Method of controlling torque of vehicle driving device
method of controlling torque of a vehicle driving device is provided. The method includes estimating speed of a driving system of a vehicle from vehicle driving information collected from the vehicle and calculating speed difference between actually measured speed of the driving system and the estimated speed of the driving system. A nominal rate limit value is determined according to the vehicle driving information and a required real-time rate correction amount is determined according to the calculated speed difference. A torque command variation is determined based on the determined nominal rate limit value and the determined required real-time rate correction amount. A torque command after correction in a previous control period is corrected by the determined torque command variation to determine a torque command after correction in a current control period.
1. A method of controlling torque of a vehicle driving device, comprising:
estimating, by a controller, speed of an engine or a motor of a vehicle from vehicle driving information collected from the vehicle and calculating speed difference value between actually measured speed of the engine or the motor and the estimated speed of the engine or the motor;
wherein the speed difference is calculated between the actually measured speed of the engine or the motor and the estimated speed of the engine or the motor in which twisting and backlash are removed;
determining, by the controller, a nominal rate limit value according to the vehicle driving information;
determining, by the controller, a required real-time rate correction amount according to the calculated speed difference;
determining, by the controller, a torque command variation based on the determined nominal rate limit value and the determined required real-time rate correction amount; and
after a correction in a previous control period, correcting, by the controller, a torque command in a current control period with the determined torque command variation which then enables another torque command to be determined after the correction in the current control period.
2. The method according to claim 1 , wherein the determining of a torque command variation includes:
determining a rate after correction using the determined nominal rate limit value and the determined required real-time rate correction amount;
determining an overshoot prevention rate limit value, which is a difference value between a torque command before correction in a current control period determined from the vehicle driving information and a torque command after correction in a previous control period; and
determining a torque command variation based on the determined rate after correction and the determined overshoot prevention rate limit value.
3. The method according to claim 2 , wherein, in the determining of the rate after correction, the rate after correction is determined to be a value obtained by multiplying the determined nominal rate limit value by a scale factor determined to be a value corresponding to the required real-time rate correction amount.
4. The method according to claim 2 , wherein the overshoot prevention rate limit value is determined to be a value obtained by subtracting the torque command after correction in the previous control period from the torque command before correction in the current control period.
5. The method according to claim 4 , wherein
when the overshoot prevention rate limit value is determined to be a positive (+) value and the nominal rate limit value is determined to be a positive (+) value, a value obtained by summing the nominal rate limit value and the required real-time rate correction amount is determined to be a rate after correction, and a smaller one of the rate after correction and the overshoot prevention rate limit value is determined to be a torque command variation.
6. The method according to claim 4 , wherein when the overshoot prevention rate limit value is determined to be a negative (−) value and the nominal rate limit value is determined to be a positive (+) value, the nominal rate limit value is multiplied by −1 to change the nominal rate limit value to a negative (−) value, a value obtained by summing the nominal rate limit value changed to the negative (−) value and the required real-time rate correction amount is determined to be a rate after correction, and a larger one of the rate after correction and the overshoot prevention rate limit value is determined to be a torque command variation.
7. The method according to claim 4 , wherein both the overshoot prevention rate limit value and the nominal rate limit value, each of which is one of a positive (+) value and a negative (−) value, are determined to be identical positive (+) or negative (−) values, and a value obtained by summing the nominal rate limit value and the required real-time rate correction amount is determined to be a rate after correction.
8. The method according to claim 7 , wherein
when the overshoot prevention rate limit value is a positive (+) value, a smaller one of the rate after correction and the overshoot prevention rate limit value is determined to be a torque command variation, and
when the overshoot prevention rate limit value is a negative (−) value, a larger one of the rate after correction and the overshoot prevention rate limit value is determined to be a torque command variation.
9. The method according to claim 7 , wherein
when the overshoot prevention rate limit value is a positive (+) value, a minimum one of the rate after correction, the nominal rate limit value, and the overshoot prevention rate limit value is determined to be a torque command variation, and
when the overshoot prevention rate limit value is a negative (−) value, a maximum one of the rate after correction, the nominal rate limit value, and the overshoot prevention rate limit value is determined to be a torque command variation.
10. The method according to claim 4 , wherein
the overshoot prevention rate limit value and the nominal rate limit value are determined to be values having opposite signs, each of which is one of a positive (+) value and a negative (−) value, and
the nominal rate limit value is multiplied by −1 to reverse the sign of the nominal rate limit value, and a value obtained by summing the nominal rate limit value having the changed sign and the required real-time rate correction amount is determined to be a rate after correction.
11. The method according to claim 10 , wherein
when the overshoot prevention rate limit value is a positive (+) value, a smaller one of the rate after correction and the overshoot prevention rate limit value is determined to be a torque command variation, and
when the overshoot prevention rate limit value is a negative (−) value, a larger one of the rate after correction and the overshoot prevention rate limit value is determined to be a torque command variation.
12. The method according to claim 10 , wherein
when the overshoot prevention rate limit value is a positive (+) value, a minimum one of the rate after correction, the nominal rate limit value, and the overshoot prevention rate limit value is determined to be a torque command variation, and
when the overshoot prevention rate limit value is a negative (−) value, a maximum one of the rate after correction, the nominal rate limit value, and the overshoot prevention rate limit value is determined to be a torque command variation.
13. The method according to claim 2 , wherein the determining of a rate after correction includes:
determining a rate obtained by correcting the determined nominal rate limit value by the required real-time rate correction amount; and
determining the rate after correction obtained by limiting the rate corrected by the required real-time rate correction amount based on a reverse rate limit value.
14. The method according to claim 13 , wherein
when both the overshoot prevention rate limit value and the reverse rate limit value, each of which is one of a positive (+) value and a negative (−) value, are identical positive (+) or negative (−) values, the reverse rate limit value is multiplied by −1 to reverse the sign of the reverse rate limit value, and
the reverse rate limit value having the changed sign is used in limiting the rate corrected by the required real-time rate correction amount.
15. The method according to claim 2 , wherein the determining of a rate after correction includes:
determining a rate obtained by correcting the determined nominal rate limit value by the required real-time rate correction amount; and
determining the rate after correction obtained by limiting the rate corrected by the required real-time rate correction amount to a value between a set maximum rate limit value and a set minimum rate limit value.
16. The method according to claim 15 , wherein
when the overshoot prevention rate limit value and the maximum rate limit value are values having opposite signs, each of which is one of a positive (+) value and a negative (−) value, the maximum rate limit value is multiplied by −1 to reverse the sign of the maximum rate limit value,
when both the overshoot prevention rate limit value and the minimum rate limit value are values having same signs, each of which is one of a positive (+) value and a negative (−) value, the minimum rate limit value is multiplied by −1 to reverse the sign of the minimum rate limit value, and
the rate after correction limited to a value between the maximum rate limit value having the changed sign and the minimum rate limit value having the changed sign is determined.
17. The method according to claim 1 , wherein
the estimating of the speed of the engine or the motor of the vehicle from the collected vehicle driving information in the calculating of speed difference includes:
outputting, by a feedback calculation unit of the controller, a feedback control value using speed difference between current measured speed of the engine or the motor and estimated speed in a previous control period as input;
determining and outputting, by a feedforward calculation unit of the controller, torque of the engine or the motor from the vehicle driving information;
summing the output value of the feedback calculation unit and the output value of the feedforward calculation unit and converting a sum value into angular acceleration of the engine or the motor using an inertia correction coefficient; and
obtaining estimated speed of the engine or the motor from angular speed of the engine or the motor obtained by integrating the converted angular acceleration of the engine or the motor and rate information of a reference torque command.
18. The method according to claim 17 , wherein the feedback calculation unit includes:
a P controller and an I controller each having the speed difference between the current measured speed of the engine or the motor and the estimated speed in the previous control period as input; and
a first summation unit configured to sum an output value of the P controller and an output value of the I controller and to output a sum value as the feedback control value.
19. The method according to claim 17 , wherein the feedforward calculation unit includes:
an acceleration model unit configured to apply a correction coefficient to the reference torque command, which is a driving torque command, to determine and output a driving torque value;
a braking model unit configured to apply a correction coefficient to a braking torque command to determine and output a braking torque value; and
a second summation unit configured to sum an output value of the acceleration model unit and an output value of the braking model unit and to output a sum value as the torque of the engine or the motor.
20. The method according to claim 17 , wherein, in the obtaining of the estimated speed of the engine or the motor, a variation of the reference torque command is corrected by a correction coefficient and is summed with the angular speed of the engine or the motor to obtain the estimated speed of the engine or the motor.