Resolver

旋转变压器（旋变）Advanced

An electromagnetic sensor, built like a small transformer, that measures motor shaft angle and resists heat and vibration.

A resolver is an electromagnetic sensor for measuring rotation angle: an AC signal is applied to an excitation winding on the stator, and as the rotor turns, two output windings pick up signals proportional to the sine and cosine of the rotation angle, which a dedicated decoder chip (an RDC) converts into an angle. It has no optical components, and no electronics on the rotor itself, so it tolerates high temperatures, vibration, oil, and shock, and has long been used in electric-vehicle drive motors, aerospace, and industrial servo systems. Compared with optical or magnetic encoders, a resolver is tougher, but its accuracy and resolution usually fall short of a high-end optical encoder, and it needs extra decoding circuitry. Magnetic encoders are more common in robot joints; resolvers show up more often in high-power applications where reliability matters most.

ExampleElectric-vehicle drive motors commonly use a resolver to supply the rotor angle needed for field-oriented control.

Also called: Rotary Transformer
Related: Rotary Encoder · Magnetic Encoder · Optical Encoder · Permanent Magnet Synchronous Motor · Field-Oriented Control (FOC)
Sources: Resolver (electrical) - Wikipedia