移动机器人的免疫非时间参考路径跟踪控制

针对移动机器人非时间参考控制方法的不足之处,借鉴生物免疫反馈响应过程的调节规律,提出了移动机器人的免疫非时间参考路径跟踪控制方法。该方法既有不依时间规划调节输出控制的特性,而且充分考虑到机器人机械结构与电机力矩特性的要求,实现了在误差较大时对控制量的限幅;通过选取合适参数,还能减小系统的超调量,进一步改善整个控制系统的性能。对于动态事件,采用插入算法,提高机器人对动态环境适应能力,使控制方法更适宜实际应用。仿真与实物实验,验证了该方法的有效性。     

基于Backstepping方法的移动机器人路径跟踪问题研究

针对轮式移动机器人的路径跟踪问题以及其非完整特性,引入一种新的虚拟反馈量,使用反演法设计了路径跟踪控制器.首先通过移动机器人的运动学模型得出其运动学位姿误差微分方程,然后基于Backstepping(逐步后推)方法设计控制器,通过构造的Lyapunov函数证明了所设计的控制器的稳定性;最后用Matlab进行仿真以及SM35机器人进行实验,结果表明,所设计的控制器能使移动机器人以任意小的误差跟踪任意给定的参考路径.     

基于线性二次型算法的轮式移动机器人轨迹跟踪控制

文章在控制输入饱和约束条件下,以非完整移动机器人的运动学模型为对象,研究了移动机器人的轨迹跟踪问题.首先在参考轨迹处对运动学模型进行线性化得到移动机器人线性时变系统,证明了其能观性和能控性,在此基础上设计了饱和约束条件的分段线性二次型控制器(Piecewise Linear QuadraticRegulator,PLQR),并基于Lyapunov方法证明了其稳定性.在MATLAB软件平台下的仿真和实验结果表明,基于PLQR的轮式移动机器人对不同初始位姿及不同的参考轨迹都有较好的跟踪效果,且能够避免控制律跳变现象,满足饱和约束条件.     

非完整移动机器人全局路径跟踪控制

根据制导路径跟踪理论,提出了一种非完整移动机器人全局路径跟踪控制方法.这一方法首先在路径坐标系上计算实际位置与期望位置的误差,利用制导的路径跟踪理论,导出消除该误差所需的姿态角和路径参数更新律,然后据此求解角速度及实际控制.文中还给出了初始路径参考点的计算方法,分析了路径跟踪方向和反转方法.稳定性分析证明该方法没有控制奇异点,受控闭环系统全局一致渐近稳定.最后通过移动机器人典型路径跟踪实验验证了所提出方法的可行性.     

离轴式带拖车移动机器人的路径跟踪控制

研究了离轴式拖车移动机器人系统任意一节车体的几何路径跟踪问题. 首先推导出系统的时间--状态线性化模型并证明了系统的能控性; 然后应用内模原理设计了线性动态反馈控制律, 该控制律可以保证路径跟踪误差有界和最终一致有界, 且最终一致界正比于期望路径函数变化率的立方. 仿真结果证实了控制律的有效性.     

含模型不确定性移动机器人路径跟踪的分层模糊控制

对受非完整约束且含模型不确定性的移动机器人基于分层模糊系统设计了跟踪期望几何路径的鲁棒间接自适应控制方案.此方法除实现路径跟踪外,还可避免控制器的奇异性并保证跟踪方向.由于控制结构中使用了分层模糊系统,大大减少了模糊规则数目;并用鲁棒控制项对模糊系统逼近误差进行补偿,减少了其对跟踪精度的影响.证明了闭环系统跟踪误差收敛到原点的小邻域内,且可通过适当增大鲁棒控制项的设计参数使跟踪误差进一步减小.最后用实验结果验证了方法的有效性.     

离轴式拖车移动机器人的任意路径跟踪控制

离轴式拖车移动机器人属于非完整系统,当车头线速度随时间变化且过零变号时,难以用一个控制器实现系统对期望路径的跟踪.本文研究离轴式拖车移动机器人系统的任意路径跟踪问题.首先由系统和虚拟小车的运动学方程得到误差状态模型,线性化后用坐标变换将其化为标准型,然后基于Lyapunov方法构造出一种跟踪控制律.只要车头的运动线速度有界且不趋于零,其导数有界,则所设计的控制律就可以保证系统跟踪任意的期望路径,且跟踪误差最终一致有界,最终界的大小与期望路径的曲率变化率成比例.当期望路径的曲率变化率为零或趋于零时,所设计的控制律可以保证拖车移动机器人指数收敛到期望路径.仿真结果证实了控制律的有效性.     

基于“非伪”理论的非完整移动机器人轨迹跟踪控制

"非伪"控制是一种基于数据驱动的无模型控制方法,它根据输入-输出数据进行在线学习,计算与当前系统状态相匹配的控制量并作用于系统,以获得系统所要求的动静态品质,并以此检验系统是否满足该性能指标.基于"非伪"控制理论,研究了移动机器人的轨迹跟踪控制问题.根据非完整移动机器人的动态方程,采用"非伪"控制,直接作用于移动机器人的控制输入,使移动机器人能快速、准确地跟踪期望轨迹.     

带拖车移动机器人全局路径跟踪控制

研究带拖车移动机器人的前向路径跟踪控制和倒车路径跟踪控制问题.首先建立系统的运动学模型,并进行系统的运动特性分析;然后基于Lyapunov方法提出一种新的单体移动机器人全局路径跟踪控制器,并将其引入带拖车移动机器人的前向路径跟踪控制;再后通过运动学变换,实现了拖挂任意节拖车的系统的倒车路径跟踪控制;最后针对三车体系统的两种路径跟踪控制进行仿真,结果表明了该方法的有效性.     

基于全局视觉的轮式移动机器人轨迹跟踪控制

将视觉伺服控制思想引入到全局视觉条件下的轮式移动机器人轨迹跟踪控制中,提出一种基于消除图像特征误差的控制方法.讨论并推导了包含电机模型的非完整移动机器人动力学方程,设计了鲁棒速度跟踪控制器.实验结果证明了文中方法的有效性.􀁱     

Delayed reference control for multi-degree-of-freedom elastic systems: Theory and experimentation

The objective of this paper is to provide an experimental proof of the effectiveness and ease of implementation of a non-time based control strategy for the simultaneous active vibration control and path tracking of multi-degree-of-freedom linear systems. What is peculiar in the proposed scheme, named DRC, is that it allows reducing elastic vibrations while guaranteeing coordinated motion among the system rigid-body degrees of freedom, and hence the accurate tracking of desired paths through space. The DRC is here applied to damp the oscillation of a load suspended to the moving platform of an Adept Quattro parallel robot by means of a cable.     

A higher level path tracking controller for a four-wheel differentially steered mobile robot

A variety of approaches for path tracking control of wheeled mobile robots have been implemented. While most of these are based on controlling the robot dynamics, they are not applicable if the robot dynamics are inaccessible. In this paper, a fuzzy logic controller (FLC) for the path tracking of a wheeled mobile robot based on controlling the robot at a higher level is presented. The controller is highly robust and flexible and automatically follows a sequence of discrete waypoints, and no interpolation of the waypoints is needed to generate a continuous reference trajectory. The speeds are varied depending on the variations in the path and on the posture of the robot. The heuristic rules of the FLC are based on an analogy with a human driving a car and the optimization of the controller is based on experimentation. The implementation on a P3-AT mobile robot shows the effectiveness of the proposed approach.     

A Case Study of the Collision-Avoidance Problem Based on Bernstein–Bézier Path Tracking for Multiple Robots with Known Constraints

In this paper a case study of a new, cooperative, collision-avoidance method for multiple, nonholonomic robots based on Bernstein–Bézier curves is given. In the presented examples the velocities and accelerations of the mobile robots are constrained and the start and the goal velocity are defined for each robot. This means that the proposed method can be used as a subroutine in a huge path-planning problem in real time, in a way to split the whole path into smaller partial paths. The reference path of each robot, from the start pose to the goal pose, is obtained by minimizing the penalty function, which takes into account the sum of all the path lengths subjected to the distances between the robots, which should be bigger than the minimum distance defined as the safety distance, and subjected to the velocities and accelerations which should be lower than the maximum allowed for each robot. When the reference paths are defined the model-predictive trajectory tracking is used to define the control. The prediction model derived from the linearized tracking-error dynamics is used to predict future system behavior. The control law is derived from a quadratic cost function consisting of the system tracking error and the control effort. The proposed method was tested with a simulation and with a real-time experiment in which four robots were used.     

小车位环境下的自动泊车路径规划与跟踪控制

针对小车位泊车路径设计不连续导致位姿调整不平滑的问题,提出一种回旋曲线、圆弧、直线组合的路径规划方法,并基于非时间参考量的跟踪偏差,设计滑模控制器。根据泊车要求和限制条件,规划出泊入路径与调整路径：泊入路径引导车辆以极限位姿进入车位;调整路径通过平滑的路径组合实现车位内的位姿调整。选用指数趋近率设计滑模控制器,利用连续函数代替趋近率中的符号函数,降低抖振影响。仿真结果表明,车辆能够连续、无突变地完成泊车操作,跟踪误差较小,抖振抑制效果较好。     

Adaptive unified motion control of mobile manipulators

This paper presents a unified motion controller for mobile manipulators which not only solves the problems of point stabilization and trajectory tracking but also the path following problem. The control problem is solved based on the kinematic model of the robot. Then, a dynamic compensation is considered based on a dynamic model with inputs being the reference velocities to the mobile platform and the manipulator joints. An adaptive controller for on-line updating the robot dynamics is also proposed. Stability and robustness of the complete control system are proved through the Lyapunov method. The performance of the proposed controller is shown through real experiments.     

An autonomous vision-based mobile robot

This paper describes the theoretical development and experimental implementation of a complete navigation procedure for use in an autonomous mobile robot for structured environments. Estimates of the vehicle's position and orientation are based on the rapid observation of visual cues located at discrete positions within the environment. The extended Kalman filter is used to combine these visual observations with sensed wheel rotations to produce optimal estimates continuously. The complete estimation procedure, as well as the control algorithm, developed are time independent. A naturally suitable quantity involving wheel rotations is used as the independent variable. One consequence of this choice is that the vehicle speed can be specified independently of the estimation and control algorithms. Reference paths are “taught” by manually leading the vehicle through the desired path. Estimates produced by the extended Kalman filter during this teaching session are then used to represent the geometry of the path. The tracking of taught reference paths is accomplished by controlling the position and orientation of the vehicle relative to the reference path. Time-independence path tracking has necessitated the development of a novel, geometry-based means for advancing along the reference path     

A Smooth Path Tracking Algorithm for Wheeled Mobile Robots with Dynamic Constraints

In order to avoid wheel slippage or mechanical damage during the mobile robot navigation, it is necessary tosmoothly change driving velocity or direction of the mobile robot. This means that dynamic constraints of the mobile robotshould be considered in the design of path tracking algorithm. In the study, a path tracking problem is formulated asfollowing a virtual target vehicle which is assumed to move exactly along the path with specified velocity. The drivingvelocity control law is designed basing on bang-bang control considering the acceleration bounds of driving wheels. Thesteering control law is designed by combining the bang-bang control with an intermediate path called the landing curve whichguides the robot to smoothly land on the virtual target's tangential line. The curvature and convergence analyses providesufficient stability conditions for the proposed path tracking controller. A series of path tracking simulations and experimentsconducted for a two-wheel driven mobile robot show the validity of the proposed algorithm.     

轮式足球机器人平滑运动轨迹控制算法的研究--Robocup系列研究之四

介绍一种轮式足球机器人的平滑运动轨迹控制算法。为了更简洁有效地驱动足球机器人平滑快速地跟踪目标位置与姿态，在控制其移动的过程中应平滑连续地改变其速度和方向。提供了一种基于双积分系统时间最优Bang-Bang控制的轨迹生成及控制算法，在模拟引导轨迹的引导下进行连续的速度控制引导机器人平滑高速跟踪运动轨迹并按要求调整其末端姿态。通过一系列的仿真结果来体现该控制算法的高效性和准确性。     

基于CPLD的彩色视觉移动机器人路径跟踪系统

路径跟踪是机器人视觉导航控制基本技术之一,为使机器人沿地面彩色引导线自主运动,并能在适时离线执行任务后自动返航,提出了一种用可编程逻辑器件(CPLD)实现的视觉伺服PID控制方法.该方法利用图像特征反馈对其所跟踪的路经进行实时识别跟踪.仿真结果表明,该方法改善了控制算法的实时性,提高了移动机器人的路径跟踪精度与速度.