Advances in Manufacturing ›› 2022, Vol. 10 ›› Issue (3): 397-410.doi: 10.1007/s40436-022-00400-6

• ARTICLES • Previous Articles    

Precision measurement and compensation of kinematic errors for industrial robots using artifact and machine learning

Ling-Bao Kong1, Yi Yu1   

  1. Shanghai Engineering Research Center of Ultra-precision Optical Manufacturing, Department of Optical Science and Engineering, Fudan University, Shanghai 200438, People's Republic of China
  • Received:2021-07-27 Revised:2022-01-24 Published:2022-09-08
  • Supported by:
    The National Key R&D Program of China (Grant No. 2017YFA0701200), Shanghai Science and Technology Committee Innovation Grant (Grant No. 19ZR1404600), Fudan University-CIOMP Joint Fund (Grant No. FC2020-006).

Abstract: Industrial robots are widely used in various areas owing to their greater degrees of freedom (DOFs) and larger operation space compared with traditional frame movement systems involving sliding and rotational stages. However, the geometrical transfer of joint kinematic errors and the relatively weak rigidity of industrial robots compared with frame movement systems decrease their absolute kinematic accuracy, thereby limiting their further application in ultraprecision manufacturing. This imposes a stringent requirement for improving the absolute kinematic accuracy of industrial robots in terms of the position and orientation of the robot arm end. Current measurement and compensation methods for industrial robots either require expensive measuring systems, producing positioning or orientation errors, or offer low measurement accuracy. Herein, a kinematic calibration method for an industrial robot using an artifact with a hybrid spherical and ellipsoid surface is proposed. A system with submicrometric precision for measuring the position and orientation of the robot arm end is developed using laser displacement sensors. Subsequently, a novel kinematic error compensating method involving both a residual learning algorithm and a neural network is proposed to compensate for nonlinear errors. A six-layer recurrent neural network (RNN) is designed to compensate for the kinematic nonlinear errors of a six-DOF industrial robot. The results validate the feasibility of the proposed method for measuring the kinematic errors of industrial robots, and the compensation method based on the RNN improves the accuracy via parameter fitting. Experimental studies show that the measuring system and compensation method can reduce motion errors by more than 30%. The present study provides a feasible and economic approach for measuring and improving the motion accuracy of an industrial robot at the submicrometric measurement level.

The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00400-6

Key words: Industrial robot, Kinematic error, Calibration, Machine learning, Recurrent neural network (RNN)