Systems, methods, and apparatus for estimating torque during fault conditions

1. An apparatus for operation of an electric vehicle (EV) during a fault condition, the apparatus comprising:

a drive system comprising a motor configured to provide motive force to the EV; and

a processing system configured to:

run a diagnostic routine to monitor the drive system for the fault condition,

based on a result of the diagnostic routine, identify that the drive system is in the fault condition, and

in response to identifying that the drive system is in the fault condition:

determine a motor speed of the motor that caused the fault condition,

determine whether the fault condition caused a three-phase short circuit or a three-phase open circuit,

estimate a motor torque for the motor that caused the fault condition based at least partly on the motor speed and on whether the fault condition caused the three-phase short circuit or the three-phase open circuit, and

use the estimated motor torque to control the drive system to provide motive force to the EV while operating in the fault condition.

2. The apparatus of claim 1 , wherein the processing system is configured to determine the motor speed based on a receipt of the motor speed from a motor speed input.

3. The apparatus of claim 1 , wherein the processing system is configured to:

determine that the motor speed is not available;

determine that a motor current value is available; and

calculate the motor speed based on a frequency of the motor current value.

4. The apparatus of claim 1 , wherein the processing system is configured to:

determine that the motor speed is not available;

determine that a wheel speed value is available; and

calculate the motor speed based on the wheel speed value and a gear ratio.

5. The apparatus of claim 1 , wherein the processing system is configured to:

determine that the motor speed is not available;

determine that a motor current input value is not available;

determine that a wheel speed value is not available; and

in response to determining that the motor speed, motor current input value, and wheel speed value are not available, calculate the motor speed based on a speed of the EV.

6. The apparatus of claim 1 , wherein the processor is configured to, in response to determining that the fault condition caused the three-phase short circuit, estimate the motor torque by accessing a value of the motor torque in a lookup table stored in a memory, wherein the value of the motor torque corresponds to the motor speed in the lookup table.

7. The apparatus of claim 6 , wherein the lookup table comprises the motor torque value indexed by the motor speed and a temperature of the motor.

8. The apparatus of claim 1 , wherein the processor is configured to, in response to determining that the fault condition caused the three-phase short circuit, estimate the motor torque according to

T

qbk

=

-

3

2

⁢

n

p

⁢

R

s

⁢

λ

f

⁢

ω

e

⁡

(

R

s

2

+

ω

e

2

⁢

L

q

2

)

(

R

s

2

+

ω

e

2

⁢

L

d

⁢

L

q

)

2

,

wherein T qbk is the calculated motor torque for the motor, n p is a number of pole pairs of the motor, R s is a stator resistance of one phase of the motor, λ f is a rotor flux constant for a rotor of the motor, ω e is an electrical fundamental frequency of the motor; and L d and L q are dynamic d and q-axis inductances of the motor, respectively.

9. The apparatus of claim 8 , wherein a value of the stator resistance R s is determined based on a temperature of the motor.

10. The apparatus of claim 8 , wherein a value of the rotor flux constant λ f is determined based on a temperature of the motor.

11. The apparatus of claim 1 , wherein the processor is configured to the processor is configured to, in response to determining that the fault condition caused the three-phase open circuit, estimate the motor torque according to T=P shaft /ω r , wherein T is the calculated motor torque of the motor, P shaft is an estimated shaft power generated by the motor, and ω r is the calculated motor speed.

12. A method of operating an electric vehicle (EV) during a fault condition, the method comprising:

running a diagnostic routine to monitor a drive system for the fault condition, the drive system comprising a motor configured to provide motive force to the EV;

based on a result of the diagnostic routine, identifying that the drive system is in the fault condition, and

in response to identifying that the drive system is in the fault condition:

determining a motor speed of the motor,

determining whether the fault condition caused a three-phase short circuit or a three-phase open circuit,

estimating a motor torque for the motor based at least partly on the motor speed and on whether the fault condition caused the three-phase short circuit or the three-phase open circuit, and

using the estimated motor torque to control the drive system while operating in the fault condition.

13. The method of claim 12 , further comprising determining the motor speed based on a receipt of the motor speed from a motor speed input.

14. The method of claim 12 , further comprising:

determining that the motor speed is not available;

determining that a motor current value is available; and

calculating the motor speed based on a frequency of the motor current value.

15. The method of claim 12 , further comprising:

determining that the motor speed is not available;

determining that a wheel speed value is available; and

calculating the motor speed based on the wheel speed value and a gear ratio.

16. The method of claim 12 , further comprising:

determining that the motor speed is not available;

determining that a motor current input value is not available;

determining that a wheel speed value is not available; and

in response to determining that the motor speed, the motor current input value, and the wheel speed value are not available, calculating the motor speed based on a speed of the EV.

17. A non-transitory, computer-readable medium comprising computer-executable instructions that, when executed, cause a computing system that operates an electric vehicle (EV) during a fault condition to perform operations comprising:

running a diagnostic routine to monitor a drive system for the fault condition, the drive system comprising a motor configured to provide motive force to the EV;

based on a result of the diagnostic routine, identifying that the drive system is in the fault condition; and

in response to identifying that the drive system is in the fault condition:

determining a motor speed of the motor,

determining whether the fault condition caused a three-phase short circuit or a three-phase open circuit,

estimating a motor torque for the motor based at least partly on the motor speed and on whether the fault condition caused the three-phase short circuit or the three-phase open circuit, and

using the estimated motor torque to control the drive system while operating in the fault condition.

18. The non-transitory, computer-readable medium comprising computer-executable instructions of claim 17 , the operations further comprising:

determining that the motor speed is not available;

determining that a motor current value is available; and

calculating the motor speed based on a frequency of the motor current value.

19. The non-transitory, computer-readable medium comprising computer-executable instructions of claim 17 , the operations further comprising:

determining that the motor speed is not available;

determining that a wheel speed value is available; and

calculating the motor speed based on the wheel speed value and a gear ratio.

20. The non-transitory, computer-readable medium comprising computer-executable instructions of claim 17 , the operations further comprising:

determining that the motor speed is not available;

determining that a motor current input value is not available;

determining that a wheel speed value is not available; and

in response to determining that the motor speed, the motor current input value, and the wheel speed value are not available, calculating the motor speed based on a speed of the EV.