Fast Solution Method for the Kinematics of Wrist Offset Robot Oriented to Wheel Hub Grinding and Polishing

doi:10.3901/JME.2022.14.126

Abstract

Abstract: In order to improve the quality and efficiency of wheel hub processing, a grinding and polishing robot with an offset wrist is designed. The wrist mechanism joint 5 can realize 360-degree rotation and improve the flexibility. But the robot does not meet Pieper's criteria. The inverse kinematics equations are complex, highly nonlinear, and strongly coupled, which makes it difficult to solve inverse kinematics effectively and accurately. To solve this problem, a fast solving method of inverse kinematics is proposed. This method constructs a new type of nonlinear equation, which simplifies the traditional six-joint angle solution to three-joint angle solution. Based on this equation, a two-step method from coarse to fine is proposed to solve inverse kinematics. The first step is to estimate the initial values of multiple sets of joint angles and select the initial values based on the current joint angles. It can avoid local optimal problems and improve the stability of the solution. The second step is to accurately solve all the joint angle values according to the initial values. For the multi-group solution problem when the 4 and 6 axes are collinear, the analytical solution of the special state of the robot is given. In terms of accuracy, efficiency, and multiple solution indicators, simulation experiments verify that the inverse kinematics algorithm meets the requirements of wheel hub grinding and polishing. Its effectiveness is further proved in the spoke processing path.

Key words: grinding and polishing robot, wrist offset, inverse kinematics, wheel hub processing, nonlinear equation

CLC Number:

TP242

LIU Zhiheng, ZHAO Lijun, LI Ruifeng, GE Lianzheng, XIA Yi, ZHU Kui. Fast Solution Method for the Kinematics of Wrist Offset Robot Oriented to Wheel Hub Grinding and Polishing[J]. Journal of Mechanical Engineering, 2022, 58(14): 126-136.

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