The Mosolver, a combined motor and resolver, uses the existing motor magnetic structure and drive elements, in combination with a unique sensor within the motor to deliver 32,000 positions per revolution as well as commutation information even when the motor is stationary. As the sensor is based on a rugged, wide temperature range polyimide sensor coil, the environmental limits of the servo actuator are primarily limited by the motor rather than the sensor system.
The sensor detects the flux variation caused by the stator ripple current associated with the PWM drive. The flux is divided between different sections of the sense coil according to the tooth overlap between the rotor teeth and the stator teeth, with the overlap varying with rotor position. When properly sampled, the sensor coil produces sine and cosine information, which is decoded into 640 positions for each of the 50 electrical cycles per revolution, resulting in 32,000 positions per revolution. The sine and cosine information is also used for commutation without the need for a startup “wiggle” or transient. The position feedback is maintained at zero speed. The sensor is also inherently aligned.
The sensor coils are built on a passive polyimide flex circuit, affixed within the motor stator structure in the process of motor assembly. The standard polyimide sensor material is rated from -80 °C to 180 °C, with other formulations (substrate and adhesive systems) available with wide working temperature ranges from -269 °C to 400 °C. Polyimide flex circuits are also available in radiation resistant as well as low out-gassing formulations. When combined with a motor with similar ratings, the resulting Mosolver is capable of operating in harsh environments. As the sensor is entirely encapsulated within the motor structure, the resulting Mosolver Hybrid Servo is the same size as the motor itself and does not require additional housings to protect the feedback element as would be required for a resolver or encoder, saving weight as well as space.
The technology is available in product format as well as being available for licensing for specialty motors.
Visit www.mosolver.com for more information.
Filed Under: Motion Control Tips