Abstract: Parallel-working controllers are provided to control processes whose performance is dependent upon working points. These controllers are allocated to selected working points, and their output signals are put into effect, after being weighted, in dependence upon the working-point parameters that have a dominant influence on the process performance. The method is preferably implemented using fuzzy logic. A transition which is smooth in terms of interpolation is possible among the controllers.

Abstract: A signal which is dependent solely on the disturbance variable is selected by means of a filter and fed to a disturbance detector. This disturbance detector simulates the steady and alternating component (sine component) of the selected signal, as well as a signal (cosine component) phase-leading by 90.degree. with the latter signal. The correction signal required to exactly compensate for the disturbance variable is determined from the sine and cosine component of the periodic disturbance signal component by means of frequency-controlled function generators and a complex phasor calculation.

Abstract: A process and device for compensation of the effect of roll eccentricities upon thickness regulation of material being rolled in a roll stand (1), wherein eccentricity oscillations are simulated by a model (6) based on measured values of roll adjustment position (s), roll force (F.sub.W) and mean support roll speed (n), together with spring constants (C.sub.G, C.sub.M) for the roll stand and the material. An output signal (.DELTA..sub.R) of the model (6) is used to modify the thickness value (h.sub.a +.DELTA.R) used for regulation, so as to compensate for the effect of roll eccentricity. The model may be implemented by a device (RECO) comprising pairs of oscillators (7), the phase and amplitude relationships of which are adjusted according to the observer principle.

Abstract: An impedance controller is used for controlling electrode-to-bath spacing in an arc furnace. Measured quantities proportional to the electrode voltage and the electrode current are determined and an actual impedance value is formed from the measured values by means of a divider. The actual impedance value is compared with a predeterminable desired impedance value to derive a control signal. If in the event of a short circuit, the actual impedance value reaches a predetermined lower limit, a switching element sets into the controller a signal causing full drive, so that the electrodes are raised at maximum velocity. If the sum of the two measurement quantities becomes zero, the output of the controller is cut off.