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Old 06-02-2012, 02:06 PM
guskenny83 guskenny83 is offline
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Default appropriate DC motors to fit to a manual wheelchair

hello, i posted this to the projects forum already, so apologies if posting here also is not allowed, but ive had 66 views on the other forum but no replies, so i thought i'd have more luck here..

Hi,

im currently in my final year of a mechanical engineering degree and our final year project is to design and build a smart electric wheelchair, capable of being controlled by a person using only finger movements.

we have developed the control system using an arduino micro-controller, and integrated it successfully into a small-scale robot using two small 12V motors utilising a differential drive method of motion control, and a motor driver based on the L298N chipset from rcubestation.com:

http://www.rcubestation.com/r3cart/i...&product_id=75

my question is about the best way to now advance the project to a full-scale wheelchair.

having a mostly mechanical background, we have not covered that much material on DC motors, so i am looking for advice on the kinds of motors we should be looking to buy for this application, what kind of drivers we should use (im assuming the L298N is not going to be powerful enough) and any general advice people can give on motor attachment or any other aspect to do with the project.

As this project is not actually going to used by a disabled person for extended periods of time, and cost is a very large factor (we are only 2 poor uni students); the more economical, the better.

any information would be greatly appreciated

thanks
gus
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Old 06-02-2012, 03:57 PM
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Bernard Bernard is offline
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The remenants of an electric wheel chair had 2- 22V 250W motors with ? 7:1 gear reduction, & 10 in wheels. Rated @ 15 mph with 300 lb load. More than enough power. Homemaid control, 2 slide pots, manual rev. SW. 3 parallel MOSFETs each motor, PWM speed control. Was prone to blow FETs if speed advanced too fast- even with current control. Second version was never built.
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Old 06-02-2012, 06:46 PM
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BMorse BMorse is offline
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whats up with the multiple threads???? http://forum.allaboutcircuits.com/sh...ad.php?t=70781

I did respond in the other one
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Old 06-03-2012, 12:22 PM
Rbeckett Rbeckett is offline
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A much larger stepper motor or servo motor is your next step. You will also need a much more powerfull driver board. The L293 and other inexpensive boards will not be capable of supplying the needed amperage. If you have not read DR Jones treatise on stepper motors, now would be a good time to review it. If you need a link or copy of that text LMK. If you are using Arduino then you are also using TTL or digital logic and will need an amp or driver to step up the power available to operate the relays or SSR's. Are you using any collision sensors like PIR or Ultrasonic? Probably should look to incorporate it into your over all design too. If you were to produce it commercially you will need passive and active safety systems to avoid a nasty product liability issue. Justa few thoughts from a wheel chair guy (I ride em, not build em). Hope this helps and if you need any additional texts for steppers and or servo I would be honored to share my fairly extensive library on this subject.
Wheelchair Bob
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Old 06-03-2012, 02:11 PM
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Depending on the load the wheelchair may have to carry, you will need some pretty strong gearbox DC motors, preferably 24 volt ones. Like these ones on ebay http://www.ebay.com/itm/Invacare-WHE...b#ht_907wt_174

And the L298 WILL not handle these so you will need to have some kind of high current driver circuits, or a compatible H-Bridge circuit to control each motor, you can use the LMD18201T 3A, 55 volt h-bridges.
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