Bounded Integral Controller with Limited Control Power for Nonlinear Multiple-Input Multiple-Output Systems

In this brief, a bounded integral controller (BIC) with limited control power is proposed for a class of nonlinear multiple-input multiple-output (MIMO) systems. The sum-of-squares constraint on the control inputs with time-varying weights is studied and handled through the BIC design, which guarantees that both the control inputs and an auxiliary time-varying variable are dynamically constrained on a designed control circle. The BIC inherits the properties of the traditional integral controller to eliminate tracking errors and achieve disturbance rejections. Even under time-varying input weights, the BIC guarantees limited control power independently of both plant information and system states. The input-to-state (practical) stability of the closed-loop system is established. To demonstrate the effectiveness of the proposed method, experimental validations are conducted for two systems: a system with multiple dc motors subject to a power limit with time-varying input weights and a permanent magnet synchronous motor system subject to a voltage limit with time-invariant input weights.