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Thread: Attachment for Manual Wheelchair that Converts to Powered Wheelchair

  1. #31
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    The FDA stuff will be tricky. The phone app for Twion wheels was pulled by the FDA about 18 months ago with no word of when it will return and lots of Twion owners like me who cannot change a single setting on the wheels as a result.
    T3 complete since Sept 2015.

  2. #32
    Quote Originally Posted by ProPulse View Post
    @nonoise Thank you for taking the time to respond to each question that was extremely helpful!! With respect to the FDA, we are definitely seeing how big of a challenge it will be to get approved. But we are ready for the fight. Also, it wouldn't be power assist. All the user would have to do is push the joystick and the device takes over!
    I am all for the use of a joystick. But are you aware that most or nearly all of us do not have arm rests on our wheelchairs? The wheelchairs we have are not temporary use hospital type tanks. And we don't just stand up and walk away from them at our destination. We transfer sideways from either or both sides so something in the way where a joystick should be would be a problem. What I am saying is keep that in mind. A joystick is ideal, but it must not get in the way. Maybe hinge it to fold under the chair or create a quick release system for it.
    I have had periodic paralysis all my life. I lost my ability to walk in 2011 beginning with a spinal block, which was used for a hip fracture caused by periodic paralysis.

  3. #33
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    Quote Originally Posted by nonoise View Post
    I am all for the use of a joystick. But are you aware that most or nearly all of us do not have arm rests on our wheelchairs? The wheelchairs we have are not temporary use hospital type tanks. And we don't just stand up and walk away from them at our destination. We transfer sideways from either or both sides so something in the way where a joystick should be would be a problem. What I am saying is keep that in mind. A joystick is ideal, but it must not get in the way. Maybe hinge it to fold under the chair or create a quick release system for it.
    Anything that is tethered to the chair (or it's "add-on") makes removing that add-on all the more difficult.

    Any "control" only has to provide directions to the device being controlled -- it's not switching power (directly) or interfacing with mechanisms. So, there's no need for a physical connection between the "control" and the device being controlled. I.e., wireless.

    There are numerous wireless technologies available with different price/power/bandwidth/range points. A chair sits at the very bottom end of all of these (the user isn't more than a few feet/inches from the "controlled device", the data link is reasonably slow, etc.). So, ZigBee, BT/BT LE, WiFi, 900MHz, etc. are all easily applicable.

    For extra points, consider how you might be able to design a "receiver" that could easily be paired with different COTS "user controls" to avoid having to design and maintain those controls, yourself. E.g.,
    https://www.amazon.com/Fucung-Wirele.../dp/B07G2JKS84
    or
    https://www.amazon.com/MOCUTE-052-Wi.../dp/B07D3514M1
    or
    https://www.amazon.com/MOSTOP-Contro.../dp/B07BBFY2Z9
    etc.

    (I am not endorsing any of the above products -- merely indicating that with 3 minutes on google you can find "options"... with the time you have available in your design process, you should be able to do a more exhaustive search and evaluation)

    Do you REALLY think you're going to make ANY kind of control that you can SELL for the prices on the above items? It will cost you MORE than that just to "process" a replacement part order from a user WHEN they need a replacement or repair -- instead, let them just buy "new" from someone else who is already making products for The Mass Market, instead of your small segment of it! Concentrate on the part of your product that is truly unique (you wouldn't waste time manufacturing your own ball bearings, would you? Or, specially shaped batteries to fit sleekly within your case?)

    This also avoids the issue of needing "expansion boxes" to add attendant controls or display devices or ??? later.

    (But, you have to consider, carefully, how you protect the user -- from failures, faults and "bad actors" -- as those will be areas where YOUR design choices will expose YOU to litigation)

  4. #34
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    Quote Originally Posted by Mize View Post
    The FDA stuff will be tricky. The phone app for Twion wheels was pulled by the FDA about 18 months ago with no word of when it will return and lots of Twion owners like me who cannot change a single setting on the wheels as a result.
    Consider "opening" as many aspects of the design as possible so folks aren't dependent on the original vendor remaining a viable business entity "in the long run". Customers often have a different idea of the "expected lifespan" of a product than the suppliers of those products (who, naturally, are looking for repeat sales to remain financially viable).

    The downside of all this is that it makes it easier for "knock-offs" to "steal" your design (sell counterfeits). The downside of BUYING a counterfeit is that you're now at the mercy of People's Wheelchair Assist Device Factory #13 "disappearing" when you need a repair/replacement part.

    Consider, carefully, the cost of making each sale. Don't naively think that your "design" is done (thus, "free") and the parts ONLY cost $X so selling it for 2X gives you a windfall (50%!) profit. By way of example, commodity electronic devices (i.e., things sold in HUGE numbers with very little "sales support/cost") usually are priced at about 3.5X (X being the cost to make) -- and these have SLIM MARGINS.

    Likewise, the cost of providing service/spare parts. Someone has to take that order, answer those questions, package up the item, process the credit card payment, interface with insurers, trace lost packages, etc.

  5. #35
    @Mize I'm sorry to hear that I'm surprised the FDA would have jurisdiction in the app store. Did you pay for the Ywion wheels through insurance?

  6. #36
    @nonoise Do you think it would be better to have the joystick totally separated from the chair? By totally separated I mean, the joystick can come with a wheelchair mount where it is "stored". But during use, the user just holds the joystick in a single hand to control the chair(the joystick is relatively small). This would eliminate the disruption from any mounting arms that would have to be installed. The alternative is exactly what you said, a collapsible joystick mount with hinge or quick release. We could also include both as options and the user can choose what they prefer depending on convenience and motor skills.

  7. #37
    @automation Thank you for the links and all the advice!! It really does help. The issue with Bluetooth is the fact that we would have to add an additional battery to the joystick, which means an additional component that the user has to plug in to charge overnight. In your opinion, is the wireless capability worth that extra hassle (and possible additional point of failure in the system)? You make an EXCELLENT point with respect to avoiding additional processing when common components fail. It will significantly decrease costs and the time it takes to fix issues. Finally, safety comes before anything else for us. There is absolutely nothing that I would put before the life of the user.

  8. #38
    @automation Absolutely. During our start-up competition we realized the complexity of all of these things. It really made us question what price the product should be sold at. We needed to balance being able to lift this company of off the ground, while keeping true to our vision of "Undenied Mobility" to all wheelchair users. That's part of the reason why I came here. I really wanted to know what users would honestly be comfortable paying? How much is too much, where they have to choose between groceries and a product that can truly give back a substantial amount of independence or even just allow users to relax their shoulders for the day. It's tough, especially when just a few months ago we knew nothing about business, only engineering.

  9. #39
    Quick thank you to everyone participating or even just taking the time to read through this thread. I truly appreciate how helpful the community has been. It's exciting to hear about everyone's input on how this product can make lives even just a bit better Edit: *Keep giving me all the advice you've got! I don't want it to seem like I wanted the thread to end lol*
    Last edited by ProPulse; 04-03-2019 at 02:15 PM.

  10. #40
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    Quote Originally Posted by ProPulse View Post
    The issue with Bluetooth is the fact that we would have to add an additional battery to the joystick, which means an additional component that the user has to plug in to charge overnight.
    The battery is already present in the device -- along with the means of charging it. YOU could select the device ("recommended by ProPulse") that you think offers the most convenience -- along with an explanation of WHY you made that recommendation. I.e., "This device offers wireless CHARGING (like earbuds) so no need to fuss with plugging in microscopic power cables each night! (which might be hard for some users)" Note that the fact that it is inexpensive and COTS means users can opt to buy 2 (or 6!) so they can have one on a charger while they use another. Or, have a "spare-on-hand" so they aren't stranded waiting for a replacement.

    In your opinion, is the wireless capability worth that extra hassle (and possible additional point of failure in the system)?
    I've grown to dislike wires -- with a passion. Everyone (designing) always thinks "it's just ONE wire"... but, they forget about all the other wires that are in place, for other reasons. Regardless of how well they try to organize and economize on them, there's always more than you would expect (the "wiring diagram" for my powerchair looks like an inner-city roadmap... "Isn't it just a joystick, motor and battery? Where do all these wires come from??" -- rhetorical question)

    Wires also mean physical interfaces. I have to physically build something (often with a "special" connector that the manufacturer chose for some reason convenient to THEM!) to interface to those "wires" if I want to augment any of the device's capability. I can't just write some code (or hope someone else will write it) to interface to a "virtual" interface -- built on COTS wireless hardware ("Look Ma, no connectors!")

    I use wireless (BT) devices, here, to track the location of "users" (most of which will NOT be in chairs so hanging a custom built, low volume box on their back would be a deal-breaker). This lets the user opt for the amount of money and comfort he wants -- and, gets ME out of the manufacturing of tiny, low margin, high volume, MOLDED PLASTIC devices (i.e., a mold can be $10K+. If you're going to shoot 10,000 parts, that means you've added a dollar to the cost of each part)

    You make an EXCELLENT point with respect to avoiding additional processing when common components fail. It will significantly decrease costs and the time it takes to fix issues.
    Decide which business you're in. Do you want to make tires? ball bearings? joysticks??

    When Kurzweil made the first Reading Machine (mid 70's), you couldn't go to the local Best Buy and purchase a COTS document scanner. Instead, they had to be designed and built, in-house. When you're only making a dozen or two ANNUALLY, you can't take advantage of economies of scale to drive the cost down. You couldn't invest in automation to reduce the time/labor to produce. And, if one of them BROKE, there was no one that the user could turn to other than the manufacturer to get replacement parts (which meant an airline flight to service the device in situ).

    Nowadays, taking that sort of approach (in light of the availability of COTS scanners) would be foolhardy.

    Finally, safety comes before anything else for us. There is absolutely nothing that I would put before the life of the user.
    THIS is what will screw you over. Any COTS device will undoubtedly NOT be validated for the sort of use you intend. And, getting the vendor to make "specials" for you is unlikely as they have little reason to want to incur the cost of the validation effort for the "few" (when compared to their commodity sales) devices that you are likely to purchase.

    OTOH, it can give you a rapid prototyping approach to evaluate the merits of different types of I/O devices without having to fabricate each, yourself. Don't underestimate the number of different "controls" you will have to accommodate (I'm refurbing a "scooter" this week because the client can't use a joystick and needs the tiller/speed control interface).

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