Volkan Nalbantoglu

System identification with generalized orthonormal basis functions: an application to flexible structures

Abstract This paper presents an application of a multi-input/multi-output identification technique based on system-generated orthonormal basis functions to a flexible structure. A priori information about the poles of the system, part of which corresponds to the natural frequencies of the structure, is used to generate the orthonormal basis functions. A multivariable model is identified for the experimental flexible structure by using these orthonormal basis functions. It is shown that including a priori knowledge of the system dynamics via the use of orthonormal basis functions into the identification process has the advantage of reducing the number of parameters to be estimated. The multivariable model is used to design an H∞ controller for the experimental structure to suppress vibrations. The controller is implemented on the structure and very good agreement is obtained between the simulations and the experimental results.

Active Vibration Control of a Smart Fin

This paper summarizes the design and wind tunnel experimental verifications of robust H∞ controllers for active vibration suppression of a dynamically scaled F-18 vertical smart fin. The smart fin consists of a cantilevered aluminium plate structure with surface bonded piezoelectric (Lead-Zirconate-Titanete, PZT) patches, Integrated Circuit Piezoelectric (ICP) type accelerometers and strain gauges. For H∞ controller design, the transfer function of the fin was first estimated outside the wind tunnel. Then, experiments were carried out to determine the aeroelastic characteristics of the smart fin at free flow and vortical (i.e. buffet) flow conditions. Variable air speeds and Angle of Orientations (AoO) were considered in both flow conditions. Significant shifts in vibration frequencies and the damping ratios were observed at the various values of airspeed and AoO. Taking into account these variations, the H∞ controllers were designed to suppress the fin’s buffeting response at the first and second bending and first torsional modes. A second set of wind tunnel experiments was conducted to verify the performance of the designed H∞ controllers at various flow scenarios. Successful vibration suppression levels were obtained within the desired frequency intervals.

Active Vibration Control of a Smart Beam by Using a Spatial Approach

The vibration control is an important and rapidly developing field for lightweight flexible aerospace structures. Those structures may be damaged or become ineffective under the undesired vibrational loads they constantly experience. Hence, they require effective control mechanism to attenuate the vibration levels in order to preserve the structural integrity. The usage of smart materials, as actuators and/or sensors, has become promising research and application area that gives the opportunity to accomplish the reduction of vibration of flexible structures and proves to be an effective active control mechanism.

Gyro-Bias Estimation Filter Design for the Stabilization Accuracy Enhancement of Two Axes Gimbaled Sighting Systems

Abstract In this study the development of a bias estimation technique for the gyroscopes used in stabilization of two axes gimbaled sighting systems is presented. Due to their size and cost limitations, generally, two axes gyroscopes with high bias values are used on such systems. These high bias values cause the sight-line to drift from the target direction and result in a need for frequent corrections from the operator. The proposed technique uses the aiding from the inertial navigation system (INS) of the host vehicle and the kinematical constraints to enable the complete attitude solution of the sighting system with only using a two axes gyroscope. This full attitude solution is used in designing an extended Kalman filter which estimates the gyroscope biases. As for the simulations, a dynamical model of the sighting system, carried on a host land vehicle, is developed and the performance improvement resulting from the bias corrections is demonstrated with simulations using this model.

Choosing Sensor Configuration for a Flexible Structure Using Full Control Synthesis

Optimal locations and types for feedback sensors which meet design constraints and control requirements are difficult to determine. This paper introduces an approach to choosing a sensor configuration based on Full Control synthesis. A globally optimal Full Control compensator is computed for each member of a set of sensor configurations which are feasible for the plant. The sensor configuration associated with the Full Control system achieving the best closed-loop performance is chosen for feedback measurements to an output feedback controller. A flexible structure is used as an example to demonstrate this procedure. Experimental results show sensor configurations chosen to optimize the Full Control performance are effective for output feedback controllers.