A robot force-controlled polishing end effector capable of tracking workpiece normal

Abstract

A robot force control polishing and grinding end effector capable of tracking the normal of a workpiece comprises a rotating assembly, a measuring assembly, a constant force control assembly, a motion decoupling assembly and a polishing and grinding disc assembly, the rotating assembly is installed on a connecting plate, the measuring assembly comprises a laser ranging assembly and an encoder assembly, the laser ranging assembly is installed on the upper side of the connecting plate, the encoder assembly is installed on the lower side of the connecting plate, the constant force control assembly is installed in connection with the connecting plate, the lower end of the motion decoupling assembly is provided with a lower mounting plate, the output end of the rotating assembly passes through the constant force control assembly and the lower mounting plate and is connected with the polishing and grinding disc assembly through the motion decoupling assembly, and the laser ranging assembly and the encoder assembly jointly constitute four measurements in different directions.The present application can realize tracking of the normal of the workpiece surface during polishing and grinding, accurate and coordinated control of polishing and grinding force and rotating speed and fast response speed, and has a simple and compact overall structure.

Description

Technical Field

[0001] This invention belongs to the field of robotic automated processing, specifically relating to a robotic force-controlled polishing end effector that can track the normal direction of a workpiece. Background Technology

[0002] With the development of industrial modernization, the widespread use of robots can liberate humans from heavy, dangerous, and heavily polluting working environments. Robotic operations can be categorized into non-contact and contact operations based on whether they involve contact. For non-contact operations, such as spraying and welding, force sensing capabilities are not required for robots to complete the task. However, for contact operations, such as clamping, grinding, polishing, and assembly, robots often require a certain level of contact sensing and adjustment capabilities. In grinding and polishing operations, the contact force has a significant impact on product quality and is crucial in preventing under-polishing or over-polishing. Therefore, controlling the contact force between the polishing tool and the workpiece is necessary and of great importance for achieving high-precision operations.

[0003] In robotic polishing, the polishing tool must maintain stable contact with the workpiece surface. This requires the tool to adapt to the freeform surface of the workpiece, meaning that throughout the robot's movement, the polishing tool must remain in perpendicular contact with the workpiece surface and be able to track the normal direction of the workpiece surface. Maintaining perpendicularity between the polishing tool and the workpiece surface facilitates control of the polishing force, significantly impacting the quality of the polishing process. Existing robotic force-controlled polishing end effectors struggle to effectively track the workpiece's orientation and require further improvement. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a robotic force-controlled polishing end effector capable of tracking the workpiece normal. Without prior knowledge of the orientation, it actively tracks the normal of the workpiece surface, improving the force control effect of the robotic polishing operation and further enhancing product quality.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A robotic force-controlled polishing end effector capable of tracking the normal direction of a workpiece includes a rotating component, a measuring component, a constant force control component, a motion decoupling component, and a polishing disc assembly. The rotating component is mounted on a connecting plate. The measuring component includes a laser ranging component and an encoder assembly. The laser ranging component is mounted on the upper side of the connecting plate, and the encoder assembly is mounted on the lower side of the connecting plate. The constant force control component is mounted and connected to the connecting plate. A lower mounting plate is mounted on the upper part of the motion decoupling component. The output end of the rotating component passes through the constant force control component and the lower mounting plate, and then connects to the polishing disc assembly through the motion decoupling component. The laser ranging component and the encoder assembly together constitute measurements in four different directions.

[0007] The rotating assembly includes a motor, a motor bracket, an upper coupling, a main shaft, and a seated bearing. The motor is mounted on a connecting plate via the motor bracket, the motor's output shaft is connected to the main shaft via the upper coupling, the bearing is mounted on the connecting plate, and the main shaft passes through the seated bearing.

[0008] The laser ranging assembly includes a sensor mounting plate, a first laser ranging sensor, a second laser ranging sensor, and a third laser ranging sensor. The first laser ranging sensor, the second laser ranging sensor, and the third laser ranging sensor are respectively mounted on the sensor mounting plate via mounting brackets. The first laser ranging sensor, the second laser ranging sensor, and the third laser ranging sensor are distributed at 90-degree intervals around the circumference of the sensor mounting plate.

[0009] The sensor mounting plate is provided with three mounting seats. The lower part of the mounting bracket is locked to the lower part of the mounting seat by screws. The upper part of the mounting bracket is provided with an adjustment slot, into which a bolt is inserted and fixedly connected to the mounting seat.

[0010] The encoder assembly includes an encoder component and a grating component. The encoder component includes a linear encoder, an encoder mounting plate, and a slider. The slider is mounted inside the encoder mounting plate. The linear encoder is connected to the encoder mounting plate by screws. The slider is located between the linear encoder and the encoder mounting plate. The encoder mounting plate is mounted and connected to a connecting plate. The grating component includes a slide rail, a grating plate, grating paper, and a grating mounting base. The bottom of the grating plate is mounted on the grating mounting base. The grating paper is attached to the grating plate. The slide rail is located on one side of the grating plate. The slide rail is inserted between the slider and the linear encoder and is movably engaged with the slider. The grating mounting base is mounted on a lower mounting plate.

[0011] The grating plate has a groove, and the grating paper is attached in the groove. The groove and the slide rail extend in the same direction.

[0012] The constant force control component includes a voice coil motor, a guide assembly, and a six-dimensional force sensor. The six-dimensional force sensor is mounted on one side of the connecting plate. The upper end of the guide assembly is connected to the connecting plate, and the lower end is connected to the lower mounting plate. The main shaft passes through the voice coil motor. The upper end of the voice coil motor is mounted to the connecting plate, and the lower end of the voice coil motor is connected to the lower mounting plate. The voice coil motor has a mover and a stator.

[0013] The guide assembly includes an optical axis and a linear bearing. The linear bearing is installed on the lower side of the connecting plate. The upper end of the optical axis is movably inserted into the linear bearing. The lower end of the optical axis is connected to the lower mounting plate by screws. A shaft end baffle is provided on the connecting plate directly opposite the position of the linear bearing.

[0014] The motion decoupling assembly includes a bearing housing, a retaining ring, a double-row angular contact ball bearing, and a spline sleeve. The bearing housing is connected to the lower mounting plate. The double-row angular contact ball bearing is installed in the bearing housing and secured by the retaining ring. The spline sleeve is installed in the bearing housing and has ball splines in it, which are assembled and connected to the spindle.

[0015] The polishing disc assembly includes a polishing disc mounting component, a lower coupling, and a polishing disc. The upper end of the polishing disc mounting component extends into the bearing housing and is connected to the main shaft. One end of the lower coupling is connected to the polishing disc mounting component, and the other end of the lower coupling is connected to the polishing disc.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects:

[0017] 1. The linear encoder and grating paper are assembled by using a combination of slide rail and slider. This makes the parallelism and parallel distance between the linear encoder and grating paper more stable when they move relative to each other, achieving the expected results. Moreover, this installation method can be used to install linear encoders and grating paper on other parallel parts.

[0018] 2. To ensure the accuracy of normal tracking during the polishing process, while using three laser rangefinders to measure the coordinates of three points around the polishing disc, a linear encoder is used to obtain high-precision coordinates at the polishing path points. Moreover, the coordinates obtained by the linear encoder have a direct impact on the fitting of the surface concavity and convexity, which is an effect that cannot be achieved by only measuring the surrounding points.

[0019] 3. To improve the installation and disassembly efficiency of laser rangefinder sensors, a sensor mounting plate is used for unified installation and disassembly, which can realize the transformation of the end effector from a general force-controlled polishing end effector to a force-controlled end effector that can be used for polishing of modelless workpieces.

[0020] 4. To accommodate different polishing disc sizes, the angle between the sensor mounting bracket and the sensor mounting plate can be adjusted, thereby adjusting the detection angle of the laser rangefinder sensor. This adjustment is convenient and flexible in use. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0022] Figure 2 This is a full sectional view of the overall structure of the present invention along the main axis and parallel to the side of the T-shaped plate;

[0023] Figure 3 This is a full sectional view of the overall structure of the present invention along the main axis and perpendicular to the side of the T-shaped plate;

[0024] Figure 4 This is a three-dimensional structural diagram of the encoder assembly described in this invention;

[0025] Figure 5 This is a schematic diagram of the encoder component in this invention;

[0026] Figure 6 This is a schematic diagram of the structure of the grating component in this invention;

[0027] Figure 7 This is a schematic diagram of the structure of the grating mounting base of the present invention;

[0028] Figure 8 This is an assembly diagram of the sensor mounting plate, laser rangefinder, and sensor mounting bracket of the present invention.

[0029] Figure 9 This is a schematic diagram of the sensor mounting plate in this invention;

[0030] Figure 10 This is a schematic diagram of the installation of the laser ranging sensor and the sensor mounting bracket in this invention.

[0031] Markings in the diagram: 1-Motor, 2-Motor bracket, 3-Upper coupling, 4-Spindle, 5-Bearing with seat, 6-Sensor mounting plate, 7-First laser rangefinder sensor, 8-First sensor mounting bracket, 9-Connecting plate, 10-Voice coil motor stator, 11-Voice coil motor mover, 12-Lower mounting plate, 13-Bearing housing, 14-Circlip for bore, 15-Double row angular contact ball bearing, 16-Polishing disc mounting component, 17-Polishing disc, 18-Lower coupling, 19-Spline sleeve, 20-Ball spline, 21-First... Two-sensor bracket; 22-Second laser rangefinder sensor, 23-Third laser rangefinder sensor, 24-Third sensor mounting bracket, 26, 31-Shaft end baffle, 27, 29-Optical axis, 28, 30-Linear bearing, 32-Six-dimensional force sensor, 33-Encoder assembly, 34-Encoder component, 341-Linear encoder, 342-Encoder mounting plate, 343-Slider, 35-Grate component, 351-Slide rail, 352-Grate plate, 353-Grate paper, 354-Grate mounting base. Detailed Implementation

[0032] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0033] In the description of this invention, it should be understood that if terms such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, they are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0034] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection. They can refer to a mechanical connection or an electrical connection. They can refer to a direct connection or an indirect connection through an intermediate medium, and they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0035] Example 1

[0036] refer to Figure 1 As shown, this invention discloses a robotic force-controlled polishing end effector capable of tracking the normal direction of a workpiece, comprising a rotating assembly, a measuring assembly, a constant force control assembly, a motion decoupling assembly, and a polishing disc assembly. The rotating assembly is mounted on a connecting plate 9. The measuring assembly includes a laser ranging assembly and an encoder assembly 33. The laser ranging assembly is mounted on the upper side of the connecting plate 9, and the encoder assembly 33 is mounted on the lower side of the connecting plate 9. The constant force control assembly is mounted and connected to the connecting plate. A lower mounting plate 12 is mounted on the upper part of the motion decoupling assembly. The output end of the rotating assembly passes through the constant force control assembly and the lower mounting plate 12, and then connects to the polishing disc assembly through the motion decoupling assembly. The laser ranging assembly and the encoder assembly together constitute measurements in four different directions. The connecting plate is a T-shaped plate, and it is inverted, that is, the upper horizontal part of the T-shaped plate is inverted and installed horizontally. The connecting plate serves as a load-bearing component of the overall structure.

[0037] The rotating component acts as the driving element, causing the polishing disc assembly to rotate. The laser ranging and encoder components are used to measure the coordinates of four points on the workpiece surface. After transforming these four point coordinates to a base coordinate system, they can be used for fitting local areas of the workpiece surface. In space, on a continuous curved surface, the curved surface of a small region around a point can be expressed by a bivariate quadratic function expression, i.e.

[0038] z = ax 2 +by 2 +cxy+dx+ey+f (1)

[0039] The unit normal vector at that point can be obtained by solving the formula:

[0040]

[0041] Solve for, where It involves finding the L2 norm of a vector. Therefore, by continuously acquiring points on the workpiece surface, we can continuously fit the expression of the workpiece surface, further calculate the unit normal vector at the polishing point, and then control the robot's posture so that the rotation axis direction of the end effector's rotating component coincides with this vector, thus achieving the effect of workpiece surface normal tracking.

[0042] Example 2

[0043] refer to Figure 1-10 As shown, the rotating assembly includes a motor 1, a motor bracket 2, an upper coupling 3, a main shaft, and a seated bearing 5. A flange is provided on one side of the output shaft of the motor 1, through which it is mounted to the motor bracket 2 and secured with screws. The motor bracket 2 is mounted on a connecting plate 9. The output shaft of the motor 1 is connected to the main shaft 4 via the upper coupling 3. The seated bearing 5 is mounted on the connecting plate 9, and the main shaft 4 passes through the seated bearing 5, forming a rotatable connection with it. A ball spline 20 can be fitted at the end of the main shaft. The main shaft 4 transmits power to the ball spline 20 through the balls in the ball spline 20. The main shaft 4 and the ball spline 20, when used together, have the characteristics of circumferential fixation and axial relative movement. The main shaft 4 passing through the seated bearing improves the coaxiality of the main shaft 4 during rotation.

[0044] The laser ranging assembly includes a sensor mounting plate 6, a first laser ranging sensor 7, a second laser ranging sensor 22, and a third laser ranging sensor 23. The sensor mounting plate 6 is connected to a connecting plate 9. The sensor mounting plate 6 is equipped with a first mounting base 61, a second mounting base 62, and a third mounting base 63. A first sensor bracket 8 is mounted on the first mounting base 61, a second sensor bracket 21 is mounted on the second mounting base 62, and a third sensor bracket 24 is mounted on the third mounting base 63. The first laser ranging sensor 7 is mounted on the first sensor bracket 8, the second laser ranging sensor 22 is mounted on the second sensor bracket 21, and the third laser ranging sensor 23 is mounted on the third sensor bracket 24. The first laser ranging sensor 7, the second laser ranging sensor 22, and the third laser ranging sensor 23 are distributed at 90-degree intervals around the circumference of the sensor mounting plate 6, thereby measuring the coordinates of three different points on the workpiece.

[0045] Furthermore, to facilitate angle adjustment, the lower part of the first sensor bracket 7 is bolted to the first mounting base 61. This bolt acts as a pivot, allowing the lower part of the first sensor bracket to rotate. The upper part of the first sensor bracket has an adjustment slot into which a bolt is inserted and securely connected to the mounting base. Rotating the first sensor bracket changes the position of the adjustment slot, allowing the bolt to be tightened, thus adjusting the installation angle of the first sensor bracket and consequently the angle of the first laser rangefinder sensor to meet different angle measurement requirements. The assembly structure of the second sensor bracket and second mounting base, and the third sensor bracket and third mounting base, is also as described above.

[0046] The encoder assembly 33 includes an encoder component 34 and a grating component 35. The encoder component 34 is positioned using the profile of the lower end face of the connecting plate 9 and is fixed to the connecting plate 9 by screws. The grating component 35 is positioned using the profile of the upper end face of the lower mounting plate 12 and is positioned by screws.

[0047] The encoder component 34 includes a linear encoder 341, an encoder mounting plate 342, and a slider 343. The slider 343 is mounted inside the encoder mounting plate 342. The linear encoder 341 is connected to the encoder mounting plate 342 by screws. The slider 343 is located between the linear encoder 341 and the encoder mounting plate 342, such that the reading hole of the linear encoder 341 faces the slider 343. The encoder mounting plate 342 is mounted and connected to the connecting plate 9 and remains stationary, while the linear encoder can move synchronously with the slide rail. The grating component 35 includes a slide rail 351, a grating plate 352, a grating paper 353, and a grating mounting base 354. The bottom of the grating plate 352 is mounted on the grating mounting base 354. The grating paper 353 is attached to the grating plate 352. The slide rail 351 is located on one side of the grating plate 352. The slide rail 352 is inserted between the slider 343 and the linear encoder 341 and is movably engaged with the slider 343. The grating mounting base 354 is mounted on the lower mounting plate 12. The grating plate 352 has a groove, and the grating paper 353 is attached to the groove for easy positioning. The groove extends in the same direction as the slide rail. After all components are assembled, they are positioned and installed using the profile and slot on the grating mounting base 354, and fixed with screws through the threaded holes on the side of the grating mounting base 354. In this way, the entire grating component 35 becomes a whole, and the grating paper 353 is placed parallel to the working surface of the slide rail 351. When the slider 343 moves relative to the slide rail 351, the grating paper 353 moves relative to the slider in the same way. Thus, the coordinates of the center point of the polishing disc assembly can be obtained by calculating the readings of the linear encoder 341.

[0048] The sliding structure of the slide rail and slider provides greater stability and higher accuracy, ensuring the stability of encoder measurements.

[0049] Example 3

[0050] refer to Figure 1-10 As shown, the constant force control assembly includes a voice coil motor, a guide assembly, and a six-dimensional force sensor 32. The six-dimensional force sensor 32 is mounted on one side of the connecting plate 9. The upper end of the guide assembly is connected to the connecting plate, and the lower end is connected to the lower mounting plate. The main shaft passes through the voice coil motor. The upper end of the voice coil motor is mounted to the connecting plate, and the lower end of the voice coil motor is connected to the lower mounting plate. The voice coil motor has a mover 11 and a stator 10. The guide assembly includes an optical shaft and a linear bearing. The linear bearing is mounted on the lower side of the connecting plate 9. The upper end of the optical shaft is movably inserted into the linear bearing, and the lower end of the optical shaft is connected to the lower mounting plate by screws. A shaft end baffle is provided on the connecting plate opposite the position of the linear bearing to limit the movement stroke of the optical shaft.

[0051] A voice coil motor is a linear motor whose output thrust can be controlled by adjusting the supply current. The output thrust is the current value multiplied by the motor coefficient. The stator 10 of the voice coil motor is positioned using the lower end face of the connector 9 and is fixed to the connector 9 with screws. The mover 11 of the voice coil motor is positioned using the upper end face of the lower mounting plate 12 and is fixed to the lower mounting plate 12 with screws.

[0052] Two optical axes are provided, located on both sides of the main shaft, namely optical axis 27 and optical axis 29. The lower ends of both optical axes are fixedly connected to the lower mounting plate 12, and linear bearings 28 and 30 pass through them respectively. The upper end of optical axis 27 is fixedly connected to the shaft end retaining ring 26, and optical axis 29 corresponds to the shaft end retaining ring 31. The cooperation between the optical axis and the linear bearing ensures that the movement between the voice coil motor mover 11 and stator 10 can only be along their axial direction, and the movable stroke can be limited by the length of the optical axis. Because the constant force control component has a degree of freedom along the axis of the main shaft 4 in the overall structure, when the polishing component disk contacts the workpiece, it can transmit the axial polishing force to the workpiece.

[0053] The motion decoupling assembly includes a bearing housing 13, a retaining ring 14, a double-row angular contact ball bearing 15, and a spline sleeve 19. The bearing housing 13 is connected to the lower mounting plate 12. The double-row angular contact ball bearing 15 is installed in the bearing housing 13 and secured by the retaining ring 14. The spline sleeve 19 is installed in the bearing housing 13 and has a ball spline 20. The ball spline 20 is assembled and connected to the spindle 4 and has the characteristics of being circumferentially fixed and axially movable relative to each other, ensuring the stability of the spindle rotation process.

[0054] The polishing disc assembly includes a polishing disc mounting component 16, a lower coupling 18, and a polishing disc 17. The upper end of the polishing disc mounting component 16 extends into the bearing housing 13 and is connected to the main shaft 4. One end of the lower coupling 18 is connected to the polishing disc mounting component 16, and the other end of the lower coupling 18 is connected to the polishing disc 17.

[0055] The inner circumferential surface of the bearing housing 13 transitions with the outer circumferential surface of the double-row angular contact ball bearing 15 to ensure that the double-row angular contact ball bearing 15 and the bearing housing 13 will not move axially or rotate circumferentially during operation, and is further secured by a retaining ring 14 installed in the internal groove of the bearing housing 13; the outer circumferential surface of the spline sleeve 19 transitions with the inner circumferential surface of the double-row angular contact ball bearing 15, and the upper end face of the polishing disc mounting part 16 clamps the upper and lower end faces of the inner ring of the double-row angular contact ball bearing 15 with the flange of the spline sleeve 19, thus achieving a fixed connection between the spline sleeve 19 and the polishing disc mounting part 16 relative to the inner ring of the double-row angular contact ball bearing 15; the inner circumferential surface of the spline sleeve 19 and the ball spline 2 The outer circumference of the two parts is fitted together, and the flanges of the two parts are fixedly connected by screws, so that the rotational motion and the movement along the axis of the two parts can be synchronized. The motor 1 transmits the rotational motion of the ball spline 20 through the main shaft 4, and the ball spline 20 then transmits the motion directly to the polishing disc mounting part 16 through the spline sleeve 19. The voice coil motor transmits the axial polishing force to the bearing housing 13 through the lower mounting plate 12. The bearing housing 13 transmits the force to the spline sleeve 19 through the inner and outer rings of the double-row angular contact bearing, and then the spline sleeve 19 transmits the force directly to the polishing disc mounting part 16. Although the spline sleeve 19 can also transmit the force to the ball spline 20, since the ball spline 20 and the main shaft 4 have no axial movement restriction, it will not affect the main shaft 4.

[0056] The output shaft of motor 1 transmits motion to the main shaft 4 via the upper coupling 3. The main shaft 4 then transmits the motion to the spline sleeve 19 via the ball spline 20. The spline sleeve 19 is fixedly connected to the polishing disc mounting part 16, and thus transmits the motion to the polishing disc 17 via the polishing disc mounting part 16 and the lower coupling 18. The axial polishing force transmission process is as follows: the voice coil motor is energized to obtain thrust, which is transmitted to the bearing housing 13 via the lower mounting plate 12. The bearing housing 13 transmits the thrust to the spline sleeve 19, and then to the polishing disc 17.

[0057] Because the process of the robotic polishing tool approaching the workpiece is also a particularly important issue, this invention mainly considers only the polishing process that has already been initiated. The workflow of this invention is as follows: First, a suitable polishing disc size is selected based on the surface curvature variation of the workpiece, and the end effector has already made contact with the workpiece, where the entire workpiece's path points have been pre-planned.

[0058] Normal tracking process: When the center of the grinding disc 17 has reached the first path point, the first laser ranging sensor 7, the second laser ranging sensor 22, the third laser ranging sensor 24, and the linear encoder 341 in the test assembly will each measure the coordinates of a point, and then convert these four points to the robot's base coordinate system. Since there are only four coordinate values, the expression of formula (1) cannot be used directly. Therefore, these four points are substituted into the three simplified versions of formula (1) mentioned above, as follows:

[0059]

[0060] The unknown coefficients in each term are obtained, and then a normal vector at the path point can be obtained for each expression. The average of the three normal vectors is then calculated to obtain the normal vector of the first path point. When the normal vector of the first path point is found, the robot adjusts the attitude of the end effector so that the axis of the main spindle 4 coincides with it, and then polishes for a period of time (the length of the delay time is determined by the process). The robot controls the center point of the polishing disc 17 of the end effector to move to the second path point. The laser range sensor 7, laser range sensor 22, laser range sensor 24 and linear encoder 341 in the test component will each measure a point coordinate. These four points are then converted to the robot's base coordinate system. At this time, with the addition of the measurement data, there are a total of eight spatial coordinates. However, formula (1) only has six unknown coefficients. Therefore, the least squares method is used to find a set of optimal coefficients using the coordinates of these eight points. Then, the normal vector of the second path point is obtained using the known expression (2) mentioned above. Then, the robot adjusts the attitude of the end effector so that the axis of the main spindle 4 coincides with it, and then delays for a period of time. The normal tracing of subsequent path points is done in the same way. Each time, the coordinate data of the points used is the spatial coordinates of eight points, which are the current measurement data and the previous measurement data.

[0061] Constant force control process: Constant force control is required throughout the polishing process. Before polishing, the six-dimensional force sensor 32 undergoes gravity compensation for the end effector, so the data measured by the six-dimensional force sensor 32 represents the contact force between the polishing disc 17 and the workpiece. At the start of polishing, a desired polishing force is given by supplying current to the voice coil motor, which transmits the current to the polishing disc 17 via the lower mounting plate 12, etc. The polishing disc 17 then transmits the axial polishing force to the workpiece. The six-dimensional force sensor 32 observes the axial polishing force at a certain frequency. When the measured force deviates from the expected axial polishing force, the magnitude of the axial polishing force can be controlled by adjusting the current to maintain stability. The constant force control process is a continuous process of detection and adjustment. During the polishing process, the voice coil motor stator 10 and the voice coil motor mover 11 move axially continuously. The midpoint of the stroke is taken as the zero point, and a threshold equal to 1 / 4 of the stroke is set at the top and bottom. The stroke position can be detected by the data collected by the linear encoder 341. When the stroke exceeds the upper and lower thresholds, the robot will adjust it to return the stroke to the midpoint. When the thresholds are not exceeded, the robot is only responsible for forward movement and posture adjustment.

[0062] Through the above structure and operation, precise tracking of the normal direction during workpiece machining can be achieved.

[0063] It should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. However, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A robotically force-controlled polishing end effector that can track a normal to a workpiece, characterized by, The system includes a rotating assembly, a measuring assembly, a constant force control assembly, a motion decoupling assembly, and a polishing disc assembly. The rotating assembly is mounted on a connecting plate. The measuring assembly includes a laser ranging assembly and an encoder assembly. The laser ranging assembly is mounted on the upper side of the connecting plate, and the encoder assembly is mounted on the lower side. The constant force control assembly is connected to the connecting plate. A lower mounting plate is mounted on the upper part of the motion decoupling assembly. The output end of the rotating assembly passes through the constant force control assembly and the lower mounting plate, and then connects to the polishing disc assembly via the motion decoupling assembly. The laser ranging assembly and the encoder assembly together constitute measurements in four different directions. The encoder assembly includes an encoder... The device comprises an encoder component and a grating component. The encoder component includes a linear encoder, an encoder mounting plate, and a slider. The slider is mounted inside the encoder mounting plate. The linear encoder is connected to the encoder mounting plate by screws. The slider is located between the linear encoder and the encoder mounting plate. The encoder mounting plate is mounted and connected to a connecting plate. The grating component includes a slide rail, a grating plate, grating paper, and a grating mounting base. The bottom of the grating plate is mounted on the grating mounting base. The grating paper is attached to the grating plate. The slide rail is located on one side of the grating plate. The slide rail is inserted between the slider and the linear encoder and is movably engaged with the slider. The grating mounting base is mounted on the lower mounting plate.

2. The robot force-controlled, polishing end-effector of trackable workpiece normal according to claim 1, characterized in that, The rotating assembly includes a motor, a motor bracket, an upper coupling, a main shaft, and a seated bearing. The motor is mounted on a connecting plate via the motor bracket, the motor's output shaft is connected to the main shaft via the upper coupling, the bearing is mounted on the connecting plate, and the main shaft passes through the seated bearing.

3. The robot force-controlled, polishing end-effector of claim 2, wherein, The laser ranging assembly includes a sensor mounting plate, a first laser ranging sensor, a second laser ranging sensor, and a third laser ranging sensor. The first laser ranging sensor, the second laser ranging sensor, and the third laser ranging sensor are respectively mounted on the sensor mounting plate via mounting brackets. The first laser ranging sensor, the second laser ranging sensor, and the third laser ranging sensor are distributed at 90-degree intervals around the circumference of the sensor mounting plate.

4. The robot force-controlled, buffing end effector of trackable workpiece normal according to claim 3, characterized in that, The sensor mounting plate is provided with three mounting seats. The lower part of the mounting bracket is locked to the lower part of the mounting seat by screws. The upper part of the mounting bracket is provided with an adjustment slot, into which a bolt is inserted and fixedly connected to the mounting seat.

5. The robot force-controlled, polishing end-effector of trackable workpiece normal according to claim 4, characterized in that, The grating plate has a groove, and the grating paper is attached in the groove. The groove and the slide rail extend in the same direction.

6. The robot force-controlled, polishing end-effector of trackable workpiece normal according to claim 5, characterized in that, The constant force control component includes a voice coil motor, a guide assembly, and a six-dimensional force sensor. The six-dimensional force sensor is mounted on one side of the connecting plate. The upper end of the guide assembly is connected to the connecting plate, and the lower end is connected to the lower mounting plate. The main shaft passes through the voice coil motor. The upper end of the voice coil motor is mounted to the connecting plate, and the lower end of the voice coil motor is connected to the lower mounting plate. The voice coil motor has a mover and a stator.

7. The robot force-controlled, polishing end-effector of trackable workpiece normal according to claim 6, characterized in that, The guide assembly includes an optical axis and a linear bearing. The linear bearing is installed on the lower side of the connecting plate. The upper end of the optical axis is movably inserted into the linear bearing. The lower end of the optical axis is connected to the lower mounting plate by screws. A shaft end baffle is provided on the connecting plate directly opposite the position of the linear bearing.

8. The robot force-controlled, polishing end-effector of trackable workpiece normal according to claim 7, characterized in that, The motion decoupling assembly includes a bearing housing, a retaining ring, a double-row angular contact ball bearing, and a spline sleeve. The bearing housing is connected to the lower mounting plate. The double-row angular contact ball bearing is installed in the bearing housing and secured by the retaining ring. The spline sleeve is installed in the bearing housing and has ball splines in it, which are assembled and connected to the spindle.

9. The robot force-controlled, polishing end-effector of trackable workpiece normal according to claim 8, characterized in that, The polishing disc assembly includes a polishing disc mounting component, a lower coupling, and a polishing disc. The upper end of the polishing disc mounting component extends into the bearing housing and is connected to the main shaft. One end of the lower coupling is connected to the polishing disc mounting component, and the other end of the lower coupling is connected to the polishing disc.

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