Freefall Detection with Spin Using Dual Tri-Axis Accelerometers
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Solution Overview
Problem
Current freefall detection systems in portable electronic devices cannot accurately distinguish between simple freefall and freefall with spin, leading to potential false detection during everyday activities like jogging or dancing, and are unable to effectively protect sensitive components from impact damage.
Innovation Solution
A system utilizing an improved algorithm combined with two tri-axis accelerometers to analyze acceleration vectors and determine if they are in the same plane, indicating freefall with spin, which generates a control signal to secure the device's hard drive or other components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single tri-axis accelerometer with high-G threshold is used to detect freefall, then simple freefall can be detected, but freefall with spin cannot be accurately detected because the accelerometer measures over 3.0 G during spin
Solution Approach 1:
The system divides the detection task into two parts: a first tri-axis accelerometer detects overall acceleration changes, while a second tri-axis accelerometer specifically detects spin-induced centrifugal and centripetal forces. This segmentation allows each sensor to focus on specific aspects of the fall detection problem, improving overall accuracy.
Solution Approach 2:
The patent transitions from single-dimension acceleration detection to multi-dimensional analysis by incorporating a second tri-axis accelerometer that provides additional spatial information. The system analyzes acceleration vectors in three-dimensional space to distinguish between simple freefall and spinning freefall, adding dimensional complexity to the detection capability.
2Measurement precision
If acceleration threshold is set low to detect spinning freefall, then spin detection improves, but false detection during everyday activities like jogging or dancing increases
Solution Approach 1:
The system uses feedback from two accelerometers to continuously monitor acceleration patterns. By comparing data from both sensors and analyzing the relationship between gravity vector and measured acceleration vectors, the system can distinguish between legitimate freefall events and everyday activities, reducing false detections while maintaining sensitivity.
Solution Approach 2:
The detection algorithm dynamically adjusts its analysis based on real-time accelerometer data. The system evaluates whether measured acceleration vectors align with expected patterns for freefall versus everyday activities, allowing adaptive response to different motion scenarios rather than relying on fixed thresholds.
3Loss of time
If conventional freefall detection algorithm is used, then simple freefall can be detected, but detection time is insufficient for protective mechanism to react
Solution Approach 1:
The system performs preliminary analysis of acceleration patterns using two sensors to detect the onset of freefall with spin earlier in the event sequence. By identifying spin characteristics through comparative vector analysis, the system can trigger protective mechanisms before impact occurs, providing sufficient reaction time.
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
Accurately detects freefall with spin in as little as 60 milliseconds, allowing sufficient time for protective measures to engage and preventing data loss from impact, with potential applicability beyond portable devices to other objects like automobiles.
Implementation Method 1
An accelerometer at rest measures 1 G (gravity) of acceleration
Implementation Method 2
the accelerometer will measure over 3.0 G during much of the fall as the spin causes centrifugal and centripetal acceleration to be placed on the object
Implementation Method 3
the accelerometer will measure over 3.0 G during much of the fall as the spin causes centrifugal and centripetal acceleration to be placed on the object
Implementation Method 4
The algorithm analyzes the inputs to determine when centrifugal or centripetal acceleration is occurring which indicates that the object is spinning and in freefall. In particular, the acceleration vectors from each of the tri-axis accelerometers are compared to determine whether they are both in the same plane
Data Source
AI summary
A system and method detect freefall associated with an object that is spinning or tumbling as it falls. Two tri-axis accelerometers provide inputs to an algorithm that detects the freefall of a spinning object that would not otherwise be detected by a conventional freefall detection system, due to the centrifugal and centripetal forces being placed on the falling object as it spins. The system can be used to detect the freefall of portable devices with onboard memory or hard disk drives, allowing the devices to have time to park the read/write head and reduce the potential of losing data that can be damaged by impact. This freefall detection system may be applied to such portable devices as notebook computers, PDAs, MP3 players, digital cameras, mobile phones and even automobiles.