This feature was first published in April 1991. In it teacher Marcus Topham explains how sensors transform the capabilities of a robot. In the original article Marcus explained what sensors mean to a robot and how where you find sensors in the animal world and in machines and some suggestions of how to introduce sensors to children. Of course things since those days the “connected world” has arrived and sensors are everywhere. However, the basic ideas behind sensors has not changed, so we have taken the opportunity to update the article.
Without sensors robots are confined to living in their own world, ‘blind’ to everything that goes on about them. Sensors change this. With sensors the Roamer is able to react to its environment. The consequences may be very exciting. Here, Marcus Topham continues his series of articles on the Classic Roamer Control features by introducing the world of sensors.
Adding sensors to a robot may do little to change its appearance, but its ability to react to its environment demonstrates the radical difference between it and a senseless automaton. However, the powerful and subtle ideas involved make learning about sensors potentially a difficult task. This means that, before introducing Roamer sensors it is worthwhile spending a significant amount of time on preparatory work.
Investigate how animals and plants sense. A comparison of human and animal sensors can prove very interesting. For example, in comparison with us, the mole is virtually blind; on the other hand a hawk can see a small mouse running through the grass from a height of 30 metres
Bats have a radar sense that allows them to detect obstacles in the dark
Sensors are used to tell us how fast a car is going, or if it is about to run out of petrol or if handbrake is on. We are surrounded by machines that use sensors. This provides an excellent topic for a project.
Sensors need not be hi-tech. Some old shops still have bells on the door which sense when the door is opened and ring to alert the shop keeper. A project on old types of sensors incorporating a visit to an industrial museum can be worthwhile.
The diagram below illustrates all the basic elements of a sensor system.
The German Philosopher Immanuel Kant (1724 – 1804) proposed that our perceptions of the world limited what we could understand about it. There are individuals with synaesthesia and autism who see the world in different, often extraordinary ways. So what really exists? In general our predicament can be understood by considering a thermometer. To a thermometer the world is not just deadly silent, but the whole concept of sound does not exist. All a thermometer understands is temperature. A Baltic German, this time a scientist, Jakob von Uexküll (1864 – 1944), realised that different creatures saw the world in different ways. Each animal has an umwelt – which literally means environment or surroundings and is used to describe the way . The idea of the umwelt inspired Norbert Weiner (1894 – 1964) a German American mathematician and philosopher who pioneered cybernetics – the study of communication and control systems in living systems and in machines in general. This includes robotics and telecommunications. This idea also influenced the educational psychologist Jean Piaget (1896 – 1980) who started his career as a biologist studying zoology.
The diagram above illustrates a sensor system that is familiar to us all. If we look at it as a control system we see:
Below is an example of one of a number of simple sensor games presented in the Valiant Sensor Pack.
Blindfold one of the children who starts to walk across the classroom directed by a partner who gives them directions by clapping. A strategy must be agreed between them first; e.g. one clap, turn left 90°, two claps turn right 90°, etc.
These games are very useful for introducing children to something akin to a how Roamer perceives the world. They are also very revealing about the type of strategy the Roamer requires to perform various tasks.
As we see above switching on the light (stimulus) is detected by the sensor (eye) which transmits a signal along the Input Line (nerves) to the computer (brain). The computer interprets the signal and decides how to react.
The Roamer mimics our sensor system: we carry on doing something until something else ‘catches our attention’. This interrupt principle is how Roamer works: it will carry out a task until interrupted by a sensor. This is an important difference between the Roamer and many other educational sensor systems. Other systems require the computer to monitor constantly what is happening to the sensors. The advantage of the human like Roamer system is that it relates to the child’s own experience.
There are a number of terms used with electronics in general that also apply to robots. The following is how we use these terms in relationship to Roamer. You will quickly see that the use of the terminology is not that rstrict and is normally understood in context.
Roamer has one input and one output ports (there are plans to add an expansion module).