Engine Disconnect Clutch Control for Smooth Hybrid Mode Transitions
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Solution Overview
Problem
Hybrid vehicles face challenges in accurately controlling the disconnect clutch to ensure smooth transitions between engine and electric machine operation, due to communication delays and imperfections in sensor signals, leading to inconsistencies in clutch torque delivery during engine starting and mode transitions.
Innovation Solution
A vehicle controller is programmed to command torque to the electric machine based on a learned time constant selected from a family of candidate time constants, compared to measured pressure data from previous clutch engagements, using a clutch model that adapts to account for signal lag and imperfections, generating a torque lead value to compensate for delays and ensure precise clutch engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed clutch model is used for controlling the disconnect clutch, then the control system is simple, but the clutch torque delivery becomes inconsistent due to signal lag and sensor imperfections
Solution Approach 1:
The clutch model is made dynamic by allowing the time constant to vary based on operating conditions. The controller selects from multiple candidate time constants (e.g., 50ms, 100ms, 200ms) depending on the current state, transforming a static model into an adaptive one that responds to changing system characteristics and compensates for signal lag.
Solution Approach 2:
The invention changes the parameter (time constant) of the clutch model based on measured pressure data from previous engagements. By comparing actual pressure responses with predicted responses from candidate models, the system identifies the best-matching time constant and uses it for future control, thereby improving torque delivery consistency.
2Productivity
If the clutch engagement is accelerated to improve responsiveness, then the transition speed increases, but torque spikes and drivability issues occur
Solution Approach 1:
The controller applies torque to the electric machine in advance of the actual clutch engagement. By using the adaptive clutch model to predict the engagement timing and characteristics, the system pre-conditions the electric machine torque, ensuring that when the clutch actually engages, the torque is already aligned and no spikes occur.
Solution Approach 2:
The system uses feedback from measured pressure data during and after clutch engagements to continuously refine the clutch model. This feedback loop allows the controller to learn the actual clutch behavior and adjust future torque commands accordingly, preventing torque spikes while maintaining fast transitions.
3Ease of operation
If torque is commanded to the electric machine without compensation for clutch delays, then the control response is fast, but smooth transitions between operational modes are not achieved
Solution Approach 1:
The controller commands torque to the electric machine before the clutch fully engages, using the adaptive model to predict the engagement timing. This preliminary torque application ensures that when the clutch connects, the torque is already present and smoothly transferred, eliminating delays and jerky transitions.
Solution Approach 2:
The system anticipates the clutch delay and applies counteracting torque commands to the electric machine in advance. By pre-applying the necessary torque and using the adaptive model to compensate for the known delay characteristics, the system eliminates the harmful effect of the delay, achieving smooth transitions without sacrificing response time.
Data Source
AI summary
A hybrid vehicle includes an engine, an electric machine, and a clutch configured to selectively couple the engine to the electric machine. A controller is programmed to command a torque to the electric machine based on a clutch model that includes a learned time constant previously selected using a family of candidate time constants based on a comparison of the family to measured pressure data of a previous engagement of the clutch.