Vehicle AWD Clutch Control for Axle Speed Difference
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Solution Overview
Problem
Existing vehicle traction control and all-wheel drive systems face challenges in efficiently managing speed differences between axles, leading to parasitic losses and reduced fuel economy due to open clutches, which can cause wheel slip and decreased mobility.
Innovation Solution
A vehicle system with first and second axles coupled by a driveshaft, featuring first and second clutches that isolate the driveshaft from loads and a controller that closes the clutches to reduce speed differences between axles, ensuring they remain within specific thresholds, thereby optimizing power distribution and reducing parasitic losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the clutches are kept open to reduce parasitic losses and improve fuel economy, then fuel economy is improved, but wheel slip increases and mobility decreases
Solution Approach 1:
The clutch system dynamically transitions between open and closed states based on real-time speed difference detection. When speed differences between axles exceed a threshold, the clutches automatically close to engage all-wheel drive, and open when speed differences are within acceptable ranges, optimizing both fuel economy and mobility as conditions change
Solution Approach 2:
The controller continuously monitors the speed difference between the first and second axles and uses this feedback to control the clutch states. This closed-loop control ensures the system responds appropriately to actual operating conditions, closing clutches only when speed differences indicate a need for all-wheel drive engagement
2Reliability
If the clutches are closed to reduce speed differences between axles, then wheel slip is reduced and mobility is improved, but parasitic losses increase and fuel economy decreases
Solution Approach 1:
The system dynamically adjusts clutch engagement based on real-time speed difference measurements. Rather than maintaining a fixed state, the clutches transition between open and closed positions according to whether speed differences exceed predetermined thresholds, allowing the system to optimize the trade-off between mobility and fuel consumption
Solution Approach 2:
The controller changes the operational parameters of the clutch system by closing clutches only when speed differences between axles exceed a specific threshold. This parameter-based control ensures clutches are engaged only when necessary for maintaining mobility, minimizing the impact on fuel economy
3Loss of energy
If the driveshaft is isolated from loads through open clutches, then parasitic losses are reduced, but speed differences between axles increase
Solution Approach 1:
The controller uses feedback from speed sensors monitoring the first and second axles to determine when to close the clutches. When the measured speed difference exceeds a threshold, the controller closes the clutches to reconnect the driveshaft and eliminate the speed difference, preventing excessive parasitic losses while maintaining energy efficiency
Solution Approach 2:
The system changes the load isolation parameter by transitioning the clutch state from open to closed when speed differences become excessive. This parameter change reconnects the driveshaft to the axle with higher speed difference, equalizing speeds and reducing parasitic losses without continuously engaging the all-wheel drive system
Data Source
AI summary
A vehicle includes a first axle, second axle, first clutch, second clutch, and controller. The first and second axles are coupled by a driveshaft. The first and second clutches are configured to isolate the driveshaft from loads transferred through the first and second axles, respectively, when open. The controller is programmed to, in response to a difference between output speeds of the first and second axles exceeding a first threshold, close the second clutch, reduce the difference such that it is below a second threshold, and close the first clutch.