Method for detecting locked-axle conditions without a speed sensor
First Claim
1. A method for detecting the occurrence of an actual locked-axle condition in a vehicle propelled by AC motors, the steps of said method comprising:
- detecting a potential locked axle condition;
setting the frequency of an inverter which controls an AC motor coupled to the potentially locked axle to a predetermined frequency value;
varying the level of electromagnetic flux in the motor coupled to the potentially locked axle;
measuring torque produced by the motor during the flux varying step; and
determining based on the measured torque whether the potential locked-axle condition is an actual locked axle condition.
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Accused Products
Abstract
A method for detecting the occurrence of actual locked axle conditions in a vehicle propelled by AC motors includes the steps of detecting a potential locked axle condition, which may be induced due to a faulty speed sensor; setting the frequency of the inverter which controls operation of the AC motor coupled to the potentially locked axle at a predetermined frequency value; varying the level of electromagnetic flux in the motor; measuring torque produced by the motor; and determining based on the measured torque whether or not the potential locked axle condition is an actual locked axle condition.
26 Citations
17 Claims
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1. A method for detecting the occurrence of an actual locked-axle condition in a vehicle propelled by AC motors, the steps of said method comprising:
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detecting a potential locked axle condition; setting the frequency of an inverter which controls an AC motor coupled to the potentially locked axle to a predetermined frequency value; varying the level of electromagnetic flux in the motor coupled to the potentially locked axle; measuring torque produced by the motor during the flux varying step; and determining based on the measured torque whether the potential locked-axle condition is an actual locked axle condition. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for detecting the occurrence of an actual locked-axle condition in a vehicle propelled by AC motors, the steps of said method comprising:
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detecting a potential locked axle condition; setting the frequency of an inverter which controls an AC motor coupled to the potentially locked axle to a predetermined first frequency value at a first frequency polarity; varying the level of electromagnetic flux in the motor; measuring torque produced by the motor while operating at the predetermined frequency value and first polarity; setting the inverter frequency to a second value which is substantially the same as said predetermined first frequency value and at a second frequency polarity opposite to the first polarity; measuring torque produced by the motor while operating at the second frequency value and polarity; and determining based on the respective values of torque measured during the measuring steps whether the potential locked-axle condition is an actual locked axle condition. - View Dependent Claims (9, 10, 11, 12)
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13. A method for detecting, without a speed sensor, whether an axle in a vehicle propelled by AC motors is rotating at or near a given speed, the steps of said method comprising:
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choosing first and second frequency values such that the given speed is substantially centered relative to the first and second frequency values, the first and second frequency values being sufficiently apart from the given speed such that an AC motor coupled to the axle can generate a sufficiently measurable level of torque; setting the frequency of an inverter controlling the AC motor coupled to the axle to the first frequency value; varying the level of electromagnetic flux in the motor; measuring torque produced by the motor while operating at the first frequency value; setting the inverter frequency to the second frequency value; measuring torque produced by the motor while operating at the second frequency value; and determining based on the respective values of torque measured during the measuring steps whether the axle is rotating near the given speed. - View Dependent Claims (14, 15, 16, 17)
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Specification