The application of robotic manipulators to complex tasks such as assembly, or insertion often requires position/force control of the end-effector, and this has been widely studied. A related task is robot compliant motion over unknown objects. The goal is to move the effector, while maintaining contact, about the object. For this application a dynamic hybrid velocity/force controller is studied. The constraints are characterized in the manner proposed by M. Mason (1981). A nominal velocity trajectory is computed, and nominal hybrid joint commands are explicitly given in terms of the sensed joint coordinates and sensed local contact information. For robustness, servoing is added, and an example design is given. Finally, the step response of the controller is simulated for the case of rolling the effector about an unknown object.
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