Design and Production of a Pneumatic Moving Exciter for Determination of Vibration Behavior of Structures in Variable Frequencies

Abstract

Determination and analysis of vibration behavior of structures for at least first few natural frequencies and mode shapes needs several sensors to be connected at different non node points and exciting the structure at one point. Other method for determination of first few mode shapes is to excite several points of the structure at once and sensing the response from one point. Both methods need several force or accelerometer sensors. Excitation of the structure can be done by impulse from a hammer, electromagnetic, pneumatic, and acoustic or laser exciters. Other method for determination of mode shapes with only one accelerometer sensor and one force transducer is possible by a moving exciter with predetermined velocity. Force excitation can be from electromagnetic, hydraulic or pneumatic system. Pneumatic type of excitation which is clean and is sensitive to small changes is used to design a moving non touching exciter for structures. This type of exciter is useful for determination of vibration behavior of sensitive and fragile structures which hammer or touching electromagnetic system cannot be used. This paper presents a design and production of a pneumatic moving exciter of a structure. Excitation force can be impulse, step, ramp or harmonic with different speeds of moving excitation point. The system was used to excite a beam and results are verified with theoretical results.