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CN-122008311-A - Universal actuating device for automatic grinding and polishing of robot and using method of universal actuating device

CN122008311ACN 122008311 ACN122008311 ACN 122008311ACN-122008311-A

Abstract

The invention discloses a universal actuating device for automatic grinding and polishing of a robot and a use method thereof, wherein the universal actuating device is detachably arranged between the tail end of a mechanical arm and an end effector and comprises a mechanical arm fixed end and a mechanical arm detachable connection; the manipulator fixing end is hinged with the remaining two connecting ends on the cross shaft through two other first bearings, two linear actuators are respectively and correspondingly arranged on one sides of the two fixing brackets, the fixing end of each linear actuator is connected with the corresponding fixing bracket, and the movable end is hinged with the manipulator fixing end through a second bearing. The universal actuating device can improve the adaptability to complex curved surfaces in the polishing process.

Inventors

  • YAN SIJIE
  • ZHENG QUAN
  • YANG ZEYUAN
  • WU YUANFEI

Assignees

  • 华中科技大学
  • 华中科技大学无锡研究院

Dates

Publication Date
20260512
Application Date
20251225

Claims (15)

  1. 1. The universal actuating device for automatic grinding and polishing of the robot is detachably arranged between the tail end of a mechanical arm (8) and an end effector (9) and is characterized by comprising a mechanical arm fixed end (1), two fixed brackets (2), two linear effectors (3), a cross shaft (4), four first bearings (5), an effector fixed end (6) and two second bearings (7); the mechanical arm fixed end (1) is detachably connected with the mechanical arm (8); the actuator fixed end (6) is detachably connected with the end effector (9); the cross shaft (4) is in a cross shape as a whole and is provided with four connecting ends; One end of each of the two fixing brackets (2) is fixedly connected with the fixed end (1) of the mechanical arm, and the other end of each of the two fixing brackets is hinged with two connecting ends which are oppositely arranged on the cross shaft (4) through a first bearing (5); the actuator fixed end (6) is hinged with the two remaining connecting ends on the cross shaft (4) through the other two first bearings (5): The two linear actuators (3) are respectively and correspondingly arranged on one sides of the two fixed supports (2), the fixed end of each linear actuator (3) is connected with the corresponding fixed support (2), and the movable end is hinged with the actuator fixed end (6) through one second bearing (7).
  2. 2. The universal actuation device according to claim 1, characterized in that the first bearing (5) is a deep groove ball bearing and the second bearing (7) is a fish eye bearing.
  3. 3. The universal actuating device according to claim 1 or 2, wherein a first clamping seat (61) is arranged on the actuator fixing end (6), two symmetrical connecting lug plates (61 a) are arranged on one side of the first clamping seat (61), the connecting lug plates (61 a) are in one-to-one correspondence with the linear actuator (3), and a through hole for connecting with the second bearing (7) is formed in one end, facing the linear actuator (3), of the connecting lug plates (61 a).
  4. 4. A universal actuating device according to claim 3, wherein the fixed end (6) of the actuator is provided with a second clamping seat (62), one side of the second clamping seat (62) is provided with two symmetrical connecting lifting lugs (62 a), and the two connecting lifting lugs (62 a) are respectively connected with two ends of the cross shaft (4) through a first bearing (5).
  5. 5. The universal actuating device according to claim 4, wherein the central axes of the mechanical arm fixing end (1), the actuator fixing end (6), the first clamping seat (61) and the second clamping seat (62) are on the same straight line, and the two straight line actuators are symmetrically arranged by taking the central axis of the first clamping seat (61) as a symmetrical axis.
  6. 6. The universal actuating device according to claim 1 or 2, wherein the fixing support (2) is provided with a plurality of hollow structures, and the hollow structures of the fixing support (2) are rectangular or oblong through holes.
  7. 7. The universal actuating device according to claim 1 or 2, characterized in that one side of the fixed bracket (2) is provided with at least two hoops (21) along its length direction, the hoops (21) being connected with the corresponding fixed ends of the linear actuators (3).
  8. 8. A method of using a universal actuation device for robotic automated polishing, implemented using a universal actuation device according to any one of claims 1-7, comprising the steps of: S1, taking the geometric center of a cross shaft (4) as the origin of a basic coordinate system, establishing a virtual cutting ellipsoid at the tool center point of a polishing head of an end effector (9) contacted with a workpiece, defining anisotropic impedance characteristics of the ellipsoid in tangential and normal directions, and mapping physical push rod movements of the linear effector (3) into surface manifold changes of the virtual cutting ellipsoid; S2, acquiring workpiece curvature data in front of a grinding and polishing path, and dynamically adjusting the rigidity coefficient and the damping coefficient of the virtual cutting ellipsoid according to curvature change rate; S3, calculating a generalized force vector required for maintaining dynamic balance of the virtual cutting ellipsoid in the current posture based on the mapping relation obtained in the step S1, decoupling and distributing the generalized force vector into axial thrust instructions required by the two linear actuators (3), and driving the two linear actuators (3) to perform differential expansion and contraction; S4, calculating the instantaneous cutting power density in the grinding and polishing process in real time, and when the instantaneous cutting power density is detected to be attenuated relative to a reference value, automatically increasing a normal contact pressure set value or controlling a linear actuator (3) to overlap a high-frequency flutter signal on the premise of keeping the geometric posture of the virtual cutting ellipsoid unchanged so as to compensate the material removal rate reduction caused by the abrasion of a grinding and polishing tool.
  9. 9. The method of use according to claim 8, wherein step S1 comprises the steps of: S11, establishing a transmission jacobian matrix based on a geometric transmission relation between the expansion speed of push rods of two linear actuators (3) and the angular speed of the rotation of an actuator fixed end (6) around a cross shaft (4), constructing a moment arm cross matrix by a position vector pointing to a tool center point from the geometric center of the cross shaft (4), obtaining a geometric jacobian matrix based on the transmission jacobian matrix and the moment arm cross matrix, thereby establishing the mapping of joint space velocity to the linear velocity of the tool center point in Cartesian space, and explicitly including the influence of tool length in a model; S12, setting dynamic response characteristics of a tool center point to external contact force in different directions through a target impedance model; s13, based on the virtual work principle, the net demand force at the tool center point is mapped to axial thrust commands of two linear actuators.
  10. 10. The method of claim 9, wherein the geometric jacobian matrix is: ; In the formula, A velocity vector of the tool center point under the base standard; Is joint coordinates; Is a transmission jacobian matrix; A moment arm cross matrix; a vector from the geometric center of the cross shaft to the center point of the tool; The mapping relation is as follows: ; In the formula, Axial thrust commands for the two linear actuators; transpose of a geometric jacobian matrix; Is a virtual stiffness matrix; the spatial coordinates where the tool center point should be in an ideal state; The actual physical coordinates of the tool center point at the current moment in the three-dimensional space are obtained; Is a virtual damping matrix; Is an external contact force.
  11. 11. The method of use according to claim 10, wherein step S2 comprises the steps of: S21, defining a planned grinding and polishing path as a continuous space curve taking arc length as a parameter, extracting point cloud data in the neighborhood of any prospective point on the path, fitting a local quadric surface by using a least square method, calculating the normal curvature of the local quadric surface along the tangential direction of the feeding speed, and carrying out convolution processing on the original normal curvature sequence along the path by a Gaussian weighted smoothing function to obtain a weighted average curvature subjected to smoothing processing; s22, based on the real-time feeding speed of the mechanical arm (8) and the path arc length from the current polishing head position to the next curvature mutation point which is visually identified, obtaining the expected collision time of the polishing head reaching the point; S23, obtaining a rheological adjustment factor based on the weighted average curvature and Sigmoid function, and dynamically adjusting the rigidity and damping of the virtual ellipsoid in the normal direction based on the rheological adjustment factor.
  12. 12. The method of claim 11, wherein the nominal normal stiffness and nominal normal damping are maintained when the path point curvature is less than a curvature threshold, wherein a rheological parameter correction command is generated and the normal stiffness is reduced and the normal damping is increased when the path point curvature is not less than the curvature threshold, and wherein the correction command is issued within a pre-actuation time window before the sanding head reaches the point of abrupt curvature.
  13. 13. Use according to claim 12, characterized in that the required kinetic compensation amount is calculated based on the lagrangian kinetic equation, superimposed on the thrust command and resulting in the final total output command: ; wherein: is the total output instruction; Is a gravity compensation term; Is a coriolis force term; is the joint speed; is a friction model.
  14. 14. The method of claim 13, wherein in step S4, the equation for calculating the instantaneous cutting power density is: ; ; wherein: Is the instantaneous cutting power density; Is the normal contact force; is the rotational linear velocity; Is the feed speed; Is the reference friction coefficient; Is the average power density; Is the time window length; based on the wear deviation index, two modes are used for compensation, wherein: And, at the same time, When (when) When the pressure gain compensation is triggered, the method specifically comprises the following steps: ; When (when) When in use, the micro-amplitude flutter compensation is triggered, which is specifically as follows: ; wherein: is the wear deviation index; as a reference energy consumption density; Is the current average power density; Is a passivation threshold; Is the corrected target pressure; is the nominal pressure; is the pressure gain coefficient; is the corrected position instruction; is a path position instruction; is the vibration amplitude; Is the dither frequency.
  15. 15. A computer readable storage medium, characterized in that the computer readable storage medium comprises a stored computer program which, when run by a processor, controls a device in which the storage medium is located to perform the use method according to any one of claims 8-14.

Description

Universal actuating device for automatic grinding and polishing of robot and using method of universal actuating device Technical Field The invention belongs to the technical field of robot automatic processing auxiliary equipment, and particularly relates to a universal actuating device for robot automatic grinding and polishing and a using method thereof. Background In the industrial automation process, the polishing operation system taking the industrial robot as a core gradually replaces the traditional manual polishing mode by virtue of the advantages of high operation stability, low labor intensity and the like, and becomes core equipment for realizing the fine treatment of the surface of the workpiece. Especially in the processing process of complex curved surface workpieces such as automobile body panel, aeroengine blades, precision die cavities and the like, the application of the robot grinding and polishing operation can obviously improve the surface quality of the workpieces and shorten the production period. However, in the actual operation process, the surface morphology of the workpiece to be polished is complex and various, and the workpiece to be polished not only comprises a regular plane structure, but also has a large number of curved surface structures with curvature change, so that the gesture adjusting capability of the end effector of the robot is strictly required. However, the rigid constraint of the traditional mechanical arm body structure and the kinematic control strategy thereof are limited, the end effector is difficult to dynamically adapt to geometric change of a curved surface in the actual operation process, so that the polishing head cannot always be tangential to a target curved surface in the polishing process, excessive or insufficient polishing of a local area is caused, and consistency of polishing thickness and surface quality are seriously affected. Aiming at the technical pain point with poor polishing consistency in the robot polishing operation, the prior art provides various improvement schemes. According to the technical scheme, a polishing path planning algorithm is preset in a robot control system, the motion track of a mechanical arm and the gesture parameters of an end effector are preset according to three-dimensional model data of a workpiece, the aim of realizing the attachment of a polishing head and the surface of the workpiece through accurate path control is fulfilled, and the technical scheme is characterized in that a force control sensor is adopted to feed back polishing pressure data, and the feeding amount of the mechanical arm is adjusted in real time to maintain the constant polishing pressure, so that polishing contact state fluctuation caused by curvature change of the surface of the workpiece is compensated. However, although the technology achieves a certain effect under a specific condition, the problem of poor polishing consistency in the process of polishing a curved surface can not be well solved, for example, a preset path planning algorithm depends on high-precision data of a three-dimensional model of a workpiece, when a machining error or surface morphology of the workpiece changes, a preset track deviates from the surface of the actual workpiece, the algorithm can not respond to dynamic interference occurring in the polishing process in real time, so that the polishing head is difficult to always maintain a tangential state with the curved surface, and secondly, a pressure adjusting scheme based on a force control sensor can only control the constant polishing pressure and can not directly adjust the attitude angle of the polishing head, and even if the pressure is constant, the contact angle deviation of the polishing head and the curved surface can still cause uneven polishing thickness for the curved surface with larger curvature change. Therefore, there is a need to develop an attitude adjustment auxiliary device adapted to the automated polishing operation of a robot, which can pointedly supplement and optimize the shortcomings of the prior art. Disclosure of Invention Aiming at the defects or improvement demands of the prior art, the invention provides the universal actuating device for the automatic grinding and polishing of the robot and the use method thereof, the self-adaptability and the consistency of the device to complex curved surfaces in the polishing process are obviously improved through the multi-degree-of-freedom connecting structure with the self-initiative adjusting capability, and meanwhile, the device is integrally designed in a modularized and detachable mode, so that the device is convenient to install, maintain and adapt to different operation scenes. In order to achieve the above object, according to one aspect of the present invention, there is provided a universal actuating device for robotic polishing, the universal actuating device being detachably disposed between a distal end of a robot arm and