Endpoint-Side Optimization of a Five Degree-Of-Freedom Haptic Mechanism

One of the main issues in the design of haptic devices is to provide maximum transparency. In this paper a design methodology, which aims at the maximization of the transparency for a low-force five degree-of-freedom (dof) haptic device, is presented. The haptic device is optimized along a typical path with proper tolerances, rather than at some workspace operating point. The device, part of a training medical simulator for urological operations, consists of a two dof, 5-bar linkage and a three dof spherical joint. The requirement for reliable reproduction of low torques and forces leads to the need for maximum transparency, in other words to the need for minimization of device induced parasitic forces and torques. The multivariable optimization employed is based on the minimization of an objective function that includes all the haptic device mass/inertia properties as seen from the user side. Kinematical and operational constraints are taken into account. A new 5-dof haptic mechanism is constructed according to the optimization results. The optimized mechanism is substantially improved with respect to an existing device