.

[0175] Step 3.2: Calculate the equivalent profile error e based on Step 3.1. ny The system executes a control algorithm based on an adaptive nonlinear sliding mode profile controller and an uncertainty compensator, specifically including three parts: the overall control law design of the direct drive XY motion platform servo system, the design of the adaptive nonlinear sliding mode profile controller, and the design of the uncertainty compensator.

[0176] 1) Design of the overall control law for the direct-drive XY motion platform servo system

[0177] Since the direct-drive XY platform servo system is affected by nonlinear dynamics during operation, an adaptive nonlinear sliding mode profile control method and an uncertainty compensator control method are designed for the linear reference model and the nonlinear dynamics part, respectively, when designing the controller.

[0178] First, according to equation (3), neglecting the total uncertainty dynamics D of the system, we can obtain

[0179]

[0180] In the formula, As the control input for adaptive nonlinear sliding mode profile control, applied to the linear reference model of the system, the output position of the linear reference model can be obtained as follows:

[0181] Secondly, considering that the actual system model contains total uncertainty dynamics D, an uncertainty compensator is designed to compensate for the influence of the system. The control input of the uncertainty compensator is υ = [υ x ,υ y ] T Therefore, the overall control law of the direct-drive XY motion platform servo system is:

[0182]

[0183] In the formula, u is the overall system control law, which is also the current control signal;

[0184] 2) Design of an adaptive nonlinear sliding mode profile controller;

[0185] When designing a sliding mode profile controller, it is necessary to design a suitable sliding surface and select a control law so that the system state points can quickly converge to the sliding surface. Traditional sliding surface design typically uses a linear sliding surface, but this method cannot simultaneously guarantee the fast response and small overshoot of the control system. Therefore, in the design of an adaptive nonlinear sliding mode profile controller, a nonlinear sliding surface is selected.

[0186]

[0187] Ξ=diag(λ j +ψ j γ j (19)

[0188] In the formula, Ξ is the sliding surface; λ is a positive definite matrix; j The linear gain of the sliding surface is given by γ, where the subscript j indicates the X-axis or Y-axis. j ψ is a symmetric positive definite matrix used to adjust the final damping ratio. j To the contour error e n The relevant nonnegative differentiable nonlinear function has an upper bound of ψ. j ≤ψ jmax Designed for

[0189]

[0190]

[0191] In the formula, β j , and e jmax These are the positive tuning parameters, β j and Used to adjust ψ j The final damping ratio and rate of change amplitude; sgn(e nj ) represents the error signal e nj The sign function, when the system state point reaches the sliding surface, has According to equation (18), we get

[0192]

[0193] To prove the stability of the control system, the Lyapounov function is chosen as...

[0194]

[0195] Substituting equation (22) into equation (23) and taking the derivative, we get

[0196]

[0197] Since Ξ is a positive definite matrix, the system is asymptotically stable.

[0198] Based on the sliding surface designed by equations (18)-(21), the system dynamic equation shown in equation (16), and equation (15), the control law of the adaptive nonlinear sliding profile controller is designed as follows:

[0199]

[0200]

[0201] In the formula, To achieve adaptive gain, an adaptive law estimation is designed. Represented as

[0202]

[0203] In the formula, ε j , ζ j and ξ j It is a positive number.

[0204] 3) Uncertainty Compensator Design

[0205] Because a linear reference model of the system is used in the design of the adaptive nonlinear sliding mode contour controller, the actual object differs from the reference object model. That is, the total uncertainty dynamics D in equation (3) still exists. Therefore, an uncertainty compensator is designed to compensate for D, so as to further reduce the contour tracking error of the system. Under the fixed coordinate system Ω, the model uncertainty is defined as:

[0206]

[0207] In the formula, κ t =[κ tx ,κ ty ] T The actual position q and the position under the linear model The difference between them is the same as in equation (14), and κ is... t Transform from Ω coordinate system to Ω n In coordinate system, we get

[0208]

[0209] In the formula, κ n =[κ nx ,κ ny ] T When the desired position r is corrected n When the desired position r is exactly reached, the model uncertainty κ is corrected.tn =κ t Assume κ n If it is a second-order nonlinear dynamic, then it is expressed as:

[0210]

[0211] In the formula, υ=[υ x ,υ y ] T σ is the control input signal for the uncertainty compensator. j For unknown dynamics of the system, and |σ j |≤σ jmax , σ jmax It is its maximum value.

[0212] The tracking error of model uncertainty is defined as

[0213]

[0214] In the formula, and In Ω and Ω respectively n Tracking error due to uncertainties in the coordinate system; κ rtn =[κ rtnx ,κ rtny ] T The expected value is subject to uncertainty;

[0215] To eliminate the impact of uncertainties on the system, a linear sliding mode control method is used for dynamic compensation, and the sliding surface s is designed as follows:

[0216]

[0217] In the formula, α j =diag[α x ,α y [ is a diagonal matrix with constants.] Taking the derivative of equation (31) yields...

[0218]

[0219] In the formula,

[0220] Define the Lyapounov function V s for

[0221]

[0222] When s = 0, the control law of the uncertainty compensator is obtained as follows:

[0223]

[0224] In the formula, μ j=diag[μ x ,μ y ] is a diagonal matrix with positive constants.

[0225] Step 3.4: The total control law of the direct drive XY motion platform servo system output by equations (17), (25) and (34) in step 3.3 is u, which is the current control signal;

[0226] Step 4: The DSP processor generates six corresponding PWM pulse signals to drive the direct-drive XY motion platform.

[0227] The PWM signal output by the DSP processor is converted into a drive signal by the IPM protection isolation drive circuit. The fixed 220V three-phase AC power is rectified into stable DC power and sent to the IPM inverter circuit. The IPM inverter circuit controls the conduction and cutoff of the six IGBTs in the IPM inverter circuit according to the six PWM pulse signals generated by the DSP processor, so as to obtain the required three-phase AC power to drive the movers of the two permanent magnet linear synchronous motors in the direct drive XY motion platform.

[0228] In this embodiment, to verify the effectiveness of the above algorithm, the parameters of the direct-drive XY motion platform are selected as follows: X-axis motor rated thrust F exn =60N, mover mass m x =2kg, thrust coefficient K fx =24N / A, pole moment τ x =2mm, viscous friction coefficient c x =244 N·s / m, rated thrust F of Y-axis motor eyn =90N, mover mass m y =2kg, thrust coefficient K fy =35N / A, pole distance τ y =2mm, viscous friction coefficient c y = 82 N·s / m. Simulation was performed using Matlab / Simulink.

[0229] Based on the parameters of the direct-drive XY motion platform described above, and the adaptive nonlinear sliding mode profile control method based on an uncertainty compensator designed in this invention, after repeated debugging, the final selected control algorithm parameters are: λ in the nonlinear sliding surface j =200, γ j =2.5, β j =6; The adaptive law is chosen as ε j =0.1, ζ j =0.01、ξ j =0.01; the uncertainty compensator parameter is selected as α. j =0.35, μj =0.01.

[0230] The direct-drive XY platform was commanded to track a desired elliptical trajectory at low speed, and experiments were conducted under no-load conditions. The X-axis input was a sine signal with an amplitude of 20 mm and a period of 4 s, and the Y-axis input was a cosine signal with an amplitude of 15 mm and a period of 4 s. Under the condition of tracking the elliptical contour curve at low speed, an adaptive nonlinear sliding mode contour controller was used, and the contour tracking curve of the direct-drive XY motion platform based on adaptive nonlinear sliding mode contour control and uncertainty compensator proposed in this invention is as follows: Figure 14 and Figure 15 As shown.

[0231] To verify the contour tracking performance of the direct-drive XY motion platform under high-speed motion conditions, a sine signal with an amplitude of 80 mm and a period of 1 s was input to the X-axis, and a cosine signal with an amplitude of 50 mm and a period of 1 s was input to the Y-axis. Under high-speed tracking of elliptical contour curves, an adaptive nonlinear sliding mode contour controller was used, and the contour tracking curves of the direct-drive XY motion platform based on adaptive nonlinear sliding mode contour control and uncertainty compensator proposed in this invention are shown below. Figure 16 and Figure 17 As shown, comparing the contour tracking curves under low-speed and high-speed motion reveals that the contour tracking performance of both methods decreases, but they can still track the desired trajectory relatively well. The contour error of the adaptive nonlinear sliding mode contour control system is approximately -7.8 to 7.2 μm, while after introducing the uncertainty compensator, the system's contour error is approximately ±2 μm. This indicates that the uncertainty compensator can effectively compensate for uncertainties such as parameter changes, external disturbances, and friction, thus improving the system's contour tracking accuracy.

[0232] The direct-drive XY platform was commanded to track the desired trajectory of a four-leaf clover with high curvature, and a 1kg load was dragged during the experiment. The contour tracking curves of the direct-drive XY motion platform based on adaptive nonlinear sliding mode contour control and uncertainty compensator proposed in this invention are shown below. Figure 18 and Figure 19 As shown in the two figures, the contour tracking error of the direct-drive XY motion platform servo system using an adaptive nonlinear sliding mode contour controller is approximately -3.9 to 3.8 μm. However, after introducing the uncertainty compensator, the contour error of the system is reduced to -2.7 to 2.9 μm. This indicates that the method based on the adaptive nonlinear sliding mode contour controller and the uncertainty compensator is very effective in improving the robustness and contour tracking accuracy of the direct-drive XY motion platform.

[0233] The above description is merely a preferred embodiment of this disclosure and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in the embodiments of this disclosure is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in the embodiments of this disclosure.

Claims

1. A method for improving contour accuracy of a direct-drive XY motion platform servo system, characterized in that, The method comprises the following steps: Step 1: inputting desired position signals of X-axis motor and Y-axis motor in a direct-drive XY motion platform, and the two permanent magnet linear synchronous motors start to move after receiving the desired position signals; Step 2: collecting actual positions, speeds and currents of the two permanent magnet linear synchronous motor movers, specifically as follows: After the two motors in the direct-drive XY motion platform run, the mover currents are collected by using a Hall sensor; three pulse signals, including two-phase quadrature square wave pulse signals and a zero position pulse signal, are output by a linear grating ruler through a position and speed detection circuit; The pulse signals are sent to an orthogonal encoding pulse input unit EQEP of a DSP processor chip, the resolution of the encoder is improved through four times frequency processing, and a general purpose timer is set to a directional increment and decrement counting mode, so that the position offset of the mover is obtained from the pulse number of the two-phase quadrature square wave pulse signals, the turning of the mover is obtained from the leading relationship of the two-phase pulse, and thus the actual position and speed of the mover are obtained; Step 3: using the actual positions of the two permanent magnet linear synchronous motor movers collected in step 2, the single-axis position tracking error is first calculated in the DSP, the equivalent contour error is calculated through a reference adjustment contour error model, and then the equivalent contour error is input into an adaptive nonlinear sliding mode contour controller to reduce the contour error, an uncertainty compensator is designed to compensate for external disturbances, parameter changes and nonlinear friction of the system, and finally the total control law based on the adaptive nonlinear sliding mode contour control and the uncertainty compensator is calculated, that is, the current control signal; Step 3.1: establishing a direct-drive XY motion platform servo system model, including a direct-drive XY motion platform dynamics model and a reference adjustment contour error model; The direct-drive XY motion platform dynamics model is expressed as: (1)； where, is the actual position of the mover of the linear motor in the direct-drive XY platform, , are the first and second derivatives of q, respectively; is the mass of the mover, and the subscripts x and y represent the X-axis motor and the Y-axis motor, respectively, denotes a diagonal matrix; is the viscous friction coefficient; is the total uncertainty dynamics of the system, including parameter variations, external disturbances, and friction forces; is the electromagnetic thrust of the motor, expressed as (2)； wherein is the electromagnetic thrust coefficient; is the q-axis current; Combined with formula (2), formula (1) is rewritten as (3)； In the formula, is the total system control input; The reference adjustment contour error model is specifically selected as is a fixed coordinate system, whose horizontal and vertical axes are X and Y, respectively, representing two feed driving shafts of the direct-drive XY platform. In this coordinate system, the curve represents the expected contour curve of a machined part point driven by the feed shaft; is the expected position of the mover of the linear motor in the direct-drive XY platform at time t in the coordinate system; represents the actual position of the mover of the linear motor in the direct-drive XY platform; is the contour error, i.e., the distance between and According to the actual positions of the movers of the two permanent magnet linear synchronous motors detected in step 2, the single-axis position tracking error is obtained by subtracting the expected position from the actual position. is (4)； For according to sought out , a local coordinate system whose axis is tangent to at , and axis is perpendicular to , through coordinate transformation, the coordinates under are converted to coordinates under, get (5)； (6)； wherein is and the tilt angle between is the single-axis position tracking error in the coordinate system; is the direction matrix; Establish coordinate system with coordinate axes and origin at is the desired contour curve the position closest to the point , with respect to is the angle of inclination Assuming that the speed required along the trajectory between position and position is almost constant, the time required to pass through this segment is estimated as (7)； From equation (7), the estimated values of and are respectively (8)； wherein is an estimate of is an estimate of is an estimate of is an estimate of According to equation (8), the modified desired position is obtained is represented as (9)； (10)； wherein is a transformation matrix; is an approximation of the rotation matrix at is obtained by substituting into equations (5) and (6), and the first and second derivatives are taken, respectively, to obtain (11)； (12)； As with equation (4), the modified tracking error is given by is (13)； By coordinate transformation, the coordinates in the coordinate system are converted to coordinates in the coordinate system, and (14)； According to equation (13), the second derivative of equation (14) is taken and the properties of the rotation matrix are applied and yields (15)； Up to now, the equivalent profile error Instead of the profile error , the reference adjustment profile error model is designed Step 3.2: Equivalent contour error calculated from step 3.1 The control algorithm based on the adaptive nonlinear sliding mode contour controller and the uncertainty compensator is executed, specifically including three parts of the total control law design of the direct-drive XY motion platform servo system, the adaptive nonlinear sliding mode contour controller design and the uncertainty compensator design. 1) Total control law design of the direct-drive XY motion platform servo system The adaptive nonlinear sliding mode contour control method and the uncertainty compensator control method are designed; First, according to equation (3), ignoring the total uncertainty dynamics of the system , we have (16)； In the formula, is the control input of the adaptive nonlinear sliding mode contour control, acting on the linear reference model of the system, and the output position of the linear reference model is ; Secondly, considering the total uncertain dynamics in the actual model of the system , an uncertainty compensator is designed to compensate the effect of the system, whose control input is Therefore, the total control law of the direct-drive XY motion platform servo system is (17)； In the formula, is the total control law of the system, and is also a current control signal; 2) Design of the adaptive nonlinear sliding mode contour controller The nonlinear sliding mode surface is selected as (18)； (19)； wherein is a sliding surface; is a positive definite matrix; is a linear gain of the sliding surface, the subscript j denotes the X-axis or the Y-axis; is a symmetric positive definite matrix, used to adjust the final damping ratio; is a non-negative differentiable nonlinear function related to the profile error , whose upper bound is is designed as (20)； (21)； wherein , and are positive tuning parameters, and are used to adjust the final damping ratio and the amplitude of the rate of change of respectively; is the sign function of the error signal and when the system state point reaches the sliding surface, there is then according to equation (18), we have (22)； In order to prove the stability of the control system, the Lyapounov function is selected as (23)； Formula (22) is substituted into formula (23) and the derivative is obtained as (24)； Because is positive definite, the system is asymptotically stable; Based on the sliding mode surface designed according to formula (18)-formula (21), the system dynamic equation shown in formula (16) and formula (15), the control law of the adaptive nonlinear sliding mode contour controller is ； (25)； wherein is the adaptive gain, the adaptive law is designed to estimate is expressed as (26)； wherein , , and are normal numbers; 3) Design of the uncertainty compensator In the fixed coordinate system Now, define the model uncertainty as （27）； where is the actual position is the position under the linear model is the difference between the two, same as equation (14), and is converted from to coordinate system, we have （28）； where When the modified desired position is exactly the desired position then there is no modified model uncertainty ; assuming second order nonlinear dynamics, this is expressed as （29）； wherein is a control input signal of the uncertainty compensator; is the system unknown dynamics, and , is the maximum value thereof; The tracking error of the model uncertainty is defined as （30）； wherein and are the tracking errors of the uncertainty in the coordinate system and are the tracking errors of the uncertainty in the coordinate system is the expected value of the uncertainty In order to eliminate the influence of the uncertainty on the system, the linear sliding mode control method is used for dynamic compensation, and the sliding mode surface s is designed as （31）； wherein is a normal diagonal matrix; and the derivative of equation (31) is （32）； In the formulae, ; Defining a Lyapounov function is （33）； In case the control law of the uncertainty compensator is obtained as （34）； wherein is a normal diagonal matrix; Step 3.3: The total control law of the direct-drive XY motion platform servo system output in step 3.2 is i.e. the current control signal; Step 4: the DSP processor generates corresponding six-way PWM pulse signals to drive the direct-drive XY motion platform to run.

2. The method of claim 1, which is implemented by a device for improving contour accuracy of a direct-drive XY motion platform servo system, characterized in that, The system comprises a rectification filter circuit, an IPM inverter circuit, a detection circuit, a DSP processor, an IPM isolation protection driving circuit, an upper computer and a direct-drive XY motion platform. The rectifier filter circuit and the IPM inverter circuit jointly constitute a power supply part, wherein an input end of the rectifier filter circuit is connected with a three-phase alternating current power supply, and an output end of the rectifier filter circuit is connected with one input end of the IPM inverter circuit; an output end of the IPM inverter circuit is connected with the permanent magnet linear synchronous motor and supplies power for the permanent magnet linear synchronous motor; The detection circuit comprises a current detection circuit, a Hall sensor, a position and speed detection circuit and a linear grating ruler; wherein an input end of the current detection circuit is connected with an output end of the IPM inverter circuit through the Hall sensor, and an output end of the current detection circuit is connected with one signal input end of the DSP processor; an input end of the position and speed detection circuit is connected with an output end of the permanent magnet linear synchronous motor through the linear grating ruler, and an output end of the position and speed detection circuit is connected with another signal input end of the DSP processor; The DSP processor is a DSP processor chip and its peripheral circuit, and a PWM port of the DSP processor is connected with another input end of the IPM inverter circuit through the IPM isolation protection driving circuit; The host computer processes the data information collected by the current, position and speed detection circuits through a control program, then makes difference between the collected data and an expected instruction signal, inputs the difference into a reference adjustment contour error model, calculates a contour error as an input variable of an adaptive nonlinear sliding mode contour controller, executes an adaptive nonlinear sliding mode contour control algorithm, designs an uncertainty compensator, and finally downloads the core algorithm based on the adaptive nonlinear sliding mode contour control and the uncertainty compensator into the DSP processor to run in the DSP processor through the SCI serial bus and the SCI serial pin of the DSP processor, so as to drive two permanent magnet linear synchronous motors in the direct-drive XY motion platform servo system to run.

3. The method of claim 2, wherein, The direct-drive XY motion platform is composed of a marble base, two permanent magnet linear synchronous motors, a linear motor mounting bed, a motor mounting bracket, a mover workbench, a linear guide rail and a grating detection device, the two permanent magnet linear synchronous motors are mounted on the linear motor mounting bed in an X-Y orthogonal form through the motor mounting bracket, wherein the lower motor is an X-axis motor, the upper motor is a Y-axis motor, N-pole and S-pole permanent magnets are alternately mounted on the stator of the permanent magnet linear synchronous motor, and an armature winding is mounted on the mover; the linear motor mounting bed is fixed on the marble base and is made of cast iron, a pad iron for adjusting height and balance is arranged under the linear motor mounting bed, the motor mounting bracket is made of aluminum alloy and the grating detection device is attached to the surface of the motor mounting bracket, the reading head of the grating detection device is mounted on the movers of the X-axis motor and the Y-axis motor through bolts, the Y-axis motor is mounted on the mover platform of the X-axis motor, and the mover workbench is connected with the mover coil of the Y-axis, so that the movement of the XY motion platform is realized, the mover coils of the X-axis motor and the Y-axis motor are supported through the linear guide rail, and double-rolling guide rails are designed for the two axes.

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