Monday, June 7, 2021

2021 Game of Shrooms

 


The Totally Not Evil Robot Army will be participating in the 2021 Game of Shroom - Art Seek -n- Keep.  If you are in Düsseldorf, Germany on June 12th 2021, you can find original Totally Not Evil Robot Army Shroom-Art!

for more details and the Clues - see the page:  2021 Game of Shrooms

you can learn more from the official site:  Game of Shrooms

Goto my Shroom Page for the details and CLUES

The Shrooms are Growing!

Shrooms are next to famous Düsseldorf painter Heinrich Ludwig Philippi

Shrooms in the Wild!


2021 Game of Shrooms - Totally Not Evil Robot Army

Goto my Shroom Page for the details and CLUES

#gameofshrooms #shroomdrop #düsseldorf


Tuesday, June 1, 2021

Tilt! - A Balancing Robot (#7) - Initial Tests

 

[This is an older post that did not get published. It describes the last steps taken on Tilt!  This was also part of the motivation for building a gearbox for recycled printer motors.]

Tilt! Balancing Robot - testing configuration


After some time with "communication failure", I sorted out some loose connections and got the initial prototype working!  All hail the Cargo Cult Programmer! (need to to write more of a story on this one I think.)

Torque and the Printer motors.  The large gear ratio with the belt pulleys is working. The wheels are turning and it is just enough to suggest that there is an attempt at ballance.  At least this seems to be true in one direction. 

12V Testing.  Some testing with the 'power' of the motors or how easy it is to stall the motors is *not* very encouraging. with only small effort, I can stall the printer motor.  This is with 12 volts of power - certainly at the lower end of the rating for these motors.  Attempting more power up to 18V will be worth the test, although my built in battery bank only supports 12v.  (thinking)  18V with a RC battery might be feasible.

18V Testing.  By connecting the robot up to 'shore power' (tether), I bypassed the onboard battery and supplied 18V to the motors.  The robot was a bit more responsive, and the issue became more clear.  Instead of stalling, the motor caused the belt to slip.  In either case, a re-design of the motor-drive-wheel system is in order.

Another aspect is to reduce the gear ratio and see if less torque is an option.  This could be done by printing new pulleys.  but what I sacrifice in torque and gear contact - may manifest undesirable slippage on the pulley. Given the results of the 18V testing, the best option will be to use a gearbox to increase the torque of the wheel, and reduce the speed/impulse of the motors.

Next Steps - The gearbox for printer motors is already in progress.  The initial results of that design are very positive. I will be replacing the motors in Tilt! with new gearbox driven versions.


in other news:

This guy has a good page on balancing robots:  Axel's FYI Balancing Robot

And this video is typical.


Saturday, May 29, 2021

Three Year Anniversary



As of May 27th, this Totally Not Evil Robot Army Blog, is three years old.

in the last 12 months, the blog has had over 31,000 views. and for all time about 45,000. Perhaps the global lockdowns have created a few more page hits. This year, over 50% of the page hits have come from Hong Kong, and another 10% from Indonesia. Perhaps a new robot hot spot?

It is clear that many russian website have been linked to mine. They are trying to create a web of references to increase the search engine optimization for their own customers pages.  However, I delete these messages as soon as they arrive, but that does not keep the internet-troll-robots from linking to me.

There are now ~80 blog posts on the record. The most popular pages are still related to Mojo the robot dog. Specifically, the discussion on alternative leg designs. I am hoping someone can make some good use out of this.

For the past year, the focus has been on two robot designs.  Tilt! is a balancing robot and Milli is a millipede robot with a special metachronal rhythm. Like most of my robots, i run through multiple design iterations, typically leaving projects open for future insight or development. This is certainly true with the last robots. Tilt! does actually work, but is not stable (ha ha) due to belt slippage. And Milli or WildWorm is also working but has some torque issues.  Both robots will use my new gear box design and portable power.

Sprinkled in with the robot development is some observations from the internets and humor where it can be found.  Enjoy and let me know what you think in the comments.

Cheers!

Düsseldorf Doug

Monday, May 24, 2021

Desert Robot Project

 

Sonoran Desert - Arizona, USA

My new objective for remote robot exploration in collaboration with Patterntology

Exploring Robots:  Desert Robot Project

Living in the desert, watching what is going on around. An Internet <=> Reality interface/portal. It is a true remote sensing platform that is self-sustaining. It needs protection from the harsh elements of sun, rain, dust, and animals. It has to have the right scale to move and manipulate. but most of all it has to have the ability to see and sense and to communicate this back to the digital world.

This post is a collection of thoughts on what a Desert Robot could potentially be.

Functionally:

It will be a remote sensing platform, with the ability to move, manipulate, and communicate. This is the basic function of all of the probs we have sent to planets, asteroids, and space. But, these robot will be for earth.

It is clear that all Exploring Robots will have the common requirements of:

  • Sense the Environment (vision,hear, temp, smell, feel, etc)
  • Manipulate the environment (possibly)
  • Move (preferably)
  • Communicate its finding, take commands
  • Process the above, as well as manage itself
  • Power: preferably renewable and storable, and portable
finally, all of the other requirements are all about surviving in the environment they are destined for.

Non-Functional:

outside of the primary functions, the non-functional requirement is to survive. It needs to survive the punishing environment that is not particularly kind to electro-mechanical systems.

Desert Robot surviving means managing these aspects:

  • Intense Sunlight, Ultraviolet and Infrared Radiation
  • Heat in excess of 45c, or below freezing
  • Dust and Sand
  • Rain, monsoon flooding, potential immersion
  • Desert animals - PackRats!  Insects and critters
  • People - that want to abscond with our dear robot

Form:

Shape - the robot could perhaps be some robotic cross between a tortoise and a crab. It would need a hard outer shell for protection and to encapsulate the internal electronics. The bottom would need to be smooth, like a tortoise so that it could slide over rocks and obstacles. A bio-inspired outer shell would be ideal for protecting the primary components.

Mobility - choices on types of movement would need to be adjusted by how far and over what terrain is planned. For the first iterations, I am considering that the robot should be able to move and manipulate, but that it would not travel over long distances. Being constrained to just a few dozen of square meters would allow the focus to be on desert wildlife instead of unexplored terrain or vistas. If this is the case, it would be possible to use some small legs that could drag the robot, instead of wheels or treads. small, stout legs can be implemented with a few simple servos and would not require a large power source.

Scale - how large should this robot be?  That would be a function of the energy budget available and what obstacles it would need to overcome.  On the desert floor in the Sonoran Desert, for example, there are many branches from plants and cactus that would need to be maneuvered around.  The size of the solar panels needed for operations and communications would also need to be considered.

What other design considerations should be made for a Desert Robot?

Please leave your thoughts and questions in the comments section below.

Sunday, April 11, 2021

Gearboxes for Recycled Printer Motors (1)


Typical brushed DC Motors salvaged from old printers
part 1

I love to recycle old electronics and printers for parts. I find taking old printers apart is a fascinating way to learn the mechanics of robots. I now have a nice collection of small 9v, 12v, and 18v brushed DC Motors. This is the basic mechanical part of robots! However, using these motors has proven to be difficult as they often have a high rotation speed and low torque. For robot projects, you typically need the opposite, slower rotation, and high torque.  The only way to achieve this is to use a gearbox with the motors. Gearboxes use the mechanical properties of gear-reduction to reduce the rotational rate and increase the torque.

Now it is the time in my robot development to build an accessible gearbox that will work with my projects and recycled motors.

I have worked with gear reduction on a few projects.  notably the tank track and wild weasel drive. Discussions about Planetary gears.  More recently with Tilt!, using the motors with a belt.

Here is a nice Instructable that i am using for inspiration, "3d Printed Gearbox for Small Dc Motors". It does not mention much on the actual design/engineering of the gearbox.  But, it is a nice video and a good place to start.  There are plenty of other YouTube videos that also show the capability of 3D printing gear boxes. Remember, it is far too easy to spend (waiste?) time watching others make videos, then just doing it yourself.  ;)

Starting from the Beginning

What do I need?  (Functional Requirements):

  • must work with recycled printer motors 
    • brushed 9-12V motors 
    • bare metal spindle
  • 16:1 or better reduction and torque
  • minimal backlash (movement in the output shaft)
  • keep the dimensions to less than 1.5 to 2 size of the motor

softer, but important requirements:

  • something easy to print, use, and maintain
  • reliable, not prone to jamming
  • No stripping of the motor gear interface

The concept:

the motor spins a series of gears, each time a small gear with ess teeth drives a larger gear with more teeth. each stage reduces the rotational rate of the gear that is being driven. There needs to be 4-5 of theses connections. finally it is connected to an output shaft. This is all contained on just 2-3 axels, contained in a box, and bathed in grease.

Let's start with a basic gear:

I am using OpenSCAD for my designs.  For gears I highly recommend the Getriebe.scad library from Dr Jörg Janssen, he rocks!  It is written in german, but hey? what's wrong with that? ;)

The primary gear will have a large and small gear physically connected. I am starting with 14 and 28 teeth (a ratio of 2) with a modulus of 1.0 (relation between teeth and diameter). I will also use a angle on the teeth on the gear, to help reduce the gears from raising up on their axles when spun at high speed.

Gear v1

Stacking the next gear:

so the big design question, is what is the separation of the gears? this should be the diameter of the large gear minus half the diameter of the small gear plus some tolerance. Now a good engineer will be able to calculate the tolerance needed based on the 'pressure faces' of the gear teeth.  however, I am not that engineer today and my 3D printing lacks some precision, therefore I am going to start with 0.5mm. ;) 

Stacking the next gear in place

Full gear stack:

Next, add the 3rd primary gear to the top of the first axel. 

For the motor gear (Red), I am using the same gear configuration as the small gear, but making it 1.5 taller than the standard gear height.  

For the output shaft gear (Green), I am using the same gear configuration of the large gear, but will add a shaft on top of it. For this first build a version, i will just print the shaft as part of the gear. However, this is not good design. The shaft should not be printed, ideally it will be a different material, preferably metal. In fact, this is the weakest part of this design so far. Load bearings should be added to this shaft to absorb the load of the shaft and translate it to the box (or any other non-moving part of the assembly). For now, I will print - it is fast and this is more of a "pathfinder" exercise.

Full gear stack

The Box

The gears will be placed inside a box. It will be important to keep the gear from getting foreign matter jammed in the gears. Also, the gears will need some lubricant grease, which will be messy. Most important, the box will provide the structural strength needed to hold the gear axels in place. On one side the motor will be attached. On the other side will be the output shaft and associated load (a bearing would be ideal, next version).  In addition, I will add some mounting holes, so that I can bolt the gearbox to my robot creations.

My first design thoughts are to have the motor and the gears attached to a plate that can be screwed on to the box. The rest of the box will be just the compartment, output shaft hole, and mounting support. This part of the box can be printed 'upside down' (see diagram).

"top view" (no top plate) to make sure all the gears fit

The CAD view, can be used to visually determine if there will be issues with the screw placements.  In this next view you can see the motor (in blue) will over lap the screw positions for the motor plate, as a result, I think i will lengthen this side of the box to compensate. (I also have an issue with the wall placement on the right side)

Use the CAD views to verify the design

Full Design

drafting out the box and all of the screw holes, will complete the initial design.  Now it is time to review the CAD drawing, look for flaws (like forgetting the primary axel holder in the output_shaft_plate). After some adjustments it looks like this:

First full design

Time to start 3D printing and testing

The first results - work, but leave a little to be desired. I assembled the motor, gear, and the three primary gears together. I used nails as a quick axel. Hooking up about 8V of power, it gave it a quick spin. It does work! This test was outside of normal operating conditions as it will be enclosed in a box and axles will be supported on both ends.  The operations were a little rough (no grease!). Therefore I did not post of video of it.  Here are some pictures.


Gearbox version1, first print

Gearbox version1, top view

Next Steps

For the next steps on this project, I will be making adjustments and some improvements. Primarily I will reduce the number of teeth, and increase the modulus. This should result in a similar sized output, but with less teeth. I believe the lower number of teeth will print easier on my 3D printer. I may also add a few mm to the size gears as well. Check back to see on the next post.