【正文】 relies on selfcentered and autonomous modules ? Leads to more emergent behavior “Complex (and useful) behavior may simply be the reflection of a plex environment” – Compare with SPA intelligence is entirely in the design of the planner (the programmer) subsumption successes ? Early efforts were a dramatic success, zipping around like R2D2 instead of pondering their plans ? “Pinnacle” was Herbert, who found soda cans in an office Criticism of Subsumption ? Herbert didn?t work very repeatably ? No subsumptionbased robot since Herbert or is there? ? Is “classical subsumption” still in use? – Cog is based on subsumption? – Brooks? publications, however, mainly describe imitation of human cognitive models and do not explicitly mention “subsumption” – But, these models also stress nonmonolithic control。 not dynamic ? Connections between modules are low bandwidth ? Modules within a layer – Interconnect with data inputs amp。 (one or more stop states) – a set of symbols – a set of transitions ? For example – an FSM for a light switch off on switch switch ? An FSM can be implemented in C – using a state variable and switch statement Let us look again to more limitations of Conventional Approaches ? Perception takes too long ? Perception is not a solved problem, nor will it be solved in the near future. ? Modeling/planning ponent assumes plete models are available ? Overall system cannot respond in realtime ? Most robots built this way have failed – (or run very slowly) And the response of the Behaviorbased Approach ? Depose overall control system into a layered set of reactive behaviors ? Each behavior represents a plete mapping from sensors to motor mands ? Lowlevel behaviors (. avoid) can run in realtime since they use little putation ? Highlevel behaviors are invoked only when necessary ? Requires arbitration strategy to choose among (or bine) conflicting behaviors What does it mean that behaviors run in parallel and control directly? ? The control system is broken down into horizontal modules, or behaviors, that run in parallel – each behavior has direct access to sensor readings and can control the robot?s motors directly sense observe changes build maps explore wander avoid objects act Brooks’ Assumptions for mobile robots: Complex behaviors from simple controls ? Complex and useful behavior need not necessarily be a product of an extremely plex control system ? Things should be simple – if a single module is getting too big: rethink the design – unstable or illconditioned solutions are not good ? Ability to wander in real environments is crucial ? Absolute coordinate systems are a source of error – relational maps are more useful to a mobile robot ? The real world is not constructed of exact shapes – models may be useful, but should not be used alone ? Sonar data, while easy to collect, do not lead to rich descriptions of the world – visual data is much better ? For robustness, the robot must be able to function when one or more of its sensors fails or starts giving erroneous readings – recovery should be quick (selfcalibrating) ? Robots should be autonomous and selfsustaining (able to survive weeks without human assistance) Brooks’ Assumptions for mobile robots: sensors integration and autonomy how much / how do we represent the world internally ? Just what we need. Subsumption paradigm Motor Schemas ? Subsumption poses simple reactions (behaviors) by letting one take control at an appropriate time. ? World state is puted in order to perform a specific task. Robot Architecture Larger example Genghis 1) Standing by tuning the parameters of two behaviors: the leg “swing” and the leg “l(fā)ift” 2) Simple walking: one leg at a time 3) Force Balancing: incorporated force sensors on the legs 4) Obstacle traversal: the legs should lift much higher if need be 5) Anticipation: handles touch sensors (whiskers) to detect obstacles 6) Pitch stabilization: uses an inclinometer to stabilize fore/aft pitch 7) Prowling: uses infrared sensors to start walking when a human approaches 8) Steering: uses the difference in two IR sensors to follow 57 FSM?s wired together ! Genghis The Approach – Don?t use logicbased description of percepts – Don?t apply search operators or logical inference or planning operators ? Goal formalized, but not generalized – Arrive at a next action, not operator sequence – Apply that operator sequence to world (detail) ? Respond based on contingencies amp。t even very good vehicles. ? Brooks identified various aspects of mobile robotics which he considered to be important and obvious Key Topics of Behaviourbased Approach ? Situatedness ? Embodiment ? (animal or insect) Intelligence ? Emergence Situatedness A situated automaton is a finitestate machine whose inputs are provided by sensors connected to the environment, and whose outputs are connected to effectors. The world is its own best model Traditional AI, working in symbolic abstracted domain. Problem solvers which are not participating in the world as agents. Dealing with model world no real connection to external world. ? Alternative approach, to use a mobile robot which uses the world as its own model, referring to information from sensors rather than internal world model. ? Representations are developed which capture relationships of entities to robot. ? Situated agent must respond in timely fashion to inputs。For the exam next Thursday 1. Reactive architectures for robots, quantum and standard Braitenberg Vehicles and their “emotions” 2. State machine architectures 3. GA and GP in all kinds of robotic applications. 4. Robot in labyrinth 5. Grammar generation of motion, dialog and