Dual-Motor Hybrid Engine Start Control for Smooth Low-Speed NVH
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Solution Overview
Problem
Dual-motor hybrid power systems experience unsmooth engine starts due to rapid drag torque increases, leading to start impacts, especially when the P1 motor or clutch drag torque is maximized, and poor NVH properties during 12V starts at low vehicle speeds, affecting safety and user experience.
Innovation Solution
A start method that includes a pre-dragging torque strategy, fuel injection control strategy, and clutch start waiting strategy, where the system determines the appropriate start strategy based on motor and vehicle state data to manage drag torque and fuel injection timing, preventing motor jitter and improving start smoothness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the drag torque of P1 motor or clutch is directly increased to maximum, then the engine can be started quickly, but the drag torque rises too fast causing impact and unsmooth engine start
Solution Approach 1:
The patent applies preliminary action by pre-heating the drag torque before full engagement. The control method gradually increases drag torque from an initial value to a maximum value over a predetermined time period, rather than abruptly applying full torque. This preliminary torque application prepares the engine for smooth starting while avoiding sudden impacts that would cause harmful vibrations and noise.
2Loss of time
If the engine starts to inject fuel when the drag torque has not been unloaded yet, then the fuel injection can begin early, but it results in start impact
Solution Approach 1:
The patent employs feedback control by continuously monitoring drag torque levels and using this information to determine the optimal fuel injection timing. The control unit delays fuel injection until drag torque falls below a predetermined threshold, ensuring that fuel is injected at the precise moment when drag torque has been sufficiently reduced. This feedback mechanism prevents start impact while minimizing fuel injection delay.
3Adaptability or versatility
If 12V start is adopted when vehicle speed is low, then the engine can be started at low speed, but the noise and oscillation are large and NVH property is poor
Solution Approach 1:
The patent applies dynamics by enabling the vehicle to dynamically switch between different starting modes based on real-time operating conditions. The system can select between 12V starter mode and P1 motor mode depending on vehicle speed, battery state, and other parameters. This dynamic adaptability allows the system to use the quieter P1 motor for low-speed starts when appropriate, thereby reducing noise and oscillation while maintaining low-speed start capability.
Data Source
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AI summary
Provided is a start method for an engine in a dual-motor hybrid power system, which belongs to the technical field of vehicles. The dual-motor hybrid power system includes the engine, a first motor connected to the engine, and a clutch connected between the first motor and a gear shift system. The start method includes: when receiving an engine start request, acquiring a current state of the first motor and current state data of a vehicle; determining an available start strategy according to the current state of the first motor and the current state data of the vehicle, and executing the available start strategy to start the engine, wherein the available start strategy includes at least one of the following: a prefill torque strategy, a fuel injection control strategy and a clutch start waiting strategy. Also disclosed are an apparatus using the method and a vehicle.