| This dissertation presents a method to protect objects from touch by the robot during teleoperation. Using the point cloud obtained in real-time by a depth camera, a virtual fixture is placed around protected areas of the workspace to keep the robot at a safe distance. Upon violating the protected area, the operator receives force feedback that opposes motion inside the forbidden region. Due to the fast nature of our haptic rendering algorithm, this method can protect moving objects in a dynamic environment as it is captured in real-time by the depth camera. The methods are implemented and evaluated on a surgical robot. In addition, adaptive techniques are developed to improve the control performance of the robot a) in contact with soft tissue with nonlinear, unknown and time varying biomechanical properties, b) in the absence of end effector measurements and c) under variable cable tension. It is anticipated that virtual fixtures will increase the speed and accuracy of procedures and will reduce the operator's fatigue. |
