Session: 17-01-01 Research Posters

Paper Number: 70469

Start Time: Thursday, 02:25 PM

70469 - Active Vibration Control of Aerospace Structural Systems for Specified Damping 

Active vibration control is needed in aerospace structural systems, such as large space structures, twin tailed high performance aircraft operating at high angles of attack and helicopters. Goh and Caughy have shown that vibration controller design can significantly benefit from the use of second order systems ln the controller design.  In this paper, the subject of the design of active vibration control of buffet induced vibrations in high performance twin tailed aircraft is discussed using a combination of acceleration feedback and positive position feedback in second order systems.  The goal is to design controllers to increase the closed loop damping ratio of the structural dynamic system to a specified level that would reduce the vibrations to the required level within a time frame of interest. Unlike the approach of Fanson and Caughy that required a trial and error approach to design the controller parameters, because they had more unknowns and fewer equations.  The problem is now formulated to obtain closed form solutions. This is accomplished by developing a procedure to design second order controllers to obtain the desired closed loop damping while maintaining the stability of the closed loop structural dynamic system.  The[SH1]  design procedure starts with a coincident closed loop frequency for each mode which is followed by a perturbation procedure to seek optimum solutions. The design procedure also yields the needed control authority that should be provided by the actuator. An option to increase the control authority by the use of[SH2]  offset piezoceramic stack actuator assemblies are discussed. The designed controllers are applied to   buffet induced vibrations of a high performance aircraft at high angles of attack.  This example also illustrates     the control authority of the piezoceramic   stack structural assemblies

 

We started with the frequency response function of the vertical tails of the full scale high performance aircraft at high angles of attack. Then, we designed and constructed a one sixteenth size aeroelastic model. We determined the frequency response function of the model through tests. We selected four natural frequencies in the range of 0 to 102 Hz . We designed p(acf) + (1-p)PPF controllers to increase the closed loop damping ratios from 0,02 to 0,25. With p=1, we only have acceleration feedback. With p=0, we only have positive position feedback controllers. For different values p, we  obtained the controller parameters and the actuator authorities. Then, we designed piezoceramic actuator assemblies to provide the needed actuator authorities and verified the control authority through tests that used the open loop responses. The closed loop system was validated through computer simulation and  wind tunnel tests . Through computer simulationand preliminary tests, it was realized that the actuators had to be seet at an angle to control both bending and torsional modes.        

 

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Presenting Author: Sathya Hanagud Georgia Inst Of Tech

Authors:

Sathya Hanagud Georgia Institute of Technology