Introduction to Artificial Intelligence CS 438 Spring 2008 Today –AIMA, Ch. 25 –Robotics Thursday –Robotics continued Home Work due next Tuesday –Ch. 13: 13.6 a – d –Ch. 14: 14.1 a – d BigDog Robot

Robotics Logistics We have enough robots for every 2 people Pair programming Find a partner by Thursday –Preferably one that has your has a schedule similar to yours

Why Study Robotics?

Where are the Robots? Exploration

Where are the Robots? Industrial Robots

Where are the Robots? Medicine

Where are the Robots? Service Robots

Where are the Robots? Consumer Robots

Where are the Robots? Cultural Robots Advances in AI and in Robotics are one and the same.

And It’s Fun

What is a Robot? An autonomous system which exists in the physical world, can sense its environment, and can act on it to achieve some goals.

Living Autonomously An autonomous robot acts on its own decisions Robots are not directly controlled by humans –Can take input and advice from humans Robots are not teleoperated –Making them much more difficult and interesting than Battlebots

The Physical World is Harsh Partially observable Stochastic Continuous Dynamic Multi-agent (typically)

Dealing with the Physical World A robot needs to be able to handle its environment or the environment must be altered and controlled. Close World Assumption –The robot knows everything relevant to performing “Complete World Model” –no surprises Open World Assumption –The robot does not assume complete knowledge –The robot must be able to handle unexpected events.

Sensing the Environment Sensors allow the robot to perceive its environment to get information that allows it to make decisions –Humans have 6 senses what are they? –What sensors does a robot need? Movie Clip

Acting on the Environment Robots have effectors that allow it to change the state of the world –What are human effectors? –What effectors can robots have? Movie Clip

Achieving a Goal Achieving a goal requires intelligent decision making –Artificial Intelligence Movie

Spectrum of Self-Control Teleoperation: Human Control Shared Human – Robot Control Autonomous (AI) Control

Spectrum of Robot Control

Autonomous Mobile Robots have to Solve Difficult Problems Where am I? –Localization Problem How do I get there? –Path Finding Problem How do I find the door? –Object Recognition Problem What are you asking me to do? –Language Understanding Problem How can I tell you the answer to your question? –Speech Generation Problem

how much of the world do we need to represent internally ? how should we internalize the world ? what inputs do we have ? what outputs can we effect ? what algorithms connect the two ? how do we use this “internal world” effectively ? What is a Robot Control Architecture? Robot Architecture

Robot Control Architecture

Deliberative/Hierarchical Robot Control Emphasizes Planning Robot senses the world, constructs a model representation of the world, “shuts its eyes”, creates a plan of action, makes the action, then senses the results of the action.

Sense - Plan - Act SENSING ACTING perception world modeling planning task execution motor control senseplanact Stanford Cart Shakey 1968 MERs 2003-

Deliberative: Good & Bad Goal Oriented –Solve problems that need cognitive abilities –Ability to optimize solution Predictable Dependence on a world model –Requires a closed world assumption Frame Problem Symbol Grounding Problem

Reactive/Behavior-Based Control Ignores world models “The world is its own best model” Tightly couples perceptions to actions –No intervening abstract representations Primitive Behaviors are used as building blocks –Individual behaviors can be made up of primitive behaviors Reactive: no memory Behavior-Based: Short Term Memory (STM) SenseAct

Sensing and Acting Reactive Paradigm tightly couples perceptions to actions –No intervening abstract representations or time history Individual Behaviors are used as building blocks StimulusBehaviorResponse SR Diagram

Behavior Coordination If multiple behaviors are possible which one does the robot do? –Competitive coordination: winner-take-all –Cooperative coordination: behavioral fusion –Combination

Where does the overall robot behavior come from? No overall goal, no planning Emergent Behavior –Emergence is the appearance of a novel property of a whole system that cannot be explained by examining the individual components, for example the wetness of water. –Overall behavior is a result of robots interaction with its surroundings and the coordination between the individual behaviors.

Reactive: Good & Bad Works with the Open World Assumption –Provides a timely response in a dynamic environment where the environment is difficult to characterize and contains a lot of uncertainty. Unpredictable Low level intelligence –Cannot manage tasks that require memory and higher level cognition Tasks requiring localization and order dependent steps

Hybrid Paradigm Lyons 1992 Combines Reactive and Deliberative Control Planner Sense Act

Planning – Reactive Interaction Reactive is primary control and Planner provides advise –Planner configures the Reactive system Planner is primary and Reactive provides actions to avoid uncertain situations –Layered approach –Requires re-planning Planner and Reactive work concurrently