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Author Topic: Suggestions for Motorizing mannequin arm  (Read 2963 times)

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Offline RainManTopic starter

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Suggestions for Motorizing mannequin arm
« on: March 15, 2015, 10:34:56 PM »
Hi all , I am building a full scale Terminator from the T2 movie which is the battle damaged version . I really think it would freak people out if I was to have the Endo arm animated ,to have movement in the shoulder and elbow . It must have enough strength to move in a leather jacket .
I have worked with servos in the past and operated them with a Parralax stamp which does PWM .
I did look at an option for a strong servo at Servo City , where the servo is attached to a gear to give it a lot of torque and 90 degrees of movement .
I haven't worked with stepper motors and am not sure how fluid there movement would be . I need 180 degrees of movement max . I understand you can buy stepper motors that brakes when it stops , which would be beneficial when power is removed.
Here's the option with a servo that I was thinking about trying for the shoulder and elbow joint


https://www.servocity.com/html/spg800a_standard_rotation.html
« Last Edit: March 15, 2015, 10:36:33 PM by RainMan »

Offline mklrobo

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Re: Suggestions for Motorizing mannequin arm
« Reply #1 on: March 16, 2015, 06:57:48 AM »
 :) Hello!
I would offer an opinion.
I have recently found out that most servos require a pulse 1/60 of  a second to remain in their
position; if not, any movement become erratic.
Geared- down motors have the power you need, but do not lock when power is not given.
(my experience with those types of motors)
However, I am sure, somebody, somewhere, will sell the motor you are looking for.
If you find them, please post the info to me; I would like to know too.  ;D ;D

Offline RainManTopic starter

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Re: Suggestions for Motorizing mannequin arm
« Reply #2 on: March 16, 2015, 07:11:38 PM »
https://www.servocity.com/html/vertical_shaft_worm_drive_gear.html#.VQd98RhOKrU

If this had feedback it would rock

Here's the beginning of my build . The mannequin has to be modded a lot . I just threw together quick till I get all my parts

« Last Edit: March 19, 2015, 06:17:29 PM by RainMan »

Offline RainManTopic starter

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Re: Suggestions for Motorizing mannequin arm
« Reply #3 on: March 16, 2015, 08:05:07 PM »
Another option . Although I don't know anything about encoders ? Hopefully I can figure it out and it works with a stamp . Not sure if the motor was moved if it could be put in the same location though as it sounds like encoders tell it how far to move but doesnt know where it is exactly

http://www.superdroidrobots.com/shop/item.aspx/ig42-24vdc-right-angle-024-rpm-gear-motor-with-encoder/1829/

Offline bdeuell

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Re: Suggestions for Motorizing mannequin arm
« Reply #4 on: March 16, 2015, 08:46:28 PM »
many types of motors can maintain a position but the system must be designed accordingly. RC style servos are typically brushed dc motors with a gear reduction, potentiometer position feedback, and a built in feedback control circuit. the feedback loop in a servo enables the motor to actively maintain a position. there are methods of electronic braking but that may not provide sufficient holding force in your case. additionally you can get motors with a break that is controlled like a solenoid.

if you go the feedback control method you may want to read up on PID. you could use an encoder, there are absolute and relative styles. an absolute encoder can identify the current position not just change in position. the best feedback sensor for your case might be a simple potentiometer (easier to read also).

all that said I recommend looking at linear actuators. i think the mechanics will be easier because you wont have to deal with a high torque joint. also depending on the mechanics (if it is a leadscrew) it may be inherently not backdrivable. And of course it would look more like the actuating cylinders seen in the terminator movies.

A worm gear motor would also be a decent choice as they are typically not backdrivable. a good source for these is car window and wiper motors (i have picked up a few for free before, robotics stores/sites also sell them). they pack a lot of power but are relatively heavy.


Offline RainManTopic starter

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Re: Suggestions for Motorizing mannequin arm
« Reply #5 on: March 16, 2015, 09:00:16 PM »
Thanks for the reply . I have linear actuators at home and thought about it , but just not seeing the mechanics that well . I would have to get a piece machined for the actautor to push on by a pivot point . So I think I'll look at other options .
Thought about the wiper motor but again no feed back

I'm really liking that motor in my last post , although I wish it was geared lower like 10 rpm but I think it will run down to 3 by adjusting the voltage .
Just have to study encoders now
« Last Edit: March 16, 2015, 09:02:26 PM by RainMan »

Offline mklrobo

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Re: Suggestions for Motorizing mannequin arm
« Reply #6 on: March 17, 2015, 09:48:02 AM »
 8) Cool!   8)
Awesome job on the terminator!  8)
Great security guard too!  ;D

Offline RainManTopic starter

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Re: Suggestions for Motorizing mannequin arm
« Reply #7 on: March 17, 2015, 05:14:22 PM »
8) Cool!   8)
Awesome job on the terminator!  8)
Great security guard too!  ;D
Thanks . Im used to it now but it scared me a few times when I walked into my living room lol .
As I mentioned it was thrown together rather hastily as I have home renos to finish first . I have the Endo skeleten arm and it should be on the left arm and damaged to be screen correct , but I was debating to do an undamaged Endo on the right side instead and motorized . Tough call . Just received the chest plate and waiting for the knee . It kinda sucks as I have to destroy the jacket , sleeve missing and bullet holes etc .
This is a 1/6th scale but it shows you what he should look like when done . I think motorizing the the left battle damaged arm would be ok ?
Was going to make it go on a timer with the stamp but random would be better yet

« Last Edit: March 17, 2015, 05:20:46 PM by RainMan »

Offline mklrobo

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Re: Suggestions for Motorizing mannequin arm
« Reply #8 on: March 18, 2015, 04:54:41 PM »
 8) Awesome idea animating the left arm. That would
give an impression of more robotic "terminator" action!
 ;D

Offline RainManTopic starter

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Re: Suggestions for Motorizing mannequin arm
« Reply #9 on: March 18, 2015, 05:42:55 PM »
8) Awesome idea animating the left arm. That would
give an impression of more robotic "terminator" action!
 ;D
Thanks , I was thinking that may make for a good effect to . Just gotta figure out the best scenario . I suspect stepper motors would be the best case scenario , but never worked with them before and don't really know how they behave and if a micro controler like my Parallax stamp will control them .
I mean if most robots use steppers it would make sense to use them I guess .
Would be one of the stronger options to I would think

Offline mklrobo

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Re: Suggestions for Motorizing mannequin arm
« Reply #10 on: March 19, 2015, 12:27:47 AM »
  8)  Hello!
In relation to using motors to "animate" the terminator, your are now
integrating robotics into art. This migration, I am sure, will give you
new challenges, with the programming involved. The only idea I can
think of at this time, is to look a the Imagineers at Disney Land.
Some of the attractions have top notch robotics; which involve DC
drives, MCU's, mechanical devices, and assorted electronic devices.
Maybe a Youtube video can help. Good Luck!   ;D ;D 8)

Offline RainManTopic starter

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Re: Suggestions for Motorizing mannequin arm
« Reply #11 on: March 19, 2015, 06:13:30 PM »
  8)  Hello!
In relation to using motors to "animate" the terminator, your are now
integrating robotics into art. This migration, I am sure, will give you
new challenges, with the programming involved. The only idea I can
think of at this time, is to look a the Imagineers at Disney Land.
Some of the attractions have top notch robotics; which involve DC
drives, MCU's, mechanical devices, and assorted electronic devices.
Maybe a Youtube video can help. Good Luck!   ;D ;D 8)
Well I do have a Parallax micro controller , but I haven't played with it for years but I think it has quite a bit of potential programming wise .
I think it's almost coming down to those servos with the extra gear . Tempted to buy a stepper motor though just to play with .
Wish I was a machinest somedays
« Last Edit: March 19, 2015, 06:18:45 PM by RainMan »

Offline RainManTopic starter

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Re: Suggestions for Motorizing mannequin arm
« Reply #12 on: March 20, 2015, 08:05:50 PM »
Ok I wasn't aware they had geared stepper motors . I think this may be the ticket .
I would love to experiment with stepper motors

http://www.hurst-motors.com/lsg35geared.html

Update . I think I need a stepper with an encoder so this option isn't looking good now :(
« Last Edit: March 21, 2015, 12:11:07 AM by RainMan »

 


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