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Thread: Stick Slip Actuators

  1. #1

    Default Stick Slip Actuators

    Hey there

    I am designing a Solar energy operated Glass cleaning Robot.
    For that i need as much as material possible on slip stick actuators.
    Also i want to know their dealers in India

  2. #2
    Super Moderator T-1000 docel's Avatar
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    I think you have the wrong combination for the task:
    1. Solar energy cannot drive anything run-time.
    2. Glass cleaning is a tricky business. You'll have discovered this if you have cleaned glass anytime by hand. The mechanism needed for it will be quite complicated and expensive.
    3. The Slip-stick actuators are basically vacuum drive devices if they have to bear the heavy machine.
    4. If you are cleaning the Glass, the slip-stick mechanism has to be fail proof, as the very act of cleaning glass is a slippery method.

    Now, the million dollar question is: aRe these Robots practical? Would they really be a serious working Robot useful enough for the myraid types of windows on high-rise buildings?

    There are several points to ponder here.
    1. The biggest point is Safety. Suppose it falls.....
    2. What happens to the resultant muck collected after cleaning? It is difficult to prevent the cleaning agent etc., from running down from above and dirtying the already cleaned windows.
    This requires kilometers of tubes that will weigh a 'ton' in reality.
    3. The Robot itself will itself get dirty after several windows.

    We made a couple of these robots some years ago and concluded that it is impractical to have a glass cleaning Robot other than for demos and technology generation. If the primary intent is automation, then the robot cannot fit the bill at all.

    It will be better to have some detailed discussion in this regard before you take up the job seriously.
    docel
    ^Anything is possible..
    after YOU prove it!!

    http://bangalorerobotics.tripod.com

  3. #3

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    I understand your point that making a glass cleaning robot for automation is impractical and costly.
    I am trying to design this robot as a part of my B-Tech project, and i am not much concerned about its practical utility.
    Right now, i was worried about its Gait, and with this regard i needed intel on slip stick actuators.
    As you said you have designed demos in past, so can you please give me some insight into your Design.It will do me a great help.

    Thanks for your reply and looking forward to hearing again from you.

  4. #4
    Super Moderator T-1000 docel's Avatar
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    Ok, so lets hear about your plan: what do you have in mind?

    Without any knowledge of what you plan to do , it may not be possible to give you any suggestions. If you aren't concerned about its practical utility, as a BTech project, I fail to understand what exactly you want the thing to do..

    It will be appropriate if you can explain the mechanism that you want in one post rather than dropping one hint per post. This will prevent any confusion and help get to the core problem soon. There are others here on the Forum who have tried this too and will help out.

    The simplest I can think of is a reverse hovercraft. All you need is a paper plate , a small motor, a gift-wrapper film and a small propeller.
    docel
    ^Anything is possible..
    after YOU prove it!!

    http://bangalorerobotics.tripod.com

  5. #5
    Senior Member Android
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    Check out this toy, it runs on the principle that doc just mentioned

    http://www.geekologie.com/2008/09/wh..._walls_cei.php

  6. #6

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    1.)The robot will derive its power from solar cells, so power constraints are decided accordingly.
    2.)The robot will have, say 4 legs. Each of these legs will have pneumatic suction pad as end effectors.
    3.) Now at any instant 3 out of 4 legs will be flexed (slip stick actuators may be used for this purpose though we are free to use any other means). The vacuum grip of these 3 legs remains intact. The vacuum at the 4th suction pad (which is not flexed) will then be removed. Because of the flexing, the 4th leg has a stress which it will relieve by moving in the appropriate direction as soon as this vacuum is removed. This will give the robot a small displacement.
    4.)The same step will be repeated for each leg (i.e. all other legs are flexed and one particular leg is de-vacuumed). Many steps like these will give the robot a random motion over the glass surface.
    5) We do not require an active power source i.e. we can wait for the solar cell to build sufficient power before it implements the next step.The speed of the robot is not important too.

    As we are never lifting the legs and the motion is only by removal of suction, the power constraints might be accounted for.

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    Super Moderator T-1000 docel's Avatar
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    Thats a good description of the your design !! Quite realistic too, and can be made to work reasonably with bare minimum resources.

    1. I still don't agree to the Solar cell theory.
    2. You will need 4 motors to move the 4 legs. each motor will weigh around a minimum 60gms, including connectors and wires.
    3. The slip- stick actuators can be those 2 rupee per silicone suction cup meant to stick on glass.
    Now, this is the real problem.... It takes some force to press down for adhesion and some real force to peel....
    4. The Suction pad needs some mechanics to slide and hold, apart from the movement motors.
    The smallest suction cup has a 3kg pull strength. At this adhesive force, it will not slide. Some of the vacuum must be released (partially) for it to slip across but still have some grip.
    docel
    ^Anything is possible..
    after YOU prove it!!

    http://bangalorerobotics.tripod.com

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    Junior Member Newbie yaniv's Avatar
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    @docel
    How about we use suction balls like these as wheels would'nt it t solve the problem? instead of using suction cups on legs ?

  9. #9
    Super Moderator T-1000 docel's Avatar
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    well....... It can be used alright- on an inclined plane; but the problem is that the vehicle is moving against gravity. You need a substantial horizontal force to make it 'stick' to the wall. This will necessitate another force component that is perpendicular to the moving plane. Besides, the ball and its cups are too pliant and tends to be pulled down by the weight of the vehicle in the static phase. This will peel it off of the wall.....
    Last edited by docel; 07-26-2010 at 08:31 PM.
    docel
    ^Anything is possible..
    after YOU prove it!!

    http://bangalorerobotics.tripod.com

  10. #10
    Administrator T-1000 vikas's Avatar
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    1. Solar would not work ... too weak
    2. Clean glass urself as said by Docel ... it aint easy to get good results
    3. The simple suction cups will not work , try buying and experimenting ... they require a lot of force to get a good grip , hard to achieve at an incline by simple pressing.
    4. Best way is to use the technique in the above video , Pumps for each custom suction cup , but such an arrangement is might be highly inefficient like the inverted hovercraft approach.
    Vikas Patial

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