Research On Phase Coordination Of Multi Points And Normal Modal Test

Modal test and analysis is a very important method to identify the structure dynamic characteristics for the updating of finite element model. It includes vibration measurement, data processing and computer application technology. The modal parameters are the basic data for structure dynamic analysis and vibration control. The methods of modal parameters identification can be cataloged into phase resonance testing (Normal-mode force appropriation) and phase separation approaches. In contrast to phase separation (curve-fitting) approaches which are largely mathematical, phase resonance testing is a physical technique. When a structure is vibrating in a normal mode, the undamped natural frequency and normal-mode shap of the structure are directly measured. In the classic phase resonance testing, the test data processing is simpler and the results are more accuracy. But it takes much time to tune the exciting force, and the testing precision is decided much by the operator's experience.Four aspects of work are done in this thesis based on former work.1. The exciting forces appropriation is realized by the Deck's method automaticly by computer, which overcomes the manual operation influence on the testing precision.2. Based on Effective Independence (EfI) idea, a method is presented to optimize the placement of actuators/sensors in modal test by the successive reduction of them one by one.3. Using the VPP code in LabVIEW and VXI bus, a softwar is programmed for the driving signals generating and the response signals sampling. The software can process the data to appropriate the exciting force, control the whole test and display the response curves.4. A cantilever beam is used as a testing example and the results show that the whole newly developed system is effective.In brief, a complete system has been developed for the normal mode test. To automatically adjust the exciting forces appropriately by a computer is realized in this thesis. The above work is a new contribution to the normal mode test.