Simulink Control Design™ - MathWorks

Linearize the model.

io(1) = linio('scdpwmharddrive/Duty cycle',1,'input');

io(2) = linio('scdpwmharddrive/Hard Disk Model',1,'output');

sys = linearize(model,io)

sys =

D =

Duty cycle

position err 0

Static gain.

As expected, the PWM components cause the system to linearize to zero.

Turn the local solver back on for simulation.

set_param(SimscapeSolver,'UseLocalSolver','on')

Find Linear Model for PWM Component

You can estimate the frequency response of the PWM-driven current source and use the

result to identify a linear model for it. The current signal has a discrete sample time of

1e-7. Therefore, you need to use a sinestream signal with a fixed sample time as your

estimation input signal. Create a signal that has frequencies between 2,000 and 200,000

rad/s.

idinput = frest.createFixedTsSinestream(Ts,{2000,200000});

idinput.Amplitude = 0.1;

Define the input and output points for the PWM-driven circuit, and run the frequency

response estimation using the sinestream input signal.

pwm_io(1) = linio('scdpwmharddrive/Duty cycle',1,'input');

pwm_io(2) = linio('scdpwmharddrive/PWM driven converter',1,'openoutput');

sysfrd = frestimate(model,pwm_io,idinput);

To identify a second-order model using the frequency response data, use tfest from the

System Identification Toolbox. Then, compare the identified model to the original

frequency response data.

2 Linearization