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Learning Lego Mindstorms EV3
Learning Lego Mindstorms EV3

Learning Lego Mindstorms EV3: Build and create interactive, sensor-based robots using your LEGO MINDSTORMS EV3 kit

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Learning Lego Mindstorms EV3

Chapter 2. Mechanical Design

In this chapter, we will build and program several models to demonstrate the basic principles of mechanical design. We will:

  • Explore the idea of mechanical advantage
  • Learn how you can increase either speed or torque using different combinations of gears
  • Build gearboxes with motors
  • Use the spur gears, beveled gears, and worm gears
  • Write a program to spin the motors a set number of rotations
  • Use the display on the EV3 brick

All of the models in this chapter can be built with both the EV3 Home Edition and EV3 Educational Edition kits.

Mechanical advantage

When designing a robot, sometimes we may want to build a fast robot that needs to get to its objective quickly. At other times, we may want a powerful robot. For instance, maybe the robot needs to push a heavy object, push another robot, or climb a steep hill. When it comes to a robotic arm, we might be trying to lift a heavy object slowly or lift a small object quickly.

However, we cannot have both speed and power. There is a trade-off here—if you increase one, you decrease the other. This trade-off is called the law of conservation of energy.

Mechanical advantage

LEGO bricks allow us to use several types of simple machines. The simplest would be the lever arm. You can easily create a lever with LEGO beams and pins. To balance a seesaw or a lever, the amount of torque or rotational force must be the same on either side of the seesaw. In the preceding image, we see a LEGO balance with unequal forces but equal lever arms. The longer the lever arm, the less force we need to rotate...

Motors

The EV3 kit comes with two large motors and one medium motor. Beyond the packaging, there are some other important differences between the large motor and the medium motor. The following list compares the features of the large and medium motor:

  • Large motor maximum speed 170 rpm
  • Medium motor maximum speed 250 rpm
  • Large motor torque when rotating 0.21 N∙m (Newton-meters is a unit used to measure torque)
  • Medium motor torque when rotating 0.08 N∙m
  • Large motor torque at standstill 0.42 N∙m
  • Medium motor torque at standstill 0.12 N∙m
  • Large motor mass is 76 grams
  • Medium motor mass is 36 grams

The large motor will be excellent to power the drive train of our robot, and if you need the extra speed, you can always gear the motors up. If you need more torque, you can gear down. The medium motor is about half the mass of the large motor. The medium motor actually spins about 50 percent faster than the large motor. The torque of the medium motor is only a fraction of the large...

Large motors and gears

We will be building a simple gear train with two gears powered by the large motor. The gears we are using are double bevel gears. Normally, when you think of a gear, you are thinking of a straight or a spur gear. The LEGO double bevel gear is essentially a spur gear in the middle, with beveled edges on both sides. Not only does this allow you to combine two double bevel gears aligned parallel to each other as we are in this section, but you can also combine them at right angles, as we will see later in this chapter. I chose this particular set of gears because they are included in both the Home Edition and Educational Edition kits. However, you could build a gear train like this using any set of dissimilar gears. The small gear has 12 teeth, and the large gear has 36 teeth. The motor will power the larger gear. We will find that every time the large gear spins once, the small gear will spin three times. So we are gaining speed, but at the cost of losing torque. This...

Writing a program

After we attach the cables, we will be ready to write a program to make the motor spin. Connect the motor to port D on your EV3 brick. Turn on your EV3 brick by pressing the dark gray button in the center of the brick.

After you start up the EV3 software, navigate to File | New Project | Program. This will start up a new program. You could easily start one of the many LEGO tutorials at this point. We will start with a blank sheet. The startup menu you see in the following screenshot is the main difference between the Home Edition version of the software and the Educational Edition. Additionally, the Home Edition does not allow you to do experiments.

Writing a program

You will see several icons at the bottom of the screen on the green Action tab of the Programming Palette. Drag a Large Motor block (encircled in red in the following screenshot) onto the Programming Canvas and place it next to the Start block.

Writing a program

Although not required, you can add a Stop block at the end of the program. You can...

Bevel gears at right angles

In the next example, we are going to build a gearbox using a 12-tooth bevel gear along with the large 36 tooth straight gear with double bevels. These gears actually rotate at right angles to each other. Since the motor drives the smaller gear, the output of our gearbox is actually slower than the motor. However, we will gain torque in this system, so we have a mechanical advantage of 3. We will be using the medium motor in this model.

Bevel gears at right angles

In the following five steps, we will build a gearbox with two gears at right angles:

  1. First attach two friction pins to the medium motor.
    Bevel gears at right angles
  2. Next, attach the open frame to the motor. The open frame is essentially our gearbox.
    Bevel gears at right angles
  3. Next, place the 8-mod axle (with stop) and the beveled gear into the medium motor. Make sure the axle fits into the motor.
    Bevel gears at right angles
  4. Now, insert the large gear and an axle into your gearbox. The teeth of both the gears should interlock.
    Bevel gears at right angles
  5. Finally, add a flag so you can see the rotations of the large gear.
    Bevel gears at right angles

Next, write this simple...

Mechanical advantage


When designing a robot, sometimes we may want to build a fast robot that needs to get to its objective quickly. At other times, we may want a powerful robot. For instance, maybe the robot needs to push a heavy object, push another robot, or climb a steep hill. When it comes to a robotic arm, we might be trying to lift a heavy object slowly or lift a small object quickly.

However, we cannot have both speed and power. There is a trade-off here—if you increase one, you decrease the other. This trade-off is called the law of conservation of energy.

LEGO bricks allow us to use several types of simple machines. The simplest would be the lever arm. You can easily create a lever with LEGO beams and pins. To balance a seesaw or a lever, the amount of torque or rotational force must be the same on either side of the seesaw. In the preceding image, we see a LEGO balance with unequal forces but equal lever arms. The longer the lever arm, the less force we need to rotate the lever...

Motors


The EV3 kit comes with two large motors and one medium motor. Beyond the packaging, there are some other important differences between the large motor and the medium motor. The following list compares the features of the large and medium motor:

  • Large motor maximum speed 170 rpm

  • Medium motor maximum speed 250 rpm

  • Large motor torque when rotating 0.21 N∙m (Newton-meters is a unit used to measure torque)

  • Medium motor torque when rotating 0.08 N∙m

  • Large motor torque at standstill 0.42 N∙m

  • Medium motor torque at standstill 0.12 N∙m

  • Large motor mass is 76 grams

  • Medium motor mass is 36 grams

The large motor will be excellent to power the drive train of our robot, and if you need the extra speed, you can always gear the motors up. If you need more torque, you can gear down. The medium motor is about half the mass of the large motor. The medium motor actually spins about 50 percent faster than the large motor. The torque of the medium motor is only a fraction of the large motor. This makes the medium...

Large motors and gears


We will be building a simple gear train with two gears powered by the large motor. The gears we are using are double bevel gears. Normally, when you think of a gear, you are thinking of a straight or a spur gear. The LEGO double bevel gear is essentially a spur gear in the middle, with beveled edges on both sides. Not only does this allow you to combine two double bevel gears aligned parallel to each other as we are in this section, but you can also combine them at right angles, as we will see later in this chapter. I chose this particular set of gears because they are included in both the Home Edition and Educational Edition kits. However, you could build a gear train like this using any set of dissimilar gears. The small gear has 12 teeth, and the large gear has 36 teeth. The motor will power the larger gear. We will find that every time the large gear spins once, the small gear will spin three times. So we are gaining speed, but at the cost of losing torque. This...

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Description

This book is for the hobbyists, builders, and programmers who want to build and control their very own robots beyond the capabilities provided with the LEGO EV3 kit. You will need the LEGO MINDSTORMS EV3 kit for this book. The book is compatible with both the Home Edition and the Educational Edition of the kit. You should already have a rudimentary knowledge of general programming concepts and will need to have gone through the basic introductory material provided by the official LEGO EV3 tutorials.

What you will learn

  • Design a robot for optimum navigation and place sensors for optimal calibration
  • Control multiple robots through a master robot
  • Decipher the advanced programs developed by LEGO
  • Account for weight and balance issues in your design
  • Calibrate the sensors using buttons on the robot
  • Utilize core programming concepts such as loops, case structures, calculations, variables, and arrays
  • Enhance your programs with proportional and PID control

Product Details

Country selected
Publication date, Length, Edition, Language, ISBN-13
Publication date : Jan 27, 2015
Length: 284 pages
Edition : 1st
Language : English
ISBN-13 : 9781783985029
Vendor :
Lego
Category :

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Product Details

Publication date : Jan 27, 2015
Length: 284 pages
Edition : 1st
Language : English
ISBN-13 : 9781783985029
Vendor :
Lego
Category :

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Table of Contents

13 Chapters
1. Engineering Notebook Chevron down icon Chevron up icon
2. Mechanical Design Chevron down icon Chevron up icon
3. Drive Train and Chassis Chevron down icon Chevron up icon
4. Sensors and Control Chevron down icon Chevron up icon
5. Interacting with EV3 Chevron down icon Chevron up icon
6. Output from EV3 Chevron down icon Chevron up icon
7. Advanced Programming Chevron down icon Chevron up icon
8. Advanced Programming and Control Chevron down icon Chevron up icon
9. Experiment Software and Data Logging Chevron down icon Chevron up icon
10. Other Programming Languages Chevron down icon Chevron up icon
11. Communication between Robots Chevron down icon Chevron up icon
12. Advanced Robot – Gyro Boy Chevron down icon Chevron up icon
Index Chevron down icon Chevron up icon

Customer reviews

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Rating distribution
Full star icon Full star icon Full star icon Full star icon Half star icon 4.1
(14 Ratings)
5 star 50%
4 star 28.6%
3 star 7.1%
2 star 7.1%
1 star 7.1%
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Marc Helfman Jul 15, 2019
Full star icon Full star icon Full star icon Full star icon Full star icon 5
I've been doing Lego Robotics ever since the original RCX kit came out in 1998. They finally got the software right with the EV3 and the more you delve into it, the more you'll appreciate it. This book does an excellent job of exploring all the EV3 has to offer.
Amazon Verified review Amazon
Csaba Csanaki Mar 23, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
This is a very in-depth, detailed book how to discover, learn and work with EV3.The book contains lot of codes, plans from simple to complex.
Amazon Verified review Amazon
Glenn Nov 02, 2016
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Walks you through from the basics to the advanced level,on programming and provides inspiration to go farther.
Amazon Verified review Amazon
steven Mar 18, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
This is a great book explaining how to learn to work with Lego Mindstorms EV3 with lot's of code explanations and building plans! This is a MUST HAVE for every EV3 user out there... for both Retail and Education owner!
Amazon Verified review Amazon
I. Luv Sushi Jul 10, 2018
Full star icon Full star icon Full star icon Full star icon Full star icon 5
For anyone wishing to take the Mindstorm EV3 beyond the realm of a toy, this is an excellent book. Using the knowledge gained I was able to build a custom robot utilizing all the sensors.Highly recommended.
Amazon Verified review Amazon
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