Dynamic Modeling of the da Vinci Research Kit Arm for the Estimation of Interaction Wrench

The commercialized version of the da Vinci robot currently lacks of the haptic feedback to the master arm. Thus, the surgeon has no haptic sense and relies only on the visual feedback. For this reason, in the recent research activities using the da Vinci Research Kit (dVRK) platform, the reflection of the interaction force between the slave tool and the environment to the master manipulator is a topic of high interest. In this work a sensorless model-based approach for contact force and torque estimation is presented and validated. The dynamics of the dVRK slave arm is modeled and its parameters are identified. The idea is to use the joint torques obtained from the measured motor currents and to subtract the torques resulting from the dynamics of the robot arm. The resulting torques are therefore only due to the external forces and torques acting on the tool, which are then obtained through the inverse transpose of the Jacobian matrix. The accuracy of this method is assessed by comparing the estimated wrench to the one measured by a force/torque sensor (ATI mini 45). It is shown that the external wrench is well estimated compared to the measured one.