Resolvers

Resolvers are rotary electrical transformers or sensors used to measure the angular displacement and speed of rotating objects. They are analog devices that also have digital counterparts. Notably, many resolvers look somewhat like an electric motor, featuring copper windings on the stator and a machined metal rotor, which contributes to their compact and efficient design. They are widely used in applications requiring precise rotational measurements, such as robotics, aerospace, and industrial machinery, where accuracy is critical for system performance.

Resolvers are known for their high accuracy, reliability, and durability, making them ideal for use in harsh environments like extreme temperatures or high-vibration settings. They are immune to electrical noise and can function over a wide temperature range. With no contact parts, resolvers have a long operational life and require minimal maintenance. Their versatility and robust performance make them suitable for various demanding applications, ensuring precise and reliable measurements in challenging conditions.

Resolvers work on the principle of electromagnetic induction. A resolver includes a stator (the fixed part) and a rotor (the rotating part), both with windings. An AC voltage is applied to the primary winding on the stator, which creates a magnetic field. As the rotor turns in this field, voltages are induced in the rotor windings based on their position relative to the stator.

The resolver outputs two signals: sine and cosine. These signals vary with the rotor’s position—the sine signal corresponds to the sine of the rotation angle, and the cosine signal corresponds to the cosine. Resolver-to-digital converters (RDCs) process these signals to calculate the exact angular position. The ratio of the sine and cosine signals provides a precise angle measurement. This method converts mechanical rotation into electrical signals that can be accurately read and used in applications like motion control.