Optimum Velocity Vector of Articulated Robot for Soft Bumping

Abstract

Controlling manipulators during the transition from the free space to the constraint space is important to avoid vibration or crashing of a grasped object in assembly tasks. This paper discusses smoothing the contact of an articulated manipulator with the object in the transition from the free space to the constraint space.
We point out that lateral velocities significantly change the momentum of the manipulator and thus much reduce the contact impact while keeping the pose of the manipulator and the desired velocity in the direction perpendicular to the contact surface.
First, we derive the optimal bumping velocity which minimizes the error between a desired steady state force and an impact force, and apply this method to a 2-link manipulator. Next, the relationship between the optimal bumping velocity and the momentum is considered in terms of energy ellipsoid. Further, we examine the optimal bumping velocity when time delay of contact detection exists. Lastly, simulation results of bumping by the 2-link manipulator are shown.