HMD Attitude Correction Using Dynamic Angular Rate
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Solution Overview
Problem
Existing techniques for calculating the attitude of a display device, such as head-mounted displays, using angular rate sensors and accelerometers face challenges in accurately correcting for errors in attitude measurement over time, leading to user discomfort due to unsmooth image rendering.
Innovation Solution
A processing method that integrates angular rate data from an angular rate sensor and acceleration data from an accelerometer to calculate a first attitude, which is then corrected using a maximum correction angle based on gravitational acceleration, ensuring smooth image rendering by limiting corrections according to the device's movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If attitude correction is performed continuously using accelerometer data, then measurement precision is improved, but user discomfort increases due to excessive image rendering corrections during device movement
Solution Approach 1:
The patent applies dynamics by making the correction application dynamic rather than static. The system calculates a dynamic correction application ratio based on the current angular rate magnitude, allowing the correction to adapt automatically to the device's motion state. When the device moves quickly (high angular rate), the correction ratio is reduced or suspended. When the device is relatively stationary (low angular rate), the correction ratio increases to improve measurement accuracy. This dynamic adjustment resolves the contradiction by making the correction process responsive to real-time motion conditions.
Solution Approach 2:
The patent changes the parameter of correction application ratio based on the angular rate parameter. By monitoring the angular rate from the angular rate sensor and adjusting the correction application ratio accordingly, the system transforms a fixed correction approach into a variable one. The correction application ratio becomes a function of the angular rate, allowing the system to optimize between measurement precision and user comfort by adjusting this parameter in real-time based on device motion characteristics.
2Measurement precision
If correction application ratio is increased to improve attitude accuracy, then measurement precision is improved, but image rendering smoothness deteriorates during device movement
Solution Approach 1:
The system dynamically adjusts the correction application ratio based on the angular rate magnitude. When angular rate is high (device moving), the correction application ratio is automatically reduced to maintain image rendering smoothness. When angular rate is low (device stationary), the correction application ratio is increased to improve attitude calculation accuracy. This dynamic behavior ensures that the system optimizes the trade-off between precision and smoothness based on real-time motion conditions rather than using a fixed ratio.
Solution Approach 2:
The correction application ratio parameter is changed based on the angular rate parameter. The system establishes a relationship where the correction application ratio is a function of the angular rate, allowing automatic parameter adjustment. This parameter change strategy enables the system to achieve high attitude accuracy when needed (low motion) while maintaining smooth image rendering during motion, effectively resolving the contradiction between these two requirements.
3Speed
If angular rate sensor data is used for attitude calculation, then response speed is improved, but measurement precision deteriorates due to error accumulation over time
Solution Approach 1:
The patent merges the advantages of both the angular rate sensor (fast response) and the accelerometer (accurate long-term measurement). The angular rate sensor provides the primary attitude calculation with fast response, while the accelerometer provides correction data to compensate for error accumulation. By combining these two sensor inputs through the correction application mechanism, the system achieves both the fast response of the angular rate sensor and the long-term accuracy of the accelerometer, resolving the contradiction between response speed and measurement precision.
Solution Approach 2:
The system uses feedback from the accelerometer to correct the attitude calculation derived from the angular rate sensor. The accelerometer data serves as a feedback mechanism that detects error accumulation in the angular rate-based attitude calculation over time. This feedback is then applied through the correction application ratio to compensate for the drift, allowing the system to maintain both fast response (from the angular rate sensor) and long-term accuracy (from the accelerometer feedback).
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 effectively corrects attitude errors, reducing user discomfort by ensuring smooth image rendering, especially during significant device movement, while maintaining accuracy even when the device is static.
Implementation Method 1
calculating a first attitude of the display device based on an angular rate detected by the angular rate sensor
Implementation Method 2
correcting the first attitude to calculate a second attitude, based on an acceleration detected by the accelerometer
Data Source
AI summary
An HMD includes an attitude calculating unit, an attitude correcting unit, an image generating unit, and a display control unit. The attitude calculating unit may calculate a first attitude of the HMD based on an angular rate detected by an angular rate sensor. The attitude correcting unit may correct the first attitude to calculate a second attitude, based on an acceleration detected by an accelerometer and a rotation amount per predetermined time of the HMD. The image generating unit may generate an image according to the second attitude. The display control unit may cause a display to display the image.