Aeroservoelastic Modeling and Sensitivity Analysis with Strain Actuators

• Published in: Journal of aircraft 2006-07, Vol.43 (4), p.1235-1241
• Main Authors: Karpel, Moti, Moulin, Boris
• Format: Article
• Language: English
• Subjects: Aerodynamics; Aircraft; Applied sciences; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Mathematical models; Mechanical engineering. Machine design; Physics; Sensitivity analysis; Solid mechanics; Static elasticity (thermoelasticity...); Structural and continuum mechanics; Vibration, mechanical wave, dynamic stability (aeroelasticity, vibration control...)
• ISSN: 0021-8669; 1533-3868
• DOI: 10.2514/1.19279

Mathematical models of aeroservoelastic systems are expanded to facilitate the use of distributed strain actuators in automated design processes. Strain actuators, such as piezoelectric patches, can change the shape of lifting surfaces by introducing structural strains due to electric voltage commands. The voltage-strain relations, the overdetermined nature of the elastic actuator-structure equilibrium, the relatively large number of involved interface coordinates, and the high importance of local strains that typically limit the actuator performance require substantial modifications in the modeling process compared with that with common control-surface actuators. A control mode is defined by the static deformations due to a unit static voltage command. Huge dummy masses are used to generate the control modes and their mass coupling with the elastic modes as part of a standard normal-modes analysis. State-space aeroservoelastic equations are constructed using the minimum-state rational aerodynamic approximation approach. Analytical expressions are given for the sensitivity of the system coefficient matrices and the associated aeroservoelastic stability and response parameters with respect to the actuator properties. A numerical application of an unmanned aerial vehicle with a piezoelectric-driven control surface is given. The example demonstrates the modeling process, some aeroelastic response parameters to control commands, and the associated sensitivity analysis.