Chapter 1: Understanding Robots
It is the last period of the day, and your teacher plays a short video. On the screen, a long orange arm swings across a car factory floor. It lifts a door, turns it, and fixes it neatly to the car body. Then it does the same thing again. And again. Nobody is holding it. Nobody is pushing it.
A student at the back says, “That is just a big machine.”
It is a fair thing to say. Your home is full of machines. The washing machine spins clothes clean. The mixer grinds masala. The ceiling fan turns all afternoon without complaining. Each one does work for you, and none of them gets tired.
So what is different about the orange arm in the factory? Look closely at it in Fig. 1.0-1. Near its wrist sit small sensors and a camera. On Monday it can be told to fit doors. On Tuesday the same arm can be given fresh instructions and told to fit windscreens instead. Your washing machine cannot be talked into doing that.
That small difference is where this chapter begins.
Diagram
Fig. 1.0-1 – photo of an industrial robotic arm working on a car assembly line, with the gripper at the end of the arm and the joints along its length clearly visible
By the end of this chapter, you will be able to answer each of these five questions for yourself.
1.1 Machines in Everyday Life
Grinding masala on a stone slab takes strong arms and a long time. A mixer does the same job in half a minute. Nothing magical has happened here. The work is the same work — someone has simply built a device that does it faster and with less effort from you.
That device is a machine. A machine is anything built by people to do a particular job, using parts that move, or carry electricity, or both. It saves your effort, saves your time, or does the job more neatly than your hands could.
Look around a normal house and you will find dozens of them. A pair of scissors cuts paper. A bicycle carries you further than walking would. A pressure cooker holds steam so that dal cooks quickly. A washing machine spins clothes clean. A calculator adds long columns of numbers without slipping.
What a machine is made of
Machines are not all made of the same stuff. Some are purely mechanical — they have parts that push, pull, turn or slide against one another. Gears, levers, wheels, springs and pulleys belong to this group. A hand pump at a village tap has nothing electrical in it at all, yet it is certainly a machine.
Other machines add electrical parts. A motor turns electricity into movement. A heating coil turns electricity into warmth. A switch lets current through or blocks it.
And some machines carry a third kind of part: a tiny computing part that follows instructions. The washing machine that runs a fixed wash-rinse-spin cycle has a small computing chip inside it deciding when to move to the next step.
So the honest answer is that a machine can be made of metal and gears, or of wires and motors, or of both together, with a small computer added on top. What makes it a machine is not the material. It is the fact that a person designed it to do a job.
From very simple to very complex
Machines sit on a long scale. At one end are the simplest ones — a lever, a pulley, an inclined plane. These have one or two moving parts and no electricity. At the other end are large, complicated systems such as an industrial robotic arm, which has many motors, many joints and a computer running it. Fig. 1.1-1 shows this range.
Diagram
Fig. 1.1-1 – four machines drawn in a row from simplest to most complex: a pulley on a well, a bicycle, a washing machine, and an industrial robotic arm. Label each with the kinds of parts it contains: “mechanical parts only”, “mechanical parts only”, “mechanical + electrical + a small computing part”, “mechanical + electrical + a full computer”
Some machines also carry out part of their work by themselves once you have started them. You pour in the clothes, press the button, and the washing machine finishes the rest of the cycle on its own. Doing a job by itself, without a person guiding every step, is called automation. A machine can have a little automation, a lot of it, or none at all.
What a machine cannot do
Here is the important limit. A machine does exactly the job it was built for, and only that job. It does not check whether the job still makes sense.
Switch on a washing machine with an empty drum and it will run the full cycle happily, rinsing nothing. Leave a ceiling fan on in an empty room and it will keep turning until someone switches it off. The machine has no way of noticing what is going on around it, so it cannot change its behaviour to suit the situation.
Keep this limit in mind. In the next section you will meet a kind of machine that was built specially to get around it.
1.2 What Is a Robot?
The last section ended with a problem. A fan keeps turning in an empty room. A washing machine keeps rinsing an empty drum. The machine cannot tell what is happening around it, so it cannot change what it is doing.
Now think of the street light outside your school. It comes on when the evening gets dark and goes off when the sun rises. Nobody climbs a pole twice a day to flick a switch. Something inside that light is measuring how bright the surroundings are, and switching the lamp on or off to match.
That is a small step in a very useful direction. The device is no longer blind to the world outside it.
Three parts, working together
Push this idea further. Suppose you want a device that can move around a room and clean the floor without bumping into the sofa. What would it need?
First, it needs a way to find out what is in front of it. Second, it needs a way to work out what to do about it. Third, it needs a way to actually move. Miss out any one of the three and the device is stuck.
A robot is a machine built with all three of these. It has one or more sensors to take in information about its surroundings, a small computer to work out the response, and motors or similar parts to carry that response out.
A sensor is a part that measures something about the world — light, distance, temperature, touch — and turns that measurement into an electrical signal the computer can read. An actuator is the opposite: it takes an electrical signal and turns it into physical movement or some other physical effect. A motor that spins a wheel is an actuator. So is a small servo motor that lifts a lid.
Between the two sits the controller — the computing part that holds the robot’s instructions, reads the sensor signals, and sends signals out to the actuators.
You can see this cycle laid out in Fig. 1.2-1.
Diagram
Fig. 1.2-1 – a circular block diagram with three boxes joined by arrows going clockwise: “Sensors – measure the surroundings”, “Controller – matches the reading to an instruction”, “Actuators – produce movement”. A dashed arrow labelled “the world changes” runs from the Actuators box back to the Sensors box
Robots come in many shapes
The word “robot” does not describe one shape. A robotic arm bolted to a factory floor is a robot and never goes anywhere. A floor-cleaning robot is a flat disc on wheels. A drone flies. A humanoid robot is built with a head, two arms and two legs so that it can work in spaces made for people.
What they share is not their body. It is the sense–decide–act cycle running inside all of them.
One honest limit
It is easy to look at a robot avoiding a chair and say it understood that the chair was in the way. It did not. Its distance sensor returned a small number, its instructions said that a small number means turn, and it turned.
That distinction matters. A robot carries out the instructions a person wrote for it, quickly and without getting bored. It has no sense of what the task is for, and it will follow a badly written instruction just as faithfully as a good one.
1.3 Characteristics of Robots
You now know what a robot does. The next question is a fair one: if someone hands you a device, how do you decide whether to call it a robot?
There is no single test. Instead, engineers look for a set of qualities that robots tend to have. Some robots show all of them. Many show only a few. Fig. 1.3-1 shows where several of these qualities sit on an ordinary wheeled robot.
Diagram
Fig. 1.3-1 – a labelled sketch of a small wheeled robot on a table, with callout lines to: the distance sensor at the front (labelled “senses – supports autonomy”), the wheels and their motors (labelled “mobility”), the circuit board on top (labelled “programmability – instructions stored here”), and a red button on the body (labelled “emergency stop – safety”)
The six qualities
Programmability. A robot’s behaviour is stored as instructions, not built into its metal. Change the instructions and the same robot does a different job. The little wheeled robot in your school lab can be told on one day to follow a black line on the floor, and on the next day to wander freely and turn away from walls. Nothing about its body changes. Only the instructions do.
Autonomy. This is the ability to carry on with a task without a person guiding every step. A robot gets it from its sensors: because it can measure its surroundings, it can pick its own next move from the choices its instructions allow. Autonomy comes in degrees. A floor-cleaning robot is largely autonomous once you press start. A surgical robot is semi-autonomous — a surgeon controls it, and the robot holds the instrument steadier than a human hand can.
Learning and adaptation. A few robots go one step further. They keep a record of how earlier attempts went and use that record to adjust what they do next time. This is the idea behind machine learning, a method in which a computer improves its performance at a task by finding patterns in data rather than being given every rule by hand. You will study it properly in the Artificial Intelligence part of this course. Be careful not to assume every robot learns. Most of the robots you will build in school do not — they simply follow the same fixed instructions each time.
Precision and repetition. A robot can place a part in the same spot, to the same small fraction of a millimetre, ten thousand times in a row. It does not get tired, distracted, or bored at four in the afternoon. This is exactly why factories that assemble circuit boards or weld car bodies use them. Precision means how closely the actual result matches the intended one.
Mobility. Many robots can move themselves from place to place. Mobility is that ability to travel through the surroundings. It can be simple, as with wheels on a flat floor, or complicated — walking on legs over uneven ground, crawling through a pipe, flying, or swimming. Not every robot has it. A robotic arm bolted to a factory floor cannot go anywhere, and it does not need to.
Safety features. Because robots move heavy parts quickly, they are built with features that limit the damage when something goes wrong. Collision sensors let the robot stop when it touches something unexpected. A large emergency stop button cuts power at once. Some arms are designed to stop pushing the moment they meet more resistance than expected, so that a person standing in the wrong place is nudged rather than crushed.
1.4 How a Robot Differs from an Ordinary Machine
Walk into a hospital and the glass door slides open before you touch it. Something above the frame notices that a person has come close, and a motor pulls the door aside. Sensing, then acting — the same pair of steps you met in Section 1.2.
So is that door a robot?
People argue about questions like this, usually because they are using the two words loosely. In everyday talk, anything that moves by itself gets called a robot, and anything with a plug gets called a machine. That is fine at a bus stop. It is not good enough in a robotics class, where the difference decides what you can expect a device to do.
The two words are not opposites. A robot is a machine — it is built of the same kinds of parts, and it exists for the same reason, to do a job for people. What sets it apart is a particular bundle of qualities that ordinary machines do not carry.
The next two sections settle the matter. First you will compare robots and machines point by point. Then you will look at the statement that sums the whole thing up: all robots are machines, but all machines are not robots. The sliding door will get its answer along the way.
1.4.1 Comparing Robots and Machines
The easiest way to see the difference is to put two real devices side by side and watch how each one behaves. Take an electric kettle in a staff room, and a warehouse robot that drives under a loaded shelf, lifts it, and carries it across the floor to a packing counter. Both are machines. Only one of them is a robot.
Four points of difference
How much a person is needed. Somebody must fill the kettle, place it on its base and press the switch. Every time. The kettle contributes nothing until a person acts. The warehouse robot is told once which shelf is wanted, and then finds its own way there and back. A person sets the goal; the robot handles the steps in between.
How many different jobs it can do. The kettle boils water. That is the whole list, and it will be the whole list for as long as the kettle lasts. The warehouse robot can fetch a shelf today, and tomorrow be sent to carry a different kind of load along a different route.
How easily the job can be changed. To make the kettle do something else, you would have to take it apart and build a different device. The robot’s behaviour lives in its instructions, so the same body does the new job once the instructions are rewritten. This is programmability doing its work.
How much it notices. Machines are not always blind. A kettle has a small sensor that measures the temperature of the water and cuts the power when it boils, and an electric iron has one that keeps the plate near the setting you chose. But those readings control one fixed thing and nothing else. A robot’s sensors feed a computer that chooses between many possible actions — go forward, stop, turn, lift, wait.
Table 1.1 collects these four differences in one place.
The line is not razor sharp
Do not expect every device to fall cleanly on one side. Devices exist all along the range between the kettle and the warehouse robot, and engineers disagree about where exactly to draw the line.
A modern washing machine senses the weight of the load and adjusts how much water it draws. That is more than a kettle does, and less than a robot does. It is usually called an automatic machine rather than a robot, because it cannot be given a new job and never moves itself anywhere.
1.4.2 All Robots Are Machines, but All Machines Are Not Robots
Read the two halves of that sentence separately. Each one says something different, and both are true.
The first half is easy once you look at what a robot is made of. It has a body of metal or plastic, motors, wires and a power supply. People designed it and built it to do a job for them. That is the description of a machine, word for word. Nothing about a robot places it outside the family of machines, so every robot is one.
The second half is just as easy from the other side. A crowbar, a bicycle chain, a table fan and a pressure cooker are all machines, and not one of them senses its surroundings or can be given fresh instructions. So the family of machines is much larger than the group of robots inside it.
Fig. 1.4-1 shows the arrangement.
Diagram
Fig. 1.4-1 – two circles, one inside the other. The large outer circle is labelled “Machines” and holds small drawings of a lever, a bicycle, an electric kettle and a ceiling fan. The smaller circle drawn inside it is labelled “Robots” and holds a robotic arm, a wheeled robot and a drone. A caption arrow points to the space between the two circles and reads “machines that are not robots”
Robots are a special group within machines — the group whose members can be programmed and can act on what their sensors report. Adding those qualities does not stop a robot from being a machine, any more than being a mango stops something from being a fruit.
A three-question test
You can settle most arguments with three questions asked in order.
Two devices put to the test
Return to the hospital’s sliding door from Section 1.4. It fails at the very first question: there is no way to tell that door to do a different job. It also fails the third — the sensor triggers one fixed response, opening the door, and nothing else. It is an automatic machine, and a very useful one, but it is not a robot.
Now try a laptop. It passes the first question easily, since installing new software gives it new work to do. It even passes the second, because it has a camera and a touchpad. But it fails the third in a different way: it has no actuators, so whatever it works out stays on the screen and never becomes movement in the world. A laptop is a programmable machine, not a robot.
1.5 Benefits of Using Robots
Robots are expensive to buy and troublesome to set up. Nobody installs one for fun. They are installed because, for certain kinds of work, a robot does something a person cannot — or should not have to.
The benefits below are always measured with respect to humans doing the same work. Keep that comparison in mind as you read each one.
Increased quality. A robot repeats the same movement the same way every time. In a workshop that welds steel frames, that means every joint gets the same heat for the same length of time, so the frames come out alike and fewer of them have to be thrown away. A skilled worker can match this for an hour. Matching it for the four hundredth frame of the day is much harder.
Increased productivity. Productivity means how much work gets finished in a given time. A robot arm moves quickly and does not pause between pieces, so more items come off the line each hour than would otherwise.
Increased efficiency. Efficiency is about how much you get out for what you put in. Because a robot places material exactly where it is meant to go, less paint is sprayed onto the floor, fewer sheets are cut wrongly, and less electricity is spent redoing spoiled work. Same input, more useful output.
Longer working span. People need sleep, meals and rest, and their accuracy drops when they are tired. A robot can run through the night and through a second shift, stopping only for maintenance. This is the benefit factories value most when demand is high.
Working in hazardous environments. Some places are simply not safe for a human body. Inside a furnace, beside a chemical spill, deep underwater, in a mine after a collapse, or near a suspicious package that may explode — a robot can be sent in and, at worst, be lost. A person cannot.
Improved workplace. When robots take over the lifting, the fumes and the endless repetition, the humans on that floor stop doing the work that injures backs and dulls attention. They move to setting up the machines, checking quality and solving problems when something goes wrong.
Putting a number on the gain
Benefits are easier to judge when you work them out rather than argue about them. The number of items finished in a day is simply
\[\text{items per day} = \text{items per hour} \times \text{hours worked per day}\]
where “items per hour” is the rate at which the work is done, and “hours worked per day” is the time the worker or robot is actually running.
Notice where the gain came from. The robot is only one and a half times faster per hour, yet it finishes five times as much work. Most of the difference is the longer working span, not the speed. Fig. 1.5-1 shows the two totals side by side.
Diagram
Fig. 1.5-1 – a simple bar chart with two bars. Left bar labelled “Worker” reaching 240; right bar labelled “Robot” reaching 1200. The vertical axis is labelled “cartons packed per day” with marks at 0, 400, 800 and 1200
Where the safety benefit really counts
Of all six benefits, the fifth is the one that decides matters of life and death. Fig. 1.5-2 shows a bomb-disposal robot, driven by an operator standing at a safe distance, examining a package that a person would otherwise have had to approach.
Diagram
Fig. 1.5-2 – photo of a tracked bomb-disposal robot with an extended arm and camera, examining a bag on open ground
The same reasoning sends robots into places people cannot survive at all: pipelines on the sea bed, damaged nuclear plants, and the surface of other planets.
1.6 Limitations of Using Robots
After a list of benefits like the one in Section 1.5, it is tempting to conclude that a robot should be put on every job. Look at the tea stall near your school and you will see why that is wrong. The work changes every few minutes, the customers stand wherever they like, and the whole business earns less in a month than a robot arm costs. A robot would be useless there, and the owner knows it without being told.
Robots have real limits. Here are the ones that matter most.
What holds robots back
High initial cost. The price on the robot is only part of it. Somebody must also pay for the safety fencing, the wiring, the mounting, the software and the training. All of this is spent before the robot has done a single hour of useful work.
Complexity. Setting up and programming a robot needs trained people. So does keeping it running. When a robot stops with a fault at midnight, the person on duty usually cannot fix it, and the line stands still until a technician arrives.
Job displacement. When a machine takes over a task, the people who used to do that task lose that work. Some are retrained for other roles. Others are not, and for them the change is a hard one.
Security concerns. Modern robots are often connected to a factory network or to the internet so that they can be monitored from an office. Anything connected can be attacked. A robot that is broken into could be stopped, damaged, or made to move in an unsafe way, and the records it stores could be stolen.
No creativity, and no handling of the unexpected. A robot follows the instructions it has. Give it a situation nobody planned for — a part lying at an odd angle, a fallen box, a power cut halfway through a movement — and it has no way to improvise. A human worker glances at the mess and works something out.
Dependency on technology. Once a workplace hands a task over completely, it has no fallback. If the system fails, the work does not slow down; it stops. Over the years the people there also lose the practice of doing that task by hand.
Counting the cost before buying
The first limitation can be tested with arithmetic rather than argument. A common check is the payback time — how long the robot must work before the money it saves adds up to what it cost:
\[\text{payback time in months} = \dfrac{\text{cost of the robot}}{\text{money saved each month}}\]
Here “cost of the robot” is everything spent to get it working, and “money saved each month” is how much less the work costs once it is running.
Fig. 1.6-1 shows the same result as a picture.
Diagram
Fig. 1.6-1 – a line graph with months from 0 to 48 along the horizontal axis and rupees from 0 to 7,20,000 along the vertical axis. A flat horizontal line at 6,00,000 is labelled “amount spent”. A straight line rising from the origin is labelled “money saved so far”. The two lines meet at 40 months, marked with a dot and the label “payback”
This is why the tea stall owner is right. A saving of ₹15,000 a month makes the sums work. A saving of ₹500 a month would push the payback time past sixty years, and no machine lasts that long.
1.7 Summary
- A machine is a device made of mechanical, electrical or computing parts, built by people to carry out one particular task or a fixed set of tasks. It need not be made of metal and gears.
- Machines range from very simple ones, such as a lever or a pulley, to very complex ones with motors and a computer inside.
- Automation means a machine carrying out part of its work by itself, without a person guiding every step.
- An ordinary machine cannot tell what is happening around it, so it goes on doing the same thing whether or not it still makes sense.
- A robot is a programmable machine that senses its surroundings, works out a response from its stored instructions, and acts on that response using motors or other actuators.
- A sensor measures something about the world and turns it into an electrical signal. An actuator turns an electrical signal into movement. The controller holds the instructions and joins the two.
- Every robot runs a sense–decide–act cycle: read the sensors, match the reading to an instruction, drive the actuators, and repeat.
- Robots are described by six characteristics: programmability, autonomy, learning and adaptation, precision and repetition, mobility, and safety features.
- Programmability and autonomy are essential. Learning, high precision, mobility and safety features are common but not present in every robot.
- Robots differ from ordinary machines in how much a person is needed, how many different jobs they can do, how easily the job can be changed, and how far sensor readings are used to choose actions.
- All robots are machines, but all machines are not robots. Robots are a smaller group inside the larger family of machines.
- A device can be tested with three questions: can it be given new instructions, does it sense its surroundings, and does it use those readings to choose among different actions.
- The benefits of using robots, compared with humans doing the same work, are increased quality, increased productivity, increased efficiency, longer working span, working in hazardous environments, and improved workplace.
- The limitations of using robots are high initial cost, complexity, job displacement, security concerns, lack of creativity when something unexpected happens, and dependency on technology.
- Whether a robot is worth installing can be checked by arithmetic — for example, by working out how long it takes for the money saved to add up to what the robot cost.
- Automating a task affects the people who used to do it, so a responsible workplace plans retraining and gives notice before making the change.
1.8 Key Terms
- Actuator — a part that turns an electrical signal into movement or some other physical effect, such as a motor that spins a wheel.
- Automation — a machine carrying out part or all of its work by itself, without a person guiding every step.
- Autonomy — a robot’s ability to continue a task on its own, using its sensor readings to pick its next action instead of waiting for instructions from a person.
- Controller — the computing part of a robot that stores its instructions, reads the sensor signals, and sends signals out to the actuators.
- Machine — a device made of mechanical, electrical or computing parts, built by people to carry out one particular task or a fixed set of tasks.
- Machine learning — a method in which a computer improves its performance at a task by finding patterns in data, rather than being given every rule by hand.
- Mobility — a robot’s ability to move itself from place to place, by wheels, legs, propellers or other means.
- Precision — how closely the result a robot produces matches the result it was meant to produce.
- Programmability — the quality of having behaviour stored as instructions, so that new instructions make the same device do a different job.
- Robot — a programmable machine that senses its surroundings, works out a response from its stored instructions, and acts on that response using actuators, with little or no help from a person while it works.
- Sensor — a part that measures something about the surroundings, such as light, distance, temperature or touch, and turns that measurement into an electrical signal.
1.9 Objective Questions
A part that measures something about the surroundings and turns it into an electrical signal is called a ______.
Which one of the following is an actuator?
- A distance sensor fitted at the front of a robot
- A motor that turns a wheel
- A battery that supplies power
- A light bulb switch on the wall
State whether the following is true or false: every robot must be able to move itself from one place to another.
Which one of the following is not a benefit of using robots?
- Increased quality
- Longer working span
- High initial cost
- Working in hazardous environments
Name the cycle that a robot repeats over and over from the moment it is switched on until it is switched off.
Match each item in Column A with its meaning in Column B.
Column A Column B a. Sensor i. Turns an electrical signal into movement b. Actuator ii. Doing part of a job without a person guiding every step c. Controller iii. Measures something about the surroundings d. Automation iv. Stores the instructions and selects the action A packing robot in a workshop packs 30 cartons every hour and runs for 18 hours a day. How many cartons does it pack in one day?
1.10 Concept Questions
Define a robot, and name the three kinds of parts that every robot must have.
The glass door of a hospital slides open when a person comes near it. Give a reason why this door is not called a robot.
Write any three differences between an ordinary machine and a robot.
Explain what programmability means. Use the example of a small wheeled robot in a school lab that is used for two different tasks on two different days.
A robot arm on a packing line comes across a carton lying at an odd angle, a situation its instructions do not cover. Explain what the arm will do, and why a factory therefore keeps human workers on the floor.
A workshop buys a labelling robot. Buying and installing it costs ₹4,50,000 in total, and after it starts running the workshop’s monthly costs fall by ₹18,000. Work out how long the robot takes to pay for itself. Show your working, and write the answer in months.
1.11 Case-Based Questions
- A small dairy near a town packs milk pouches into crates. At present a worker does this by hand. The owner is thinking of buying a packing robot instead. The rates and working hours of the two are shown in Table 1.2.
- Work out how many crates the worker packs in a day and how many the robot packs in a day.
- How many more crates does the robot pack in a day than the worker?
- The robot packs only a little faster each hour, yet finishes far more work in a day. Name the benefit of using robots that explains most of this difference, and say why.
A grocery shop in a market has an electronic weighing scale at the counter and a shutter that rolls up when the owner presses a button on a remote. The owner has now been offered a floor-cleaning robot for the shop.
- Apply the three-question test to the weighing scale and to the shutter. For each device, say at which question it stops.
- The owner says, “My shutter opens without anyone touching it, so it is a robot.” Do you agree? Give one reason for your answer.
- Name two limitations of using robots that the owner should think about before buying the floor-cleaning robot.