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KDY0523

Spotmicro - robot dog

by KDY0523 Feb 22, 2019
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First test of a quick walking setup using servos I salvaged from old RC toys in my shed and very rough code on Arduino Uno. Waiting on proper servos, etc. and much work still to do. Thank you so much for the model KDY.
https://youtu.be/XPo4JapexC8

Looks like a perfect platform for a jetson nano..

Great model, thank you very much. But I find some parts seems missing in file list. For example, I cannot find the parts which conneting between shoulders and side plates.

File R_shoulder

I see. F&R shoulders combination both used in front and rear framework. Thanks.

Hello ?? Is there another video?

I'm so sorry, but a Korean man has to serve in the army for two years. So I won't be able to upgrade Spotmicro for two years. I'll leave the software to other smarter people instead.

Best of luck with your service, we as a community will take care of your project while you're away. :)

Thank you very much. I am touched :')

Great model, thank you very much for her.
What is the weight of the robot? According to my calculations, it is about 4 kg, along with electronics and batteries.
In this case, in the lower joint the servo needs to be changed. When the length of the joint is 12 cm, a load of up to 12 kg / cm acts on the servo shaft. In the mode of movement the weight falls on 3 legs and the moment will be up to 16kg / cm (in case the joint is 90 degrees - the most loaded option).
If the robot climbs on some obstacle, up to 40% of its weight will act on 1 leg, the moment will be 19-20 kg / cm.
For the lower joints, it is desirable to apply servo drives with a moment of 20-25 kg / cm. For example MG958, MG968.
At MG996R moment only 9-11kg, he can not keep the robot even in statics. Either it is necessary to add some balancing elements - springs or active blockers of foot position.

It is 2.25kg with battery. Only the robot weight is 2kg. Thank you.

How do you organize servos power supply? They have a maximum power of 6.8V, a charged battery produces a voltage of 8.4V. The current consumption of each servo to 1.4A (8 pieces in the legs will consume almost the maximum current). We also need UBEC, for example, 2 pcs. HobbyWing UBEC 8A or HENGE 8A UBEC, 1 on the right side of the second on the left.

Well, with a margin for additional equipment there will be only 3 kg. Then the MG958 servo will be enough, it is not as expensive as more powerful servo drives.
Could you put the source of the foot so that I can change it under MG958?

definitely thought it was that dog thing from black mirror

how does it continue?

I have all of the black and yellow parts printed. I bought the screws today. The servos have been ordered. I have the Arduino mega.
I think that you missed 8 x 5mm nuts in your list. Also I think that the 8 x 4mm screws need to be 25mm long, not 15mm.
I plan to make a mold for the gray feet and cast them with silicone rubber.
This is a great looking design. Thank you for your hard work creating it and for sharing it.

03/12/19 Update: I posted a make with some pictures...no gray feet yet.
I need to make connections for the servos and get some batteries, too
Some additional pics are attached.
My son is planning to make a Spotmicro, too.

Awesome design! looking forward to future posts!

This is a wanderful desing, I really love it!
But, I have to say, it is not going to work. I'm doing a robot dog whit the same motors but a different desing, and I've seen many problems that in this desing are imposible to solve.
Over all, this is really the best thing i've ever seen on thingiverse, great job.

Good morning Sergio!
Can you tell us more about your design or maybe show us some pictures of it?

I have been thinking for days if it was possible to drive the legs with brushless motors and encoders....James Bruton from xrobots used brushless motors with his opendog project.
What do you and others think about the idea?

Have a good day!

Hello,
I would like to publish something about my design...but not yet: it is not ended, I'm still working on it. You can see something about it on my instagram profile " sergio_gugliandolo ". There are some stories where it is trying to move xD. Now it is nearly able to walk (in a more natural way than others on the web xD). I will publish videos and file at the end.

Talking about brushless motors I think that it could be a great idea, but in a different way from James Bruton: he is using screw actuators, powerful but too big in my opinion. There are many projects as " https://www.youtube.com/watch?v=WwEuJozJMuc " that are better. I'm still using brushed servo for their semplicity to be programmed.

Write back if you have some ideas ;) .

Thanks for your fast reply!
I understand that you want to finish your project before you release it :)

Exactly! Those screw bearings are huge and way to slow..
I sat that video you linked by Paul Gould and it looks amazing. I really have to dig deeper into all the materials and instructions though before i can decide what to print :D

Are there any powerful yet cheap servos out there?

I'm using mg996r. 50 euros for 12 motors, and 10 to 15 kg each. I like them. They are probably not the best ones, but very cheap. I spent many money for raspberry and a camera, an arduino mega for all sensors 2 18650 batteries and many other things... I also bought my first 3d printer for 300 (a goog one: anycubic i3 mega) so i didn't want to spend too much on motors. The mg996r works great for now. each piece of the leg of my robot i 10 cm long, and all the weight is obviusly divided for 4 legs. I think that they are good (even if it wont be able of jumping or of doing extrahordinary things).

https://www.amazon.it/diymore-MG996R-Digitale-Elicottero-Controlli/dp/B07DQJ1JXY/ref=sr_1_6?keywords=Mg996r+Servo&qid=1556124403&s=gateway&sr=8-6

I suppose it's feet are printed with some flexible TPU material to have more grip.
I also might change ultrasonic sensors to lidars, ultrasonic sensors could have some problems to work at such a low angle. They might also interfere with each others.

Definitely gonna print and build this!

Hi,
first of all, congratulations for this very interesting design, great job.
But I have some concerns or questions.

  • I think the Arduino has not enough computing power to move the servos and scan and map the environment. I would recommend off loading the computing intensive tasks via Wifi to a PC. From the PC you can even offload AI tasks to cloud services. This way you can have speach or face recognition. Off course you need a camera for the robot.

  • Have you calculated the load and the resolution of the servo in the arm joint? The servo what moves the arms in and out. I am not sure, but I tend to doubt if the direct drive will provide enough precision of movement at the end of the arms. Also the torque load of that servo will be very high if the arms move out, for example when the robot stumbles or falls. The holding load on the lower servos will drain the battery.

These are only some of my ideas, but anyway I still admire your construction and I have already ordered the servos :) I plan to use an EZ-Robot control unit.

You can, an arduino mega can individually control up to 48 sg90 servos at once. But I agree I personally would use an arduino to control the servos, antoher to read the sensor information and they both communicate to a raspberry pi (mainly because it is easier to do image recognition on a pi)

his instagram said he hasnt written any code yet.