A Virtual Fixtures Control Method of Surgical Robot Based on Human Arm Kinematics Model

Physical human-robot interaction(pHRI) is the most popular way to ensure the safety in robot surgery. Current research of pHRI in operation room focuses on the inside of the surgical area, which adapts virtual fixtures method for ensuring the safety of drag. But the safety problems caused by human error in the stage of dragging the robot from the outside surgical area to the inside surgical area are ignored. Therefore, a method of applying virtual fixtures to the outside of the surgical area is proposed to solve the safety issues during dragging stage outside surgical area. This method takes the kinematics model of human arm as the reference motion trajectory to construct the guided virtual fixtures, which is to restrict the robot movement in a defined area during the pHRI drag. This drag is based on admittance control method to improve safety and ensure flexibility. Experiment results show that the constructed guided virtual fixtures with the trajectory of the human arm model as the central axis, with radius 30 mm, and restrict area 5 mm can effectively limit the robot motion to a certain range. Simultaneously, the output speed of the robot in tangent direction of the central axis can well follow the change of the force applied by the doctor, and the output speed in the normal direction of the central axis can converge to zero stably at the pipeline boundary. Consequently, the purpose of improving the safety and flexibility of the surgical robot before surgical operation is realized.