OpenChair is a project developed with Irene Sanz aiming to create the first electric wheelchair development platform, that is a wheelchair that anyone can modify in hardware or software to adapt to their needs or create new control methods.
The first step was to get the electric part working. After searching for a combination of motors, drivers and battery+charger powerful enough to transport an adult for more than ten minutes, we came to the conclusion that taking advantage of mass production was the way to go and got a hoverboard.
For about 270€ new (and with the huge number of sales, probably a lot less in a second-hand store) we got 2x350W brushless motors and a 36V 4400mAh LiPo battery with an autonomy of up to 20km per charge.
Once the motion was taken care of, we wanted everyone to be able to customize their chair easily, so apart from uploading all the source files we incorporated a set of slots into which a number of accessories could be slid.
These could be anything from hooks to carry bags, drink holders, phone/tablet stands... or even active ones, such as a torch or horn. To this end, all the grooves have a hole through which the cables can pass and go to the controller board, effectively hiding them from view and keeping a clean look.
The control board used initially in the chair was a Nucleo F446RE, an STM32 board with an ARM Cortex-M4 processor but we then developed our own board based on the NXP LPC1768 processor and the nRF8001 Bluetooth Low Energy radio.
This, in addition to the broken-out GPIOs and I2C, SPI and UART buses should give the user the ability to add any type of sensor or actuator to interact with the chair in the way that suits them best.
Additionally, we designed an extra board based on the nRF51822 Cortex-M0+BLE SoC and the BNO055 9DOF IMU with on-board sensor fusion intended to control the chair through gestures, so people unable to use the joystick can strap the board to their head (or wherever they're able of moving) can still use the chair autonomously.