A step is applied to a first-order process at t = 0. The output starts at 0 and settles at 20. At t = 3 s it reads 18. Find the time constant τ.
Step response worksheet with answers
An uncharged capacitor C = 1 µF is charged from a 5 V step source through a resistor R = 10 kΩ. How long after closing the switch does the capacitor voltage reach 60 % of its final value? Find t in ms.
A system has the transfer function G(s) = 117/(s² + 9s + 39) and receives a unit step input. The poles are s = σ ± jωd. Find the real part σ.
A system has the transfer function G(s) = 35.5/(s² + 10s + 71) and receives a unit step input. Find the damping ratio ζ.
A unity negative feedback loop has G(s) = 160/(s(s + 4)). Find the 2 % settling time ts of the closed-loop step response, using ts ≈ 4/(ζωₙ).
A unity negative feedback loop has G(s) = K/(s(s + 4)). Find the gain K that gives a step response with 20 % overshoot.
Answer key
- 1. τ = 1.303 s
- 2. t = 9.163 ms
- 3. σ = −4.5
- 4. ζ = 0.5934
- 5. ts = 2 s
- 6. K = 19.24
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