Research And Applications Of Anti-disturbance Control Algorithms Via Fuzzy Disturbance Modeling

Since disturbances widely exist in practical applications,the problem of disturbance attenuation or rejection has been a hot topic in the field of control engineering.Disturbance-observer-based control(DOBC)approaches have received extensive attention and research in the past few decade,and have been successfully applied in many practical applications.However,the problem of disturbance modeling is still a challenge in DOBC theory research,especially for those irregular and nonlinear disturbances.This thesis proposes a novel disturbance modeling approach under the DOBC framework by combining with T-S fuzzy modeling capabilities for nonlinearities,and further presents the design methods of disturbance observer and composite controller for several kinds of complex systems with unknown disturbances.The main research work and contributions of this thesis are listed as follows:(1)The anti-disturbance dynamical tracking control problem is investigated for a class of MIMO systems subject to unknown disturbance and nonlinear dynamics.Different from some traditional anti-disturbance results,T-S fuzzy models are firstly employed to describe the nonlinear disturbances,in which a disturbance observer based on T-S exogenous system is designed under different conditions to estimate the unknown nonlinear disturbances for the plants with known and unknown nonlinearities,respectively.By integrating the estimates of disturbance with PI-type control input,a composite controller based on convex optimization theory is proposed to ensure the system stability and convergence of the tracking error to zero.Meanwhile,the satisfactory disturbance estimation and attenuation performance can also be achieved by the designed optimization algorithm.Finally,the effectiveness of the proposed control schemes is verified by simulations for A4D aircraft dynamic model with three different types of nonlinear disturbances modeled by T-S fuzzy models.(2)The anti-disturbance dynamical tracking control problem is discussed for a class of systems subject to input saturation and unknown disturbances.By describing the complex nonlinear disturbances with T-S fuzzy models,the corresponding disturbance observers are designed for the cases of known and unknown nonlinearities,respectively.By combing disturbance estimate and PI control input,a composite anti-disturbance controller can be designed to guarantee the system stability and satisfactory tracking performance with convex hull representing saturated linear feedback.Meanwhile,an estimation of domain of attraction can be given by the level set of the Lyapunov function.(3)An anti-disturbance dynamical tracking control scheme is proposed for a class of T-S fuzzy systems subject to parametric uncertainties and unknown disturbances.By modeling exogenous disturbances with T-S fuzzy models,a composite observer is constructed to estimate system states and disturbance simultaneously.In addition,based on observer estimation and PI control algorithm,a composite controller is designed to ensure system stability,tracking performance as well as the desired disturbance estimation and rejection performance.(4)The disturbance estimation and rejection problem are discussed for the yaw channel dynamics of small-scale unmanned helicopter subject to mismatched disturbances.Following the T-S fuzzy description for unknown nonlinear disturbances,a composite control input is designed to attenuate the influence of mismatched disturbances in system output channel by combining state feedback control,disturbance observer and disturbance compensator.The satisfactory control performance can be verified using linear inequality optimization algorithm.Simulation results on a yaw channel dynamical system can reflect the feasibility and effectiveness of the proposed disturbance rejection approach.