Relative task prioritization for dual-arm with multiple, conflicting tasks: Derivation and experiments

This paper presents new formulations in task-prioritization for dual-arms with multiple, conflicting tasks and experimental validations. An essential part of the proposed method is the use of relative Jacobian that treats the dual-arm as an equivalent single arm. As a result, three formulations are derived. The first formulation, called relative task prioritization, expresses a task prioritization at the acceleration level for a dual-arm, with multiple tasks, that is controlled as a single manipulator. The second formulation is an impedance control equation that allows direct control of the relative motion and impedance between two end-effectors. Our third formulation is a control law that combines relative task prioritization, impedance control, and time-delay estimation, which contributes to the ease of implementation of our proposed method. In the physical implementation, one arm draws a circle on a plate attached to the other arm in parallel with three subtasks. Then, intentional conflict among subtasks is induced. The experimental results show that when such conflict occurs, the higher priority task is guaranteed an immediate execution without influence from the lower priority task.