Method for controlling output torque in powertrains
View Patent ↗A method of controlling output torque in a hybrid or electric vehicle transmissions includes calculating a first long-term output torque constraint and a first short-term output torque constraint. A first effective output torque constraint is determined from at least one of the first long-term and short-term output torque constraints. The first effective output torque constraint is bounded by both of the first long-term and short-term output torque constraints. The method may further include calculating a rate limit, such that determining the first effective output torque constraint includes restricting the magnitude of changes in the first long-term output torque constraint to the calculated rate limit. A spread between the first short-term output torque constraint and the first effective output torque constraint may be measured, and the rate limit calculated as a function of that spread. The rate limit may also be calculated with an inversely-proportional relationship to the spread.
1. A method of controlling output torque in a vehicle transmission including at least one electric machine and in electrical communication with a battery, comprising:
calculating a first long-term output torque constraint with a processor;
calculating a first short-term output torque constraint with the processor;
calculating a rate limit with the processor;
determining a first effective output torque constraint with the processor from the first long-term output torque constraint and the first short-term output torque constraint,
wherein the first effective output torque constraint is bounded by both of the first long-term output torque constraint and the first short-term output torque constraint,
wherein determining the first effective output torque constraint includes restricting the magnitude of changes in the first long-term output torque constraint to the rate limit, and
wherein restricting the magnitude of changes in the first long-term output torque constraint to the rate limit occurs only when the first long-term output torque constraint is tightening; and
operating the transmission at the first effective output torque constraint determined by the processor.
2. The method of claim 1 , further comprising:
measuring a spread with the processor between the first short-term output torque constraint and the first effective output torque constraint,
wherein the rate limit is calculated as a function of the spread.
3. The method of claim 2 , wherein the rate limit is calculated with an inversely-proportional relationship to the spread.
4. The method of claim 3 , wherein the first long-term output torque constraint is a maximum long-term output torque constraint, the first short-term output torque constraint is a maximum short-term output torque constraint, and the first effective output torque constraint is an effective maximum output torque constraint, and further comprising:
calculating a minimum long-term output torque constraint with the processor;
calculating a minimum short-term output torque constraint with the processor; and
determining an effective minimum output torque constraint with the processor by restricting the magnitude of changes in the minimum long-term output torque constraint to the rate limit, wherein the effective minimum output torque constraint is bounded by both of the minimum long-term output torque constraint and the minimum short-term output torque constraint.
5. The method of claim 4 :
wherein restricting changes in the minimum long-term output torque constraint to the rate limit occurs only when the minimum long-term output torque constraint is increasing, and
wherein restricting changes in the maximum long-term output torque constraint to the rate limit occurs only when the maximum long-term output torque constraint is decreasing.
6. The method of claim 5 , further comprising:
measuring an output torque request with the processor for the transmission,
wherein the rate limit is further calculated as a function of the output torque request.
7. The method of claim 6 ,
wherein the maximum and minimum long-term output torque constraints are calculated based upon long-term battery power limits, and long-term electric machine limits, and
wherein the maximum and minimum short-term output torque constraints are calculated based upon short-term battery power limits, and short-term electric machine limits.
8. The method of claim 1 , wherein the transmission is in electrical communication with a battery,
wherein the first long-term output torque constraint is calculated based upon long-term battery power limits of the battery, and
wherein the first short-term output torque constraint is calculated based upon short-term battery power limits of the battery.
9. The method of claim 8 , further comprising:
measuring an output torque request for the transmission with the processor,
wherein the rate limit is further calculated as a function of the measured output torque request.
10. The method of claim 9 , wherein the first long-term output torque constraint is a maximum long-term output torque constraint, the first short-term output torque constraint is a maximum short-term output torque constraint, and the first effective output torque constraint is an effective maximum output torque constraint, and further comprising:
calculating a minimum long-term output torque constraint with the processor;
calculating a minimum short-term output torque constraint with the processor; and
determining an effective minimum output torque constraint with the processor by restricting the magnitude of changes in the minimum long-term output torque constraint to the rate limit, wherein the effective minimum output torque constraint is bounded by both of the minimum long-term output torque constraint and the minimum short-term output torque constraint.