Wheel Attitude Control Using Tire Acceleration Sensors
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Solution Overview
Problem
Existing methods for controlling wheel attitude during vehicle braking, such as those using strain gauges and camber adjustment, fail to accurately maintain a symmetrical contact patch shape, leading to reduced braking force due to changes in wheel load and attitude.
Innovation Solution
A wheel attitude control method and device that utilizes two acceleration sensors, one at the center and one off-center on the tire, to calculate the contact length and generate a control signal for the suspension control device to adjust camber and toe angles, maintaining a stable contact patch shape during braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If strain gauges are mounted at two symmetrical positions to measure contact length, then the measurement system is simple, but it is impossible to accurately ascertain the shape change in the contact length which depends upon the wheel link mechanism
Solution Approach 1:
The patent divides the contact length measurement into multiple segments by mounting strain gauges at three or more positions around the tire circumference (including center and off-center positions). This segmentation allows accurate detection of shape changes in different regions of the contact patch, enabling precise ascertainment of contact length variations caused by wheel link mechanism changes.
Solution Approach 2:
The patent employs asymmetric gauge arrangement by placing strain gauges at both center and off-center positions relative to the tire width direction. This asymmetric configuration enables detection of asymmetric shape changes in the contact patch that occur during braking, which cannot be detected by symmetric two-point measurement alone.
2Device complexity
If the wheel attitude is not controlled during braking, then the suspension system remains simple, but the contact patch shape becomes asymmetrical leading to reduced braking force
Solution Approach 1:
The patent implements a feedback control system where strain gauge measurements of contact patch shape are continuously monitored, and suspension actuator commands are generated based on detected deviations from optimal contact patch geometry. This closed-loop feedback maintains symmetrical contact patch shape during braking, maximizing braking force while managing suspension complexity through selective actuator engagement.
Solution Approach 2:
The system performs preliminary detection of contact patch shape changes using strain gauges before significant performance degradation occurs. By detecting early shape asymmetries caused by wheel attitude changes, the system can proactively adjust suspension parameters to maintain optimal contact patch geometry, preventing braking force reduction rather than merely responding to it.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method effectively maintains a stable contact patch shape, enhancing braking force by compensating for load-induced changes in wheel attitude, thereby improving braking performance.
Implementation Method 1
obtains acceleration data indicating acceleration of the tire in a radial direction from two acceleration sensors, one at a center position of a tire tread and the other at an off-center position spaced apart from the center position toward the shoulder
Implementation Method 2
When braking a vehicle by imparting a braking force to wheels, each of front wheels undergoes an increase in load due to this braking, and a camber angle and a toe angle indicating wheel attitude are changed. This change depends upon a wheel mounting link mechanism for wheel attachment.
Data Source
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Figure 3A~3B
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AI summary
A wheel attitude control method of the invention comprises the steps of: chronologically obtaining acceleration data in a radial direction of a tire at a center position of a tire tread and at an off-center position spaced apart from the center position toward a shoulder; obtaining respective contact lengths at the center position and the off-center position from the acceleration data; and controlling a wheel attitude, which varies in accordance with changes in a load applied to the wheel when the braking force is imparted to the wheel, based on the obtained contact length at the center position and the obtained contact length at the off-center position.