Adaptive Servoregulation of a Projectile Fin Using Piezoelectric Actuator

This paper treats the question of adaptive control of a projectile fin using a piezoelectric actuator. The hollow projectile fin is rigid, within which a flexible cantilever beam with a piezoelectric active layer is mounted. The model of the fin-beam system includes the aerodynamic moment which is a function of angle of attack of the projectile. The rotation angle of the fin is controlled by deforming the flexible beam which is hinged at the tip of the rigid fin. It is assumed that the system parameters are completely unknown and that only the fin angle and its derivative are measured for synthesis. A linear combination of the fin angle and fin’s angular rate is chosen as the controlled output variable and an adaptive servoregulator is designed for the control of the fin angle and the rejection of the disturbance input (aerodynamic moment). In the closed-loop system, the fin angle asymptotically converges to the desired value and the elastic modes converges to their equilibrium values. Computer simulation is performed which shows that in the closed-loop system, the fin angle is precisely controlled in spite of uncertainties in the fin-beam parameters and the aerodynamic moment coefficients. Furthermore, a laboratory model of the projectile fin is developed and the adaptive controller is implemented for real-time control. Experimental results are presented which show that adaptive servoregulator accomplishes fin angle control.