About Sensors
Information about Sensors
In robotics, the sensor programming is called "open loop" or "closed loop".
Open loop robotics, is where a controller requires an actuator to be activated, and it assumes that the required action has taken place. An example of this is wipers on a car. When the driver turns them on the system turns on the actuator (wiper motor), and that is it...it assumes it is working.
In a closed loop system, when the controller fires an actuator, it will read a sensor to determine what has actually happened. An example of this is when you ask a DVD player to PLAY, but there is no disk inserted, the DVD player will issue a message like "no disk inserted", because it reads a sensor that detects if a disk is present or not.
So in robotics, the sensor range chosen is as important as the controller being used.
Sensors come in various types. The ones we sell include rangers (infra-red and sonic), bump detectors, cameras, tilt detector, compass and GPS units.
The sensors are normally dynamically active. That means the sensor only does it's function when asked to by the controller. In the case of rangers (distance measuring sensors), the controller will "ping" the sensor which will send out a burst of infra-red or a screech of ultrasonic sound. The ping then bounces off any obstacle in it's path, and the same sensor will detect it's echo, and by time delay (or angle of return) will calculate a distance.
Other sensors include the bump detector. This just closes a microswitch when an antenna bumps an obstacle. The GPS, compass and tilt unit are self explanatory.
All sensors return some information to the controller, which will process the information, and make the robot move accordingly.
The most complex sensor that requires a good controller to operate, is the colour camera. Two may be used to emulate stereo vision, or one can be used when a frame is shot, the robot moves and another shot is taken. The combined two images may be treated as stereo vision, and distance can be calculated accordingly.
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