Low-Power Tilt-Compensated Pointing Device With Roll-Compensated Gyroscope
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Solution Overview
Problem
Existing pointing algorithms in smart pens and similar devices face challenges in achieving low power consumption, tilt compensation, and efficient resource utilization while maintaining accuracy and reliability, particularly due to the limitations of gyroscope-only solutions and complex sensor-fusion algorithms.
Innovation Solution
A pointing method utilizing a MEMS triaxial accelerometer and gyroscope with a generic sensor-fusion algorithm to generate a gravity vector, combined with a roll-compensated gyroscope signal, allows for tilt-compensated pointing with low-power consumption by processing in a few easy operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a gyroscope-only solution is used for pointing, then power consumption is low and the algorithm is lightweight, but tilt compensation is not achieved and the user must maintain fixed device orientation
Solution Approach 1:
The patent combines gyroscope measurements with accelerometer-derived gravity vector information to achieve tilt compensation. The gyroscope provides angular rate data while the accelerometer provides gravity direction, and their fusion enables accurate pointing without requiring fixed device orientation, thus merging the advantages of both sensors.
Solution Approach 2:
The gravity vector from the accelerometer serves multiple purposes: it enables tilt compensation for the gyroscope measurements and provides a reference frame for remapping angular rates to screen coordinates. This multi-functional use of the gravity vector allows tilt compensation without requiring complex dedicated algorithms.
2Ease of operation
If dedicated sensor-fusion algorithms with Kalman filters are used, then tilt compensation is achieved, but computing power and power consumption increase significantly
Solution Approach 1:
The patent extracts only the essential component needed for tilt compensation - the gravity vector from the accelerometer - and uses it directly to compensate the gyroscope measurements. This extraction approach avoids the computational overhead of full sensor-fusion algorithms like Kalman filters while achieving the necessary tilt compensation.
Solution Approach 2:
The patent uses simple mathematical operations (cross products and coordinate transformations) instead of complex filtering algorithms. These computationally inexpensive operations provide adequate tilt compensation for the application, sacrificing some algorithmic sophistication for significantly reduced power consumption and computational requirements.
3Measurement precision
If complex filters and ad-hoc algorithms are implemented, then tilt compensation accuracy improves, but memory occupation and device complexity increase
Solution Approach 1:
The patent segments the pointing algorithm into distinct functional steps: obtaining gravity vector from accelerometer, compensating gyroscope measurements using the gravity vector, and remapping to screen coordinates. This segmentation simplifies the overall algorithm structure and reduces implementation complexity while maintaining tilt compensation accuracy.
Data Source
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AI summary
A pointing method to generate screen-frame displacement data based on 3D-space movements of a pointing electronic device (1), envisages: receiving a gravity vector (g), having components (gx, gy, gz) corresponding to respective projections of gravity acceleration (g) on three axes (X, Y, Z) of a 3D reference system associated with the pointing electronic device (1), generated by a sensor-fusion algorithm from joint processing of an acceleration signal (Acc), indicative of acceleration acting on the pointing electronic device (1) along the three axes (X, Y, Z) of the 3D reference system, and of a gyroscope signal (Gyro), indicative of angular rate of rotation of the pointing electronic device (1) around the three axes (X, Y, Z) of the 3D reference system. The method further envisages: implementing a roll-compensation of the gyroscope signal (Gyro) as a function of the gravity vector (g) to determine a roll-compensated gyroscope signal (Gyro'); and generating the screen-frame displacement data based on the roll-compensated gyroscope signal (Gyro').