In this paper, the development of an unmanned autonomous forklift is discussed. A system configuration using vision, laser ranger finder, sonar, etc. for autonomous navigation is presented. The kinematics of a spin-turn mechanism is analyzed first, and then the obtained kinematics equations are transformed to the equations represented by path variables. These equations are nonlinear state equations to be used for control purposes. A time varying feedback control law via the chained form of Murray and Sastry [12] is derived. The effectiveness of the proposed control law is examined through simulations and experiments.
A key feature of an autonomous vehicle is the ability to re-plan its motion from a starting configuration (position and orientation) to a goal configuration while avoiding obstacles. Moreover, it should react robustly to uncertainties throughout its maneuvers. We present a predictive approach for autonomous navigation that incorporates the shortest path, obstacle avoidance, and uncertainties in sensors and actuators. A car-like robot is considered as the autonomous vehicle with nonholonomic and minimum turning radius constraints. The results (arcs and line segments) from a shortest-path planner are used as a reference to find action sequence candidates. The vehicle's states and their corresponding probability distributions are predicted to determine a future reward value for each action sequence candidate. Finally, an optimal action policy is calculated by maximizing an objective function. Through simulations, the proposed method demonstrates the capability of avoiding obstacles as well as of approaching a goal. The regenerated path will incorporate uncertainty information.
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