Hybrid Vehicle Controller Engine Start Delay
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Solution Overview
Problem
Hybrid electric vehicles face challenges in improving fuel economy and customer perception due to unnecessary engine starts and restarts during inefficient operations, particularly when transitioning from electric-only mode to engine-assisted mode.
Innovation Solution
A controller in the hybrid electric vehicle is configured to delay engine start events by applying an engine-start-threshold offset based on vehicle speed and battery state of charge, allowing continued electric-only operation until the driver power request exceeds a modified engine-start threshold, thus avoiding premature engine activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine is started whenever the driver power request exceeds the engine-start threshold, then the vehicle can respond to power demands, but unnecessary engine starts occur during low-speed electric-only operation, reducing fuel economy perception
Solution Approach 1:
The engine-start threshold is made dynamic by introducing an offset that varies with vehicle speed. At low speeds, a positive offset raises the threshold to prevent unnecessary starts, while at higher speeds the offset decreases to allow timely engine activation when needed.
Solution Approach 2:
The control system changes the parameter of the engine-start threshold based on vehicle operating conditions (speed and battery SOC). By adjusting this parameter dynamically, the system optimizes the balance between fuel economy and power responsiveness.
2Use of energy by moving object
If the engine-start threshold is lowered to enable electric-only operation at low speeds, then fuel economy improves, but the engine may fail to start during brief temporary increases in driver power request
Solution Approach 1:
The system provides a cushion by raising the effective start threshold through the offset, which prevents premature engine starts. This cushion allows the electric motor to handle transient power demands without unnecessary engine intervention, while still ensuring reliable starts when genuinely needed.
Solution Approach 2:
The control system continuously monitors vehicle speed and battery state of charge to dynamically adjust the engine-start threshold. This feedback mechanism ensures the threshold adapts to current operating conditions, preventing both unnecessary starts and missed start opportunities.
3Use of energy by moving object
If the engine-start-threshold offset is increased to maximize electric-only operation, then fuel economy perception improves, but the battery discharge limit may be exceeded
Solution Approach 1:
The offset parameter is dynamically adjusted based on battery state of charge. When battery SOC is high, a larger offset can be applied to maximize electric-only operation. When battery SOC decreases, the offset is reduced to ensure the battery discharge limit is not exceeded.
Solution Approach 2:
The control system uses real-time feedback on battery state of charge to modulate the offset magnitude. This ensures the offset provides maximum fuel economy benefit while continuously respecting the battery's discharge capabilities.
Data Source
AI summary
A hybrid electric vehicle includes an internal combustion engine configured to provide power to traction wheels, and a controller. The controller is configured to, in response to the engine being off and a power request exceeding an engine-start threshold, delay an engine start when vehicle speed is below a predetermined value. Delaying an engine start may include providing an engine-start-threshold offset. The offset decreases as vehicle speed increases. The engine is started when the power request exceeds a sum of the engine-start threshold and the engine-start-threshold offset.