Hybrid Vehicle Engine Restart RPM Control
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Solution Overview
Problem
Hybrid vehicles experience noise and reduced ride comfort due to unstable engine RPM changes during restart after Start & Stop Coasting (SSC) and Neutral Coasting Control (NCC), affecting fuel economy and driving performance.
Innovation Solution
A method of controlling the engine and transmission using a controller to manage Mild Hybrid Starter & Generator (MHSG) RPM, implementing PID control to synchronize engine and transmission RPM, and adjusting ignition timing and throttle opening to follow target RPM gradients, thereby ensuring consistent engine behavior and smooth acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engine is restarted after releasing SSC or during NCC acceleration, then the vehicle can resume normal operation, but unstable engine RPM changes occur causing noise and reduced ride comfort
Solution Approach 1:
The controller pre-calculates the target RPM gradient for the MHSG based on current operating conditions (clutch state, battery charge/discharge status) before engine restart or NCC acceleration. This preliminary determination of the ideal RPM trajectory allows the engine control system to proactively adjust ignition timing and throttle opening to prevent unstable RPM changes and associated noise, rather than reacting after the problem occurs.
Solution Approach 2:
The controller continuously monitors the actual MHSG RPM and compares it with the target RPM gradient. Based on this feedback, the system dynamically adjusts ignition timing and throttle opening to maintain RPM stability during engine restart and NCC acceleration. This closed-loop control ensures that any deviations from the desired RPM profile are corrected in real-time, preventing noise and vibration while maintaining reliable operation.
2Object-affected harmful factors
If the MHSG RPM is controlled to follow target RPM gradient, then ride comfort and noise are improved, but additional control complexity is introduced
Solution Approach 1:
The existing MHSG motor, originally designed for starting the engine and regenerative braking, is made multi-functional by also using it for RPM control during NCC acceleration and engine restart. The same MHSG motor and control infrastructure are leveraged for multiple purposes, avoiding the need for additional dedicated control hardware while achieving improved RPM stability and reduced noise during transitional operating conditions.
Solution Approach 2:
The controller adjusts engine operating parameters (ignition timing and throttle opening) based on the determined target RPM gradient. By dynamically changing these parameters in response to the desired RPM trajectory, the system achieves smooth RPM transitions and reduced noise without requiring complex mechanical modifications. The control strategy modifies existing parameters rather than introducing new system components.
3Stability of the object's composition
If the engine RPM is controlled during restart, then acceleration smoothness is improved, but response time may be delayed
Solution Approach 1:
The controller dynamically adjusts the target RPM gradient based on real-time operating conditions, including clutch engagement state and battery charge/discharge requirements. Rather than using a fixed, conservative RPM profile that would ensure smoothness but delay response, the system adapts the RPM trajectory to balance smoothness and responsiveness. This dynamic approach allows faster acceleration when conditions permit while maintaining smooth transitions when stability is prioritized.
Solution Approach 2:
The controller pre-determines the optimal target RPM gradient based on current operating conditions before initiating engine restart or NCC acceleration. By calculating the ideal RPM trajectory in advance considering factors like clutch state and battery status, the system can execute a pre-planned control strategy that achieves both smooth acceleration and rapid response. The preliminary action eliminates delays associated with reactive control adjustments during the acceleration process.
Data Source
AI summary
A method of controlling an engine and a transmission of a vehicle includes: determining, by a controller, whether the engine is restarted after releasing the vehicle's SSC (Start & Stop coasting) or whether the vehicle is accelerating during NCC (Neutral Coasting control), determining an RPM and gear stage of the transmission if it is determined that the engine is restarted after releasing the vehicle's SSC or the vehicle is accelerating during NCC, determining a mild hybrid starter and generator (MHSG) target RPM and an MHSG target RPM gradient of the vehicle, performing, by the controller, MHSG RPM control of the vehicle to follow the MHSG target RPM and the MHSG target RPM gradient, determining whether the MHSG RPM slips compared to the MHSG target RPM, and performing proportional-integral-derivative (PID) control to follow the MHSG target RPM if the MHSG RPM slips compared to the MHSG target RPM.