What Are Synchros and Resolvers?

Whether a pilot is using an inertial navigation reference unit, automatic direction finder, omnirange system, cockpit indicator, or many other aircraft systems that they regularly depend on during flight operations, they rely on the capabilities of synchros and resolvers. This is because synchros and resolvers serve as types of transducers, devices that convert energy from one form to another. Synchros and resolvers have been implemented in many military and commercial systems for a number of years, and they provide for high reliability for applications in which difficult environments are present. In this blog, we will discuss more in detail about what synchros and resolvers are, and how they benefit the systems that they are present in.

In general, servos and resolvers are World War II era technology that act similarly to transformers, containing both primary and secondary windings. Also like a transformer, the primary windings of both are driven by an alternating current signal. Synchro and resolver parts come in many types, including Amplifier Resolver, drive resolver, amplifier synchro, and adapter synchro components. While servos and resolvers are similar to one another in some of their components, they do have some distinct differences that set them apart. Typically, a synchro features one primary winding and three secondary windings, while a resolver has two primary windings and two secondary windings perpendicular from each other.

Both also act mechanically like a motor, and each provide their own uses for different applications and systems. Resolvers are considered a type of synchro, and they may be used in various aircraft systems. Synchros in general may be used to track rotary output angles of a closed-loop system, utilizing the gained feedback to provide accuracy and repeatability. Synchros may continuously turn, and the fact that their secondary winding outputs are analog signals allows for an infinite resolution output. While the synchro shaft turns, the rotor winding angular position adjusts in comparison to the Stator Windings. The resulting AC output signal of the secondary windings then indicates the rotary position of the shaft.

Once the analog output signal is produced by the synchro, it then needs to be converted into a digital form. This is conducted by a synchro-to-digital converter, due to the fact that synchros feature inductive characteristics that affect readings, thus output signals may be distorted due to nonlinearities in the synchro. With a synchro-to-digital converter, transformer-isolated inputs and outputs may be used to convert signals efficiently.

Synchro and resolver performance is typically measured based on their accuracy, resolution, distortion, phase shift, and dynamic characteristics. To ensure that they can conduct with such performance, advanced testing equipment may be utilized to measure such factors. synchros and resolvers are present in many aircraft systems and equipment, including but not limited to flight surface controls, landing gear, aircraft instruments, actuators, and other equipment. Due to their importance to such flight systems, it is always critical that they are well maintained and inspected so that they may provide for peak performance.