A Unified Approach to Compliant Motion Control

This paper studies a unified approach to the design of non-adaptive and adaptive model-based controllers for different types of compliant motion. By regarding the interacting robots and environments as one integrated mechanism, with a common set of generalized coordinates describing its motion, compliant motion can be viewed as an unconstrained motion, and all the control methods developed for free motion control, such as PID for position control, computed torque for trajectory control, and adaptive control for dealing with large parameter uncertainty, can be used straightforwardly, achieving global stability and motion tracking convergence. Since there are genrally more joint actuators than the number of degrees of freedom of the integrated mechanism, the remaining freedom in choosing joint inputs is used to achieve other benefits, such as joint torque minimization or guaranteeing contact with unidirectional constraint surfaces, depending on the specific problem.