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Assistance with helping boy to draw

  • Ian D Midgley
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(posted by Susan Iwanek

Ian Midgley at the Harrogate and Ripon panel has the following challenge and would appreciate input from members who may have had a similar case. He writes:

We have a case of a boy who is athetoid cerebral palsy with lots of jerky, uncontrolled, random movements all the time. The challenge is to see if we can help him to write/draw. He can just about put pen to paper but can’t draw anything you would ever recognise.

His OT has had some success with his eating using the manual Neater Eater ( ) where it dampens his involuntary movements quite effectively using fluid couplings – which brought her to us to see if we could apply the same principle, but with the added articulation needed to draw/write.  I got in contact with Neater and they used to make a fluid dampened mouse which some people had apparently adapted to take a pen , but they consider that the dampening necessary to write with, would make any device very tiring. They may be right but I found if I supported his hand just a little, it gave him some better control.

What I’m struggling with though is making a coupling that properly dampens, rather than movement being restricted by friction which certainly would be too tiring. That coupling will need to be fully adjustable too, to get the right amount of resistance.

Commercial items already identified/considered are:

1. Able2 mobile arm support – the OT has tried this with a small degree of improvement

2. A magnetic support, but this relies on the user being able to hold the pen against the rest which he will not be able to do at the same time as trying to move it.

This idea would be easy to replicate with some sort of pen holder but the issue is how we then get him to control putting a pen on/off the paper.

3. An aid made in the US which supposedly caters for this problem, but there is very little trace of the manufacturer, reviews etc. so I’m not convinced it would be better than other arm supports.

My best alternative thought so far is a variation on the weighted pens you can get where the pen is attached to his hand by way of a weighted glove/wrist brace, but his movements are likely to be too random for this to be effective unless it was (say) accompanied with a dampended roller ball underneath it which suppresses any involuntary sideways movements.

Ian Midgley

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40 responses to “Assistance with helping boy to draw”

  1. Ian Midgley says:

    My solution came back in for some running repairs recently, which reminded me to post the outcome on here for future reference. See our panel case studies at entitled “writing and drawing aid”.

  2. Ian Tanner says:

    Somewhere in this thread it is mentioned that the lad enjoys the tactile aspect of drawing which ‘remote’ drawing would not have. Allow me to assume, however, that he would enjoy, or learn to value, its novelty. I know nothing about remote arms following a ‘drivers’ manual input but, I assume, the relevant software could have the facility to filter out involuntary movements;handshake at very least*. Maybe a university robotics dept would have suitable software, hardware, and even a willingness to help? (postgrad or postdoc research).

    *I’m wondering whether acceleration, or that combined with direction and distance, could be the basis of an effective filter? I’m just reminded that I recently purchased noise suppressing ‘phones which, I presume, have similar filtering aspects. -v impressive!

  3. Ian Midgley says:

    That was interesting Chris!

    The two motors I had knocking about were MFA low geared units – see

    Mine are the 62:1 ratio variant. If you turn the output shaft there is so much gearing in there, you get a nice dampened feel anyway. With 50 ohms across the terminals, you can feel its having some effect and slighly harder to turn but you don’t feel much change if you turn it faster v slower.

    However, drop the pot down to maybe 10-15 ohms and the difference in the resistance to turning is much more noticeable. Still relatively easy to turn slowly, but much firmer resistance to turning it sharply.

    I’ll need to experiment further but the intial results are certainly encouraging.

  4. Ian Midgley says:

    I’m familiar with that principle now you mention it Chris. I remember fixing up an emergency stop button on a Scalextric controller when I was a kid, which killed the output and put a short to track.

    I have some DC motors floating about and a 50ohm wire wound pot which will do for testing various resistance, so I’ll have a go and see what results I get with it.


  5. Brian Light says:

    A further thought on this if that’s OK.

    A damper system would act by the restraint on movement being proportional to the accelaration of the movement, jn which case the spasmodic movements could not be eliminated, only lessened. An inertia reel (which I understand is like a centrifugal pawl) stops any accelaration over x m per sec squared dead. This is surely what is required, so long as the deliberate drawing/writing movements are fairly slow. If the limit on accelarstion were adjustable, the optimum cut off could be found by trials with the client.

  6. Chris Dale says:

    Ian, One of the properties of small DC motors is that they can also act as generators, and if a short circuit is placed accross the terminals then the faster one tries to turn the shaft the more difficult it is. The effect can be modified by connecting a small resisitance in place of a short circuit. To use this effect to dampen hand movements, linear movements could be converted to rotary by using a pulley system or a rack and pinion. Two systems mounted horizontally at 90deg to each other may be needed.

    I see that you have several other ideas to try, but if you think this idea may work, I could do an experiment for you. (I tried to send a similar reply this morning but can’t see it here).
    Chris Dale West Midlands panel.

  7. Thomas Hinton says:

    How about filtering the input from a drawing tablet, instead of a mouse – this solves the rotational issue, and provides absolute rather than relative coordinates which might be useful.

  8. Chris Dale says:

    Ian, one of the properties of small DC motors is that they will also act as a generator, and if a short circuit is placed across the output, the faster one tries to turn the shaft, the more difficult it is. The effect can be modified by replacing the short circuit with some resistance. These motors may offer a fairly compact system although some sort of pulley system or rack and pinion would be needed to convert linear movements to rotary. Two systems acting at 90deg to each other may be needed.

    I note that you have several other interesting ideas, but if you would like me to do an experiment with motors, please let me know. Chris Dale, West Midlands Panel.

  9. Ian Midgley says:

    Thanks David – I think the theory is sound but as his random movement is pretty much in every direction, engineering it in would certainly be the challenge. I’ll mull that one over a bit longer – thanks!

  10. Ian Midgley says:

    You’re absolutely right Brian. I’m preparing myself for lots of experimentation on this one. If that US arm support was in the UK I’d have risked getting hold of one by post, testing it quickly, and returning it under the provisions of the distance selling regs if didn’t work as promised.

    The seat belt concept is an interesting one – I’ll check what the mechanism looks like and whether it might suit something like this.


  11. David Smart says:

    Perhaps a better approach to the problem of restraining rapid involuntary movements would be to use mass rather than friction. Mass always comes with weight so a conterbalance is required.
    As an experiment try this. Fix a weight to his hand. Attach a cord and run it over a pulley with a counter balance weight on the other end. Adjust this so his hand becomes virtually weightless. If the system oscillates introduce a critical amoumt of friction ( Stiffen the pulley).
    The theory behind this is that while friction opposes movement, mass opposes the rate of change so it will oppose rapid movement more than the slow deliberate actions.
    If that works the next problem is to engineer it into a solution. Over to you.

    Best wishes David Smart (Essex West)

  12. Brian Light says:

    I can see that with some of the commercial solutions suggested, what is needed is just to experiment with the device – but this can’t be done without buying it first!

    Another brainstorm: inertia reel seat belts are a device which eliminate sudden movements but allow slow ones …

  13. Gareth Harris says:

    I was thinking along similar lines to Ken’s 2nd suggestion – a custom drawing program which would apply filtering to the mouse movements.

    I don’t know how to write a mouse driver but I think I could write a very basic drawing program which would draw lines on the screen and I know how to design filters.

    A possible disadvantage is that, unlike a pen, the mouse would need to be kept the right way round (i.e. if it twists 90 degrees moving the mouse up moves the pointer left). Another possible disadvantage is that the filtering would introduce lag, which if it’s too long could get really frustrating.

    A big advantage is that the filter settings could be easily adjusted and there would be no hardware costs at all.

    Does the client have access to a PC and would a mouse be suitable?


  14. Ian Midgley says:

    All – just to update on my thinking.

    Firstly, I have an idea on what I could do around the principle of the commercially available magnetic aid, based on a couple of similar projects I’ve been advised about by Leeds/Bradform and Essex West panels.

    Secondly, now I know a lot more about non-newtonian and damping fluids than I did a few hours ago, I feel much more confident there might be a support arm solution there too.

    But in the interests of expediency, I reckon I can knock together a prototype of the magnetic solution in a matter of hours to rule that in or out, so I think I’m going to look at that one first.

    Thanks for all your replies – much appreciated.

  15. Ian Midgley says:

    PS – just spotted another software solution we identified a while back is still online though, and that is:

    Looks as if it might be compatible with later OS such as Vista and Win7 which is encouraging.

  16. Ian Midgley says:

    Hi Peter, in the case of a liquid, I wouldn’t envisage compressing it – more feeding it through small channels. I mulled over an air based solution but I confess I ruled it out quickly as I couldn’t see how I could handle the degree of articulation needed at joints but I’m open to any ideas right now!

    Not that I have yet solved that problem for liquid either – apart from perhaps the torque converter principle mentioned below, and I can see that being a right pain to make, even if we have now established the sort of fluid that might go well within it.


  17. Ian Midgley says:

    A computer solution is a possibility, but he likes to draw and scribble with his pens just like any other young kid.

    I am aware of some commercial solutions in that area. A client of our panel with parkinsons has one of these which is a hardware smoothing solution sitting in between mouse and PC/mac, originally developed by IBM. I’ve actually tried it and it seems to do what it claims pretty well.

    For XP PCs, IBM used to do free smoothing software which I can’t find online anymore but I have an old copy myself lurking about somewhere. That was OK too if I recall.

  18. Ian Midgley says:

    I think your point is very well made Chris.

    He’s a really lively sole in spite of his disabilities so I really do want to try and sort something out for him. He gets a little frustrated too when his hands don’t do what he wants them too so I’m thinking I might be able to harness that frustration if the solution is right for him. It’s also possible his strength will develop a bit more over time too.

  19. Ian Midgley says:

    Cheers Peter – I notice one company does an evaluation kit so I might see if I can get one!

  20. Ian Midgley says:

    I’m right with you there Ken – I drive an auto and I’d mulled over whether I could re-create a tiny version of a torque converter. Two vaned assemblies turning in fluid with less slip the closer they are together.

    The cornflour idea is a new one on me – I’ll see what Mrs Midge has in her baking cupboard!


  21. Ian Midgley says:

    Thanks Jennifer. I think the problem in this case is his movements are very random plus he struggles to hold and control the pen at the same time. Ideas for me to put in the melting pot though – so thanks for taking the time to reply.

  22. Peter Mitchell says:

    Would a damping system based on air (compressible) rather than liquid (non-compressible) be less tiring? It would also have the advantage of stiffening up the more it is compressed.

  23. Ken McMullan says:

    Some time ago, when computers generally had serial ports, we were able to input data to them which was treated as if it were coming from a mouse or keyboard. If we could obtain a serial mouse, and the end PC had a serial port, it would be reasonably straightforward to make an electronic box containing a microcontroller which would sit in between the two. This box would repeat the smaller, slower movements out to the PC, but would discard the larger faster movements. Total cost of hardware would be under a tenner, but the software might take a few weeks to cobble out.

    Alternatively, if there are any software engineers out there who are more versed than I in modern techniques, it should be very straightforward to write a USB mouse driver which performs teh same function.

    Neither solution would create any undue resistance for the end user.

  24. Ken McMullan says:

    Yes, I was trying to think of how a fluid clutch works in a car. Have you ever mixed up a paste of cornflour and water? I recommend it. It’s a non-Newtonian fluid, which actually thickens up the faster you try to move it. It could certainly be made to damp only the rapid motions while allowing slow movements effortlessly.

  25. Jennifer Shoesmith says:

    As a retired Occupational Therapist, it struck me that perhaps you could use some sort of pen rest, combined with a damping system. I have given you links for two from Nottingham Rehab below. Alternatively, if these were not suitable, perhaps a rest made to suit the client, out of splinting material, could be manufactured by colleagues of the OT involved, and then combined with a suitable damping system.

    Hope this is helpful.

  26. Charles Hawkes says:

    Have you considered. ?
    1. A computer with Windows Paint and a printer
    2.An infrared mouse
    3 Hydraulic damping on the mouse or the wrist ,in the horizontal plane only

  27. Chris Manlsey says:

    The following points come from recent experience of assisting a remap project for a young boy who needed to operate a type of computer pad that needed him to flick with his fingers, when he had just not got the strength to do it, However, wonderfully, he developed that because he found that there was an opportunity for children his school to learn how to play the ukeleli, (presumably someone else fingers the strings for him), and he can now flick quite well. I wonder if this lad might be given enough strength to operate the dampening device that you considered too tiring?

    These ideas come from my my enjoyment of drawing, (and the excitement of realising that the boy that I helped had been able to do something that he had really wanted to do) rather than in relation to making the device to help the boy, – I’m a civil engineer, who just enjoys making things out out woodwork!

    Chris Mansley

  28. PeterP says:

    There is an arm tremor control design at . You might be able to make a smaller hand joint using damping grease – this allows slow movement but damps rapid excursions. eg or

  29. Ian Tanner says:

    Further to my contribution (5 above) suggesting Robotics and Universities:-
    I notice that the Horizon Prog tonight (re cancer treatment) features a robot (Saturday Times preview) “..known as the Da Vinci……By eliminating all hand tremor the robot multiplies the surgeons precision….”

  30. Ian Midgley says:

    The pictures are deceptive Chris – the motor is actually quite small. I can’t turn it on the spindle alone (lack of grip more than anything else!), but I can turn it with just a very small lever on it. I’ll post up the outcome in due couse. Cheers.

  31. Ian Midgley says:

    Yeah – I guess I should have asked them why they discontinued it Ray! I’d assume that for mouse steadying alone, it was overtaken by software solutions (a couple of which are free), and the hardware device from Montrose Secam which is probably cheaper.

    Funny you should mention the dampers – I’m refitting my bathroom and was looking at the clip on ones supplied with a vanity unit and wondering whether I could do anything around them. I’ll mull over that one, and thanks for the pointer an manufacturers. Ian

  32. Ian Midgley says:

    Thanks Ian – we are looking at the computer angle too, ref. my reply below on software that can do a degree of involuntary movement filtering. I gather from the OT that she has had a degree of sucess with Clicker 5 software but he does tend to get frustrated with it, so his high degree of involuntary movement might need a combination of approaches.

  33. Ian Midgley says:

    I’m all for simplicity Jeff ! I think the idea has merit and I’ve had a similar suggestion by e-mail, but having seen the little lad myself, his random movement is quite severe and I think this approach would suit a more predictable tremor in a particualr plane. I’m still evaluation options and wouldn’t rule this out so thanks for raising it. Ian.

  34. Ian Midgley says:

    Thanks John – I passed this info and your photo to my OT to see if she thinks it will apply to particular type of CP he has, and the extent to which he has it. Regards, Ian

  35. Ian Midgley says:

    Many thanks Alberto – I’m still evaluating ideas and getting some bits and pieces together to test a few principles. I’ll have a look into this one too – cheers, Ian

  36. Chris Dale says:

    pleased to know that initial tests with a motor were encouraging. I was rather surprised that a motor with a 62:1 gear box ratio didn’t have too much resistance due just to the gears. Anyway, I’ll be interested to see what the final outcome is. Maybe the drawing board pantograph suggested by Alberto could be coupled to the motor(s) via pulley(s).

    Chris Dale, West Midlands panel

  37. SusanI says:

    I am posting this on behalf of Alberto Molena of the Shropshire panel

    Hi Ian,
    I had some success in the past with a damping system to enable a Remap client wit a partially uncontrollable arm and wrist to use a keyboard by using a wrist support mounted on a form of pantograph.

    In this instance a commercially available drawing board pantograph mounted on a horizontal plane will move freely in any direction and if required can be damped by the adjustment f the existing springs and possibly a felt pad to make contact with the table. Should a suitable small gutter be fitted by way of a swivel point to the bracket of a previously removed horizontal ruler it should support and steady the user wrist to allow a reasonably control movement of a pen/pencil held in his hand. I hope you’ll be able to elaborate on this suggestion and I would appreciate your comments.

    Regards, Alberto (Shropshire panel).

    P.S Should you require further information please don’t hesitate to contact me.

  38. SusanI says:

    I am posting this on behalf of John Moutrie of the Bury, Bolton & Rochdale panel

    John writes:

    We tackled the same problem with a young lady suffering from CP in a different way some years ago.

    The OT had heard that involuntary movements in a person suffering from CP can be reduced or eliminated if the body is supported in a particular way, which varied between one patient and another. We spent some hours using cushions to find the correct body position, where the involuntary movements stopped, then I measured up the body position and designed a special seat which supported the young lady.

    The peculiar shape of the chair supports the lady on her stomach as well as her knees, which are at different heights, and the chair was adjustable so we could fine tune her position.

    In this position she was able to draw very well.

    Best regards,

    John Moutrie

  39. Jeff Lesser says:

    This is a very amateur suggestion but it would cost vitually nothing and could be tried reaonably quickly by the OT. A pen or pencil or suitable holder could be suspended from a spring and weighted to provide resistance to movement. It may be that this has been tried already; if not, it would be simpler to try than some more complex suggestions.

  40. Ray Westcott says:

    The mouse trap idea seems to me to be most promising. Longstroke miniature air dampers at 90 degrees, coupled to a block with a mouse ball would take care of movements in the horizontal plane. Movements in the vertical plane would not require any damping, just a spring loaded pen to keep in contact with the paper. A company called Blum make dampers for kitchen doors/drawers etc – very small. There are others.

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