Hybrid AWD Torque Split Control for Smooth Engine Engagement
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Solution Overview
Problem
Hybrid vehicles experience jerks and reduced comfort due to imprecision in clutch mechanisms and gearboxes when changing drive modes, particularly when the combustion engine engages the wheels.
Innovation Solution
A method for distributing drive torque in hybrid vehicles that anticipates changes in the operating state of the thermal engine and mechanical coupling, adjusting torque setpoints of electric machines to smoothly transition between drive modes, incorporating a waiting period to confirm the need and compensate for engine and coupling state changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the combustion engine engages the wheels through clutch mechanism and gearbox when changing drive modes, then the vehicle can switch between different drive modes (electric-only to hybrid), but the imprecision in clutch mechanism and gearbox causes jerks and reduces passenger comfort
Solution Approach 1:
The control method anticipates the need for combustion engine engagement before it actually occurs. The system forecasts when the engine will be needed and pre-adjusts the torque distribution between electric machines to compensate for the upcoming mechanical coupling. This preliminary action allows the electric machines to take over smoothly during the engine engagement process, preventing jerks and maintaining passenger comfort while enabling drive mode switching.
2Adaptability or versatility
If the clutch mechanism and gearbox are used to engage the combustion engine to the wheels, then drive mode changes can be implemented, but the mechanical imprecision adds jerk and reduces drive uniformity
Solution Approach 1:
The control system introduces an intermediary approach by using the electric machines as a buffer between the combustion engine and the wheels during engagement. Instead of directly coupling the engine to the wheels through the imprecise clutch and gearbox, the system mediates the torque transmission through the electric machines, which can adjust their torque output smoothly. This intermediary role of the electric machines compensates for the mechanical imprecision and maintains drive uniformity.
Solution Approach 2:
The system dynamically changes the torque parameters of the electric machines in anticipation of engine engagement. By modifying the torque setpoints of the electric machines before and during the engine engagement process, the system compensates for the mechanical imprecision of the clutch and gearbox. This parameter adjustment ensures smooth torque distribution and maintains drive uniformity throughout the drive mode transition.
3Productivity
If the torque distribution is changed abruptly when the combustion engine engages, then the drive mode switch is achieved quickly, but the jerk perceived by passengers increases and comfort deteriorates
Solution Approach 1:
The control system performs preliminary adjustments to the torque distribution before the combustion engine actually engages. By forecasting the engine engagement need and pre-modifying the torque setpoints of the electric machines, the system prepares the torque distribution in advance. This allows the drive mode switch to be executed quickly while maintaining smooth torque transitions, thereby achieving both fast switching speed and passenger comfort.
Data Source
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AI summary
The invention relates to a method for drive torque splitting in a hybrid motor vehicle having four drive wheels. The vehicle has a first drive train driven by a first electrical machine, and by a heat engine via a first coupling system; and a second drive train driven by a second electrical machine. The method comprises the following steps: (a) driving (100) the vehicle according to a first torque split between the first and second drive train; (b) anticipating (102) a need to change the state of operation and the state of coupling of the heat engine to the first drive train, which requires a second torque split between the first drive train and the second drive train; and (c) changing (108) from the first to the second torque split by modifying a torque set point output by the first electrical machine to the first axle, and the second electrical machine to the second axle.