Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Electric vehicle
Reexamination Certificate
2000-04-28
2001-12-04
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Electric vehicle
C701S084000, C318S825000, C318S826000
Reexamination Certificate
active
06327524
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to electric machine control and, more particularly, to a system for high efficiency motor control.
BACKGROUND ART
Automotive emissions have a negative impact on the Earth's environment. In an effort to reduce the effect of automotive emissions on the environment, extensive legislation has been passed to regulate the amount and types of emissions allowed for automobiles. As time has progressed, government regulations regarding the amount and types of emissions allowed has continued to become more strict. As a result, the automotive industry has continually explored technology to assist in emissions reduction. One possible technology being explored is hybrid or completely electric vehicles. These electric vehicles require the use of an electric motor as a power source.
Industrial applications such as electric vehicles, robotics, automated machine tools and precise positioning systems are generally implemented with DC-servo motors as power sources. DC motors are commonly used for applications requiring characteristics such as fast response and good low speed control because the torque developed by a DC motor is proportional to the armature current. The armature current of a DC motor is easily controlled using current feedback. Although the AC induction motor enjoys a number of advantages such as higher output per unit mass over the DC motor, the fact that rotor flux is induced rather than directly controlled has traditionally disqualified the AC induction motor from many high performance, high precision industrial applications.
The recent development of field-oriented control has now made fast torque control of induction motors achievable. Analogous to the DC machine, the torque control of an AC motor will be achieved through current control, however, in the AC case this must also include the phase as well as the amplitude.
In a DC motor the commutator and the brushes fix the orientation of the field flux and the armature mmf. However, in an AC machine, the orientation of the field flux and armature mmf must be controlled externally. If this orientation is not controlled in the AC motor then the angles between the various fields vary with loads and transients making for an oscillatory dynamic response. With the orientation between the fields controlled externally in the AC motor, current feedback can be applied to allow torque control.
Various approaches have been made to qualify the induction motor for high performance applications using various concepts of field oriented control. One approach involves the measurement of rotor flux and the determination of stator terminal excitation values needed to produce desired torque or speed conditions.
Also, overall drive system efficiency has not been an important issue until the advent of the electric vehicle. This is particularly important on electric vehicles because the range and acceleration of an electric vehicle is limited by its battery capacity.
The disadvantages associated with conventional motor control have made it apparent that a new technique for high efficiency motor control is needed. Preferably, the new technique should maximize motor torque and efficiency. The present invention is directed to these ends.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved and reliable means for high efficiency motor control. Another object of the invention is to maximize motor torque.
A device for high efficiency motor control includes an induction motor and a controller. The induction motor generates a motor torque and has a given rotor resistance and magnetizing inductance at a specific temperature. The controller is coupled to and controls the induction motor. The controller includes control logic operative to maximize the motor torque using a flux current and a torque current. The controller determines the flux current and torque current based upon a requested torque, a requested speed, the magnetizing inductance, the temperature and the rotor resistance.
The present invention achieves an improved and reliable means for a system for high efficiency motor control. Also, the present invention is advantageous in that it extends the useful range of electric vehicles.
Additional advantages and features of the present invention will become apparent from the description that follows, and may be realized by means of the instrumentalities and combinations particularly pointed out in the appended claims, taken in conjunction with the accompanying drawings.
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Arthur Gertrude
Cuchlinski Jr. William A.
Ford Global Technologies Inc.
Sparschu Mark S.
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