INVESTIGATION OF RESONANT FREQUENCIES AND OWN FORMS OF VIBRATIONS OF SENSITIVE ELEMENTS OF ACCELEROMETERS

Abstract

The article presents the results of the simulation of sensitive elements of pendulum micromechanical accelerometers (MMA). MMA basically have a cantilever suspension scheme, where elastic elements are similar to beams working on bending or torsion (torsions). For the manufacture of sensitive elements MMA used mainly monocrystalline silicon KEF-4,5 (100), which has high elastic characteristics. The analysis of real products for resonance and the ability to modify them in order to remove from the range of forbidden eigenfrequencies remain an actual problem in the design of sensitive elements of the pendulum micromechanical accelerometers.The main constructive node of the micromechanical accelerometer is a sensitive element which includes mass and elastic elements of the suspension, is attached to the support frame (base). Elastic elements of the suspension are located on the console or bridge scheme. Under the bridge scheme, the suspension M moves strictly along the measuring axis. Multilayer bridge suspension M is characterized by low sensitivity to transverse actions, high rigidity and basic self-frequency. The dynamic analysis seeks to calculate of the resonant (own) frequencies and their corresponding forms of oscillation.The module COSMOSWorks implements the classical finite elemental method, which has the following limitations: damping is not taken into account; the presence of friction is ignored; the external load which changeable is absent.The consequence of the first limitation is the inability to obtain information on the state of the design at the moment of resonance. None of the parameters (displacement, deformation, stress) is not calculated. Also, the analysis of behavior during loading of loads is not available.However, even with these restrictions, the program allows you to solve the most urgent task - to perform the analysis of real products on the resonance and to modify them in order to remove from the range of forbidden eigenfrequencies.The finite element method was used to study influence of the geometric parameters of the elastic suspension and the mass of the sensitive element on the frequency of natural oscillations with correction for damping. In the modeling of suspensions of different shapes, a stress-strain state of the sensitive element was determined and an analysis of the elastic characteristics was conducted to select the optimal design