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Autonomous Mobile Robotics > 9 - Control Architectures > Flashcards

9 - Control Architectures Flashcards

1
Q

Name 5 problems you may encounter with robotic behaviours?

A

Complex environment

Noise/unpredictable environment

Actions don’t always lead to intended consequences

Misleading sensors

Responses are too sloe

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2
Q

Why do you need control architectures?

A

How to bring a range of competencies together into a single system that can operate autonomously (and reliably, in a complex world)

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3
Q

What is the definition of the robot control paradigm?

A

A philosophy or set of assumptions and/or techniques which characterise an approach to a class of problems

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4
Q

What are the 3 main control architecture paradigms?

A

Deliberative, reactive, hybrid

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5
Q

How do you typically characterise the 3 control architecture paradigms?

A

Through the fundamental primitives, sense, plan, act

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6
Q

What is sense?

A

Sensing the environment, takes raw sensor data and returns the sensed information

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7
Q

What is plan?

A

Deciding what to do using some model of the world, takes sensory information and returns directives

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8
Q

What is act?

A

Acting on the environment, takes in sensory information of directives and returns actuator commands

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9
Q

What is the extra control architecture?

A

Cognitive

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10
Q

What is a deliberative architecture?

A

Planning what action to take, assuming you have a world model then doing it.

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11
Q

What is the basic process of a deliberative architecture?

A

Gather currently available information and integrate it into the world model, plan what to do, then execute the plan and return the step 1

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12
Q

What does the deliberative architecture emphasise?

A

A top down (hierarchical) planning process, partly inspired by human introspection

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13
Q

What is STRIPS?

A

Stanford Research Institute Problem Solver

Symbolic representation of all information

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14
Q

What are the 4 parts to STRIPS?

A

The world model (everything about the state of the environment)

The capabilities/properties of the robot itself (operators)

Initial and goal states

Difference evaluator (how close to the goal state am I?)

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15
Q

What is PDDL?

A

Planning Domain Definition Language.

STRIPS plus extensions, common assumptions, benefits, shortfalls

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16
Q

What is the difference between STRIPS and PDDL?

A

STRIPS is a specific planner/language, PDDL is a more recent standardised planner

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17
Q

Name 5 limitations of deliberative architectures?

A

Closed World problem (all information is present, nothing unexpected, no unanticipated consequences)

Frame problem (what is and is not relevant, should enumerate all states even if unchanged)

Brittleness problem (can’t handle change not effected by the agent)

Uncertainty problem (how should this be handled in a symbolic planner that assumes crisp knowledge and true/false conditionals)

Computational load (high load leads to slow reactivity)

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18
Q

What is a reactive architecture?

A

Direct reaction against deliberative models

Emphasis on fast reaction to low-level sensory information, without involved processing and planning

19
Q

What is the basic process of reactive architectures?

A

Sensory input acquired, multiple parallel behaviours result in overt agent actions

20
Q

What are 3 benefits to reactive architectures?

A

No internal world model is needed

Real-time behavioural control

Can have emergence of complex behaviour with little design effort

21
Q

What is behaviour based robotics?

A

Typically reactive, tightly coupled to sensor information (no planning or internal state)

In the design of the robots, strong focus on robot’s body

Interaction with environment

22
Q

What are ego-centric representations?

A

Deals with the limitation of having no world model.

Provides some structure and helps with choosing what to do

23
Q

Name 3 roles for a coordinator in multiple behaviours?

A

Competitive (winner takes all)

Cooperative (blend outputs through addition)

Hybrid (activation/inhibition dynamics)

24
Q

What is a subsumption architecture?

A

A single example case of behaviour-based control architecture

Gets around the coordinator problem by having higher level behaviours subsume lower level behaviours (i.e some behaviours can over-ride others)

25
Q

What are the limitations to reactive architectures?

A

Oriented to specific task (lack of generalisation)

Based on, and constrained by particular robot embodiment

Sensitivity to sensor noise

Lack of planning

Stimulus response alone insufficient to account for intelligence

Emergence of complex behaviour is a design problem

26
Q

What are hybrid architectures?

A

Trying to get the best of both deliberative and reactive paradigms

Multiple levels of control, each focused on a difference aspect

Some planning where appropriate but maintaining ability to respond quickly to the environment

27
Q

How can you get the best of both in hybrid architectures?

A

Use symbolic processing and world models/maps for planning and use reactive behaviours for fast responsive action

28
Q

What is temporal decomposition?

A

Deliberative uses horizontal decomposition of the task and reactive uses vertical decomposition of tasks, temporal resolves this by using time-appropriate processes where different layers have different speeds of processing

29
Q

Discuss the speed of horizontal decomposition and vertical decomposition

A

Horizontal decomposition of the task is used in deliberative architectures and can be slow, whereas vertical decomposition of the tasks are used in reactive architectures and can be too quick

30
Q

What are the 3 tiers in the Three Tier (3T) architecture?

A

Controller, sequencer/executive/deliberator

31
Q

Discuss the controller in 3T

A

Library of behaviours, must be fast, must be able to detect failure (allows sequencer/executive to call another behaviour or call for replanning)

32
Q

Discuss the sequencer/executive in 3T

A

Drives the control of the system, selects which behaviour will be active, initiates behaviour and planning

33
Q

Discuss the deliberator in 3T

A

Operates on its internal state (world model, no sensing), time consuming and computationally intensive tasks, no commitment to the means of processing, and operation is directed by the sequencer/executive

34
Q

What are the advantage of 3T and hybrid?

A

Specification of overall structure, and principle of operation rather than precise mechanisms

Maintains flexibility

If one algorithm is not appropriate then swap it out for another

35
Q

What are the issues with hybrid architectures?

A

Central role of the sequencer/executive

Symbol grounding (relevance of the representations to the instantiation/actions of the robot system it is planning for)

36
Q

What is a cognitive architecture?

A

Explicitly takes into account the way that humans may process information and act

Overlaps with the previous paradigms, particularly hybrid

37
Q

What is the definition of a cognitive architecture?

A

The overall, essential structure and process of a domain-generic computational cognitive model, used for a broad, multiple-level, multi-domain analysis of cognition and behaviour

38
Q

Why take inspiration from humans for cognitive architectures?

A

Humans demonstrate the best example of highly complex intelligence, and so could form useful design guides

If robots are to interact with humans in human environments then having them endowed with some human-like cognitive features could be useful

39
Q

What are 2 main approaches to cognitive architectures?

A

Derive a set of mechanisms to use from human behavioural or other data

Try to model fundamental principles of organisation of cognition and implement these

40
Q

What is ACT-R?

A

An established cognitive architecture that has been applied to numerous models of human behaviour

Based on evidence from pscyology and pysiology

Hybrid symbolic/sub symbolic processing

41
Q

What is HAMMER?

A

Hierarchical, Attentive, Multiple Models for Execution and Recognition

Fundamentally based on forward/inverse model couplings, and applied to imitation, learning, assistance etc

42
Q

What are 3 issues with cognitive architectures?

A

How related to biology should it be? (inspiration or constraints)

Suitable level of abstraction? (behaviour or mechanism)

What is the purpose of using a cognitive architecture? (functional or explanatory)

43
Q

What are multi-agent systems?

A

Coordinating multiple robots, emergent behaviour from swarms of robots

Autonomous Mobile Robotics (13 decks)

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