auto page turner prototype

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LeissKG
Posts: 6
Joined: 04 Mar 2014, 00:52

Re: auto page turner prototype

Post by LeissKG »

StevePoling wrote: In the video, pages are turned from right to left, and I wonder about two things:
1) what prevents two pages on the right from sticking together and being flipped simultaneously?
Nothing.. This is the major problem of all automatic page turners. A method that minimizes this effect is blowing an air blast at the edge of the page block. This will probably separate pages that stick together. During this you have to prevent that some pages are turned by the air alone. I would mount the air nozzles at the platen. Then i would rise the platen a small amount from the book, blast the air, wait a moment to let the pages settle and than rise the platen fully.
A better way would be to fix the top page with a slight vacuum to the platen and the to rise the platen a little bit. If you now direct an air blast at the page edge the other pages should be moved down at the page block again. This would require either a scissor movement of the platen or a vacuum that is large enough to lift the page but low enough to still allow it to slide down on the platen. Otherways you would tear the page apart..
2) After the page is turned, what prevents additional pages from falling over from right to left before the platen can be lowered?
For lose bound books gravity. But if there is tension in the spine from the binding of the book this or something equally evil may actually happen.

A possible solution would be a second little finger that turns in the opposite direction. The big finger separates the pages a bit. Than the second little finger is turned in fixing the rest of the page block. Then the original finger turns the page. It may be difficult when the second finger only turns on an axis. Ideally it would move inward and than turn to fix the page block.

Another option would a double finger that opens like a scissor. Move this finger inward until it is in the gap that is produced by the movement of the big finger. Then open it. Lower the platen while the finger is still between the pages. Then close the scissor fingers and remove them from the book. finally lower the platen fully.

Another failure mechanism with such books would be that the already turned pages would flip back when you rise the platen. This would require further fingers that retain the page blocks on both sides when the platen rises. This would only work if this fingers fit in gaps in the platen because the edges of this books would follow the platen while it rises and you could not insert an external finger between book and platen.

A page turner with no errors will not be easy to build. But something that works with the major part of the books may be achievable .

Klaus Leiss
dtic
Posts: 464
Joined: 06 Mar 2010, 18:03

Re: auto page turner prototype

Post by dtic »

Cool, my hand is on youtube! :)

Klaus: Thank you. So this would be a good buy then, right? http://www.arduino.cc/en/Main/ArduinoBoardDuemilanove

Yes, the small finger needs almost no force. Searching now I see tiny RC servos for as little as 4$ , like this. I'll get one and test it.

Full automation also involves platen up/down movement. That's where most force is needed. Any suggestions on servos/motors that can do the job and fit the arduino? (Google shows many guides on how to mod RC servos to 360 motors. But would that be enough for platen lifting?)

Steve:
1) I kept tweaking parameters like the angle of the finger, the pressure (from the sinker), where on the page and how fast the finger hits until I repeatedly got one page grabs. I have not detailed measurements to give or explanation of exactly how it works. But I do think this is a really challenging step. An improved device needs to have some easy way to adjust such settings for different sized books with different types of paper. I've so far only tested on ~10 textbooks and novels all with sizes and paper similar to the textbook in the video.

I think adding one more small drinking straw finger can help here. When I, prior to the big finger movement, manually add very light vertical pressure on the lower right corner of the right hand page with an extra drinking straw (and keep it there) then the one page grabs go through more reliably.

2) nothing apart from the the angle of the book. It hasn't been a problem in my tests. But I can imagine that it would be in some cases. (Maybe especially for fragile books where you can't do some "back stretching" before scanning?). The third finger idea above might solve such problems too.

edit: ah, I now see that Klaus just posted some similar thoughts. The scissor is a nice idea!
LeissKG
Posts: 6
Joined: 04 Mar 2014, 00:52

Re: auto page turner prototype

Post by LeissKG »

dtic wrote: Klaus: Thank you. So this would be a good buy then, right? http://www.arduino.cc/en/Main/ArduinoBoardDuemilanove
Yes and no. It is the standard board from the developers of the Arduino concept but the clones are usually cheaper. One thing to watch out for is that many clones left off the USB interface and require a FTDI Breakout Board or cable.. This makes sense if you have more than one project which do not communicate with a PC outside of the software development.
dtic wrote: Yes, the small finger needs almost no force. Searching now I see tiny RC servos for as little as 4$ , like this. I'll get one and test it.
I this should work. I am not current on servo prices, I quoted the first that I found at my usual vendor.
dtic wrote: Full automation also involves platen up/down movement. That's where most force is needed. Any suggestions on servos/motors that can do the job and fit the arduino? (Google shows many guides on how to mod RC servos to 360 motors. But would that be enough for platen lifting?)
While a modified servo may have the easiest control interface, it is probably wrong for this project. While bigger servos should have enough torque to move the platen I think they have no holding torque if the motor is stopped or the platen is in the down stroke. This requires a self-locking gear like a worm gear.

Probably the easiest way for a beginner may be a stepper motor with enough holding torque for the weight of the platen. Suitable stepper motor controllers can be bought at SparkFun and other vendors. A point to watch out for is that there are two types of stepper motors and controllers, unipolar and bipolar. Controller and motor must be of the same type. I would use a controller with current limiting and an motor with a lower voltage than my power supply since this will allow to drive the motor faster. If your controller has no current limiting your motor voltage must be equal or greater than your power supply. For further information see Control of Stepping Motors by Douglas W. Jones .

You will also need a switch or photo interrupter that tells you that the platen is at the upper stop. Another switch on the platen is used to detect that the platen is on the book

Klaus Leiss
dtic
Posts: 464
Joined: 06 Mar 2010, 18:03

Re: auto page turner prototype

Post by dtic »

Klaus, thanks, very helpful feedback! I hadn't thought at all about some of those things. Still, I'll start by just ordering a Arduino kit and some RC servos and see how far that takes me. With the stepping motor as a fallback solution.

Here's how I'm thinking:
- I realized I can add a platen counterweight like on this build.
- The drawer slide I use has a weak "click lock" at both end positions. Given counterweighting that "lock" might keep the platen in place at the top by itself.
- If I add some friction to platen downward movement then gravity might be enough for it (it will slide down by itself but not fall down and damage the book)
- Timing all the movements well (in arduino) might make platen position sensors redundant.
LeissKG
Posts: 6
Joined: 04 Mar 2014, 00:52

Re: auto page turner prototype

Post by LeissKG »

dtic wrote: Klaus, thanks, very helpful feedback! I hadn't thought at all about some of those things. Still, I'll start by just ordering a Arduino kit and some RC servos and see how far that takes me. With the stepping motor as a fallback solution.
I wish you luck. It is entirely possible that it works. It depends on the friction in the system.
Here's how I'm thinking:
- I realized I can add a platen counterweight like on this build.
- The drawer slide I use has a weak "click lock" at both end positions. Given counterweighting that "lock" might keep the platen in place at the top by itself.
- If I add some friction to platen downward movement then gravity might be enough for it (it will slide down by itself but not fall down and damage the book)
- Timing all the movements well (in arduino) might make platen position sensors redundant.
A friction lock is a nice idea, i did not think of that. Maybe i look at it to much in a industrial context.
Now some further thoughts
  • If the force of your click lock is not big enough you can add a magnet that keeps it in the lock position
  • You could add also a brake for the down stroke only e.g.: Some small servo that presses a rubber pad against the slide. Or some small DC Motor that is shorted with a resistor or has a small voltage applied that wants to turn the system upwards.
  • With a stepper the sensors are redundant already since you should know where the platen is. The upper sensor is a safety feature that should prevent damage to the fingers if the platen does not move up. The lower is for faster scanning. You will not have to wait by a safety margin since you know the platen is down
Since a mechanical system is not stable over time the speed of your movements may vary after a while. Without sensors you will have to add ample delay at certain points in the movement of the system to be sure that all is correct for an unattended scan. The sensors allow to omit this delays.

Klaus Leiss
Tim

Re: auto page turner prototype

Post by Tim »

dtic wrote: To later on get a device that can autoscan a whole (thick) book some automatic mechanism would also be needed for both moving the book holder sideways (for the platen to keep hitting center) AND to adjust the big finger slightly since the book's right hand side "page pile" is higher when scanning the beginning of the book and that affects where the finger hits the page. If it gets close to the right edge or to the center then the page grab fails.
This doesn't seem as hard to solve as the other issues you have surmounted. Since page turning moves pages from the right to the left you need to move the book slightly to the left with each page turned. Not only will this align your platen with the spine of the book, but it will move the right stack of pages back into position for the big finger since moving to the left will move that stack by the amount that was lost because of pages that were turned (removed from the right stack). I'm not sure I'm explaining this well, but basically I think moving the book to the left at the correct rate should keep the stack of pages that needs to be turned in constant correct tension with the big finger.

If you did it with a stepper motor and were precise, it would essentially amount to measuring the thickness of the pages to be scanned and dividing by the number of those pages to find the rate the book needs to move left by. It's possible that a lower tech solution such as tension by a rubber band pulling the book to the left will work but that would require something holding back the tension at all times and I can't see how to do that without interfering with page turning.
LeissKG
Posts: 6
Joined: 04 Mar 2014, 00:52

Re: auto page turner prototype

Post by LeissKG »

Tim wrote: This doesn't seem as hard to solve as the other issues you have surmounted. Since page turning moves pages from the right to the left you need to move the book slightly to the left with each page turned. Not only will this align your platen with the spine of the book, but it will move the right stack of pages back into position for the big finger since moving to the left will move that stack by the amount that was lost because of pages that were turned (removed from the right stack). I'm not sure I'm explaining this well, but basically I think moving the book to the left at the correct rate should keep the stack of pages that needs to be turned in constant correct tension with the big finger.

If you did it with a stepper motor and were precise, it would essentially amount to measuring the thickness of the pages to be scanned and dividing by the number of those pages to find the rate the book needs to move left by. It's possible that a lower tech solution such as tension by a rubber band pulling the book to the left will work but that would require something holding back the tension at all times and I can't see how to do that without interfering with page turning.
In a manual system the cradle is centered by the platen. You can do the same on an automatic page turner provided you mount the page turning mechanism on the cradle. This way you introduce no additional forces into the cradle that could move it. If your construction does not allow for that, you have to lock the cradle during page turning . After you unlock it the platen will center it again.

Klaus Leiss
Tim

Re: auto page turner prototype

Post by Tim »

LeissKG wrote: In a manual system the cradle is centered by the platen. You can do the same on an automatic page turner provided you mount the page turning mechanism on the cradle. This way you introduce no additional forces into the cradle that could move it. If your construction does not allow for that, you have to lock the cradle during page turning . After you unlock it the platen will center it again.

Klaus Leiss
But if you mount the page turner on the cradle, then you still have to find a way to adjust it for the pages that have been turned and that reduce the tension of the page turner against the book.
univurshul
Posts: 496
Joined: 04 Mar 2014, 00:53

Re: auto page turner prototype

Post by univurshul »

Outstanding work!
LeissKG
Posts: 6
Joined: 04 Mar 2014, 00:52

Re: auto page turner prototype

Post by LeissKG »

Tim wrote: But if you mount the page turner on the cradle, then you still have to find a way to adjust it for the pages that have been turned and that reduce the tension of the page turner against the book.
You are right here. If the page turner is mounted outside the cradle but the cradle is centered by the platen you eliminate most of this adjustment problems. So a movable cradle that can be locked during page turning is possibly the easiest solution.

Klaus Leiss
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