AJC5001 wrote:AF62 wrote:As for 3 pedals - then I take it that a BEV with 'one pedal driving' making the brake pedal redundant as the car goes into regenerative braking when you stop accelerating, would be utterly unacceptable
Silly question (I hope ) - How do you do an emergency stop using regenerative braking?
Adrian
There are various levels of answers.
There's no real difference between a stop and an emergency stop.
As a driver you press the brake hard (or release the only pedal) and let the motor controller do it's thing.
As a hardware engineer you note that with proper motor control any motor can generate more torque against the direction of rotation than in the direction of rotation. The reason for this is that when braking resistive losses help rather than hurt.
This satisfies the criteria that you can stop faster than you can accelerate. If you have a spec for how rapidly you need to do an E-stop that would affect the sizing of the motor and motor controller (just as it would affect the sizing of brake pads).
As a software engineer you have the motor controller control the applied voltage so the AC current is a few Hz slower (for an induction motor) or a few degrees retarded (for a permanent magnet motor) than the rotor. The rotor is dragged towards the AC current which slows the rotor, and also increases the current, which means the motor controller needs to apply voltage opposing the current which is to say it operates as a generator.
As a mathematical physicist there is nothing different between acceleration and braking. There is no discontinuity, it's just that some of the variables smoothly change sign as you go from positive torque (motor) to negative torque (generator).