IEEE Robotics & Automation Magazine - December 2018 - 20

task-constrained motion-planning problems and generally
reduces the dimensionality of the search space. Finally, by
properly defining the task, one can choose a good tradeoff
between the dimension of the search space and the delegation
of some degrees of freedom to the controller.
The proposed control-aware motion planner applies a
sampling-based algorithm to search for a solution directly in
the task state space X Y = C Y # VY # A Y, which in gener-
al represents all possible poses ^C Y h, velocities ^VY h, and

obs

q i +1

q i q (t )
Γ(q , v, xyd )

yi

y

y

y i +1
d (t )

Figure 8. A schematic representation of the control-aware
planning paradigm. Each trajectory in the task space (below)
corresponds to a motion of the robot generated by the control
method (above).

Figure 9. An illustration of a planned trajectory for a pipe
inspection. The planned trajectory allows the robot to maintain
contact between the sensor (installed at the end of the arm) and
the inspected pipe while avoiding collisions with the other pipe on
top. The path followed by the sensor is represented by the red line.

Figure 10. An outdoor contact inspection experiment with the
AEROARMS aerial robot.

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december 2018

accelerations ^A Y h of the end effector when it is limited to a
given task. Figure 8 shows a schematic of the approach.
The planner can find trajectories in constrained environ-
ments where a purely reactive, gradient-based approach fails
because of local minima traps. Figure 9 shows one of the sce-
narios used for evaluation in a simulation reproducing a plau-
sible I&M application by contact, which requires the end
effector to constantly be touching and perpendicular to the
pipe. The planner requires about 20 s to obtain a solution tra-
jectory in this context.
AEROARMS Aerial Robot for
Industrial Contact Inspection
Various control, perception, and planning algorithms and
functionalities have been described in the previous sections.
After a research period during which different approaches
and functionalities were developed and tested in controlled
environments, all of this know-how was applied to develop
an aerial robot for industrial outdoor contact inspection
(Figure 10), which is AEROARMS's first use case.
The main characteristics of this aerial platform, called
AEROX, are shown in Table 1. It has an eight-rotor configura-
tion with a small angular gap at the front and back of the
vehicle to allow the robotic arm to pass between the propel-
lers. The motors are tilted alternately 30° around the arms,
allowing control of lateral acceleration to prevent the platform
from tilting. Moreover, this machine exhibits a special design
integrating a new type of aerial robotic manipulator that can
rotate around the vehicle's CoM and allow robust contact
operations that are suitable for precise industrial inspections.
This novel manipulator can orient the end effector in 1 DoF
(up and down) with 180° of working space, efficiently deal
with external perturbations (wind, force, and torques generat-
ed from the contact), maintain a specific force in contact with
the surface, and calculate the position of the end effector with
respect to the aerial robot.
To validate this configuration, many experiments were
conducted. The video at https://youtu.be/vc6E_3iS690 pro-
vides a summary of these investigations, including laboratory
tests in an indoor test bed with a motion-tracking localization
system used as ground truth, outdoor experiments with a
safety tether, and outdoor free-flight experiments.
As shown in Figure 11(a), each time the rope was pulled, a
perturbation along the rolling axis of the vehicle was pro-
duced due to the pulling direction and the rope anchoring to
the landing gear under the center of gravity. The relative posi-
tion of the robot was validated using the ground-truth local-
ization system. As a result, we obtained precise estimations,
with a root-mean-square error of 9.2 mm.
A teleoperation device, specifically designed for contact
inspection operations, was developed. It is composed of the
following elements:
● a video camera to allow remote viewing of the area
of interest
● a wheeled system to move the end effector when it is in
contact with the pipe
https://youtu.be/vc6E_3iS690
IEEE Robotics & Automation Magazine - December 2018

Table of Contents for the Digital Edition of IEEE Robotics & Automation Magazine - December 2018
