Abstract
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 30mm, and restrict area 5mm 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.
Highlights
Since the first robotic brain surgery was performed by an industrial robot in 1985 [1], various types of surgical robots had been used in different surgical environments due to the continuous update of robotics and the advance of modern control algorithms [2]
The safety of surgical robot can be improved though various software and hardware methods [6] such as tactile sensor [7], CT imaging technology [8], impedance /admittance control [9]–[12] and a series of adaptive control methods [13]
To apply the surgical robot to more complex surgical environment, safer and more intuitive pHRI control methods are needed during surgical operating [15]
Summary
Since the first robotic brain surgery was performed by an industrial robot in 1985 [1], various types of surgical robots had been used in different surgical environments due to the continuous update of robotics and the advance of modern control algorithms [2]. A method for constructing virtual fixtures of surgical robot is proposed in this paper, which based on the model of natural movement of the human arm to improve the safety and flexibility during the doctor dragging the robot. It can be seen that as long as the direction of V in the dragging process is limited, that is, V in the direction of dangerous boundary is eliminated, while the V in the direction of safety is retained, so that safe robot dragging can be realized, the human’s motion can be restricted in the defined area, so as to achieve a safer pHRI This restriction of movement in a certain direction is called virtual fixtures. The principle of virtual fixtures implementation will be elaborated in detail below
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