| Robots have been used in manufacturing and service industries to improve productivity, quality, and flexibility. Robots are usually mounted on a fixed plate, or on rails, and can move in a limited manner. The success of robots in these environments encourages the use of mobile robots in other applications where the environments are not structured, such as in outdoor environments.; This dissertation presents the development of an autonomous navigation and obstacle avoidance system for a Wheeled Mobile Robot (WMR) operating in unstructured outdoor environments. The algorithm produces the robot's path positioned within the road boundaries and avoids any fixed obstacles along the path. The navigation algorithm was developed from a feedforward multilayer neural network. The network used a quasi-Newton backpropagation algorithm for training.; Proportional-plus-derivative computed-torque, proportional-plus-integral-plus-derivative computed-torque, digital, and adaptive controllers were developed to select suitable control torques for the motors, which cause the robot to follow the desired path from the navigation algorithm.; Simulation software permitting easy investigation of alternative architectures was developed by using Matlab and C++. The simulation software for the controllers was developed for two case studies. The first case study is the two-link robot manipulator, and the second is a navigation controller for the WMR. The simulation software for the WMR navigation controller used the Bearcat III dynamic model, developed in this dissertation.; Simulation results verify the effectiveness of the navigation algorithm and the controllers. The navigation algorithm was able to produce a path with a small mean square error, compared to the targeted path, which was developed by using an experienced driver. The algorithm also produced acceptable results when tested with different kinds of roads and obstacles. The controllers found suitable control torques, permitting the robot to follow these paths. The digital controller produced the best results.; The significance of this work is the development of a dynamic system model and controllers for WMR navigation, rather than robot manipulators, which is a new research area. In addition, the navigation system can be utilized in numerous applications, including various defense, industrial and medical robots. |
