Hybrid Powertrain Controller Engine Start Adaptability
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Solution Overview
Problem
Existing hybrid-electric powertrain systems face challenges in efficiently controlling engine starts, particularly in managing the disconnect clutch and engine speed targets based on varying states of driving, which affects responsiveness and fuel efficiency.
Innovation Solution
A controller is programmed to command specific speed targets and disconnect clutch operations based on detected states of driving, adjusting engine speed targets and clutch engagement thresholds to optimize engine starts and responsiveness, with different offsets and thresholds for different driving scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed engine speed target is used during engine start, then the control system is simple to implement, but the responsiveness and fuel efficiency cannot be optimized for different driving conditions
Solution Approach 1:
The engine speed target is made dynamic by adjusting it based on the detected state of driving. The controller determines different speed targets (first speed target vs. second speed target) according to the driving state, allowing the system to adapt to varying driving conditions while maintaining a relatively simple control structure through predefined adjustment rules.
Solution Approach 2:
The control system changes the engine speed target parameter based on the state of driving. When a first driving condition is detected, a first speed target is commanded; when a second driving condition is detected, a second speed target is commanded. This parameter adjustment enables adaptability without requiring complex real-time optimization algorithms.
2Speed
If the disconnect clutch is locked immediately during engine start, then the engine coupling is achieved quickly, but driveline disturbances increase and mechanical stress is heightened
Solution Approach 1:
Before locking the disconnect clutch, the controller commands the engine speed to reach a target value that is determined based on the motor speed and the state of driving. This preliminary speed adjustment ensures that when the clutch is locked, the speed difference between engine and motor is minimized, reducing driveline disturbances and mechanical stress.
Solution Approach 2:
The controller continuously monitors the state of driving and the speeds of both the engine and motor. Based on this feedback, the controller adjusts the engine speed target and determines the appropriate timing for clutch locking, ensuring optimal coupling conditions are met before engagement to minimize harmful disturbances.
3Productivity
If engine speed target is increased for faster response, then vehicle responsiveness improves, but fuel consumption increases during engine start
Solution Approach 1:
The engine speed target parameter is adjusted based on the state of driving rather than being fixed at a high value. The controller determines appropriate speed targets that balance responsiveness requirements with fuel efficiency considerations for different driving conditions, avoiding unnecessary high-speed engine starts when full responsiveness is not required.
Solution Approach 2:
The engine speed target is made dynamic and adaptive to actual driving conditions. The controller evaluates the state of driving and commands speed targets that are optimized for each scenario, providing fast response when needed while conserving fuel during normal operating conditions, thus resolving the trade-off between productivity and energy loss.
Data Source
AI summary
A hybrid vehicle includes an electric machine, an engine selectively coupled to the electric machine by a disconnect clutch, and a controller. The controller is programmed to, in response to a change in the driver-demanded torque necessitating starting of the engine: determine a state of driving (SOD) based on the change in driver-demanded torque, wherein the SOD is indicative of a desired responsiveness of the vehicle, and the desired responsiveness increases as SOD increases; command a speed target to the engine equal to a predicted motor speed associated with the driver-demanded torque plus an offset that is based on the SOD; and command a capacity to the disconnect clutch at a rate and a magnitude based on the SOD.