Fail-free actuator assembly

摘要

An electro-mechanical actuator has two motors which normally operate at the same speed and combine (sum) to move a load via a rotary actuator output member. If the motors begin to operate at different speeds, this indicates that the system has failed, and the output member is automatically decoupled from the remainder of the actuator. This leaves the output member free to rotate relative to the remainder of the actuator. The speeds of the motors are monitored by a differential mechanism which produces a rotary output proportional to the average of the two motor speeds. This average is normally the same as the speed of the output member. Decoupling of the output member occurs when this average deviates from the output member speed.