Effect of Hall Errors on Current and Rotor Position of Robot Joint Motors

This article investigates the impact of Hall errors on the speed, rotor position, and current of joint motors in robots, focusing on brushless dc torque motors. On introducing the sensing principle of the Hall sensor in the torque motor system, the influence of circumferential installation errors and axial offset errors on the rotor position and current of the motor is derived analytically on the basis of the Hall vector signals. The results show that the Hall errors generate rotor position errors characterized by the occurrence of specific harmonics with inherent deviations in rotor position, which in turn introduce the (2n - 1)th current harmonics. The study proceeds to conduct simulations for a comparative evaluation of the degrees of influence exerted by circumferential installation errors and by axial offset errors on the motor speed, rotor position, and current. These findings are then validated through experiments, wherein the characteristics of Hall errors' influence are elucidated via analysis of speed and current harmonics. This study provides a fresh methodology for analyzing errors in Hall sensors.