IEEE Robotics & Automation Magazine - December 2018 - 72

real-time constraint imposed by the human-in-the-loop control scheme. The compromise we chose is a multirigid-body
dynamics integration with
collision-processing and
reconfigurable joints. The
The first experiments
physics simulation is
handled by the V-REP
of the Tele-MAGMaS were
software (http://www
.coppeliarobotics.com/), a
showcased at the
robot simulator that provides a design environHanover Fair 2017.
ment and incorporates the
simulation library Bullet.
Because the overall system
controller relies on MATLAB-Simulink, a bridge enabling
bilateral communication between V-REP and the controller
has been implemented, exploiting the remote application programming interface functions, which are integrated within
S-functions in MATLAB-Simulink, thus providing data
transceiver blocks.

Figure 6. A display of the three-dimensional scene and
graphical user interface within the V-REP. The red box shows the
subsystem status indicators (which can be folded), the blue box
shows the emulated first-person view camera on the OTHex, and
the green box shows the visualization of the interaction forces
and torques.

Figure 7. A photo of the cooperative manipulation state of
the Tele-MAGMaS using the bilateral teleoperation approach
performed during the KUKA 2017 Innovation award competition,
at the Hanover Fair 2017.

IEEE ROBOTICS & AUTOMATION MAGAZINE

december 2018

Additionally, a graphical user interface was implemented
to provide some telemetry to the operator, both in simulations and during real experiments. The displayed information
provides visual feedback (via an emulated camera mounted
on the OTHex), the interaction wrenches, and general metadata about the subsystems state. Considering the large
amounts of possible data to be shown, we have chosen to set
up a hierarchical user interface, which allows the user to
choose the level of detail. The operator is informed about the
status of the system and subsystems by means of color-changing indicators. Each detailed subwindow can be folded to
reduce the visual load on the screen (Figure 6).
Experiments
The first experiments of the Tele-MAGMaS were showcased
at the Hanover Fair 2017 as part of the finals of the KUKA
2017 Innovation Award (Figure 7). The demonstration presented the main features of the Tele-MAGMaS system and a
proof-of-concept application. During the fair week, the demonstration ran every hour (or more often), thus indicating the
high reliability of the proposed system and control architecture. Videos highlighting the key features of the demonstration, i.e., cooperative aerial-ground manipulation with human
telepresence, can be found online at https://vimeo.com/
217252361 and https://youtu.be/GRnGSvJGUKk.
Later, we conducted a set of experiments with a successful comanipulation of a 2.5-m-long bar. The goal is to validate cooperative manipulation with a Tele-MAGMaS for
both horizontal displacements of the object and for lifting.
These basic motions are considered representative of the
possible construction/decommissioning scenario. Additionally, the telepresence framework is validated for teleoperation and full autonomy.
The experimental sequence depicted in Figure 8 consists
in the following tasks. First the OTHex is manually flown to
grasp the bar from one of its ends, while the ground robot
autonomously grasps the other end. Once both manipulators are attached to the bar, the comanipulation is fully
autonomous: they lift the bar from its supports, move it
twice along a line in the horizontal plane (blue part), and
synchronously lift the bar up to 30° (green part). Then, they
bring the bar back to its starting position. This experiment
highlights both the vibration stabilization induced by the
OTHex and the feasibility of the MAGMaS. We realized that
the OTHex was subject to larger external forces than expected, i.e., predicted by the model, due to vibrations of the long
object. This is also illustrated in the video contained in the
multimedia material.
Key quantities of the system are displayed in Figures 9 and
10. In particular, Figure 10 illustrates that a passive joint is sufficient to complete the task, because the bar motion is guided
by the GM. Note that the small oscillation would have
required some active suppression with an actuated joint, leading to a more external wrench on the AM side. This implies
that the passive joint has a stabilizing effect on the system. In
Figure 9, the Cartesian wrench at the GM EE is depicted (top

http://www.coppeliarobotics.com/ http://www.coppeliarobotics.com/ https://www.vimeo.com/ https://youtu.be/GRnGSvJGUKk

IEEE Robotics & Automation Magazine - December 2018

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