mechDOG (robot dog based on Arduino and LSS)

Lynxmotion Legged Robots
,
1

Hey guys!

This is my second attempt to build a robot dog. I am more confident in this iteration, since I am using 12x ST1 servos.

The chassis is handmade with 1.5mm thick aluminum sheet. There are other parts also made by hand with high impact polystyrene.

To control it I am using an LSS Adapter board stacked over an Arduino Uno.

I would like to write much more and show all the details of the construction (I will do this when everything is working). Now the total focus is on programming.

Thread is open for general discussion about this project.

mechDOG_01
mechDOG_012048Ă—1152 864 KB
mechDOG_02
mechDOG_022048Ă—1152 761 KB
mechDOG_03
mechDOG_032048Ă—1152 795 KB
mechDOG_04
mechDOG_042048Ă—1152 717 KB
mechDOG_05
mechDOG_052048Ă—1152 771 KB
mechDOG_06
mechDOG_062048Ă—1152 716 KB

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Hey @dickel !

It looks great :slight_smile :slight_smile:

When it’s finished, we hope that you will post it in our Robots section :slight_smile:

We are looking forward to it :slight_smile:

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@dickel Well done! Can see the SPOT Mini inspiration. Your creations are always very professional. Think it will need an extra DoF per leg to help with turning?

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Awesome! You should tag your post NSFW…cuz I just lost an hour of work time checking out all your videos. haha. You have some great videos and nice job on the new robot workspace. :slight_smile:

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Thanks!

For sure!

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Thank you very much!

I think and hope that the 3 DoF will be enough… at least it worked on several similar DIY robots I’ve seen.

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Haha! :sweat_smile: Thank you very much!

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And… IT WALKS!

I am very happy with the result. I know… there is a lot to improve… but, having worked practically only with robots moved by tank tracks and DC motors and having very limited knowledge in programming, this project is well outside my comfort zone…

Spent about 3 days trying to figure out how to make it walk and write a functional code. For now the code has no IK implemented.

As I previously worked with Flash to make animations, it was easy for me to find the angles, creating two lines (red and blue) that represent the leg segments and I was able to position them where I wanted and to find the angles I used a drawing of a protractor of angles.

steps_pos_6
steps_pos_61140Ă—713 44.6 KB

20200505_225211
20200505_2252114608Ă—2592 2.2 MB

Yep. It’s a bit hard-working… but for now it’s fine.

You may have noticed the green tape on the feet… it is temporary, and serves to reduce the friction caused by the rubber tips (this should be corrected with improvements in the code).

Below is an example of how the code works:

float targetPos;
float currentPos;
float previousPos;
byte stepPhase;

void setup() 
{
Serial.begin(9600);
}

void loop() 
{
  
if (stepPhase == 1)
{targetPos = 100;
if (currentPos != targetPos)
{
  currentPos += (targetPos - previousPos)/(50);
}

else
{
  currentPos = targetPos;
  previousPos = targetPos;
  stepPhase = 2;
}
Serial.print(currentPos);
delay(300);
}

else if (stepPhase == 2)
{targetPos = -100;
if (currentPos != targetPos)
{
  currentPos += (targetPos - previousPos)/(50);
}

else
{
  currentPos = targetPos;
  previousPos = targetPos;
  stepPhase = 1;
}
Serial.print(currentPos);
delay(300);
}

else {stepPhase = 1;}

}
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9

That is well done! There’s really not much out there “ready to go” regarding IK for animal quadruped motion (quite a few papers), so the approach you took got you to a working result. As you’re likely aware, the (current) Phoenix code implemented on the Lynxmotion legged robots uses coordinate systems as opposed to IK. The lower limb seems to be at a very acute angle to the ground, likely requiring quite a bit of torque - might want to straighten it more? If you can work out a system to automatically determine joint angles, you’ll be able to adapt the walking gait, work on turning etc. Given your interest and abilities, wonder if you want to look into jumping on the ROS 2.0 bandwagon?

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Thanks!

Next iteration on the code for walking routine will have some improvements. This may be one of them. Lack of time to work more on coding right now.

I have been following the SES V2 Legged Robots thread and that got me a bit interested in ROS 2.0… but my knowledge on this is zero… also, not very familiar with RPi. So, there would be a learning curve. And I don’t have much time to work (due to my job, house, wife, son, real dogs)… so it would take a little longer to start working.

BUT I really dreamed (a few times) about an advanced/more adaptive and slightly larger version of mechDOG (even more inspired by Spot), and that would need RPi + ROS 2.0. Off course it would also need HT1 servos (everything improved, stronger).

Just daydreaming… for now!

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This is sweet. Very well put together… great work!

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Thank you very much!

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Hopefully as Lynxmotion moves towards ROS 2.0, we’ll be creating tutorials etc.
However, as you indicated, it’s quite a learning curve. Arduino is always a great language and looking forward to seeing your progress!

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Yes… first, let’s see how this project evolves… still many things to do to consider this robot “functional”… like turnings and so. Then, let’s plan the next steps on it… next improved version! :slight_smile:

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Another task accomplished… now mechDOG can turn!

To be honest, I was concerned about this specific movement… because the design of mechDOG is not symmetrical and what that implies in CoG / CoM.

Note that the green tape remains on the tips (remove it and it will be an issue… because of the asymmetrical design, the mass distribution is not well done, and the body tends to tilt to one side, and the rubber tips would cause friction.).

But maybe it can be balanced with IMU.

BUT… it’s working! Not perfect… but working. I’m happy with the result!

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mechDOG in other media:

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@dickel
Bravo! :smiley:

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This video summarizes all the progress with this project so far. Now it can be considered “functional”. Can walk, turn, do side trotting. It’s very stable and has a good speed.

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Well done! Really happy to see it reach this point and looks professional as always.

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How the chassis was built.

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