A step is applied to a first-order process at t = 0. The output starts at 0 and settles at 5. At t = 0.5 s it reads 2. Find the time constant τ.
Step response worksheet with answers
An uncharged capacitor C = 1 µF is charged from a 24 V step source through a resistor R = 22 kΩ. How long after closing the switch does the capacitor voltage reach 90 % of its final value? Find t in ms.
A system has the transfer function G(s) = 24/(s² + s + 8) 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) = 42/(s² + 4s + 42) and receives a unit step input. Find the natural frequency ωn in rad/s.
A mass m = 20 kg hangs on a spring k = 200 N/m with a viscous damper c = 38 N·s/m (m·x″ + c·x′ + k·x = F). At rest in equilibrium, a constant force F = 100 N is suddenly applied. Find the damping ratio ζ.
A unity negative feedback loop has G(s) = K/(s(s + 5)). Find the gain K that gives a step response with 10 % overshoot.
Answer key
- 1. τ = 0.9788 s
- 2. t = 50.66 ms
- 3. ts = 8 s
- 4. ωn = 6.481 rad/s
- 5. ζ = 0.3004
- 6. K = 17.88
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