Cordless Inertial Navigation Elevation Database Integration
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Solution Overview
Problem
Existing cordless inertial navigation systems for land vehicles face errors due to invalid no-roll assumptions, unreliable altitude measurements, and variations in the longitudinal accelerometer arm caused by sideslip, leading to positioning inaccuracies.
Innovation Solution
Incorporating an elevation database to provide accurate vertical position measurements for a Kalman filter, which reduces errors by using rate gyroscopes to track orientation and combining with GNSS, accelerometer, and elevation data to improve rotation and acceleration measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If barometric altimeter measurements are used for vertical position, then cordless navigation is enabled, but altitude measurements become unreliable due to pressure changes in the vehicle cabin
Solution Approach 1:
The patent introduces an intermediary mechanism (pressure equalization system with vents or channels) that allows the vehicle cabin to equalize pressure with the external environment, thereby eliminating the harmful effect of pressure changes on barometric altimeter measurements while maintaining the ability to operate cordlessly
2Device complexity
If the no-roll assumption is made to simplify navigation calculations, then device complexity is reduced, but positioning errors increase due to actual roll motion in vehicles
Solution Approach 1:
The patent extracts and separately handles the roll motion component by introducing roll rate sensing and dedicated roll compensation calculations, removing the unrealistic no-roll assumption while maintaining tractable navigation mathematics through targeted correction terms
3Ease of operation
If longitudinal accelerometer arm is assumed constant, then calculation simplicity is maintained, but positioning errors occur due to sideslip-induced variations
Solution Approach 1:
The patent implements feedback by using lateral acceleration and roll rate measurements to dynamically estimate and compensate for accelerometer arm variations due to sideslip, thereby maintaining calculation simplicity while correcting for the harmful effect of arm length changes
4Device complexity
If roll rates and lateral acceleration are ignored to simplify the navigation system, then device complexity is reduced, but attitude errors accumulate leading to positioning inaccuracies
Solution Approach 1:
The patent applies partial action by selectively incorporating only the critical motion components (roll rates and lateral acceleration) that have the greatest impact on attitude accuracy, rather than implementing a complete six-degree-of-freedom inertial system, thus achieving improved reliability with moderate increases in 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
The solution significantly reduces positioning errors by limiting attitude errors and providing accurate elevation data, enhancing the reliability of inertial navigation systems, especially in situations where GNSS signals are weak or obstructed.
Implementation Method 1
uses rate gyroscopes to track orientation
Implementation Method 2
self-contained barometric altimeter measurements
Data Source
AI summary
Elevation data obtained from a terrain database is a measurement in an inertial navigation system for land vehicles.