【正文】 control alpha (advance) amp。s General Robot Requirements ? He identified a number of requirements of a control system for an intelligent autonomous mobile robot. ? Multiple Goals: – Some conflict, context dependent ? Multiple Sensors: – All have errors, inconsistencies and contradiction. ? Robustness: – The robot must by faulttolerant. ? Extensible: – You have to be able to build on whatever you built Subsumption architecture the Brooks’ approach – levels of petence ? example petences – layers of control ? subsumption – structure of layers – extensions – finite state machines What were the weaknesse of traditional approaches? ? Can?t account for large aspects of Intelligence ? Reliant on representation ? In real problems we have rapidly changing boundary conditions ? Hard to map sensor values to physical quantities ? Not robust ? Relatively slow response ? Hard to extend ? Hard to test Brook’s Dogma ? Brooks also introduced, what he called, 9 dogmatic principles, – 1) Complex (and useful) behavior need not necessarily be a product of an extremely plex control system. – 2) Things should be simple: Interfaces to subsystems etc. – 3) Build cheap robots that work in human environments – 4) The world is threedimensional therefore a robot must model the world in 3 dimensions. Dogma (cont) ? 5) Absolute coordinate systems for a robot are the source of large cumulative errors. ? 6) The worlds where mobile robots will do useful work are not constructed of exact simple polyhedra. ? 7) Visual data is useful for high level tasks. Sonar may only be good for low level tasks where rich environmental descriptions are unnecessary. ? 8) The robot must be able to perform when one or more of its sensors fails or starts giving erroneous readings. Dogma (cont) ? 9) We are interested in building artificial beings – robots that survive for days, weeks and months, ? without human assistance, ? in a dynamic plex environment. – Such robots must be selfsustaining Solution: Subsumption ? Brooks and his group eventually came up with a putational architecture. ? Model arrived at by continually refining attempts to program a robot to reactively avoid collisions in a peoplepopulated environment. ? Not intended as a realistic model of how neurological systems work. ? The model is called subsumption architecture”. ? Its purpose is to program – intelligent, – situated, – embodied agents. new architecture: subsumption ? Introduced in Brooks? seminal 1986 paper ? Consists of layered behaviors, – from simple to plex, – with simple interfaces ? Layers can “override” each other ? Each layer has a control program that is capable of working at the speed of environmental change ? Each layer now can do: – the appropriate model building, – sensor fusion, – etc. ? 1. No central model of world. ? 3. No separation into perception, central processing, and actuation. ? 3. Layering increases capabilities. ? 4. No hierarchical arrangement. ? 5. Messages on input ports when needed. ? 6. Behaviors run in parallel. Basic Architecture of an autonomous agent Sensors Cognition Effectors Vision, range, touch Decides actions and Carry out actions mands effectors Subsumption Architecture ? Control Problem for an autonomous robot ? Traditional Approach: – functional deposition ? A new approach – deposition by activity Main difference in the deposition type Motivation To achieve cooperation and coordination among different robots and self governance with human like performance in a mon work space. Key Problems for Subsumptionbased mobile robots. ?Cooperation ?Coordination ?Learning ?Vision ?Localization Subsumption Architecture ? 1. Reactive robotics approach, which Brooks calls “behavioral robotics.” ? 2. The central idea of Brooks? approach is that more sophisticated robot petencies should be built on top of simpler ones. ? Instead of all robot inputs feeding into a sensory perception unit, which creates a “world model” of the robot?s environment, which feeds into a planning module, Brooks has argued that: – robot perception and action should be closely linked, – plex behaviors can be built from the interactions of simple ones. ? Example: – a robot that must walk should first learn to stand. – Then later behaviors can “exploit” earlier ones: a task which causes a legged robot to move its legs can make use of the knowledge embedded in the behavior that allows the robot to simply stand. Subsumption Architecture: Massiveness ? Brooks has proposed that future unmanned interplaary missions should be performed by hundreds—or thousands—of simple, insectlike robots that act in teams to acplish work, rather than a large and plicated monolithic device. ? Individual robots could be considered expendable without jeopardizing the success of the entire mission, whereas if a single large robot had a failure, the mission would be over. ? Homework (not this year): ? Read: ? Rodney Brooks?s paper on “Fast, Cheap, and Out of Control” Behaviorbased Robotics started earlier, in about 1984 ? Groups at MIT and SRI independently began rethinking how to anise intelligence (around 1984). ? Requirements: – Reactive to dynamic environment – Operate on human time scales – Robustness to uncertainty/unpredictability ? They implemented simple systems with similar features. Subsumption Priciples: Network Construction ? 1) Computation is anized as an asynchronous work of active putational e