State and output feedback stabilization of multiple chained systems with discontinuous control

The problem of state and output feedback stabilization of nonholonomic multiple chained systems is addressed and solved using a particular class of discontinuous control laws. The obtained control laws are relatively simple, compared with others existing in the current literature, and guarantee exponential convergence of the closed-loop system. A simulation example, showing the main features of the proposed controllers, is enclosed.     

Discontinuous control of nonholonomic systems

The problem of asymptotic convergence for a class of nonholonomic control systems via discontinuous control is addressed and solved from a new point of view. It is shown that control laws, which ensures asymptotic (exponential) convergence of the closed-loop system, can be easily designed if the system is described in proper coordinates. In such coordinates, the system is discontinuous. Hence, the problem of local asymptotic stabilization for a class of discontinuous nonholonomic control systems is dealt with and a general procedure to transform a continuous system into a discontinuous one is presented. Moreover, a general strategy to design discontinuous control laws, yielding asymptotic convergence, for a class of nonholonomic control systems is proposed. The enclosed simulation results show the effectiveness of the method.     

含未校准摄像机参数的非完整移动机器人自适应动态反馈跟踪控制

研究基于视觉伺服的不确定非完整移动机器人的跟踪控制问题.基于视觉反馈和状态输入变换,提出一类非完整运动学系统的不确定模型,并运用两个新的变换,对3种不同情况分别设计自适应动态反馈控制器来跟踪不确定系统的期望轨迹.利用李雅普诺夫方法和推广的Barbalat引理,严格证明了误差系统的收敛性.仿真结果验证了所提方法的有效性.     

Logarithmic control,trajectory tracking,and formation for nonholonomic vehicles on Lie group SE(2)

This paper studies the problem of set-point stabilisation, trajectory tracking, and formation tracking for unicycle-type vehicles by taking advantage of the exponential coordinates and the other mathematical tools provided by the Lie group setting of the special Euclidean group SE(2). Motivated by recent developments in geometric control approaches for holonomic systems, we first study the stabilisation problem for nonholonomic constrained kinematic systems by improving the logarithmic stabilising control laws in such a way that they can satisfy nonholonomic constraints too. We then extend the control design to the problem of trajectory tracking by proposing auxiliary systems and investigating the conditions for which the adjoint map in the Lie algebra preserves the velocity constraint. This leads to a global control law which is valid for general time-varying as well as non-smooth trajectories. The tracking control law is also applied to the problem of leader-follower formation tracking by constructing nonholonomic virtual leaders in the desired formation. Finally, the kinematic control law is translated to a differential drive robot using the backstepping technique. To demonstrate the effectiveness of the controllers, the numerical results are presented and the performances are compared with the other three controllers in the literature.     

基于视觉反馈的非完整机器人不确定链式系统的指数稳定

研究带有未知参数的非完整移动机器人的镇定问题. 基于已有不确定非完整链式模型, 运用辅助变量法和控制输入法分别设计控制器, 使系统状态指数收敛. 所提出的两种控制器不仅克服了对系统初始状态的限制, 而且具有高度的统一性. 仿真结果验证了两种控制方法的有效性.

     

实际输入饱和的一类非完整运动学系统的镇定

对一类非完整移动机器人提出了实际输入饱和下镇定控制器的设计方案.这种设计不是基于链式系统而是基于原始系统的.控制器的设计使用了滑模控制和多步控制策略,并用Lyapunov的思想证明了闭环系统的收敛性.最后,用设计的控制器对一类机器人进行了仿真,验证了方法的有效性.     

Stabilization of Nonholonomic Robotic Systems Using Adaptation and Homogeneous Feedback

This paper considers the problem of stabilizing nonholonomic robotic systems in the presence of uncertainty regarding the system dynamic model. It is proposed that a simple and effective solution to this problem can be obtained by combining ideas from homogeneous system theory and adaptive control theory. Thus each of the proposed control systems consists of two subsystems: a (homogeneous) kinematic stabilization strategy which generates a desired velocity trajectory for the nonholonomic system, and an adaptive control scheme which ensures that this velocity trajectory is accurately tracked. This approach is shown to provide arbitrarily accurate stabilization to any desired configuration and can be implemented without knowledge of the system dynamic model. Moreover, it is demonstrated that exponential rates of convergence can be achieved with this methodology. The efficacy of the proposed stabilization strategies is illustrated through extensive computer simulations with nonholonomic robotic systems arising from explicit constraints on the system kinematics and from symmetries of the system dynamics.     

Stabilization of nonholonomic chained systems via nonregular feedback linearization

This paper addresses the problem of feedback stabilization of nonholonomic chained systems within the framework of nonregular feedback linearization. Firstly, the nonsmooth version of nonregular feedback linearization is formulated, and a criterion for nonregular feedback linearization is provided. Then, it is proved that the chained form is linearizable via nonregular feedback control, thus enable us to design feedback control laws using standard techniques for linear systems. The obtained discontinuous control laws guarantee convergence of the closed-loop system with exponential rates. Finally, simulation results are presented to show the effectiveness of the approach.     

Finite‐time tracking control of uncertain nonholonomic systems by state and output feedback

This paper studies the finite‐time tracking control of nonholonomic systems in chained form with parameter uncertainties, unknown output gains, and mismatched uncertainties. To achieve the finite‐time tracking control of uncertain nonholonomic systems, we propose 2 types of controllers by state and output feedback, respectively. Both of the proposed 2 types of controllers can achieve the finite‐time output tracking control of the nonholonomic systems even in the presence of mismatched uncertainties and/or unknown gains. The effectiveness of our proposed controllers are illustrated with simulation examples.     

非完整向量幂式系统的光滑时变指数镇定

研究非完整向量幂式系统的镇定问题,通过引入一个辅助状态变量,此类系统可将转换成一个线性时变系统,由此可得至具有指数收敛率的光滑反馈控制律。该方法优点是控制律光滑并且设计过程简单,系统每个状态的收敛率可被事先确定。仿真结果表明,仿真结果表明了该方法的有效性。     

Adaptive control of nonholonomic robotic systems

This paper considers the problem of controlling the motion of nonholonomic robotic systems in the presence of uncertainty regarding the system model and state, and presents a class of adaptive controllers as a solution to this problem. The proposed control strategies provide simple and robust solutions to a number of important nonholonomic system control problems, including stabilization to an equilibrium manifold, motion control to an equilibrium point via trajectory tracking, and stabilization to an equilibrium point. All of the schemes are computationally efficient, are implementable without knowledge of the system dynamic model, and ensure uniform boundedness of all signals and accurate motion control; furthermore, most of the controllers can be implemented without rate measurements. The efficacy of the proposed approach is illustrated through extensive computer simulations with nonholonomic robotic systems arising from explicit constraints on the system kinematics and from symmetries of the system dynamics. © 1998 John Wiley & Sons, Inc.     

Tracking control of a nonholonomic mobile robot using compound cosine function neural networks

The purpose of this paper is to propose a compound cosine function neural network with continuous learning algorithm for the velocity and orientation angle tracking control of a nonholonomic mobile robot with nonlinear disturbances. Herein, two neural network (NN) controllers embedded in the closed-loop control system have the simple continuous learning and rapid convergence capability without the dynamics information of the mobile robot to realize the adaptive control of the mobile robot. The neuron function of the hidden layer in the three-layer feed-forward network structure is on the basis of combining a cosine function with a unipolar sigmoid function. The developed neural network controllers have simple algorithm and fast learning convergence because the weight values are only adjusted between the nodes in hidden layer and the output nodes, while the weight values between the input layer and the hidden layer are one, i.e. constant, without the weight adjustment. Therefore, the main advantages of this control system are the real-time control capability and the robustness by use of the proposed neural network controllers for a nonholonomic mobile robot with nonlinear disturbances. Through simulation experiments applied to the nonholonomic mobile robot with the nonlinear disturbances which are considered as dynamics uncertainty and external disturbances, the simulation results show that the proposed NN control system of nonholonomic mobile robots has real-time control capability, better robustness and higher control precision. The compound cosine function neural network provides us with a new way to solve tracking control problems for mobile robots.     

Switched mode feedback control laws for nonholonomic systems in extended power form

A class of nonholonomic control systems in extended power form is studied. It is demonstrated that under appropriate assumptions Lagrange's equations, including classical nonholonomic constraints, can be transformed into the extended power form. A switched mode feedback controller is used to obtain global convergence of the states of the extended power form to the origin. This feedback controller can be interpreted as a hybrid system consisting of a high level discrete event supervisor and a family of low level feedback controllers. The closed loop system exhibits finite-time responses.     

基于Lyapunov函数方法的时滞车辆纵向跟随控制

应用向量Lyapunov函数方法和比较原理,基于非线性车辆动态耦合模型,研究具有时间滞后的车辆跟随系统的指数稳定性问题,得到了车辆跟随系统的指数稳定性判据．根据滑模控制策略确定了车辆跟随系统的纵向控制规律,基于稳定性准则设计了车辆纵向跟随控制器参数．仿真结果表明,基于该方法设计的车辆纵向跟随控制器能使跟踪误差具有较快的收敛率．     

非完整链式系统的输出跟踪控制——动态扩展线性化方法

针对非完整单链和多链系统,利用动态反馈线性化技术设计了输出跟踪控制器.证 明了当满足一定的条件时,通过选择适当的输出变量并利用动态反馈可使非完整链式系统实 现输入-输出完全线性化,从而可设计线性控制器跟踪期望的运动轨迹.最后以移动小车的跟 踪控制为例,通过仿真验证了文中方法的有效性.     

非完整链式系统的输出跟踪控制 ——动态扩展线性化方法1)

Tracking control of nonholonomic single and multi-chained systems is investigated in this paper.It is shown that the nonholonomic chained systems can be completely linearized by dynamic feedback linearization if the proper output variables are chosen and certain conditions are satisfied,and linear tracking controllers can then be designed for the resulted linearized systems.As an example,a moving cart is simulated to verify the proposed strategy.     

Distributed Consensus of Multiple Nonholonomic Mobile Robots

Consensus problems of multiple nonholonomic mobile robots are considered in this paper. These problems are simplified into consensus problems of two subsystems based on structure of nonholonomic mobile robots. Linear distributed controllers are constructed respectively for these two subsystems thanks to the theory of nonautonomous cascaded systems. Consensus of multiple nonholonomic mobile robots has been realized using the methodology proposed in this paper no matter whether the group reference signal is persistent excitation or not. Different from previous research on cooperative control of nonholonomic mobile robots where the consensus problem under persistent exciting reference has received a lot of attention, this paper reports the first consensus result for multiple nonholonomic mobile robots whose group reference converges to zero. Simulation results using Matlab illustrate the effectiveness of the proposed controllers in this paper.      

A framework for the stabilization of general nonholonomic systems with an application to the plate-ball mechanism

We present a framework for the stabilization of nonholonomic systems that do not possess special properties such as flatness or exact nilpotentizability. Our approach makes use of two tools: an iterative control scheme and a nilpotent approximation of the system dynamics. The latter is used to compute an approximate steering control which, repeatedly applied to the system, guarantees asymptotic stability with exponential convergence to any desired set point, under appropriate conditions. For illustration, we apply the proposed strategy to design a stabilizing controller for the plate-ball manipulation system, a canonical example of nonflat nonholonomic mechanism. The theoretical performance and robustness of the controller are confirmed by simulations, both in the nominal case and in the presence of a perturbation on the ball radius.     

Robust Control for a Class of Time-delay Nonlinear Systems via Output Feedback Strategy

This paper studies the robust control problem for time-delay systems with complicated inherent nonlinearities and unknown disturbances. Based on the modified homogeneous domination method and by constructing the proper Lyapunov-Krasovskii (L-K) functional, output feedback controllers are successfully constructed to guarantee the boundedness of all the states of the closed-loop system. The convergence of the states is also realizable when the L₂ norm of the disturbance exists. The presented method is also extended to solve the control problem of nonholonomic time-delay system. Simulation examples are given to show the effectiveness of the proposed theory.