Electricity: motive power systems – Limitation of motor load – current – torque or force
Reexamination Certificate
2000-02-08
2001-08-07
Masih, Karen (Department: 2837)
Electricity: motive power systems
Limitation of motor load, current, torque or force
C318S433000, C318S798000, C318S799000, C388S907500
Reexamination Certificate
active
06271637
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to diagnostic systems.
BACKGROUND OF THE INVENTION
It is known to provide electric motors to provide power assisted steering in automobiles or other vehicles. Electric motors have various known advantages over traditional hydraulic power assist systems, among the most notable being significant energy savings at high engine RPMs. However, electric systems are also prone to failures that are unknown to hydraulic systems, such as short circuits and the like. What is needed is a diagnostic system that can monitor an electric power steering system, detect various electrical failures, and signal the failure to the operator.
BRIEF SUMMARY OF THE INVENTION
Common failure of electric motors used for automotive purposes include closed current feedback loop failures, motor phase-to-phase shorts, and open motor phases. In automotive applications, such as electric power assist, these failures show the common trait of exhibiting deviations from normal operating currents.
Disclosed herein is a system for measuring deviations from normal operating currents. There is provided a diagnostic control unit DCU that is preferably integrated with the motor's controller to form an Electronic Control Unit ECU on a single chip. The DCU takes as inputs the desired command current I
desired
, the measured motor current V
fb
and the motor speed. This information is used to calculate a valid range of motor current. If the measured current falls out of this range, an error is signaled.
In a preferred embodiment, errors are accumulated on a counter and are not signaled until the counter exceeds a predetermined threshold.
REFERENCES:
patent: 5631796 (1997-05-01), Yoshihara et al.
patent: 5780980 (1998-07-01), Naito
Anderson Edmund P.
Delphi Technologies Inc.
Masih Karen
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