Real-time computation and parameter identification of torque-off sliding distance for elegant robot failure

Abstract

When the robot is stopped after failure occurs, the moving part of the robot will decelerate until stop. The traveling distance during deceleration is called torque-off sliding distance (TOSD), which should be computed in real time for operation safety. However, the real-time requirement excludes the commonly adopted, iteration-based computation methods. Besides, the varying parameters further challenges the accuracy of the computed TOSDs. In this paper, we derive an analytic expression of TOSD, enabling its real-time computation in each servo cycle. To estimate the varying TOSD parameters, the discrete system dynamics is modeled via momentum changes, arriving at a set of linear identification equations that can also be solved in real time. The proposed TOSD formulation and online identification method are verified both in simulations and experiments.