A Multi-Node Magnetic Positioning System with a Distributed Data Acquisition Architecture

Abstract

We present a short-range magnetic positioning system that can track in real-time both the position and attitude (i.e., the orientation of the principal axes of an object in space) of up to six moving nodes. Moving nodes are small solenoids coupled with a capacitor (resonant circuit) and supplied with an oscillating voltage. Active moving nodes are detected by measuring the voltage that they induce on a three-dimensional matrix of passive coils. Data on each receiving coil are acquired simultaneously by a distributed data-acquisition architecture. Then, they are sent to a computer that calculates the position and attitude of each moving node. The entire process is run in real-time: the system can perform 62 position and attitude measurements per second when tracking six nodes simultaneously and up to 124 measurements per second when tracking one node only. Different active nodes are identified using a frequency-division multiple access technique. The position and angular resolution of the system have been experimentally estimated by tracking active nodes along a reference trajectory traced by a robotic arm. The factors limiting the viability of upscaling the system with more than six active nodes are discussed.

Parkinson’s Disease Patient Monitoring: A Real-Time Tracking and Tremor Detection System Based on Magnetic Measurements

“…This study extends the results in [ 19 ], where the feasibility of adopting the magnetic tracking system for tremor monitoring was investigated by preliminary experiments, and it adopts a hardware setup which was entirely developed by our research group and presented in [ 16 ]. Extensive measurement results are provided on trajectories that emulate tests for movement tremor, rest tremor and tapping.…”

“…The MPS prototype used [ 16 ] was an enhanced version of that presented in [ 32 ], which was also previously adopted for industrial purposes in [ 33 ], and equipped with novel capabilities for reducing EMC disturbances in [ 17 ]. The system tracked the position and attitude of an active coil (TX) moving within a matrix of passive coils acting as receivers (RXs).…”

“…The main features of the MPS—mean Euclidean error , mean angular error , measurement rate, mean signal-to-noise ratio and TX operating frequencies—as reported in [ 16 ], are summarized in Table 1 . We performed experiments using a robotic arm as a reference.…”

“…To overcome these limits, the authors of this paper propose the adoption of a scalable and transportable tracking and monitoring system. The solution presented in this work can be used to detect vibration patterns and trajectories compatible with those associated with PD symptoms and diagnostic tests, as well as for other localization and rehabilitation purposes, such as in [ 16 , 17 , 18 ]. The system measures vibrations from direct position measurements instead of integrating inertial data, avoiding error accumulation.…”

MagIK: a Hand Tracking Magnetic Positioning System based on a Kinematic Model of the Hand

“…The MPS error on position ϵ r is defined as the Euclidean distance between measured and real positions. By choosing a reference set of positions, an empirical distribution for ϵ r is obtained, as reported in [39]. Taking the average and the standard deviation of this distribution, the Euclidean error of the MPS can be estimated asε r = 3.5 ± 1.9 mm.…”