IEEE Robotics & Automation Magazine - December 2018 - 74

Position (m)
Orientation (°)
Angle (°)

2
1.5
1
0.5
0
-0.5
-1
20
15
10
5
0
-5
5
0
-5
-10
-15
-20
-25
-30

a
Roll

Pitch

Yaw

|φ |
0

75
Time (s)

105

120

135

150

Figure 10. The top and middle rows demonstrate the position and orientation of the OTHex AM. The bottom row shows the
evolution of the OTHex passive joint angle during a typical task with free flight, horizontal motion, and object tilting. The four instants
highlighted are (a) takeoff, (b) the OTHex grasping, (c) cooperative lifting, and (d) ungrasping. The blue area highlights the horizontal
motion, and the green area shows the bar tilting.

by the object's weight ( xy ) diminishes during the lifting of
the object, because it is proportional to the cosine of the
object inclination. Figure 9 (bottom row) depicts the joint
torque of the GM: it is clear that joint torques start to be
noisy when the breaks are disengaged (≈30 s). Given the
particular configuration of the GM, most efforts are furnished by the joint A2 (shoulder), and the three joints not
aligned with the motion (A1, A3, and A5) are not solicited.
All joint torques are well within their limits (Table 1). The
AM-desired trajectory from the admittance filter is presented in Figure 10; the good tracking performances validate
our approach. Indeed, thanks to the multidirectional thrust,
the error in orientation does not impact the position during
the cooperative manipulation.
Conclusions and Future Work
We introduced the Tele-MAGMaS, a new kind of heterogeneous multirobot system with teleoperation capability. This
new category of systems leverages the advantages of both
GMs and AMs to perform tasks that would be impossible
for homogeneous systems. A scenario of object manipulation (pose tracking), beyond the working capabilities a single robot could achieve, is enabled through the teleoperation
of the MAGMaS. To demonstrate the benefit of AMs, we
designed the OTHex, a fully actuated platform tailored for
bar lifting. The integration and implementation of the
framework have been demonstrated in a set of experiments
(including a week of live demonstrations during the
Hanover Fair 2017), thus proving the reliability of our
approach. Moreover, the software architecture is component-based; hence, adding a higher-level task planner or
other perception modules to operate outdoors could be easily achieved.
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IEEE ROBOTICS & AUTOMATION MAGAZINE

december 2018

Aside from the advantages provided by its architecture,
the Tele-MAGMaS opens a new field of study that may eventually bring improvements to the method presented here. In
particular, although the idea of the Tele-MAGMaS is generic,
further work is necessary to reach the point where three arbitrary robotic components can be strapped together as a viable Tele-MAGMaS for ad hoc cooperative manipulation.
Currently, the system relies on motion-capture information
for its localization and general state estimation: our goal is
to replace the motion-capture system with a truly embedded perception to run experiments in any environment,
especially outdoors. Our future work will also include the
extension of the system and framework to a GM mounted on
a mobile platform, which is of paramount importance in
USAR or construction missions. It is also important to
address the estimation of load parameters and the active
rejection of vibrations in the system. Another envisioned
plan to improve the work is to make the teleoperation and
shared-control schemes more robust against time delay, thus
allowing a system usable in Internet-based teleoperation scenarios where considerable time delays can occur during
Internet traffic jams.
Acknowledgments
This work was partially supported by EU Horizon 2020 grant
644271 AEROARMS; ANR Project ANR-17-CE33-0007
MuRoPhen; EU FP7/2007-2013 grant 601165 WEARHAP;
and the Basic Science Research Program (grant
2015R1A2A1A15055616) of the National Research Foundation funded by the Ministry of Science and ICT, Korea. We
thank KUKA and its Innovation Department, Schunk
France, and MathWorks for support in this research project. The contributions of other collaborators, who helped

IEEE Robotics & Automation Magazine - December 2018

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