Hybrid Engine Speed Control for NVH and Efficiency Arbitration
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Solution Overview
Problem
Existing hybrid electric vehicle (HEV) powertrain control strategies fail to achieve optimal noise, vibration, and harshness (NVH) characteristics while maintaining best efficiency, as they do not consider NVH factors in adjusting engine speed and torque values.
Innovation Solution
A control strategy that calculates a battery power offset to adjust the target engine power command, ensuring a desired engine speed and vehicle speed relationship, taking into account battery state-of-charge, temperature, age, and balance, to achieve optimal NVH characteristics without clipping engine speed, and arbitrates operating variables for trade-offs between NVH, fuel economy, and exhaust gas quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If engine speed is controlled to achieve maximum efficiency, then fuel economy is improved, but noise, vibration and harshness characteristics deteriorate
Solution Approach 1:
The control system dynamically adjusts engine speed based on real-time arbitration between efficiency objectives and NVH objectives. The system transitions between different operating modes (efficiency-oriented vs. NVH-oriented) depending on current vehicle conditions, battery state, and driver demand, making the engine speed control flexible and adaptive rather than fixed.
Solution Approach 2:
The system changes the engine speed parameter based on the arbitration outcome between efficiency and NVH considerations. When NVH becomes a priority, the engine speed is adjusted to values that reduce vibration and noise, even if this means operating away from the peak efficiency point. This parameter adjustment resolves the contradiction by allowing the system to shift between different operating regimes.
2Object-affected harmful factors
If engine speed is reduced to improve NVH characteristics, then noise, vibration and harshness are improved, but engine efficiency deteriorates
Solution Approach 1:
The battery acts as an intermediary that enables the system to decouple engine speed from vehicle speed. When NVH improvement is prioritized, the battery can compensate for the power deficit created by operating the engine at lower, quieter speeds. This intermediary energy storage device allows the engine to operate in NVH-optimized regimes without significantly impacting overall vehicle performance or efficiency.
Solution Approach 2:
The system applies partial battery power to compensate for the efficiency loss when operating in NVH-optimized mode. Rather than requiring the engine to operate at peak efficiency continuously, the battery provides supplemental power during periods when the engine operates at quieter, less efficient speeds, allowing the system to tolerate temporary efficiency reductions in exchange for sustained NVH improvement.
3Object-affected harmful factors
If battery power is increased to compensate for engine power reduction, then NVH characteristics are improved, but battery state-of-charge decreases
Solution Approach 1:
The control system continuously monitors battery state-of-charge and uses this feedback to modulate the arbitration between efficiency and NVH objectives. When battery charge is high, the system can afford to prioritize NVH by reducing engine speed and using battery power for compensation. When battery charge becomes low, the feedback mechanism shifts the arbitration toward efficiency priorities to recharge the battery, creating a self-regulating system that manages the trade-off dynamically.
Solution Approach 2:
The system employs periodic alternation between efficiency-oriented and NVH-oriented operating modes, regulated by battery state-of-charge thresholds. During high charge states, the system operates in NVH-optimized mode, drawing power from the battery. When charge depletes to a threshold, it switches to efficiency-oriented mode to recharge the battery, creating a periodic cycle that balances NVH improvement with battery energy management.
Data Source
AI summary
A control strategy is disclosed for regulating speed of an engine in a hybrid electric vehicle powertrain that includes an electric motor and gearing. An electrical power flow path and a mechanical power flow path are established. Electrical power is coordinated with mechanical power to effect an arbitrated engine speed for a given power demand that will result in an acceptable noise, vibration and harshness (NVH) characteristic for the powertrain and an acceptable powertrain efficiency.