In the case of rolling installations, in particular cold rolling lines, it is known for undesirable oscillations to occur in certain operating states, for example strip tension, strip tension difference, coefficients of friction, thickness decrease, material strength and strip velocity, and these oscillations can lead to considerable damage to the installation, as well as to defects in the rolled material. 3rd-octave oscillations, also referred to as 3rd-octave chatter, are known by a person skilled in the art from the multiplicity of oscillations which occur in rolling processes. 3rd-octave oscillations typically occur in a frequency range from about 80 to 170 Hz, and are characterized by a high energy content and unstable oscillating states, as a result of which considerable mechanical damage can also occur to the rolling stand of a rolling installation. Since, however, these oscillations also lead to movements of the roller set and therefore to discrepancies from the nominal rolling gap, this leads to defects in the rolled material, which may be in the form of surface defects, geometric defects or else combinations thereof. Typically, when oscillations such as these occur, the personnel operating the rolling installation will immediately reduce the rolling speed, which involves a reduction in throughput (that is to say reduced productivity), and leads to the oscillations decaying. The stated frequency range for 3rd-octave oscillations depends substantially on the respective installation configuration and the rolling parameters, and may therefore also differ therefrom. In a method for suppression of oscillations (so-called “active oscillation compensation”), at least one permanently measured variable of the rolling installation is supplied to a regulator, which calculates a manipulated variable which varies over time. By acting on at least one actuator for roller engagement, it is possible to maintain the controlled variables substantially at defined nominal values, that is to say except, for example, for overshoot processes.
EP 1457274 A2 discloses a method and an apparatus for preventing 3rd and 5th-octave oscillations in a rolling stand. In this case, at least one roller in a roller set is acted on by means of a controller and an actuator, by which means the controlled variables are kept at defined nominal values. Specific embodiments and selection criteria for the actuator cannot, however, be found in the disclosure.
USPTO Backgrounds
USPTO Backgrounds