Inertial Device Turning Point Velocity Direction Estimation
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Solution Overview
Problem
Conventional inertial devices for pedestrian dead reckoning (PDR) require attachment to the user, are costly due to high performance requirements, and are difficult to downsize, especially when not attached, and they perform high-load calculations using sensors like acceleration and magnetic field sensors.
Innovation Solution
An inertial device with an acceleration sensor that detects turning points in vertical acceleration waveforms to calculate horizontal velocity and determine movement direction without the need for Fourier transformation or principal component analysis, allowing for reduced cost and size while estimating direction accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high performance inertial sensors are used to estimate direction without attachment, then measurement precision is improved, but device cost increases and device size increases
Solution Approach 1:
The patent changes the processing parameters from high-rate sampling to event-triggered sampling based on turning point detection. By detecting turning points in the vertical acceleration waveform and only calculating horizontal velocity during these specific periods, the system achieves accurate direction estimation while reducing computational load and allowing the use of lower-cost sensors.
Solution Approach 2:
The patent applies partial action by performing high-load calculations (Fourier transformation or principal component analysis) only during specific periods centered on turning points rather than continuously. This selective processing reduces the overall computational burden while maintaining estimation accuracy when it matters most.
2Measurement precision
If high performance inertial sensors are used to estimate direction without attachment, then measurement precision is improved, but device size increases
Solution Approach 1:
The patent changes the sampling rate parameter from high-rate continuous sampling to event-triggered sampling based on turning point detection. This parameter change reduces the data processing load and allows for a more compact device design while maintaining accurate direction estimation capability.
Solution Approach 2:
The patent extracts only the essential information needed for direction estimation by detecting turning points and calculating velocity only during relevant periods. This extraction approach eliminates unnecessary data processing requirements, enabling device downsizing while preserving measurement precision.
3Measurement precision
If Fourier transformation or principal component analysis is used for direction estimation, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies partial action by performing complex calculations (Fourier transformation or principal component analysis) only during specific periods centered on detected turning points rather than continuously. This selective application reduces computational complexity while maintaining measurement precision when direction changes occur.
Solution Approach 2:
The patent segments the processing into distinct phases: turning point detection phase, velocity calculation phase centered on turning points, and direction estimation phase. This segmentation allows complex calculations to be performed only when necessary, reducing overall device complexity while preserving accuracy.
Data Source
AI summary
An inertial device having sensors operable to output accelerations in a horizontal and a vertical direction is disclosed that includes a detection unit configured to detect a turning point in a waveform representing the acceleration in the vertical direction with respect to time and to detect time at the turning point; a calculation unit configured to calculate a velocity in the horizontal direction using the acceleration in the horizontal direction in a predetermined period centering on the time at the turning point; a determination unit configured to determine whether the velocity is less than or equal to a threshold value; and an estimation unit configured to estimate a direction to which a target having the inertial device moves using the velocity in response to a determination by the determination unit that the velocity is less than or equal to the threshold value.