Coordinated Control for a Non-Holonomic Modular Omnidirectional Mobile Robot

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This project studied a coordinated control for a non-holonomic modular omnidirectional mobile robot, in which wheel units assembled are modularized on their mechanisms and controllers, so that we can easily tailor the robot to individual transfer applications. The project is concluded as follows :1. A dead reckoning system for the robot was designed based on the extended Kalman filter. The dead reckoning system can precisely identify the robot position and the wheel radius of each wheel unit. The accurate estimation in the wheel radius succeeds in reducing the motion interactions among the wheel units.2. A motion control system was designed to coordinate wheel units and to ensure correct robot motion. In the control system, a path-tracking controller decides the desired motion of the robot based on the Ackerman geometry to track its reference path, while the coordinated controller controls wheels to produce the desired motion of the robot. To reduce motion interactions among the wheel units, we constituted two types of wheel units : active wheel units and passive wheel units. The active wheel units produce the desired robot motion, and the passive wheel units correct their own velocities to mimic caster behavior.3. The performance of the dead reckoning and motion control systems was evaluated through both simulations and experiments.4. A motion control system consisting of path-tracking and chassis-tilting controllers was designed for a modular omnidirectional vehicle equipped with chassis-tilting mechanisms. The control system can prevent the robot from tumbling by centrifugal acceleration while the robot following a predetermined path. A dead reckoning system for the robot was also designed.5. As the first step toward applying the proposed methods to real robots, a dead reckoning system for a large omnidirectional AGV in outdoor environments was designed, and the performance was evaluated through fundamental experiments.