The performance of automatic guided vehicles (AGVs) is gauged by their position and orientation errors. Sometimes the orientation errors are not measurable, and output feedback using position errors only is employed. In this paper, a controller using output feedback is proposed for a differential-wheel-drive AGV with a simple linear array of 64/spl times/1 opto-sensors. A linear controller is first developed. The performance of the linear controller is further improved using fuzzy logic. Two fuzzy-logic controllers are accordingly formed. Stability based on the Hurwitz criterion, the Popov criterion, and the phase-plane method is demonstrated. Experimental results using a laboratory AGV are provided to illustrate the effectiveness of the proposed controllers.