IEEE Robotics & Automation Magazine - September 2013 - 30

We used a Delrin core to assemble the metal laminations in
the cylindrical-shaped ending (Figure 10). Epoxy material was
used to create a rigid structure and to provide electronic insulation. The magnetic core received further electric insulation
by means of insulating lacquer. The module was then wound
in copper wire. More than 500 windings were utilized. Weight,
resistance, and dimensions were checked after fabrication.

Figure 8. The final and intermediate shape of the iron wire.

Figure 9. Iron wire modeling. About 200 laminations were
crafted for the entire device. A simple but stable setup was built
to ensure constant dimensions for all the laminations.

Primary Module
The primary unit was developed by following similar design
criteria to those adopted for the secondary side, particularly
with regard to the maximum magnetic induction available in
the material and target voltage. The module is composed of
six radial coils (Figure 11), generating a magnetic ﬂux, and
poles are located with a small radial gap at the ends of the secondary module. Epoxy material was used to link iron pieces
in the six cores. Coils were made by using a wire with a diameter of 0.8 mm, which gives an impedance for the six coils
in series that matches the voltage given by a commercial
transformer, as detailed in the following.
After preliminary tests on overall functionality, the module was embedded in polyurethane (PU) to strengthen the
structure, increase the heat dissipation, and make the system
waterproof. The device will also be coated with a special lacquer paint to obtain a smooth surface and to ensure complete
isolation when underwater.
Experiments
Once the ﬁnal prototype was ready (Figure 12), experiments were performed to verify compliance with the
model and to characterize the device. Particular attention
was paid to the testing of the output power supplied by
the secondary coil. Table 2 summarizes the main characteristics of the system.
The complete device is powered by an external workstation and works at 48 V and 50 Hz. The most important value
to investigate is the maximum output power of the second-

Materials and Methods
Secondary Module
As already mentioned, the secondary coil dimensions are
approximately 50 mm in diameter and 60 mm !2 mm in
length. Off-the-shelf materials were chosen as building elements.
Materials:
● iron wire (1.2 mm diameter)
● Delrin
● copper wire (0.5 mm diameter)
● epoxy material.
The iron wire was shaped into curved laminations (Figures 8
and 9) in accordance with the transformer theory. In fact,
using a low-frequency magnetic ﬁeld (50 Hz), hysteresis
losses and eddy currents can inﬂuence the device by generating side effects in the magnetic core. To reduce these effects,
which may decrease the efﬁciency of the device, the magnetic
core needs to be built with lamination-like elements.
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IEEE ROBOTICS & AUTOMATION MAGAZINE

september 2013

Figure 10. The secondary coil is mounted using the laminations,
and a Delrin core is used as a building frame for the metal. First,
the metal is bound in a solid structure using Epoxy material and
then wound in copper wire.

Table of Contents for the Digital Edition of IEEE Robotics & Automation Magazine - September 2013