Inertial Dead-Reckoning Using Context Detection
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Solution Overview
Problem
Current outdoor portable navigation systems are unreliable and power-intensive for indoor navigation due to the limited penetration of GPS and RF signals, and they assume a fixed device orientation, which is impractical for hand-held devices.
Innovation Solution
A low-cost inertial dead-reckoning navigation system using MEMS devices such as accelerometers, gyroscopes, and magnetometers to determine a user's bearing by measuring physical and magnetic orientations at different times, allowing for accurate navigation without the need for external signals and with reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GPS and RF signals are used for navigation, then outdoor navigation is possible, but indoor navigation reliability deteriorates due to signal penetration issues
Solution Approach 1:
The patent replaces the electromagnetic signal-based navigation system (GPS/RF) with an inertial measurement system using accelerometers and magnetometers. This substitution eliminates the dependency on external signals that cannot penetrate buildings, enabling reliable indoor navigation through local physical measurements of motion and magnetic field orientation.
Solution Approach 2:
The patent introduces an intermediary processing layer that combines accelerometer data (for motion detection) and magnetometer data (for heading detection) to compute navigation information. This intermediary system bridges the gap between the unavailable external signals and the required navigation functionality, enabling operation in signal-denied environments.
2Measurement precision
If GPS and RF signals are used for navigation, then positional data is provided, but power consumption increases due to power-intensive receivers
Solution Approach 1:
The patent replaces the power-intensive GPS/RF receivers with low-power MEMS sensors (accelerometers and magnetometers). These inexpensive sensors consume minimal power compared to signal receivers, enabling prolonged navigation operation without requiring continuous high-power external signal acquisition, thus resolving the contradiction between measurement precision and energy consumption.
3Measurement precision
If magnetic heading is used for navigation, then heading information is obtained, but the system becomes unreliable when device orientation changes during use
Solution Approach 1:
The patent implements a dynamic orientation detection system that continuously monitors both magnetic heading and accelerometer data to detect changes in device orientation relative to the user. The system dynamically adjusts the navigation calculations based on the detected orientation state, allowing accurate heading determination regardless of whether the device is held in a fixed position or moved throughout the environment.
Solution Approach 2:
The patent merges the magnetic heading measurement with accelerometer-based motion detection and orientation tracking. By combining these complementary measurements, the system achieves robust heading accuracy that remains valid even when the device is moved or repositioned, as the accelerometer data compensates for orientation changes while the magnetometer provides continuous magnetic north reference.
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
Enables accurate indoor navigation with low power consumption, allowing the device to function effectively even when held in various orientations, such as in a pocket or purse, without relying on external signals like GPS or RF.
Implementation Method 1
determining with a physical sensor of the portable device, a first geometric orientation of the portable device with respect to gravity
Implementation Method 2
determining with a magnetic sensor of the portable device, a first sensed magnetic field of the portable device in response to an external magnetic field
Implementation Method 3
MEMS devices may include a three-axis accelerometer, three-axis gyroscope
Data Source
AI summary
A method for determining a user bearing, implemented on a portable device programmed to perform the method includes determining with a physical sensor of the portable device, a first geometric orientation of the portable device with respect to gravity at a first time, determining with a magnetic sensor of the portable device, a first sensed magnetic field of the portable device in response to an external magnetic field at the first time, determining with the magnetic sensor of the portable device, a second sensed magnetic field of the portable device in response to the external magnetic field at the second time, and determining with the portable device a bearing of the portable device at the second time in response to the first geometric orientation, the first sensed magnetic field, and the second sensed magnetic field.