I have just made a repository for this projet on github: CANbus Wheelchair Controller It includes a builder's and user's manual as well as the hardware and software designs. It is licensed as GPL-3.0.
Here's a copy of the github readme:
An Open Source, Open Hardware multi-node CANbus Wheelchair control system
WHY BUILD YOUR OWN CONTROL SYSTEM?
It's not because this system does things that (upper-end) commercial systems don't do. It is because it let's YOU do things that you can't do easily, or can't do at all, with current controllers. Do you want to run a chair at 36V or 48V? Do you want to have user inputs different from what commercial systems provide? Do you want to try to solve the problems of using brushless motors? Do you want to have 150 Amps per channel either for speed or for grunt on difficult terrain? WHY BUILD YOUR OWN CONTROL SYSTEM?
In other words, this is not an attempt to improve on commercial systems, but an attempt to allow experimentation that can't be done (except by the manufacturer) with commercial systems. Some of this doesn't actually require a CANbus setup - there's a version of the Roboteq script component that can be used without a CAN bus. But if you need something other than a joystick or you want to avoid a complex wiring harness or you appreciate the interference-resistance of CAN, then there's reason to use CANbus.
The system has several CANbus modules: a Master module that interprets user input, a Power Distribution module to handle high-current tasks, a Display module to provide information and a Programmer module to change various user settings. Hardware designs and code for these are included. These interact with one or another RoboteqTM motor controller, and a script for the controller is included. Contributors should feel free to modify this system to work with other controllers. Although designed for wheelchair control, the system is readily adaptable to any differentially-steered mobile device.
Before jumping into the individual folders, each of which has its own ReadMe file, I strongly recommend that you read, or at lest skim, the Manual (a.k.a. User and Builder's Guide).