Research of IMC-Fed BLDCM Servo System Based on Fuzzy Control - Intelligent Computing for Sustainable Energy and Environment - page 22

Fig. 2. The division of input voltage sectors
through a position controller. Then the command speed is produced. Secondly,
the actual speed is compared with the command speed and the error between the
two is regulated through a speed controller. Then the need voltage for BLDCM
is produced. In position servo system, an additional controller for position loop
is added. Usually, position overshoot is not allowed in position servo systems. In
order to avoid overshoot phenomenon, a simple P controller is employed instead
of a PI controller in position loop. However, if the P parameter is very large,
overshoot phenomenon also occurs. Therefore, a appropriate P value is chosen to
guarantee servo accuracy and absence of overshoot. In traditional P controller,
the P parameter is fixed and can't be modified. If P is chosen too large, overshoot
phenomenon would appear. Oppositely, if P is chosen too small, the response
speed would be quite slow, though without overshoot phenomenon. Fuzzy P
controller is one that modifies the P parameter according to the error and error-
in-change based on fuzzy theory. In the start time, when the error is large, the
P parameter is large to get rapid response. When the error becomes small, P
parameter value is reduced to avoid overshoot phenomenon. Therefore, fuzzy P
is a flexible controller.The modified P parameter is calculated as
K p = K p 0 + ΔK p ( K p 0 = 200)
4 Simulation Results
The simulation parameters are as follows. 3-phase input: 220V, 50Hz Stator re-
sistance: 4.765 Stator inductances: 0.0085H Flux induced by magnets: 0.1848Wb
Inertia: 0.0001051 Friction: 0.00004047 Pairs of poles: 2 Suppose the command
speed was 2000r/min at 0s and changed to 3000r/min at 0.05s. The load torque
was 1Nm all the time. The simulation results are as follows. From Figure 4(a), it