Vehicle Tilt Sensor Using Dual Accelerometers and Arcsine Selection
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Solution Overview
Problem
Existing vehicle tilt sensors fail to accurately determine tilt angles due to errors caused by centripetal force, travel acceleration, and vertical acceleration from sloped terrain, leading to unreliable measurements.
Innovation Solution
A tilt sensing system utilizing two accelerometers aligned with orthogonal axes and a data processor that applies arcsine and arccosine equations to differentiate between vertical and lateral acceleration, selecting the appropriate tilt calculation to compensate for terrain changes and ensure accurate tilt estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single accelerometer is used to determine tilt angle, then the device complexity is reduced, but the measurement precision deteriorates due to inability to differentiate between vertical and lateral acceleration
Solution Approach 1:
The tilt measurement function is segmented into two independent measurement channels: one accelerometer measures acceleration along the longitudinal axis (x-axis) to determine pitch angle, while the other measures acceleration along the lateral axis (y-axis) to determine roll angle. This segmentation allows each sensor to focus on a specific tilt component, improving measurement precision while maintaining relatively simple device complexity.
Solution Approach 2:
The system transitions from single-axis measurement to two-axis measurement by adding a second accelerometer oriented perpendicular to the first. This dimensional expansion enables simultaneous measurement of both pitch and roll angles, resolving the ambiguity that plagues single-accelerometer systems and significantly improving tilt angle measurement accuracy.
2Device complexity
If traditional arc-cosine equation is used for tilt calculation, then the calculation is simple, but the reliability deteriorates due to sensitivity to vertical acceleration from terrain changes
Solution Approach 1:
The system changes the calculation parameter from using vertical acceleration (z-axis) to using lateral acceleration (x-axis and/or y-axis). By applying arc-sine equations to horizontal acceleration components rather than arc-cosine to vertical acceleration, the system becomes insensitive to vertical acceleration disturbances from terrain changes, thereby improving reliability while maintaining calculation simplicity.
Solution Approach 2:
The invention converts the harmful effect of vertical acceleration (from bumps and terrain changes) into a beneficial selection criterion: when vertical acceleration is detected (indicating terrain disturbance), the system automatically relies more on the horizontal acceleration-based tilt calculation, which remains accurate. This transforms the disturbance into a trigger for using the more reliable calculation method.
3Productivity
If accelerometer measurements are used during vehicle maneuvers, then the productivity is maintained, but the measurement precision deteriorates due to centripetal force and travel acceleration interference
Solution Approach 1:
The system segments the acceleration measurements into distinct components: vertical acceleration (affecting both axes) and horizontal acceleration (specific to each axis). By analyzing the pattern of acceleration across both accelerometers, the system can identify when centripetal or travel acceleration is present and selectively use only the unaffected accelerometer data for tilt calculation, maintaining precision during maneuvers.
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 system provides accurate and reliable tilt measurements by compensating for transient centripetal and vertical accelerations, improving tilt estimation accuracy during turns, braking, and traversing sloped or rough terrain.
Implementation Method 1
a first accelerometer for measuring a first acceleration level associated with a first axis of the vehicle
Implementation Method 2
A second accelerometer measures a second acceleration level associated with a second axis of the vehicle that is generally perpendicular to the first axis
Data Source
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AI summary
A tilt sensor (11) and method comprises a first accelerometer (10) for measuring a first acceleration level associated with a first axis of the vehicle, A second accelerometer (12) measures a second acceleration level associated with a second axis of the vehicle that is generally perpendicular to the first axis. A data processor (30) is capable of determining an arcsine-derived tilt based on an arcsine equation and the determined first acceleration level The data processor (30) is capable of determining an arc-cosine-derived tilt based on an arccosine equation and the determined second acceleration level. The data processor (30) comprises a selector (e.g., 24) for selecting the arcsine-derived tilt as the final tilt of the vehicle if the determined arcsine-derived tilt is lesser than the determined arccosine derived tilt such that the final tilt compensates for vertical acceleration associated with changes in the terrain In the direction of travel of the vehicle.