Hand Position Modeling Using Minimal Sensors
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Solution Overview
Problem
Existing hand tracking systems require a large number of sensors to model the position and orientation of finger joints, which is cumbersome and inefficient, and do not provide accurate 3D position information.
Innovation Solution
A method and system using at least one sensor on a finger phalanx for five degrees of freedom and a second sensor on the palm for six degrees of freedom, with magnetic induction to detect positions and orientations of the joints, allowing calculation of joint positions and orientations using measured distances and sensor data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sensors are attached to each finger joint to track position and orientation, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system divides the sensing function into two segments: a first sensor on the distal phalanx handling finger tip position and orientation, and a second sensor on the palm/dorsum handling wrist position and orientation. This segmentation allows each sensor to focus on specific degrees of freedom, reducing the total number of sensors needed while maintaining measurement precision for all hand joints.
Solution Approach 2:
The second sensor placed on the palm or dorsum serves multiple functions simultaneously: it tracks wrist position and orientation, and provides reference data for calculating metacarpal-phalangeal joint positions. This multi-functionality reduces the need for separate sensors at each joint, simplifying the overall device while maintaining measurement accuracy.
2Measurement precision
If sensors are placed under and above each joint to measure angles, then measurement precision is improved, but device complexity and ease of operation worsen
Solution Approach 1:
The invention extracts the angle measurement function from multiple distributed sensors and consolidates it into orientation detection by fewer sensors. The first sensor on the distal phalanx and second sensor on the palm detect orientations, from which all joint angles are calculated mathematically, eliminating the need for physical sensors under and above each joint.
Solution Approach 2:
The system replaces the mechanical approach of placing physical sensors at each joint with a computational approach. By detecting the position and orientation of two sensors and knowing the anatomical distances between joints, the system calculates all joint positions and orientations through mathematical relationships, substituting mechanical sensor placement with computational geometry.
3Ease of operation
If a glove with flex sensors is used to measure hand kinematics, then ease of operation is improved, but measurement precision for 3D position deteriorates
Solution Approach 1:
The invention replaces mechanical flex sensors that only measure bending angles with electromagnetic or optical sensors that directly measure 3D position and orientation in space. This substitution provides complete 3D position information while maintaining ease of operation, as the sensors can be integrated into a glove structure similar to flex 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
Enables accurate modeling of hand positions and orientations with a minimal number of sensors, reducing complexity and improving 3D tracking accuracy without additional sensors for metacarpal-phalangeal, proximal interphalangeal, and distal interphalangeal joints.
Implementation Method 1
A varying magnetic field is generated so that the first and second sensors induce voltages, so that at the detection step the position and orientation of each of the first and second sensors is detected based on the induced voltages.
Data Source
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AI summary
The present invention provides a method for modelling a position and orientation of a hand with as small a number of sensors as possible. A first sensor is attached on a phalanx distalis of a finger. The first sensor is adapted to provide information on at least five degrees of freedom that correspond to three translations, yaw and pitch. A second sensor is placed at a fixed position relative to a dorsum or palm of the hand. The second sensor is adapted to provide information on at least six degrees of freedom that correspond to three translations, yaw, pitch and roll with respect to a point of the dorsum or palm of the hand. A position and orientation of each of the first and second sensors is detected. A first distance between said point and a metacarpal-phalangeal joint of the finger, a second distance between the metacarpal-phalangeal joint and a proximal interphalangeal joint, a third distance between the proximal interphalangeal joint and a distal interphalangeal joint, and a fourth distance between the distal interphalangeal joint and the first sensor are measured. A position and orientation of each of the three joints is calculated on the basis of the measured first to fourth distances, the detected position and orientation of the first sensor, and the detected position and orientation of the second sensor.