A robot positioning compensation system based on real-time feedback of mechanical arm end coordinates

Abstract

The application provides a robot positioning compensation system based on real-time feedback of mechanical arm end coordinates, the robot comprising a mechanical arm and an end effector, the end effector being arranged at the end of the mechanical arm; the positioning compensation system comprising a target ball, a laser tracker, a computer and a controller, the target ball being arranged on the end effector, a closed-loop control system being formed among the mechanical arm, the laser tracker, the computer and the controller; the laser tracker being used for detecting the coordinates of the target ball in real time and sending the coordinates to the computer, the computer being used for converting the coordinates of the target ball into the spatial coordinates of the mechanical arm and sending the spatial coordinates to the controller; the controller being used for generating a corresponding compensation signal according to the spatial coordinates and sending the compensation signal to the mechanical arm, and the mechanical arm moving to a set position according to the compensation signal.

Description

Technical Field

[0001] This invention relates to the field of nanometer measurement technology, and in particular to a robot positioning compensation system based on real-time feedback of the coordinates of the end effector of a robotic arm. Background Technology

[0002] Large-aperture optical components are core components of many technologies and symbols of national strength. They are currently widely used in precision optical systems such as lithography machines, remote sensing satellites, space telescopes, defense optical tracking and search devices, and laser fusion. They are the core of high-performance optical systems and the crown jewel of the precision optical manufacturing field.

[0003] Although optical components are becoming increasingly larger in diameter and more complex in shape, the requirements for surface control precision are also increasing. The surface control precision of optical components in the aforementioned high-end applications is required to reach the picometer level. The surface roughness, flatness, and defects of large-diameter optical components are important parameters that must be detected during the grinding and polishing process. Micrometer and submicrometer defects need to be detected and addressed in a timely manner during processing; otherwise, the abnormal energy accumulation of residual defects may damage the device or even the entire equipment.

[0004] Atomic force microscopy (AFM) is currently the only tool capable of performing picometer-precision three-dimensional topography and shape measurements in submicron surface regions, making it a key instrument for calibrating OCD, CD-SEM, and other online equipment. Currently, the probe of the AFM is primarily mounted at the end of a robotic arm, which moves the probe along a planned path above the optical elements. However, due to potential positioning errors in the robotic arm, the movement path may deviate from the planned path, potentially causing the probe to collide with and damage the optical elements.

[0005] Therefore, how to improve the positioning accuracy of robotic arms has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a robot positioning compensation system based on real-time feedback of end-effector coordinates. The robot includes a robotic arm and an end effector, with the end effector disposed at the end of the robotic arm. The positioning compensation system includes a target ball, a laser tracker, a computer, and a controller. The target ball is mounted on the end effector, and the robotic arm, laser tracker, computer, and controller form a closed-loop control system. The laser tracker detects the coordinates of the target ball in real time and sends these coordinates to the computer. The computer converts the coordinates of the target ball into spatial coordinates of the robotic arm and sends these spatial coordinates to the controller. The controller generates a corresponding compensation signal based on the spatial coordinates and sends the compensation signal to the robotic arm. The robotic arm moves to a set position based on the compensation signal.

[0007] Optionally, the coordinates of the target ball detected in real time by the laser tracker are obtained in the coordinate system of the laser tracker.

[0008] Optionally, the coordinate system of the laser tracker is based on the center of the tracking head of the laser tracker as the origin, the 0 reading direction on the dial as the x-axis, the upward direction of the normal to the dial plane as the z-axis, and the y-axis is determined by a right-hand coordinate system.

[0009] Optionally, the coordinates of the target ball detected in real time by the laser tracker are three-dimensional coordinates.

[0010] Optionally, the end effector of the robotic arm is connected to the end effector via a three-dimensional nano-damping gimbal, which is used to detect and counteract the vibration of the end effector, the vibration being a characterization of the relative vibration between the end effector and the sample.

[0011] Optionally, the vibration damping gimbal includes an accelerometer, an XYZ three-degree-of-freedom drive unit, and a gimbal controller. The gimbal controller is electrically connected to the accelerometer and the XYZ three-degree-of-freedom drive unit. The accelerometer is integrated on the end effector and is used to detect the XYZ three-axis displacement of the end effector, obtain a vibration signal, and send the vibration signal to the gimbal controller. The gimbal controller generates a corresponding drive signal based on the vibration signal detected by the accelerometer and sends it to the XYZ three-degree-of-freedom drive unit. The XYZ three-degree-of-freedom drive unit is also mechanically connected to the end effector and the end of the robotic arm, and is used to drive the end effector to generate a compensating motion based on the received drive signal. The compensating motion is used to counteract the vibration.

[0012] Optionally, the XYZ three-degree-of-freedom drive unit includes a first connector, an XY-axis drive module, an intermediate platform, a Z-axis drive module, and a second connector. The first connector is fixedly connected to the end effector of the robotic arm. The first connector is connected to the intermediate platform through the XY-axis drive module, which drives the intermediate platform to perform vibration compensation motion in the XY direction. The intermediate platform is connected to the second connector through the Z-axis drive module, which drives the second connector to perform vibration compensation motion in the Z direction. The second connector is fixedly connected to the end effector.

[0013] Optionally, the XY-direction drive module includes at least two X-direction flexible hinges and at least one X-direction piezoelectric ceramic. The two sides of the intermediate platform are respectively connected to the first connector in the X direction through at least one of the X-direction flexible hinges. The X-direction piezoelectric ceramic is used to drive the intermediate platform to perform vibration compensation motion in the X direction.

[0014] Optionally, the XY-direction drive module further includes at least two Y-direction flexible hinges and at least one Y-direction piezoelectric ceramic. The two sides of the intermediate platform are respectively connected to the first connector in the Y direction through at least one of the Y-direction flexible hinges. The Y-direction piezoelectric ceramic is used to drive the intermediate platform to perform vibration compensation motion in the Y direction.

[0015] Optionally, the end effector is an AFM probe or a white light interferometer measuring head.

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

[0017] 1. This invention improves the positioning accuracy of the robot by establishing a closed-loop control system between the laser tracker and the end effector of the robotic arm, and by controlling the real-time feedback compensation of the control system.

[0018] 2. The present invention sets a three-dimensional nano-vibration damping gimbal between the end of the robotic arm and the end effector. The three-dimensional nano-vibration damping gimbal is used to detect and counteract the vibration of the end effector. The vibration characterizes the relative vibration between the end effector and the sample.

[0019] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of a robot positioning compensation system based on real-time feedback of the end-effector coordinates of a robotic arm, provided in an embodiment of the present invention.

[0022] Figure 2 This is a schematic diagram illustrating the working principle of a laser tracker according to an embodiment of the present invention.

[0023] Figure 3 A schematic diagram of a structure for vibration reduction between the end effector and the end effector of a robotic arm, provided in an embodiment of the present invention, using a three-dimensional nano-vibration damping gimbal. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The terms "first," "second," "third," "fourth," etc. (if present) in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus. The terms "above" and "over," and any variations thereof, are intended to describe positional relationships and do not imply direct contact between the described objects.

[0026] As described in the background section, atomic force microscopy (AFM) is currently the only tool capable of performing picometer-precision three-dimensional topography and shape measurements in submicron surface regions, making it a key instrument for calibrating OCD, CD-SEM, and other online equipment. Currently, the probe of the atomic force microscope is primarily mounted at the end of a robotic arm, which moves the probe along a planned path above the optical elements. However, due to potential positioning errors in the robotic arm, the arm's path may deviate from the planned path, potentially causing the probe to collide with the optical elements and damage them.

[0027] Therefore, how to improve the positioning accuracy of robotic arms has become a technical problem that urgently needs to be solved by those skilled in the art.

[0028] To solve the above technical problems, please refer to Figures 1 to 3 An embodiment of the present invention provides a robot positioning compensation system based on real-time feedback of the end-effector coordinates of a robotic arm. The robot includes a robotic arm 1 and an end effector 5, wherein the end effector 5 is disposed at the end 11 of the robotic arm 1. The positioning compensation system includes a target ball, a laser tracker 2, a computer 3, and a controller 4. The target ball is disposed on the end effector 5, and a closed-loop control system is formed between the robotic arm 1, the laser tracker 2, the computer 3, and the controller 4.

[0029] Specifically, controller 4 is electrically connected to robotic arm 1, and computer 3 is communicatively connected to controller 4 and laser tracker 2 respectively.

[0030] The laser tracker 2 is used to detect the coordinates of the target ball in real time and send the coordinates to the computer 3. The computer 3 is used to convert the coordinates of the target ball into the spatial coordinates of the robotic arm 1 and send the spatial coordinates to the controller 4. The controller 4 is used to generate a corresponding compensation signal based on the spatial coordinates and send the compensation signal to the robotic arm 1. The robotic arm 1 moves to a set position based on the compensation signal.

[0031] This invention improves the robot's positioning accuracy by forming a closed-loop control system among the robotic arm 1, laser tracker 2, computer 3, and controller 4, thereby achieving real-time feedback compensation of the control system.

[0032] In this embodiment, the laser tracker 2 includes a tracking head 21. When tracking and measuring the target ball on the end effector 5, the laser emitted by the tracking head 21 hits the target ball and is reflected back to the tracking head 21. When the target ball moves, the tracking head 21 adjusts the beam direction to align with the target ball. At the same time, the returned beam is received by the tracking head 21 and used to calculate the spatial position of the target ball.

[0033] In summary, the laser tracker 2 determines the spatial coordinates of the end effector 5 by measuring the position of a target ball placed on it. The laser tracker 2 can directly measure the three-dimensional coordinates of a point in space, obtained within its coordinate system. This coordinate system is defined as follows: with the center of the tracking head 21 as the origin, the 0-reading direction on the scale as the x-axis, the upward direction of the normal to the scale plane as the z-axis, and the y-axis determined by the right-hand coordinate system rule. When the target ball leaves the reference position (the distance from the reference position to the center of the laser tracker 2 is known) and moves in space, the laser tracker 2 automatically tracks the target ball, simultaneously recording the interferometric ranging value L and the angle values ​​α and β on the vertical and horizontal scales, thus obtaining the three-dimensional rectangular coordinates (X, Y, Z) of the point.

[0034] The laser tracker 2 can not only obtain the position of the end effector 11 of the robotic arm 1, but also the coordinate transformation matrix between the robotic arm 1 and the laser tracker 2. Therefore, the coordinate information measured by the laser tracker 2 can be transformed into the base coordinate system of the robotic arm 1.

[0035] With the development of modern industry, optical components are becoming increasingly larger, with dimensions exceeding meters. In-situ measurement of ultra-large samples is a pressing need in the industry. However, existing atomic force microscopy (AFM) systems can only measure small samples (less than 40*40cm). To inspect even larger samples, the mechanical loop between the probe and the sample stage needs to be enlarged. Enlarging the mechanical loop is susceptible to ground vibrations and environmental noise, leading to complex vibrations and relative instability between the probe and the sample stage, resulting in more noise in the images. Therefore, how to detect and eliminate probe vibration has become another technical problem that urgently needs to be solved by those skilled in the art.

[0036] To solve the above-mentioned technical problems, in one embodiment of the present invention, the end effector 11 of the robotic arm 1 is further connected to the end effector 5 by a three-dimensional nano-vibration damping gimbal 6. The three-dimensional nano-vibration damping gimbal 6 is used to detect and counteract the vibration of the end effector 5, and the vibration characterizes the relative vibration between the end effector 5 and the sample 7.

[0037] Specifically, the vibration damping gimbal 6 includes an accelerometer 67, an XYZ three-degree-of-freedom drive unit, and a gimbal controller 66. The gimbal controller 66 is electrically connected to the accelerometer 67 and the XYZ three-degree-of-freedom drive unit. The accelerometer 67 is integrated on the end effector 5 and is used to detect the XYZ three-axis displacement of the end effector 5, obtain a vibration signal, and send the vibration signal to the gimbal controller 66. The gimbal controller 66 generates a corresponding drive signal based on the vibration signal detected by the accelerometer 67 and sends it to the XYZ three-degree-of-freedom drive unit. The XYZ three-degree-of-freedom drive unit is also mechanically connected to the end effector 5 and the end of the robotic arm 1, respectively, and is used to drive the end effector 5 to generate a compensating motion based on the received drive signal. The compensating motion is used to counteract the vibration.

[0038] In this embodiment, the robot and sample 7 are mechanically connected.

[0039] A three-dimensional nano-vibration damping gimbal 6 is fixed to the end effector 11 of the robotic arm 1, and an end effector 5 is fixed to the three-dimensional nano-vibration damping gimbal 6. The end effector 5 is used to scan and image or process the test area of ​​the sample 7. The three-dimensional nano-vibration damping gimbal 6 is used to detect and counteract the vibration of the end effector 5, which characterizes the relative vibration between the end effector 5 and the sample 7.

[0040] Specifically, the XYZ three-degree-of-freedom drive unit includes a first connector 61, an XY-axis drive module 62, an intermediate platform 63, a Z-axis drive module 64, and a second connector 65. The first connector 61 is fixedly connected to the end effector 11 of the robotic arm 1. The first connector 61 is connected to the intermediate platform 63 through the XY-axis drive module 62, which drives the intermediate platform 63 to perform XY-axis vibration compensation motion. The intermediate platform 63 is connected to the second connector 65 through the Z-axis drive module 64, which drives the second connector 65 to perform Z-axis vibration compensation motion. The second connector 65 is fixedly connected to the end effector 5.

[0041] In this embodiment, since both the X and Y directions are located on a horizontal plane, the XY direction drive module 62 can integrate the first connector 61, the XY direction drive module 62, and the intermediate platform 63 into one unit.

[0042] Furthermore, the XY-direction drive module 62 includes at least two X-direction flexible hinges and at least one X-direction piezoelectric ceramic. The two sides of the intermediate platform 63 are respectively connected to the first connector 61 in the X direction through at least one of the X-direction flexible hinges. The X-direction piezoelectric ceramic is used to drive the intermediate platform 63 to perform X-direction vibration compensation movement, thereby driving the end effector 5 to perform X-direction vibration compensation movement.

[0043] In this invention, X-axis piezoelectric ceramics can be provided on one side of the intermediate platform 63, or X-axis piezoelectric ceramics can be provided on both sides of the intermediate platform 63. In the vibration supplementary motion where X-axis piezoelectric ceramics are provided on both sides of the intermediate platform 63, if the X-axis piezoelectric ceramic on one side retracts, then the X-axis piezoelectric ceramic on the other side extends.

[0044] The XY drive module 62 further includes at least two Y-axis flexible hinges and at least one Y-axis piezoelectric ceramic. The two sides of the intermediate platform 63 are respectively connected to the first connector 61 in the Y direction through at least one of the Y-axis flexible hinges. The Y-axis piezoelectric ceramic is used to drive the intermediate platform 63 to perform vibration compensation movement in the Y direction, thereby driving the end effector 5 to perform vibration compensation movement in the Y direction.

[0045] In this invention, Y-axis piezoelectric ceramics can be provided on one side of the intermediate platform 63, or Y-axis piezoelectric ceramics can be provided on both sides of the intermediate platform 63. In the vibration supplementary motion where Y-axis piezoelectric ceramics are provided on both sides of the intermediate platform 63, if the Y-axis piezoelectric ceramic on one side retracts, then the Y-axis piezoelectric ceramic on the other side extends.

[0046] The function of the first connector 61 is to fix the vibration damping gimbal 6 to the end of the robotic arm 1. As one embodiment, the first connector 61 is a frame structure with a bottom at the top, an opening at the bottom, and a surrounding edge on the side. The upper end of the first connector 61 is fixedly connected to the end of the robotic arm 1. The intermediate platform 63 is connected to the frame structure through an XY-direction drive module 62. The side of the frame structure is provided with an X-direction application port for applying preload to the X-direction piezoelectric ceramic and a Y-direction application port for applying preload to the Y-direction piezoelectric ceramic.

[0047] The X-axis piezoelectric ceramic is preloaded through the X-axis preload bolt passing through the X-axis application port to drive the intermediate platform 63. The Y-axis piezoelectric ceramic is preloaded through the Y-axis preload bolt passing through the Y-axis application port to drive the intermediate platform 63.

[0048] The Z-axis drive module 64 includes at least one Z-axis flexible hinge and at least one Z-axis piezoelectric ceramic. The intermediate platform 63 is connected to the second connector 65 in the Z-axis direction through at least one of the Z-axis flexible hinges. The Z-axis piezoelectric ceramic is used to drive the second connector 65 to perform vibration compensation movement in the Z-axis direction.

[0049] In this invention, the accelerometer 67 is an XYZ triaxial accelerometer. The accelerometer 67 can be mounted on the end effector 5 or on the second connector 65; this invention does not impose any specific limitations on this.

[0050] The end effector 5 can be a probe, or it can be a nanoprobe used by a mask repair robot to remove nanoparticles from the mask surface, a processing head in an electron beam lithography machine, a processing head in scanning probe micromachining, a measuring head of a white light interferometer, etc. The present invention does not impose specific limitations on this.

[0051] Please refer to the figure. In this embodiment, the end effector 5 is taken as an atomic force microscope (AFM) probe. The accelerometer 67 is used to detect the vibration of the AFM probe relative to the sample 7 and sends the vibration signal to the gimbal controller 66. The gimbal controller 66 generates a compensation signal based on the vibration signal detected by the accelerometer 67 and sends it to the XYZ three-degree-of-freedom drive unit. The three actuators of the XYZ three-degree-of-freedom drive unit (i.e., XYZ piezoelectric actuators, namely X-axis piezoelectric ceramics, Y-axis piezoelectric ceramics, and Z-axis piezoelectric ceramics, all of which are electrically connected to the gimbal controller 66) drive the AFM probe to perform compensating motion in the XYZ directions according to the received compensation signal. This compensating motion can eliminate the vibration of the AFM probe. Therefore, the accelerometer 67, actuators, and gimbal controller 66 provided by this invention can detect and eliminate the vibration of the AFM probe, solving the problem that the vibration of the AFM probe cannot be detected and canceled, thereby eliminating noise in scanning imaging.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A robot positioning compensation system based on real-time feedback of end-of-arm coordinates, the robot comprising an arm and an end effector, the end effector being disposed at the end of the arm; characterized by, The positioning compensation system includes a target ball, a laser tracker, a computer, and a controller. The target ball is mounted on the end effector. A closed-loop control system is formed between the robotic arm, the laser tracker, the computer, and the controller. The laser tracker is used to detect the coordinates of the target ball in real time and send the coordinates to the computer. The computer is used to convert the coordinates of the target ball into the spatial coordinates of the robotic arm and send the spatial coordinates to the controller. The controller is used to generate a corresponding compensation signal based on the spatial coordinates and send the compensation signal to the robotic arm. The robotic arm moves to a set position according to the compensation signal.

2. The robotic positioning compensation system of claim 1, wherein, The coordinates of the target ball detected in real time by the laser tracker are obtained in the coordinate system of the laser tracker.

3. The robotic positioning compensation system of claim 2, wherein, The coordinate system of the laser tracker is based on the center of the tracking head of the laser tracker as the origin, the 0 reading direction on the dial as the x-axis, the upward direction of the normal to the dial plane as the z-axis, and the y-axis is determined by a right-hand coordinate system.

4. The robotic positioning compensation system of claim 3, wherein, The laser tracker detects the target ball's coordinates in real time as three-dimensional coordinates.

5. The robotic positioning compensation system of claim 1, wherein, The end effector is connected to the robotic arm via a three-dimensional nano-vibration damping gimbal. The three-dimensional nano-vibration damping gimbal is used to detect and counteract the vibration of the end effector, which characterizes the relative vibration between the end effector and the sample.

6. The robotic positioning compensation system of claim 5, wherein, The vibration damping gimbal includes an accelerometer, an XYZ three-degree-of-freedom drive unit, and a gimbal controller. The gimbal controller is electrically connected to both the accelerometer and the XYZ three-degree-of-freedom drive unit. The accelerometer is integrated into the end effector and is used to detect the XYZ three-axis displacement of the end effector, obtain a vibration signal, and send the vibration signal to the gimbal controller. The gimbal controller generates a corresponding drive signal based on the vibration signal detected by the accelerometer and sends it to the XYZ three-degree-of-freedom drive unit. The XYZ three-degree-of-freedom drive unit is also mechanically connected to both the end effector and the end effector of the robotic arm, and is used to drive the end effector to generate a compensating motion based on the received drive signal. The compensating motion is used to counteract the vibration.

7. The robotic positioning compensation system of claim 6, wherein, The XYZ three-degree-of-freedom drive unit includes a first connector, an XY-axis drive module, an intermediate platform, a Z-axis drive module, and a second connector. The first connector is fixedly connected to the end effector of the robotic arm. The first connector is connected to the intermediate platform through the XY-axis drive module, which drives the intermediate platform to perform vibration compensation motion in the XY direction. The intermediate platform is connected to the second connector through the Z-axis drive module, which drives the second connector to perform vibration compensation motion in the Z direction. The second connector is fixedly connected to the end effector.

8. The robotic positioning compensation system of claim 7, wherein, The XY-direction drive module includes at least two X-direction flexible hinges and at least one X-direction piezoelectric ceramic. The two sides of the intermediate platform are respectively connected to the first connector in the X direction through at least one of the X-direction flexible hinges. The X-direction piezoelectric ceramic is used to drive the intermediate platform to perform vibration compensation motion in the X direction.

9. The robot positioning compensation system according to claim 7, characterized in that, The XY-direction drive module further includes at least two Y-direction flexible hinges and at least one Y-direction piezoelectric ceramic. The two sides of the intermediate platform are respectively connected to the first connector in the Y direction through at least one of the Y-direction flexible hinges. The Y-direction piezoelectric ceramic is used to drive the intermediate platform to perform vibration compensation motion in the Y direction.

10. The robotic positioning compensation system of claim 1, wherein, The end effector is an AFM probe or a white light interferometer measuring head.

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