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SmallKat: An adorable dynamics oriented robot cat

A dynamics oriented quadruped for research and education.

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$500.00
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SmallKat is a 16 DOF low cost, opensource, 3D printed quadrupedal robot. It was designed and made by 2 WPI students (Keion Bisland and Xavier Little) along with framework code prepared by WPI staff Kevin Harrington. The intention of the platform was to make a fully open source dynamics quadruped for the education, research, and hobbyist markets. Using hobby servos and common electronics allows the overall price point to remain very low in comparison to its competitors.

In addition to the hardware kits, a full education kit is provided. SmallKat has lecture slides, tutorials and lab procedures for educators to take out of the box and use to teach robot dynamics. Prior knowledge required is merely basic programming skills in Java or Groovy and understanding of Git. The education kit will onboard you to being able to teach the rest.

In addition to performance and ease of use, adorability is a high priority.

Introducing SmallKat!

The problem we wish to solve is that there is a need for hardware to teach dynamic walking robotics. When we say dynamic, we mean both able to sense perturbations, and has processing power and actuator speed fast enough to compensate.  All existing dynamics-capable walking platforms are too expensive, and all affordable platforms are not capable of full dynamics. If students are going to learn how to make walking robots walk they need to learn using hardware. At the moment only *very* well funded universities and businesses can learn dynamics oriented robot walking. 

We are leveraging 3 degrees in robotics engineering, 10 years of product design and robotics experience, and a brand new robotics IDE to provide the best possible teaching tool at the minimal possible price. We have designed a new, 3d printable cat, about the size of an adolescent kitten. We are also using the brand new BowlerStudio robotics IDE for kinematics and dynamics control. This lets students run their code on the workstation in front of them and see it controlling the SmallKat across the room.  In addition to cutting edge tools, we have a comprehensive teaching package. SmallKat was used to teach robot walking dynamics at Worcester Polytechnic Institute (WPI) and those teaching materials are availible alongside the SmallKat sources. The teaching pack includes tutorials, lab procedures, lecture slides with scripts and teacher onboarding tutorials. No other walking platform has such cutting edge architecture, nor prestigious teaching materials. 

What makes this system so unique is the way students write and test code. BowlerStudio lets the students control SmallKat over the rooms WiFi network. Students code runs as scripts on the PC they are using to develop, and the control commands go over WiFi. This code is quick to change and re-test, making the students experience smooth and delay free. BowlerStudio itself is designed with documentation and tutorials front and center. All documentation is visible from inside BowlerStudio, and the code examples are executable. Executable documentation makes the connection to a description of what something should do, and seeing it happen one click away. Not only is the documentation excellent, it has been teach-tested at WPI. The SmallKat platform was used to teach WPI Robotics Engineering students how to write dynamics controllers. This curriculum and teaching materials are all open-source. WPI has agreed to partner with us to promote SmallKat and help us on the distribution.

The functional structure can be broken down into two major blocks, the high level gait & kinematics computation done in bowler studio and the lower level done by the micro controller on board the robot.


Bowler Studio functional diagram:

MCU Functional Diagram:

Our business model is to sell classroom kits of hardware, and individual fully assembled SmallKats. We have the backing of a top tier Robotics Engineering college and will use that backing to promote this platform to aspiring colleges and advanced high schools. The intent is to provide a lifestyle business for the developers, and to leverage resin casting for bulk orders. All SmallKats can be 3d printed, and for initial fulfilment we will provide printed parts. We will also be refining a resin cast process to streamline production and ensure consistent parts. 

The process to bring SmallKat to market is incremental. In the initial stage we will lean source components and print the plastic to order. As we scale up, we will increase the number of printers dedicated to SmallKat printing and hire a member of the local Makerspace to put together kits. If we outgrow this production throughput, or if we got a large lump sum, we will hire a member at our local makerspace who used to make resin molds for Hasbro. We have already discussed feasibility and would just need to engage him to make the molds. As we spool...

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SmallKatGraceFinal-v3.zip

The final print beds for a complete smallKat Grace

x-zip-compressed - 4.65 MB - 11/07/2019 at 16:13

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LunaSTLs.zip

All files and print beds for SmallKat Luna

x-zip-compressed - 17.08 MB - 10/28/2019 at 16:22

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SmallkatVersion2CADandSTLs.zip

Zip file of latest revision stls and CAD

x-zip-compressed - 13.23 MB - 10/01/2019 at 03:47

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Calibration Side 2.step

Calibration Block Step file mirrored version of side 1

step - 97.36 kB - 09/19/2019 at 17:49

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Calibration Side 1.step

Calibration Block Step file

step - 96.83 kB - 09/19/2019 at 17:49

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View all 12 files

View all 17 components

  • Howto Balance the SmallKat

    Kevin Harrington3 days ago 0 comments

    I made a video explaining the math governing the SmallKat's balance control system. 

  • SmallKat Math Video!

    Kevin Harrington11/11/2019 at 18:15 0 comments

    I have posted the video for this weeks lecture on the Math of the SmallKat

  • SmallKat Kinematics

    Kevin Harrington11/10/2019 at 23:24 1 comment

    This weeks videos have to do with the math the controls SmallKat. Tune in if you are a math nerd looking to understand robot kinematics!

  • SmallKat Assembly and Calibration Videos!

    Kevin Harrington10/24/2019 at 15:31 0 comments

    I have filmed a set of videos that take you through assembly and calibration of SmallKat Grace. 

  • Thank you!

    xaveagle10/01/2019 at 04:23 0 comments

    As this competition nears its end, we just wanted to take a quick second to thank everyone who has supported this project. When we first started Smallkat it was really just a challenge to see if it was possible to make a super small and adorable quadruped. We really did not expect it to become as big as it has. Smallkat has been a staple for robotics demonstrations at WPI for over a year now bringing smiles and wonderment to both kids and adults. We have encouraged and inspired students to learn more about quadrupeds and robotics in general and take on challenges they might not have thought possible. Smallkat has been a past time, a senior project and a passion of ours for the last two years and we are excited to share this adorable robot with the world and hopefully inspire more people to build, create and get excited about engineering. Thank you to everyone who has shown interest and support, built their own Smalkat, asked questions and most of all, for letting us share our project with you.

  • SmallKat Curriculum!

    Kevin Harrington09/23/2019 at 19:40 0 comments

    Here is a link to the SmallKat teaching curriculum:

    https://docs.google.com/document/d/16jmpZ8z6Lw8g2hYu_gwpO5CaW7e0nuaeb-JE35jBCps/edit?usp=sharing

    Here are the lab procedures:

    http://commonwealthrobotics.com/Mobile-Base-Control/BasicWalking/

    The lectures are being recorded one by one as the class is taught in B term (Mid October through End of December). They will be recorded and posted on youtube. 

  • Design Revision: Update 2

    xaveagle09/20/2019 at 16:51 0 comments

    Its been some time since the latest revision of the cat but we have been busy. We tested the last version from our previous design update and found it to be a little too big and heavy for what we wanted. For this version we essentially combined the original version and last version together. The features of this version include the following updates:

    • Longer legs and a slightly larger body with same setup as orginal
    • Uses M3 hardware for easier procurement and assembly. M2 nuts constantly stripped out of plastic. 
    • Optional encoders for additional feedback
    • Improved calibration 
    • Better aesthetics 

    This version of the cat has more parts than the original however the assembly process is significantly easier and it is more robust. Additionally replacing servos and other parts takes much less time. 

    The next step will be wiring and running this version through some tests with walking and fixing a few small design errors with tolerances. This version is getting closer to what we hope a final and commercial product would like. Still a lot of work and testing to go before we get to that point. For now enjoy the working prototype featured on our page!

  • A friendly user helped out with a wiring diagram!

    Kevin Harrington08/16/2019 at 20:33 0 comments

    Shout out to @jtechs who made a lovely wiring diagram as he builds the FIRST build of SmallKat made by another person!

  • New Assembly instructions and BOM purchasing info!

    Kevin Harrington07/16/2019 at 20:36 0 comments

    Today was busy and productive! I printed out a new Grace model SmallKat and made an assembly instructions document. Check it out here:

    https://github.com/OperationSmallKat/SmallKat_V2/releases/download/0.0.2/Catbot.build.instructions.pdf

    In it you will learn how to assemble a smallkat robot, as well as calibrate all its links.

    I also added the purchasing direct links on all of out BOM:

    https://hackaday.io/project/164727/components

    This should fill in the mystery steps in our previous documentation. 

  • Design Revision: Update 1

    xaveagle07/09/2019 at 03:47 0 comments

    Quick update on the most recent version of the cat. We took a look at our previous designs and have started making some improvements. 

    These include;

    • Longer legs and a slightly larger body
    • Easier assembly - many of the parts will be the same and reversible so its harder to mess up
    • Easier manufacturing down the line. Similar parts allow for easier mass production
    • More customization  
    • Optional encoders for additional feedback
    • Improved motherboard with room for 20 servos
    • Improved calibration 

    The current design still needs a revision or two. Currently its very blocky and hastily made so that electronics can be tested. Further revisions will have nicer aesthetics. Additionally we are re-evaluating our choice of hardware so that we can better supply parts. We also need to stress test the system with the larger body size and additional weight 

View all 18 project logs

  • 1
    Fork the Smallkat configuration

    Before building anything, lets load up our personalized copy of the SmallKat framework. Navigate to the Greycat repository and fork it:

    https://github.com/OperationSmallKat/greycat

    Once you have it forked, copy your new git URL

    https://github.com/javatechs/greycat.git

    And replace the existing:

    https://github.com/OperationSmallKat/greycat.git

    Open MediumKat.xml and do the same on line 8.

    Open launch.groovy and change Line 3.

    You now have a fork of the MediumKat configuration with a hardware launcher!

  • 2
    Launch your fork of SmallKat

    Download and install BowlerStudio and Java 8. 

    http://commonwealthrobotics.com/

    Open BowlerStudio and login with your Github username and password. 

    Use the Github menu to navigate to your fork of greycat and open launch.groovy

    Use the run button to launch your robot. A simulation of your robot will open on the 3d window. You can make it walk using the arrows in the top right of the Creature Lab tab.

View all 9 instructions

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Discussions

coopervarley wrote 12/02/2019 at 12:59 point

A very cool project, which was developed by college students, I would like to talk with them and learn more about the development of the project. I would also like to recommend you a service https://paperell.com/write-my-thesis where you can write your thesis, I think this is a great resource for you.

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Louis Hill wrote 11/25/2019 at 10:26 point

I would say that this could be modified so that children who are cancer patients can interact with the cat. https://g.page/CommercialRealEstateCincinnati?share

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debil1 wrote 11/09/2019 at 21:30 point

Hi,

I have some questions:

1. what printing setting do you recommend (infill, supports) ?

2. which red board is used for ESP32 ? I can not find it on "components" list?

Or can we use instead it, bread-board? Can I use: https://bit.ly/32yZ5L6 ?

3.. will code work with much cheaper bno055  (https://bit.ly/2PYDl93)  as one from "https://www.adafruit.com/" is not cheap...?


Thank you.

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Clément wrote 10/04/2019 at 13:42 point

Hi, I decided it's time to make a SmallKat :)

Is there more details about the motherboard (and related assembly) ?

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Kevin Harrington wrote 11/07/2019 at 16:22 point

We have a build instructions pdf in the instructions section, as well as a set of videos showing the entire process here: https://www.youtube.com/watch?v=QnPbU4okW08&list=PLrTh8skra715CDtLi1BoX_ObPwqbkul6S&index=4

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Suyash wrote 09/12/2019 at 03:59 point

Hey.. Love the idea! I was considering making one of these for myself and need some suggestion. The recommended MG92b Micro Servo is quite pricey here in India. Is there any alternative that I can try? Something like a drop-in replacement but not as amazing as the MG92b. Let me know 😅

  Are you sure? yes | no

Kevin Harrington wrote 09/12/2019 at 10:49 point

SmallKats size and weight are such that any cheaper servo would destroy itself in a few minutes of running.  We push the mg92b to its limits in SmallKat and i have little hope of a cheaper one working at all. 

  Are you sure? yes | no

xaveagle wrote 09/20/2019 at 16:53 point

As kevin said the Mg92bs are really the recommended servo. You could try the MG90Ds as they will fit the design but they are not as powerful and might not last as long.

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dana2048 wrote 09/12/2019 at 00:33 point

awesome project!

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[deleted]

[this comment has been deleted]

Kevin Harrington wrote 04/23/2019 at 14:14 point

Thanks! I will be in touch as we go into development this summer to build the new stand-alone variant. 

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Ken Yap wrote 04/12/2019 at 02:52 point

Love cats. The "ignore you" part of the coding would be simple. But seriously, love cats. Meow!

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Starhawk wrote 04/12/2019 at 02:11 point

Meow!

...but seriously, I want one. A pity, because I can guarantee you that I can't afford it :(

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Keion Bisland wrote 04/12/2019 at 02:48 point

you might be surprised. The projects open sourced so you can print everything yourself and all the other components only less than $300

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Starhawk wrote 04/12/2019 at 02:50 point

I have a dead maximum of $200/mo disposable income and no 3d printer.

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alireza safdari wrote 04/11/2019 at 17:37 point

We deserve more information. :)

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Kevin Harrington wrote 04/11/2019 at 18:49 point

geez man im posting as fast as i can...

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alireza safdari wrote 04/11/2019 at 18:51 point

@Kevin Harrington  Sorry, did not want to push you. Take it in a positive way, like there are people out here who are interested to know more. :) Thank you for posting.

  Are you sure? yes | no

Kevin Harrington wrote 04/11/2019 at 18:53 point

no worries! Im excited to get this public facing after a year of under-the-radar developemnt with Keion and Xavier

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alireza safdari wrote 04/12/2019 at 04:18 point

@Kevin Harrington You guys are on fire :D Thank you for posting more information. :)

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Kevin Harrington wrote 04/11/2019 at 22:40 point

I added a bunch more info :)

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alireza safdari wrote 04/11/2019 at 22:41 point

Going to read them now. Thank you.

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alireza safdari wrote 04/11/2019 at 22:46 point

@Kevin Harrington I really love your solution for programming the cat. Am I outdated or this has never been done before?

  Are you sure? yes | no

Kevin Harrington wrote 04/12/2019 at 12:00 point

This is rather new way to program and control robots, yes. My contribution to the project is the programming framework, [BowlerStudio](http://commonwealthrobotics.com/). I wrote the programming environment, the kinematics models and the hot-swapping Git based script architecture. 

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Dan Maloney wrote 04/11/2019 at 16:42 point

If it doesn't spend 90% of the time sleeping, 5% puking, and 5% licking itself, it's not a proper cat. ;-)

But it's still really cool, and I'm looking forward to seeing more. Nice work!

  Are you sure? yes | no

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