BLDC max current and e-bike application

[asida]

I have no idea where to start, so I placed my question to general discuss...

I have 2 question:

1. is it possible to make (from available freescale components) custom BLDC controller for higher rates, eg: 36V and 900-1500W ?

2. Would it be possible to measure realtime current with such controller and react on current changes ?

I wish to have elektro-bike controller application where I wish to change engine power based on biker's pedaling power contribution.

desired application description:

if my legs power is aprox 200W, motor runs idle on 10W (with max 900W limit), when I start pedaling, running motor should feel some XX% current decrease repeatelly on 50-70 RPM ( x 2 in fact) pedaling frequency. Bigger decrease = harder pedaling = put more power to motor until maximum.
When stop pedaling (no repeated current decrease) = engine power decrease to some minimal rate again.

is it possible to to make such application  ? If yes, what components should I use ?

thnx

Adam

[TomE]

> If yes, what components should I use ?

I assume you don't want to build the motor controller from scratch, but are looking to control the "throttle" on an existing electric bike.

> running motor should feel some XX% current decrease repeatelly

> on 50-70 RPM ( x 2 in fact) pedaling frequency. Bigger decrease = harder

> pedaling = put more power to motor until maximum.

I don't understand that but I think you want it to work like a "power assist" or "power amplifier". Sort of like a power steering system where it puts in a multiple of what you're supplying. Is that the idea?

The first thing is to measure how much power the human is generating.

You could measure the torque on the pedals with a strain gauge. You might be able to measure the force/deflection on some part of the drive chain to try and separate the motor power from the pedal power. It all depends on the mechanical design as to what you might be able to measure. This would be difficult electromechanical design work though.

You might be able to measure the cycle or motor small speed increase during the pedal downstroke, and from that try to work out how hard you're pushing the pedals, and then control the throttle from that.

If this is to provide exercise, use a heart rate monitor and control the electric bike's power output from that!

Tom