Automatic locomotive speed control

Abstract

An automatic speed control system for a consist of diesel locomotives conserves fuel by throttling back trailing engines and operating remaining engines at the most efficient throttle position. A control unit in the lead locomotive is operated by the engineer to command control units in equipped trailing locomotives of the consist. In the lead locomotive, depressing a 'set speed' push button causes a speed memory to store the existing speed of the consist, and a cutout control signal is generated which is transmitted to trailing units in serial order, i.e., front to rear, by a single spare trainline wire. The control signal has two control voltage levels that increase or decrease with deviations of the speed of the consist from the desired speed in memory. These voltage levels are decoded by each trailing unit and, if power is needed, the engine throttle is set at the most efficient position or, if the locomotive is to be cut out, the throttle is set at a desired minimum position. The trailing units also cause these voltage levels to drop by a fixed amount (equivalent to a predetermined speed increase) as the control signal is conducted by the trainline wire rearwardly in the consist from each trailing unit to the next succeeding trailing unit. In this manner, engines are successively throttled back from the rear of the consist and returned to the higher throttle position from the front to maintain the desired train speed. A hold mode permits the automatic control system to be temporarily disabled without clearing the speed memory or changing the control signal, and depressing a 'resume speed' push button on the lead unit reestablishes automatic speed regulation.