4 degree-of-freedom haptic device for surgical simulation

Haptic interaction is a growing area of research and enables users to interact with virtual objects using their haptic sensory modality. Haptically enabled surgical simulation can allow users to be trained with realistic haptic feedback. Commercial-Off-The-Shelf (COTS) haptic devices typically provide either 3 or 6-Degrees of Freedom (DOF). While low-cost 3-DOF COTS haptic devices do exist, in many surgical simulation scenarios haptic feedback in more than 3-DOF is required. This work presents a low-cost attachment for retrofitting a 4th DOF to the affordable 3-DOF Phantom Omni haptic device. The attachment allows the provision of torque feedback around the stylus' longitudinal axis lending itself to applications where 3-DOF Cartesian forces and 1-DOF torque feedback are required, such as surgical screw insertion. In order to integrate the 4th DOF attachment, the kinematics of the resulting device are considered, and the Jacobian determined. The workspace of the Phantom Omni is also considered as well as the effect of stylus orientation on the ability to display torque. Finally the generation of forces and torques for simulating pedicle screw insertion as required in scoliosis surgery is discussed.