Design and Master-Slave Task Switching Obstacle Avoidance Control of a Hollow Continuum Manipulator
Continuum manipulators(CMs)exhibit excellent bending performance and flexibility as well as unique environmental adaptability and human-machine interaction safety.Therefore,they have broad application prospects in unstructured environments such as minimally invasive surgery,post-disaster rescue,narrow space maintenance,and home services.However,the central backbone of CMs occupies their internal space,and motion coupling be-tween their redundant modules hampers obstacle avoidance control and poses challenges to their practical application.To solve these problems,a wire-driven hollow CM was designed to leave sufficient physical space for the electric-liquid-gas pipelines of the end-effector and decoupling between its modules was realized using a Bowden tube in the structure.Considering the bending characteristics of the wire-driven CM,a simplified kinematic model and kinematic closed-loop control algorithm after decoupling were established.Furthermore,a method for calculating the shortest distance between obstacles and CMs was developed.Based on the traditional variable configuration obstacle avoid-ance control,an obstacle avoidance control algorithm based on master-slave task switching was proposed.This algo-rithm allowed the CM to avoid obstacles under the constraint of end trajectory tracking and could temporarily abandon tracking of the given end trajectory to avoid obstacles near this trajectory.Simulated and experimental results show that the CM has good motion ability and that the average error of the end position of trajectory tracking control is 2.510 mm,which is only 0.32%of the length of the CM.The proposed algorithm is effective and can accurately evaluate the priority of end motion and obstacle avoidance motion.This research provides a new reference and idea for the design and motion control of CM.
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