A disturbance observer design for backlash compensation

摘要

Electromechanical systems usually have an innate backlash in their gear trains which is normally nonlinear and limits the performance of the system. In this paper, a disturbance observer is designed in order to estimate the properties of the backlash. Generally, such disturbance observers are designed with the inverse model of the nominal plant but since the backlash is an internal factor of the plant, its effect cannot be separated from the system output. In the proposed model, the plant is reconfigured to separate the effects of the backlash from the output, and a new type of disturbance observer is proposed to detect and compensate for the backlash in the remodelled plant. The suggested disturbance observer is applied to the knee joint of a humanoid robot. Using the proposed disturbance observer, it is shown that the backlash can be compensated for, and that the tracking error decreases in the knee pitch trajectory. Also, an error analysis of the input trajectory is carried out to verify the performance of the proposed disturbance observer and the validity of the proposed control scheme is discussed.