Disconnect Clutch Torque Control During Hybrid Engine Start
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Solution Overview
Problem
In hybrid electric vehicles, the control of the disconnect clutch during engine start is challenging due to delays in control signals between separate control modules, leading to potential overcapacity beliefs and undesired corrective actions in the electric machine, affecting drivability and torque control.
Innovation Solution
A controller is programmed to control the torque capacity of the disconnect clutch using a feedforward model of pressure applied, adjusting torque based on a ramp down phase, pressure differences, and rate of change, incorporating an offset value to compensate for signal delays and ensure accurate torque management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate control modules are used for clutch and electric machine control, then control functionality is improved, but signal delay between modules causes torque control inaccuracies
Solution Approach 1:
The patent combines the clutch control module and electric machine control module into a single integrated control module. This integration eliminates the signal delay between separate modules while maintaining all necessary control functionalities for both the clutch and electric machine during engine start operations
2Speed
If feedforward pressure model is used for torque capacity control, then responsiveness is improved, but ramp down phase causes torque overcapacity
Solution Approach 1:
The patent implements a feedback mechanism that monitors the actual pressure in the clutch pressure accumulator during the ramp down phase. When the pressure decreases below the feedforward model prediction, the system detects this deviation and adjusts the electric machine torque accordingly to prevent overcapacity conditions, thereby maintaining torque control accuracy while preserving responsive control
Data Source
AI summary
A vehicle includes an engine, an electric machine, a clutch, and a controller. The clutch is disposed between the engine and the electric machine. The controller is programmed to, in response to an engine start, close the clutch to transfer power from the electric machine to the engine to start the engine. The controller is further programmed to, in response to the engine start, control a torque capacity of the clutch during the engine start according to a model of a pressure applied to the clutch. The controller is further programmed to, in response to the engine start, control the torque of the electric machine based on an adjusted torque capacity of the clutch.