Milli (#7) - Update: Added Steering and Pede-Wheels

Milli is a bio-inspired robot that uses a single actuator to create standing wave motion.

Update: I have been somewhat distracted (as we all have been with this virus), but here is some progress made.  I have added a forward section of the frame to provide room for a steering mechanism.  For the first prototypes, I will use a set of wheels that can be turned to steer the 'WildWorm' in a new direction. This may look like a traditional vehicle, but all of the motive force propelling the robot will still be from the oscillating standing wave motion.  In order to keep the Millipede motif, the front wheels will be made of little feet!

Here is a CAD view of the current design:

Milli in CAD - Single actuator bio-inspired robot 20MAR2020 (OpenSCAD)

and here is the current printed version:

Milli 3D Printed - Single actuator bio-inspired robot 20MAR2020 

Next steps:

• build a system to support a servo for steering
• consider balancing the robot with a 'tail'
• and it still needs a monster millipede head!

Milli (#6) - Many-Many New Feet

Milli now has many many new feet!

Milli is a sinusoidal, bio-inspired Millipede Robot.  It is completely 3D printed and is made of recycled printer parts and a metal cloth hanger.

Apologies for the delay in posting, it has been a busy month working on my startup (non-robot) business. However, this weekend, I booted up the 3D printer and created a whole new set of golden feet for Milli.  81 new feet to be exact! (not quite a "milli" but getting closer)

Milli - millipede robot track - new feet

Mathematically, the new feet should provide more distance ground traveled with the twist of each tread. This will result in an even faster robot!  The additional ground speed will also be enhanced by the additional grip (friction) with the ground surface, resulting in reduced slippage.

Milli Robot - Tread-Track with new feet 3D CAD design

Each tread now support either 3 or 4 feet.  The 3 or 4 treads are interleaved, to prevent the feet from colliding when they are traversing the rotating helix. The resulting sinusoidal motion will spread the feet as it comes to ground contact. Then contract the feet when lifted.  -- Video coming soon!

Milli Robot - close-up of the new track-tread-links

The result of the additional stretch between the expansion and contraction of the feet will result in a faster motion for the (standing wave) motion of the tread. Theoretically, the feet can be extended a bit further, this will be interesting to see in the future!

I am currently working on the 'head' of the Milli Robot. The new version will support axle and wheel-feet (feet-wheels?) to provide steering.  In addition, I need to create a place to stow the battery and controller.

In other news...
This TotallyNotEvilRobotArmy Blog has now had over 10,000 page hits!

Milli (#5) - It's crawling now

The Prototyping of milli is moving - as well as Milli, its self!

The focus since the last post was to find and fix any binding parts of the tread tracks. I have located a specific tread that was not flexing properly, due to it being part of the v3 design and connecting to a v4 tread. I am using screws to act as 'pins' in the track to connect treads together. This is not a good practice as the tread of the screw can bind with the tread. however, if significantly bored out it is permissible at this stage of development.

Milli OpenSCAD - for 3rd prototype test 16 Feb 2020

The other change was to adjust the design of the horizontal stabilizing arm.  This arm converts the spinning helix motion to a moving sine wave. Thus it is essential to the design. Changes included shortening the arm by 8mm and increasing the opening by 4mm. I also noticed that the first tread was binding with the arm, and adjusted the tread to move more freely.

Milli - ready for static testing, full tread length, 18v battery, messy desk(!)

The result - the track moves freely!  At least in the initial trials when I applied 18V to the motor it worked well. I then removed the frame holding the chassis and a quickly put together a simple axle and wheels. This was made by a thin rod and some plastic gears salvaged from a printer. I used alligator clips to hold the wheels in place. I put the robot drive on some carpet for friction and Viola! - the worm drive works!!

Next steps:

• Find that nagging binding point seen in the video
• Thinking on the chassis and covering. How the heck am I going to get a battery on it?
• New tread design with increased movement
• Ability to move on smooth surfaces

Milli (#4) - Prototyping the Wild Worm Drive (New Video)

The Milli project is an effort to build a bio-inspired (math inspired?) robot capable of traversing surfaces that are problematic to other robots (such as loose gravel, shag carpet, and muddy bogs, etc).  And to make it look really cool. ;)

The results of the 2nd prototype are much improved, you can see from the video that the prototype has the correct motion and considerably less friction.

Currently, I have printed 23 links in the track tread.  There is an additional load to rotate the helix, but applying additional voltage the motor resulted in enough torque to spin the helix. (at 18V it is very quick).

Next steps will be to create a rear stabilizer to dampen the effects of the spinning helix.

Milli (#3) - Making improvements

Milli is a bio-inspired robot that uses a single actuator to create standing wave motion.

The Frankenstein prototype was successful enough to indicate that the concept is feasible. The next step is to take the learnings and iterate on the next design as well as create new pieces to replace the Frankenstein parts.

New in this build are:

• a motor mount, with a frame to hold the Horizontal Stabilizer
• a single piece Horizontal Stabilizer
• upgraded tread-tracks (version 4)
• new Helix mount for motor spendel

WildWorm Drive - iterative design (OpenSCAD)

The Frankenstein prototype was becoming 'stuck' due to two combining factors. An astute YouTube viewer pointed out that the Horizontal Stabilizer was twisting which caused the treads to bind on the helix. In addition, the pin in the Horizontal Stabilizer was crudely glued and would obstruct the rotating helix. The new design uses a single piece Horizontal Stabilizer, pictured above in light blue. In addition, the new motor mount will more tightly secure the stabilizer and position it in line with the centerline of Helix's rotation.

The Tracks have been updated to use a screw as the henge pin between the treads. This design, I hope, will create more fluid motion. It will also be easier to assemble and reduce the failure rate the track becoming disconnected.

WildWorm - Underside view (OpenSCAD)

The underside view of the next design iteration shows the base of the motor mount. As you might be thinking, the helix will not be well exposed to ground contact with this design. This is true, it will be addressed in future iterations. For now, I need to verify the easy rotation of the helix. For this, I will need more track links and a smooth stabilizer. 

WildWorm Drive - 3D printed, the new design works much better

[later today...] I have printed the new design and put it together.  The single piece Horizontal Stabilizer was a significant improvement. With a some additional filing on the parts, the WildWorm drive rotates as planned.  I will update with a video of the new design.

Finally, for the Robot Lovers out there.  Ninety-nine years ago, On January 25th, 1921 the Czech play Rossum's Universal Robots premiered, entering the word 'Robot' into the English Language.