import type { PidInput, PidResult } from './types.js';
/**
 * PID Tuning Calculator — Ziegler-Nichols / Cohen-Coon
 *
 * @formula
 *   Z-N Step Response: Kp = T/(K×L), Ti = 2L, Td = 0.5L (for PID)
 *   Z-N Ultimate:      Kp = 0.6×Ku, Ti = 0.5×Pu, Td = 0.125×Pu (for PID)
 *   Cohen-Coon:        Kp/K × (T/L) × f(L/T) with dead-time ratio corrections
 *
 * @reference Ziegler, J.G. & Nichols, N.B. (1942). Optimum Settings for Automatic Controllers.
 * @reference Cohen, G.H. & Coon, G.A. (1953). Theoretical Consideration of Retarded Control.
 *
 * Every coefficient below (0.6/0.5/0.125 for Z-N ultimate PID, 1+r/3 through 4L/(11+2r) for
 * Cohen-Coon, where r = L/T is the dead-time ratio) is the published table value for the cited
 * method, not a derived or approximated figure — see the golden tests in pid.test.ts for a
 * worked numeric case per method and controller type.
 */
export declare function pid(input: PidInput): PidResult;
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