Disability Midwheel Drive Powerchair Conversion Project.

Jorge PJorge P Posts: 354
Hi all,

This project is quite personal to me, My fiance has Multiple Sclerosis and is confined to a powerchair. She has stated several times, "I wish I could still mow the lawn, Shovel the porch, Sweep/Mop the floor, Vacuume the floor, and dust the house again", things we all take for granted. I am going to attempt to help her do all these things, mostly with items we have lying around the house or can obtain easily. Her current chair has 4 motors to control the chairs seat(full articulation), Upper half. these are all linear actuators with medical ratings. The lower half has 2 separate motors, the Base, to move about. This new char is not part of this project. She has two chairs, the old one is a "Quantum 6000z" power base. This old chair has a broken cable that attaches to the hand controller, the hand controller is also broken. I have seen some people try to diagnose the signals that come from the hand controller to the main computer of the chairs and probe for signals to make their own hand controllers. There is little to no data on the signals and they are usually proprietary signals by the chair manufacturer.

This project will be to replace the main controller that the base uses, so I can use a Propeller, main wheel motor controller(~45amp each wheel), and some sensors to maneuver the chairs base with and/or without human control. The current upper half, which consists of a standard non motorized seat, will be removed and a mechanism will be created to automate attaching different types of custom attachments. All prototypes will be made from wood/aluminum until I can determine the attachments motions, measurements, and lifting/pushing weights. After it is functional the device will be constructed from metal by a metal fabrication shop locally. I anticipate this project will take several months to prototype and complete. If anyone has a spare chair of similar mid wheel drive configuration, I welcome you feedback. Others may be able to purchase a used power chair second hand from a pawn shop but they will most likely need batteries. If the batteries in a used chair are over 1 year old, they WILL need to be replaced. At a pawn shop I have seen several of these chairs sell for 200-300 USD. If you purchase the base from a Pharmacy/Medical Supply company you will pay significantly more unless the unit is discontinued and they are willing to cut a deal to get rid of some scrap. You only need the base frame with the wheels, casters, and motors. Everything else is optional since we can use robotics motor controllers of our own choosing

The drive wheels and motors will remain intact, however I would like to design a bolt on tracked system for outdoor use. Some power chairs drive axles have a 5 bolt pattern, others have 4 bolts. The four casters may need to be removed if you opt for a tracked system.

Attachments (For the Upper Half):
Snow Shovel(or small electric snow blower( Snow Joe 11 inch))
Manual Lawn Mower(Reel Mower)
Articulating boom/arm (custom for reaching and grabbing objects out of reach)
Vacuum/Mop/feather duster holder

Each attachment will have their own batteries, controllers, and charge units. Power inverters will be used for 110V power if the tool requires it (vaccume, snowblower, etc...). Each attachment will have a universal mechanism that will allow the Base to attach itself, lock, and go, this will be a type of cam lock system. A roller switch, maybe a few, will be used to detect placement of the base under the attachment and activate its locking mechanism. The cam style lock is of the type used in furniture and a small gear motor will activate the rotation of the cam to lock/unlock.

The original motor controller/computer is a 100 Amp controller, which is more than double what is needed, even when the motors are in a stall condition. I will be using an Ion Motion Control MCP263 dual 60A 34VDC controller to drive the wheels for the base. All attachments will use various other ION Motion Controllers where a significant amount of weight will need to be pushed/lifted.

The motors for the attachments will mostly be Linear Actuators which will be ordered from https://geek.wish.com as needed (significant wait times). They are mostly aluminum and may not be ideal for the purpose intended but they are fairly inexpensive and will be excellent to prototype with at low cost.

On Monday November 13th 2017 I will purchase the main Base controller, and a 6 channel Radio transmitter/receiver pair. This thread will be updated once I receive the motor controller and have it attached to the motors. I will relay the information Ion Motion Control recommends for the type of motor break used on these motors since this will be done through email or over the phone.

First step is to prepare the base for modification which can be done without any additional parts (see linked post).

Powerbase Preparation
Connecting an Motor Controller
Connecting Batteries
Connecting the Propeller to the Controller
Applying power and first power up
Making the attachment universal mechanism
Making the first attachment
Additional Atachments
Powering the Attachments
6 Channel RC Controller

Jorge P.


  • 11 Comments sorted by Date Added Votes
  • Jorge PJorge P Posts: 354
    edited November 2017 Vote Up0Vote Down
    The first step is to prepare and clean the Power Base and remove everything we will not need, like the seat and original controller. I've taken photographs of tool free removal of the seat on this power chair, other chairs may have similar tool free maintenance options, others will not.

    Step 1:
    Disconnect the hand controller cable from the base controller unit and ensure it will not catch on anything when the upper half it is attached to is removed from the base. Sorry forgot to photograph this step

    Step 2:
    Locate and activate the seat removal lever and squeeze hard, debris and dirt may make it dificult so you could use WD-40 and let it soak a few minutes to break it free.

    Step 3:
    Lift firmly on the front of the chair seat so it rotates/tilts back

    Step 4:
    Grab ahold of the entire chair and pull upwards firmly and remove the chair seat from the base

    Step 5:
    Remove the foot plate by removing the camlock screws

    Step 6:
    Remove the battery access cover, this is a simple lever on each side that just pushes toward the center to release the pins. Once the pins are released pull the metal of the footplate bracket straight up to remove it completely (Do not dispose of this cover it will be needed.

    Step 7:
    Remove the batteries, if any

    Test the batteries in the same manner you would determine if an automotive batter is good, the batteries of my chair were way below 11 Volts they were 7 so they cannot be recovered fully. We will need Deep Cycle, Gell or similar high amp battery.

    Step 8:
    Locate the motor break manual release lever and activate it to free wheel position so we can move the chair unpowerd. When we connect a controller we will need to move this back to drive position before the wheels will spin

    Step 9:
    Clean all removed parts and keep only the ones needed. The foot plate and screws, the seat and hand controller can be sold back to the Medical Supplier that sells and maintains these chairs, it will inevitable help keep these parts available to those that really need them. The battery access cover should be kept since it will be used.

    Step 10:
    Locate and remove the original controller/computer, usually at the back of the base. Keep any brackets for our use but sell the hand controller cable and the original controller back to the Medical Supply companies. Keep battery and motor cables. The covers are usually tool free and have thumb screws, unscrew and remove all cover pieces, then unscrew and remove all cables/connectors to the controller.

    Step 11:
    Locate the battery cable at the back along with the two 4 conductor motor cables and label them appropriately. The motors should be in free wheel mode if you followed step 8 above. We can locate the plus, minus motor wires on the four conductor cables to isolate the break wires by attaching 12 volts and listening for the motor spinning. the two remaining wires are the motor break that will need to be energized before the wheels will spin once back in Drive Mode
    Jorge P.
  • Jorge PJorge P Posts: 354
    edited December 2017 Vote Up0Vote Down
    I received the MCP263 motor controller a few weeks ago. ION Motion listed some part numbers in the manuals and I just placed the order today. It is not required, but I figured I better research the 4 pin motor connectors and the battery connectors so I can keep the original cabling and just store it aside, incase I want to put the chair back to the original condition.

    The power chair had two 73Amp batteries that were reading dead at about 3 volts, thankfully I was able to revive them. It took quite a long time to do this, I pulled a fully charged automotive battery out of the truck and put it in parallel on the battery charger with the 1 dead battery at a time. Took about 6 hours for the supposedly smart charger to charge the 73A Gell cell to a point where I could remove the good battery. After that it took 2 days to fully charge 1.

    The 4 pin connector of the motor is an "Anderson Power" "Power Pole" "15 to 45" connector (45 Amp contacts) with "Standard Housings", they offer what they call "Finger Proof" but those are keyed casings that will not mate with the Standard Housings. The battery connectors are "Anderson Power" "SB-50"'s, grey and black which mate with each other. Surprisingly, they are quite inexpensive! I ordered enough housings, contacts, bonded assemblies, and hardware to continue the project without cutting any wires.

    I also received the Raspberry Pi 3 that I am quite impressed with, along with a couple of nRF52832 boards that I wanted to connect to the Propeller, but I think the base can be completely controlled by the Raspberry Pi 3, we'll see. GPS, and distance sensors will be connected to the Propeller which in turn will communicate with the Pi over its GPIO port, I've used it for this purpose before so I know I have the code floating around someplace. The Pi can't do it all so the Propeller is going to be used for reading all the sensors I have planned. I wanted to use the propeller to communicate with the MCP using packet serial, but I cant find anything for packet serial in OBEX or on the forums, also it will be used to cut main battery power to the controlling Pi, incase of errors. The raspberry Pi apparently can communicate with the MCP directly through USB which is the fastest method so I will tinker with that for now.

    I will update this post in a few weeks when more parts come in. The project total so far, not including the power chair, is about $450-$500 so I am in it till the end now! That doesn't include anything that will be attached to the base as a functional component. Next month, January 2018, I will take on the Linear actuators I will use for the arm motions, 2" or 4" actuators should be all I need as long as I build the cam on the arm, wrist, and fingers correctly.

    In the mean time, I am working on the Python code that will run on the Pi. I am using a python lib called pygame so I can use a standard USB Joystick/Gamepad. Got it working in that respect and the code is fairly small and I am getting the values I need for the MCP controller. Using Wi-Fi and 2 Pi's I can control the base remotely over my local network, or directly with each other. One to stream video of a camera (attached to the base), the other to send the joystick controls and view the video being streamed. That way, my fiance can move it about the house and retrieve, do things, without waiting for someone to put her in her chair when no one is home.

    Slowly but surely it is truckin along!
    Jorge P.
  • Reserved for project step 3
    Jorge P.
  • Updated, lots more to come ;)
    Jorge P.
  • Jorge P wrote: »
    Updated, lots more to come ;)

    That is incredible; I can't wait to see how things progress. There is so little advances on wheelchairs because of no funding interest, so it's great to see this type of project building.

    A buddy of mine has a wheelchair and I help him in and out of a his van; I have wanted to build something for him to make it easier, but getting a spare chair for dev is harder than I thought it was going to be.

    Joshua Donelson
  • This is the Frankenstein Moment! I have about 25Gb of video I have to go through that details the process.

    Now to make a few purchases of sensors to connect to the Propeller and Raspberry Pi. Still alot of work to do :) I'd like to connect 8 PING sensors around it facing about 30-45 degrees downward to detect objects and drop-offs around steps and wheelchair ramps.

    Jorge P.
  • IT'S ALIVE!!! haha :zombie:

    3000A is some serious juice to control. Is the ION motion controller part of the chair or did you have to buy it for this project? Is the PC software from the manufacturer for diagnostic testing or custom? Great to see the progress
    Joshua Donelson
  • JD wrote: »
    Is the ION motion controller part of the chair or did you have to buy it for this project? Is the PC software from the manufacturer for diagnostic testing or custom? Great to see the progress

    I bought the MCP263 for this project and the software on the screen is IonStudio by Ion Motion, the maker of the MCP263. The 3000A 30V interrupt was on the chair connected between both batteries.
    Jorge P.
  • Jorge P wrote: »
    JD wrote: »
    Is the ION motion controller part of the chair or did you have to buy it for this project? Is the PC software from the manufacturer for diagnostic testing or custom? Great to see the progress

    I bought the MCP263 for this project and the software on the screen is IonStudio by Ion Motion, the maker of the MCP263. The 3000A 30V interrupt was on the chair connected between both batteries.

    Nice setup man, those are some monstrous specs, but chairs are unbelievably heavy even without a person, not to mention the draw when going up hill. :nerd: data points... sweeeet

    I learned that getting help with funding on a project for the handicapped were very limited because of the little roi. Billings has plenty of areas that do not have great curbs or super narrow sidewalk entrances in older areas. I was taking buddy into his wheelchair maintenance and got to talking with a lady who was lucky knowledgeable about getting help with funding a project. Getting him in and out is something of an obstacle, and I know technology has a very helpful answer for it. Right now there is a pulley-style setup that is as cumbersome as much as it sounds, from what I've been told; so a better solution is highly needed and wanted.
    Joshua Donelson
  • Project update: I got Two Raspberry Pi 3B+'s and a Pi Zero W. One Pi 3B+ has a USB Game Controller working in Python to read the Joystick values, this Pi is connected to an official Display with case that will be the controller over Wi-Fi. I still need to send and receive the data between two Pi's.

    The Pi Zero W is connected to the motor controller on the chair and will communicate with the Propeller for reading sensors without getting interrupted by the OS. I saw and bought a Stanley 3-Port Car Charger to give the Pi Zero some power from 24V :)

    I received a bunch more parts and 10 HC-SR04's, A few US1881LUA-AAA-00-BU to make a couple of encoders for the wheels, Some shift registers, Mux/Demuxers, some bus expanders, some servo controllers, heatsinks for some 30V 60A QFET. Wow this is getting pricey but it is worth it. The next month or two I will be putting it all together. I forgot to order some resistors and caps so now I wait for some more components :/

    Not to mention I found out my Fiance is Pregnant :) that means I have 9 months to get all this together and documented, I'm still taking photos and videos but haven't gotten around to updating the first few posts yet.
    Jorge P.
  • JDJD Posts: 481
    Jorge P wrote: »
    Not to mention I found out my Fiance is Pregnant :) that means I have 9 months to get all this together and documented, I'm still taking photos and videos but haven't gotten around to updating the first few posts yet.

    Congratulations Jorge :)

    I feel the pain of waiting on parts in MT, there is no where we can just go out and get parts out here. :cool:
    Joshua Donelson
Sign In or Register to comment.