The servo motor starts with the mode of the light load and
the given speed value is 200rad/s. The blue curve is the actual
speed / position, and the red curve is the estimated speed /
position. As shown in Fig. 4(a), when the time is one fifth of a
second (0.2s), we change the given speed to 250rad/s.
Compared with the actual speed, it is clearly seen from the
motor speed curve that when the servo motor is at start-up
stage or the given speed have a sudden jump, the estimated
speed exists certain error. Nevertheless, the estimated speed
will quickly converge to the actual speed, which means that the
error between the actual speed and the estimated speed will
tend to 0 from the time about two fifths of a second (0.4s). As
shown in Fig. 4(a) and (b), the estimated rotor position is
obviously in accordance with the actual rotor position.