A step is applied to a first-order process at t = 0. The output starts at 0 and settles at 2. At t = 10 s it reads 0.8. Find the time constant τ.
Step response worksheet with answers
A first-order system G(s) = 8/(s + 4) receives a step input of size 5 at t = 0, starting from rest. How long does the output take to reach 75 % of its final value? Find t.
A system has the transfer function G(s) = 14.5/(s² + 8s + 29) and receives a unit step input. Find the 2 % settling time ts of the step response, using ts ≈ 4/(ζωₙ).
A system has the transfer function G(s) = 27/(s² + 11s + 54) and receives a unit step input. Find the damping ratio ζ.
A mass m = 1 kg hangs on a spring k = 400 N/m with a viscous damper c = 8 N·s/m (m·x″ + c·x′ + k·x = F). At rest in equilibrium, a constant force F = 10 N is suddenly applied. Find the time tp at which the displacement is largest.
A series RLC circuit with R = 190 Ω, L = 100 mH and C = 1 µF is connected to a 24 V step at t = 0. The capacitor is uncharged and no current flows before the step. Find the time tp of the first voltage peak, in ms.
Answer key
- 1. τ = 19.58 s
- 2. t = 0.3466 s
- 3. ts = 1 s
- 4. ζ = 0.7485
- 5. tp = 0.1603 s
- 6. tp = 1.042 ms
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