Representing position in binary
We have seen how binary can be used to represent documents, pictures and sounds but binary numbers and codes can also be used to represent position. A classic application of using binary to control position is with computer controlled robots. According to the British Computing Society's "A Glossary of Computing Terms", a robot is "a computer-controlled mechanical device which is sufficiently flexible to be able to do a variety of tasks". Robots are used extensively, including for welding, painting cars, assembling parts of machines, shearing sheep, packing and unpacking boxes, in warehouses to collect items, space exploration, deep sea exploration, picking fruit, bomb disposal, surgery, maintenance in nuclear reactors, assembling complete houses, building circuit boards, exploring volcanoes and so on!
What is a robot?
The word ‘robot’ comes from the Czech word ‘robotnik’ meaning ‘worker’ and was coined for English use in the early 20th century. Robots are essentially computer controlled mechanical devices that are based on the human arm. The arms often have ‘joints’, a little bit like elbow joints, to allow greater flexibility. These are positioned using computer-controlled motors (known as ‘actuators’), the computer calculating the correct position for the arm. Sometimes, the joints have a sensor. The sensor ‘feeds back’ to the computer what angle a joint is actually at and the computer compares that with what angle it wants the joint to get to. It then uses the motor to adjust the joint position and the process of ‘feedback’ is repeated. Robots usually have a specialised ‘hand’ or gripper on the end of the arms that can be designed for carrying out different jobs. The grippers can also be controlled by actuators but pneumatics and hydraulics can be used as well.
They are usually designed to perform a task over and over again with great accuracy and speed and they have the ability to react with their environment; when the environment in which the robot is operating changes, the robot’s behaviour changes. Some robots are static. They are fixed in one place. Others have the ability to roam around!
A typical robot will be made up of sensors, actuators and a computer. The computer’s job is to read the data from the sensors, make sense of it and then operate the actuators as appropriate.
Degrees of freedom
If we examine the human arm for a moment, we can see the movement it provides us with is quite complex. At the elbow, you can move your lower arm up and down. The wrist can be rotated, moved up and down and also left and right. Each finger is complex, being made up of more joints that provide more opportunities for movement. Each of the ways of movement at any particular joint is known as a 'degree of freedom'. So the elbow has one degree of freedom, the wrist three and so on. The more degrees of freedom in a system, the more complex the movement that can be achieved. The human arm has many degrees of freedom indeed and so we can manipulate objects easily. When you look at a robot, one of the key features to take note of is how many degrees of freedom it has. The more degrees of freedom it has, the more complex the robot. Each degree of freedom can have a sensor that 'reads' where it is. You can have a sensor for up and down, one for left and right and one for rotation, for example. These sensors can be read by a computer and converted into numbers that represent exactly where the robot is.
Advantages and disadvantages of robots
1. Robots are extremely expensive to buy. They also need highly skilled (and expensive) people to reprogram them to do different things.
2. Robots should produce financial benefits because you don't have to pay a salary (amongst the other reasons listed below) but these benefits are not usually felt for a number of years.
3. The quality of work produced by robots may be higher than with humans. For example, spot welding can be done to much finer tolerances. Perhaps more importantly, however, the work done by robots will be done to consistent standards. With humans, mistakes can vary with how tired the employee is, the day of the week. Cars that keep breaking down are sometimes referred to as 'Friday afternoon' or 'Monday morning' cars. Mistakes may also creep in if an employee is having personal problems, for example.
4. Employees get tired easily, go sick, need breaks and have holidays. Robots can work for much of the time. They do need to stop sometimes, however, for such things as routine maintenance and system upgrades.
5. Employees need facilities that don't need to be provided for robots. These include lighting and heating, car parks and toilets, a personnel department to look after them and an accounts department to make sure they're paid!
6. Robots can be used in hazardous environments such as for bomb disposal, maintenance in nuclear reactors, space or in very deep parts of the ocean.
7. Robots provide opportunities for a higher paid, more skilled workforce, for example, programmers of robots or maintenance people. However, the workforce may be smaller. This means there will be fewer jobs available in a car factory and less unskilled or semi-skilled jobs in a community. This will have an effect on the local economy.
Q1. Define ‘robot’.
Q2. State three uses for robots. Use the Internet for research.
Q3. State the advantages to a company of using robots to assemble cars.
Q4. State the impact on employment that introducing robots onto the assembly line in a car factory might have.
Q5. What is an actuator?
Q6. A robot arm has to position a box accurately in a warehouse. What is meant by ‘feedback’?
Q7. What does a proximity switch sense?
Q8. What is meant by a degree of freedom in robots?
Q9. Use the Internet for research. Describe a medical use for nanorobots.
Q10. Use the Internet for research. Why are robots used for bomb disposal?