Trajectory tracking and obstacle avoidance control to unknown objects for redundant manipulators utilizing preview control (1st report, use of path planning by penalty method)

We propose a control method for redundant manipulators for working to unknown objects. When a manipulator's hand tracks a desired trajectory on the surface of an object of unknown shape, trajectory tracking and obstacle avoidance should be controlled at the same time. Real-time operation to an unknown object requires to achieve measurement, path planning and control simultaneously. We present a new method which controls redundant manipulators based on the planning of a collision-free arm form assuming a system for 3-D measurement of the object's configuration. The planning problem can be solved by the penalty method as a nonlinear planning problem with restricting conditions. The penalty method gives the collision-free arm form for the desired future trajectory utilizing an imaginary manipulator. We realize the functions of operation and collision-free movement for unknown objects, using a preview controller which changes the current arm form referring to the future arm form, using its redundancy. Effectiveness is confirmed by simulation experiments.