A control method and system for reducing the error deflection angle of a double-screw workbench

Abstract

The present invention discloses a control method and system for reducing the error deflection angle of a double-screw worktable, which belongs to a control or regulation system, solves the problem of worktable deflection in the double-screw feeding system in the prior art, and has the beneficial effect of effectively reducing the deflection of the worktable and improving the target accuracy of the workpiece. The specific scheme is as follows: a thrust compensation device for reducing the error of the double-screw worktable, wherein the thrust compensation device is arranged in a through groove of a slider of the worktable; a data processing unit estimates the current of the motor on the d-axis and the q-axis, the angular velocity of the motor and the load torque of the motor through a filter, and obtains the error deflection angle of the worktable according to the real current of the motor on the d-axis and the real current of the motor on the q-axis, the real angular velocity of the motor and the real load torque of the motor; a controller obtains the force that the thrust compensation device needs to output according to the error deflection angle of the worktable; the controller controls the action of the thrust compensation device to push the worktable to deflect in the opposite direction.

Description

Technical Field

[0001] The invention relates to the field of screw worktables, and in particular to a control method and system for reducing the error deflection angle of a double screw worktable. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] The existing ball screw worktable is divided into single-screw drive and double-screw drive. The driving force of the single-screw drive cannot accurately act on the center of gravity of the moving part. Therefore, double-screw drive is mostly used at present. The inventor found that the existing double-screw drive is prone to synchronization errors of the two screws due to defects in the manufacturing process and errors in actual assembly, resulting in a deflection angle of the moving part after movement, making it impossible for the workpiece on the moving part to achieve the target accuracy in subsequent processing or testing. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a control method for reducing the error deflection angle of a double-screw worktable, effectively reducing the deflection angle error that occurs during the movement of the dual-drive ball screw worktable, and improving the accuracy of the workpiece on the worktable in subsequent processing or testing.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0006] A control method for reducing the error deflection angle of a double-screw worktable, comprising the following contents:

[0007] A thrust compensation device is arranged in the through slot of the worktable slide block;

[0008] The data acquisition unit acquires the current of the motor in the d-axis and the q-axis and the voltage of the motor in the double-screw workbench in the d-axis and the q-axis;

[0009] The data processing unit estimates the current of the motor on the d-axis and the q-axis, the angular velocity of the motor and the load torque of the motor through a filter, obtains the real current of the motor on the d-axis and the q-axis, the real angular velocity of the motor and the real load torque of the motor after multiple iterations, and obtains the error deflection angle of the workbench according to the real current of the motor on the d-axis and the q-axis, the real angular velocity of the motor and the real load torque of the motor;

[0010] The data processing unit sends the obtained error deflection angle of the workbench to the controller, and the controller obtains the force that the thrust compensation device needs to output according to the error deflection angle of the workbench;

[0011] The controller controls the thrust compensation device to push the workbench to deflect in the opposite direction to reduce the error deflection angle of the workbench.

[0012] As described above, a control method for reducing the error deflection angle of a double-screw workbench is provided with a pressure sensor on the side wall of the through groove of the workbench slider, the pressure sensor is located on one side of the workbench, and the pressure sensor is connected to the controller.

[0013] In the control method for reducing the error deflection angle of a double-screw worktable as described above, the data processing unit estimates the motor current on the d-axis and the q-axis, the motor angular velocity and the motor load torque through a Kalman filter.

[0014] As described above, a control method for reducing the error deflection angle of a double-screw worktable is described, wherein the data processing unit inputs the real current of the motor on the d-axis, the real current of the motor on the q-axis, the real angular velocity of the motor and the real load torque of the motor into the double-screw error model to obtain the error deflection angle of the worktable.

[0015] A control method for reducing the error deflection angle of a double-screw worktable as described above, wherein the double-screw error model includes a PMSM vector control model and a mechanical system model, the Kalman filter is connected to the PMSM vector control model, and the angular velocity output by the Kalman filter is connected to the speed loop of the PMSM vector control model;

[0016] The output angular velocities of the two PMSM vector control models serve as two inputs of the mechanical system model.

[0017] In the control method for reducing the error deflection angle of a double-screw worktable as described above, the mechanical system model is established by the dynamic formula of the double-screw error model, and the dynamic formula of the double-screw error model is obtained by the following content:

[0018] Obtaining the output torque of the motor for driving the lead screw;

[0019] Get the load torque of the motor;

[0020] The angular velocity of the motor is obtained according to the output torque of the motor and the load torque of the motor;

[0021] The thrust of the screw on the workbench is obtained according to the axial displacement converted by the screw lead according to the screw rotation angle and the actual displacement of the workbench;

[0022] The dynamic formula of the double-screw error model is obtained according to the angular velocity of the motor and the thrust of the screw on the workbench.

[0023] A control method for reducing the error deflection angle of a double-screw worktable as described above, wherein the thrust compensation device comprises a plurality of compensation components, the plurality of compensation components are sequentially arranged along the length direction of the through slot, the compensation components between two adjacent compensation components and the end side are connected to the side wall of the through slot by a spring pin, each compensation component comprises a first plate and a second plate, the first plate and the second plate are arranged at a distance, an elastic member is connected between the first plate and the second plate, the outer side of the elastic member contacts the side of the worktable, a driving motor is fixed on the side of the first plate away from the second plate, the side of the driving motor away from the first plate is connected to the steering gear, each end of the steering gear is connected to a traction rope, and the traction rope passes through the first plate and is connected to the second plate;

[0024] The drive motor is connected to the controller, and the controller controls the drive motor to rotate to tighten the traction rope through the steering gear. The elastic member is compressed and bent in the radial direction of the first plate. At the same time, the elastic member generates a thrust toward the working surface to push the workbench to deflect in the opposite direction.

[0025] A control method for reducing the error deflection angle of a double-screw worktable as described above, wherein the servo is a cross-type servo;

[0026] The elastic member is a spring sheet, and the spring sheet is evenly arranged between the first plate and the second plate.

[0027] As described above, a control method for reducing the error deflection angle of a double-screw worktable is provided, wherein the controller obtains the thrust that each compensation component needs to generate based on half the length of the side surface of the worktable, i representing the i-th compensation component, the distance between two adjacent compensation components, the error deflection angle of the worktable and the rotational inertia of the motor, where i is a natural number.

[0028] In a second aspect, the present invention further provides a control system for reducing the error deflection angle of a double-screw worktable, comprising two screws, the two screws supporting the worktable, one of the two screws being connected to a controller, and the controller being connected to a thrust compensation device;

[0029] A data acquisition unit, the data acquisition unit acquires the current of the motor in the d-axis and the q-axis and the voltage of the motor in the double-screw workbench in the d-axis and the q-axis;

[0030] A data processing unit estimates the motor current on the d-axis and the q-axis, the motor angular velocity and the motor load torque through a filter, obtains the real motor current on the d-axis and the q-axis, the real angular velocity and the real load torque of the motor after multiple iterations, and obtains the error deflection angle of the workbench according to the real motor current on the d-axis and the q-axis, the real angular velocity and the real load torque of the motor; the data processing unit sends the obtained error deflection angle of the workbench to the controller, the controller obtains the force that the thrust compensation device needs to output according to the error deflection angle of the workbench, and the controller controls the thrust compensation device to drive the workbench to deflect in the opposite direction to reduce the error deflection angle of the workbench.

[0031] The beneficial effects of the present invention are as follows:

[0032] 1) The thrust compensation device of the present invention is reasonably structured. The thrust compensation device includes a plurality of compensation components. Two adjacent compensation components are connected by spring pins. The drive motor can rotate. The drive motor is connected to the steering gear, and the steering gear can be controlled to rotate and tighten the traction rope, so that the elastic member between the first plate and the second plate can expand outward, thereby generating thrust on the side of the workbench. By arranging multiple compensation components in the through groove, different thrusts can be generated at different positions of the workbench to avoid excessive compensation, thereby offsetting the error deflection angle of the workbench through the radial thrust of the elastic member.

[0033] 2) In the present invention, a pressure sensor is arranged on the side of the workbench, and the pressure sensor is connected to the controller. The controller obtains the value of the pressure sensor. When the thrust exerted on the side of the workbench obtained by the pressure sensor meets the requirement, the controller controls the driving motor to stop rotating, which can effectively control the magnitude of the force generated by the thrust compensation device, and is further beneficial to ensure the effective control of the error deflection angle of the workbench.

[0034] 3) The provision of the dual-screw feed system in the present invention can accurately obtain the error deflection angle of the worktable and control the thrust compensation device to work in a timely manner, effectively reducing the deflection angle error of the dual-drive ball screw worktable during movement, and improving the accuracy of the workpiece on the worktable in subsequent processing or testing.

[0035] 4) The present invention uses a Kalman filter to calculate the error technology. The Kalman filter can effectively reduce the impact of noise on the accuracy of model calculation; the error deflection angle actually generated by the double-screw feed system is calculated according to the double-screw error model, effectively improving the accuracy of the error deflection angle of the workbench obtained.

[0036] 5) The present invention provides a control method for reducing the error deflection angle of a double-screw workbench. The data acquisition unit collects the current and voltage data related to the motor, and then the data processing unit obtains the real current, motor angular velocity, etc., and obtains the error deflection angle of the workbench based on the real current and motor angular velocity, thereby effectively ensuring the accuracy of the error deflection angle. The controller calculates the thrust that the thrust compensation device needs to provide to the workbench, so that the thrust compensation device is actuated to reversely deflect the workbench, and the control is reasonable and effective. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0038] Figure 1 It is a schematic diagram of a double-screw worktable in a control method for reducing the error deflection angle of a double-screw worktable according to one or more embodiments of the present invention.

[0039] Figure 2 It is a side view of a thrust compensation device installed in a double-screw feed system in a control method for reducing the error deflection angle of a double-screw worktable according to one or more embodiments of the present invention.

[0040] Figure 3 The present invention Figure 2 Enlarged schematic diagram of the BB section.

[0041] Figure 4 It is an enlarged schematic diagram of a thrust compensation device at a slider through groove in a control method for reducing the error deflection angle of a double-screw worktable according to one or more embodiments of the present invention.

[0042] Figure 5 It is a schematic diagram of a compensation component in a thrust compensation device in a control method for reducing the error deflection angle of a double-screw worktable according to one or more embodiments of the present invention.

[0043] Figure 6 It is a front view of a thrust compensation device in a control method for reducing the error deflection angle of a double-screw worktable according to one or more embodiments of the present invention.

[0044] Figure 7 It is the first PMSM vector control model in a control method for reducing the error deflection angle of a double-screw worktable according to one or more embodiments of the present invention.

[0045] Figure 8 It is a mechanical system model in a control method for reducing the error deflection angle of a double-screw worktable according to one or more embodiments of the present invention.

[0046] Fig. 9 It is a schematic diagram of a double-screw worktable in a working state in a control method for reducing the error deflection angle of a double-screw worktable according to one or more embodiments of the present invention.

[0047] Fig.10 It is a control flow diagram of a control method for reducing the error deflection angle of a double-screw worktable according to one or more embodiments of the present invention.

[0048] In the figure: the distances or sizes between parts are exaggerated to show the positions of various parts, and the schematic diagram is for reference only.

[0049] Among them: 1. Screw, 2. Slider, 3. Workbench, 4. Guide rail, 5. Thrust compensation device, 6. Base;

[0050] 1-1. first screw, 1-2. second screw;

[0051] 2-1.Through groove;

[0052] 5-1. Spring pin, 5-2. Traction rope, 5-3. Elastic member, 5-4. Servo, 5-5. Driving motor, 5-6. First plate, 5-7. Second plate. DETAILED DESCRIPTION

[0053] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0054] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless otherwise explicitly stated in the present invention, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof;

[0055] As introduced in the background technology, the deflection angle generated during the operation of the double-screw worktable in the prior art cannot be eliminated. In order to solve the above technical problem, the present invention proposes a control method for reducing the error of the double-screw worktable.

[0056] Embodiment 1

[0057] In a typical embodiment of the present invention, this embodiment provides a control method for reducing the error of a double-screw workbench, referring to Fig.10 As shown, including the following:

[0058] A thrust compensation device is arranged in the through slot of the worktable slide block;

[0059] The data acquisition unit measures the current i of the motor on the d-axis in the double-screw workbench in real time d and the current i on the q axis q and the voltage u on the d-axis d and the voltage u on the q axis q ;

[0060] The data processing unit uses a filter to process the motor current i on the d-axis. d and the current i on the q axis q 、Motor angular velocity ω e and motor load torque T L Estimate and obtain the actual motor current i on the d-axis after multiple iterations d * and the real motor current i in the q axis q *、The actual motor angular velocity ω e * and the actual motor load torque T L *, and the real motor current i in the d-axis d * and the real motor current i in the q axis q *、The actual motor angular velocity ω e * and the actual motor load torque T L *Substitute into the double screw error model for calculation to obtain the error deflection angle θ of the workbench er ;

[0061] The data processing unit sends the obtained error deflection angle of the workbench to the controller, and the controller obtains the force that the thrust compensation device needs to output according to the error deflection angle of the workbench;

[0062] The controller controls the thrust compensation device to push the workbench to deflect in the opposite direction to reduce the error deflection angle of the workbench;

[0063] Moreover, a pressure sensor is arranged on the side wall of the through groove of the workbench slider. The pressure sensor is located on one side of the workbench and is connected to the controller. The controller obtains the value of the pressure sensor. When the thrust exerted on the side of the workbench obtained by the pressure sensor meets the requirements, the controller controls the drive motor to stop rotating.

[0064] refer to Figure 2 , Figure 3 and Figure 4As shown, the thrust compensation device 5 includes a plurality of compensation components, which are arranged in sequence along the length direction of the through slot, and the compensation components between two adjacent compensation components and the end side are connected to the side wall of the through slot through a spring pin 5-1, and each compensation component includes a first plate 5-6 and a second plate 5-7, which are arranged at a distance from each other, and an elastic member 5-3 is connected between the first plate 5-6 and the second plate 5-7, and the outer side of the elastic member contacts the side of the workbench 3, and a driving motor is fixed on the side of the first plate away from the second plate, and the side of the driving motor 5-5 away from the first plate is connected to the steering gear 5-4, and each end of the steering gear 5-4 is connected to a traction rope 5-2, and the traction rope passes through the first plate and connects the second plate;

[0065] The drive motor is connected to the controller, which can be a PLC controller or other types of controllers. The controller controls the drive motor to rotate to tighten the traction rope through the servo. The elastic member is compressed and bent in the radial direction of the first plate 5-6. At the same time, the elastic member 5-3 generates a thrust toward the working surface to push the workbench to deflect in the opposite direction to which the workbench has already deflected.

[0066] In this embodiment, the pressure sensor is arranged on the side of the workbench facing the through groove. Specifically, multiple pressure sensors are set on the side of the workbench, and the setting position of the pressure sensor corresponds to the position of each elastic part in contact with the side of the workbench; the pressure sensor is connected to the controller, and the controller obtains the value of the pressure sensor. When the thrust generated by the compensation component to the workbench obtained by the pressure sensor meets the requirements, the controller controls the drive motor to stop rotating.

[0067] Wherein, the controller may be a PLC controller or other types of controllers;

[0068] Understandably, reference Figure 5 , Figure 6 As shown, the steering gear 5-4 is a cross-shaped component, the movable end of the driving motor is fixedly connected to the center of the steering gear, and each end of the steering gear is arranged beyond the driving motor; the elastic member 5-3 is a spring sheet with a set width, and the spring sheets are evenly arranged between the first plate 5-6 and the second plate 5-7. Specifically, there can be 4 spring sheets, and both ends of the spring sheets are bent. One end of each spring sheet is fixed to a side of the second plate close to the first plate, and the other end of the spring sheet is fixed to a side of the first plate close to the second plate. The spring sheet is located between the first plate and the second plate;

[0069] Correspondingly, the traction rope 5-2 connected to the end of the servo is arranged between two adjacent elastic members. The traction rope can be a steel wire rope. One end of the traction rope can be fixed by tying a knot after passing through the second plate, or fixed by an existing rope clamp.

[0070] In this embodiment, the first plate and the second plate can both be circular plates, and the structures and sizes of the first plate and the second plate are the same;

[0071] It needs to be explained that the length direction of the slider slot 2-1 is arranged along the width direction of the workbench, and at least three compensation components can be arranged in the slot. Two of the three compensation components are arranged in the same direction, and the other compensation component is arranged opposite to the adjacent compensation component, that is, the servo of the compensation component is close to the servo of the adjacent compensation component.

[0072] Therefore, after the data processing unit sends the error deflection angle of the workbench obtained by it to the controller, the controller controls the driving motors in the compensation component to rotate to tighten the traction rope through the steering gear, and the elastic member is compressed to bend in the radial direction of the first plate. At the same time, the elastic member generates a thrust toward the working surface. Under the action of the thrust, the workbench deflects in the opposite direction (opposite to the current deflection direction of the workbench) to reduce the error deflection angle θ of the workbench. er ;

[0073] It should be noted that the motor of the double-screw workbench is a permanent magnet synchronous motor, and the data acquisition unit is specifically an existing server connected to the permanent magnet synchronous motor, through which the current of the motor on the d-axis and the current on the q-axis and the voltage on the d-axis and the voltage on the q-axis can be obtained;

[0074] The data processing unit estimates the motor current on the d-axis and the q-axis, the motor angular velocity and the motor load torque through the Kalman filter, including the following contents:

[0075] Among them, the Kalman filter is used for the i of the permanent magnet synchronous motor d and i q And the speed ω e and motor load T L Make an estimate and obtain the real current i after multiple iterations d * and i q * and speed ω e * and motor load T L *, including the following:

[0076] 2-1) Update the predicted state, that is, obtain the predicted estimated value of the state at time k+1, and obtain the predicted estimated value of the state at time k+1 through the state transfer matrix, the estimated value of the state at time k, the input control matrix and the control amount at time k:

[0077] x(k+1|k)=Ax(k|k)+Bu(k) (1)

[0078] Where x(k+1|k) represents the predicted estimated value of the state at time k+1, A represents the state transfer matrix, x(k|k) represents the estimated value of the state at time k, B is the input control matrix, and u(k) represents the control amount at time k;

[0079] Among them, the input control matrix

[0080] u(k+1)=(u d u q ) T ;

[0081] According to the mathematical model of the motor, the state equation and output equation of the system are established.

[0082]

[0083] Among them, w(t) and v(t) are noise errors, which conform to the normal distribution, and the observation matrix Measurement Matrix

[0084] The mathematical model of the permanent magnet synchronous motor PMSM is matrixed, x(t) is the state equation, x(t) = [i d i q ,ω e T L ] T ,i d and ix are the d-axis and q-axis currents in the dq0 coordinate system, respectively. The ABC coordinate system is transformed by Clark transformation (referring to transforming ABC into the stationary αβ coordinate system) and Park transformation (referring to transforming ABC into the rotating dq coordinate system) to obtain the d-axis and q-axis currents, ω e is the motor angular velocity, and the motor load T during the Kalman filter process L is the steady-state value, which is 0 after differentiation. The state transfer matrix A can be obtained and expressed by formula (3).

[0085]

[0086] Where, R is the stator resistance, L is the armature inductance, K t is the torque constant, J m is the motor moment of inertia, B m is the motor viscosity coefficient, ψ is the rotor flux amplitude, P n are the number of motor pole pairs, which are fixed parameters of the motor.

[0087] 2-2) The covariance update of the predicted state is obtained by the estimated value of the state covariance at time k, the state transfer matrix and the covariance matrix of the process noise at time k+1;

[0088] P(k+1|k)=AP(k|k)A T +Q(k+1) (4)

[0089] Among them, P(k+1|k) represents the predicted value of the state covariance at time k+1, P(k|k) represents the estimated value of the state covariance at time k, and Q(k+1) represents the covariance matrix of the process noise at time k+1;

[0090] in,

[0091] P0 represents the starting value of P(k|k).

[0092] 2-3) Update the Kalman gain by the predicted value of the state covariance at time k+1, the measurement matrix, and the covariance matrix of the measurement noise:

[0093] K(k+1)=P(k+1k)H(k+1)^T(H(k+1)P(k+1k)H(k+1)^T+R(k+1))^-1(5)

[0094] Wherein, K(k+1) represents the Kalman gain at time k+1, H(k+1) represents the measurement matrix at time k+1, specifically the measurement matrix H is used, and R(k+1) represents the covariance matrix of the measurement noise;

[0095] in,

[0096] 2-4) Update the estimated value of the state at time k by the predicted estimated value of the state at time k+1, the Kalman gain at time k+1, the measured value at time k+1 and the measurement matrix;

[0097] ×(k+1|k+1)=×(k+1|k)+K(k+1)(z(k+1)-H(k+1)×(k+1|k)) (6)

[0098] Where x(k+1|k+1) represents the estimated value of the state at time k+1 after the update, and z(k+1) represents the measured value at time k;

[0099] 2-5) Obtain the predicted value of the state covariance at the update time k+1 through the unit matrix, the Kalman gain at the time k+1, the measurement matrix and the predicted value of the state covariance at the time k+1;

[0100] P(k+1|k+1)=(IK(k+1)H(k+1))P(k+1|k) (7)

[0101] Among them, P(k+1|k+1) is the estimated value of the state covariance at time k+1 after the update, and I is the identity matrix.

[0102] It should be noted that permanent magnet synchronous motors often use d-axis current of 0, so i d =0.

[0103] It should be noted that the data processing unit can be an existing computer terminal, and the real current of the motor on the d-axis, the real current of the motor on the q-axis, the real angular velocity of the motor and the real load torque of the motor are input into the double-screw error model to obtain the error deflection angle of the workbench;

[0104] The double-screw error model includes a PMSM (permanent magnet synchronous motor) vector control model and a mechanical system model. Since the double-screw workbench has two permanent magnet synchronous motors, it has a first PMSM vector control model and a second PMSM vector control model. The Kalman filter is connected to the PMSM vector control model, and the angular velocity ω output by the Kalman filter is e * The first PMSM vector control model formed by connecting to the PMSM speed loop is shown in Figure 7 As shown, the angular velocity ω output by the Kalman filter e * Connecting to the speed loop of PMSM and performing negative feedback on the speed loop controller is beneficial to making the q-axis current loop output by the speed loop controller more accurate. The second PMSM vector control model is the same as the first PMSM vector control model;

[0105] refer to Figure 8 As shown in the figure, the output angular velocities of the two PMSM vector control models are used as the two inputs of the mechanical system model. e *, the error deflection angle θ of the workbench can be obtained er , the Kalman filter is connected to the double screw error model, which effectively improves the error angle θ calculated by the model. er accuracy.

[0106] In this embodiment, the mechanical system model is established by the dynamic formula of the double screw error model. Fig. 9 As shown in Figure 2, the dynamic formula of the double screw error model includes:

[0107]

[0108]

[0109] Among them, M t is the weight of the workbench, L1 and L2 are the distances from the two screws to the center axis of the workbench, J t is the moment of inertia of the table, X m is the actual displacement of the workbench;

[0110] The dynamic formula of the double screw error model is obtained through the following:

[0111] Get the output torque of the motor. The output torque of the motor is T = K t i q , refers to the torque constant K t and q-axis current i q The product of .

[0112] Get the load torque of the motor, the load torque T of the motor L =K L (θ m -θ s ), (In the Kalman filter, the load torque of the motor is also estimated, just to improve i q * and ω e *, but the motor load torque in the Kalman filter is not used in the calculation of the double screw error model. Instead, the motor load torque T calculated by the double screw error model is used. L );

[0113] Get the angular velocity of the motor through The angular velocity ω of the motor can be calculated e , which is the angular velocity of the motor rotor.

[0114] Among them, K L is the equivalent torsional stiffness of the double screw feed system, θ m is the motor rotor angle, which is determined by the motor angular velocity ω e Perform an integral to obtain, θ s The screw rotation angle can be expressed by the formula Get, P L is the lead of the screw, t is the setting time, F i is the thrust of the screw on the workbench, J s is the moment of inertia of the screw;

[0115] In addition, the thrust of the screw on the workbench is based on F i =K d (X s -X m ) is obtained, where X s The screw rotation angle is calculated according to the screw lead (P L ) converted axial displacement, K d is the equivalent axial stiffness of the double screw feed system, and the axial displacement X converted by the screw s according to get;

[0116] The actual displacement of the workbench is X m according to Get, Ft =F1+F2, F1 is the thrust of the first screw on the workbench, F2 is the thrust of the second screw on the workbench, F t It is the total thrust of the two screws on the workbench;

[0117] Thus, the dynamic formula of the double-screw error model can be obtained, and the error deflection angle of the workbench can be obtained through the dynamic formula of the double-screw error model.

[0118] In order to further ensure the accuracy of the error deflection angle of the workbench, the friction and stress are added to the dynamic formula of the double screw error model. where F f1 and F f2 The friction between the first and second lead screws and the workbench is obtained by empirical formula, F st F is the stress of the screw on the workbench, st =K L *θ er ).

[0119] In addition, the output displacement y1 of the first screw to the worktable and the output displacement y2 of the second screw to the worktable can be obtained, y1 = y m +L1θ er ,y2=y m -L2θ er .

[0120] The data processing unit calculates the error deflection angle θ of the workbench er The controller sends a command to the drive motor. When the drive motor receives the command from the controller, it rotates and tightens the traction rope, shortening the axial length of the thrust compensation device. The spring sheet is compressed and bent in the radial direction, increasing the radial length. At the same time, the spring sheet generates thrust on the workbench in the radial direction. Since a thrust compensation device is set in the through slot of the slider, multiple compensation components will be adjusted according to θ. er Generate a force to offset the error deflection angle θ of the worktable er .

[0121]

[0122] where f i is the thrust generated by a single compensation component, b is half the length of the side of the worktable, i is the number of thrust compensation devices, and Δx is the distance between the compensation components;

[0123] The corresponding thrust compensation device on the side of the workbench is provided with a pressure sensor, which detects the thrust f generated by a single compensation component in the thrust compensation device to the workbench through the pressure sensor. i , and the controller calculates the resultant force generated by the entire thrust compensation device Eliminate the error deflection angle θ of the workbench er .

[0124] Among them, it should be noted that Figure 7 The PI in the equation refers to the proportional-integral controller. The position loop controller can be a sliding mode controller, a fuzzy sliding mode controller or an adaptive controller, etc. Clark refers to Clark transformation, which is a commonly used coordinate transformation method in motor control. Its essence is to transform the variables in the three-phase static abc coordinate system with a 120° difference to the two-phase static αβ coordinate system with a 90° difference. Park and Anti-Park refer to Park transformation and anti-Park transformation. Park transformation transforms the static α and β two-phase coordinates into rotating dq two-phase coordinates, while anti-Park transformation transforms the rotating dq two-phase coordinates into static α and β two-phase coordinates. SVPWM space vector pulse width modulation (Space Vector Pulse Width Modulation) is a pulse width modulation technology used for three-phase motor control. It generates different voltage vectors by controlling the switching states of three power switching devices to achieve precise control of the motor. Two-level Converter refers to a power electronic converter that has two output levels, high and low, and can control the output voltage level according to the input signal (such as SVPWM signal), control the voltage and frequency of the motor, and achieve precise speed and torque control;

[0125] Figure 8 Middle J s ·S 2 Middle J s is the moment of inertia of the screw, and S is the Laplace operator.

[0126] In this embodiment, a double-screw error model is provided, and a Kalman filter is used in the double-screw error model to improve the calculation accuracy of the error deflection angle. Currently, there is no solution using a Kalman filter to calculate the double-screw deflection angle. The Kalman filter can effectively reduce the influence of noise on the calculation accuracy of the model. The data processing unit calculates the error deflection angle actually generated by the double-screw feed system according to the double-screw error model, and offsets the error deflection angle through the radial thrust of the thrust compensation device. At the same time, when offsetting the error deflection angle, the thrust is not directly generated by the drive motor, but the elastic force generated by the drive motor to drive the elastic part to contract to push the workbench to deflect, so as to prevent the excessive force generated by the drive motor from causing over-compensation, thereby increasing the error deflection angle. After experimental testing, the double-screw workbench can directly obtain the difference in the output displacement of the two screws on the workbench. The error accuracy calculated using the double-screw error model provided in this embodiment is higher than that of the error model without using the Kalman filter.

[0127] Embodiment 2

[0128] The present embodiment provides a control system for reducing the error deflection angle of a double-screw worktable, comprising a base 6, the base 6 is provided with two screws 1, the screws are a first screw 1-1 and a second screw 1-2, the base 6 is provided with a guide rail 4, the two screws support the same worktable 3, the worktable 3 cooperates with the guide rail 4 through a slider 2, one of the two screws is connected to a controller, the controller is connected to a thrust compensation device, and the thrust compensation device is the thrust compensation device in the first embodiment;

[0129] A data acquisition unit, the data acquisition unit acquires the current of the motor in the d-axis and the q-axis and the voltage of the motor in the double-screw workbench in the d-axis and the q-axis;

[0130] A data processing unit estimates the motor current on the d-axis and the q-axis, the motor angular velocity and the motor load torque through a filter, obtains the real current of the motor on the d-axis and the q-axis, the real angular velocity of the motor and the real load torque of the motor after multiple iterations, and obtains the error deflection angle of the workbench according to the real current of the motor on the d-axis and the q-axis, the real angular velocity of the motor and the real load torque of the motor; the data processing unit sends the obtained error deflection angle of the workbench to the controller, the controller obtains the force that the thrust compensation device needs to output according to the error deflection angle of the workbench, and the controller controls the drive motor to work so as to tighten the traction rope through the servo.

[0131] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A control method for reducing the error deflection angle of a double-screw worktable, characterized in that: It includes the following: A thrust compensation device is arranged in the through slot of the worktable slide block; The data acquisition unit acquires the current of the motor in the d-axis and the q-axis and the voltage of the motor in the double-screw workbench in the d-axis and the q-axis; The data processing unit estimates the current of the motor on the d-axis and the q-axis, the angular velocity of the motor and the load torque of the motor through a filter, obtains the real current of the motor on the d-axis and the q-axis, the real angular velocity of the motor and the real load torque of the motor after multiple iterations, and obtains the error deflection angle of the workbench according to the real current of the motor on the d-axis and the q-axis, the real angular velocity of the motor and the real load torque of the motor; The data processing unit sends the obtained error deflection angle of the workbench to the controller, and the controller obtains the force that the thrust compensation device needs to output according to the error deflection angle of the workbench; The controller controls the thrust compensation device to push the workbench to deflect in the opposite direction to reduce the error deflection angle of the workbench; The thrust compensation device comprises a plurality of compensation components, which are arranged in sequence along the length direction of the through slot, and the compensation components between two adjacent compensation components and the end side are connected to the side wall of the through slot by a spring pin, and each compensation component comprises a first plate and a second plate, which are arranged at a distance from each other, an elastic member is connected between the first plate and the second plate, and the outer side of the elastic member contacts the side of the workbench, a driving motor is fixed on the side of the first plate away from the second plate, and the side of the driving motor away from the first plate is connected to the steering gear, and each end of the steering gear is connected to a traction rope, which passes through the first plate and is connected to the second plate; The drive motor is connected to the controller, and the controller controls the drive motor to rotate to tighten the traction rope through the steering gear. The elastic member is compressed and bent in the radial direction of the first plate. At the same time, the elastic member generates a thrust toward the working surface to push the workbench to deflect in the opposite direction.

2. A control method for reducing the error deflection angle of a double-screw worktable according to claim 1, characterized in that: A pressure sensor is arranged on the side wall of the through groove of the workbench slider, the pressure sensor is located on one side of the workbench, and the pressure sensor is connected to the controller.

3. A control method for reducing the error deflection angle of a double-screw worktable according to claim 1, characterized in that: The data processing unit estimates the motor current on the d-axis and the q-axis, the motor angular velocity and the motor load torque through a Kalman filter.

4. A control method for reducing the error deflection angle of a double-screw worktable according to claim 3, characterized in that: The data processing unit inputs the real current of the motor on the d-axis, the real current of the motor on the q-axis, the real angular velocity of the motor and the real load torque of the motor into the double-screw error model to obtain the error deflection angle of the workbench.

5. A control method for reducing the error deflection angle of a double-screw worktable according to claim 4, characterized in that: The double-screw error model includes a PMSM vector control model and a mechanical system model, the Kalman filter is connected to the PMSM vector control model, and the angular velocity output by the Kalman filter is connected to the speed loop of the PMSM vector control model; The output angular velocities of the two PMSM vector control models serve as two inputs of the mechanical system model.

6. A control method for reducing the error deflection angle of a double-screw worktable according to claim 5, characterized in that: The mechanical system model is established by the dynamics formula of the double screw error model, and the dynamics formula of the double screw error model is obtained by the following content: Obtaining the output torque of the motor for driving the lead screw; Get the load torque of the motor; The angular velocity of the motor is obtained according to the output torque of the motor and the load torque of the motor; The thrust of the screw on the workbench is obtained according to the axial displacement converted by the screw lead according to the screw rotation angle and the actual displacement of the workbench; The dynamic formula of the double-screw error model is obtained according to the angular velocity of the motor and the thrust of the screw on the workbench.

7. A control method for reducing the error deflection angle of a double-screw worktable according to claim 1, characterized in that: The steering gear is a cross-type steering gear; The elastic member is a spring sheet, and the spring sheet is evenly arranged between the first plate and the second plate.

8. A control method for reducing the error deflection angle of a double-screw worktable according to claim 1, characterized in that: The controller obtains the thrust that each compensation component needs to generate based on half the length of the side surface of the workbench, i representing the i-th compensation component, the distance between two adjacent compensation components, the error deflection angle of the workbench and the rotational inertia of the motor, where i is a natural number.

9. A control system for reducing the error deflection angle of a double-screw worktable, characterized in that: A control method for reducing the error deflection angle of a double-screw worktable as described in any one of claims 1 to 8 is implemented, comprising two screws, the two screws supporting the worktable, one of the two screws being connected to a controller, and the controller being connected to a thrust compensation device; A data acquisition unit, the data acquisition unit acquires the current of the motor in the d-axis and the q-axis and the voltage of the motor in the double-screw workbench in the d-axis and the q-axis; A data processing unit estimates the motor current on the d-axis and the q-axis, the motor angular velocity and the motor load torque through a filter, obtains the real motor current on the d-axis and the q-axis, the real angular velocity and the real load torque of the motor after multiple iterations, and obtains the error deflection angle of the workbench according to the real motor current on the d-axis and the q-axis, the real angular velocity and the real load torque of the motor; the data processing unit sends the obtained error deflection angle of the workbench to the controller, the controller obtains the force that the thrust compensation device needs to output according to the error deflection angle of the workbench, and the controller controls the thrust compensation device to drive the workbench to deflect in the opposite direction to reduce the error deflection angle of the workbench.

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