I am referring to mild hybrid vehicles. How long does the regenerative braking work? Whether it is for few seconds, minutes? It does this by negative torque. Can i produce the negative torque and positive torque but still rotate in the same direction as engine? Please advise.

 

The braking is performed by turning the electric motor temporarily into an electric generator.
This lasts until the vehicle ceases to slow down or until it stops.

 

But is it possible to control the amount of braking like sometimes i may want more braking etc ?

 

The torque can be applied both positive, (driving) or negative, (braking) while the shaft revolves in the same direction.

It depends on the direction of energy flow, either from, or to the motor.
You can proportion either energy flow either way, to control the amount of drive or braking effect.

On a long downhill run, the energy flow could be regenerated for minutes at a time.

 

An electric motor can both source and sink torque.

It's an electric current to torque transducer(usually called a motor).....and a torque to electric current transducer(usually called a generator).

It's like a intercom speaker(a regenerative speaker sorta speak)..........it works both ways.

Everything is adjustable and controllable.