Cost efficient control of a plurality of motor drives has been a goal of most drive system suppliers. In the distant past, such efficiency was achieved mechanically by a motor driving a line shaft having gears and pulleys attached thereto to drive apparatus at various work stations. A more modern approach utilizes a motor at each work station, thus eliminating the line shaft, but such an approach requires synchronization of the control apparatus associated with each motor. In effect, the control apparatus provides an "electronic line shaft" to ensure drive synchronization. Such approaches typically also require extremely long control wiring and power wiring runs from a central controller to each of the motors. This is particularly the case if the motors are located in a hostile environment requiring that the control apparatus be located some distance away in a more desirable environment. Such long wiring runs are susceptible to losses and to radio frequency interference. In addition, such long wiring runs are extremely expensive to install and maintain.
In view of the foregoing, it has become desirable to develop a synchronization system for a plurality of motors wherein the wiring from the control apparatus and power apparatus to the motor is minimized and wherein any communication from the control and/or power apparatus to a drive controller is over fiber optic cables thus eliminating the problems associated with long wiring runs and radio frequency interference.
USPTO Backgrounds
USPTO Backgrounds