Multi-objective Optimization of a Reconfigurable Spherical Parallel Mechanism for Tele-Operated Craniotomy

The practice of neurosurgery sometime requires to open a large space through the skull. The drilling operation is called craniotomy. The neurosurgeon needs to use specific surgical drill to perform this task. The high dexterity required for this operation has justified the development of robotic system for the manipulation of craniotomy instruments. A series of motion capture and force experimentation on Human cadavers have been carried out to collect kinematic and force data for the definition of a mechanical architecture specification. A 3-RRR Spherical Parallel Mechanism is proposed for the manipulation of the neurosurgical drill. This mechanism is modified by adding a variable parameter that changes the configuration of its base. Three pantographic mechanisms are integrated to control this variable parameter. The mechanism is optimized to generate the highest kinematic performance and the lowest motor torque to generate the minimum required drilling force. A series of kinematic simulation reveals that the introduction of the new reconfiguration parameter can improve both the dexterity and the force transmission of the mechanism.