IEEE Robotics & Automation Magazine - December 2018 - 16

single- and dual-arm aerial manipulators. The approach in
[22] is based on an extension of the set-based null-space-
based approach [23] to the case of aerial manipulators, which
involves challenges different from those in other robotic sys-
tems. On the one hand, the results show that this generaliza-
tion was successful; on the other, specific behaviors and
design procedures were tailored because of the different actu-
ating characteristics.
Teleoperation
To evaluate the feasibility of aerial telemanipulation for indus-
trial I&M tasks, the AEROARMS teleoperation system had
the goals of ensuring 1) a stable and transparent teleoperation
system under the channel characteristics of the wireless com-
munication link and 2) the stability of the coupled controller
for the manipulator and aerial base.

and position signals were exchanged between both the haptic
interface (master) and the aerial robot (slave). In each of the
channels, a passivity-based controller was exploited to guar-
antee stability under nominal communication time delays,
packet loss, and jitter, while transparency was maintained. To
this end, a widely used passivity tool, namely, the time-
domain passivity approach (TDPA), was used. The overview
of the implemented bilateral controller for the AEROARMS
project is shown in Figure 4.

(°)

(m)

(N)

(m)

Stable Coupled Control of the
Manipulator-Aerial Base System
The stability of the coupled controller for a helicopter with a
manipulator was proven in [24] for the autonomous scenario.
Here, the manipulator wrench forces were computed in the
fuselage frame of the helicopter, thus ensuring passivity. As an
extension of the teleoperation case, the passivity check with
Stable Teleoperation with
TDPA to remove the destabilizing effects of communication
Communication Time Delay
time delay was applied for the coupled controller. The on-
For the time-delayed teleoperation system, the tradeoffs ground hardware-in-the-loop (HIL) simulator [25] was
between stability and performance requirements were tackled adapted to reproduce the dynamics and control of the aerial
by means of a novel four-channel architecture in which force system and repeatedly test the bilateral control under
defined conditions.
Figure 5 shows the results of the
teleoperation peg-in-hole experiments
performed on the HIL with the heli-
4
0.05
copter control and dynamic simulation.
x
y z
Measured Estimated
2
Although the designed controller pro-
0
0
duced a stable and high-performing
-2
-0.05
system (in terms of pure teleoperation),
-4
as can be seen, the base of the manipu-
-0.1
lator moved as a result of the manipula-
0
10
20
30
40 45
0
10
20
30
40 45
tor's motion and external interaction. It
Time (s)
Time (s)
was discovered that, for highly intricate
(a)
(b)
tasks like precise end-effector position-
Roll Pitch Yaw
ing and accurate force exertion on the
x
y z
0.04
0.4
environment, the reactive dynamics of
the aerial base make the task comple-
0
0
tion highly challenging for the operator
(note especially the time between 27
-0.04
-0.4
and 30 s in the plots). To aid the opera-
0
10
20
30
40 45
0
10
20
30
40 45
tor, task-dependent autonomy can offer
Time (s)
Time (s)
substantial benefits. Therefore, employ-
(c)
(d)
ing virtual fixtures [26] and vision-
based shared control [27] rather than
Figure 3. Some experimental results on interaction control: (a) contact force acting on
pure teleoperation is planned in the
the end effector, (b) admittance error, (c) position tracking error, and (d) orientation
tracking error.
AEROARMS scope.

Master Device

Master
Control with
Passivity
Check

Wireless
Communication
with Delay

Figure 4. The teleoperation architecture for the aerial scenario.

16

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IEEE ROBOTICS & AUTOMATION MAGAZINE

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december 2018

Slave
Control with
Passivity
Check

Slave Robot
IEEE Robotics & Automation Magazine - December 2018

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