Limit cycles analysis of two-input two-output nonlinear control systems with transport delay using stability-equation method

In this paper, the stability-equation method is used to analyze limit cycles of two-input and two-output nonlinear control systems with nonlinearity and transport delay. By solving the two associated stability equations, families of constant limit cycle amplitude and frequency loci are portrayed in the parameter plane. Therefore, the overall limit cycle tendency with respect to the parameter variations can be realized clearly. A limit cycle can then be graphically predicted. The adjustable system parameters can be designed to suppress and remove existing limit cycles. An illustrative example is given to show the effectiveness of the proposed method.