 #1
JasonLi
 119
 14
 Homework Statement:

The proportional control system of FIGURE 3(a) has an input, Q1, of 10 units. The uncontrolled input, Q2, has a value of 50 units, prior to a step change down to 40 units. The result of this disturbance upon the output, Qo, is shown in FIGURE 3(b).
Calculate the change in offset in the output produced by the step change.
 Relevant Equations:
 Control Systems Equations
Hello, I found an old thread related to this question but it doesn't look correct to me so was looking for some guidance.
I have equated Qo = (Q2+Q1*G) / (1+H*G)
I did this by rearranging Qo=Q2+G(Q1Q0*H)
I then went on to the calculations and found before step disturbance:
Qo= (50+10*9)/(1+0.1*9) = 73.68
And After:
Qo=(40+10*9)/(1+0.1*9) = 68.42
Giving an offset of 5.26
My issue is that if you look at figure 3b the Qo  time graph 73.68 and 68.42 don't seem to line up to where the disturbance starts and where it resettles at?