Virtual spring based dynamic model and control of underactuated hand

A dynamic model was established for the underactuated 2-joint finger using the virtual spring approach, and a dynamic model for the underactuated 3-joint finger was deduced hereform. The dynamic models were verified by dynamic control experiments. The suggest approach not avoids the solution of the differential-geometrical equations, but also leads to a completely decoupled dynamic model which is ideal for the inverse dynamic analysis, simulation and real-time control directly. Meantime, a velocity observer was constructed based on the dynamic model to track the trajectory to make up the drawback of short of velocity sensors in the underactuated hand and the uncertain factors by the underactuated links. Comparing with the PID control or the control by the computed torque method, the observer is characterized by less trajectory tracking error and better dynamic control results.