METHOD FOR CONTROLLING MOLTEN METAL SURFACE LEVEL IN CONTINUOUS CASTER AND CONTROLLING UNIT

PROBLEM TO BE SOLVED: To provide a control method, in which the variation of molten metal surface level due to the non-stationary bulginess or the periodic disturbance caused by the eccentricity of pinch rolls is suppressed in a continuous caster. SOLUTION: A notch filter 21 is interposed in a molten metal surface level control system control loop and also, the control system for adding the molten metal surface level deviation into a computing output in a molten metal surface level control law 16 is constituted through a band pass-filter 22, a phase compensator 23 and a phase compensating gain 24. Frequency of the notch filter and the band pass-filter is adjusted to the pre-obtained periodic disturbance frequency. The periodical disturbance frequency is obtained from a peak component obtained by executing the frequency analysis to the variation of the molten metal surface level and may be automatically set to the notch filter and the band pass-filter. Control parameters of the notch filter, the molten metal surface level controller and the phase compensating gain may be better to be automatically set. When the frequency analisis is executed, the periodical disturbance frequency can be obtained at high speed by using a turning type frequency analyzing method having a variable frequency generator.