A step is applied to a first-order process at t = 0. The output starts at 0 and settles at 4. At t = 0.5 s it reads 1.2. Find the time constant τ.
Step response worksheet with answers
1.Easy
y(∞) = 4y(0.5) = 1.2
τ = s
2.Easy
A first-order system G(s) = 2.5/(s + 5) receives a step input of size 10 at t = 0, starting from rest. Find the final value y(∞) of the output.
G(s) = 2.5/(s + 5)U = 10
y(∞) =
3.Medium
A system has the transfer function G(s) = 188/(s² + 4s + 94) and receives a unit step input. Find the damping ratio ζ.
G(s) = 188/(s² + 4s + 94)
ζ =
4.Medium
A system has the transfer function G(s) = 5/(s² + 3s + 5) and receives a unit step input. Find the percent overshoot %OS of the step response.
G(s) = 5/(s² + 3s + 5)
%OS = %
5.Hard
A unity negative feedback loop has G(s) = 260/(s(s + 16)). Find the 2 % settling time ts of the closed-loop step response, using ts ≈ 4/(ζωₙ).
G(s) = 260/(s(s + 16))
ts = s
6.Hard
A unity negative feedback loop has G(s) = K/(s(s + 8)). Find the gain K that gives a step response with 2 % overshoot.
G(s) = K/(s(s + 8))%OS = 2 %
K =
Answer key
- 1. τ = 1.402 s
- 2. y(∞) = 5
- 3. ζ = 0.2063
- 4. %OS = 5.833 %
- 5. ts = 0.5 s
- 6. K = 26.32
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