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Identification of elastomeric isolator parameters on air-borne EO/IR camera with multi-axis gimbal

Abstract

Stabilization performance of an air-borne EO/IR camera is severely affected mainly by two factors: One is the vibration transmitted from the platform, and the other is the torque disturbance due to mass imbalance of the inner gimbal installed on the camera. Elastomeric isolators are commonly employed in aeronautical equipment due to their ease of installation, light-weight, and excellent dissipation characteristics. The dynamic characteristics of an elastomeric isolator are a function of frequency and also of temperature. Therefore, it is very important to obtain accurate parameters for its dynamic characteristics for the control of an EO/IR camera system. The parameters are identified inversely by testing and by using finite element calculation with proper modeling of the isolators. In this paper, the process of identifying the dynamic parameters of the isolators using a simple pilot test and a finite element model of the camera system is presented. A pilot test equipment is built to put real environmental condition (e.g., temperature condition, heat flow condition, etc.) on the elastomeric isolator. Therefore, the characteristics of an elastomer identified on tests are the dynamic values reflecting the temperature environment characteristic. In the process, 3 dB method is introduced for fast and effective parameter identification. On matching the isolator model on FEA to the disturbance transfer model on stabilization control simulator, it is able to narrow the difference between the test and the real condition by using more reliable parameters.

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Abbreviations

M :

Concentrated mass

C :

Damping coefficient

K :

Spring constant

ζ :

Damping ratio

η :

Loss factor (loss modulus)

C c :

Critical damping coefficient

E :

Material factor

E*:

Complex factor

G*:

Complex shear modulus

G′:

Storage modulus

G″:

Loss modulus

X :

Dynamic amplitude

x st :

Static deflection

ω :

Forcing frequency

ω n :

Natural frequency

t :

Time

φ :

Phase angle

K Br :

Radial stiffness of bearing

K ir :

Radial stiffness of elastomer

K Ba :

Axial stiffness of bearing

K ia :

Axial stiffness of elastomer

C r :

Radial damping coefficient of elastomer

C a :

Axial damping coefficient of elastomer

f n_Radial :

Radial natural frequency of elastomer

f n_Axial :

Axial natural frequency of elastomer

k ita :

Axial stiffness of elastomer

k itr :

Radial stiffness of elastomer

K T_Radial :

Total radial stiffness of elastomers

K T_Axial :

Total axial stiffness of elastomers

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Authors

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Correspondence to Ik-jin Lee.

Additional information

Recommended by Associate Editor Daeil Kwon

Sangwon Kim recevied a M.S. degree in Mechanical Engineering from Yonsei University. He joined ADD in 2005. He is currently a Ph.D. candidate in Mechanical Engineering at KAIST, Korea. His research interests include optomechanical design and system analysis.

Ikjin Lee is an Associate Professor of Mechanical Engineering at KAIST, Korea. He received his Ph.D. in Mechanical Engineering at the Unversity of Iowa. He jointed KAIST in 2013. His current research interests include system reliability analysis and design optimization, surrogate modeling, and system robustness analysis and design.

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Kim, Sw., Youn, Sk., Lee, Ij. et al. Identification of elastomeric isolator parameters on air-borne EO/IR camera with multi-axis gimbal. J Mech Sci Technol 33, 4605–4613 (2019). https://doi.org/10.1007/s12206-019-0903-z

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  • DOI: https://doi.org/10.1007/s12206-019-0903-z

Keywords

  • Elastomeric isolator
  • Dynamic parameter
  • Inverse analysis
  • 3 dB method
  • EO/IR camera