A Safety Joint with Passive Compliant and Manual Override Mechanisms for Medical Robotics

Force and collision control is a primary concern to guarantee the safe use of medical robots as such systems normally need to interact with clinicians and patients, while at the same time cooperate with other devices. Among different strategies, passive features working with intrinsically safety components are treated as one of the most effective approaches and therefore deserve in-depth study. In this study, we focus on the design of a novel back-drivable safety joint that incorporates a torque limiter with passive compliance and a manual override mechanism to disconnect the robotic joint from its drive train. The design and working principle of the proposed joint are explained, followed by the mathematical analysis of its performance and the impacts of parameters. An example of the design was manufactured and tested experimentally to validate the working concepts. It is concluded that the proposed multi-functional safety joint provides more versatility and customization to the design of bespoke medical robots and would limit the maximum torque that can be exserted onto the patient, allow the clinician to push the joint back, and enable the operator to switch back to manual override.