Multi-Interaction Control for Manipulators in Unknown Environments Based on Hybrid Position-Impedance-Force Control

For the uncertainty of human-manipulator interaction and the unknown environment, a velocity control based scheme is developed to study the interaction among the human, the manipulator and the environment. Firstly, two 6-dimension force sensors are mounted at the end-effector of the manipulator to measure the interaction forces, and a compliant link with single DOF (degree of freedom) is added at the tool connection to achieve the compliance of the manipulator. Secondly, the compliance of the manipulator and the tool is modeled based on iTaSC (instantaneous task specification using constraints), so as to relate forces and position/velocities in the output space and realize the contact force control between the manipulator and the environment, and the stiffness matrix is adopted to drag the manipulator by an operator. Through the hybrid force-position-impedance control, the operator can drag the manipulator to complete a series of position/force tasks and interact with the unknown environment under the constraint of the safety area. Finally, the proposed algorithm is tested on a UR5 platform to complete the contour tracking task, which confirms that the proposed approach can implement good interaction control.