Abstract: In an apparatus for controlling operation of an automatic door with minimum error in a detected door position, a motion sensor is positioned relative to a movable driving member coupled to the door. Pulses having a pulse repetition rate are created in direct proportion to a velocity of movement of the driving member. The pulses are counted and current position of the door determined. Any error arising from a loss or slip in an intermediate transmission mechanism which couples a motor with the final driving member is substantially eliminated. A pair of motion sensing elements as opto-electronic couplers may be provided for sensing a phase relationship between the sensing elements defining a direction of door movement. A pulse interval monitor adapted to generate a signal indicative of a long lapse of time between adjacent pulses from the sensing element may be provided. A sequence control circuit responsive to this generated signal generates a stop command for the motor.

Abstract: An apparatus for use in an automatic door system. Means are provided which compares the current position of the running door with a deceleration point to generate a low speed command upon their coincidence. A speed control responds to decelerate the door to a selected low speed. A measuring device measures a variable run-length of the door which is subject to variations in the mechanical condition of the door. In one embodiment, the device measures a low speed run-length over which the door has moved at a low speed. A comparator compares the measured low speed run-length with a preselected optimal low speed run-length to obtain error or departure from the optimal value. A correction logic produces an updated deceleration point by removing the error from the former deceleration point.