Trajectory optimization and control for robot manipulator using evolution strategy and fuzzy logic

Robot manipulators have some physical constraints such as the limits of the position, velocity, acceleration and jerk. In order to increase the productivity, it is desirable to drive the manipulators as fast as possible. The problem can be formulated as the time optimal control problem under the given physical constraints. But it is very difficult to obtain the exact solution of the time optimal control problem. The paper solves this problem in two steps. In the first step, we find the minimum time trajectories by optimizing cubic polynomial joint trajectories under the physical constraints using the modified evolution strategy. In the second step, the fuzzy controller is optimized for robot manipulator to track precisely the optimized trajectory found in the previous step. Experimental results for SCARA type manipulator show that the proposed method is very useful.