| 摘要 |
PURPOSE:To perform precise and speedy switching from automatic reaping height control by automatically putting a manual reaping height control mechanism in operation when the frequency of fault occurrence reaches a set value. CONSTITUTION:A mechanism 28 decides on whether a detected value by a sensor utilizing an ultrasonic wave is normal or not while an automatic reaping height control mechanism 13 is in operation. When the detected value is abnormal, a mechanism 19 performs automatic switching from the operation of the mechanism to that of a manual reaping height control mechanism 14 once the frequency of the occurrence of said abnormal value reaches a set value within a set time. Consequently, variance in reaping height due to switching delay and a failure in switching is suppressed because of the precise and speedy switching from the automatic to the manual reaping height control state. |
