Planners search in configuration space, the space of all possible joint angles or vehicle poses, and look for a continuous path that never puts the robot inside an obstacle. Grid searches such as A* suit mobile robots; sampling methods such as RRT and PRM cope better with the many dimensions of an arm; optimisation-based planners smooth a rough path into something fast and fluid.
Planning answers where to go. A controller then executes the path, correcting in real time for slip, load and disturbance.
A bin-picking cell replans on every cycle, because the next part lies at a different angle and the arm must dive into the box and come out without hitting the walls or the fixture beside it.
