Fixed Time Tracking Control Of Nonholonomic Wheeled Mobile Robots

Wheeled mobile robots with uncalibrated camera parameters are playing an increasingly important role in industrial,military,and commercial production activities.Among them,trajectory tracking is an important research content of nonholonomic wheeled mobile robots.The trajectory tracking time optimization problem of nonholonomic systems has attracted many researchers,such as finite-time control.However,the convergence time of nonholonomic robot trajectory tracking problems based on finite-time often depends on the initial value of the system state,which is not convenient to obtain the tracking time in advance.Therefore,this paper will take(2.0)and(1.1)nonholonomic wheeled mobile robots with uncalibrated camera parameters as examples to discuss their fixed-time trajectory tracking problems.The convergence time of fixed-time control is not determined by the initial value of the system,but only by the parameters of the controller,which is convenient for obtaining the control time in advance.The first two chapters of this paper mainly introduce the background and significance of our subject research,and discuss the existing research methods in the research of nonholonomic wheeled mobile robot control briefly.The basic knowledge of nonholonomic wheeled mobile robot is discussed,and the definitions and lemmas of finite time control and fixed time control are given.The last two chapters consider the fixed-time trajectory tracking control problem of(2.0)wheeled mobile robot with uncalibrated camera parameters firstly,and propose a fixed-time adaptive trajectory tracking control law.The dynamic model of the robot system with unknown parameters is given,and the tracking error system is derived.The state and input transformation are used to transform the trajectory tracking problem into a fixed-time stability problem of the error system.Then,a non-singular recursive terminal sliding mode surface control method is used to design a fixed-time controller,so that the actual system can track the reference trajectory in a fixed time.Then we discussed the trajectory tracking problem of the(1.1)wheeled mobile robot with uncalibrated camera parameters again.We considered the unknown external disturbance of the system and approached the unknown parameters in the system using the RBF neural network method.The problem of trajectory tracking in a fixed time is discussed.The simulation results verify the effectiveness of the designed controller.The innovation of this paper is that for a robot system with uncalibrated camera parameters,a new controller based on fixed-time trajectory design is designed,so that the actual robot can track the reference trajectory in fixed-time effectively,and the convergence time only depends on the controller parameters.Based on the terminal sliding mode method proposed in the previous literature,we have designed a new third-order recursive sliding mode surface model,which can guarantee the third-order chained system stability in fixed-time.