Mobile Body Motion Estimation Using Magnetic Field Validity Checks
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Solution Overview
Problem
Current motion estimation methods for mobile bodies face challenges such as unreliable data from absolute sensors, integration errors from relative sensors, and limitations of existing Kalman filter-based sensor fusion, particularly in environments with magnetic fields, obstacles, and slippery floors, which require non-Gaussian noise handling and precise sensor information.
Innovation Solution
A motion estimation method and system that uses sensor fusion combining magnetic compasses, gyroscopes, and odometers, where magnetic field information is used to determine the validity of compass data and adjust the estimation of moving direction through Kalman filters or integration based on threshold comparisons, allowing for robust orientation estimation in various environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Kalman filter-based sensor fusion is used to combine gyro, compass, and odometer data, then motion estimation accuracy is improved, but the system becomes sensitive to non-Gaussian noise in magnetic fields, obstacles, and slippery floors
Solution Approach 1:
The patent implements dynamic switching between different sensor fusion methods (Kalman filter, complementary filter, and sensor selection) based on real-time environmental conditions detected through validity checks on magnetic field data, gyro data, and odometer data. This allows the system to adapt its estimation strategy to match current operating conditions rather than relying on a single static filter
Solution Approach 2:
The system changes the parameters of sensor fusion by selecting different fusion methods based on environmental validity. When magnetic field validity is high, compass data is incorporated; when validity is low, the system switches to methods that rely more on gyro and odometer data, effectively changing the fusion parameters to match environmental conditions
2Measurement precision
If compass data is used for orientation estimation, then long-term directional accuracy is improved, but the system becomes vulnerable to magnetic field disturbances in indoor environments
Solution Approach 1:
The patent introduces magnetic field validity checks as an intermediary mechanism that mediates between compass data and the orientation estimation process. The validity check acts as a gatekeeper, allowing compass data to influence orientation only when magnetic field conditions are deemed reliable, and blocking it when disturbances are detected
Solution Approach 2:
The system dynamically adjusts the weight and usage of compass data based on real-time validity assessment. When magnetic field validity is high, compass data is heavily weighted for long-term accuracy; when validity is low, the system reduces or eliminates compass usage, switching to gyro-based estimation
3Device complexity
If only relative sensors (gyro and odometer) are used for pose estimation, then the system is simpler and less expensive, but integration errors accumulate over time causing drift
Solution Approach 1:
The patent merges relative sensors (gyro, odometer) with an absolute sensor (compass) in a conditional sensor fusion system. The compass provides absolute directional reference to correct drift, while the relative sensors provide continuous motion data, combining the benefits of both sensor types without requiring all sensors to be active simultaneously
4Measurement precision
If expensive high-specification sensors are used to improve sensor fusion performance, then measurement accuracy is improved, but the system cost and complexity increase
Solution Approach 1:
The patent applies partial action by using standard-specification sensors rather than high-specification sensors, combined with intelligent partial usage of sensor data based on validity checks. The system uses only the portion of sensor data that is currently valid and reliable, rather than relying on continuously high-performance data from expensive sensors
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 approach provides accurate and robust pose estimation for mobile bodies, effectively handling uncertain environments like magnetic fields and slippery floors, without requiring high-specification sensors, thus overcoming limitations of traditional methods.
Implementation Method 1
obtaining compass information from magnetic compasses attached to the mobile body; calculating a magnitude of a magnetic field from the compass information
Implementation Method 2
a method using a gyro, a compass, and an odometer together
Implementation Method 3
a method using only an odometer, a method using a gyro and an odometer
Data Source
AI summary
A motion estimation method and system for a mobile body are provided. The method includes: obtaining magnetic field information from compass information of the mobile body; comparing the magnetic field of the mobile body with a predetermined value and determining whether a position of the mobile body belongs to a specific region according to the comparison result; and estimating a direction of the mobile body by determining whether a compass azimuth angle is used for direction estimation of the mobile body according to the determination result. The system, in which a gyro, odometers, and compasses are installed, comprises: a magnetic field calculator calculating the magnitudes of magnetic fields of the mobile body; a magnetic field comparator obtaining differences between the magnitudes of the magnetic fields and the magnitude of the geomagnetic field and comparing the differences with the first threshold value; a geomagnetic region determiner determining whether a position where the mobile body exists belongs to a region where the geomagnetism works according to the comparison result; and a moving direction estimator estimating a moving direction of the mobile body by determining whether or not to use azimuth angles of the compasses for direction estimation of the mobile body according to the determination result.