AWD-2WD Switching Control Based on Slip and Lateral G
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Solution Overview
Problem
Conventional vehicle drive systems switch from all-wheel drive (AWD) to two-wheel drive (2WD) only at vehicle speeds of 0 km/h, restricting the timing of AWD to 2WD conversion and potentially leading to oversteering and reduced vehicle stability during vehicle movement, thereby compromising driving efficiency.
Innovation Solution
A vehicle drive system that includes a control device with slip-correlation and vehicle-movement-correlation acquisition means to dynamically switch between AWD and 2WD based on slip and movement conditions, allowing for more appropriate timing of drive state changes, including switching from AWD to 2WD during vehicle movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If switching from AWD to 2WD is permitted only at vehicle speed 0 km/h, then motor brush wear is reduced and fuel consumption is improved, but vehicle stability deteriorates during movement and switching timing is restricted
Solution Approach 1:
The patent implements dynamic switching between AWD and 2WD modes based on real-time vehicle conditions including speed, acceleration, steering angle, and wheel slip. The system transitions from static switching (only at 0 km/h) to dynamic switching (at multiple speed points), allowing optimal drive mode selection that balances fuel efficiency with vehicle stability during movement.
Solution Approach 2:
The patent changes multiple parameters simultaneously to enable safe AWD-to-2WD switching during movement: vehicle speed thresholds, acceleration rates, steering angle limits, and wheel slip conditions. By monitoring and adjusting these parameters together, the system determines appropriate switching timing that maintains vehicle stability while improving fuel consumption.
2Reliability
If AWD to 2WD switching is restricted to stationary conditions, then switching safety is maintained, but driving efficiency deteriorates due to prolonged AWD operation
Solution Approach 1:
The patent employs feedback control by continuously monitoring vehicle speed, acceleration, steering angle, and wheel slip conditions. This real-time feedback enables the system to assess switching safety dynamically and permit AWD-to-2WD transitions during movement when conditions are appropriate, thereby improving driving efficiency while maintaining switching safety.
Solution Approach 2:
The system uses its own operational parameters (speed, acceleration, steering angle, wheel slip) to determine switching timing. By self-assessing its current state against predefined safety criteria, the system autonomously decides when AWD-to-2WD switching is safe, eliminating the need for conservative stationary-only switching and improving driving efficiency.
3Productivity
If switching conditions are relaxed to permit AWD to 2WD during travel, then driving efficiency improves, but vehicle stability may be compromised during oversteering or lateral movement
Solution Approach 1:
The patent performs preliminary assessment of switching safety by evaluating multiple parameters (speed, acceleration, steering angle, wheel slip) before permitting AWD-to-2WD switching during movement. This preliminary check ensures that switching only occurs when vehicle conditions indicate stability, preventing oversteering or lateral movement issues while improving driving efficiency.
Solution Approach 2:
The system prepares for potential stability issues by setting conservative thresholds for switching parameters and requiring multiple conditions to be met simultaneously before permitting AWD-to-2WD transition. This cushioning approach creates a safety buffer that prevents switching during critical maneuvers while still allowing efficient switching during normal travel conditions.
Data Source
AI summary
A vehicle drive system, that can improve drive efficiency while maintaining vehicle stability, includes a step (S3, S105) in which a switch is made from 2WD to AWD on the basis of a cumulative slip point; a step (S12, S303) in which a switch is made from 2WD to AWD on the basis of a calculated lateral G; a step (S13, S109, S111) in which a switch is made from AWD to 2WD after the step (S3 or S105) under a first switching condition; and a step (S13, S306, S308) in which a switch is made from AWD to 2WD after the step (S12 or S303) under a second switching condition. The first switching condition and the second switching condition differ from one another.