Ultrasonic Locationing Using Time Difference of Arrival Measurements
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Solution Overview
Problem
Current ultrasonic locationing systems using time difference of arrival (TDOA) information face challenges in achieving high accuracy, confidence, and fast determination of device location, particularly with increasing numbers of microphones, as they often result in non-linear equations with tradeoffs in accuracy, run time, and coding complexity.
Innovation Solution
The system introduces arbitrary flight times to TDOA information, allowing for a binary search to narrow down the location error to below an accuracy threshold, using a geometric approach with a central microphone and peripheral microphones to calculate intersection points and test errors, ensuring high accuracy and fast determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If hyperbolic positioning with multiple microphones is used to improve location accuracy, then measurement precision improves, but device complexity and computation time increase due to non-linear equations
Solution Approach 1:
The patent transforms the TDOA problem from using time differences directly to using range differences (distance differences) as the measurement parameter. This parameter change allows the location problem to be formulated as solving linear equations rather than non-linear equations, significantly reducing computational complexity while maintaining location accuracy using a minimal set of three microphones
Solution Approach 2:
The patent divides the location determination process into two distinct stages: first solving for the x,y coordinates using range difference measurements from three microphones through linear equations, then separately determining the z coordinate (height) using the known microphone spacing and range relationships. This segmentation simplifies the overall problem by breaking it into manageable linear sub-problems
2Measurement precision
If more microphones are added to improve location accuracy and confidence, then measurement precision improves, but run time increases due to solving more complex equations
Solution Approach 1:
By changing the measurement parameter from time difference to range difference, the patent enables the use of linear equations that can be solved efficiently. This allows accurate location determination with only three microphones, avoiding the need to add more microphones which would increase computational time and system complexity
3Reliability
If hyperbolic positioning methods are used to achieve high confidence in location results, then reliability improves, but device complexity increases due to multiple solution approaches needed for different microphone configurations
Solution Approach 1:
The patent develops a universal location determination method based on range difference measurements that works consistently regardless of the specific geometric configuration of microphones. The linear equation approach provides a unified solution framework that handles different microphone arrangements (collinear, triangular, tetrahedral) through the same mathematical principles, eliminating the need for multiple specialized algorithms and reducing coding complexity
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
This method delivers high accuracy, high confidence, and fast answer determination for device location, capable of achieving results in tens of milliseconds with negligible additional error, and can be scaled efficiently using binary search algorithms.
Implementation Method 1
The ultrasonic emitter can transmit ultrasonic energy in a short burst which can be received by an ultrasonic transducer (microphone) in the ultrasonic receiver
Implementation Method 2
hyperbolic positioning is required when only time difference of arrival (TDOA) information for signals is available
Data Source
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AI summary
A method and system for ultrasonic locationing using time difference of arrival measurements includes an ultrasonic receiver including three microphones (116) each disposed on a periphery of a housing and a fourth centrally-positioned microphone (216). A controller establishes only time difference of arrival measurements of an ultrasonic signal at each microphone, assumes an arbitrary flight time for the signal in order to obtain three flight distances (Rl, R2, R3) of the signal at each of the three microphones, calculates an intersection point (206) of three spheres having radii equal to the three flight distances, calculates a distance from the intersection point to the central microphone, subtracts the distance from a sum of the arbitrary flight time plus the time difference of arrival measurement for the central microphone to establish an test error, and searches different arbitrary flight times along a straight line (200) through the central microphone and intersection point until the test error is less than a threshold, indicating an actual location (106) of the emitter.