Abstract

Six degree-of-freedom (6-DOF) robotic manipulators have been increasingly adopted in various applications in industries due to various advantages, such as large operation space, more degrees of freedom, low cost, easy placement, and convenient programming. However, the robotic manipulator has the problem of insufficient stiffness due to the series structures, which will cause motion errors of the manipulator end. In this paper, taking a 6-DOF robotic manipulator as an example, forward and inverse kinematics models are established, and a new modeling method for the joint angle and space stiffness of the end of the manipulator is proposed, which can establish the composite stiffness model of joint link stiffness and joint stiffness. An error compensation model is subsequently established. The experimental results indicate that the proposed error compensation method can effectively reduce the end motion error of the robotic manipulator, and hence, the working performance and accuracy of the manipulator can be improved. The proposed research is helpful for extending the application of robotic manipulators in precision machining and measurement.

Highlights

  • Since the advent of robots in the 1940s, robot technology has constantly improved

  • This paper presents a method for stiffness modeling and error compensation for a 6-DOF cooperative robotic manipulator

  • The experimental results of this paper indicate that the error compensation method by the stiffness model based on joint stiffness and joint link stiffness is effective, which is significant for improving the spatial positioning accuracy of 6-DOF manipulator ends

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Summary

Introduction

After nearly a century of development, this technology has become an indispensable part of industries and production, especially in the field of precision machining and testing [1,2] Due to their series structure configuration, robotic manipulators have some problems, such as jitter and a relatively large end error caused by insufficient stiffness. Chen et al [18] proposed a calibration method of robot geometric parameters based on laser tracker measurement, which improved the absolute positioning accuracy of cooperative robots, the D-H parameter error of which is identified and compensated for. This paper presents a method for stiffness modeling and error compensation for a 6-DOF cooperative robotic manipulator This method can solve the problem of the complex stiffness model, in which it is difficult to establish joint stiffness and joint link stiffness based on the ANSYS finite element analysis method.

Kinematics Model for a 6-DOF Robotic Manipulator
Trajectory Compensation Based on Stiffness Modeling
Construction of the Jacobian Matrix
Flexibility Matrix
Motion Error Compensation by Correcting Joint Angle
Simulation Studies for a 6-DOF Manipulator
Solving Kinematics Model
Errors Caused by Connecting Rod Deformation
Flexibility Elements in Six Directions
Simulations of Error and Stiffness in PTP Trajectory
Experimental Studies
Concluding Remarks
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