Abstract:

In order to improve the absolute positioning accuracy of robots,an absolute positioning error model is constructed and an error compensation method is investigated.First,positioning errors are divided into geometrical parameter errors and compliance errors,and two models are respectively constructed for the two kinds of errors.The geometrical parameter errors are investigated on the basis of modified Denavit-Hartenberg kinematics,and the impact of the compliance errors is decoupled.Then,by taking into consideration the conversion error between the base coordinate system and the measurement one of robots,a geometrical parameter error model on the basis of relative positions is constructed.For the compliance errors,a model for joint 2 and joint 3 is constructed according to the construction features of robots,thus simplifying the calculation model of the compliance errors greatly.Finally,on the basis of the two kinds of error models,the error compensation method is proposed.The results of error compensation experiments show that average absolute positioning accuracy decreases from 1.173 to 0.158mm after calibration,which means that the proposed method can improve the absolute positioning accuracy of industrial robots effectively and extend its range of applications greatly.

Key words: industrial robot, absolute positioning accuracy, geometrical parameter error, compliance error, error compensation