【正文】 subsumption might be there implicitly 1. More plex behaviors? ? This approach won?t necessarily lead to system capable of more plex behaviors. A new controller is needed for each task. 2. Is it an evolution? – The experimenter is deciding on what modules to add, and what environment and task the robot should be exposed to. not the same as evolution. – But in terms of evolution, new behaviors and new mental structures are learnt in response to the environment, not added by an experimenter. – Similarly, in the development of an individual, new representational structures are developed in response to the environment, not added by an experimenter. Criticism of Subsumption 3. It would be more impressive if the robot learnt new behavior modules in response to the environment. – This possibility is discussed by Brooks (1991), but not yet successfully tackled. 4. Emphasis in this approach on reacting to the environment. – And it is the case that apparently quite sophisticated behaviors can result from simple reaction to the environment. – But representations are needed for more plex tasks. ? . ?Find an empty can and bring it back to the starting point? requires the formation of an internal representation corresponding to a map. ? Need to provide an account of the development of representations. Criticism of Subsumption Other Reactive Approaches Other Reactive Approaches ? Two other reactive approaches that are popular ? Potential field method。 modeling – keep more state – planning further in the future ? Layers can fake the inputs or outputs of other layers subsumption advantages (according to Brooks) ? Provides a way to incrementally build and test a plex mobile robot control system ? Supports parallel putation in a straightforward, intuitive way ? Avoids centralized control。 outputs – Modules are asynchronous ? No centralized clock ? No central memory Module Conflict resolution on a path from sensors to actuators Example of suppression A Behaviorbased Architecture for museum robot A Behaviorbased Architecture for Box Pushing Global reward Local Rewards on all levels Suppression is build in hardware Connections between layers ? Layer0 is lowest – Layer1 is next – Etc. ? Layers are designed to have separate goals – Lower layers deal with more important goals – ., important = survival ? Connections across layers – Layer1 connects to Layer0。 beta (balance) motor ? Level2: simple walk – does not pensate for rough terrain ? Level3: force balancing – Compensates for rough terrain ? Level4: leg lifting ? Level5: whiskers ? Level6: pitch stabilization ? Level7: steered prowling Layers and modules ? Each layer consists of a number of modules ? Modules – Module is a hardware ponent ? CPU + memory + specialized hardware + program ? Modules connect to other h/w ponents via physical wires ? Connections are fixed by design。 interaction Levels for the Genghis Robot ? Level1: standup – 2 modules per leg。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 o