By the end of this lesson you will be able to
- name the six main parts of a humanoid robot and say what job each one does
- say which of three worlds (mechanical, electrical or information) a part belongs to, and why a fault can cross from one world to another
- describe Bramble, the demonstration robot used in every lesson, and the idea of a data sheet
- explain what this course teaches, how its lessons work, and what it does not do
Welcome to the Ashdown Robotics Workshop
In this course you play the part of Eleanor Price, a new technician at the Ashdown Robotics Workshop. The workshop looks after humanoid robots: machines with a body shaped roughly like ours, with a head, a torso, two arms and two legs. Your job is to keep them working and, before that, to understand how they work.
You will meet these people as the lessons go on:
| Who | Role | What they do for you |
|---|---|---|
| Henry Wren | Senior technician | Your mentor. He hands you the day's small jobs and explains what he expects you to work out. |
| Margaret Ellis | Workshop manager | Sets the workshop rules, especially on safety, and signs off the work. |
| Oliver Grant | Operator | Works with the robot every day and reports what it does, in his own words. |
| Alice Bennett | Museum curator | Owns the small museum where the robot works as a guide, and cares that it is reliable. |
| Thomas Hale | Previous technician | Has left the workshop, but left notes that you sometimes read. They are useful, and not always complete. |
Meet Bramble
Every lesson uses one robot as its example. It is called Bramble: model HR-7, serial number HR7-0412. Bramble is a demonstration humanoid that guides visitors round Alice's museum, and Oliver looks after it during the day. It is 1.6 m tall and has a mass of 70 kg, of which 6 kg is its battery.
Bramble is a made-up robot. That is deliberate: it means every number in this course is the same for everyone, and nothing here describes a real product. The ideas, however, are true for electrically powered humanoid robots in general.
Bramble comes with a data sheet: a page of facts and figures about the machine, such as its size, the strength of each motor and the capacity of its battery. A real technician reads the data sheet before touching anything, because it says what the machine should do. When a lesson needs a number about Bramble, the number comes from its data sheet.
The body plan
A humanoid robot moves by bending at joints. A joint is a place where two parts of the body can move relative to each other, like your knee or your elbow. Bramble has 17 of them: 2 in the neck, 1 in the waist, and one on each side (so 2 in all) at the shoulders, elbows, wrists, hands, hips, knees and ankles. Add them up: 2 + 1 + 2 + 2 + 2 + 2 + 2 + 2 + 2 = 17.
The picture shows where the main parts sit. Do not worry about remembering it yet. The rest of the course looks at every part in turn.
The six main parts
Every humanoid robot, whatever its size, is built from six kinds of part. Each has a job, and a comparison with a human body helps to see it. Treat the comparison as a picture only: a robot is not a person, and the parts do not behave in exactly the same way.
- Frame. The frame is the rigid structure of the robot: the metal or plastic parts that hold everything in place and carry the weight down to the feet. It is like a skeleton.
- Actuators. An actuator is a part that makes something move. In Bramble, each actuator is a motor (a machine that turns electrical energy into turning) joined to a gearbox (a set of gears that slows the turning and makes it stronger). One sits at each joint. They are like muscles.
- Sensors. A sensor measures something and reports it as an electrical signal. Bramble has an encoder on each motor that reports how far it has turned, a balance sensor in the torso that reports tilt and turning, four force sensors in each foot, two cameras and one microphone. Sensors are like eyes, ears, touch and the balance organs of the inner ear.
- Controller. The controller is the robot's set of computers: a main computer, plus a small motor-driver board at each joint that passes the main computer's orders to its motor. It reads the sensors and decides what every actuator should do next. It is like a brain and spinal cord.
- Battery. The battery stores the energy the robot runs on. Bramble's is a pack of 12 lithium-ion cells, and it holds about 888 Wh, the unit you will meet in Lesson 1.2. It is like a fuel tank.
- Wiring. Wiring carries electricity and information between the parts. There are heavy wires that carry power from the battery to the motors, and thin wires that carry signals. Signals travel along buses: shared cables that many parts use to talk to the controller. Bramble has four, named a to d. Wiring is like blood vessels and nerves together.
| Part | Its job | Everyday picture | In Bramble |
|---|---|---|---|
| Frame | Holds the shape and carries loads | Skeleton | The structure of the whole 1.6 m body |
| Actuators | Make the joints move | Muscles | A motor and a gearbox at each of 17 joints |
| Sensors | Measure and report | Eyes, ears, touch, inner ear | Encoders, balance sensor, foot sensors, cameras, microphone |
| Controller | Decides what to do next | Brain | One main computer and a driver board at each joint |
| Battery | Stores the energy | Fuel tank | 12 lithium-ion cells, 6 kg |
| Wiring | Carries power and signals | Blood vessels and nerves | Power wires and four buses, a to d |
Three worlds
To think clearly about a machine as varied as a robot, it helps to sort its parts into three worlds.
- The mechanical world is about forces, movement and material: the frame, the gearboxes, the bearings and the joints.
- The electrical world is about carrying and using electrical energy: the battery, the power wiring, the motor-driver boards and the motors.
- The information world is about measuring, deciding and communicating: the sensors, the controller and the buses.
Some parts stand on the border. A motor turns electrical energy into mechanical movement. An encoder turns mechanical movement into information. A driver board turns an order (information) into power for the motor (electrical). Follow one movement through the robot and you cross all three worlds, as the picture shows.
The reason this matters for a technician is that a symptom shows up in one world while its cause may sit in another. Suppose Oliver says that Bramble's elbow feels weak. The cause could be mechanical (a worn or dry gearbox), electrical (a supply that has sagged, so the motor gets less power than it should) or in the information world (the controller is holding back because it has been given a wrong reading). If you know all three worlds, you can list the possibilities and choose a test that separates them. That is the skill this course builds.
The course is arranged to follow the worlds. It starts with mechanics, then electricity, then motors, which join the two, then sensors, power, and the controller and its wiring. It finishes by putting everything together on Bramble.
What a technician must understand, and why
Three reasons run through every lesson.
- To find faults. You cannot notice that something is wrong unless you know what right looks like. If you know a knee should turn at a certain speed with a certain strength, a slow or weak knee stands out.
- To choose the right test. There are dozens of things you could check on a robot. Understanding tells you which check answers the question in one step, instead of ten.
- To stay safe. A humanoid robot has heavy moving limbs, a battery that stores a lot of energy, and motors that get hot. Lesson 1.3 is about working safely, and safety comes before every other skill.
Common mistake: changing parts until the fault goes away
When a robot misbehaves, it is tempting to swap the part that seems most likely. This costs money and time, and it can hide the real cause, so the fault returns. Understanding first, then a test, then a repair, is faster in the end.
How the course is laid out
The course has 9 modules and 37 lessons. Each module builds on the ones before it.
| Module | Title | Lessons | What it lets you understand |
|---|---|---|---|
| 1 | Getting Started | 1.1 to 1.4 | The parts of a robot, units and estimating, safety, and the tools you measure with |
| 2 | Mechanics | 2.1 to 2.5 | Forces, torque, gears, backlash, bearings and friction |
| 3 | Electricity | 3.1 to 3.5 | Voltage, current, resistance, power, circuits and the multimeter |
| 4 | Motors and Actuators | 4.1 to 4.5 | How a motor works, drive electronics, heat, and brakes |
| 5 | Sensors | 5.1 to 5.5 | Encoders, balance sensors, force sensors, temperature and current sensing, cameras |
| 6 | Power Systems | 6.1 to 6.4 | Battery cells and packs, battery safety, charging, fuses and wire sizes |
| 7 | Controllers and Wiring | 7.1 to 7.4 | The controller, buses, connectors and cables, noise and grounding |
| 8 | Structure and Environment | 8.1 to 8.3 | Frames and fasteners, cooling, dust, moisture, vibration and fatigue |
| 9 | Putting It Together | 9.1 to 9.2 | Tracing a symptom to a component, and a final hardware audit of Bramble |
How each lesson works
From Lesson 1.2 onwards, every lesson opens with a job card: a short work order from Henry, Margaret, Oliver or Alice that shows why the lesson matters. Then come short explanations with diagrams. Several lessons include an explorer, which is a small live tool: you move sliders and watch the results change, so that you can see how a formula behaves instead of only reading it.
Each lesson then gives you five exercises, with numbers to work out, choices to make, steps to put in order, or items to match. Every exercise is checked for you. If you are stuck you can ask for a hint or for the worked answer. A four-question quiz and a short summary close the lesson.
This first lesson has no exercises. It sets the scene for everything that follows.
What this course is, and what it is not
This course teaches understanding: the physics and hardware ideas behind a robot, and the habit of reasoning from a symptom to a cause. It does not qualify anyone to work on a real robot. A real robot has its own maker's service manual and training, and both come first. Where the course describes a hands-on step, it does so to explain an idea, and the maker's instructions and your workshop's rules always take precedence over anything you read here.
There is a companion course, Humanoid Robot Maintenance: Diagnostics and Fault-Finding, which uses a practice service console. It teaches the reading of logs and the method of fault-finding. This course gives you the hardware understanding that makes that one easier.
Lesson 1.2 is next. It gives you the language of numbers and units that every later lesson depends on.
Quick check
Four questions to confirm the main ideas. Choose an answer to see the explanation.
Which of these is an actuator in Bramble?
An actuator is a part that makes something move, and in Bramble that means a motor with its gearbox at a joint. A camera is a sensor, the frame is structure, and a bus carries signals.
An encoder on a motor shaft reports how far the shaft has turned. In terms of the three worlds, what is it doing?
A sensor changes something physical, here a turning shaft, into a signal the controller can read. It does not move anything itself, and it stores nothing.
Oliver reports that Bramble's elbow feels weak. What is the sound way to begin?
A weak joint could come from a worn gearbox, a low supply or a wrong reading, so you list the possibilities across all three worlds and choose a test that separates them. Swapping a part on a guess may hide the real cause.
What does this course promise, and what does it not?
The course builds understanding so that you can follow a manual and reason about faults. The maker's manual and training always come first, and no course of this kind makes someone qualified to work on a real robot.
Summary
- A humanoid robot has six main kinds of part: frame, actuators, sensors, controller, battery and wiring.
- An actuator is a motor with a gearbox at a joint. Bramble has 17 joints, and so 17 actuators.
- Parts belong to three worlds: mechanical, electrical and information. A symptom in one world can have its cause in another.
- A technician needs understanding to find faults, to choose the right test and to stay safe.
- Bramble is a made-up robot whose data sheet supplies the numbers for this course. The maker's manual and workshop rules always come first.
Found a mistake on this page, or something unclear? Report a problem and mention “Hardware Lesson 1.1”.