Human-Robot Cooperative Motion Constraint Control of Surgical Robot Based on Virtual Fixture

Surgical robot is one of the most important application fields of human-robot collaboration. Since the operating objects are often fragile human tissues, how to improve the safety of the surgical process is the key for practical application of surgical robots. General human-robot interaction methods for safety such as collision detection and obstacle avoidance are relatively passive and robot-based, having difficulty in dealing with complex surgical scenarios. Virtual Fixture(VF), an active motion constraint method, is more suitable for shared control in surgical scenarios. This paper introduces a combination of VF method with admittance control for avoiding damage to robot or tissues while complying with doctor's intention. Firstly, in order to obtain the human-robot interaction force, a statistical method for six-dimensional force sensor calibration is proposed. Then, two velocity-based admittance control models are compared by simulation, and the first order inertial model is selected. On the basis of these, a variety of hard VFs with visual information are established. Finally, the effectiveness of the proposed method and the causes of violation are analyzed by experiments on a serial robot manipulator.