This work presents a design methodology, which aims at the minimization of the mass, inertia and joint friction for a low - force five - dof haptic device. 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 lead to the need for minimization of device induced parasitic forces and torques. The multiobjective optimization employed is based on two objective functions that include mass/ inertia properties and joint friction. The kinematical and operational constraints are taken into account. The resulting optimized mechanism is substantially improved with respect to an existing device.

A haptic feedback mechanism with five active degrees of freedom (dof), part of a training simulator for urological operations, is presented. The mechanism consists of a 2-dof 5-bar linkage, and a 3-dof spherical joint. To reproduce very small forces and moments, the mechanism has low friction, inertia and mass, is statically balanced, and has a simple mass matrix. Roll-pitch-yaw motions of the tool result in motions of the corresponding actuator. Force feedback transmission is achieved via capstan drives and idler pulleys. The computation of the currents and the structure of the control loop are described.