下肢康复机器人动力学建模约束违约抑制

The U-K theory provides a new concept for obtaining the explicit dynamic equation of constraint multibody system. However, one consequence of the numerical approximation and truncation error is the constraint violation of the dynamic equation at the position and velocity level. Baumgarte's constraint violation stability methods (BSM) provide a stable dynamic equation by constraint modification. Nevertheless, the selection of Baumgarte parameters usually involve a trial-and-error process, which may result in the failure of simulation results. Consequently, the Baumgarte parameters selection problem is studied by using the classical fourth-order Runge-Kutta method, and the explicit dynamic equation of robot system based on the modified U-K theory by BSM is established. Furthermore, the lower limb rehabilitation robot is taken as the research object for simulation analysis. The results show that the constraint violation can be effectively suppressed. The joint angle errors are controlled within the range of -5×10^-3(°)-5×10^-3(°), the joint angular velocity errors are controlled within the range of -2×10^-4 rad/s-2×10^-4 rad/s, and the operation trajectory of the robot end-effector can be well close to the predetermined target of the system.