Guidance of an autonomous guided vehicle using low-level ultrasonic and odometry sensor systems

Abstract

A method of guidance is described for an autonomous guided vehicle (AGV) operating in a pre-defined and structured environment such as a warehouse or factory. The guidance system requires a series of data describing concatenated curved and straight-line segments to be passed to the vehicle as a representation of a planned path within its environment. The coordinate position of each line segment, the associated AGV direction, and the demand speed constitute a series of commands which are queued and then executed in sequence. In order to execute commands, the AGV is equipped with two-level sensor systems, ultrasonic transducers and odometry, which allow it to estimate and correct its global position continually. In addition to a queue of commands, the AGV also has a pre-programmed knowledge of the position of a number of correction boards within its environment. When the AGV passes such a correction board, it can measure its position relative to the board in the local frame of the board. This is then transformed into a global position correction. Position corrections appear as step disturbances to the control system. The control system is arranged so that it allows the vehicle to move back on to its planned trajectory after a position correction in a critically damped fashion.