Abstract: An automatic travel control method for a unmanned vehicle system is performed on the basis of signals indicating the existence of the curvature of a guide path and right and left digital signals indicating the degree of the curvature of the guide path. In the method, (1) where the guide path is straight, the steering of the vehicle is controlled based on both the right and left digital signals; (2) where the guide path is curved to the right, the steering of the vehicle is controlled based on the right digital signal; and (3) where the guide path is curved to the left, the steering of the vehicle is controlled based on the left digital signal. The curvature existence detecting operation is performed according to the levels of the voltage signals induced to a pair of voltage generating devices located at the right and left sides of the vehicle after generating a magnetic field by applying alternating current to the guide path.

Abstract: A microwave oven having a heater apparatus has an upper heater installed to an upper portion of a cooking chamber for transmitting heat toward the center of the cooking chamber. A bracket is fixed to a side plate of the cooking chamber and has a pair of lugs spaced apart from each other by roughly 60.degree. along the swinging direction of the upper heater. A bushing is fitted into the bracket to be rotatable therein, and is pierced with the upper heater along the rotating shaft line. A guiding plate formed with a groove is fixed to the bushing. A lower heater is installed to a bottom plate of the cooking chamber to be shaped as an alphabet "U," and a turntable is coated with a ceramic. Thus, the swinging angle of the upper heater is controlled to adjust a distance from food, and the upper plate of the cooking chamber is cleaned by easily swinging the upper heater. The lower heater bakes the lower side of food to consistently cook the food.