Design and control of a rigid–flexible coupled supernumerary robotic limb used for auxiliary operation

Abstract

Due to the limitations of inflexible end-effector adjustment, low load-to-weight ratio, and poor human–machine motion compatibility in conventional rigid supernumerary robotic limbs (SRLs), this paper proposed a rigid–flexible coupled SRL that integrated a cable-driven manipulator with a continuum segment, which can enhance the control performance with better posture adjustment capability by leveraging the high stiffness and positioning accuracy of the manipulator and the flexibility of the continuum structure. An active decoupling kinematics mode for the cable-driven SRL is established based on Denavit–Hartenberg (D–H) method and joint coupling mechanism for analyzing the relationship between the bending shape and the configuration parameters. Moreover, a human upper limb motion detection system based on the inertial measurement unit is proposed, and a human–machine cooperative control strategy for the SRL based on distributed inertial sensors and a neural network algorithm is put forward to realize high-performance cooperative control of SRL. Finally, an experimental prototype of SRL is built, and its experimental results indicate that the SRL exhibits high control performance and better human–machine collaborative operation capability, the average deviation of the end position of the robot is 4.8 mm, with a maximum deviation of 6.5 mm. This study validates the rationality and feasibility of the proposed external limb structure, as well as the effectiveness and correctness of the established kinematics model and control strategy.