Instruction Guide: EV3 - Moving with Linkages
1.) On the first day introduce students to a few videos of robots that move without wheels (ones that use linkages and ones that do not).
Here are some example videos you can use to accomplish this:
Discuss with the class what the difference is between the robots in the first video and the robots in the second and third video.
As they start to talk about wheels or pieces moving around, ask them how humans move. Then discuss other animals.
Why have most of the robots we’ve built so far moved like a car?
2.) Show them the pictures of the EV3 Large Motor and Simple Hand-wound Motor (attached in Primary Instructional Material) and discuss the type of rotation produced by motors.
If you can make the above motor, go ahead and make one and use it as an example.
The students should be able to figure out the motors move rotationally. The opposing magnetic fields (one electric and one permanent) cause the wire to spin. That is a motor in its most basic form. When we convert electrical energy into mechanical energy with a motor, the output is rotational. If we want to change the type of output we can use a linkage.
3.) In their notebooks or wherever you have students take notes/do research (we use iPads and Google Docs in my class) have your students start a new doc/page/etc. and write down the definition of the following two terms:
animal locomotion
mechanical linkage
After the students have found and written down their definitions discuss them with the class and ask how they can be related to moving robots.
4.) Show/have the students watch this playlist:
https://www.youtube.com/playlist?list=PLdW-vHULkLtPIcovdEWctxoU1S-UeoNrj
As they watch it, have them write down five things/ideas/robots that they liked or they didn’t like. I like to have them write these down right below their definitions.
Reiterate for them the definition of mechanical linkage and what they are used for. Also repeat that one of the objectives of this lesson is to build a robot that moves using linkages. To begin they are going to build some sample linkages to see what they are like and how they work.
5.) At this point I share with them a .pdf file of builds by the famous LEGO technic builder, Yoshihito Isogawa called Tora No Maki. His books are amazing and of great benefit to any Robotics’ teacher using LEGO. You can download this file for free from his website here. He allows you to download it for free but does ask for a donation. I had my school district make a donation to him.
On the document there are several pages that have sample linkages he has built with LEGO pieces. On pages 32 and 33 there are nine different linkages you can have them build.
**Some of them use pieces that you may not have in your EV3 kit. I suggest the teacher build them all ahead of time to see what pieces you have and what pieces you may not. There are some builds on page 34 that also use linkages but these also require a lot of pieces (small triangles, short rack gear, LEGO pulleys) that are not readily found in most EV3 kits.
After my students have built these, and I have each team build all nine of them, I ask them to set aside their two favorite and to either take pictures and upload them digitally to their notes, or write about them and describe them in their notes.
The preceding activities usually take about one class period, but you can decide for yourself how far you can get in a period of teaching.
6.) At this point I use another book by Yoshohito Isogawa titled The LEGO Mindstorms EV3 Idea Book.
I purchased this book from No Starch Press (www.nostarch.com) and when you purchase their hardcover books you get unlimited downloads of that book. So I have the hardcover but I am able to provide my students with digital copies to work and learn from. If you do not have this book or do not wish to purchase it, then there is an alternative way you can do the next part.
On pages 36 and 37 I have my students complete builds #52, #53, and #54. The build numbers are in red at the top of each build, while the page numbers are in black at the bottom of each page; some .pdf readers read the build numbers as page numbers so be careful when searching.
These three builds are similar to the ones they built from the last book, but these use pieces found only in a single EV3 kit. If you don’t have the EV3 Idea Book, then you can skip this last part and we’ll modify the next part.
On pages #38, #39, and #41 there are several linkages attached to medium and large EV3 motors. (Builds #55-62 to be specific.) I have my students choose and each team will build one of the mechanisms shown attached to a medium motor and one of the ones with a large motor.
If you don’t have this resource to use, here’s how to modify it:
Have your students take the linkages they built using the free downloads from Yoshohito Isogawa and modify them so they can attach them to a large EV3 motor.
After your students have built several linkages and built a few motors with linkages attached to them, it’s time to share out. Have each team demonstrate the one motor they think will be the best one to use to create movement that is not rotary with their robot.
By the time all students have finished these builds and shared out their work and ideas with each other you will most likely have hit the end of another day.
7.) On the next day go back to the learning target and reiterate for the students why you are doing this unit. We want to produce some type of motion that is more akin to animal locomotion rather than car wheels and we want to use linkages to accomplish this. Then present them with their task: Build a robot that moves forwards in a straight line for a distance of two or more feet using linkages. (I allow students to use a wheel for support or to help overcome friction, but they must not be turned or moved by a motor. The motors must turn one bar of the linkage and the movement must follow from there.
It usually takes my class about 6-8 days (including the two original exploration days) to build a machine that moves on its own using a linkage.
