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Convert From One Model Type to Another

This example shows how to convert a numeric LTI model from one type (pid) to another type (tf).

In general, you can convert a model from one type to another type using the model-creation command for the target type. For example, you can use the tf command to convert an ss model to transfer function form, or use the ss command to convert a zpk model to state-space form.

Create a PID controller.

pid_sys = pid(1,1.5,3)
pid_sys =
 
             1          
  Kp + Ki * --- + Kd * s
             s          

  with Kp = 1, Ki = 1.5, Kd = 3
 
Continuous-time PID controller in parallel form.

Convert pid_sys to a transfer function model.

C = tf(pid_sys)
C =
 
  3 s^2 + s + 1.5
  ---------------
         s
 
Continuous-time transfer function.

C is a tf representation of pid_sys. C has the same dynamics as pid_sys, but stores the dynamic parameters as transfer-function numerator and denominator coefficients instead of proportional, integral, and derivative gains.

You can similarly convert transfer function models to pid models, provided the tf model object represents a parallel-form PID controller with Tf0.

In general, you can use the technique of this example to convert any type of model to another type of model. For more specific information about converting to a particular model type, see the reference page for that model type.

See Also

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