Vibration is a phenomenon related to every physical system that has the potential to cause severe problems that range from increased structural fatigue to potential operator health hazards. The traditional approach to solve the vibration related problems is to dissipate the vibration energy through the addition of passive damping elements consisting of springs, masses and dampers. Even though these methods have been widely applied in all branches of industry, they are becoming increasingly inadequate in meeting the industrial standards of today. In the past decade the significant increase in the available computational power has given a rise to another approach to tackle the vibration related problems; namely the active control of vibrations, which is capable of meeting the tightened standards. In this approach, the vibrations are suppressed through the excitation of external energy in a suitable form into the system, resulting in the compensation of the vibrations. The use of this approach has enabled the mitigation of vibrations in very complex structures in a deterministic manner. The major benefit of the method is the change of the underlying design problem. Namely, the original structural design problem is converted into a standard control design problem, enabling the designer to use the very powerful tools of control theory. In this thesis, a novel method for active vibration mitigation is presented. The proposed approach shares many similarities with the existing model-based methods while addressing many of the drawbacks and problems encountered with the current approaches. The proposed method is a generic nonlinear control law capable in the simultaneous suppression of multiple tonal disturbances in multiple dimensions. The control design procedure is simplified such that the number of free parameters is minimal and the impact of these parameters on the process performance is transparent. Such an approach enables the method to be applied by an industrial system specialist with possibly very little experience in control theory, unlike what is the case with the most of the existing methods. In addition, the essential tools for the performance and stability evaluation of the obtained control law are presented in detail with the focus being in the problems commonly encountered in the practical implementation. This thesis consists of a summary and five publications with the focus being on the control design, performance analysis and test-bed implementation in several industrial processes. An extensive comparison of the proposed method against the existing linear control approaches is also included in this work.
In this paper a method of suppressing vibrations in an industrial rolling process with varying rotational frequency is presented. The vibrations in a rolling process are problematic as they do not only cause structural fatigue on the machinery, but also deteriorate the quality of the end product. The traditional approach for this type of a problem would be to avoid the critical frequencies of the process by changing the rotation speed of the reel, thus decreasing the vibrations. However, in practice this is hard to achieve as the radial velocity of the reel should be constant, while rotation speed of the reel varies depending on the diameter of the reel. The changes in radial velocity are typically not allowed as the rolling process is usually part of a larger process, where change in rotation speed affects the whole process. This paper introduces a generic modified LQ-control law to tackle the problem. This control design was designed in a previous ACRVEM-project (Active Control of Radial Rotor Vibrations in Electric Machines) and has been successfully used in suppression of radial rotor vibrations in electric drives, resulting in 90% damping of the vibrations. The major drawback of the controller has been the limitations due to its linear nature; the control is applicable only at a certain predefined rotational frequency, and outside this frequency the controller becomes unstable. In order to resolve this problem, a nonlinear optimal state-feedback controller based on continuous gain scheduling is introduced. This modification of the original controller is capable of suppressing the vibrations over the whole operational frequency range. In this paper the modelling and identification of the rolling process is first discussed. After the model has been obtained the control design procedures for both linear and nonlinear controllers are presented in detail. The performances of both controllers are analyzed in extensive simulations. Finally the simulation results are validated by implementing the designed controllers in the actual rolling process. It will be shown that this control methodology is highly effective for this type of vibration damping problems resulting in over 90% decrease in the vibrations over the whole frequency range of rotation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.