Computational Intelligence - November 2013 - 37

trajectory, however fuel line ruptures, total
5DOF spacecraft models were used to test
loss of control thruster(s), loss of sensor
payload and even complete agent loss may
operations complemented by virtual reality simulations
result from major impact events. Hardware
in jBullet.
failure may occur as a result of a collision
instance, it may also occur as a random
hardware "glitch" that the agent must also
be tolerant to.
environment and a representative hardware system. We sought
The complete system is a multi-language software
to explore the system's flexibility in an environment requiring
system: the abstraction processes and agent reasoning are
a high degree of autonomy, and its feasibility for real-time
performed in Java and the spacecraft hardware is modeled
implementation.
in Simulink, which in turn uses skill abstractions developed
Encoding agent abilities through natural language abstracwith sEnglish. The hardware actions are propagated within
tions resulted in an intuitive interface into system operation;
the Java based asteroid environment; a schematic of
this is an innate advantage of the method used. In turn this
this software system and their interactions is given in
abstraction link to hardware and software processes provided a
Figure 8(a).
clear link between reasoned decisions and output actions. This
The simulation was initialized with four spacecraft
resulted in a syntactically clear agent system, where its configuagents distributed throughout a partially known asteroid
ration and subsequent operation is entirely transparent. The
field, with the high level goal of cataloging all the observabstraction method also facilitated expansion and modification
able asteroids. The spacecraft were able to negotiate (and
of agent capabilities without disturbing existing abilities, as was
renegotiate) responsibilities for orbiting asteroids, correct
evidenced with the transferal of the system to hardware; the
for thruster malfunctions, and operate in phased orbits of
several spacecraft around a single asteroid. This is shown in
Figure 9. Dur ing all operations, notification of an
approaching solar storm acted to override all current activities, forcing the spacecraft to seek shelter behind the closest suitable asteroid.
B. Hardware Implementation

For application of the agent system on hardware, true hardware
processes and real dynamics replace the Simulink models and
jBullet simulation used within the complete software application. This integrated (hardware) agent system is shown in Figure 8(b) and the ground based hardware facility used is shown
within Figure 10.
On transferal of the agent system architecture to the hardware system, there is a clear difference between interfacing true
hardware devices and those modeled within Simulink. Bridging this gap relates to enriching the sEnglish database to
include interface for the specific hardware devices being implemented; neither the high level sEnglish performative abstractions, nor the agent reasoning code, were modified for the
hardware application.
The test facility demonstrated the capability of the agent
architecture to perform aspects of the asteroid scenario, namely
motion to 'nominated' points with disturbance compensation
and phased orbiting of a nominated point, through negotiation
with companion agents. Videos of some of these actions are
available to view at http://www.sheffield.ac.uk/

Figure 9 Screen capture of two spacecraft agents entering a phased
orbit about a nominated asteroid.

acse/staff/smv.
VI. Observations

This article has presented the application of a formally verifiable agent architecture, linked to a skill abstraction library formulated in a natural language, within a complex simulation

Figure 10 Image of the ground test facility and model frame "spacecraft" robots.

November 2013 | Ieee ComputatIoNal INtellIgeNCe magazINe

http://www.sheffield.ac.uk/

Table of Contents for the Digital Edition of Computational Intelligence - November 2013