Intermittent Magnetic Motion Tracking System
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Solution Overview
Problem
Current motion tracking systems require infrastructure and are not ambulatory, suffer from occlusion and magnetic disturbances, and consume excessive power, limiting their use in various applications.
Innovation Solution
A motion tracking system using inertial sensors combined with intermittent magnetic field transmitters, where position and orientation information is derived by periodically calibrating inertial measurements with magnetic data, reducing power consumption and enabling ambulatory use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If continuous magnetic field transmission is used to achieve high time resolution, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The transmitter transmits magnetic fields intermittently at predetermined time intervals rather than continuously. The processor derives position and orientation information during the intervals between transmissions using inertial sensor data, and periodically calibrates this data with magnetic field measurements when transmissions occur. This periodic action reduces power consumption while maintaining measurement precision through calibration.
2Duration of action of moving object
If inertial sensors are used for continuous position measurement, then duration of action is improved, but measurement precision deteriorates due to integration drift
Solution Approach 1:
The system uses magnetic field measurements as feedback to periodically correct and recalibrate the inertial sensor data. When the transmitter emits magnetic fields, the magnetic measuring module captures these fields and the processor uses this information to reset and recalibrate the integrated position and orientation data from the inertial sensors, eliminating accumulation of errors over time.
Solution Approach 2:
The system performs preliminary calibration of inertial sensor data using magnetic field measurements at predetermined intervals before significant drift occurs. This periodic recalibration prepares the system by resetting the integration constants and correcting orientation errors before they accumulate to unacceptable levels.
3Volume of stationary object
If magnetic field strength is increased to improve detection range, then volume of stationary object is improved, but weight of moving object increases
Solution Approach 1:
The transmitter emits magnetic fields periodically at predetermined intervals rather than maintaining continuous high-strength fields. During transmission intervals, the magnetic field strength is high for calibration, but between transmissions the field is reduced or off, allowing use of smaller, lighter transmitter components while achieving the same functional detection range through periodic measurements.
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 system allows for accurate, ambulatory motion tracking with reduced power consumption, minimizing weight and cost, and extending usage time to several hours or a day, while reducing sensitivity to magnetic disturbances.
Implementation Method 1
The magnetic measuring module measures the earth magnetic field which is used as a reference for the forward direction in the horizontal plane (north)
Implementation Method 2
at least one current coil is wound around the trunk for generating a magnetic field, with a magnetic measuring module for measuring the magnetic field
Implementation Method 3
The measured gravitational acceleration can be used as a reference system direction
Data Source
Figure 1A~1C
Figure 2
Figure 3
AI summary
A motion tracking system for tracking an object composed of object parts in a three-dimensional space. The system comprises a number of magnetic field transmitters; a number of field receivers for receiving the magnetic fields of the field transmitters; a number of inertial measurement units for recording a linear acceleration; a number of angular velocity transducers for recording angular velocities. The system further comprises a processor for controlling the transmitters and receiving signals coming from the field receivers and the inertial measurement unit; which processor contains a module for deriving orientation and/or position information of the constituent object parts of the object on the basis of the received signals. The processor is configured for intermittently controlling the transmitters transmit at a predetermined frequency, wherein the position and/or orientation information is derived by periodically calibrating the motion information coming from the inertial measurement unit with the motion information coming from the magnetic field receivers.