While the Survivability Reference Architectureencapsulates the relationships between theneeds,actionsandemotionsof a system, its exact implementation takes on a myriad of forms. To ensure its efficacy, the primary consideration in the realization of the reference architecture is in preserving such relationships between these concepts by following the principles (i.e. 3.1 to 3.3) set out in section 3.8.4. With various realizations
of the relationships betweenneeds, actions, andemotions, a collection of architectures that bear close resemblances with some existing robotic paradigms are generated. Some of these architectures are discussed below.
Layered, behaviour-based architecture
A layered, behaviour-based architectural realization of the Survivability Reference Architectureis depicted in Figure 4.4. In this figure, eachneedis paired with an action that is activated given the intensity of theneed.Need-actionpairs are arranged in layers, and the output of each pair goes to a selection or arbitration mechanism that determines the action(s) to be performed. Some variations of this selection mechanism is found in Table 4.5. The difference between this architecture and a typical behaviour-based system is the addition of theneeds, a consistent scheme for determining the activation of actions. Thus, each equivalent behaviour is a “needs-motivated action.” This scheme is implemented in Use Cases D.2 and D.3 (sections D.3 and D.4) in Appendix D.
Subsumption-type architecture
Figure 4.5 shows a subsumption-type architectural realization of the Survivability Reference Architecture. In this architecture, each need activates an action. and all need-actionpairs are arranged in layers. The ordering of such pairings are in terms of relative importance. Each labelled node ‘S’ describes the suppression of activation for a lower priorityneed, by one of higher priority. Thus the subsumption of one behaviour by another, is implemented in this case as the suppression of activation of someneed- actionpairs over others, which provides aneeds-based interpretation of thesubsumption architecture. The main difference is the inclusion of an internal state representation (i.e.
the needs of the system) for this architecture, which endows subsumption with some form of representation.
Information-processing model based architecture
TheSurvivability Reference Architectureis depicted as an information processing model in Figure 4.6. Observations of the environment and the current internal state of the system are added to the state history in an internal memory space akin to a global workspace (Baars, 1997), which contains a history of the states, needs, and in which predictions about the changes in state andneedsare being stored. As the intensity of needsincreases, the actions that are motivated by theneedswould be brought forth for consideration for execution. Activation levels are computed and the final action(s) to
Needs1 Actions1
Selection desired action(s) Needs2
Needs3
Needsn
.. .
Actions2
Actions3
Actionsa
.. .
Perceived States
and Observations
Internal / External Environment
Figure 4.4: A layered behaviour-based realization of the Survivability Reference Architecture. The final selection or arbitration of action has several variations, as explained in Table 4.5.
Needs1 Actions1
Needs2
Needs3
Needsn
.. .
Actions2
Actions3
Actionsa
.. .
Perceived States
and Observations
Internal / External Environment
desired action(s) S
S
S
…
S
S
S
…
Figure 4.5: A Subsumption-type realization of the Survivability Reference Architecture.
Each labelled node ‘S’ describes the suppression of activation of one action by another.
be executed are arbitrated by a selection mechanism (section 4.9.2). To regulate this process, the progress of the fulfilment of theneedsare monitored byemotions. The role of emotions is to enable or inhibit the actions that are being considered. The unique characteristic of this architectural realization is that the relevant pairs ofneeds-action couplings that are considered for execution may change or be acquired over time.
Cognitive model based architecture
An architectural realization of the Survivability Reference Architecture is shown in Figure 4.7. It is a realization of the three-level cognitive model of human affect and behaviour by Ortony et al. (2005) which comprises thereactive, routine and reflection layers, as shown in Figure 3.5 and discussed in section 3.7.2. In this architecture, needs are divided into three different levels, which is a reorganization of the initial
Perceived States
and Observations
Internal / External Environment
Emotions
N1 N2
N3 N4
N5
E1 E2 E3 E4
A1 A2 A3
A4 A5
Needs history / predictions
Activations
Actions Needs
Enable/Inhibit
Selection desired action(s)
Global Workspace state history
and predictions
needs history
and predictions repertoire of intrinsic / acquired
actions
Figure 4.6: An information processing model of theSurvivability Reference Architecture.
Perceived States
and Observations
Internal / External Environment
Evaluative Actions
Reactive Level Needs
Routine Actions
Reactive Actions Emotions
Primitive Emotions Proto-affect
Reflective Level Needs Routine Level
Needs Selection desired
action(s)
activations
Enable / Inhibit
Enable / Inhibit Enable Inhibit
Figure 4.7: A cognitive model realization of the Survivability Reference Architecture, extended from the three-level model of human information processing by Ortony et al. (2005), as shown in Figure 3.5.
needs hierarchy (Figure 3.10). Actions are divided into three types, namely reflective, routine, andreactive. Emotions are distinguished intoproto-affect(at the reactive level), primitive emotions (at the routine level), and cognitively elaborated emotions (at the reflection level), in line with the explanation in (Ortony et al., 2005). Cross-activations of different actions byneedsin adjacent levels provide the interaction between the three levels. This architecture offers a possible explanation of the on-going processes within each level.
Emotions1
Emotions2
Emotions3
Emotionsm
.. .
Needs1 Actions1
measurements
activations
enable/disable
Selection State1
Internal / External Environment
interactions observations
state transformation
triggers State2
State3
States
.. .
Needs2
Needs3
Needsn
.. .
Actions2
Actions3
Actionsa
.. .
Environment Preferences Mechanisms Capabilities
Platform desired action(s)
Figure 4.8: A connectionistic realization of the Survivability Framework, showing the relationships between sensor data,needs,emotionsandactions.
Connectionistic architecture
The final realization of the Survivability Reference Architecture to be discussed, is depicted in Figure 4.8. This is a connectionistic architectural realization that relies heavily on the inter-connected relationships betweenneeds,emotionsandactions.
The implied implementation of such an architecture is with any connectionistic, or graph-based framework. In particular, there is strong architectural basis for the use of neural networks and fuzzy logic for a number of reasons. First the process ofneeds determination discuss so-far in this thesis is akin to fuzzification, namely the process of translating physical quantities into a membership value in the range[0, 1]. Second is the interconnection between concepts, which can be implemented in an artificial neural network. Alternatively, the whole configuration can be implemented withfuzzy cognitive maps(Kosko, 1986; Stylios et al., 1997), which would be shown in Use Cases 4 and 5 (sections 6.3 and 6.4) in Chapter 6.