Research On Motion Control Of Uncertain Nonholonomic Wheeled Mobile Robot

Nonholonomic wheeled mobile robot (WMR) is a typical multiple input multiple outputcoupled underactuated nonlinear system, thus its motion control becomes a very challengingproblem. Moreover, most of the WMR work in a complex unknown environment, making itmore easily affected by a variety of uncertainties and disturbances, Therefore, solving themotion control problems of WMR with complex uncertainties has profound significance andurgent practical needs.In this paper, the motion control strategies for WMR with uncertainty of positioning, un-certainties of parametric and non-parametric, disturbances of skidding and slipping are pro-posed. The finite-time control of nonholonomic single-chain system and the WMR dynamicscontrol with bounded torque are also discussed. The major research findings are as following:(1) The WMR path following problem with positioning uncertainty is studied, a globaluniformly asymptotically stable controller based on adaptive extended kalman filtering opti-mized by improved genetic algorithms is proposed.(2) A robust finite-time stabilization control law for the n-dimensional uncertain nonho-lonomic single-chain system is proposed. By using the input-state-scaling technique, the sys-tem is divided into two decoupled independent subsystems, which are a first-order and an(n-1)-order respectively. In order to solve the singular problem of (n-1)-order subsystem withthe discontinuous transformation, a segmented control strategy is applied in the first-ordersub-system, and the global feature of the control law is ensured. The controller designcomplexity of (n-1)-order subsystem is reduced by using the backstepping design method.Since the control law design process is based on finite-time Lyapunov theory, the finite-timestability of the system is ensured.(3) The trajectory tracking problem for WMR with parametric and non-parametric uncer-tainties of body dynamics model is studied, a globally asymptotically stable saturation controlscheme based on adaptive backstepping sliding mode control is proposed. The linear modelwith system overall uncertainty is established by kinematics input-output nonlinear feedbackand dynamics input transformation, and a dynamic adjustment mechanism is adopted for thecontrol inputs saturation constraint. The smoothness and rapidity of sliding mode control isimproved by using power reaching law, the chattering of sliding mode control is weakened byadaptively estimating the upper boundary of sytem overall uncertainty.(4) A unified control method for trajectory tracking and stabilization of WMR with para-metric and non-parametric uncertainties of actuator dynamics mode is proposed. By using backstepping technique, the controllers of kinematics, body dynamics and actuator dynamicsare designed independently, a time-varying control amount is adopted in the kinematics con-troller, making no singular when the tracking errors model is used for stabilization control, thereinforcement learning adaptive fuzzy control with robust item is applied by the controllers ofbody dynamics and actuator dynamics to compensate the complex uncertainties of the system,and in order to avoid the calculation inflation of backstepping procedure, a class of nonlineartracking-differentiator is used. The closed-loop system is ultimately uniformly bounded.(5) A robust H∞unified controller based on adaptive neural network disturbance observ-er for trajectory tracking and stabilization of the WMR with unknown skidding and slippingdisturbances is proposed. By using the transverse function (TF) and standard Lie computingmethods, the no singular input-output completely decoupled unified control model which isequivalent with the original system is established. The skidding and slipping disturbances areestimated by the adaptive neural network disturbance observer, and the estimation error isinhibited with predetermined level by the H∞controller, eliminating the unknown skiddingand slipping disturbances, ensuring the H∞control performance of the system.The effectiveness of proposed methods are verified by the simulation results, and finally,a WMR fast real semi-physical simulation platform is established, and some of the proposedmethods are experimented, the effectiveness of these methods are further validated.