KEYWORDS: Satellites, Composites, Finite element methods, Actuators, Smart structures, Data modeling, Structural design, Sensors, Control systems, Active vibration control
This research focuses on a finite element analysis of active vibration suppression capabilities of a smart
composite platform, which is a structural interface between a satellite main thruster and its structure and
possesses simultaneous precision positioning and vibration suppression capabilities for thrust vector control
of a satellite. First, the combined system of the smart composite platform and the satellite structure are
briefly described followed by the finite element modeling and simulations. The smart platform
piezoelectric patches and stacks material properties modeling, for the finite element analysis, are developed
consistent with the manufacturer data. Next, a vibration suppression scheme, based on the modal analysis,
is presented and used in vibration suppression analysis of satellite structures of the thrust vector under the
thruster-firing excitation. The approach introduced here is an effective technique for the design of smart
structures with complex geometry to study their MIMO active vibration suppression capabilities.
This paper focuses on the development of an ANSYS finite element analysis (FEA) environment with integrated PID control scheme for simultaneous precision positioning and vibration suppression of smart composite structures with piezoelectric flat patches acting as actuators. This environment includes three modules: structural modeling, PID controller design, and dynamic analysis of smart structures. Two types of PID controllers are investigated, namely, PID vibration suppression (PID-VS) controller and PID simultaneous precision positioning and vibration suppression (PIDSPPVS) controller. The PID-VS controller is suitable to perform only vibration suppression with no positioning capability. The PID-SPPVS controller is equipped with SPPVS capabilities. The characteristics of individual control gains and their behavior with respect to each other for the two PID controllers are also studied. The gain selection for the PID-VS controller is based on obtaining the best VS while the gain selection for the PID-SPPVS controller is based on achieving the best positioning accuracy and VS simultaneously. In this study, a horizontal cantilevered graphite/epoxy composite beam with one surface-mounted ACX piezoelectric flat patch located at the beam root is first modeled. Next, the FE modal analysis is performed to determine the natural frequencies and hence the time step interval
needed for the FE transient analysis. During the transient analysis, the mid-point of the beam tip is subjected to different types of external excitations such as sine loadings with different frequencies as well as random forces to evaluate the two PID controller performances. It is demonstrated that the FEA model with integrated PID-SPPVS controller is able to reach the desired position in a much shorter time in comparison to the PID-VS controller. Vibration amplitude reduction capabilities for the both PID controllers are very similar, although the PID-VS controller performs slightly better. This study also implies that the integrated FEA environment, consisting of the structural modeling of active composite structures with piezoelectric flat patches, modal and transient analyses, controller design, and simulation, provides a powerful tool for the design, analysis, and control of smart structures with SPPVS capabilities.
KEYWORDS: Actuators, Piezoelectric effects, Sensors, Finite element methods, Composites, Current controlled current source, Modal analysis, Ferroelectric materials, Chemical elements, Active vibration control
This work utilizes a Direct Constant Voltage (CV) Scheme as a versatile tool to study piezoelectric actuator performance effectiveness either surface-mounted or embedded. To achieve this goal calculated control Constant Voltage is employed for active vibration suppression. This paper introduces a closed form formula that replaces Design Charts for a faster and easier way to calculate actuator voltage required for active vibration suppression. To perform a comprehensive study, three finite element models (FEMs) are developed. The first FEM considers non-collocated surface-mounted piezoelectric patches as sensor and actuator for beams with varying thicknesses. The second FEM deals with embedded non-collocated piezoelectric patches as sensor and actuator for beams with varying thicknesses and constant number of constraint layers. For this embedded case one extra layer is needed to cover the piezoelectric patch and one extra cut-out layer to fill the area around the piezoelectric patch compared to the surface-mounted. The third FEM focuses on beams having constant thicknesses with variable number of constraint layers and non-collocated embedded piezoelectric patches. A surface-mounted ACX piezoelectric patch acts as a shaker is all three FEMs. Numerical and experimental results were compared and excellent comparisons were obtained. The Direct Constant Voltage Scheme can offer useful information into the actuator performance effectiveness in terms of: 1) the piezoelectric actuator performance effectiveness with respect to the laminate thicknesses and actuator distance from the beam neutral axis either surface-mounted or embedded, and 2) the influence of the constant and variable number of constraint layers on the embedded piezoelectric effectiveness for beams with variable and constant thicknesses.
KEYWORDS: Actuators, Piezoelectric effects, Sensors, Composites, Finite element methods, Current controlled current source, Modal analysis, Ferroelectric materials, Chemical elements, Ceramics
This study focuses on the effectiveness of the piezoelectric patches either surface-mounted or embedded for different composite laminate thicknesses. Primarily, two finite element models (FEMs) are considered for this study. The first FEM considers beams with varying thicknesses and non-collocated surface-mounted piezoelectric patches as sensor and actuator. Typical results are shown for four and eight layers graphite/epoxy composite laminates. The second FEM deals with embedded non-collocated piezoelectric patches as sensor and actuator for beams with varying thicknesses. For the embedded case one extra layer is needed to cover the piezoelectric patch and one extra cut-out layer to fill the area around the piezoelectric patch. Therefore, a composite beam for the embedded case in comparison to the surface-mounted case has always four extra constraint layers. Typical results, for these two cases, are compared for the beams with the same number of inner layers (i.e. four and eight). A surface-mounted ACX piezoelectric patch acts as a shaker in both FEMs. Numerical and experimental results from modal and harmonic analyses were compared and excellent comparisons were achieved. Cross-examination between these two FEMs determined the following. 1) The effectiveness of piezoelectric patches acting as an actuator with respect to the laminate thicknesses and the actuator distance from the beam neutral axis for both cases. 2) The influence of the constraint layers on the performance of the embedded piezoelectric patches.
KEYWORDS: Actuators, Composites, Sensors, Finite element methods, Ferroelectric materials, Adaptive optics, Ceramics, Space operations, Beam shaping, Active vibration control
This paper focuses on various vibration suppression schemes for Active Composite Struts (ACS) and Active Composite Panels (ACP). Dynamic responses of struts and panels using piezoelectric sensors and actuators were analyzed and evaluated by the finite element method. Four different vibration suppression schemes for ACS and ACP have been studied. Objectives were to first investigate various schemes for active vibration suppression that can be determined directly without trial and error, and Second to determine a scheme that can completely suppress the vibration and is easy to use. Four schemes were considered, namely, 1) constant voltage (CV), 2) optimum voltage (OV), 3) corresponding voltage (COV) and 4) truncated corresponding voltage (TCOV) schemes. This paper also discusses the pros and cons of each and provides guidelines for active vibration suppression of intelligent structures.
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