Hybrid Vehicle Engine Torque Control Across Battery SOC Levels
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Solution Overview
Problem
Hybrid vehicles experience a sharp deterioration in engine efficiency and fuel efficiency when the State of Charge (SOC) value of the battery decreases, particularly due to changes in intake air density and operating points.
Innovation Solution
A hybrid vehicle control method that determines a final target torque for the engine based on the SOC section of the battery, adjusting the engine torque between an optimal operating line, an intermediate stage part-load maximum torque, and a part-load maximum torque after correction to maintain efficient engine operation across varying SOC levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the engine charges the battery by rapidly outputting torque greater than OOL torque when SOC value decreases to threshold level, then sufficient torque for charging the battery is secured, but engine efficiency sharply deteriorates and fuel efficiency of the vehicle deteriorates
Solution Approach 1:
The patent applies dynamics by making the engine torque control strategy adaptive and variable based on real-time SOC conditions. The controller dynamically adjusts the target engine torque according to the current SOC value, transitioning between different control modes (normal torque around OOL, intermediate torque, and maximum torque) as SOC decreases. This dynamic adjustment allows the system to optimize the balance between battery charging requirements and engine efficiency at different charge states.
Solution Approach 2:
The patent implements parameter changes by modifying the target engine torque parameter based on SOC thresholds. When SOC is above the first threshold, the engine operates at normal torque around the OOL. When SOC drops below the first threshold but remains above the second threshold, the target torque is adjusted to an intermediate value. When SOC falls below the second threshold, the engine outputs maximum torque. This staged parameter adjustment resolves the contradiction by preventing abrupt torque increases that would cause sharp efficiency deterioration.
2Power
If the ECU controls ignition time to compensate for engine output due to decrease in filling efficiency, then engine output is compensated, but engine efficiency deteriorates compared to standard state
Solution Approach 1:
The patent addresses this contradiction by changing the control parameter from ignition timing adjustment to direct engine torque target adjustment based on SOC. Instead of compensating for filling efficiency losses through ignition timing changes (which deteriorate efficiency), the system directly adjusts the target engine torque according to SOC levels. This approach maintains the ability to control engine output while avoiding the efficiency penalty associated with ignition timing compensation.
Data Source
AI summary
A hybrid vehicle includes an engine which generates power by combustion of fuel; a drive motor which generates power, and is selectively operated as a generator to generate electrical energy; a battery which is connected to the drive motor and supplies electrical energy to the drive motor and charges the electrical energy generated in the drive motor; a battery management system which measures a State of charge (SOC) value of the battery; and a controller which is configured to determine a final target torque of the engine in a Hybrid Electric Vehicle (HEV) mode based on an SOC section in which the SOC value of the battery measured in the battery management system belongs.