Root-locus sampled gains calculator

Calculate gain and closed-loop pole coordinates with your own figures.

Your numbers

Use the units shown. Results update as you change valid inputs.

Use gain and closed-loop pole coordinates to compare changes to your inputs. The method and limits below explain the scope.

Examples

Examples

Try the starting example

Plant numerator coefficients
1
Plant denominator coefficients
1,3,2
Negative-feedback gains
0,1,3,5
Gain and closed-loop pole coordinates (JSON)
[[0,[[-2,0],[-1,0]]],[1,[[-1.5,-0.866025403784],[-1.5,0.866025403784]]],[3,[[-1.5,-1.65831239518],[-1.5,1.65831239518]]],[5,[[-1.5,-2.17944947177],[-1.5,2.17944947177]]]]

Try another scenario

Plant numerator coefficients
[2]
Plant denominator coefficients
[1, 3, 2]
Negative-feedback gains
[0, 1, 3, 5]
Gain and closed-loop pole coordinates (JSON)
[[0,[[-2,0],[-1,0]]],[1,[[-1.5,-1.32287565553],[-1.5,1.32287565553]]],[3,[[-1.5,-2.39791576166],[-1.5,2.39791576166]]],[5,[[-1.5,-3.1224989992],[-1.5,3.1224989992]]]]
Calculation method

Calculation method

Gain and closed-loop pole coordinates (JSON)

Negative unity-feedback characteristic polynomial D(s)+K N(s); evaluate numerical roots at supplied gains, not continuous branch tracking.

Symbols and units
a
Plant numerator coefficients
b
Plant denominator coefficients
c
Negative-feedback gains

Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.

Assumptions & limits

Assumptions & limits

  • User-supplied measurements and assumptions; Negative unity-feedback characteristic polynomial D(s)+K N(s); evaluate numerical roots at supplied gains, not continuous branch tracking. Supported limits: Finite numeric values bounded to 1e9 magnitude; lists and tables contain 1–100 records unless a stricter bound is stated. Inputs use the units shown. Lists explicitly paired by a method must have matching lengths; independent polynomial coefficient vectors may differ. Respect stated physical, interpolation, policy and computational domain limits. Polynomial degrees are bounded to 6. Higher-degree near-multiple roots with a small derivative relative to coefficient scale are rejected as ill-conditioned; nonconvergent root solves are rejected rather than presented as accurate.
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Further reading

Method reference ↗

Background reading; this does not imply endorsement or independent review of SumFizz.

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