Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Electrical signal parameter measurement system
Reexamination Certificate
1999-11-03
2002-04-02
Grimley, Arthur T. (Department: 2852)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Electrical signal parameter measurement system
C702S064000, C702S065000, C318S701000, C318S727000
Reexamination Certificate
active
06366865
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to electronic circuits, and more particularly to a motor controller and to a method.
BACKGROUND OF THE INVENTION
Switched Reluctance Motors (SRM) find more and more use, for example, in household appliances (e.g., washing machines, dishwashers, vacuum cleaners), industrial machines, and in cars (starter/generator, window lifter, pumps). The motor has a stator with consecutively switched windings (“coils”) creating a rotating magnetic field under control of a microcontroller and semiconductor switches.
For many applications it is desirable to know the actual mechanical position of the rotor in respect to the stator (rotor-to-stator angle). The position can be measured by a mechanical position sensor. However, the sensor would require space (inside or outside the motor), would be coupled by a extra cable (expensive, sometimes shielded), may limit the application scope of the motor (especially for high speed), and may exhibit further disadvantages (e.g., lower reliability). A sensorless position estimator using the microcontroller can be used instead.
A useful reference for construction and operation of a SPM with a sensorless estimator is: “Wolff, J.; Rahner, R.; Späth, H.: ‘Sensorless Speed Control of a Switched Reluctance Motor for Industrial Applications’, Proceedings of ‘Optimization of Electrical and Electronic Equipment’, Vol. 2, p. 457-462, Brasov 1998” Wolff et al. describe sensorless position estimation for an industrial motor (power supply 3×400 V/50 Hz) taking into account an assumed value R for the ohmic coil resistance. Compared to the coil voltage, the resulting ohmic voltage drop was small and could be have been neglected.
However, for low-voltage applications (e.g., 12 or 24 volts supply in a car), the coil resistance R becomes unneglectable. Resistance changes during the operation of the motor, for example, an 25% increase from start-up to continuous running duty when the motor is warming up, require a more accurate estimation. While it is possible to derive R for a motor stand-still in a calibration mode, there is a practical requirement to obtain R substantially at any time even if the motor is rotating.
The present invention seeks to provide an improved motor controller operating according to an improved resistance estimation method which mitigate or avoid these and other disadvantages and limitations of the prior art.
REFERENCES:
patent: 4451770 (1984-05-01), Boettner et al.
patent: 5589754 (1996-12-01), Heikkila
patent: 6069467 (2000-05-01), Jansen
patent: 6249418 (2000-06-01), Bergstrom
Wolff, J.; Rahner, R.; Späth, H.; “Sensorless Speed Control of a Switched Reluctance Motor for Industrial Applications”, Proceedings of “Optimization of Electrical and Electronic Equipment”, vol. 2, pp. 457-462, Brasov 1998.
Chalupa Leos
Visinka Radim
Charioui Mohamed
Fink Mark J.
Grimley Arthur T.
Motorola Inc.
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