Maximum Allowable Load of Mobile Manipulator in the Presence of Obstacle Using Non-Linear Open and Closed Loop Optimal Control

In this paper, a new method which is a combination of open and closed loop optimal control is developed to find maximum load carrying capacity of nonholonomic wheeled mobile manipulator (WMM) in the presence of environmental obstacles. At first level, open loop control method is used to solve path planning problem and design an optimal trajectory with maximum dynamic load carrying capacity between initial and final point. Optimality conditions are obtained for carrying the maximum payload between two points in an environment including obstacles. The main contribution at first level is applying obstacle avoidance in the objective function that leads to a two-point boundary value problem. At second level, a nonlinear closed loop optimal controller is designed to perform optimal trajectory in real-time conditions. The main contribution at second level is applying the nonlinear Hamilton–Jacobi–Bellman equation to design an optimal nonlinear state feedback controller. Numerical procedure in both levels, that is time consuming, is performed off line and resulted control law is simply applied in real-time conditions. The other contribution of this paper is the combination of these levels; it makes sure that the achieved trajectory and maximum load is applicable. To show the effectiveness of the method, simulations are performed for a planar WMM and a spatial WMM named Scout as well as experimental results for Scout robot.