An Active Composite Reflector System for Correcting Thermal Deformations

Smart actuators, made of smart materials, are becoming more attractive in many applications because smart materials are not subjected to wear and does not require lubrication during services. Piezoelectric materials are a group of the many attractive smart materials that are being investigated for many applications today. Piezoelectric materials show fast responses, high efficiency/accuracy and operate on a large bandwidth. Composite materials are of interest because of their design flexibility and because they are lighter than other materials commonly used in aircraft and other applications. For the research reported here, a piezoelectric material was embedded in a composite material to form a piezoelectric composite actuator. This research was conducted to expand our knowledge of piezoelectric composite material actuators, and originated from the need to control air flow separation over an airfoil. There is a need to build a profound knowledge about such actuators before they can be implemented in an airfoil, and to understand which parameters influence the behaviour of piezoelectric composite material actuators under static and dynamic operating conditions. The actuators were manufactured and tested under static and dynamic conditions and the experimental results were compared to the finite element models. The models were incorporated with piezoelectric material properties that were determined experimentally. The results showed that a piezoelectric material’s response to an input stimulant, e.g. electric voltage and frequency, influences the actuator’s behaviour.

The shock resistance of structures is of current interest of academia and industry. Sandwich structures have been proposed as alternatives to conventional monolithic structures in order to enhance the shock resistance. Sandwich structures are widely used in many important fields, such as ship, aircraft, automotive and aerospace industries, packaging and construction engineering. In this study, a number of experiments were conducted to investigate the structural response of dynamically loaded on clamped (both end) 1mm thick monolithic aluminium beams and rubber core sandwich beams of 3.02 mm and 4.02 mm thicknesses impacted by a blunt nosed cylindrical projectile made of mild steel of diameter 12.8 mm, length 30.2 mm and mass 0.03018 Kg in sub ordinance velocity range (20 to 110 m/s). Sandwich structure consists of two face sheets of aluminium adhered to a low-density rubber core. The failure of composite specimens observed in the tests can be classified with respect to the front face sheet, core and back face sheet, respectively Different parameters like impact velocity, residual velocity, velocity drop, energy absorbed, kinetic energy, deflection, dimensionless external dynamic energy, and dimensionless maximum transverse permanent deformation were observed experimentally and calculated analytically with the help of work in the past. Three modes of failure of beams have been found during the experiment on monolithic and rubber core sandwich beams like mode-1: Fracture at the point of strike i.e. tearing; mode-2: Fracture at one or both support either on front face sheet or on back face sheet of beam i.e. end shear; mode-3: Fracture at the point of strike with bulging (cup shape) and after fracture beam turnaround from the support (in case of monolithic) or Fracture at the point of strike without bulging on front face sheet and after fracture on the back face sheet with bulging and beam turnaround from the support (in case of sandwich beam).

Piezoelectric actuators can offer micro/nano-level precision actuating ability and have been employed in different applications. For the piezoelectric actuating systems, the output actuating performance is affected not only by the internal non-smooth hysteresis but also by the operating load and the excitation frequency. To improve the actuating precision, predicting the nonlinear behaviour of the piezoelectric actuating system is essential for effective designs of control approaches. In this paper, a modified rate-dependent Prandtl–Ishlinskii model is presented to explore the coupling effects analytically between the internal hysteresis and the operating frequency with the external loads and predict the output behaviour of the piezoelectric actuating system accurately. The proposed modelling method is testified on a piezoelectric actuating platform under broad ranges of excitation frequencies (1–80 Hz) and external loads (0–0.5 kg), and the comparison results using the rate-dependent Prandtl–Ishlinskii (RDPI) model are also provided to prove the precision of the proposed method. Combining with the modified RDPI model, a guaranteeing preselected tracking controller is developed to ensure the output performance, and a set of tracking experiments under different frequencies with load is performed. The experimental results compared with PID control performance validate the effectiveness of the proposed prescribed performance control method and its high actuating performance against the adverse effects from the external hysteresis nonlinearities and external loads.

New aircraft propulsion architectures increasingly rely on the turbofan as the main thrust generating component. Improving turbofan efficiency is therefore a promising approach to boosting overall propulsive efficiency, and thereby enhancing the sustainability of future aircraft engine architectures. Although current turbofans already operate at high on-design efficiencies, the engine and mission specific operating line determines operating periods with increased losses. To improve off-design operation, variable systems are increasingly investigated. As an alternative to pitch variable fan blading and variable nozzle geometries, this research proposes shape-adaptive fan blading. Applying piezoelectric Macro Fiber Composite actuators to the fan blades allows for an adjustment of the span-wise twist and turning of the rotor to match the inflow and flow deflection requirements occurring during off-design operation. To investigate the aerodynamic effect induced by morphing turbofan blades, a scaled test rig fan design is introduced. The low hub-to-tip ratio fan design is tailored for an increased deformability towards a piezoelectric actuation, while maintaining a sufficiently high aerodynamic on-design efficiency. The design measures considered include the rotor main dimensions, the blade profile design as well as 3D design features, such as sweep and dihedral. Since the adaptive fan design favours actuators that aim for an elevated blade cambering, corresponding actuation concepts are investigated in further detail. Considering a fan test rig set-up without core and a fixed nozzle, FEA morphing simulations are coupled with stationary 3D RANS passage CFD simulations and the detailed aerodynamic morphing effects are discussed. Finally, integral performance map effects are evaluated with respect to the stationary test rig working line, also taking into account the simplifications made during the morphing evaluation.

Adaptive sliding mode control with hysteresis compensation-based neuroevolution for motion tracking of piezoelectric actuator

A great amount of research is being conducted to incorporate smart material actuators in aerospace applications such as (1) turbo fan engines (2) servo flap actuators for helicopter rotor control. For example, a piezoelectric stack actuator, coupled with mechanical or hydraulic amplification could provide the actuation required for the variable pitch fan system with a potentially higher level of reliability. In addition, piezoelectric actuation system could do so at a lower overall weight. However, there are limitations with existing piezoelectric stack actuators relative to power requirements. Therefore, a new approach has been investigated to improve these characteristics in order for piezoelectric stacks to be a feasible solution for these types of large scale applications. A new configuration involving dielectric, conductor, piezoelectric material in a particular sequence of stack actuation is examined and experimented. A nonlinear lumped parameter model of a piezoelectric stack has been developed to describe the behavior for the purpose of control actuation analysis.

A driving power for piezoelectric actuators is presented in this paper. The power supply is the key component in piezoelectric micro displacement system. The dedicated DC driving power is designed toward the piezoelectric micro angle actuator, through changing the charging current of piezoelectric ceramic to control its movement speed, thereby control the displacement. The positive voltage float regulating expansion circuit is consisted of LM723CN, to realize the stable controllable voltage output with high precision. The high voltage linear amplification circuit uses discrete components design method. Through the two stage amplifying drive signal, a closed loop negative feedback circuit system is set, and it have small output resistance, strong load capacity. The stability of the output voltage is improved. The system meets the requirements of the high precision, strong drive capabilities, simple structure and good stability.

Thermal postbuckling analysis of laminated cylindrical shells with piezoelectric actuators

A new class of materials known as ‘functionally graded materials’ (FGMs) has emerged recently, in which the material properties are graded but continuous particularly along the thickness direction. In an effort to develop the super heat resistant materials, Koizumi [1] first proposed the concept of FGM. These materials are microscopically heterogeneous and are typically made from isotropic components, such as metals and ceramics. In the quest for developing lightweight high performing flexible structures, a concept emerged to develop structures with self-controlling and self-monitoring capabilities. Expediently, these capabilities of a structure were achieved by exploiting the converse and direct piezoelectric effects of the piezoelectric materials as distributed actuators or sensors, which are mounted or embedded in the structure [2, 3]. Such structures having built-in mechanisms are customarily known as ‘smart structures’. The concept of developing smart structures has been extensively used for active control of flexible structures during the past decade [4]. Recently considerable interest has also been focused on investigating the performance of FG plates integrated with piezoelectric actuators. For example, Ootao and Tanigawa [5] theoretically investigated the simply supported FG plate integrated with a piezoelectric plate subjected to transient thermal loading. A 3-D solution for FG plates coupled with a piezoelectric actuator layer was proposed by Reddy and Cheng [6] using transfer matrix and asymptotic expansion techniques. Wang and Noda [7] analyzed a smart FG compositestructure composed of a layer of metal, a layer of piezoelectric and a FG layer in between, while in [8] a finite element model was developed for studying the shape and vibration control of FG plates integrated with piezoelectric sensors and actuators. Yang et al. [9] investigated the nonlinear thermo-electro-mechanical bending response of FG rectangular plates covered with monolithic piezoelectric actuator layers; most recently, Huang and Shen [10] investigated the dynamics of a FG plate coupled with two monolithic piezoelectric layers undergoing nonlinear vibrations in thermal environments. All the aforementioned studies focused on the rectangular-shaped plate structures. However, to the authors’ best knowledge, no researches dealing with the free vibration characteristics of the circular FGM plate integrated with the piezoelectric layers has been reported. Therefore, the present work attempts to solve the problem of providing analytical solution for free vibration of thin circular FG plates with two full size surface-bonded piezoelectric layers on the top and the bottom of the FG plate. The formulations are based

This paper presents the design and the realisation of a technique to attenuate the hysteresis nonlinear phenomenon of piezoelectric actuators. Piezoelectric actuator are widely utilised for deformable mirrors used for MOAO and power laser beam shaping techniques. The nonlinearities of piezo are usually iteratively compensa- ted using closed-loop set-ups. In open-loop control, the hysteresis and the creep of the piezo cannot be corrected, thus this nonlinearities must be removed or at least minimised. The concept has been demonstrated on high displacement Amplified Piezoelectric Actuators (APA) mounted in a Fabry-Perot interferometer. The hysteresis attenuation technique aims to assist the Fabry-Perots nano-positioning control system to attain its main scientific specification. In such system, each APA has a maximum stroke of 270 μm within a 170 V (-20 V to +150 V) range and is used to position a high reflective mirror plate. The Fabry-Perots nano-positioning control system is specified to limit the APAs positioning steady-state noise to 3nm rms, but the hysteresis limits the positioning accuracy. In order to attenuate hysteresis, a hybrid amplifier circuit built with a high power operational amplifier has been designed and applied for each APA. The experiments results show that the hysteresis effect has almost been eliminated, and consequently the positioning steady-state noise can significantly been reduced. Because of the excellent results of this hybrid amplifier, a patent application has been introduced in June 12, 2015 under number No.1555381 and is being reviewed now.

In this research, a new approach is proposed to enhance the effectiveness of piezoelectric actuators. Through mechanical tailoring, the resonant frequencies of the actuation system (this includes the piezoelectric actuator and the related mechanical and electrical elements for actuation) can be tuned to the required actuation frequencies. This obviously will increase the authority (both stroke and force) of the actuation system. However, the resonant actuation system can be hard to control and nonrobust, due to its narrow operating bandwidth. This issue can be resolved through electric circuit tailoring. With the aid of a network of inductance, resistance, and negative capacitance, the actuation resonant peak can be significantly broadened and flattened. In this case, one can achieve a high authority actuation system without the negative effects of resonant problems. The electrical networks can also achieve a fail-safe system due to its passive shunting character. The proposed concept is evaluated using a PZT tube actuator for trailing edge flap control of rotorcraft blades. Promising results are demonstrated, showing that the treatment can indeed create a high-authority and robust actuation system that satisfies the performance requirements of the example application. Also, the proposed concept is verified by experiments using an equivalent circuit model with a synthetic inductor and a negative impedance converter of capacitance.

In this paper, a robust controller for a piezoelectric actuator system with dominant hysteresis is developed. First, the external part of a transformed piezoelectric actuator via a feedback linearizing control consists of a linear dynamic system with uncertainties. The uncertainty is not necessarily to satisfy the matching condition. A reference model with the desired amplitude and phase properties for the time-varying trajectory is given to obtain an error model. Then, an equivalent control using the known part of system dynamics is designed to achieve the desired control behavior. Furthermore, the uncertainties are tackled by the switching control. The proposed control contains a feedback linearizing control with a reference model and a sliding-mode control including an equivalent control and a switching control. Finally, the stability of the overall system is verified by the Lyapunov theory so that the ultimately bounded tracking is accomplished. Simulations of piezoelectric actuator are presented to verify the usefulness of the proposed control.

Multiscale thermopiezoelectric analysis of laminated plates with integrated piezoelectric fiber composites

Piezoelectric distributed actuators are exhaustively utilized in control of the structural deformation/vibration. These actuators are also used in the form of smart composite of which active fiber composite (AFC) and macro-fiber composite (MFC) are the most popular smart composites. In the present work, few shortcomings of MFC/AFC actuator in its structural applications are identified and those are alleviated through the proposition of a short piezoelectric fiber-reinforced composite (SPFRC) actuator. The SPFRC is composed of equally spaced coaxial short piezoelectric fibers embedded within the polymer matrix. Every fiber is poled along its length that yields maximum piezoelectric stress/strain within the composite along the same direction in effect of co-directional applied electric field. This piezoelectric effect quantified by the coefficient (e11) is the main parameter in its use as an actuator with a special arrangement of electrodes in microscale. The SPFRC is designed with an objective of improved magnitude of major effective coefficient (e11), and it is performed through a continuum micro-mechanics finite element analysis of its effective electro-elastic properties. The actuation-capability of SPFRC actuator according to its present design is verified by analyzing the geometrically nonlinear electro-elastic deformations of a simply supported smart beam. The micro-mechanics analysis reveals a significant magnitude of e11 of SPFRC although it is lesser than the case of continuous fibers within the similar composite. However, the analysis of smart beam reveals better actuation-capability of the smart composite actuator when short fibers are used instead of continuous fibers retaining the same applied voltage and electrodes.

Piezoelectric ceramic wafers embedded or surface mounted are able to generate transverse forces to control structural shape and vibration. These actuators are excited by applying an electric field through the thickness of the piezoelectric ceramic wafer. The proper design of their dimensions such as wafer thickness, and applied actuation voltage will enhance the system reliability, and guarantee the optimal control authority. This paper shows that the force transfer from the piezoelectric ceramic wafer to the structure, rather than the shear stress transfer in bond lines, becomes a key issue in the design when the length relative to the thickness of the piezoelectric ceramic wafer is large. It should be noted at this point that the shear stress distribution in the bond lines may influence the durability of the piezoelectric ceramic actuation system and, therefore, should also be considered when designing the system as a whole. This aspect of design is not discussed here. The force transfer is basically determined by the force transfer efficiency and block force in association with the wafer thickness. Therefore, this paper presents a design window for piezoelectric ceramic wafers bonded onto structures that is based on the relations between the force transfer and the wafer thickness, and also accounting for the applied actuation voltage and dielectric breakdown voltage of the piezoelectric material. The design window clearly describes the upper bound of the force transfer and the maximum value that can be achieved. It is also used to find an appropriate wafer thickness and actuation voltage when a minimum value of force transfer is required. In addition, an analytical model is developed in order to express the relation between the force transfer and the wafer thickness. This model is compared to the results from finite-element analysis. Limitations of the analytical model are described.