Control systems.md (2179B)
1 +++ 2 title = 'Control systems' 3 +++ 4 # Control systems 5 Sensors: receive signals (microphones, cameras…) 6 7 Actuators: actually do stuff in the 'real world’ (LEDs, motors, speakers, displays, lamps…) 8 9 Controller: “the brain”, the intelligent unit. provide hardware & software that makes system autonomous by using sensor input etc. 10 11 any pervasive computing system executes sense-control-act sequence in a loop 12 13 Control: 14 15 - deliberative: think hard, act later 16 - planning — look ahead at outcomes of possible actions 17 - searching — looking for sequence of actions leading to desired goal 18 - use internal representation of the environment — a map, for example 19 - for decisions, use for example shortest path from one node to another in a map 20 - uses Dijkstra’s or A* algorithm 21 - GPS nav systems use this 22 - reactive: don’t think, react! 23 - e.g. smart curtains, thermostat, obstacle handling, landmark navigation 24 - don’t use internal representation, just direct mapping between sensors and effectors 25 - rules: 26 - if dark outside, then close the curtains 27 - control type 28 - open-loop control — input signal to controller, actuator, output controlled variable 29 - examples: microwave, automatic lights, automatic water faucets 30 - closed-loop control — get feedback, check if everything was executed right 31 - uses a comparator that gets feedback from output of actuator 32 - comparator outputs error to controller, which then tries to minimise error 33 - example: heater 34 - obstacle handling 35 - simple — contact (touch sensor) 36 - better — proximity, but don’t know distance (whiskers) 37 - best — ranging 38 - sonar, with reflected sound waves. echolocation (distance = speed × time) 39 - LIDAR, using a laser swept across FOV 40 - landmark navigation 41 - follow a line, a wall 42 - feedback control — turn always same angle, turn proportionally (P), proportional derivative (PD, rate of change), or proportional derivative and integral (PID, rate of change and time) 43 - others: hybrid, behaviour-based