[sunmix]

Velocity mode servos have lower performance and are more difficult to tune than torque mode servos. This is because a velocity mode servo has 90 degrees less phase margin than a torque mode servo (velocity is the first integral of acceleration). Torque mode controls acceleration, velocity mode controls speed.

The gas pedal idea simply pictures it into my mind at ease. Thanks Mariss!

But what are these 90 degree less phase margin, and how are they connected in different servo modes?