IEEE Robotics & Automation Magazine - September 2017 - 45

Collision Check Library (FCL) [10]. To achieve MoveIt!'s main
goals of extendability and reusability, custom configuration of
these components can be combined through the plug-in system.
The modeling in MoveIt! uses unified robot description
format (URDF) and complementary semantic robot
description format (SRDF) extensible markup language
(XML)-based files. The URDF defines the visual shape and
the collision properties of the system, along with its
kinematics parameters. With the SRDF, planning group(s)
are defined by choosing the set of joints and links that act
together as a single entity capable of performing planning
and/or manipulation tasks by using its chosen kinematics
solver and planner. Also in this file, the self-collision matrix
is defined by choosing link pairs that are permitted to collide (e.g., adjacent links). The collision-checking library
incorporates this information during path planning.

bounded by the size of the water tank, where the experiments were carried out. Followed by three revolute joints
corresponding to (z, i, }) Euler rotations, two are noncontrollable (i.e., modeled as fixed joints) but included to
account for the small motions that the AUV may experience due to system perturbations. The } joint is modeled
as unlimited and continuous. The final configuration vector
of the AUV is Q = [q 1 q 2 q 3 q 4] T , representing the controllable part of the AUV pose vector NED h = [xyz}] T .
Arm Modeling
The arm is also modeled using the DH convention, and its
links have associated frames {L 4, L 5, L 6, L 7, L 8}, with the first
and the last associated to the arm base {0} and EE {ee},
respectively. The arm joint variables Q = [q 5 q 6 q 7 q 8] T are
configured as revolute joints with their corresponding
mechanical limits.

GIRONA500 UVMS Modeling

AUV-Arm Link Modeling
In Figure 3, a fixed virtual joint between the vehicle and
the arm is introduced, defining a transformation between
the AUV center and the arm base, thus linking both models together as one system. For visualization purposes, we
used a stereolithography file derived from the I-AUV
using computer-aided design. To account for collisionchecking and safety measures, the AUV is represented by
a square box defined as the shape of the last link in the

I-AUV Model H3
Figure 3 presents the I-AUV kinematics chain as modeled in
MoveIt!. A north-east-down ({NED}) frame is used as the global reference frame. Collocated in the same point, but rotated, is
the {R} frame that is used for visualization purposes. The robot
pose is defined by NED h = [xyzzi}] T , providing the origin
and attitude of the robot fixed frame {B} with respect to the
{NED} frame. The arm mounting pose vector is given by B rB0,
and the EE pose vector frame {n}, with
respect to the robot base frame {0}, is
given by 0 h ee. By compounding the
robot pose NED h, the arm mounting
pose B rB0, and the EE pose 0 h ee, it is
{R}
possible to compute the world-referNED
enced EE pose
h ee.
AUV Modeling
The AUV has 6 DoF, although the
roll and pitch are passively stable. As
a result, the vehicle is actuated only
in 4  DoF (surge, sway, heave, and
yaw). The AUV kinematics are modeled using the Denavit-Hartenberg
(DH) method applied to the equivalent Cartesian manipulator, shown in
Figure 3. For each link, a frame {L i} is
defined. {L 0} is placed with {NED}
but with the attitude required by the
DH algorithm to keep its motion axis
along the z direction. Similarly, {L 3}
is placed with the robot body-fixed
frame {B}, again with different attitude to follow the DH guidelines. The
vehicle motion is modeled as three
consecutive prismatic joints representing (X, Y, Z) displacements in the
{NED} frame, and their motion is

{NED}

q1 = x
{L1}

{L0}

q2 = y

{ L 2}
ηee

η
{Lφ}

φ

q4 = Ψ

q3 = z

{L3}

{B }

{Lθ}

{L6} {L7}
{L4} {L5}
q6
q7
q5
a1
a2 a3

rB 0

θ

η0ee
q8

θ
q1

d

a

α

Home

1

0

0.108

−90

0

2

q2

0

0.231

0

0

3

q3

0

0.1

90

0

4

q4

0.308

0

0

0

DoF

d4
{L8}

Figure 3. The I-AUV schema and arm DH kinematics parameters.

SEPTEMBER 2017

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IEEE ROBOTICS & AUTOMATION MAGAZINE

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