Direction Detector True North Accuracy via Sensor Rotation
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Solution Overview
Problem
Conventional direction detectors, such as single-axis gyro compasses, face challenges in accurately detecting true north due to errors associated with the time constant of angular velocity sensors, which affect the measurement accuracy and cannot correctly determine true north.
Innovation Solution
A direction detector incorporating an angular velocity sensor, an attitude changer, and a control device that rotates the sensor to match the characteristics of errors associated with the time constant in both measuring and opposite directions, allowing for improved detection accuracy by canceling these errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-axis type gyro compass is used to reduce size and cost, then the device becomes more compact and affordable, but the measurement accuracy deteriorates due to inferior direction measuring accuracies compared to three-axis type compasses
Solution Approach 1:
The patent divides the measurement process into discrete directional steps (0°, 45°, 90°, 135°, 180°, 225°, 270°, 315°) rather than continuous measurement. By segmenting the circular measurement space into specific angular positions, the system achieves sufficient accuracy for civil engineering applications while using a simpler single-axis structure.
Solution Approach 2:
The patent performs preliminary calibration by measuring angular velocities at multiple predetermined directions before calculating the final azimuth angle. This preliminary measurement of angular velocities in different orientations allows the system to compensate for sensor biases and achieve accurate true north detection despite the simplified single-axis structure.
2Measurement precision
If the angular velocity sensor measures rotational angular velocity to determine true north, then true north can be detected correctly, but errors associated with the time constant of the sensor cannot be removed, reducing measurement accuracy
Solution Approach 1:
The patent uses feedback by measuring angular velocities at multiple predetermined directions and using these measurements to calculate the azimuth angle. The system continuously references the measured angular velocities against the known geometric relationships between directions to compensate for time constant errors and sensor biases, thereby improving reliability while maintaining precision.
Solution Approach 2:
The patent changes the measurement parameters by measuring angular velocities at multiple different orientations (0°, 45°, 90°, etc.) rather than at a single position. By varying the measurement parameters across different angular positions, the system can mathematically eliminate the effect of time constant errors through the relationship between measurements at different orientations.
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 enhances the detection accuracy for true north by effectively canceling errors related to the time constant, reducing measurement time and improving the overall precision of the direction detection.
Implementation Method 1
an angular velocity sensor that detects an angular velocity around a y-axis
Implementation Method 2
an acceleration sensor that detects a gravitational acceleration around the y-axis
Data Source
AI summary
A direction detector that allows true north detection accuracy to be improved is provided. In a direction detector 1, an attitude changer 100 rotates an angular velocity sensor 26 around a detection axis and controls an attitude of the angular velocity sensor 26 so that the detection axis is directed in a predetermined measuring direction and an opposite direction to the predetermined measuring direction. A control device 30 controls the attitude changer 100 so that the angular velocity sensor 26 rotates in a first rotation direction around the detection axis before the angular velocity sensor 26 starts to detect an angular velocity around the predetermined measuring direction. The control device 30 controls the attitude changer 100 so that the angular velocity sensor 26 rotates in a second rotation direction opposite to the first rotation direction around the detection axis and, thereafter, the angular velocity sensor 26 rotates in the first rotation direction around the detection axis before the angular velocity sensor 26 starts to detect an angular velocity around the opposite direction.