Abstract-Virtual reality is becoming very important for training medical surgeons in various operations. Interfacing users with a virtual training environment requires the existence of a properly designed haptic device. This paper presents the design and implementation of a new force feedback haptic mechanism with five active degrees of freedom (DOFs), which is used as part of a training simulator for urological operations. The mechanism consists of a 2-DOF, 5-bar linkage, and a 3-DOF spherical joint, designed to present low friction, inertia and mass, and to be statically balanced. The device is suitable for the accurate application of small forces and moments. All five actuators of the haptic device are base-mounted dc motors and use a force transmission system based on capstan drives, pulleys, and tendons. The paper describes the overall design and sizing considerations, the resulting kinematics and dynamics, the force feedback control algorithm, and the hardware employed. Experimental results are provided.Index Terms-Force feedback, haptic devices, training medical simulators, urological operations.

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The inductance of an arc discharge has been modeled and a mathematical formula given for the arc inductance in terms of its geometrical dimensions. This formula agrees with the experimental results and is used to determine the arc-channel radius. Inductance measurements have been taken for various values of pressure, interelectrode distance and applied voltage in a triggered spark gap. The dependence of inductance upon these parameters has been explained through the existing variations of the arc-channel cross section. Two mechanisms are responsible for the variations of inductance. The first is diffusion and the second is the tendency of the current channel to vary diameter with pressure, interelectrode distance, and applied voltage. The time history of the arc-channel inductance has been investigated. Finally, the ambipolar diffusion coefficient and the total charge number of the arc channel has been obtained.

Abstract. A new 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.

Abstract-This paper 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. Kinematical and operational constraints are taken into account. The resulting optimized mechanism is substantially improved with respect to an existing device.