Step-Motor Drives

Servomotor performance from low-cost step-motors

In applying field-oriented or vector control, Innovatia motor drives achieve from step-motors performance comparable to more costly "brushless dc" permanent-magnet synchronous motors.

Innovatia motion-control designware projects are the StepMaker and StepMaster. Prototypes of these technologies have reached design completion and project manuals for your participation in these projects are being prepared.  Motion-control concepts used in these two projects are explained in the following article:

Motor-drive field-oriented control theory

Winding-Sensed Vector-Control of PMS Motor-Drives

Torque control with no position sensors

The rotor position is sensed from the motor terminal voltages. This eliminates the need for a shaft encoder or resolver. The motor controller provides rotor position to the path controller, which sends it a torque command.

StepMaker - low-cost, six-step per electrical cycle, field-oriented control of 3-phase PMS motors.

Field-oriented control

Field-oriented control eliminates the resonances and loss of dynamic control due to open-loop microstepping. The motor instead behaves like a dc brush motor, even when changing speed. Instead of pulsing the rotor from one equilibrium position (step) to the next, field-oriented control continually maintains correct drive at all rotor positions.

The StepMaker is currently undergoing design refinement. Some designware is available. Contact Innovatia for project details.

StepMaster - high-performance field-oriented control of step-motors.

High-performance dynamic step-motor control

Industrial-size step-motors are essentially permanent-magnet synchronous (PMS) motors with negligible variable reluctance and many poles. They are generally less expensive than PMS "servo" motors with fewer poles and a round rotor. Innovatia design offers significant advances over microstepping: sensorless field-oriented (vector) step-motor control.

Low-speed microstepping

At low speeds (typically < 50 rpm), the motor-induced voltage is too small to reliably sense position. The mode of control defaults to microstepping or external position sensing. At low speed, if accelerations are also low for fine positioning, microstepping can often move the motor to the end position with acceptable motion performance.

The StepMaster is currently undergoing design refinement. Designware of the previous generation is available but not recommended for new product manufacture. Contact Innovatia for project details.

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