Sensor-based formation control using a generalised rigidity framework and passivity techniques
Date
2016
Authors
Stacey, Geoff
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Abstract
The research in this thesis addresses the subject of sensor-based
formation control for a network of autonomous agents.
The task of formation control involves the stabilisation of the
agents to a desired set of relative states, with the possible
additional objective of manoeuvring the agents while maintaining
this formation.
Although the formation control challenge has been widely studied
in the literature, many existing control strategies are based on
full state information, and give little consideration to the
sensor modalities available for the task.
The focus of this thesis lies in the use of a generic arrangement
of partial state measurements as can commonly be acquired by
onboard sensors; for example, time-of-flight sensors can be used
to measure the distances between vehicles, and onboard cameras
can provide the bearing from one vehicle to each of the others.
Particular aspects of the problem that are addressed in this
thesis include (i) ways of modelling the formation control task,
(ii) methods of analysing the system's behaviour, and (iii) the
design of a formation control scheme based on generic
arrangements of sensors that provide only partial position
information.
A key contribution in this thesis is a generalisation of the
classical notion of rigidity, which considers the use of distance
constraints between agents in R^2 or R^3 to specify a rigid body
(or formation).
This enables the concept of rigidity to be applied to agent
networks involving a variety of (possibly non-Euclidean)
state-spaces, with a generic set of state constraints that may,
for example, include bearings between agents as well as
distances.
I demonstrate that this framework is very well-suited for
modelling a wide variety of formation control problems
(addressing goal (i) above), and I extend several fundamental
results from classical rigidity theory in order to provide
significant insight for system analysis (addressing goal (ii)
above).
To design a formation control scheme that uses generic partial
position measurements (addressing goal (iii) above), I employ a
modular passivity-based approach that is developed using the
bondgraph modelling formalism.
I illustrate how adaptive compensation can be incorporated into
this design approach in order to account for the unknown position
information that is not available from the onboard sensors.
Although formation control is the subject of this thesis, it
should be noted that the rigidity-based and passivity-based
frameworks developed here are quite general and may be applied to
a wide range of other problems.
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Keywords
formation control, vehicle formations, agent formations, sensor modeling, sensor modelling, partial state measurements, rigidity theory, generalised rigidity, generalized rigidity, passivity based control, bond graph modelling, bond graph modeling
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Thesis (PhD)
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