Nonlinear compliant actuators are being increasingly used in human-robot interaction scenarios due to their inherent flexibility. However, a limitation is that nonlinear hysteresis exists, which will degrade the force/torque tracking performance if the hysteresis is not modeled accurately. Moreover, the existing methods are difficult to deal with the multi-loop asymmetry hysteresis. In this work, we present a novel modeling method, in which the hysteresis curves are decoupled into nonlinear reference lines and symmetrical hysteresis loops. A hybrid hysteresis model based on power function and Maxwellslip model is then developed to fit the nonlinear reference lines and symmetrical hysteresis loops respectively. Experiments were conducted on a nonlinear compliant actuator and the results show that the root-mean-square-errors (RMSE) of the hysteresis model decreases by 24.4% when compared with the Maxwellslip based hysteresis model.

High-generation FPD (Flat Panel Display) glass substrates need to be carried by large clean transfer robot. Due to the space of the deposited glass box is limited, the distance between the two substrates is very small, this requires the sag amount of the robot fork must be controlled within a certain range. The traditional design is completed only in robot manufacturing stage by adding a shim to compensate for this distortion, but this method can only make the fork be compensated at a determined location, deformation at other locations may not be considered. A new solution to the dynamic compensation for the robot fork is proposed. By establishing the robot FEA model and mechanism accuracy model respectively, the synthetic dynamic error is then obtained. One can just change the mechanism accuracy through rational allocation of design tolerances of the robot links to minimize the dynamic error.