Fault-tolerant Coordinated Motion Control for a Modular Mobile Robot

本课题对模块化移动机器人的容错控制进行了研究。主要研究内容如下：1.设计了一种基于分散式数据关联的机器人三维航位推算系统。提出了基于信息滤波、协方差交集和无迹变换的航位推算算法。该算法为航位推算系统带来了高度的模块化和可扩展性。针对机器人在起伏区域的运动，设计了一种运动控制系统。运动控制系统由底盘单元控制器和轮单元控制器组成，底盘单元控制器决定机器人的期望运动，而每个轮单元控制器控制各自的移动底座和底盘倾斜机构以产生机器人期望的运动。该控制系统使机器人能够保持底盘在水平位置，同时在起伏区域跟踪其规定的路径。设计了一种基于多模型的内部传感器故障检测与诊断系统。对每个传感器的三种故障模式(硬故障、噪声故障和尺度故障)进行了处理。在变结构交互多模型算法和卡尔曼滤波的基础上，提出了FDD算法。将FDD算法嵌入到模块化机器人的航位推算系统中。它允许机器人在传感器故障的情况下进行稳健的自我定位。设计了一种模块化机器人容错控制系统。对两个驱动/转向单元的传感器和执行器硬故障进行了处理。故障检测和诊断通过交互多模型估值器和启发式规则来实现。基于Ackerman几何，设计了容错控制器。该控制系统实现了机器人在传感器/执行器故障情况下的安全运动。

This project studied a fault-tolerant control for a modular mobile robot. The project is concluded as follows:1. A 3D dead reckoning system for the robot was designed based on a decentralized data association. The dead reckoning algorithm is formulated based on the information filter, the Covariance Intersection and the unscented transformation. This algorithm brings highly modularity and extendibility in the dead reckoning system.2. A motion control system was designed for the robot moving on undulating area. The motion control system consists of chassis-unit controller and wheel-unit controller; the chassis-unit controller decides the desired motion of the robot, while each of wheel-unit controllers controls its own mobile base and chassis tilting mechanism to produce the desired motion of the robot. The control system makes it possible to keep the chassis in a horizontal position while the robot tracking its prescribed path on undulating area.3. A multi-model based fault detection and diagnosis (FDD) system of internal sensors was designed. Three fault modes (hard fault, noise fault, and scale fault modes) of each sensor are handled. The FDD algorithm is formulated based on the variable structure interacting multiple-model algorithm and the Kalman filter. The FDD algorithm is embedded into the dead-reckoning system of our modular robot. It allows the robust self-localization of the robot subject to sensor faults.4. A fault-tolerant control system for a modular robot was designed. The hard fault of sensors and actuators in two drive/steering units is handled. The fault detection and diagnosis are achieved via the interacting multiple-model estimator and heuristic rule. A fault-tolerant controller is designed based on the Ackerman geometry. The control system achieves the safe motion of the robot subject to sensor/actuator fault.