Instrumentation & Measurement Magazine 25-6 - 4

Use of Magnetic Positioning
Systems in Industrial and
Biomedical Applications
Andrea Bernieri, Gianni Cerro, Luigi Ferrigno, Marco Laracca, and Filippo Milano
N
owadays the ability to locate people and objects is
becoming an important and necessary aspect for
the wide range of applications concerning localization-based
services. Indeed, applications based on spatial and
time awareness of people and objects within certain contexts
are being developed. Some application examples in which the
positioning problem must be considered and solved are: industrial
automation, virtual reality, smart cities, smart health,
robot navigation and remote surgery. Although in outdoor environments
this does not represent a big issue thanks to the
presence and support of Global Navigation Satellite Systems
(GNSSs), there is a whole series of scenarios, such as indoors,
underground, and underwater environments, in which GNSSs
fail due to the complexity of the considered environments with
respect to radio propagation. Nowadays, in the considered
scenarios, the identification of a reliable method able to satisfy
the positioning requirements is an open issue, for which the
measurement community can provide a valuable contribution
regarding the proposal of measurement methods and procedures,
the evaluation of the major causes of uncertainty of the
devices and the consideration of these features within positioning
algorithms and data processing.
Approaches to Positioning
Measurement
The process by which a generic mobile node is able to dynamically
orient itself in an unknown environment is known as
positioning [1]. Once the information regarding the position
and orientation of the mobile node has been determined, it is
also necessary to provide information on the surrounding environment
to allow navigation of the mobile node within the
environment. The mobile node can be a device such as a smartphone,
and thus the location information can be exploited by
the person using the device, or it can be a sensor in a wireless
sensor network, and its position is crucial to correlate its data
to the geographical place where it is located [2]. Furthermore,
in industrial logistics applications, it is necessary to track the
product's position in real time, so the mobile node represents
the generic product to be tracked. A robot (mobile node) needs
4
to know its position and orientation to navigate within a work
environment. A surgeon who performs a remote-controlled
surgical intervention needs to know the scalpel position to be
sure that its operation is accurately performed. These are some
of the many applications in which the services of people but
also the actions of objects depend on the position taken within
a work environment.
There are two main adopted approaches to solve the positioning
problem. There are so-called anchor-based systems
[3], in which there are reference devices (therefore with known
position and orientation) which are used to exchange information
with the mobile node. The reference devices are typically
known as " anchors " while the mobile node is known as the
" tag. " A GNSS is an example of an anchor-based positioning
system. Through the exchange of anchors-tag information, it is
possible to estimate some quantities (for example, the anchorstag
distances) which act as inputs, together with the positions
and orientations of the anchors, for the positioning procedure.
The position and the orientation of the tag are the output of this
procedure. All of the coordinates of the anchors (known) and
of the tag (estimated), are determined with respect to an absolute
reference system.
Another adopted approach to solve the positioning problem
is based on anchor-free systems [4]. These systems do
not require the use of anchors, but through the estimation of
quantities related to the inertia of the device (velocity and acceleration)
and subsequent integration processes, the tag is
able to self-locate. An Inertial Measurement Unit represents
the most common example of an anchor-free positioning system.
In these systems, the position and orientation of the tag
are referred to a local reference system located on the tag, since
it is not necessary to define an absolute frame.
From a constructive point of view, anchor-free systems offer
advantages regarding the cost and ease of set-up (since
there are no anchors, both the cost and the installation of such
devices are missing) compared to anchor-based systems.
On the other hand, anchor-based systems have the advantage
of excellent stability over time of the estimated solution,
while for anchor-free systems, due to measurement noise and
IEEE Instrumentation & Measurement Magazine
1094-6969/22/$25.00©2022IEEE
September 2022
Instrumentation & Measurement Magazine 25-6

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