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THE NEW YamaX: Hardware of v4.0 was completed

Hello, it’s coorde.

I’m sorry for taking time to update. I’ll try to get back to update in usual interval.

So, as the title says so, the hardware of YamaX 4.0 was completed.

YamaX 4.0
YamaX 4.0

YamaX 4.0, which is made by us Y-modify, is to take part in the Maker Faire Tokyo 2017.

Our “makers page”

O’Reilly Japan, Inc.

The new YamaX

Although the previous version is 3.2, this change to version 4.0 seems to be a quite a major update.

This update contains a lot of changes.

The renewed joints

It won’t totter again.

From 2.0, we used MG996R servo motor for YamaX. It was great at first, but as it takes times, the gear is getting rattled. YamaX could walk through the way of over 200 steps, but it cannot walk through just 30 steps. That’s why we renewed servos.

As you can see in recent post, we used servo motors named “KRS786” which is used in the robot “KHR1” found at school.

MG996R (by 4.0)
KRS786 (from 4.0)

This is made in Japan by Kondo Kagaku co.,ltd.

However we could not found any documentation about this servo because it is too old.

It worked when we put PWM somehow, but it isn’t popular product anyway.

Getting thinner.

Robot which cares its figure.


Did you understand?

The width got slim.

Then, the prototype PCB used in 3.2 can’t be in the body of 4.0.

So we’ve been trying to make this work with “Green Board”.

However it was broken suddenly so I have to finish making “White Board”. I’ll try.

Green Board (for YamaX ~3.0)
White Board(In progress)
Prototype Board (for YamaX 3.2)

Easy to open and close.

Open the back cover anywhere and anytime you like.

It’s very useful despite it’s plainness.

YamaX 3.2 背中
YamaX 4.0 背中

The back cover and body are connected with magnet.

The circuit has nothing to change.

The figure below describes the inside of YamaX 3.2. (I’m sorry for cheap figure)

I won’t change this in 4.0. Although Edison will be EOL, but I’ll use it for a while.

PCB: As I wrote above, I cannot help using white board.

I wanna change, software.

Let’s move to software, which is my main work.

The figure below describes the software structure of 3.2.

I’m very embarassing because the code looks too bad, so I want to make a big change.

It should be controlled from browser because Nyanyan said that he doesn’t like CUI…


Then I pass the baton to Nyanyan.


I’m Nyanyan, who got the baton barely.

I’ll write about mechanics.

The best accuracy of processing

First of all, I’ll make a boast.

I don’t know whether my condition was good or my skill had been improved, the accuracy of aluminum processing was extremely improved. After finishing all processes including cutting, making holes, and bending, it was in error by less than two millimeters! So there was no problem regarding an error in assembly.

Also the accuracy of processing MDF board was getting stabilized.

By the way, the accuracy of YamaX had been about ±0.8mm until recently, which was quite bad.

The servo has very good performance & It started static walking

KRS786ICS is high-grade servo made in Japan, which seems to have cost about 5000 yen.

The performance is so good it cannot be compared to MG996R’s that. (However the torque is a little bit lower)

Because its speed is too fast, we found it a bit difficult to make it walk like a dynamic walking.

So I challenged a static walking first time in my life.

From crouching position move the center of gravity, raise and put out the leg, and put down then move the center of gravity again. The walking is this loop. I separated each action to frames and made a smooth moving. This was the most troublesome work.

However I found it easy to make sure where is wrong in the moving when I’m making in this way. YamaX succeed in walking within about 3 hours. It is very stable moreover.


In addition, the walking movie will be uploaded soon.

Thank you for reading!

Published in Edison KHR1 linux MFT2017 YamaX Servo motor Software Hardware Announcement