A Research Of Robust Tracking Control For Multi-rigid-body Systems Based On Disturbance And State Estimation

As a typical class of mechanical systems,multi-rigid-body systems have a wide range of applications in many fields such as machinery,vehicles,robots and aircraft,and so on.In many practical applications,there are constraints such as model uncertainty,unknown external disturbances and actuator saturation,and strong nonlinearity and strong coupling;due to space and cost constraints,it is difficult to install suitable sensors in each part of the multi-rigid-body systems to obtain the system states.The existing control methods are mostly based on state feedback control,and there are shortcomings such as complex controller structure,difficult parameter adjustment,and difficulty to guarantee the actual control accuracy.Aiming at the problem of robust tracking control for the multi-rigidbody system,in order to eliminate the influence of uncertain components and control input constraints on the motion accuracy of the dynamic model of the multi-rigid-body system under the conditions of limited modeling,measurement,and actuation ability,this dissertation studies the estimation and compensation of uncertain components,state observer design,design of high precision robust tracking controller with simple structure and easy parameter tuning,and stability derivation.It has a wide application prospect in the fields of manipulator workshop operation,space robot satellite maintenance,carrier autonomous motion,and so on.In this dissertation,we propose a theoretical method of robust control based on estimates of disturbance and state for robust tracking control of multi-rigid-body systems,and use the estimation and compensation of disturbance,estimation and replacement of state,and combine with controller design to realize the high-precision trajectory tracking of multi-rigid-body systems and verify the effectiveness of the proposed control schemes by the experimental platforms of multi-rigid-body systems.The experimental results show that the robust control method based on estimated data proposed in this dissertation has satisfactory steady-state tracking accuracy and transient state performance.The main contributions and innovations of this dissertation are summarized as follows:(1)This dissertation studies the proportional-integral-derivative(PID)control design scheme based on proportional-derivative(PD)controller and uncertainty and disturbance estimator(UDE),simplifying the parameter adjustment of the PID controller,and the ultimate bounds of the tracking errors of the single parameter adjustment are realized.On this basis,considering the robust tracking control problem of multi-rigid-body systems without velocity measurements,the UDE is designed to be improved and extended to the output feedback situation.We propose a simple feedback-control scheme that includes a modified Luenberger state observer(LSO)to estimate velocity and a modified UDE to estimate exogenous disturbance.The novel feature of the scheme is that a mutual coupling between LSO and UDE is introduced to improve the estimation and control precision.By using the designed linear nonsingular state transformation and ingenious parameter mapping,the performance analysis of the closed-loop system is simplified.By the singular perturbation theory,we derive a simple stability condition and a single-parameter tuning approach to reduce the steady-state estimation errors and tracking errors.Finally,the performance improvement resulting from the mutual coupling effect,as well as the effectiveness of the parameter tuning approach,are demonstrated by numerical simulation and experimental verifications on a three-degree-of-freedom(3-DOF)helicopter platform.(2)Robust output feedback tracking control of n-DOF multi-rigid-body systems with limited state measurements is investigated.An improved extended high gain observer(EHGO)is designed to estimate the unmeasurable system states as well as uncertainties and disturbances.A novel control scheme combining the improved EHGO and a continuous PID-sliding mode control(SMC)scheme is proposed.The transient response performance of the closed-loop system is improved,while the steady-state accuracy of estimation and tracking is ensured.The effectiveness of EHGO is verified using the Lyapunov stability method.In addition,the stability and convergence of the closed-loop system are demonstrated by singular perturbation theory.Numerical simulations and experimental results show the performance advantages of the proposed control scheme.(3)A novel robust finite-time tracking control scheme is proposed for a class of single-input single-output(SISO)multi-rigid-body systems subject to the model uncertainty,external disturbance,and input saturation.A barrier function-based disturbance observer is designed to estimate nonsmooth nonlinear composite disturbances of the system with finite-time convergence performance.Also,an adaptive continuous nonsingular terminal sliding mode control(CNTSMC)scheme,based on the barrier function and the estimate of the BFDO is developed.The Lyapunov stability and finite-time convergence of the proposed control scheme are proved.The effectiveness and performance advantage of the proposed control scheme is demonstrated by numerical simulations and comparison with some existing control methods.The research results of this dissertation are conducive to solve the problem of highprecision robust tracking control of multi-rigid-body systems,and have certain guiding significance for the design and development of robust tracking controllers based on estimates of disturbance and state,simple structure and easy-to-tune parameters.