Design of Structured Controller Satisfying H Infinite Loop Shaping using Evolutionary Optimization: Application to a Pneumatic Robot Arm

paper proposes a new design procedure of a fixed-structure robust controller for the joint space control of a pneumatic robot arm. The proposed technique is based on the concept of H ∞ loop shaping which is a sensible method for robust controller design. However, in conventional H ∞ loop shaping, the order of the controller is much higher than that of the plant. It is not easy to implement this controller in practical applications. To overcome this problem, in this paper, H ∞ loop shaping control under a structure-specified controller for a pneumatic robot is proposed. The performance and robust stability conditions of the designed system satisfying the H ∞ loop shaping are formulated as the objective function in the optimization problem. Genetic algorithm (GA) is adopted to solve this problem and to achieve the control parameters of the proposed controller. Additionally, in the proposed technique, the performance weighting function, which is normally difficult to obtain, is determined by using GA. The optimal stability margin is used as an objective in GA for selecting the optimal weighting parameters; the requirements in terms of performance specifications are utilized as additional constraints in order to get more practical parameters. The designed controller contains simple structure with lower order and still retains the robustness and performance specification. Simulation results show that the robustness and performance of the proposed controller are almost identical to those of the controller designed by H ∞ loop shaping method. Experimental results verify the effectiveness of the proposed technique.