Flexible Mechanisms Towards Surgical Application

With the advancement in endoscopy and surgical techniques, robot-assisted technologies have become appealing to push the limits of what surgeons can achieve. Flexible mechanism plays an important role in surgical applications; it enables the surgeon to access through narrow and winding natural orifices, which is becoming a future trend in minimally invasive surgery. In this chapter, we explore some key technical challenges in the design and control of such flexible mechanisms, with a special focus on the Tendon Sheath Mechanism (TSM). High flexibility and redundancy allow such flexible mechanisms to navigate through the complex environment and perform dexterous motions, but it also introduces unpredictable nonlinear behavior, such as backlash and hysteresis. The lack of rigidity at the end-effector also often introduces control uncertainty and inconsistency at loading and unloading. This chapter provides a detailed analysis of two innovative design concepts that can mechanically enhance the control performance, with better bending uniformity, and variable structural stiffness. In addition, a generalized learning-based compensation method for hysteresis behavior in the flexible mechanism is introduced. Lastly, challenges in the development of these techniques are discussed and explored.