Design of VRFT Based Feedback-feedforward Controllers for Enhancing Disturbance Rejection on Non-minimum Phase Systems

Abstract

AbstractIn this work, Virtual Reference Feedback Tuning (VRFT) based feedback-feedforward controllers are designed for non-minimum phase systems to enhance the disturbance rejection. In model based design methods the feedforward controller is inverse of the plant model reduces the controller performance in the presence of uncertainties. The novelty of the work lies in to design VRFT based controllers independently for the feedforward structure, which decouples set point tracking and disturbance rejection. The optimal filter selection and algorithms to design the controllers were proposed with non-measurable disturbance signal using open loop experimental data. These controllers are applied to discrete time non-minimum phase Flexible Transmission System (FTS) with no load, half load and full load conditions. The simulation study on FTS with feedback and feedback plus feedforward structures evaluates the effectiveness of proposed controllers. The performance indices like Integral Absolute Error (IAE), Integral Square Error (ISE), Total Variance (TV), VRFT Objective Function (JVR) and Fragility Index (FI) are used to compare the controller’s performance. The simulation results indicate that proposed feedback plus feedforward controller is superior to feedback controller.