A step is applied to a first-order process at t = 0. The output starts at 0 and settles at 100. At t = 3 s it reads 80. Find the time constant τ.
Step response worksheet with answers
A first-order system G(s) = 1/(2s + 1) receives a step input of size 2 at t = 0, starting from rest. How long does the output take to reach 98 % of its final value? Find t.
A system has the transfer function G(s) = 40.5/(s² + 11s + 81) and receives a unit step input. Find the damping ratio ζ.
A system has the transfer function G(s) = 18/(s² + 2s + 6) and receives a unit step input. Find the 2 % settling time ts of the step response, using ts ≈ 4/(ζωₙ).
A second-order system without zeros must have a step response with 25 % overshoot. Find the damping ratio ζ.
A mass m = 20 kg hangs on a spring k = 800 N/m with a viscous damper c = 152 N·s/m (m·x″ + c·x′ + k·x = F). At rest in equilibrium, a constant force F = 50 N is suddenly applied. Find the damping ratio ζ.
Answer key
- 1. τ = 1.864 s
- 2. t = 7.824 s
- 3. ζ = 0.6111
- 4. ts = 4 s
- 5. ζ = 0.4037
- 6. ζ = 0.6008
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