Optimal H₂ Input Load Disturbance Rejection Controller Design for Nonminimum Phase Systems Based on Algebraic Theory

This work discusses the issue of input load disturbance rejection (ILDR) for open-loop nonminimum phase (NMP) plants. A novel analytical solution is proposed on the basis of the internal model control (IMC) theory. Differing from other methods, the proposed design is conducted to optimize the ILDR criterion. Optimization of the input disturbance response of the controller is performed under the constraints on robustness. When the input load disturbance is taken into consideration, the proposed controller performs better disturbance rejection capability in terms of 2-norm than most explored IMC-based controllers derived from the conventional criterion. Typical NMP processes are systematically analyzed. Numerical examples are given to illustrate the effectiveness of the novel solution. The quantitative performance specifications and robust stability can be obtained by monotonously tuning the single parameter. Results show that the proposed solution makes the proposed method yield the expected dynamic responses