Low Speed and High Speed Controller Architecture for Electric Motors

Abstract

A motor controller architecture and method of operating the same. The motor controller includes a function for estimating the low speed operation of the motor, for example by evaluating the response to a periodic excitation signal injected into the control loop of the controller architecture. A periodic excitation signal in the form of a square wave allows for analysis of the response of the motor without requiring demodulation, which allows the frequency of the excitation signal to be above the audible range. Control logic for controlling the motor at transitional speeds between low speed control and high speed (back emf) control is provided in some embodiments.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority, under 35 U.S.C. §119(e), of Provisional Application Nos. 61 / 881,714 and 61 / 881,730, both filed Sep. 24, 2013, and both incorporated herein by this reference. This application is also a continuation-in-part, under 35 U.S.C. §120, of copending application Ser. No. 14 / 245,206, filed Apr. 4, 2014, incorporated herein by this reference, which claims priority, under 35 U.S.C. §119(e), of Provisional Application No. 61 / 819,267, filed May 3, 2013, also incorporated herein by this reference.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT[0002]Not applicable.BACKGROUND OF THE INVENTION[0003]This invention is in the field of control systems for electric machines. Embodiments described in this specification are more specifically directed to control of alternating current (AC) electric motors operating at low speed.[0004]Even more than a century after their introduction, AC electric motors continue to ...

AI Technical Summary

Benefits of technology

The patent text describes a new controller architecture and method for electric machines that can accurately control their speed, even at low speeds. This architecture can be easily integrated into existing control loops without adding too much complexity.

Problems solved by technology

Field-oriented control of AC motors is complicated because the rotation of the magnetic field in the stator with respect to the rotating magnetic field of the rotor can be asynchronous.

However, as is well known in the art, these sensors and associated wiring and connectors add significant cost and complexity in the motor and its control system, and are prone to inaccuracy and mechanical failure.

As such, conventional sensorless motor control is not well-suited for low speed control of AC motors.

However, certain new AC motor applications require low speed control.

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