KEYWORDS: Satellites, Composites, Sensors, Control systems, Linear filtering, Feedback control, Adaptive control, Actuators, Control systems design, Protactinium
In this paper, a novel application of adaptive composite structures, a University of Hawaii at Manoa (UHM) smart
composite platform, is developed for the Thrust Vector Control (TVC) of satellites. The device top plate of the UHM
platform is an adaptive circular composite plate (ACCP) that utilizes integrated sensors/actuators and controllers to
suppress low frequency vibrations during the thruster firing as well as to potentially isolate dynamic responses from the
satellite structure bus. Since the disturbance due to the satellite thruster firing can be estimated, a combined strategy of
an adaptive disturbance observer (DOB) and feed-forward control is proposed for vibration suppression of the ACCP
with multi-sensors and multi-actuators. Meanwhile, the effects of the DOB cut-off frequency and the relative degree of
the low-pass filter on the DOB performance are investigated. Simulations and experimental results show that higher
relative degree of the low-pass filter with the required cut-off frequency will enhance the DOB performance for a high-order
system control. Further, although the increase of the filter cut-off frequency can guarantee a sufficient stability
margin, it may cause an undesirable increase of the control bandwidth. The effectiveness of the proposed adaptive DOB
with feed-forward control strategy is verified through simulations and experiments using the ACCP system.
In this paper, the dynamic analysis of a satellite dish with respect to spherical polar coordinate system is investigated. In this complex three-dimensional case, the method of separation of variables is employed to obtain the explicit solution of the partial differential governing equation of the adaptive composite satellite dish. Then, the mode shape functions are expanded in combination of periodic functions, associated Legendre functions, and spherical Bessel functions. The validation of the theoretical model is performed by comparing the developed analytical mode shapes with finite element analysis mode shapes. Three actuator parameters, i.e., actuator number, location, and placement configuration are
considered in the Genetic Algorithms (GAs). Also, employing the developed model, the norm-2 of LQR optimal feedback gain vector is set as the objective function in the GAs to obtain the optimal actuator placement coupled with the control law, with which good structural vibration suppression as well as less control energy consumption can be achieved by the linear quadric regulator (LQR).
In this paper, the dynamic analysis of an Adaptive Circular Composite Plate (ACCP) with asymmetric constraints with respect to the angular coordinate system is investigated. Due to the asymmetric constrains, the shape functions of the circular plate could not be simply obtained from the partial differential equation by ignoring the angular dependency. Using the method of separation of variables, the mode shapes are expanded in Bessel series. The comparison of the developed analytical mode shapes with the Finite Element Method (FEM) mode shapes confirmed the validation of the analytical model. A modeling strategy using Rayleigh-Ritz method is presented to build the system model. Taking the effects of piezoelectric actuators on the dynamics of the ACCP into account, the optimal placement of the actuators is investigated. Also, employing the developed model, the simulation of the vibration control is implemented on the ACCP with one central simply support and three edge simply supports using LQR controller. The simulation results verify the best performance of the LQR controller with the optimal configuration for vibration suppression of the ACCP.
This paper presents an advanced strategy to determine the optimal configuration of piezoelectric actuators embedded in
an adaptive circular composite plate (ACCP) with one central support and three simply supports on the edges for active
vibration suppression. The modeling strategy combines the Finite Element Analysis (FEA) and the transfer function
estimation technique taking into account the effects of piezoelectric patches on the dynamics of the structures. To obtain
the optimal actuator locations coupled with the control law, the linear quadric regulator (LQR) is chosen as a controller
to achieve maximum structural vibration suppression with minimum control energy consumption, where the norm-2 of
the LQR optimal feedback gain vector is set as the objective function of the optimization strategy. Due to their
effectiveness in searching optimal design parameters and obtaining globally optimal solution, the Genetic Algorithms
(GAs) are applied to fmd the optimal actuator configuration and placement among 8 possible configurations. Finally,
several simulations are performed using the LQR with five typical actuators configurations including the optimal
configuration given by the GAs. The results show that a substantial saving in the objective function as well as a
significant vibration reduction can be obtained when the optimal configuration of the actuators is adopted.
In this paper, a model of the adaptive composite panel surfaces with piezoelectric patches is built using the Rayleigh-Ritz method based on the laminate theory. The interia and stiffness of the actuators are considered in the developed model. An optimal actuator location has been proved to be desirable since the piezoelectric actuators often have limitations of delivering large power oiutputs. Due to its effectiveness in seraching optimal design parameters and obtaining globally optimal solutions, the genetic algorithm has been applied to find optimal locations of piezoelectric actuators for the vibration control of a smart composite beam. In addition, the effects of population size, the crossover probability, and the mutation probability on the convergence of the genetic algorithm are investigated. Meanwhile, linear quadric regulator (LQR) and disturbance observer (DOB) are employed for the vibration suppression of the optimized adaptive composite beam (ACB). The experimental results show the robustness of the DOB, which can successfully suppress the vibrations of the cantilevered ACB according to the optimization results in an uncertain system.
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