INVERSION-BASED ITERATIVE FEEDFORWARD-FEEDBACK CONTROL: APPLICATION TO NANOMECHANICAL MEASUREMENTS AND HIGH-SPEED NANOPOSITIONING

In this research, we used the self-designed piezoelectric actuated stage to achieve the nanometer level precise positioning control through the design of the fuzzy controller. A novel piezoelectric actuator structure - 4-9-9-14 piezoelectric actuator is constructed, and it is made of piezoelectric buzzer to drive the stage. The movement of the piezoelectric actuated stage is read and analyzed by means of NI PCI-6115 data acquisition card and LabVIEW software operating in conjunction with a linear encoder. The new consideration of tuning time T(subscript on) is used to place of traditional method of changing the magnitude of driving voltage to control the stepping distance of the stage. Under a constant driving voltage, the stride of the stage increases with time T(subscript on), and the stride of the stage decreases with time T(subscript on). According to the control experiment, the piezoelectric actuator stage would be reached below 1 μm levels by the fuzzy controller which is designed for this experiment, has been demonstrated. Furthermore, the purpose of control could be achieved by changing the time T(subscript on) which has been demonstrated.

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.

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.

A method to reduce vibration in a helicopter blade under a variable harmonic pressure loading using piezoelectric actuators is presented. The model of a helicopter blade is an equivalent aluminum plate. To decrease the amplitude in the resonant frequency range, piezoelectric actuators are set on the top of the plate. The results were obtained by using the ANSYS finite element code. The temperature analogy method instead of a variable pressure load is assumed for numerical analysis. The influence of piezoelectric actuators on the plate is considered. It is shown that the use of piezoelectric actuators to decrease the vibration of the plate is highly efficient. The most rational arrangements of piezoelectric actuators and the required amount of electric voltage are determined.

The present article reports the feasibility of the electrical energy generation from ambient low-frequency vibration using a piezoelectric material mounted on a bimorph cantilever beam actuator. A corresponding higher-order analytical model is developed using MATLAB in conjunction with finite element method under low-frequency with both damped and undamped conditions. An alternate model is also developed to check the material and dimensional viability of both piezoelectric materials (mainly focussed to PVDF and PZT) and the base material. Also, Genetic Algorithm is implemented to find the optimum dimensions which can produce the higher values of voltage at low-frequency frequencies (≤ 100 Hz). The delamination constraints are employed to avoid inter-laminar stresses and to increase the fracture toughness. The delamination has been done using a Teflon sheet sandwiched in between base plates and the piezo material is stuck to the base plate using adhesives. The analytical model is tested for both homogenous and isotropic material characteristics of the base material and extended to investigate the effect of the different geometrical parameters (base plate dimensions, piezo layer dimensions and placement, delamination thickness and placement, excitation frequency) on the model responses of the bimorph cantilever beam. It has been observed that when the base material characteristics are homogenous, the efficiency of the model remains higher when compared to the condition when it is of isotropic material. The necessary convergence behaviour of the current numerical model has been established and checked for the accuracy by comparing with available published results. Finally, using the results obtained from the model, a prototype is fabricated for the experimental validation via a suitable circuit considering Glass fibre and Aluminium as the bimorph material.

As the fatigue life of a piezoelectric actuator is relative to the service life of a piezoelectric pump,this paper carries out a fatigue life-related research.First,times of stress cycle corresponding to the ultimate stress is experimentally acquired when Pb(Zr,Ti)O3(PZT-5)ceramics suffers from the fatigue failure under an electro-mechanical coupling field.The number of samples selected at different levels of stress in the above experiment are discriminated and corrected by using the coefficient of variation.After data processing,a p-S-N double logarithm curve and its linear regression equation are obtained with the safety life at different levels of stress under conditions of 95% degree of confidence and 99.9% livability calculated respectively,which offers important and necessary data for the fatigue life calculation of piezoelectric actuator.Finally,the fatigue life of the piezoelectric actuator of a certain resonance-type air pump is calculated to be 4461 h with safety factor 1.25 by using ansys and hypothesis of fatigue damage accumulation.These results perfect the technical parameters of this air pump and the fatigue data,and the calculation method can be applied to the fatigue calculation of PZT-5 actuator in other kinds of piezoelectric pumps.

The piezoelectric actuating device that consist of piezoelectric material is known for large power density with simple structure. It can generate large force than the conventional actuator and it has also wide bandwidth with fast response in a compact size. To control the piezoelectric actuator, we need analog signal conditioning circuit as well as digital microcontrollers. Conventional microcontrollers are not equipped with analog part and need digital to analog converters in addition to the embedded analog to digital converters, which makes the system bulky compared with the small size of the piezoelectric devices. To overcome these weaknesses, we are developing single-chip controller that can handle analog and digital signals simultaneously using mixed signal FPGA technology. We used the Smart Fusion FPGA device that integrates ARM®Cortex-M3, analog interface and FPGA fabric in a single chip and offering full customization. It gives more flexibility than traditional fixed-function microcontrollers with the excessive cost of soft processor cores on traditional FPGAs. In this paper we introduce the design of a single chip controller using mixed signal FPGA, Smart Fusion device. To demonstrate its performance, we implemented a PID controller and PWM generator in the FPGA fabric. PWM generator and PID controller showed the effective regulation of a simple 1st order plant.

A piezoelectric paper feeder actuator using Micro Virtual Roller (MVR) is proposed, designed, fabricated and tested. This actuator can drive a sheet of paper forward or backward without any mechanical parts, such as the costly and heavy rollers used in traditional paper feeders. In this paper feeder actuator, two vibrating stators which produce traveling waves are used to drive the paper. The vibrations of the stators are similar to those of piezoelectric motors and follow a similar procedure to move the paper. A feasibility study simulated the actuator in COMSOL Multiphysics Software. Traveling wave and elliptical trajectories were obtained and the dimensions of the stator were optimized using FEM so that the paper could move at top speed. Next, the eigenfrequencies of the actuator was determined. Experimental testing was done in order to validate the FEM results that revealed the relationships between speed and parameters such as frequency and voltage. Advantages of this new mechanism are the sharp decrease in power consumption and low maintenance.

In this study, PZT (piezoelectric) actuators and PD control (PDs’ command line tool) method is selected to control the vibration of the flexible manipulator. The dynamic equations of the flexible manipulator system are established based on Lagrange principle. The control strategy of PZT actuators and joint control torque are designed. It is investigated by a Lyapunov approach that a combined scheme of PD feedback and command voltages applies to segmented PZT actuators. By comparison, only PD feedback control is also considered to control the flexible manipulator. The numerical simulations prove that the method of the designed PZT actuators’ control strategy and PD control is effective to compress the vibration of the flexible manipulator.

Nowadays, piezoelectric actuators (PA) are used in fast power actuations and high power applications as requested in machine tools or helicopters flap applications. Regarding to the low power capability and high loss ratios of linear amplifiers, Switching Power Amplifiers (SA75X) is designed by Cedrat Technologies to drive piezoelectric actuators in such applications. The switching technique (up to 100 kHz) allows high current peaks required by impulse or by high frequency applications on large piezoelectric actuators (or actuators in parallel) and allows energy harvesting. Output voltage, current, and actuator position are monitored via controller board and using sensor feedbacks. Furthermore, the developed system (SA75X+actuators) can operate in open or closed loop system with an output signal frequency up to 1 kHz. The OEM version of the powerful switching amplifier (SA75D:20Amax) has a dimensions of 100x100x100mm, i.e. 1 litter, and a weight of 850g.The power ratio of this amplifier is thus of 1.5kVA/L and 1.75kVA/Kg. The output power capability, signal noise ratios, and control robustness of the SA75X justifies the proposed solution Theoretical, simulation, and experimental tests of the SA75D (20Amax) will be presented to improve the amplifier performances

Piezoelectric (PZT) actuators are micro motion generators capable of producing a high displacement resolution and low strain with high force outputs. However, due to their relatively short motion ranges, the functions of PZT actuators become limited or infeasible for many of the above mentioned applications. One technique to overcome the mentioned shortcoming is to integrate a PZT actuator with a mechanical displacement amplifier. Such an amplification mechanism can be based on a compliant mechanical displacement amplifier (CMDA). A CMDA has many advantages such as no friction losses, no need for lubrication, no tolerance, and et al. over conventional rotating pinjoint mechanisms. Hence, the primary goal of a CMDA is to achieve a large output displacement in desired direction(s) for a given input displacement generated by a PZT actuator, and to keep a high positioning resolution at the same time. This thesis describes a complete study on the design, development and optimization of two proposed CMDA’s, one for the use in prostate Magnetic Resonance Elastography (MRE) application, and the other for the use as a planar motion generator mechanism for the application in high precision manipulation systems. The design of the both proposed mechanisms are based on the symmetric five-bar topology which facilitates a high amplification ratio (AR) with maintaining a relatively high natural frequency (NF). The first proposed CMDA was designed and optimized to amplify the generated motion of a PZT actuator in only one direction with keeping the NF as high as possible. On the other hand, the design and optimization of the second proposed CMDA was done to convert the linear motions of the integrated PZT actuators into a XY planar motion with high accuracy and resolution. In this study the comprehensive FEM analysis and simulations of both proposed CMDA designs are provided.

P(VDF-TrFE-CFE) (Poly (vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)), which exhibits a high electrostriction of about 7%, can transmit tactile output as vibration or displacement. In this study, we investigated the applicability of P(VDF-TrFE-CFE) to wearable piezoelectric actuators. The P(VDF-TrFE-CFE) layers were deposited through spin-coating, and interspaced with patterned Ag electrodes to fabricate a two-layer 3.5 mm × 3.5 mm device. This layered structure was designed and fabricated to increase the output and displacement of the actuator at low driving voltages. In addition, a laser vibrometer and piezoelectric force microscope were used to analyze the device’s vibration characteristics over the range of ~200~4,200 Hz. The on-off characteristics were confirmed at a frequency of 40 Hz.

This paper describes a stacked (multilayered) piezoelectric (PE) actuator in which both small and large displacements can be generated with a high degree of accuracy. This operation is achieved by driving the individual layers of the multilayered PE actuator. Such multilayered actuators are sandwich-structured, with a thin, (/spl sim/50 /spl mu/m) electrode layer between each pair of thin (/spl sim/100 /spl mu/m) PE-ceramic layers, so driving an individual layer of the stacked PE actuator was difficult. This difficulty was overcome by using polyamide deposition and a YAG-laser process so that each layer had an individual connection to the power supply. Each layer of the present multilayered PE actuator is thus driven by a corresponding pair of electrodes, and each pair of electrodes can be individually controlled.

Exact static solutions to piezoelectric smart beams including peel stresses: I: Theoretical formulation

To enhance the performance for high-speed tracking control of a piezoelectric tube actuator (PTA), an improved direct inverse rate-dependent PI model is obtained in this paper, and then adopted to design a practical feedforward controller achieving high-speed tracking control for a high-frequency trajectory with strong robustness. Specifically, based on the Prandtl-Ishlinskii (PI) model, an improved direct rate-dependent inverse model is set up for the PTA, with a polynomial function module introduced to eliminate the influence caused by the structure nonlinearity. Then, considering the features of the PTA structure, some preprocessing procedure is proposed to handle the collected experimental data, with the results utilized to identify all the unknown parameters over a wide bandwidth. Based on the obtained model, a practical feedforward controller, which presents the advantages of high-speed response, simple structure and convenient implementation, is then designed to enable the PTA to track high-frequency trajectories with satisfactory precision. Some experimental results are provided, which clearly demonstrate the high precision of the constructed/identified model, and the satisfactory performance of the proposed practical feedforward tracking control law.