Wheel Lift Force Detection Using Strut-Mounted Vertical Acceleration
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Solution Overview
Problem
Existing traction control and anti-lock braking systems struggle to optimize braking and acceleration forces on uneven or wet road surfaces due to unknown tire contact forces, leading to inefficient vehicle stabilization and increased risk of wheel spin or lock.
Innovation Solution
Positioning an accelerometer with unique sensor axis orientations between a suspension strut and brake disc to accurately measure tire contact force, allowing for precise determination of tire contact forces and friction coefficients, which are then utilized by traction control and anti-lock braking systems to enhance vehicle stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If constant maximum braking force or propulsion force is applied to a wheel, then optimal braking or acceleration is achieved on dry flat surfaces, but the force becomes too high for suddenly unloaded wheels or too low for suddenly loaded wheels on uneven or wet surfaces
Solution Approach 1:
The system continuously monitors wheel acceleration using an accelerometer and feeds this information back to the control unit. The control unit calculates tire contact force based on the measured acceleration and adjusts the braking or propulsion force accordingly, creating a closed-loop control system that adapts to changing road conditions.
Solution Approach 2:
The system calculates and determines the tire contact force before applying optimal braking or propulsion force. By knowing the current tire contact force in advance, the control system can pre-adjust the braking force to the appropriate level, preventing wheel lock or spin before they occur.
2Adaptability or versatility
If an accelerometer with conventional sensor axis arrangement is used, then general vehicle acceleration measurement is achieved, but accurate measurement of vertical acceleration during sudden wheel loading or unloading is insufficient
Solution Approach 1:
The accelerometer is designed with an asymmetric sensor axis arrangement where one sensor axis is oriented vertically to specifically capture vertical acceleration during wheel loading or unloading events. This asymmetric configuration targets the specific measurement need rather than using a conventional symmetric arrangement.
Solution Approach 2:
The system adds a vertical measurement dimension to the accelerometer's sensor axes, enabling it to detect acceleration in the direction perpendicular to the road surface. This dimensional addition allows the sensor to capture vertical dynamics that conventional horizontal-axis accelerometers would miss.
3Ease of manufacture
If tire contact force is not known, then traction control and ABS can operate with constant force settings, but they cannot optimize braking or acceleration force for varying road conditions
Solution Approach 1:
The system replaces complex mechanical force sensing mechanisms with an electronic accelerometer-based measurement system. The accelerometer measures wheel acceleration, and the control unit calculates tire contact force electronically, avoiding the need for direct mechanical force sensors while achieving the same functional goal.
Solution Approach 2:
The accelerometer serves as an intermediary measurement device that indirectly determines tire contact force by measuring wheel acceleration. Rather than directly measuring the contact force between tire and road, the system uses acceleration as an intermediate parameter to infer the contact force through calculation.
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
Enables precise control of maximum drive and braking torques, improved vehicle stabilization, and enhanced safety by allowing stronger braking and acceleration on varied road conditions.
Implementation Method 1
at least one acceleration at one wheel of the motor vehicle in a vertical direction, i.e., in the direction of the ground... is taken into account
Data Source
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AI summary
The invention relates to an acceleration sensor having a fastening axis, which is configured to fasten the acceleration sensor to a carrier along the fastening axis by means of a screw, and a sensor element having a plurality of sensor axes. A linear combination of all sensor axes runs parallel to the fastening axis. The invention also relates to a motor vehicle having in each case at least one acceleration sensor which is arranged in each case between a spring leg and a brake disc of a front wheel of the motor vehicle, wherein each acceleration sensor has a sensor element having a plurality of sensor axes. A linear combination of all sensor axes of the acceleration sensor is orthogonal to a horizontal plane of the motor vehicle. In a method for determining a vertical tyre force (Fz) of a wheel of the motor vehicle, at least one acceleration (z̈R) at a wheel of the motor vehicle in the direction of the ground is taken into account in the determination.