【正文】 f 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 elements: – they are augmented finite state machines, – with a fixed topology of unidirectional connections. ? 2) Messages sent over connections have no implicit semantics: – they are small numbers (typically 8 or 16 bits, but on some robots just 1 bit), – their meanings are dependent on the dynamics designed into both the sender and receiver ? 3) Sensors and actuators are connected to this work, – usually through asynchronous twosided buffers. Subsumption Architecture: Incrementally build work of state machines ? Incremental method for building robots ? Network of finite state machines links sensors to actions ? Internal timers ? Control system built in layers of state machines ? Model: Message passing augmented finite state machines Finite State Machines ? In Brooks? original work, each module was implemented as a finite state machine – augmented with some instance variables ? A finite state machine has – a set of states ? a start state。 but much information from the world. Why situatedness is better for mobile robot behaviors? Embodiment Embodiment: Physical grounding of robot in real world. According to Brooks (1991), embodiment is critical for two reasons. ? Only an embodied agent is validated as one that can deal with real world. ? Only through a physical grounding can any internal symbolic system be given meaning. Emergence Intelligence emerges from interaction of ponents of the system. Behaviourbased approach intelligence emerges from interaction of simple modules. . Obstacle avoidance, goal finding, wall following modules. Sensors Actuators Level 3 Level 2 Level 1 Level 0 Main ideas ? No central model maintained of world ? No central locus of control ? No separation into perceptual system, central system and actuation system ? Behavioural petence improved by adding one more behaviour specific work to existing work. – Crude analogy to evolutionary development ? No hierarchical development ? Layers or behaviors run in parallel Main Ideas of Behaviorbased Approach Model of Brooks: the perceptual and action subsystems are all there really is: A. Brooks, “Cambrian Intelligence” Cognition is only in the eye of an observer Brooks Criticizes traditional robotics Intelligence is determined by the dynamics of interaction with the world = he says Some activities we think of as intelligent have only been taking place for a small fraction of our evolutionary lineage. ?Simple? behaviors to do with perception and mobility took much longer to evolve. Would make sense to begin by looking at simpler animals. looking at dynamics of interaction of robot with its environment. Example of Criticisms of traditional approach Brooks ? We should take evidence