- Brief system overview
The motor/power module will be capable of some serious power, the aim is >1KW. it will take a max 52V battery input (13cell lithium) and incorporates regenerative braking to recharge the battery when slowing down. The motor control is sensorless (only connection to the motor will be via the 3 power phase connections) and the drive waveform is sinusoidal, as opposed to trapazoid waveform drives which dominate the market currently, this provides much smoother power delivery by reducing torque ripple, efficiency is also increased by removing unnecessary current ripple through the motor. This is achieved using TI's InstaSpin solution running on a Piccolo microcontroller.
The control/monitoring module will act as a bridge between the power module and android phone software for on-the-fly analysis and control. Aside from this core function it will contain circuitry to allow charging of the phone, control of expansion modules - for example to drive bike lights so you can make it look like tron - and any other function you can get on a shield - because this expansion interface will be Arduino compatible. The module and phone will be housed in a sturdy yet slick 3d-printed handlebar mount which functions as a vehicle head-unit.
Vital control signals will be double checked by both modules to make the system more failsafe. Including the throttle, regenerative brake lever and emergency cutoff
- Where are we now?
Design of the motor control hardware is now up to it's 4th PCB revision, with the last two revisions dealing with power layout and protection circuitry. We want the motor control with TI's chip to be proven and stable before trying to do the advanced integration we plan.
Motor control software has been developed enough to get a working test-bed with basic data reporting via the UART.
We have developed a mechanical test bench for load testing at up to 1 horsepower in the lab, and a rough but functional hardware implementation on a mountain bike.
- What do we still need to achieve?
Motor control software needs to be hardened with extensive failsafes and a sturdy communication protocol needs to be implemented
The control unit and Android app development is still in a block-level design stage, We still have a lot of hardware, mechanical and software design work for these parts.
Thanks go to Clayton and James for technical inspiration and help.