Hybrid Powertrain Engine Speed Profiling for Clutch Synchronization
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Solution Overview
Problem
Conventional engine speed synchronization techniques for hybrid powertrains are slow and inaccurate, leading to noticeable noise/vibration/harshness (NVH) and requiring high calibration efforts.
Innovation Solution
A model-based control system using a linear quadratic integral (LQI) controller with gain scheduling, saturation, and integral factor freeze is employed to determine and control the engine speed profile for synchronization with an intermediate powertrain shaft, eliminating the need for empirical calibration and feedback-based controls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional heuristic or feedback-based controls are used for engine speed synchronization, then the synchronization process is simpler to implement, but the synchronization speed and accuracy deteriorate, resulting in noticeable NVH
Solution Approach 1:
The patent applies parameter changes by using a model-based approach that dynamically adjusts engine speed profile parameters (target speed, acceleration rate, torque requests) based on real-time powertrain state. This enables faster and more accurate synchronization compared to conventional fixed-parameter heuristic or feedback-based controls, while reducing NVH through optimized speed tracking.
2Measurement precision
If model-based control with LQI controller is used for engine speed synchronization, then synchronization accuracy and NVH reduction improve, but control system complexity increases
Solution Approach 1:
The patent replaces complex mechanical calibration processes with a model-based control system using LQI controller. Instead of relying on empirical calibration data and trial-and-error mechanical tuning, the system uses a mathematical model of the powertrain to predict and optimize engine speed profiles, achieving high synchronization accuracy without extensive calibration efforts.
Solution Approach 2:
The LQI controller performs self-optimization by using the powertrain model to automatically generate optimal speed profiles based on current operating conditions. The controller adapts to different scenarios (electric-only to hybrid mode transitions, varying load conditions) without requiring external calibration input, making the system self-sufficient and reducing development complexity.
3Power
If the first electric motor (BSG) is used to start the engine, then engine starting is achieved, but the motor's limited power prevents it from accelerating the engine to the required synchronization speed
Solution Approach 1:
The patent segments the engine acceleration process into two distinct phases: Phase 1 uses the BSG motor to start the engine and bring it to a preliminary speed, while Phase 2 uses the engine's own combustion torque to complete the acceleration to synchronization speed. This segmentation allows each component to operate within its capability envelope, overcoming the BSG's power limitation.
Solution Approach 2:
The BSG motor performs preliminary action by starting the engine and bringing it to an initial operating speed before the engine takes over. This preliminary acceleration prepares the engine for self-acceleration, allowing the transition to hybrid mode to proceed even though the BSG cannot directly achieve the final synchronization speed.
Data Source
AI summary
Techniques for synchronizing shaft speeds of a hybrid powertrain of a hybrid vehicle include, during a first phase of a synchronization process, starting an engine using a first electric motor and increasing a speed of an output shaft of the engine to a first speed that is less than a second speed of an intermediate powertrain shaft on an opposing side of a disconnect clutch relative to the engine output shaft, and during a subsequent second phase of the synchronization process, performing a model-based determination of a target speed profile for the engine to follow from the first speed to the second speed and controlling the engine to increase its speed according to the target speed profile, and closing the disconnect clutch when the speeds of the engine output shaft and the intermediate powertrain shaft are synchronized.