Abstract: The invention relates to a method of determining a first hydraulic variable (Q) of a pump assembly (1) operated at a predefinable rotation speed (n0) from a mechanical or electrical variable (Mactual, Pel, nactual) by evaluating a correlation between the hydraulic variable (Q) with the mechanical or electrical variable (Mactual, Pel, nactual). A control parameter (Msetpoint, nsetpoint) of the pump assembly (1) is acted on by a periodic excitation signal (fA,n (t), fA,H(t)) having a predetermined frequency (f) such that a second hydraulic variable (H, ?p) is modulated. The instantaneous value of the first hydraulic variable (Q) is determined from the mechanical or electrical variable (Mactual (t), Pel (t), nactual (t)) as a system response (X(t)) to the excitation signal (fA,n (t), fA,H(t)), using the correlation. The invention further relates to a pump control system and a pump assembly that are configured for carrying out the method.

Abstract: The invention relates to a method of determining a first hydraulic variable (Q) of a pump assembly (1) operated at a predefinable rotation speed (n0) from a mechanical or electrical variable (Mactual, Pel, nactual) by evaluating a correlation between the hydraulic variable (Q) with the mechanical or electrical variable (Mactual, Pel, nactual). A control parameter (Msetpoint, nsetpoint) of the pump assembly (1) is acted on by a periodic excitation signal (fA,n (t), fA,H(t)) having a predetermined frequency (f) such that a second hydraulic variable (H, ?p) is modulated. The instantaneous value of the first hydraulic variable (Q) is determined from the mechanical or electrical variable (Mactual (t), Pel (t), nactual (t)) as a system response (X(t)) to the excitation signal (fA,n (t), fA,H(t)), using the correlation. The invention further relates to a pump control system and a pump assembly that are configured for carrying out the method.