Electric Wheelchair Makes A Great Base For A Big Robot

Wiring into the joystick is a quick and easy way to hack in custom control to a wheelchair.

Building robots can be fun, and remains a popular pastime among many in the hacker and maker set. However the hardware side of things can be daunting. This is particularly the case for those attempting to build something on a larger scale. A great shortcut is to start with a robust mechanical platform from the outset – and using an electric wheelchair is a great way to do so.

[Nikita] started this project way back in 2009, after finding a broken electric wheelchair at a flea market. It was no longer in fit condition for use as a wheelchair, so [Nikita] was able to score it for the low price of just $50. That’s a great price for a package which includes a robust chassis, wheels, motors and the required controllers to drive it all. With the platform in hand, it was time to get hacking.

Thus far, [Nikita] has gone so far as to strip the wheelchair of all extraneous parts, leaving it as a motorized carriage. Radio control has been implemented with the help of an Arduino, and a couple of “eyes” have been added to give it a little personality. It can also still be driven with the original joystick, which has been relocated on the chassis. Future plans involve adding a level of autonomy to allow the ‘bot to navigate waypoints and recognise faces, both tasks which should be significantly easier with 2019 technology. We’re eager to see where it goes next; we’ve seen great applications of wheelchair hardware before, after all. Video after the break.

26 thoughts on “Electric Wheelchair Makes A Great Base For A Big Robot

  1. The folks who build Daleks at the Milwaukee Makerspace use electric wheelchairs to provide motive force all the time. Some are remotely controlled, some have a person riding inside.

  2. I built one myself recently. Take the brakes off the motors, wire up a sabertooth 2×60 and an RC car tx/rx, and done! Was the easiest RC thing I’ve built so far. It pulls a trailer to take the trash to the dumpster and move stuff around, and pulls a trail mower to mow my huge tracts of land :-). I was going to build a TARDIS shell for it, but OMG Dalek….
    If you’re wondering what to do with the leftovers, I donated the spare parts (seat, frame, controller and joystick) to a local repair shop that does free repairs for a medical ministry.

    1. I have a large wheelchair base exactly with that in mind :)

      I have a conventional dual motor drive and have aquired one that uses a single motor at the rear running a diff similar to a mobility scooter and the stearing is done via actuators on the front wheels

    2. – I have/built one that is still alive and kicking after 5+ years, works great. Mount batteries low between rear wheels and can handle about a 45 degree hill. Can usually find cheap old 24V electric mowers that have shot batteries that pair nicely with 24v drive wheelchair bases.

  3. Didn’t read the article yet but I have been looking for someone to help me on my sticking point for the same project of keeping the joystick and stock motor controllers in place. Most projects ditch the brakes and such from the motors and replace with SabreTooth’s. The proprietary signal sent through the joystick doesn’t play nice with PWM that I can tell and had my project stalled. I am looking forward to reading all about this. Major point for me was keeping most of the stock electronics in place because I liked plugging it in to charge the batteries.

    1. I hacked the joystick on one of these. The joystick has a couple of connections. 5V, GND and then X/!X and Y/!Y – Outputs are driven opposite, so when X goes higher, !X goes lower. It’s a “fail safe” system. I tricked it with an Arduino and generated 4 PWM signals and made sure they tracked nicely and then simulated the joystick being moved. A bit of filtering on the outputs made a nice DC level the controller in the joystick liked. The comms . from the Joystick to the motor controller was some “DX-bus” (CAN-bus) that i didn’t want to mess with.

    2. If it helps – I opened the controller up and worked my way back from the output/power stage, to drivers, to controlling micro/cpu. Cut existing controller traces, and you can drop your own PWM into the output driver stage. Can spare you the expense of a SabreTooth or similar if you have a stock motor controller available.
      – Or my other two cents for hacking an existing controller – digital potentiometer’s are cheap and easy to use with a micro to keep yourself mostly isolated from existing hardware. you could connect a digital pot up to the existing joystick pot inputs, and just simulate the stick movements as wanted from your mcu.

      1. Thank you for confirming this tactic.

        I was definitely eyeing the route of chopping out everything before the motor controllers, and just grafting in my own input at that point.
        You can easily input just about anything, if all you need is a PWM signal.

        I might just take the time to bring that out on a lead and make it easy to plug in different control sources depending on where the project takes me.
        RC, sure; robotics next week, sure again…

        1. Welcome! – yeah, would be nice if there was info on the joystick comms protocol around… I didn’t have much luck with that, at least for the vintage/brand of chair I had. – I’ve got another chair and that has large brushless direct-wheel-drive motors, so the controller is a heavy-duty 2-channel sensored brushless controller. Would love to get this usable, but can’t exactly just jack PWM into it. Maybe worth trying the digital pot route on yet… — Also zaprodk mentioned the X & !X pot inputs used – 2 channel digital pots make easy work of these also – just invert the position on the second channel. Used this to play with a prius accelerator sensor a good while back, it used the same X / !X pot sensing to cross-check the signal/wiper position.

  4. Ever since seeing Colin Furze turn one into a remote control trash can and drive it around town startling people I have been watching Craigslist for as/is electric wheel chairs. I have yet to see one that looks old and beat up enough that one wouldn’t still use it as a wheelchair. And the least expensive I have seen is $300! Most are much more expensive than that.

    I guess I could go to flea markets like Nikita did but it seems like a rather specific item to hope for. How many might I have to go to before finding one? Is there a better source of old electric wheelchairs out there that I should know about? These things have to go somewhere when they are no longer worth servicing right?

    1. Hospital physiotherapy/ occupational therapy departments would be the place to start – they often have a loan equipment department that often deals with them.
      They have an operational life of only a few years after which it is often not economical to reuse them and they often get dumped.

      That’s my experience from working in the industry in Australia. Other places may have different procedures.

      Get to know your local service agent for mobility products, help out, do some repairs and you’ll most likely end up with a few.

      1. I just picked one up for free from a power chair repair shop’s scrap pile.
        The batteries appear to be toast, but they’re just U-1 deep cycle batteries, and can easily be replaced with standard U-1 small engine batteries if you aren’t worried about the run time.

        Much like a few others here, I have learned that the controller and the joystick module have an interlock between them, so I haven’t decided to ditch it yet.

          1. The one that I got used 12V 32Ah U1 batteries, so they seem to start around $99 each, and it takes two.
            Needless to say, I’m not jumping to grab any until I test that the rest of the equipment works, first!

    2. At my local hackerspace, we’ve obtained about five of these over a few years. When a wheelchair reaches end of life, it is sent to a place where it is supposed to be taken apart and sold for scrap. If you happen to know someone who works at such a place, you can sweet-talk your way into getting a few of those.

  5. Boston Dynamics is famous for making robots that move like graceful cheetahs.
    Imagine an army of robotic cheetahs taking over the world.
    Scary!

    That’s awesome but they have nothing on Nikita.
    Nikita makes robots that move like Walmart shoppers!
    Imagine an army of robotic Walmart shoppers taking over the world.
    Don’t you miss the Cheetahs‽

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