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.