ORCA: A physics based, robotics simulator able to distribute ...

handle all environment processing through its server
object. Consequently it can
tackle the large computational
costs that are
inherent in complex robotic structuress and
large environments, by sharing and distributing resources
across simulation
instances.
This functionalityy
is
embodied through threee different properties in n the
simulator’s environment: (i) robot
sharing, (ii)
environment sharing, (iii) object sharing. Thesee are
outlined below.
A. Robot sharing
One of the main characteristics of a simulated robot is
that it utilizes resources that are modular, and can be
described by
an I/O convention. Consequently, in most
cases, rendering a simulated robot is a computationally
intensive task
that outputs only a small set s of parameters.
Consider for example the case where a “high degrees
of freedom” manipulator has to be processed within a
large environment. At any
given time, the simulatorr has
the duty to process its kinematic chain, integratee the
appropriate equations, and
update the position of the joints
of the hand
to simulate it. Even though this process
contains a large number of
computations, it is only used to
output a small amount of
information, , such as the end-
with such a robot, it is usually important to have onlyy this
point location
of the hand. Consequently, when interacting
piece of information available. Due to its design, ORCA
can facilitate
processing of
such roboticc structures locally,
and distribute outputs from the simulation on demand,
only when required (Fig. 6).
simulation environments or being transmitted by the
server.
B. Environment sharing
Another important feature of the ORCA
simulator is
its ability to share the processing requirements of large
environments. Such feature is becoming increasingly
important across research projects, and finds applications
in a large number of fields including outdoor robotics,
search and rescue simulations, swarm robots etc.
In these typess of environments, usually
the robot is
located within a small manifold space, which must
process. Upon initialization off an experiment, the serverr
loads a virtual world file whichh contains the definitions of
all objects that will be processed by simulation instances.
These are createdd as physical entities and entered into the
world without processing any of their properties (Fig. 7).
Figure 7. (right) The environment-sharing view of thee server showing
how different robots are being processed using different subsets of an
environment. (left) Rendered with redd is robot 1, green robot 2, while
transparently are rendered the surroundings that are not n processed by
any robot.
As soon as a new simulation instance is i loaded into
the new world, it communicates its location to the server.
The
server responds to the request of thee instance by
transmitting the environment and object properties thatt
are in the vicinityy of the roboticc client (Fig. 8).
Figure 6. The environment-sharing view of thee server showingg how
different robots are being processed using ORCA’s virtual robots. The
simulation instances transmit all required infromation to a server, which
for the given example, reduces the robot’s existence to a spatial x, y, z
vector.
To facilitate this feature, the latest ORCA release
includes an extensive network protocol that contains
messages pertaining to information sharing amongst
robots. Thesee messages are integrated within appropriate
environment parsers, thatt reside on the server andd are
responsible for filtering and transmitting to simulation
instances only the appropriate environment information.
In addition, the latest release uses virtual robots, simple
graphic structures with no physical properties, that can be
used to visualize information coming from other
Figure 8. Local copy of o the simulator that receives onlyy a partial view of
the environment.