JPH0612485B

PURPOSE:To ensure the effective operation of a system by enabling a carrier got out of its course to set on the course again by itself after moving back by a fixed distance. CONSTITUTION:In a normal stop stage a carrier 1 stops in the direction where the shift value of the carrier body increases if the carrier 1 moves forward as it is as shown by a position P2, i.e., in the outer direction. When the carrier 1 is straightly moved back under such conditions, the carrier 1 reaches again a position P3 set on a course. In this case, the carrier 1 is set back to its steering enable range in most cases as long as the carrier 1 is driven back by a distance (lB+lC) where lB and lC mean a braking distance and a fixed distance respectively. Thus both the shift value and the direction of the carrier body can be corrected by driving forward the carrier 1 by a fixed distance lD at a low speed while steering. Then the carrier 1 reaches a position P4. If the carrier 1 gets out of its course again while the carrier 1 is moving forward at a slow speed, the carrier 1 is set again on its course just by repeating the same operation. As a result, the manual operations are extremely decreased to set back the carrier 1 to its course and the effective system operation is attained. In addition, a fail-safe system is realized with higher reliability.