Development of a Three Degrees-of-Freedom Tendon-Sheath-Driven Upper Limb Exoskeleton With Sliding Mode Admittance Control for Microlaryngoscopic Surgery Assistance

Abstract

Abstract. Microlaryngoscopic surgery requires surgeons to maintain elevated arm postures for extended periods, leading to muscle fatigue, tremors, and reduced precision. Although upper-limb exoskeletons have been widely studied for rehabilitation and assistance, their use in surgical scenarios requiring both transparent motion following and stable postural support remains limited. To address these issues, we present a tendon-sheath-driven upper-limb exoskeleton (TULE) that provides ergonomic support during prolonged procedures. The system offers three degrees-of-freedom per arm and uses a simplified dynamic model tailored to the motion patterns of microlaryngoscopic surgery. A hybrid control strategy combines admittance control with computed-torque sliding-mode control. Simulations and hardware experiments show that the proposed controller reduces joint tracking errors compared to proportional–integral–derivative (PID) control while ensuring smooth torque output. Motion-following experiments demonstrate compliant human–robot interaction with low interaction torques. Tremor-suppression tests reveal an approximately 75–80% reduction in wrist tremor amplitude in lock mode, confirming the system's potential to enhance surgeon endurance and stability in microsurgery.