Investigating remote sensor placement for practical haptic sensing with EndoWrist surgical tools

It has been frequently argued that the addition of haptic sensing to tele-operated surgical robots would benefit surgeon performance. Conventional haptic sensing technologies are impractical for application to minimally invasive surgery, due to size, sterilization robustness and cost vs. tool disposability. In this work we validate the concept of remote force measurement, where force interactions at the tip of a surgical tool are observed via simple torque sensors near the tool's actuators. This method provides reusable sensors located outside of the human body and so sidesteps many key issues that have limited practical haptic sensing in this scenario. Though such methods have been proposed and criticized by several groups in the past, we have been unable to locate quantitative results in the literature. Here, we provide initial remote force interaction measurements on a da Vinci EndoWrist needle driver tool. The measurements were obtained via simple custom torque sensors which easily attach to any EndoWrist tool. The complex cable-pulley transmission of the tool introduces expected nonlinearities over distal measurements. These effects are more pronounced in flexion than abduction DOFs. Despite these effects, the unprocessed torque data identifies contact with synthetic soft tissue at various actuator velocities and during external shaft loading.