Position Tracking System Using Inertial Sensors and RF Signals
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Solution Overview
Problem
Existing RF-based position tracking systems face limitations such as satellite and receiver clock errors, signal propagation errors, and drift, bias, and scale factor errors, particularly in GPS systems and sourceless navigation systems, which affect accuracy and stability, especially in environments with line-of-sight restrictions and multipath issues.
Innovation Solution
Integration of an inertial/magnetic devices subsystem (IMDS) within mobile devices to stabilize RF signals by combining inertial information with RF data using a Kalman filter, allowing for accurate position tracking in two or three dimensions, even during signal corruption or loss, and implementing an automatic power management system to conserve battery life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GPS receivers are used for position tracking, then location data can be obtained, but accuracy deteriorates in environments with line-of-sight restrictions or tall buildings
Solution Approach 1:
The patent combines GPS receiver with inertial sensors (accelerometers, gyroscopes, magnetometers) into an integrated navigation system. The inertial sensors continue tracking position through inertial navigation when GPS signals are blocked or unavailable, ensuring continuous operation and maintaining position accuracy in urban canyons, indoor environments, or areas with line-of-sight restrictions.
Solution Approach 2:
The system dynamically changes operational parameters by switching between GPS-based positioning and inertial navigation based on signal availability. When GPS quality deteriorates or becomes unavailable, the system transitions to inertial navigation mode, adjusting the navigation parameters to maintain accurate position tracking under varying environmental conditions.
2Measurement precision
If GPS systems are used, then position tracking is achieved, but satellite and receiver clock errors introduce measurement biases
Solution Approach 1:
The inertial navigation system serves as an intermediary that provides continuous position tracking independent of GPS clock synchronization. The inertial sensors measure acceleration and integrate it to determine position changes, bypassing the need for satellite-receiver clock synchronization and eliminating the associated timing errors and measurement biases.
3Reliability
If RF signals are used for position tracking, then location data can be obtained, but signal propagation errors and multipath effects reduce accuracy
Solution Approach 1:
The system performs preliminary position updates using inertial navigation before GPS signal degradation occurs. By continuously integrating inertial measurements, the system maintains an accurate position estimate that serves as a baseline, reducing the impact of subsequent signal propagation errors and multipath effects when RF signals are received.
4Measurement precision
If continuous RF transmission is used for position tracking, then accurate location data is maintained, but battery life is reduced
Solution Approach 1:
The system uses periodic GPS signal updates combined with continuous inertial navigation. The inertial sensors continuously track position without requiring periodic signal transmission, while GPS provides periodic corrections to bound inertial drift. This periodic action pattern maintains position accuracy while significantly reducing battery consumption compared to continuous RF transmission.
Data Source
AI summary
An RF position tracking system for wirelessly tracking the three-dimensional position of a tracked object. The tracked object has at least one mobile antenna and at least one inertial sensor. The system uses a plurality of base antennas which communicate with the mobile antenna using radio signals. The tracked object also incorporates the inertial sensor to improve position stability by allowing the system to compare position data from radio signals to data provided by the inertial sensor.