Drives and Controls Magazine
Servo actuator eliminates the need for encoders
Published:  04 February, 2014

A Californian motion control specialist has developed a servo actuator that integrates a position feedback sensor into a high pole-count AC motor. QuickSilver Controls says that its Mosolver actuator will eliminate the need for costly encoder and resolvers, as well as eliminating most of the sensing electronics and the power needed to operate them.

By combining the motor and resolver into a single package, the device offers a compact, inexpensive and robust closed-loop motion controller that operates quietly. The Mosolver is the same size as the motor alone.

Sensing coils in the motor provide precise information on the rotor position. Voltages are induced in the sensing coils using a combination of the PWM current ripple and flux steering as a result of interaction between the rotor and stator magnetic fields. The Mosolver can resolve up to 32,000 counts per revolution.

QuickSilver Controls' Mosolver servo actuator does not need a separate encoder

The position sensing is said to be absolute over a commutation cycle, allowing true sinusoidal commutation, and eliminating the need for start-up motion.  As well as cutting costs, the elimination of a separate feedback device reduces the actuator’s size, avoids the need for (and possible loss of) alignment, and improves the ruggedness of the system.

The Mosolver design is protected by several US and European patents.