A study for the dynamic system of coupled cable-driven structure in surgical robot instrument

Many surgical robots adopt a tendon driven mechanism using cable and pulley to transmit the power. However, although tension is the main medium of power structurally, it is directly related with cable material characteristics including not only elastic region which make it able to use fixed spring constant but also nonlinear elastic and yielding one. Therefore, in the view point of control, it is difficult to control the force on end-effect with the torque generated from driving motor and pulley located on other place. In addition, interference between links can occur in small size and multi DOF system as surgical robot instrument. In surgical operation, both motion and force are important element for successful result. Thus, to make it possible to force control of surgical robot instrument, this paper derives dynamic governing model of coupled cable pulley structure. And the dynamic analysis and equation is proven by both simulation and experimental test.