Kinematic Modeling and Analysis of Skid-Steered Mobile Robots With Applications to Low-Cost Inertial-Measurement-Unit-Based Motion Estimation

Skid-steered mobile robots are widely used because of their simple mechanism and high reliability. Understanding the kinematics and dynamics of such a robotic platform is, however, challenging due to the complex wheel/ground interactions and kinematic constraints. In this paper, we develop a kinematic modeling scheme to analyze the skid-steered mobile robot. Based on the analysis of the kinematics of the skid-steered mobile robot, we reveal the underlying geometric and kinematic relationships between the wheel slips and locations of the instantaneous rotation centers. As an application example, we also present how to utilize the modeling and analysis for robot positioning and wheel slip estimation using only low-cost strapdown inertial measurement units. The robot positioning and wheel slip-estimation scheme is based on an extended Kalman filter (EKF) design that incorporates the kinematic constraints for accuracy enhancement. The performance of the EKF-based positioning and wheel slip-estimation scheme are also presented. The estimation methodology is tested and validated experimentally on a robotic test bed.     

Decentralized Motion Planning for Multiple Mobile Robots: The Cocktail Party Model

This paper presents an approach for decentralized real-time motion planning for multiple mobile robots operating in a common 2-dimensional environment with unknown stationary obstacles. In our model, a robot can see (sense) the surrounding objects. It knows its current and its target's position, is able to distinguish a robot from an obstacle, and can assess the instantaneous motion of another robot. Other than this, a robot has no knowledge about the scene or of the paths and objectives of other robots. There is no mutual communication among the robots; no constraints are imposed on the paths or shapes of robots and obstacles. Each robot plans its path toward its target dynamically, based on its current position and the sensory feedback; only the translation component is considered for the planning purposes. With this model, it is clear that no provable motion planning strategy can be designed (a simple example with a dead-lock is discussed); this naturally points to heuristic algorithms. The suggested strategy is based on maze-searching techniques. Computer simulation results are provided that demonstrate good performance and a remarkable robustness of the algorithm (meaning by this a virtual impossibility to create a dead-lock in a random scene).     

动态滑模控制及其在移动机器人输出跟踪中的应用

针对轮式移动机器人的输出跟踪问题,提出一种动态滑模控制方法,首先给出机器人的动力学简化模型,然后将其分解成两个低阶子系统,并给出其输出跟踪的动态滑模控制器设计方法,仿真试验表明该方法能明显地削弱滑模控制系统的抖振。     

基于Fuzzy-PID的移动机器人运动控制

移动机器人涉及到许多研究方向,运动控制是其中的基础。通过对移动机器人运动学模型进行分析,以足球机器人系统为实验平台,论证了Fuzzy-PID技术应用于移动机器人运动控制的可行性。将传统的PID控制与模糊控制相结合,通过PID控制实现控制的准确性,利用模糊控制提高控制的快速性。针对移动机器人运动控制中的实际问题,着重提出了基于误差分区的PID控制器和模糊控制器的设计方法。实验证明该方法不仅增强了控制器的调节能力,还在一定程度上简化了控制器的设计。     

轮式移动机器人预见预测运动控制

针对移动机器人的运动控制问题,该文采用预见预测控制方法加以解决。利用三阶Bezier曲线作为路径生成器生成目标轨迹,并据此设计了最优预见控制器作为系统的前馈补偿;使用扩展卡尔曼滤波器作为预测模型,基于广义预测控制(GPC)实现了PPC运动控制器的设计。仿真实验结果证明了该方法的有效性。     

实现机器人随动的红外感知方法

结合机器人随动任务对人体运动定位的需求,提出一种分层递阶结构的红外运动感知模式,及基于热释电红外传感器的物理实现方法.在传感模型方面,采用两层递阶结构的感知模式:底层为由多个几何传感单元构成的几何传感层,在机器人视野内实现多视角运动目标的方位测量;上层为协作感知层,用来组织底层各几何传感单元的协作,实现运动目标的定位测量.在物理实现方面,底层组合热释电红外传感阵列与菲涅尔透镜组,构建运动目标方位角测量所需的几何传感单元;上层以最小二乘优化准则作为融合多视角方位测量信息的手段,获得运动目标的位置信息.移动机器人随动实验结果验证了所提出感知方法的有效性.较多视角光学视觉传感技术,该方法在传感效率、对光照和环境变化的稳健性、低成本和低功耗等方面具有不可替代的优势.     

多移动机器人实时最优运动规划

研究多移动机器人的实时运动规划问题，提出了运动规划问题的体系结构，并将最优控制与智能决策相结合，建立实时专家系统，在其支持下，使机器人在时间—能量最优情况下完成规划策略。仿真结果表明该方法具有很强的实时性。     

轮式移动机器人与地形交互运动仿真研究

分析了轮式移动机器人（WMR）在不平坦的三维地形上运动的运动学模型,利用速度投影法,得到了一种WMR运动模型的新的形式。基于虚拟现实技术,利用VC + +OpenGL实现了WMR虚拟漫游系统。该系统具有较强的交互性和实时性,为星球探测机器人虚拟导航、遥操作提供了验证平台。     

Fuzzy Motion Planning of Mobile Robots in Unknown Environments

A fuzzy algorithm is proposed to navigate a mobile robot from a given initial configuration to a desired final configuration in an unknown environment filled with obstacles. The mobile robot is equipped with an electronic compass and two optical encoders for dead-reckoning, and two ultrasonic modules for self-localization and environment recognition. From the readings of sensors at every sampling instant, the proposed fuzzy algorithm will determine the priorities of thirteen possible heading directions. Then the robot is driven to an intermediate configuration along the heading direction that has the highest priority. The navigation procedure will be iterated until a collision-free path between the initial and the final configurations is found. To show the feasibility of the proposed method, in addition to computer simulation, experimental results will be also given.     

基于规则的移动机器人实时运动规划

研究移动机器人在动态环境中的导航与避障问题。为提高规划的实时性,提出了基于规则的规划方法,将多移动障碍环境机器人的运动规划分解为相对简单的单移动障碍运动规划,利用最优控制来实现单障碍的最优避障,并用智能搜索方法解决了移动机器人在多移动障碍环境中的实时运动规划问题。仿真实例表明了该方法的有效性。     

基于运动描述语言的轮式移动机器人控制

介绍了一种基于运动描述语言的轮式移动机器人控制方法．运动描述语言不仅可以有效地描述机器人系统中离散和连续动力学过程的相互作用,而且可以定量地描述操纵机器人的复杂性．利用该方法对具有非完整约束的轮式移动机器人的位姿镇定问题进行了研究,仿真结果验证了该方法的有效性．     

Dynamic Motion Planning for Mobile Robots Using Potential Field Method

The potential field method is widely used for autonomous mobile robot path planning due to its elegant mathematical analysis and simplicity. However, most researches have been focused on solving the motion planning problem in a stationary environment where both targets and obstacles are stationary. This paper proposes a new potential field method for motion planning of mobile robots in a dynamic environment where the target and the obstacles are moving. Firstly, the new potential function and the corresponding virtual force are defined. Then, the problem of local minima is discussed. Finally, extensive computer simulations and hardware experiments are carried out to demonstrate the effectiveness of the dynamic motion planning schemes based on the new potential field method.     

Energy Consumption Optimization for Mobile Robots Motion Using Predictive Control

Operation of mobile robots in off-road environment requires the attention to the torque saturation problem that occurs in the wheels DC motors while climbing hills. In the present work, off-road conditions are utilized to benefit while avoiding torque saturation. Energy optimization algorithm using predictive control is implemented on a two-DC motor-driven wheels mobile robot while crossing a ditch. The predictive control algorithm is simulated and compared with the PID control and the open-loop control. Predictive control showed more capability to avoid torque saturation and noticeable reduction in the energy consumption. Furthermore, using the wheels motors armature current instead of the supply voltage as control variable in the predictive control showed more efficient speed control. Simulation results showed that in case of known ditch dimensions ahead of time, the developed algorithm is feasible. Experimental examination of the developed energy optimization algorithm is presented. The experimental results showed a good agreement with the simulation results. The effects of the road slope and the prediction horizon length on the consumed energy are evaluated. The analytical study showed that the energy consumption is reduced by increasing the prediction horizon until it reaches a limit at which no more energy reduction is obtained. This limit is proportional to the width of the ditch in front of the mobile robot. Curve fitting is applied to the obtained results to address further the effect of the parameters on the energy consumption.     

Sensor-Based Motion Planning of Wheeled Mobile Robots in Unknown Dynamic Environments

This paper presents a new sensor-based online method for generating collision-free paths for differential-drive wheeled mobile robots pursuing a moving target amidst dynamic and static obstacles. At each iteration, the set of all collision-free directions are calculated using velocity vectors of the robot relative to each obstacle, forming the Directive Circle (DC), which is the fundamental concept of our proposed method. Then, the best feasible direction close to the optimal direction to the target is selected from the DC, which prevents the robot from being trapped in local minima. Local movements of the robot are governed by the exponential stabilizing control scheme that provides a smooth motion at each step, while considering the robot’s kinematic constraints. The robot is able to catch the target at a desired orientation. Extensive simulations demonstrated the efficiency of the proposed method and its success in coping with complex and highly dynamic environments with arbitrary obstacle shapes.     

A Discrete Method for Time-Optimal Motion Planning of a Class of Mobile Robots

This paper addresses the time-optimal motion planning (TOMP) problem between two configurations for a mobile robot with two independently driven wheels. Different from previous methods, in which one needs to solve a set of differential equations, a discrete method is proposed to solve this problem. The first step is to transform the TOMP problem into a nonlinear programming (NLP) problem by an iterative procedure, in which the sampling period and the control inputs are chosen as variables, and the traveling time is to be minimized. Since it is usually hard to find initial feasible solutions of an NLP problem, a method that combines the concepts of genetic algorithms (GAs) and penalty functions is also proposed. In this manner, the NLP problem can be solved since initial feasible solutions can be generated easily. Simulation results are included to show the validity of the proposed method.     

Coordinated Collective Motion of Groups of Autonomous Mobile Robots with Directed Interconnected Topology

Coordinated collective motion of groups of autonomous mobile robots is studied. A qualitative analysis for the collective dynamics of multiple autonomous robots with directed interconnected topology using nearest neighbor rules is given. A necessary and sufficient graphical condition is proposed to guarantee that the headings of all robots converge to the same heading. The graph having a globally reachable node plays a crucial role in convergence analysis. Furthermore, we show that the globally reachable node having no neighbors serves as a group leader as a special case Supported in part by National Natural Science Foundation of China under the grant 60604001 and 60674081, Natural Science Research Project of Hubei Provincial Department of Education under the grant D20081306 and Scientific Innovation Team Project of Hubei Provincial College under the grant T200809.     

基于动力学模型的轮式移动机器人电机控制

针对移动机器人两路电机协同控制问题,提出基于动力学模型的轮式移动机器人电机控制律 （DMMC）．首先推导出质心位置不一定在几何中心的移动机器人运动学模型和动力学模型,并求解出两轮速 度与力矩之间的非线性微分方程．然后,基于两轮速度与力矩间非线性微分方程、电机电气方程和电机机电 方程,推导出移动机器人系统状态方程．最后采用极点配置得到I 型状态反馈控制律．仿真显示,DMMC 法实 现了对输入指令的零稳态误差快速响应．     

Navigation of Multiple Kinematically Constrained Robots

In this paper, we propose a methodology for implementing multirobot navigation-function-based controllers to mixed teams of holonomic and nonholonomic agents. A new nonsmooth backstepping controller is introduced for translating kinematic controllers to equivalent dynamic ones, while maintaining bounded velocity specifications. The derived backstepping controller is applied to a dynamic model of the mobile robots, yielding a globally asymptotically stable dynamic controller. The effectiveness of the methodology is verified through nontrivial computer simulations.     

Adaptive Polar-Space Motion Control for Embedded Omnidirectional Mobile Robots with Parameter Variations and Uncertainties

This paper presents an adaptive polar-space motion controller for trajectory tracking and stabilization of a three-wheeled, embedded omnidirectional mobile robot with parameter variations and uncertainties caused by friction, slip and payloads. With the derived dynamic model in polar coordinates, an adaptive motion controller is synthesized via the adaptive backstepping approach. This proposed polar-space robust adaptive motion controller was implemented into an embedded processor using a field-programmable gate array (FPGA) chip. Furthermore, the embedded adaptive motion controller works with a reusable user IP (Intellectual Property) core library and an embedded real-time operating system (RTOS) in the same chip to steer the mobile robot to track the desired trajectory by using hardware/software co-design technique and SoPC (system-on-a-programmable-chip) technology. Simulation results are conducted to show the merit of the proposed polar-space control method in comparison with a conventional proportional-integral (PI) feedback controller and a non-adaptive polar-space kinematic controller. Finally, the effectiveness and performance of the proposed embedded adaptive motion controller are exemplified by conducting several experiments on steering an embedded omnidirectional mobile robot.     

一种适用于移动机器人的障碍物快速检测算法及其实现

针对传统的用于机器人检测障碍物的算法存在的不足,提出了一种基于视觉传感器与超声波传感器信息融合的快速障碍物检测算法.该算法通过位十机器人头部的超声波传感器获取机器人到障碍物(本算法采用矩形障碍物)的距离信息,通过改进型快速直线检测方法和约束条件确定障碍物在视觉传感器所采集的图像中的直线边缘,根据成像过程中-三角形相似的...