Managing wheel slip in a locomotive
The present invention is directed to the termination of the occurrence of wheel slip/skid and prediction and prevention of the onset of wheel slip/skid in a locomotive. In one configuration, a lookup table of adhesion factors is used to predict the occurrence of wheel slip/skid.
1. A locomotive, comprising:
a plurality of series connected DC traction motors, each of the plurality of series connected DC traction motors being independently coupled to and driving at least one wheel;
a plurality of sensors operable to sense an operating characteristic, wherein each of the sensors corresponds to a series connected DC traction motor; and
a controller operable to (a) determine, based on the sensed operating characteristic, that at least one wheel corresponding to a first series connected DC traction motor is experiencing wheel slippage and (b) in response thereto incrementally reduce power supplied to the first series connected DC traction motor for a selected period of time while continuing to provide power in excess of the reduced power to at least one other of the plurality of series connected DC traction motors, wherein the reduced power continues to drive the at least one wheel experiencing wheel slippage, wherein the power is supplied to the first traction motor in a series of pulses, wherein at least one of the amplitude and pulse width of the pulses is incrementally reduced, and wherein, after each incremental power reduction, the reduced power is maintained for a predetermined time interval to determine whether wheel slippage has been reduced to a predetermined acceptable level as a result of the respective incremental power reduction.
2. The locomotive of claim 1 , wherein the controller is further operable to compare the detected operating characteristic detected for each of the series connected DC traction motors to an operating characteristic set point and, when the detected operating characteristic for any series connected DC traction motor traverses to the undesirable side of the operating characteristic set point, the controller determines that the at least one wheel of the corresponding traction motor is experiencing wheel slippage.
3. The locomotive of claim 1 , wherein, upon the detection of a predetermined acceptable level of wheel slippage, the reduced power is not further reduced and wherein the at least one of the a amplitude and pulse width of the pulses supplied to the first series connected DC traction motor is different from the at least one of the amplitude and pulse width of the pulses supplied to the at least one other of the plurality of traction motors over the selected time period.
4. The locomotive of claim 1 , wherein the sensed operating characteristic is a corresponding electrical current supplied to each of the plurality of series connected DC traction motors, and wherein the determining operation includes the sub-operations of: determining that the electrical current and/or electrical current time derivative corresponding to the first series connected DC traction motor has decreased, wherein, when the decrease is abrupt, the controller determines that at least one wheel of the first series connected DC traction motor is experiencing wheel slip.
5. The locomotive of claim 1 , wherein the sensed operating characteristic is an operating speed of at least one wheel driven by each of the series connected DC traction motors and wherein the controller is further operable to detect a speed of the locomotive and wherein, when the speed of a wheel exceeds the locomotive speed, the controller determines that the wheel is experiencing wheel slip.
6. The locomotive of claim 1 , wherein the sensed operating characteristic is a corresponding revolutions-per-minute of each of the plurality of series connected DC traction motors, and wherein, when an increase in the revolutions-per-minute is abrupt, the controller determines that at least one wheel of the first series connected DC traction motor is experiencing wheel slip.
7. The locomotive of claim 1 , further comprising:
a prime energy source;
an energy conversion device, in communication with the prime energy source, to convert the energy output by the prime energy source into direct current electricity;
an energy storage device, in communication with the energy conversion device and the plurality of series connected DC traction motors, to receive and store direct current electricity; and
a plurality of power control circuits corresponding to the plurality of series connected DC traction motors.
8. The locomotive of claim 1 , wherein the controller is operable to reduce power supplied to the first series connected DC traction motor in increments in a range of 5-50% of a previous power supplied to the first series connected DC traction motor.
9. The locomotive of claim 1 , wherein the controller is operable to reduce power supplied to the first series connected DC traction motor in increments in a range of 10-35% of a previous power supplied to the first series connected DC traction motor.
10. The locomotive of claim 1 , wherein the controller is operable to reduce power supplied to the first series connected DC traction motor in increments in a range of 10-20% of a previous power supplied to the first series connected DC traction motor.
11. The locomotive of claim 1 , wherein the controller is operable to incrementally reduce power supplied to the first series connected DC traction motor in 4 millisecond intervals.
12. The locomotive of claim 1 , wherein each of the plurality of series connected DC traction motors has a chopper circuit associated therewith for selectively providing power to the associated series connected DC traction motor under control of the controller.