Improvement of the direct kinematic model of a haptic device for medical application in real time using an extra sensor

This paper deals with a spherical parallel manipulator developed for a master device, used in a teleoperation system for surgical application. The aim is to improve the calculation of the direct kinematic model (DKM) even when the parallel manipulator is in a singular configuration by using an extra sensor for a passive joint. A new simple approach for the DKM calculation of the haptic device, in order to meet requirement of real time applications, is developed. The measure of a passive joint´s angle reduces the calculation time and improves the accuracy of the direct model particularly in the vicinity of the singular positions. Experiments were conducted on tele-operation system despite of the presence of singularities in the master workspace. The obtained results demonstrate the feasibility of the approach.