[logfromblammo]

The hinge that connects each blade to the rotor is angled with the same pitch, but on opposite sides of the rotor, like this:

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When the rotor applies more torque than the current angular momentum of the blades, the blades lag behind the central hub, pushing them the same direction against their hinges. On one side, that increases the blade pitch. On the opposite side, it decreases the blade pitch. The motor could also apply a slight braking force, to pitch the blades in the opposite direction.

The flight computer determines the correct timing at which to apply more oomph to the drive motor, which translates to the same effect as a mechanical swashplate due to the angled pins. The total energy imparted to the blades over a single rotation remains the same as with a motor operating at constant torque.

One disadvantage is that you will need a motor that is capable of applying more maximum torque, because you won't be running it at 100% all the time, but with a sinusoidal power level that will go both above and below that steady level. The other disadvantage is complexity in the computer controlling the motor. The advantage is mechanical simplicity.