Discussion and realization of safety device for stop-hold robot operation.

Abstract

The machine of the man-machine system must be fail-safe to assure the safety of the human and a fail-safe interlock must be provided to allow the machine to perform the intended operation only when the human absent in the work area of the machine. But, as the matter of fact, a human operation such as trouble-shooting or maintenance is conducted under stop-hold condition of the machine. This paper addresses, such a system that a human operation can safely work with an industrial robot stop-holding in the common work area. The paper first shows a principle of safe work in a man-machine (robot) system. Described next is a prototype safety device (safety hold device) that actuates when the human works in close proximity to the movable part of robot in the stop-hold condition. Described last is fail-safe construction of the device. On the basis of the fail-safe logic, the safety device is so constructed that an erroneous operation signal produced by the safety device cannot permit the stop-hold operation and any malfunction of the device make a shut-off of the power source.