Control systems mainly differ because of feedback. While open loop systems allow signals to travel from control to motor without any guarantee against errors, close loop systems send another set of signals back to control for information about operation success or failure.
Feedback sensors ensure reliable, smooth, and accurate operation. They generally fall into absolute, relative, or intermediate types depending on how they report information. While absolute sensors report position within a single electrical cycle, incremental sensors provide output pulses for each motion without reference to location.
These devices are specifically designed for linear, rotational, or a mixture of motions, with differences in mounting features and directions. From tachometers to Hall sensors, encoders, and resolvers, feedback sensors make it possible to eliminate errors from transmission and guarantee greater control.
Feedback can also be provided by vision systems, from simple sensors to elaborate vision systems with industrial cameras for image capture and sophisticated software for analysis.