Richard Russ

Manufacturing and Testing of Active Composite Panels with Embedded Piezoelectric Sensors and Actuators

This work presents the manufacturing and testing of active composite panels (ACPs) with embedded piezoelectric sensors and actuators. The composite material employed here is a plain weave carbon/epoxy prepreg fabric with 0.30 mm ply thickness. A cross-ply type stacking sequence is employed for the ACPs. The piezoelectric flexible patches employed here are Active Fiber Composite (AFC) piezoceramics with 0.33 mm thickness. Composite layers with openings are used to fill the space around the embedded piezo patches to minimize the problems associated with ply drops in composites. The AFC piezoceramic patches were embedded inside the composite laminate. High-temperature wires were soldered to the piezo leads, insulated from the carbon substructure by high-temperature materials, and were taken out of the composite laminates employing cutout hole, molded-in hole, and embedding techniques. The laminated ACPs with their embedded piezoelectric sensors and actuators were vacuum bagged and co-cured inside an autoclave employing the cure cycle recommended by the composite material supplier. The Curie temperature of the embedded piezo patches should be well above the curing temperature of the composite materials as was the case here. The capacitance of the piezoelectric patches was measured before and after cure for quality control. The manufactured ACPs were trimmed and then tested for their functionality. A finite element analysis (FEA) model was developed to verify the free expansion of the AFC FEA. Next, the FEA model of the manufactured ACP was developed based on the AFC FEA free expansion model and was employed to test the functionality of the AFCs embedded within the ACPs. Both static and dynamic FEA results of the modeled ACPs showed very good agreements with their corresponding experimental results. Finally, vibration suppression as well as simultaneous vibration suppression and precision positioning tests, using Hybrid Adaptive Control (HAC), were successfully conducted on the manufactured ACP beams and their functionality was further demonstrated. The advantages and disadvantages of ACPs with embedded piezoelectric sensor and actuator patches manufactured employing the abovementioned three wires out techniques are also presented in terms of manufacturing and performance.

Finite Element Charts and Active Vibration Suppression Schemes for Smart Structures Design

This article employs a finite element method to introduce Displacement-Load-Sensor voltage-Actuator voltage (DLSA) Design Charts and associated vibration suppression schemes; namely, Constant Voltage (CV), Optimum Voltage (OV), Corresponding Voltage (COV), and Truncated Corresponding Voltage (TCOV), to develop actuator control voltages with amplitude and phase information for the design of smart structures with piezoelectric sensors and actuators for active vibration suppression. These techniques can be used to (a) design the location, size, and number of actuators without resorting to complex control strategies or formal optimization techniques, (b) investigate the actuation effectiveness of surface-mounted versus embedded piezoelectric patches in similar composite structures, and (c) determine actuator control voltages analogous to a feedforward open-loop control technique. Guidelines are presented for the development of DLSA Design Charts. In addition, closed form analytical equations that can replace DLSA Design Charts, are developed and presented due to their ease of use. An Active Composite Panel (ACP) with a surface-mounted piezoelectric patch actuator for lateral vibration suppression and an Active Composite Strut (ACS) with a piezoelectric stack actuator for axial vibration suppression are considered. The ACP and ACS are employed to demonstrate the applications of the introduced DLSA Design Charts and the vibration suppression schemes for vibration suppression and actuator placement optimization. The vibration suppression of both ACP and ACS is significant over a frequency range encompassing several resonances, and is indicated by the Suppressed Vibration Energy (SVE) index. This investigation shows that the optimum location of the actuator depends on the structural mode shape, based on the criteria of maximum SVE and minimum actuator power. In general, the actuator should be placed on the panel on a sub-area, where the sum of normal strains is maximum. However, a preferred location can be determined over a range of frequencies that encompass more than one natural frequency.

A finite element analysis approach with integrated PID control for simultaneous precision positioning and vibration suppression of smart structures

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.

Vibration suppression schemes for active composite struts and panels

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.

Vibration suppression of satellites using multifunctional platforms

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.

Piezoelectric performance effectiveness for active composite panels with surface-mounted and embedded sensors and actuators using direct constant voltage scheme

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.

A Comparative Study on the Effectiveness of Piezoelectric Patches For Active Composite Panels With Surface-Mounted and Embedded Sensors and Actuators

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.

Manufacturing and Active Control Testing of Active Composite Panels With Embedded Piezoelectric Sensors and Actuators: Wires Out by Cut-Holes and Embedding

This work presents manufacturing and testing of active composite panels (ACPs) with embedded piezoelectric sensors and actuators. The composite material employed here is a plain weave carbon/epoxy prepreg fabric with about 0.3 mm ply thickness. A cross-ply type stacking sequence is employed for the ACPs. The piezoelectric flexible patches employed here are Active Fiber Composites with 0.33 mm thickness. Composite cut-out layers are used to fill the space around the embedded piezo patches to minimize the problems associated with ply drops in composites. The piezoelectric patches were embedded inside the composite laminate. High-temperature wires were soldered to the piezo leads, insulated from the carbon substructure by high-temperature materials, and were taken out of the composite laminates employing both cut-hole and embedding techniques. The laminated ACPs were co-cured inside an autoclave employing the cure cycle recommended by the composite material supplier. The Curie temperature of the embedded piezo patches should be well above the curing temperature of the composite materials as was the case here. The manufactured ACPs were trimmed and then tested for their functionality. Vibration suppression as well as simultaneous vibration suppression and precision positioning tests, using Hybrid Adaptive Control techniques were successfully conducted on the manufactured ACP beams and plates and their functionality were demonstrated. The advantages and disadvantages of ACPs manufactured by taking the wires out employing cut-holes and embedding techniques, in terms of manufacturing and performance, are presented.Copyright