Saturday, July 11, 2020

Minions!

A Dream of Totally-Not-Evil-Robot-Army Minions!!


Minions - and not the D'zney ones!  Every Mad Scientist needs them.  Especially if you are going to build a robot army. Minions can be the foundation for any robot army, the very lowest of the 'foot soldiers'. What would be the robot equivalent?  Perhaps the most simplest robot configuration. In 'Agile' speak: the Minimal Viable Robot?

Robotic Minion with a Manipulator Arm

The Minimal Viable Robot, would have the minimal number of parts, and be the easiest to replicate. It could be small, one would say Miniature. A minimal, miniature robot - the first one in the Robot Army.  It will be a Min-i-on, and mini-one, a Mini1!

Lets build it!!  Because this Robot Army needs many many more robots!  It needs Mini1s!!

Mini1 sketches

Design


What is the bare-bones, minimalist robot, that still has some kick?  I would propose:

  • 2 Wheels
  • 2 Small Motors
  • a Motor Controller
  • Microcontroller
  • and a Battery

That sounds really basic. but, if it is going to do something - like to serve butter - in needs at least a sensor and a manipulator.

Here are some parts I have laying around the Totally Not Evil Robot Army Lab. This is a really cheap build with these parts. The Wheels are from an old printer. The motors came off of a chotsky fan I collected from a trade fair. The motor driver is a little overkill L298N but will do the job. The microcontroller is a Arduino Pro Mini (clone) about $5. and for power perhaps this battery bank battery 5V.  For a sensor, I have a common ultrasonic ranger HC-SR04.  And if I go for an arm, I will use simple micro-servos. In the bottom corner is a ESP32, which would be more powerful, and provide wifi/bluetooth - perhaps for future versions.

Potential Parts for a Mini1 - Robot Minion


Alright!  Let's get started:

Mini1 - first CAD sketch - OpenSCAD

Friday, July 10, 2020

Crappy Robot Stories #1: Secondhand Love

 Crappy Robot Stories...


The front door to the shop slammed open andValk stalked through, block trench coat swirling around his ankles. He marched through the store, past the ranks of metallic soldiers standing motionless, to the counter at the back of the store. Beneath the display cabinet, rows of motherboards and semi-organic AI’s sparkled in the lights.
              Val slammed both hands down on the glass.
              “I demand a refund!” he shouted at the clerk behind the counter. Electricity sparked off of the stray white hairs that stood out in all directions from his head like a puffy cloud.
              The clerk behind the counter didn’t flinch from the sudden noise. Instead, he slowly dog-eared the page of Evil Today that he was reading before closing the magazine and laying it off to the side. Finally, he raised his bored gaze to the puffing scientist on the other side of the counter.
              “Welcome to Secondhand Evil, how can I help you today?” he intoned.
              “I demand a refund for… for… for that!” Valk shouted again, pointing behind him. As the clerk looked, a metallic head with a single eye widget poked around the villain’s back.
              “Hello,” the robot whirred. “My name is Bobs, minion robot 001.”
              “What seems to be the problem?” The clerk asked.
              “It’s supposed to be an evil robot. I specifically asked for the Villainy 2.0 software to be installed, and it hasn’t been!”
              “All our models come standard with the henchman software Villainy 2.0 installed. Why do you believe your model does not?”
              “It doesn’t do anything evil!”
              The clerk sighed and pulled a complaint form out from beneath the counter. “Can you give me some examples?” he droned.
              “I told it to prepare the lab for experiments, and it cleaned my lair. The floors are freaking sparkling!”
              The clerk looked up, one eyebrow raised.
              “I had just the right amount of evil chaos! It’s too neat now! It interferes with my evil creativity!” Valk screeched.
              Behind him, gears whirred as the cycloptic robot peeked around its owner again. “There were roaches.”
              “That’s not the point!”
              “Okay, it cleaned without command. Anything else?” The clerk asked.
              “Yes! I identified a homeless man that would make the perfect minion, and I sent Bobs out to recruit him. The guy was recruited…. to an IT firm as a manager! He now makes six figures and can comfortably support his family!”
              The clerk rolled his eyes and began to scrawl on the form. “Failure to follow directive to necessary level. Anything else?”
              “He made me contribute to the middle class. I loathe the middle class!”
              “Yes, yes, I know the Evil Rulebook as well. Anything else?”
              “He’s constantly baking cupcakes. My entire lair smells like vanilla!” Valk’c chest heaved as he turned to glare at the robot.
              The clerk looked at the robot as well. Bobs held up a pink box and offered it to the clerk. He opened it up to a perfectly frosted cupcake, wrapped in a lacy doily.
              “Oookay, that’s a new one,” he said slowly. “Are they any good?”
              “They’re delicious!” Valk screeched. “And they aren’t even poisoned? What kind of villainy is that?”
              “I see.” The clerk closed the box and stored it beneath the counter. He pointed up above his head, at the large sign suspended from the ceiling.
              All purchases are final. NO REFUNDS, NO EXCHANGES.
              “Oh, come on, you have to do something for me!” Valk insisted. “What about in-store credit?”
              “Nope. All sales are final. You acknowledged the risks of buying a second-hand robot when you signed the contract with us. Would you like to see your signature? I can pull up the agreement right now.”
              “I want to see your manager!”
              The clerk rolled his eyes. “I mean, I can call her if you want me too, but she said she was working on her death ray and she was going to use anyone who interrupter her as target practice.”
              Valk glared at the clerk, who stared back with the dead gaze of someone who had spent way to long in retail.
              “Fine!” he snapped, spinning around. “Bobs, we’re leaving. Se if I ever come to this stupid store again! I’m going to tell everyone how terrible the place is!”
              The robot waved one, then raced off after its master with a whirr of gears.
              The clerk sighed, shook his head, and flicked his magazine open.
              “Cupcakes,” he sighed. “Really?”


Monday, July 6, 2020

Tilt! - A Balancing Robot (#2) - Online Inspiration


There are certainly influencers that I am using while developing this idea. Here are links to their videos, libraries, and project pages.

From the Internet:

James Bruton

He is loud and British, but you have to admire his enthusiasm!



OzBot - Red

These are nice robot builds. and good inspiration and guidance.


Of course - this guy's proto-robot army.  From his 2018 blog: Electronics and Robotics.

Open Source Libraries:

I am benefiting from some OpenSource libraries

Jeff Rowberg’s  I2CDev

Brett Beauregard’s  PID Library

More General Inspiration and help:


Homofaciens project page on using Transmissive optical sensors to create DIY servos.

DroneBot Workshop video description of using the MPU-6050.  As well as a nice project page.

This looks pretty detailed too..  kas on the Arduino Forums has a nice long thread on the topic of Balancing Robots.  I certainly liked his disclaimer: 
"I invented nothing
I read A LOT and went by trial and error"

Monday, June 29, 2020

Tilt - A Balancing Robot (#1) - Thinking about it

Tilt will be my next robot with a focusing on implementing Dynamic Control in Robotics.

There are a good number of videos on YouTube from 2 years ago on how to build a "self-balancing robot". I do find these fascinating, and I would like the experience of building one - of course as cheaply as possible with as many reused parts as possible.  ;)

I am challenged by the engineering aspects of this type of robot.  Perhaps because ... that an inverted pendulum was offered as a senior project when I was an undergraduate. I passed on it due to the complexity at the time, and lack of good motors and controllers. Yes, I am a bit haunted that I *should* have done this project. So, I feel like I should re-live my Control Engineering days and build this robot! :)

I feel that these type of control will be standard in most future interesting robots. I sense that we are still at the early aspects even though Dynamic movement has been a part of the current stable of robots. we are starting to see combinations of quadrupeds -and- wheels. (Soon, I would not be surprised to find reaction wheels also included for more stability and agility.)  

However - after all that is mentioned, these types of developments are still very uncommon in the DYI Robotics space!

Moving forward with this robot, the numbers and types of parts are limited.  Here is what I am considering at this point:

  • 2 wheels, recycle, reuse, or print
  • 2 motors - 9-12v from a recycled printer
  • 2 belts - to drive the wheels and do some gear reduction/torque
  • 2 encoders - used to measure the output of the motores
  • 1 motor driver for DC brushed motors (L298N)
  • 1 micro controller - EPS32 or Arduino Nano or other
  • 1 motion sensor - MPU-6050
  • 1 battery solution - drives the motors, powers the electronics
What else would I need?

OK - Time to scavenge for parts!  and think about an encoder solution.

Thursday, June 25, 2020

Intergalactic Planetary (gears)!

Just doing some thinking and sketching on how best to use Recycled Printer Motors in my robots. 

One of the Totally Not Evil Robot Army motivations, is to make robotic creations by recycling parts from existing technology. To RE-USE, is the best approach to waste management. -- and also of course, because I am really, really cheap.  ;)

Recycled Printer Motors

Most computer printers have these nice (DC Brushed) Motors, but they tend to be too fast and with out a lot of usable torque for my projects. This would be expected, since the printers they come from have a lot of built in gear reduction.  For power, they typically require 12-18v. These are not light either, they have some weight to them. In order to utilize these printer motors, they will need a gearbox to both reduce speed and increase the torque - which is exactly what gearboxes do for motors.

The Planetary Gear is a good choice for a compact way of converting the motors output into a stronger more useful force.

The Planetary Gear is made up of 4 pieces, The Sun Gear, one or more Planet Gears, The Carrier (connecting Planet gears) and on the outside, the Ring.

Named Parts of a Planetary Gear Box

The configuration of a planetary gear box can vary based on specific needs. Any one part of the system can be 'fixed' which allows for the other two parts to become the Driver (input) and the Output.  

Example:  by fixing the Ring and attaching the drive motor to the Sun, it makes the Planetary Carrier to become the Output and move.  Likewise, you could fix the Carrier and attaching the drive motor to the Sun Gear, would cause the Ring to be the output and move.

Here is a quick 3D print or sketch of the Planetary "Wheel".  Here the motor and Carrier are the same part. This allows the motor to directly drive (input) the Sun gear.  Since the planets are fixed, the Ring will move. I have built the Ring gear to be the inside of a wheel.


Planetary Wheel
Motor Mounted on the Planetary Carrier

On the reverse side you can see the planetary gears encased in the wheel. The Sun Gear is removed.


Complete "Planetary Wheel"


Gear Reduction with Planetary Gears


The actual gear reduction and torque increase can be calculated based on the number of teeth in the gears or the radius of the gears (given a specific modulus).  The equations are similar to basic gear equations, however there are differences due to the planetary gear set.  here they are:

For the gear ratio of a basic gear 

    i = Z2 / Z1 

where Z are the number of teeth on Gear 1 and Gear 2

For the Planetary Gear, we have the number of teeth - Zs for Sun Gear and Zr for the Ring. The number of teeth on the carrier does not matter, since it is derived and removed from the equations. (also, it does not matter how many actual planet gears you have).

the equation for planetary gear reduction is:

    i = 1 + (Zr / Zs)

Here is a nice little summary video of deriving the gear-ratios of Planetary Gears.


(Update:  here is a nice summary sheet from the MIT FAB LAB)

Testing the 3D printed gear box


I was able to make this wheel work pretty much out of the print.  I did have some difficulty in the motor shaft 'stripping out' the inside of the sun gear if the gears were blocked.  this is the same problem encountered on the Milli project.  I believe some glue may help hold the gear in place, but this does not seem to be a sustainable solution. I would have difficulty replacing the gear when needed.

As a result, The Sun gear would slowly lift off of the motor spindle when operated at full speed.  (A failure you would not want if the Wheel was part of an inter-planetary rover.)

Looking forward, at these brushless motors, I believe a belt and tensioner system may work best. Most of the motors I have, already have a nylon belt gear on the motor spindle.  I will try to use this combination in one of my next projects.


Postscript

Hi all, this post was somewhat delayed due to some personal health issues.  I am doing much better now, thanks!  I have some upcoming work on a balancing robot - using Printer Motors that I am currently considering.  More to Come!  Thanks! Doug