Dynamic Hysteresis Compensation for Tendon-Sheath Mechanism in Flexible Surgical Robots Without Distal Perception

摘要

The accurate position transmission of tendon-sheath mechanisms (TSMs) is challenging but of significance to the flexible robot for minimally invasive surgery (MIS). The challenges are mainly attributed to 1) the tendon-elongation and its caused hysteresis that depend on the route configuration of the TSM and could result in misaligned position transmission, 2) realistic surgical scenarios requiring the TSM with arbitrary and even time-varying route configurations, and 3) the absence of distal sensory feedback due to strict spatial constraints. Existing works are always devoted to tackling 1) yet evade 2) and 3). Here a route-related tendon-elongation model is formulated to resolve 1), and in response to 2), a route-sensing optical fiber is used. Obeying 3), a feedforward hysteresis compensator is then developed to align the distal position of the tendon with the desired position. Our final contribution gives an application-oriented remedy for the foregoing methodologies. Applying our compensator on the challenging position transmission tasks subject to 2) and 3), the positional accuracy can be still maintained at around 97.50%; guided by the provided remedy, the surgical end-effector achieves sub-millimeter tip position accuracy. Extensive tests demonstrate that the pending concerns yet of great practical importance in existing related works are well resolved.