Disability Midwheel Drive Powerchair Conversion Project.

Jorge PJorge P Posts: 341
edited November 8 in Robotics Vote Up0Vote Down
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


  • 3 Comments sorted by Date Added Votes
  • Jorge PJorge P Posts: 341
    edited November 8 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
  • Reserved for project step 2
  • Reserved for project step 3
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