Modal analysis of a unimorph piezoelectrical transducer

Piezoelectric transducers are widely applied to MEMS devices as actuators or sensors due to their simple structure and easy control. A micromachined piezoelectric microjet is introduced and modal analysis of its piezoelectric actuator has been thoroughly presented. Both numerical analysis and experimental measurement are implemented in this study. In numerical analysis, an approximate method is established to evaluate the first vibration mode and finite-element methods are used to simulate higher order vibration modes of the transducer. An experimental system was also set up to measure the axisymmetric vibration modes of the transducer. Compared with experimental results, good correlation was found between the numerical and experimental results, which proved the validation and reliability of the models. Through these models, further optimal design of the transducer can be carried out.Financial support by National Natural Science Funds (29833070) and National 973 Basic Research Projects (G1999033106) of China is deeply appreciated.     

Computation of magnetic field in an actuator

Design and optimization of an actuators based on magnetostrictive technology requires computation of the magnetic field. The “MS”-technology offers an attractive controllability with high power density. The magnetostriction is a reversible feature which can be used in various actuator layouts. The actuator performance depends on driving magnetic field and the particular magnetic properties of used materials. Good understanding of specific design constrains is required to define and to optimized a magnetostrictive actuator. The non-linear computation of the magnetic field using FEM software is vital for the finale experimental design of a low-frequency actuator. This paper presents results of magnetic field simulation with FEMM software package and experimental measurements of the magnetic flux density. Good correlation between the simulation results and experimental measurements has been achieved.     

Analysis and modeling of hysteresis of piezoelectric micro-actuator used in high precision dual-stage servo system

A dual-stage servo system consists of a primary coarse actuator for facilitating large motion and a secondary micro-actuator for small but precise motion to improve tracking performance. Piezoelectric micro-actuator made from lead zirconate titanate(PZT)has been a popular choice for the secondary stage. However, the advantage gained by the resolution of the secondary PZT actuator is reduced by its inherent hysteresis nonlinearity. Model based hysteresis compensation techniques are preferred due to their simplicity and fast response. Identification and modeling are two substantial parts in such model-based techniques. This paper presents a rigorous analysis and modeling of the hysteresis of PZT micro-actuator. Modified Generalized Prandtl-Ishlinskii and Coleman-Hodgdon models are studied. Identification of the model through nonlinear least square and particle swarm optimization are examined and compared. Several analyses are done through tuning of the model parameters and identification techniques.Experimental analysis and simulation results underscore the effectiveness of this modeling approach. Finally as a design example,a dual-stage simulation analysis is done to show the effectiveness of systematic modeling on hysteresis compensation.     

Intelligent control of DC motor driven electromechanical fin actuator

In this paper modeling, simulation and control of an electromechanical actuator (EMA) system for aerofin control (AFC) with permanent magnet brush DC motor driven by a constant current driver are investigated. Nonlinear model of the EMA-AFC system has been developed and experimentally verified in actuator test bench. Model has been used as the starting point for PID position controller synthesis. To improve performances of the system, computational intelligence has been applied. Genetic PID optimization, genetic algorithm (GA) optimized fuzzy supervisory PID control and finally GA optimized nonlinear PID algorithm modification are proposed. Improved transient response and system behavior have also been experimentally validated.     

A high displacement ultrasonic actuator based on a flexural mechanical amplifier

Commonly used high displacement ultrasonic actuators are composed of a Langevin transducer and of a sectional ultrasonic concentrator working as a displacement amplifier. In this work, a novel ultrasonic actuator, which exploits a displacement amplifier vibrating in a flexural mode, is proposed. Design and analysis of the actuator have been performed by using a FEM software. Performances of the proposed actuator have been evaluated by using a classical ultrasonic actuator, based on a stepped horn concentrator, as a benchmark. Simulated results have shown that the flexural amplifier exhibits a displacement amplification about 50% higher than that of the stepped horn; furthermore, due to its capability to absorb a higher electrical power, the whole actuator has shown a maximum displacement that is twice the maximum displacement of the stepped horn actuator. Simulated results have been validated by measurements carried out on two manufactured prototypes.     

Design of a dual stage actuator tape head with high-bandwidth track following capability

As tape recording density increases, high-frequency track following capability of the tape head actuator becomes more important. This paper details the mechanical design and experimental analysis of a dual state actuator tape head. The dual stage actuator design combines a traditional voice coil motor for low frequency track following with a piezoelectric actuator for high-frequency track following. Non-parametric and parametric modeling techniques are used in the analysis of the dual stage actuator. The performance of the dual stage actuator head shows good correlation with the model and will enable improved track following capability for future high-performance tape drives.     

Modified BVD model of PZT actuator using high-voltage square pulse method for micropumps

The field of micro–electro–mechanical systems and microfabrication has produced micro-total-analysis systems, which are widely used in medicine, diagnostics, and biological and chemical research. For the development of high precision drug delivery systems, micropumps with a lead zirconate titanate (PZT) actuator, which has a fast response time and high resolution, are most likely to be applied in implementations. To improve the performance of PZT micropumps utilized in the microfluidics field, suitable models are required to enable the optimization of the PZT actuator driving circuits. This study proposes a modified Butterworth–Van Dyke (BVD) model which consists of a BVD model in series with an electrical resistance that describes a PZT actuator driven by a square pulse with a relatively high voltage and low frequency for micropump applications. Experiments were conducted to assess parameters of the model at various voltages; they indicate that the electrical resistance is essential for modeling the PZT actuator of the micropump. The electrical model was verified using a SPICE simulation, whose numerical results were compared with the experimental data for the current response of the PZT actuator. The results show a close correlation between the simulation of the electrical model and the measurements of the PZT actuator under real operating conditions.     

Robust stability analysis and fuzzy-scheduling control for nonlinear systems subject to actuator saturation

Takagi-Sugeno (TS) fuzzy models can provide an effective representation of complex nonlinear systems in terms of fuzzy sets and fuzzy reasoning applied to a set of linear input-output submodels. In this paper, the TS fuzzy modeling approach is utilized to carry out the stability analysis and control design for nonlinear systems with actuator saturation. The TS fuzzy representation of a nonlinear system subject to actuator saturation is presented. In our TS fuzzy representation, the modeling error is also captured by norm-bounded uncertainties. A set invariance condition for the system in the TS fuzzy representation is first established. Based on this set invariance condition, the problem of estimating the domain of attraction of a TS fuzzy system under a constant state feedback law is formulated and solved as a linear matrix inequality (LMI) optimization problem. By viewing the state feedback gain as an extra free parameter in the LMI optimization problem, we arrive at a method for designing state feedback gain that maximizes the domain of attraction. A fuzzy scheduling control design method is also introduced to further enlarge the domain of attraction. An inverted pendulum is used to show the effectiveness of the proposed fuzzy controller.     

Design,kinematic modeling and sliding mode control with sliding mode observer of a novel 3-PRR compliant mechanism

Compliant mechanisms have great advantages to be used as micropositioning stages for high-precision applications but they are very sensitive to manufacturing tolerances and assembling errors. In this work, a novel compliant stage having 3-PRR kinematic structure and actuated by piezoelectric actuators is introduced. A kinematic modeling based on compliance of the flexible elements and finite element analysis based model have been extracted. It is found out that the experimental results are not compatible with the theoretical results due to the manufacturing, actuator assembly errors. The position control of the mechanism has been achieved using sliding mode control which is a great method for unpredictable varying parameters in the system. Sliding mode observer has also been used for the hysteresis and nonlinearities of the piezoelectric actuators. Experimental models for each actuation axis have been used as the nominal models for the sliding mode observer. In order to see the advantage of the control method simple PID control has also been implemented. It is seen that sliding mode control with sliding mode observer using experimental models reduces the position tracking errors to the range of the accuracy of our available measurement.     

压电扭转驱动器的有限元分析

为研究压电陶瓷的扭转驱动能力,制作了压电扭转驱动器,应用有限元分析方法,使用三维六面体耦合单元对压电扭转驱动器进行了力学和电学分析。根据压电陶瓷的基本方程,利用有限元分析软件ANSYS进行直接耦合分析求解。分析结果与试验结果取得了良好的一致,证实了利用压电陶瓷双晶片弯曲制作压电扭转驱动器结构设计的可行性。该分析方法与结论对压电驱动器的设计、制造与优化具有一定的指导意义。     

Adaptive neuro-fuzzy modeling of a soft finger-like actuator for cyber-physical industrial systems

Soft robotics is a trending area of research that can revolutionize the use of robotics in industry 4.0 and cyber-physical systems including intelligent industrial systems and their interactions with the human. These robots have notable adaptability to objects and can facilitate many tasks in everyday life. One potential use of these robots is in medical applications. Due to the soft body of these robots, they are a suitable replacement for applications like rehabilitation and exoskeletons. In this paper, we present the neuro-fuzzy modeling of a soft pneumatic finger-like actuator. This actuator is a fiber-reinforced soft robot with the shape and dimensions of a real finger and moves in planar motion. A bending sensor is used as a feedback for curvature motion of this actuator. In order to model this actuator, an adaptive neuro-fuzzy inference system is utilized to overcome the hardship in the modeling of the nonlinear performance of the soft materials. An experimental setup is designed to obtain suitable input–output data needed for modeling. The results show the applicability of the utilized method in the modeling of the soft actuator.

     

Polymeric Thermal Microactuator With Embedded Silicon Skeleton: Part I—Design and Analysis

This paper presents the modeling of a new design of a polymeric thermal microactuator with an embedded meander-shaped silicon skeleton. The design has a skeleton embedded in a polymer block. The embedded skeleton improves heat transfer to the polymer and reinforces it. In addition, the skeleton laterally constrains the polymer to direct the volumetric thermal expansion of the polymer in the actuation direction. The complex geometry and multiple-material composition of the actuator make its modeling very involved. In this paper, the main focus is on the development of approximate electrothermal and thermoelastic models to capture the essence of the actuator behavior. The approximate models are validated with a fully coupled multiphysics finite element model and with experimental testing. The approximate models can be useful as an inexpensive tool for subsequent design optimization. Evaluation, using the analytical and numerical models, shows that the polymer actuator with the embedded skeleton outperforms its counterpart without a skeleton, which is in terms of heat transfer and, thus, response time, actuation stress, and planarity.$hfill$ [2007-0193]      

电热驱动Bimorph微执行器对流系数估算方法研究

随着电热驱动MEMS器件尺寸进一步缩小,传统热对流系数的取值已无法满足微系统分析建模需求。针对电热型Bimorph结构的MEMS微镜驱动器,通过分析其温度分布,并以其平均温度为参考指标建立简单热阻和对流热阻分段模型,推算出微尺度下精确的对流系数,提高了微执行器设计模型的驱动性能。经理论计算和实验测试验证,对流系数值的误差在8.1%以内,满足实际设计需求,验证了该方法的合理性和可行性。     

Electrothermal properties and modeling of polysilicon microthermal actuators

This work addresses a range of issues on modeling electrothermal microactuators, including the physics of temperature dependent material properties and Finite Element Analysis (FEA) modeling techniques. Electrical and thermal conductivity are a nonlinear function of temperature that can be explained with electron and phonon transport models, respectively. Parametric forms of these equations are developed for polysilicon and a technique to extract these parameters from experimental data is given. A modeling technique to capture the convective and conductive cooling effects on a thermal actuator in air is then presented. Using this modeling technique and the established polysilicon material properties, simulation results are compared with measured actuator responses. Both static and transient analyzes have been performed on two styles of actuators and the results compare well with measured data.     

Simultaneous optimization of photostrictive actuator locations,numbers and light intensities for structural shape control using hierarchical genetic algorithm

The present paper introduces an investigation into simultaneous optimization of the PbLaZrTi-based actuator configuration and corresponding applied light intensity for morphing beam structural shapes. A finite element formulation for multiphysics analysis of coupled opto-electro-thermo-mechanical fields in PbLaZrTi ceramics is derived and verified with the theoretical solution and the commercial software ANSYS. This element is then used to simulate beam bending shape control using the orthotropic PbLaZrTi actuators and the simultaneous optimization. In this procedure, the controlling and geometrical variables are simultaneously optimized via a hierarchical genetic algorithm. A bi-coded chromosome is proposed in a hierarchical mode, which consists of some control genes (i.e. actuator location and number) and parametric genes (i.e. applied light intensity). Whether the parametric gene is activated or not is managed by the value of the first-grade control genes. The numerical results demonstrate that the achieved beam bending shapes correlate remarkably well with the expected ones and the simultaneous optimization of photostrictive actuator locations, numbers and light intensities can result in optimal actuator layout with less PbLaZrTi actuators and irradiated light energy. The simulation results also show that the hierarchical genetic algorithm has more superior performance over the conventional real-coded genetic algorithm.     

Hierarchical genetic-particle swarm optimization for bistable permanent magnet actuators

Bistable permanent magnet actuator (BPMA) has been widely used in industry as a kind of energy converter. However, its power consumption and response performance are in conflict during operating because of the conflict between holding force and initial force (the minimum threshold driving force). An optimization procedure based on a novel hierarchical genetic-particle swarm algorithm (HGP) for a hybrid excited linear actuator (HELA) constrained in a specific volume has been developed. For obtaining the objective function for each parameter combination precisely, three-dimensional finite element analysis (FEA) was employed. Meanwhile, the improvement of optimization efficiency and quality is extremely demanding because the FEA needs much computing time. The proposed hybrid algorithm adopts a hierarchical structure from the concept of “experimental classes” in China. The base level is composed of the majority general individuals of Genetic algorithms (GA), which provides the global search ability of the entire algorithm. The top level comprises the minority elite consisting of the better individual, which performs the accurate local search by using the particle swarm optimization (PSO) algorithm with variable inertia weight and constriction coefficient. Additionally, the performance of HGP has been evaluated through the Rosenbrock function, and the proposed method is superior to other related methods Finally, the proposed procedure was verified by optimizing HELA's parameters in multidimensional parameters space under the design constraint. The results show that both of the holding force and the initial force are improved more than 25% compared with the initial design, which ensures both low power consumption and fast response.     

Modeling and experimental validation of a piezoelectric micropump with novel no-moving-part valves

No-moving-part (NMP) valves are microconduits able to partially rectify an oscillating fluid moving through them. The modeling of such valves is not at all trivial. Even greater difficulties arise when the behavior of the whole micropump equipped with those NMP valves is investigated, because of the complex fluid-dynamic phenomena interacting with deformable structures. This paper proposes a generalization of the efficiency modeling, nowadays used for single valves, to whole micropump equipped with them. Such modeling has been applied to design a novel, high efficiency NMP valve to be used in a piezoelectric micropump. The main feature of the new valve is the presence of some properly shaped vortex area along its fluid-dynamic pattern, allowing to improve micropump performance. For comparison purposes, the same modeling has been applied to a standard nozzle-diffuser NMP valve to be used with the same piezoelectric actuator. The experimental comparison of micropump performance (maximum flow rate and pressure head) shows that the proposed modeling technique is able to discriminate between better and worse performer. The effects of unsteady dynamic effects have been evaluated a posteriori, confirming their important weight on the actual performance of the micropumps equipped with NMP valves.     

A model for transient ultrasonic field in solid generated by a transducer in immersion

A model has been developed which can be used to calculate the particle velocity waveforms at arbitrary positions in a solid immersed in a fluid when irradiated by a transmitting transducer, launching a short pulse of a longitudinal wave into the fluid. Mode-converted longitudinal and shear waves are generated at the interface between the solid and the fluid. Calculations performed agree well with the results of experimental measurements using a specially constructed miniature piezoelectric receiving probe. The model constructed has been used to explain the radiation of a transmitting transducer into an immersed solid and it can be used for the optimal design of a transducer and ultrasonic NDT device in immersion mode, that has been widely used for ultrasonic imaging and automatic inspection.     

An analysis,design and tuning of Cascade Control Systems in the presence of constraints in actuator and process outputs

In the presence of rate constraints in actuator, design of cascade controller based on the primary controller conditional integration can result into closed-loop system oscillations. Stability analysis, performed by the describing function technique and confirmed by simulation, demonstrates that the solution based on the Anti-Reset Windup Cascade Control System (ARW CCS) structure is successful. Design and tuning of the ARW CCS secondary controller is a standard ARW single-input single-output problem. In the present paper tuning is proposed for the ARW CCS primary controller. For the serial process modeling simple rules are derived and confirmed by experimental results, obtained on a drum type boiler of a 210 MWe lignite coal fired unit. General design of the ARW CCS is based on the parallel process modeling and optimization of the primary controller. Optimization is performed in the frequency domain, under constraints on the maximum sensitivity, multiplicative uncertainty bound and sensitivity to measurement noise. Simulation and experimental results on a laboratory thermal plant demonstrate effectiveness of the proposed optimization.     

Design of a magnetostrictive (MS) actuator

Several advanced technologies are introduced in automotive applications. Higher energy density and dynamic performance are demanding new and cost-effective actuator structures. Magnetostriction (MS), change in shape of materials under the influence of an external magnetic field, is one of the advanced technologies. Good understanding of specific design constrains is required to define and optimize a magnetostrictive actuator. This paper presents parametrical analysis with magnetic simulation of a magnetostrictive actuator. Proposed actuator has been designed, and the performance has been evaluated on experimental rig. Strain, elongation of the shaft, of 1000 ppm at 10 A and a blocked force over 4500 N has been achieved with shaft of 8 mm diameter, made of Terfenol-D. Furthermore, the effect of pre-stress of the Terfenol-D shaft has been evaluated experimentally. The study shows that excellent features can be obtained by magnetostrictive materials for many advanced applications.