4WD Controller Road Surface Condition Determination
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Solution Overview
Problem
Conventional controllers for four-wheel-drive vehicles fail to accurately determine road surface conditions, especially during steady traveling states where the vehicle is moving at constant speed on a flat road with low acceleration, leading to potential misclassification of road friction levels.
Innovation Solution
A controller for a driving force transmitting apparatus that calculates a command torque based on the vehicle's traveling state and road surface condition, and determines a high-μ condition when the vehicle speed is above a threshold and the slip ratio of main drive wheels is below a certain value for a prescribed time, allowing for accurate road surface condition assessment even in steady states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the controller calculates low-μ information based on slip ratio and acceleration operation, then the road surface condition can be determined during dynamic states, but the determination accuracy deteriorates during steady traveling states where acceleration is small
Solution Approach 1:
The controller dynamically switches between two different road surface condition determination methods based on the vehicle's traveling state. During acceleration states, it uses the conventional method based on slip ratio and acceleration operation. During steady traveling states, it switches to a method based on comparing actual fuel consumption with calculated fuel consumption. This dynamic adaptation resolves the contradiction by ensuring high determination accuracy across all traveling states.
Solution Approach 2:
The invention changes the parameters used for road surface condition determination based on the traveling state. Instead of relying solely on slip ratio and acceleration operation, it introduces fuel consumption parameters (actual fuel consumption from sensor and calculated fuel consumption based on engine output) as alternative indicators. This parameter substitution enables accurate road surface condition determination during steady traveling states where acceleration-based methods fail.
2Reliability
If the controller uses slip ratio and acceleration operation to determine road surface condition, then the determination can be made during acceleration states, but the system fails to accurately determine road surface condition during steady traveling states
Solution Approach 1:
The controller utilizes existing sensor data (fuel consumption sensor, engine output data) that is already being collected for other control functions. By repurposing this existing data for road surface condition determination during steady traveling states, the system improves reliability without significantly increasing operational complexity. The fuel consumption information is already available from normal vehicle operation.
Solution Approach 2:
The invention makes the controller's determination system multi-functional by enabling it to accurately determine road surface conditions across all traveling states (acceleration, deceleration, and steady traveling). The dual-method approach ensures that the system maintains high reliability whether the vehicle is accelerating or maintaining constant speed, making the road surface condition determination universally applicable.
Data Source
AI summary
A controller for a driving force transmitting apparatus mounted in a four-wheel-drive vehicle, includes: a driving force controller configured to calculate a command torque indicating a driving force to be transmitted to the sub-drive wheels via the driving force transmitting apparatus based on a traveling state of the four-wheel-drive vehicle and a road surface condition, and to control the driving force transmitting apparatus based on the command torque; and a road surface condition determiner configured to determine that the road surface condition is a high-μ condition when a duration of a non-slipping state where a vehicle speed is equal to or higher than a prescribed value and a slip ratio of each of both the main drive wheels is lower than a prescribed value has become equal to or longer than a prescribed time.