In this paper, the wall-following problem of an AGV is characterized by keeping a constant distance from a wall. Four Polaroid ultrasonic range sensors (sonar) are used to obtain information of the distance between the AGV and the wall. Four sonars are divided into two groups being placed at the front and back end on the right side of the AGV, respectively. A digital filter is used to get rid of disturbance and wrong readings. The former results mainly from the door and the latter from the specular reflection and accidental scattering. To obtain good dynamic and steady performances, a new compound fuzzy-I control algorithm is presented. Our methods have been verified by following a 15-meter-long wall with one door by using our TIT-1 AGV (TIT: Tianjin Institute of Technology). The results show a good performance with an error of ±2 cm from the desired distance to the wall.