Predictive power split with zero-emission zone handling
Hybrid vehicles and control methods for hybrid vehicles. The vehicles and methods are adapted for use with restricted emissions zones, including zero emission zones. The battery state of charge for a hybrid vehicle is controlled to enable passage through a zero emissions zone without the use of the engine in the zero emissions zone. Multiple approaches to the analysis are highlighted.
1. A vehicle comprising:
a first power source and a second power source, the second power source being a rechargeable battery, the first and second power sources configured to provide drive power to a transmission for output to a wheel of the vehicle;
a controller configured to determine power utilization between the first power source and the second power source, including generating a lower state of charge (SOC) limit value for the battery of the second power source, the lower SOC limit value indicative of a minimum target state of charge of the battery calculated at specific locations or points in time along the vehicle route; and
a navigation system configured to determine a vehicle route and identify in the vehicle route a restricted emissions zone; wherein:
the controller is configured to receive an indication of an entry to and an exit from the restricted emissions zone along the vehicle route and adjust the lower SOC limit value as a function of proximity to the restricted emissions zone by:
determining a total charge from the second power source needed to traverse the restricted emissions zone from the entry location to the exit location;
calculating a desired SOC at entry to the restricted emissions zone from the total charge;
determining torque needed to reach the entry of the restricted emissions zone; and
calculating a series of lower SOC limit values for use along the route which increase as distance to the entry location reduces; and
wherein the controller is further configured to determine power utilization between the first power source and the second power source by performing a cost function minimization using a prediction horizon, wherein the series of lower SOC limit values are used in the cost function minimization as penalties responsive to the estimated SOC of the battery of the second power source at an end of the prediction horizon being below a lower SOC limit value at the end of the prediction horizon.
2. The vehicle of claim 1 , wherein the controller is configured to reduce the lower SOC limit value upon entry to the restricted emissions zone.
3. The vehicle of claim 1 , wherein the restricted emissions zone is a zero emissions zone (ZEZ), and one of the series of lower SOC limit values is set to allow the vehicle to traverse the ZEZ using only power from the second power source.
4. The vehicle of claim 1 wherein the controller is configured to determine control parameters for the first and second power sources such that the battery of the second power source has an actual SOC at the entry to the restricted emissions zone which enables the vehicle to traverse the restricted emissions zone while operating as an electric vehicle.
5. The vehicle of claim 1 wherein the controller is configured to calculate the series of lower SOC limit values for use along the route which increase as distance to the entry location reduces by working backward from a restricted zone entry SOC limit value that will allows the vehicle to traverse the restricted emissions zone while operating in a selected mode, to a default SOC limit value, and determining an SOC slope that defines differences from one SOC limit value to a next SOC limit value throughout the series of lower SOC limit values.
6. The vehicle of claim 1 , wherein the controller is configured to determine torque needed to reach the entry of the restricted emissions zone by analysis of one or more of road grade, curvature, traffic, and speed limits in the vehicle route.
7. The vehicle of claim 1 , wherein the controller is configured to determine a total charge from the second power source needed to traverse the restricted emissions zone from the entry location to the exit location by analyzing one or more of road grade, curvature, traffic, and speed limits in the vehicle route.
8. The vehicle of claim 1 , wherein the controller is configured to determine a total charge from the second power source needed to traverse the restricted emission zone from the entry location to the exit location by analyzing a prior trip through the restricted emissions zone.
9. A vehicle comprising:
a first power source and a second power source, the second power source being a rechargeable battery, the first and second power sources configured to provide drive power to a transmission for output to a wheel of the vehicle;
a controller configured to determine power utilization between the first power source and the second power source, including generating a lower state of charge (SOC) limit value for the battery of the second power source, the lower SOC limit value indicative of a minimum target state of charge of the battery calculated at specific locations or points in time along the vehicle route; and
a navigation system configured to determine a vehicle route and identify in the vehicle route a restricted emissions zone; wherein:
the controller is configured to receive an indication of an entry to and an exit from the restricted emissions zone along the vehicle route and adjust the lower SOC limit value as a function of proximity to the restricted emissions zone by:
determining a total charge from the second power source needed to traverse the restricted emissions zone from the entry location to the exit location;
calculating a desired SOC at entry to the restricted emissions zone from the total charge;
extrapolating from a set of past or predicted future SOC values for the battery of the second power source a projected SOC value at entry to the restricted emission zone;
further wherein the controller is configured to determine power utilization between the first power source and the second power source and generate control values for the first and second power sources by performing a cost function minimization using a prediction horizon, and wherein the cost function comprises a penalty term which is a product of a weighting value multiplied by an SOC shortfall calculated by subtracting the projected SOC value from the desired SOC at entry to the restricted emissions zone.
10. The vehicle of claim 9 , wherein the controller is configured to determine a total charge from the second power source needed to traverse the restricted emissions zone from the entry location to the exit location by analyzing one or more of road grade, curvature, traffic, and speed limits in the vehicle route.
11. The vehicle of claim 9 , wherein the controller is configured to determine a total charge from the second power source needed to traverse the restricted emission zone from the entry location to the exit location by analyzing a prior trip through the restricted emissions zone.
12. The vehicle of claim 9 , wherein the set of past or predicted future SOC values includes one or more past SOC values and one or more future SOC values calculated within the prediction horizon.
13. The vehicle of claim 9 , wherein the set of past or predicted future SOC values includes only future SOC values calculated within the prediction horizon.
14. A vehicle comprising:
a first power source and a second power source, the second power source being a rechargeable battery, the first and second power sources configured to provide drive power to a transmission for output to a wheel of the vehicle;
a controller configured to determine power utilization between the first power source and the second power source, including generating a lower state of charge (SOC) limit value for the battery of the second power source, the lower SOC limit value indicative of a minimum target state of charge of the battery calculated at specific locations or points in time along the vehicle route; and
a navigation system configured to determine a vehicle route and identify in the vehicle route a restricted emissions zone; wherein:
the controller is configured to receive an indication of an entry to and an exit from the restricted emissions zone along the vehicle route, and to perform a cost function analysis to determine operating parameters including power split between the first power source and the second power source as follows:
including in a cost function a first term for a first prediction horizon having a first duration and a first sample length;
including in the cost function a second term for a second prediction horizon occurring after the first prediction horizon, the second prediction horizon having a second duration that is at least twice the first duration and a second sample length that is at least twice the first sample length; and
determining the operating parameters by minimizing the cost function including calculations throughout the first prediction horizon and the second prediction horizon.
15. The vehicle of claim 14 , wherein the second prediction horizon is sufficiently long to include each of the entry to and the exit from the restricted emissions zone.
16. The vehicle of claim 14 , wherein the second prediction horizon is at least ten times as long as the first prediction horizon, and the second sample length is at least ten times the first sample length.
17. The vehicle of claim 14 , wherein:
the controller is configured to analyze a path through the restricted emissions zone and determine the lower battery state of charge (SOC) limit value for entry to the restricted emissions zone;
the controller is configured to determine a predicted battery SOC at entry to the restricted emissions zone as part of the cost function analysis, and include a penalty in the cost function analysis applicable if the predicted battery SOC at entry to the restricted emission zone is below the lower battery SOC limit value for entry to the restricted emissions zone.
18. The vehicle of claim 17 , wherein the controller is configured to determine the lower battery SOC limit value for entry to the restricted emission zone by analyzing one or more of road grade, curvature, traffic, and speed limits in the vehicle route.
19. The vehicle of claim 14 , wherein:
the controller is configured to determine the lower battery SOC limit value for entry to the restricted emissions zone from data related to a prior traverse of the restricted emissions zone by the vehicle; and
the controller is configured to determine a predicted battery SOC at entry to the restricted emissions zone as part of the cost function analysis, and include a penalty in the cost function analysis applicable if the predicted battery SOC at entry to the restricted emission zone is below the lower battery SOC limit value for entry to the restricted emissions zone.