Design and optimization of spherical parallel manipulator as a haptic medical device

This paper deals with the design and analysis of a spherical parallel mechanism (SPM) to be used as a haptic device for a medical application. The chosen application is mini invasive surgery during which an anastomosis technique has to be performed. First, the task space, necessary to perform an anastomosis technique, which consists in suturing two parts of a ruptured hollow organ, was determined using a motion capture system. An experimented surgeon was asked to perform the anastomosis technique on a simulator. Several markers were used to track the motion of the hand-tool system during the operation. The experimental data were used to identify the necessary workspace for performing this operation. Then, a spherical parallel manipulator was designed, which has a workspace containing the desired workspace. An optimization procedure was carried out to find the optimal spherical manipulator with the closest workspace to the desired one. Genetic Algorithms were used to solve this problem. The effect of the rotation range around the tool axis on the structure parameters and workspace is also discussed. Finally, the obtained design parameters were shown, through simulation, to yield the required workspace.