This is Electric Machine Drives subject
Crane operation has always had two simply stated objectives: get the crane to the load, then move the load somewhere; and do it safely and efficiently. In the past, crane movements were actuated either by a cab-mounted operator guided by hand signals from a floor walker, or by pushbutton pendants hanging from the crane and controlled by someone on the floor. While pendant control solves some of these problems by bringing crane control closer to the load, there are still problems. The pendant is on the wrong side of the crane half the time, even with the convenience of festooning across the bridge. Or the pendant could be dropped from the hoist.
Re additional details Electric motors turn a drum to wind and unwind a cable to raise and lower the hoist. Other motors are used to move the hoist horizontally. Cranes usually have a motor on each end of the trolly to drive the wheels that move it back and forth. A motor drives the traverse mechanism to position the hoist from side to side. Electronic controllers control the speed, direction and torque of the motors.
