Author Topic: Mechatronic eyes for mascot head  (Read 1337 times)

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Offline wyukigTopic starter

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Mechatronic eyes for mascot head
« on: June 01, 2012, 09:59:29 AM »
Hi everyone,
Just hoping to tap into the knowledge here on a project that I've been taking a while to complete.
I am trying to make open-able and closable eyes for my mascot heads.
The thing is, there is very little room for movement behind the eyes.

I have solved the opening and closing construction, take a look at the video below.
Kigurumicosplay.com Blinking mask project, manual blinking achieved.


Two plastic strips behind the mascot head slides in a plastic sleeve to open and close the eyes vertically.

I've been trying to use push-solenoids to push the eyes shut but the plastic sleeves bends most of the time instead of moving with the solenoid's stoke.
And the solenoid's stroke is also about 2cm too short even with already a 2cm stroke.
A Solenoid's stroke seems to be so tiny compared to its body size.
I cannot fit any bigger solenoid into the mascot head or it won't be wearable.

I'm thinking of using muscle wires, but I haven't researched into it.
I've thought about using actuators/servos, but the battery pack and the interface between the actuator and the plastic strip hasn't been figured out yet.

Does anyone have any ideas?
Thanks in advance.

Offline tomcharley

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Re: Mechatronic eyes for mascot head
« Reply #1 on: June 01, 2012, 12:13:36 PM »
Dear Wyukig,

  Do you think that you could switch the plastic pull tabs to go down towards the chin?  You might be able to hook up a chin strap on the ends that would pull the eyelids around.  Then you wouldn't need any kind of actuator.  I'm not sure how you could make it wink, but it should be able to blink at least.
  Otherwise I'm not sure how you can make them move without some sort of actuator.  You said that you were using solenoids, which would require some sort of wiring and (I would think) a more complex control algorithm than a servo.  Micro servos should fit inside the head without taking up too much room.
  To fix the problem of the plastic strip bending you could add more braces so that it can't buckle.  Also, as long as you have a bit of room between the front of the mask and the wearers face, you could shorten the plastic strip and store everything in the forehead.
  Another option would be to put tiny motors to the side of each eye.  They would have a gear on the shaft that would mesh with the sides of the eyelashes.

Good luck!
~Tom

Offline wyukigTopic starter

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Re: Mechatronic eyes for mascot head
« Reply #2 on: June 01, 2012, 12:40:09 PM »
Dear Wyukig,

  Do you think that you could switch the plastic pull tabs to go down towards the chin?  You might be able to hook up a chin strap on the ends that would pull the eyelids around.  Then you wouldn't need any kind of actuator.  I'm not sure how you could make it wink, but it should be able to blink at least.
  Otherwise I'm not sure how you can make them move without some sort of actuator.  You said that you were using solenoids, which would require some sort of wiring and (I would think) a more complex control algorithm than a servo.  Micro servos should fit inside the head without taking up too much room.
  To fix the problem of the plastic strip bending you could add more braces so that it can't buckle.  Also, as long as you have a bit of room between the front of the mask and the wearers face, you could shorten the plastic strip and store everything in the forehead.
  Another option would be to put tiny motors to the side of each eye.  They would have a gear on the shaft that would mesh with the sides of the eyelashes.

Good luck!
~Tom

Thats awesome, you knew whats happening from just that brief description and the video.
I'll respond to your reply part by part.

1) having the tabs be pulled down by the chin is the smartest idea I've heard so far.
I've been trying to use electronics the whole time, i only spent very little time to think about analogue means.
I shall look into it. At least that was a real breakthrough from my stuck situation.

2) The thing about servos and why I tried to avoid it is because of the programming and extra mobo required inside the mascot.
I don't know the programming yet, and I think you mentioned in the last point the servo will need a gear/cog meshing with the side of the eyelid thing in order to work.
Thats a lot of high precision assembly there, might not be as easy as it would seem I thought, and I wanted to find a simple and repeatable process thats why.

3) Preventing the plastic strips from bending, I thought of adding more buckles too.
That would be the natural next step I guess.
The issue I had is that, since the direction of the sliding strips is along a curved surface, there is already a lot of resistance caused by friction.
The small solenoids I have I'm afraid doesn't output that much force.
The current plastic sleeve that its sliding in now is already giving it a hard time.
I must try to find a way to make the sleeve looser I'm thinking.

I'll think of something for an analogue design.
That is a REALLY good idea, you have no idea how good it sounds to me now.
I've tried building and thought experimenting with a lot of electronics means.
But because how rough this handmade mascot head is, a lot of functions that would happen in theory doesn't quite happen in real life.

Offline tomcharley

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Re: Mechatronic eyes for mascot head
« Reply #3 on: June 01, 2012, 02:51:50 PM »
Dear Wyukig,

  I'm glad I could help!  Hopefully the chin strap thing works out for you.
  If you decide to go with electronic actuators instead, don't discount servos.  I'm not sure what you're using to control the solenoids, but I still think that controlling servos would be easier.  You don't need to do the gear thing to use servos.  If you use a long servo horn you can connect the end of it to a pin joint in the plastic strip.  The arcing movement of the servo will approximate the straight line motion that you want.
  Also remember that you can shorten the plastic strips significantly to reduce the surface area that produces friction against the inside of the mask.  Another way to reduce friction would be to put some kind of coating on the inside of the mask (Teflon, wax, etc.), but this seems like more work than it's worth, and it would be susceptible to wear and tear.
  The other thing to think about with electronic actuation is how it is controlled.  Do you want it to just blink every 30 seconds or so, or do you want it to blink whenever the person behind the mask hits a button?  This extra complication might make the manual actuation option that much more appealing.
  I've seen a microcontroller made by Arduino called the 'Lilypad', which is meant to be used on textiles in wearable projects.  I've personally never used it, but it's something you might want to look into if you're adding anything electronic to your costumes (it's washable!).

Keep us updated on your progress!
~Tom

Offline wyukigTopic starter

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Re: Mechatronic eyes for mascot head
« Reply #4 on: June 12, 2012, 06:25:07 AM »
I am just posting here again to give thanks to Tom, who without him i wouldn't have completed the project.

The animatronics in the mask is working now. Video can be found at my Facebook page here:
This is the completed mask with the costumer using it.
http://www.facebook.com/photo.php?v=160142807451425

This is the completed mask, just demonstrating the effect.
http://www.facebook.com/photo.php?v=160022324130140

I'm also writing a detailed report on how the entire project is made on my costuming forum here:
http://www.kigurumicosplay.com/social/viewtopic.php?f=6&t=1090

Thank you Tom,
And with the information shared above, I hope we can keep helping others and receive great help from everyone.

P.S. Version2, any idea for reducing motor size and battery size?
The images of the motor and battery setup can be found in my report in the costuming forum linked above.
« Last Edit: June 12, 2012, 06:27:46 AM by wyukig »

 


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