"feedback" amd "append" comands

In this Matlab tutorial, DC motor control example, about 60% of the way down you see this Feedback command:

cl_rloc = feedback(dcm * append(C,1),1,1,1);

What is the purpose of "append"-ing the compensator 'C' in this closed-loop feedback design?

Before this "feedback" command, "dcm" was the 2-input / 2-state State Space equation of the DC Motor: back EMF voltage, and angular velocity. After appending, the SS equation "cl_rloc" has three states, but I don't see why it requires three, nor is the example clear what the third state would be.

Answer 1

[Arkadiy Turevskiy]

Read the section of the example preceding this code immediately. You will see that what the example does is apply feedback control in the form of K/s (integral compensation). The feedback is applied through the first input of dcm, which as you noticed is a 2 input 1 output system.

append is needed to compute closed loop transfer function that you get when you apply feedback k/s to the first input channel of 2x1 system dcm. The resulting closed loop system has 3 states because the third state comes from the integral gain k/s.

hope my explanation helps.