Power braking control law

[gp]

To make it a bit more confusing (and definetely I could miss something here), but let's think about all this from the standpoint of law of conservation of energy. Which states, that energy just cannot vanish into or come from thin air. So, if the wheel is moving, it has some considerable amount of kinetic energy. When braking, there are only two options – to convert that energy to heat or if possible, store into the battery. There's no difference, how hard we will brake, the amount of the kinetic energy of the moving wheel – with which we have to deal –  doesen't change upon that. The only thing that does change, is the time availvable we have, to convert that energy to some other form. The shorter the time, the more heat or current (to the battery) we'll get in that timeframe. So, if so called power braking would also need to use energy from battery, then there should be a lot more heat to be dissipated somewhere, as the kinetic energy from the wheel doesen't just fade away.  Which, to be honest, doesen't make sense... or? You can't fight energy with energy, and they somehow cancel each other out peacefully, if you'll get my point...  

[Jurgen]

 

E_k = ½mv²

I my quick calc are correct: a 70kg adult+10kg wheel at 20KmH that's 1200J energy, putting this to a stop in 1,2sec means you'll need a 1000W peak power to do so.

Apart from peak current, the total energy that has to be absorbed should be less of a problem as a lot of it will go to the postal stamp size burning rubber when the weel blocks.

Between the forward and backward rotation (if any) there should be a point where the motor doesn't rotate  (if all goes well ), all this in 1,2sec, let's say: 0.5 slow down +0.2 stop + 0.5sec to full reverse. Is an EUC motor capable of delivering max power in 0,5sec?

[gp]

Well, this 1000W is exactly the power that wheel / motor is able to generate in this timeframe and the problem is, where to put it.  As to consulting w experts – there are exactly two ways to deal w this energy peak (power) – either to store it to battery, as much as the controller / inverter / battery is capable of, or to start shorting engine coils (may be insert some resistor etc) in which case the heat will be generated accordingly in the coils / resistor. Also, the wheels ability to brake (act as generator) is exponentially tied to its rolling speed. Which indeed means, that at some point, when the speed of the wheel is already too low to generate enough voltage to charge the battery, controller can make some "tricks", which use power from the battery to slow the wheel down more quickly. Hence generating a bit more heat. Because in the teorethical frictionless world the wheel would keep rolling indefinetely, as the braking strength would keep to fade as the wheel slows,  the slower it turns, the less it brakes, but never stops... Or smthng like this. But it is not the point in this discussion anyway. 

But at high speed, the problem is, where to put the energy from the spinning wheel as quickly as possible, not from the battery. If, hypothetically spekaing, the wheel is mechanically jammed at high speed, then all the energy would have to go to burning rubber. Which is not very effective braking method, as we know from other wheeled stuff like cars for instance.