Simultaneous Position Estimation and Omnidirectional Camera Parameter Calibration for Multiple Mobile Robots

This paper proposed an algorithm on simultaneous position estimation and calibration of omnidirectional camera parameters for a group of multiple mobile robots. It is aimed at developing of exploration and information gathering robotic system in unknown environment. Here, each mobile robot is not possible to know its own position. It can only estimate its own position by using the measurement value including white noise acquired by two omnidirectional cameras mounted on it. Each mobile robot is able to obtain the distance to those robots observed from the images of two omnidirectional cameras while making calibration during moving but not in advance. Simulation of three robots moving straightly shows the effectiveness of the proposed algorithm.     

Development of a System for Location Finding of Low-Level Sound Source by Using Human Acoustic System with Stochastic Resonance

The purpose of this study is to develop a system that enables location finding of a small sound. The location finding of a small sound has some difficulties such as high computational costs or disturbances from the ambient noises and reflected waves. The proposed system is composed of a biologically-inspired system which uses a hearing mechanism based on the human ear and a mechanism for perceiving weak signals that uses stochastic resonance. The location finding mechanism in the proposed system is based on the time-lag detecting architecture. On the other hand, the stochastic resonance mechanism can pick up the small sound source in the ambient noises. Using this proposed system, we implemented the location finding of small sounds through numerical simulations and hardware experiments. Good results were obtained for the small sound source location finding.     

Localization of Small Mobile Robot by Low-Cost GPS Receiver

This article deals with a problem of the robot localization in the outdoor environment by using the GPS （global positioning system） data. In order to navigate the robot, it is necessary to transform the global position into the local map in the form of two-dimensional Cartesian coordinate system. The transformation is based on the model of the Earth-WGS 84 reference ellipsoid. The aim of this article is to experimentally evaluate a set of low-cost GPS receivers applicable as position sensors for small outdoor mobile robots. The evaluation is based on series of measurements executed in different times and places. The measured data is processed by given procedure and acquired positions are transformed into the local coordinate system. Accordingly the accuracy of the measured positions is statistically evaluated. The evaluation of used GPS receivers is done by comparison with data acquired by high-end geodetic GPS system Leica 1200, which is used as a reference GPS system.     

Electromagnetic Torque Estimation of a Three-Phase Induction Motor for Setting the Feedrate of a Milling Machine

In this paper, it presents a project of a fuzzy controller and a neural estimator to control a coordinate table powered by three-phase induction motor, aiming to implement an intelligent milling system. The position/speed control is performed using vector techniques of three-phase induction machines. The estimation of the motor electromagnetic torque is used for setting the feedrate of the table. The speed control is developed using TS （Takagi-Sugeno） fuzzy logic model and electromagnetic torque estimation using neural network type LMS （least mean square） algorithm. The induction motor is powered by a frequency inverter driven by a DSP （digital signal processor）. Control strategies are implemented in DSP. Simulation results are presented for evaluating the performance of the system.     

Position control optimization of aerodynamic brake device for high-speed trains

The aerodynamic braking is a clean and non-adhesion braking, and can be used to provide extra braking force during high-speed emergency braking. The research of aerodynamic braking has attracted more and more attentions in recent years. However, most researchers in this field focus on aerodynamic effects and seldom on issues of position control of the aerodynamic braking board. The purpose of this paper is to explore position control optimization of the braking board in an aerodynamic braking prototype. The mathematical models of the hydraulic drive unit in the aerodynamic braking system are analyzed in detail, and the simulation models are established. Three control functions--constant, linear, and quadratic--are explored. Two kinds of criteria, including the position steady-state error and the acceleration of the piston rod, are used to evaluate system performance. Simulation results show that the position steady state-error is reduced from around 12-2 mm by applying a linear instead of a constant function, while the acceleration is reduced from 25,71-3.70 m/s2 with a quadratic control function. Use of the quadratic control function is shown to improve system performance. Experimental results obtained by measuring the position response of the piston rod on a test-bench also suggest a reduced position error and smooth movement of the piston rod. This implies that the acceleration is smaller when using the quadratic function, thus verifying the effectiveness of control schemes to improve to system performance. This paper proposes an effective and easily implemented control scheme that improves the position response of hydraulic cylinders during position control.     

Influence of Tire Dynamics on Slip Ratio Estimation of Independent Driving Wheel System

The independent driving wheel system, which is composed of in-wheel permanent magnet synchronous motor（I-PMSM） and tire, is more convenient to estimate the slip ratio because the rotary speed of the rotor can be accurately measured. However, the ring speed of the tire ring doesn’t equal to the rotor speed considering the tire deformation. For this reason, a deformable tire and a detailed I-PMSM are modeled by using Matlab/Simulink. Moreover, the tire/road contact interface（a slippery road） is accurately described by the non-linear relaxation length-based model and the Magic Formula pragmatic model. Based on the relatively accurate model, the error of slip ratio estimated by the rotor rotary speed is analyzed in both time and frequency domains when a quarter car is started by the I-PMSM with a definite target torque input curve. In addition, the natural frequencies（NFs） of the driving wheel system with variable parameters are illustrated to present the relationship between the slip ratio estimation error and the NF. According to this relationship, a low-pass filter, whose cut-off frequency corresponds to the NF, is proposed to eliminate the error in the estimated slip ratio. The analysis, concerning the effect of the driving wheel parameters and road conditions on slip ratio estimation, shows that the peak estimation error can be reduced up to 75% when the LPF is adopted. The robustness and effectiveness of the LPF are therefore validated. This paper builds up the deformable tire model and the detailed I-PMSM models, and analyzes the effect of the driving wheel parameters and road conditions on slip ratio estimation.     

Secondary Lens Optimization for LED Lamps

The purpose of this paper is to present a methodology for optimizing the geometry of the LED （light emitting diode） secondary lens. The research objective is to uniform the illumination distribution on a target plane for nonimaging application. In order to achieve this, a software that simulates ray tracing is used, in conjunction with a heuristic process for enhancing the optimized parameters that form the geometry of the LED secondary lens. Spherical lenses was opted for optimization due to its lower manufacture complexity.     

Optimal Placement of Phasor Measurement Units Using a Modified Canonical Genetic Algorithm for Observability Analysis

This paper proposes a method for optimal placement of synchronized PMUs （phasor measurement units） in electrical power systems using a MCGA （modified canonical genetic algorithm）, which the goal is to determine the minimum number of PMUs, as well as the optimal location of these units to ensure the complete topological observability of the system. In case of more than one solution, a strategy of analysis of the design matrix rank is applied to determine the solution with the lower number of critical measurements. In the proposed method of placement, modifications are made in the crossover and mutation genetic operators, as well as in the formation of the subpopulation, and are considered restrictive hypotheses in the search space to improve the performance in solving the optimization problem. Simulations are performed using the IEEE 14-bus, IEEE 30-bus and New England 39-bus test systems. The proposed method is applied on the IEEE 118-bus test system considering the presence of observable zones formed by conventional measurements.     

Steering control algorithm for efficient drive of a mobile robot with steerable omni-directional wheels

Omnidirectional mobile robots are capable of arbitrary motion in an arbitrary direction without changing the direction of wheels because they can perform 3-DOF motions on a plane. This paper presents a novel mobile robot design with steerable omnidirectional wheels. This robot can operate in either omnidirectional or differential drive modes, depending on the drive conditions. In the omnidirectional mode, the robot has 3 DOF in motion and 1 DOF in steering, which can function as a continuously variable transmission (CVT). The CVT function can be used to enhance the efficiency of the robot operation by increasing the range of the velocity ratio of the robot velocity to wheel velocity. The structure and kinematics of this robot are presented in detail. In the proposed steering control algorithm, the steering angle is controlled such that the motors may operate in the region of high velocity and low torque, thus operating with maximum efficiency. Various tests demonstrate that the motion control of the proposed robot works satisfactorily and the proposed steering control algorithm for CVT can provide a higher efficiency than the algorithm using a fixed steering angle. In addition, it is shown that the differential drive mode can give better efficiency than the omnidirectionaldrive mode.     

全方位移动机械手运动控制Ⅰ——建模与控制

针对一类由轮式驱动全方位移动平台和机械臂所组成的全方位移动机械手,首先通过对机械结构和运动特性的分析,建立一体化运动学模型,并利用拉格朗日力学法建立动力学模型,分析这两种模型的运动性质.然后根据所建立的模型,分别设计轨迹跟踪控制器,并对控制器的稳定性予以证明.在基于动力学模型的轨迹跟踪控制器中,通过结合全方位移动平台的运动学模型和全方位移动机械手的动力学模型,定量地分析移动平台运动状态对机械臂的耦合作用,并在相应的轨迹跟踪控制器中予以补偿.仿真结果不仅显示所提出两种模型的正确性和相应轨迹跟踪控制器的有效性,而且也说明所述方法可以作为一类移动机械手通用的建模和控制方法.     

基于变分贝叶斯的自适应 PF-SLAM 方法研究

针对移动机器人即时定位与地图构建中时变观测噪声及粒子位置分布对SLAM精度的影响,本文提出基于变分贝叶斯的自适应PF-SLAM算法,采用高斯混合模型对时变的观测噪声建模,并通过变分贝叶斯方法,迭代估算出混合模型中的未知参数;同时根据粒子权值将粒子划分为固定粒子和优化粒子,通过粒子间的近邻拓扑位置关系调整粒子分布,处理时变观测噪声与优化粒子的位置分布,使得优化的粒子集可以更好地表示机器人位置概率分布,实现观测噪声及粒子位置分布自适应。仿真实验表明本算法对比传统PF-SLAM算法定位与地图构建误差降低了76.45%。实际实验表明本算法处理下的环境轮廓误差对比传统PF-SLAM算法的环境轮廓误差减小了61.87%。该算法有效提高了移动机器人的状态估计精度,为移动机器人即时定位与地图构建提供了新的参考。     

一种履带式全方位移动平台的设计与运动学分析

针对轮式全方位移动平台在工程应用中存在振动大及路面适应性差等问题,基于Mecanum轮及传统履带的结构,提出全方位移动履带的结构,并分析全方位移动履带的运动机理;基于全方位移动履带,设计履带式全方位移动平台的布局结构,建立履带式全方位移动平台的逆运动学方程,并根据其判断平台满足全方位运动的必要条件;指出履带式全方位移动平台存在转向滑移问题,分析最大转向滑移率与平台结构参数之间的关系,并提出相应的平台设计准则;基于履带式全方位移动平台的虚拟样机,完成样机横向、斜向及中心转向的运动仿真,通过仿真结果验证履带式全方位移动平台可以实现全方位运动,同时验证平台逆运动学方程的正确性从而为平台的运动控制研究确立理论基础。     

二维合作目标的单相机空间位姿测量方法

针对空间交会对接的近距离位姿测量要求,提出了一种基于单目视觉的二维合作目标位姿解算算法。为方便空中移动平台的调整以满足特定的位姿关系,引入了一种新的姿态角定义方法,此方法定义的三个姿态角可以作为平台姿态调整的反馈量且不受旋转顺序的限制。平面模型相对于相机坐标系的三个姿态角和位置向量可通过平面单应矩阵直接导出。在测量实验中,算法基于DSP平台实现,合作目标由4个共面LED光源构成,测量值基准由高精度倾角传感器和全站仪获得。对空间位置变化范围为2m×2m,姿态角变化范围为-30°~30°的目标平面进行测量,结果表明,本算法可实现0.88%的相对位置定位误差和最大为0.996°的姿态角测量误差,且单帧算法的解算速度仅为0.25ms。     

一种全方位移动机械手的可操作度分析

将机械手可操作度的概念推广到移动机械手，定义了广义可操作度。建立了基于全方位移动平台的移动机械手的广义运动学模型。在广义可操作度概念的基础上，分析了全方位移动平台对机械手奇异位姿、可操作度及方向可操作度的影响，并与受非完整约束的差分移动平台对机械手的相应影响进行了比较。     

大视场室内移动机器人高精度动态定位方法

高精度室内定位是移动机器人实现自主导航、运动控制和协同作业等任务的前提条件.利用单目视觉定位原理,提出了一种针对大视场的室内移动机器人绝对定位方法.该方法适用于室内多移动机器人同步动态定位,解决了大视场环境下多相机非线性标定和视场融合问题,相机标定精度提高了52.6％.为提高移动机器人动态定位精度,设计了基于光信标的高...     

一种履带式全方位移动平台的平顺性分析

针对Mecanum轮式全方位移动平台存在路面适应性差等问题,提出了“全方位移动履带”的结构,并研制出一种履带式全方位移动平台;研究了履带式全方位移动平台的运动平顺性,分别建立了履带式和Mecanum轮式全方位移动平台的虚拟样机,主要完成了两种样机在B~F级不平路面的纵向及横向运动仿真试验;分析了两种样机纵向及横向运动的平顺性,结果表明,履带式全方位移动平台的运动平顺性优于Mecanum轮式全方位移动平台,并总结了路面等级对其纵向及横向运动平顺性的影响规律;在一段土路（相当于C级路面）上完成了平台的平顺性试验,试验结果验证了仿真结果的正确性;因此,履带式全方位移动平台可以改善Mecanum轮式全方位移动平台的路面适应性。     

基于PF算法的移动机器人定位研究

针对移动机器人的智能化要求,提出了一种应用粒子滤波（PF）进行机器人定位的方法。通过分析激光雷达的识别观测模型和履带式机器人本体的运动特点,建立基于最优贝叶斯估计的PF位姿估计算法框架,避免了传统EKF定位算法在非线性系统应用中需要近似线性化、求取复杂雅克比矩阵等问题。在搭建的室内平台上进行了现场定位实验,结果表明该算法定位准确、稳定,具有更广泛的适应性。     

考虑打滑干扰的解耦式主动脚轮全向移动机器人跟踪控制

基于解耦式主动脚轮的全向移动机器人系统,提出了一种考虑未知脚轮打滑的轨迹跟踪控制方法。建立了包含脚轮打滑情况的全向移动机器人运动学模型,利用附加传感器获得的冗余信息对滑动参数进行估计;根据反步法设计轨迹跟踪控制器,利用Lyapunov定理证明闭环系统的稳定性,并依据极点配置的方法实现控制参数的整定。仿真与实验结果表明：该控制方法能够使全向移动机器人在复杂室内地面稳定地跟踪设定轨迹。     

一种轮式移动机器人实时速度估计方法

环境和机器人自身的不确定性影响轮式移动机器人的轨迹跟踪控制性能,此时仅仅使用里程计往往不能正确表达机器人的状态信息。在无速度传感器的情况下,讨论了使用加速度传感器和位置传感器的输出实时估计轮式移动机器人的速度。首先使用滑模观测器进行里程计信号处理,然后对车体加速度信号进行带通滤波提取车体扰动信息,通过频域融合信号表达轮式移动机器人的速度,并针对正交轮式全方位移动机器人进行了轨迹跟踪控制研究。试验结果表明采用融合数据可以更准确提供机器人的状态信息并得到更好的控制性能。