Electricity: motive power systems – Positional servo systems – Pulse-width modulated power input to motor
Reexamination Certificate
2000-03-22
2001-09-18
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Positional servo systems
Pulse-width modulated power input to motor
C318S478000, C318S456000, C318S811000
Reexamination Certificate
active
06291960
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to the operation of electric motors, and more particularly, to a method and system of operating an electric motor to reduce noise vibration and harshness.
BACKGROUND
Electric motors are used for various purposes in automotive vehicles. Commonly, pulse width modulation (PWM) is used to drive the motor. A number of trade offs must be considered when determining the duty cycle of the pulse width modulation signal. System performance and NVH goals are typically at competing ends of the trade off dynamic. For example, in order to meet NVH goals, the duty cycle of the pulse width modulated signal should be low. However, the low duty cycle requires the motor to run longer and may potentially compromise the system performance. Oftentimes minimum duty cycle levels are set so that minimum performance criteria of a given system may be met. The minimum duty cycles do not allow reduced noise vibration and harshness (NVH).
It would therefore be desirable to provide a motor-driven system that is capable of operating at a reduced noise vibration and harshness level while not compromising overall system performance.
SUMMARY OF THE INVENTION
It is therefore one object of the invention to provide a pulse width modulated motor control system that can vary the pulse width modulation in response to system performance to reduce noise vibration and harshness of the system.
In one aspect of the invention, an apparatus for reducing motor noise in a motor driven system has a sensor coupled to the system that generates an electrical signal indicative of a system operating parameter. A controller is coupled to the motor and the sensor. The controller drives the motor with a pulse width modulated signal having a variable duty cycle. The controller monitors the electrical signal and varies the pulse width modulated signal from a low duty cycle corresponding to a low noise operation of the motor to a higher duty cycle in response to an increased demand as indicated by the sensor.
In a further aspect of the invention, a method for reducing in a motor-driven system comprises the steps of:
applying a primary pulse width modulated signal having a first duty cycle to the motor;
monitoring a system parameter; and
applying a second pulse width modulated signal having a second duty cycle greater than said first duty cycle to said motor in response to system parameter.
One advantage of the invention is that the motor will operate at a reduced noise level for much of its operation while not under a substantial load. The duty cycle is increased when demand on the system increases.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.
REFERENCES:
patent: 4958636 (1990-09-01), Blandino et al.
patent: 5110152 (1992-05-01), Jones
patent: 5477833 (1995-12-01), Leighton
patent: 5900704 (1999-05-01), Henninger et al.
patent: 5986426 (1999-11-01), Rowan
patent: 6047557 (2000-05-01), Pham et al.
Ford Global Technologies Inc.
Leykin Rita
Nappi Robert E.
Sparschu Mark S.
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