Controlling physical systems

Computers can only interact with the world if they are connected to input and output devices.

These devices allow them to respond to the world around them and to act according to their programming.

A computer can be programmed to respond to input devices like sensors. For example in a water heater, sensors are used to react to a drop in temperature and tell an output device, like a heating element, to heat up the water.

Different computers and sensors

Computers and sensors can be used to control conditions in lots of different places.

You might have sensors in your home to control the lights. When light sensors detect that it is dark outside a computer can instruct the lights in your driveway to switch on.

Traffic lights are another example. A computer responds to sensors on a camera, checking to see if cars are waiting. If they are, the lights are changed according to a set pattern.

These are simple programmed actions in response to external changes.

Sensors can also be used to control the heating. If the temperature of the house gets too low or high a computer can instruct the heating or air conditioning to turn on.

What is a robot?

When we think about robots, we often think of something out of a science fiction film or book. But real robots can be very simple machines built to perform a task.

A robot is just a computer that can perform a series of complex tasks automatically. Robots use a central computer to process information, as well as input and output devices to react and to carry out tasks.

You may have robots in your home right now.

Find out more about robotics, sensors and motors.

How many different types of robots are there?

There are many different types of robots. Most are designed to complete a specific task.

Here are some examples:

▪ A robot vacuum cleaner that moves around your home avoiding obstacles and cleaning the floor.

▪ A toy robot that responds to the commands that you give it. Toy robots can be programmed to move around and avoid obstacles.

▪ A robot that constructs cars and machinery. Construction robots can repeat the same tasks again and again without getting bored or tired.

▪ A robot that explores the surface of another planet. These robots can be programmed or controlled to perform experiments and navigate around their surroundings.

▪ A drone (an unmanned aircraft) can have cameras attached so it can be used to observe places that are difficult to get to. It will respond to commands given to it.

How many robots do you think you use each week?

How do we control robots?

Robots are controlled through programming. Depending on the type of programming different tasks can be achieved.

Autonomous robots

Some robots are programmed to be autonomous which means that they can function independently. They will follow their program and don’t need humans to keep telling them what to do.

Semi-autonomous robots

Some robots are semi-autonomous which means that while they can do a lot independently, they still need to be given instructions by humans from time to time.


Remote-controlled robots are programmed to respond to inputs. But the robot is not making decisions, it is just doing what it's told. Some will have controllers like a remote-controlled car or helicopter. Others will respond to inputs though a keyboard.

Pressing forward on the remote control will tell the car to move forward.
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