Comparison of experimental and operational modal analysis on a back to back planetary gear

Abstract

Several modal analysis techniques are widely used to study the dynamic characteristics of a structure byidentifying the modal parameters. This paper presented a comparison between anExperimental Modal Analysis (EMA) test and an Operational Modal Analysis (OMA) test and an Order Based Modal Analysis (OBMA) applied on a recirculating energy planetary gear. TheOMA and OBMA offer a test of the planetary gear under its realboundary conditions, whereas the EMA is based on the frequency response function estimation. Using the different techniques, the back to back planetary gearmodal parameterswereidentified. In afirst step, the experimental results determined by EMA and OMA were correlated to the numerical results model obtained by athreedimensional lumped parameter model. In asecond step,the OBMA estimated modal parameters were compared to those of the EMA. According to the obtained results, OMA cannot excite all the modes. However,it was noticed that there is no significant differencebetween the modal parameters obtained by the EMA and theOBMA.The natural frequencies and damping ratios were deviating by 11% and 2.43%, respectively. Highlights Planetary gear natural frequencies and damping ratios wereidentified with three different modal analysis techniques.  FRF, Cross Power Spectral Density, Order Function, Mode shapes,modal assurance criterion and stability diagram were presented.  Modal analysis under rotating excitation is different from the conventional modal analysis.  Validation by three-dimensional lumped parameter model.

Experimental Characterization of the Coupling Stage of a Two-Stage Planetary Gearbox in Variable Operational Conditions

“…Each planetary train comprises one carrier C (n) , two planet gears P (n) , one sun gear S (n) and one internal ring gear R (n) ; the superscript n indicates the corresponding planetary train, n = 1 for the input train and n = 2 for the output train. Note that since the sun gears are fixed on the same shaft and the ring gears are on the same frame, each couple of gears actuates as a rigid body, S (1,2) and R (1,2) . The input torque is applied to the sun gear S (1) and ring gears R (1) from the input carrier C (1) by means of the planet gears P (1) .…”

“…Note that since the sun gears are fixed on the same shaft and the ring gears are on the same frame, each couple of gears actuates as a rigid body, S (1,2) and R (1,2) . The input torque is applied to the sun gear S (1) and ring gears R (1) from the input carrier C (1) by means of the planet gears P (1) . Since sun gears and ring gears act like a rigid body, the torque is transmitted to the planet gears P (2) to the output carrier C (2) .…”

“…P = 0. Consequently, the closed gear chain P (1) -R (1) -R (2) -P (2) -S (2) -S (1) behaves as a unique rigid body which rotates about the axis of the two sun gears. Thus, the movement of the input carrier is directly transmitted to the output carrier, giving ω…”

“…Experimentally, it is based on impact test and an excited mechanical structure by means of a hammer and a shaker, respectively. Nevertheless, it has been proved that experimental modal analysis suffers from missing modes because some modes cannot be excited [1]. Numerous research works on condition monitoring and fault diagnosis have been accomplished with the aim of preserve planetary gearboxes in healthy operating conditions.…”

Dynamic behaviour of three-dimensional planetary geared rotor systems

“…To validate the modal behaviour of the dynamic models, some experimental studies were performed for spur planetary gear sets. Computed rotational, translational and planet modes in the torsional -transverse model were correlated with these experimental studies [34,[37][38][39].…”