Agile Systems has received a patent for technology designed to improve stepper-motor performance. It allows simple low-cost two-phase stepper motors to operate as sophisticated servo motors without the use of external sensors.
The patented technique transitions from open-loop micro-stepping methodology at low-speed control after gathering enough information from the motor. The algorithm calculates the position of a rotor from the sensing circuitry in the amplifier, and when the motor reaches 30 rpm to 60 rpm, depending on the motor design, it switches to servo control. When servo techniques are applied to the stepper motor, the results are higher acceleration and deceleration, greater efficiency, stall detection and prevention, and higher potential motor speeds.Agile’s SILENTstep incorporates this patented technique to control a two-phase stepper motor. Stepper motors produce high torque at low speeds, and attempts to increase their speeds often result in the motor stalling out. However, SILENTstep software algorithms eliminate this potential for stalling.