During the past decade, robotic minimally invasive surgery (R-MIS) has been widely implemented in hospitals around the world, and has had a large impact on surgical technique in certain specialties [1]. The robotic surgical system typically requires a surgical tool with a long shaft and a dexterous tip, for example, the EndoWrist from the da Vinci Surgical System. The tool tip has three degrees of freedom (DOF)—yaw, pitch and grasp—and can offer an even greater range of motion than the human hand [1]. One problem is that the three motions are coupled; when driving the yaw DOF, the pitch DOF and grasp DOF are also actuated. This complicates the position control (decoupling is done in software) and has implications for sensing and force control as well (relations between actual output load and sensed input load can become nonlinear).
Nishizawa et al. [2] proposed a...
