Vision Measurements for Modal Control Data Preparation

Modal control was introduced in the second half of the last century to reduce structure vibrations actively. This concept was forced by the spill-over phenomenon, i.e., the escape of the control signal energy to higher modes of natural vibrations, which resulted in the system’s loss of stability. With the concept of modal control, a modal filter MF was developed, which allowed for removing components related to selected modes from the vibration response of an object. Although it had some drawbacks, the modal filter performed well in preparing data for modal control (better than previously used state observers). One of the problems was filtration’s effectiveness in changing the object’s dynamic parameters (e.g., a change in ambient temperature causing a change in Young’s modulus). The adaptive modal filter AMF was developed in the early 90s of the XX century to extend the modal filter to enable modal control for structures with parameters changing over time. One of the features of the AMF approach is the necessity to operate on a large grid of measuring sensors, which severely limits the method’s applicability at that time. In the current state of technology, high-speed cameras are increasingly used, which allow for the simultaneous measurement of vibrations of many points in a structure. This measuring technique has several advantages: relatively low complexity of the measuring system, simultaneous measurement of many points, and non-contact measurement. In the paper, the authors check the effectiveness of applying vision measurements for AMF synthesis. In the first step, appropriate software was prepared in the MATLAB environment, and its correct functioning was checked using simulation data. Then, a laboratory experiment was carried out with simultaneous vision and accelerometric measurements, and the data obtained were successfully subjected to AMF.