How is the speed of three pumps synchronised on a drilling rig?
An independent servo actuator and potentiometer is used for each pump. The operator sets the three speeds separately from a single cabin; because there is no mechanical linkage, one does not affect the other.
Adjusting three pumps separately with a mechanical lever linkage is hard in the field and the settings drift into one another. In the electronic solution the throttle lever of each pump is driven by its own servo actuator.
The three potentiometers in the cabin set the three speeds independently. Because there is no mechanical link, the setting of one pump does not upset another; the settings do not drift with vibration.
Full topic: Why is constant speed important on a generator?