Block diagrams worksheet with answers

Free printable Block diagrams worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

For teachers: free to print, copy and use in class. Every new worksheet has new values and its own answer key. A link to ExamProblems on your course page is appreciated.

Name: ____________________   Date: ____________

1.Easy
R(s)15G₂9G₃+−6G₁C(s)

The signal R splits into two parallel blocks G₂ = 15 and G₃ = 9. Their outputs meet at a summing junction with the signs shown (+ and −), and the sum passes through G₁ = 6. Find the overall gain T = C/R.

G₁ = 6G₂ = 15G₃ = 9signs: + G₂, − G₃
T =
2.Easy
R(s)+4G₁9G₂C(s)1H−

In the block diagram the forward path has the gains G₁ = 4 and G₂ = 9 in series, and the negative feedback path has the gain H = 1. Find the overall gain T = C/R.

G₁ = 4G₂ = 9H = 1
T =
3.Medium
R(s)+32s + 4G(s)C(s)0.5H−

A plant G(s) = 32/(s + 4) is controlled in a negative feedback loop whose sensor has the gain H = 0.5. A step of size 1 is applied at R. Find the steady-state output css.

G(s) = 32/(s + 4)H = 0.5R = 1
css =
4.Medium
R(s)+13s + 5G(s)C(s)0.2H−

A plant G(s) = 13/(s + 5) is controlled in a negative feedback loop whose sensor has the gain H = 0.2. Find the time constant τ of the closed loop.

G(s) = 13/(s + 5)H = 0.2
τ = s
5.Hard
R(s)+14controller+D(s)+6s + 4plantC(s)−

A proportional controller K = 14 drives the plant G(s) = 6/(s + 4) in a unity negative feedback loop. A disturbance D enters at the plant input (it is added to the controller output). A reference step of size 2 and a disturbance step of size 0.5 are applied together. Find the steady-state output css.

K = 14G(s) = 6/(s + 4)D = 0.5R = 2
css =
6.Hard
R(s)+Ks(s + 7)(s + 9)G(s)C(s)−

The plant G(s) = K/(s(s + 7)(s + 9)) is in a unity negative feedback loop. Use the Routh–Hurwitz criterion to find the largest gain Kmax for which the closed loop is stable.

G(s) = K/(s(s + 7)(s + 9))unity negative feedback
Kmax =

Answer key

  1. 1. T = 36
  2. 2. T = 0.973
  3. 3. css = 1.6
  4. 4. τ = 0.1316 s
  5. 5. css = 1.943
  6. 6. Kmax = 1008

Full step-by-step solutions: practise this topic on examproblems.com.