Deflection Of Actuator Research Articles

Suboptimal Control Theory for Vehicle Attitude Control System Design

Base on the Lyapunov stability theory, an improved suboptimal control system scheme is advanced in this paper. Aiming at hypersonic reentry vehicle nonlinear properties of the actuator deflection angle rate and the deflection angle were studied. First, the mathematical model of the control system is established according to the flight control system control scheme. Considering the project realize easy, the flight control system is designed based on suboptimal control of Lyapunov stability theory. In order to close to the optimal control, then the suboptimal control design is improved. Finally the controller is applied to the instances, by analyzing the results confirmed the method is correctly.

Model Predictive Control for Gust Load Alleviation

For economical and ecological reasons aircraft are required to become more efficient by reducing fuel consumption and CO2 emissions. One way to achieve these objectives is to decrease the weight of the aircraft structure. The reduction is, however, limited by the structural requirement that the aircraft must be able to withstand the forces and stress induced by maneuvers, turbulence, and gusts. Reduction of the forces and stress, for example by suitable flight control schemes, allows lighter structures and thus more efficiency.In this paper we focus on the problem of alleviating gust loads at critical locations of the airframe. This is accomplished via a model predictive control approach that accounts for look ahead measurements of incoming gust disturbances via light detection and ranging (LIDAR) systems. Deflecting control surfaces are used by the predictive controller to reduce the load effects caused by the disturbance, the aircraft rigid body, and the structural response. The proposed controller design takes actuator deflection- and rate-limitations, the complex multiple-inputs multiple-outputs system structure, and the objective to reduce critical loads directly into account. Predictive control proved itself to be an effective control strategy for gust load alleviation.

Effect of the Casimir attraction on the torsion/bending coupled instability of electrostatic nano-actuators

In this paper, the effect of the Casimir attraction on the torsion/bending coupled pull-in instability of an electrostatic nano-actuator has been investigated for the first time. The governing equation of the actuator is derived and the instability parameters of the nano-actuator have been computed as a function of the geometrical characteristics and the bending/torsion stiffness ratio of the nano-actuator. The results reveal that the Casimir attraction could highly affect the coupled pull-in performance of the actuator. It is found that the Casimir force can reduce the instability voltage of nano-actuators. This deteriorating effect is more clearly highlighted in the torsional pull-in mode compared to the bending pull-in mode. Furthermore, it is found that the influence of the Casimir force on pull-in angle and deflection of the torsional actuator depends on the torsion/bending coupling ratio. For small-gap torsional actuators, the pull-in parameters have been strongly affected by the Casimir force, and neglecting Casimir attraction may lead to considerable error during simulations of the pull-in instability. The results of the present model are in better agreement with the experimental data compared to previous models.

Magnetization reversal observed by the deflection of magnetic actuator

A magnetic actuator consisting of a silicon oxide microcantilever and a silicon oxide plate deposited on ferromagnetic multilayer thin films is fabricated using electron beam lithography and electron beam evaporation, and placed in various magnetic fields to observe its flexure. The magnetic actuator is bent by magnetic torque produced by ferromagnetic multilayer thin films under an external magnetic field owing to the fabrication of a highly sensitive microcantilever and the design of elliptic ferromagnetic thin films with high magnetic shape anisotropy. The magnetic actuator is placed in four kinds of magnetic field directions to investigate the diversity of deflections; the angles between the easy axis of the ferromagnetic multilayer thin films and the direction of the external magnetic field are 90°, 70°, 45° and 20°.

Magnetization Reversal in Different Magnetic Thin Films Studied Using a Magnetic Actuator

We propose a novel method for observing the magnetization reversal of ferromagnetic thin film; the novel method is to observe the deflection of a magnetic actuator under various magnetic fields. However, they are necessary that the magnetic actuator is bent using a ferromagnetic thin film and that the deflection of the magnetic actuator is obvious enough to study the magnetization reversal of the ferromagnetic thin film. The magnetic actuator consisting of a 76×0.75×0.3 µm3 silicon oxide microcantilever and a 75×9×0.3 µm3 silicon oxide plate deposited on a ferromagnetic multilayer thin film is successfully fabricated using electron beam lithography and electron beam evaporation, and placed in various magnetic fields to observe its flexure. In this study, three shapes of magnetic element are designed: 60×1×0.09 µm3, 60×3×0.09 µm3, and 60×6×0.09 µm3. In the sweep-down process, the magnetization of the 60×6×0.09 µm3 ferromagnetic thin film is reversed at -147 G; the magnetization of the 60×3×0.09 µm3 ferromagnetic thin film is reversed at -313 G; and the magnetization of the 60×6×0.09 µm3 ferromagnetic thin film is reversed at -643 G. The study is useful for applications of the magnetic actuator.

Magnetization Reversal in Different Magnetic Thin Films Studied Using a Magnetic Actuator

We propose a novel method for observing the magnetization reversal of ferromagnetic thin film; the novel method is to observe the deflection of a magnetic actuator under various magnetic fields. However, they are necessary that the magnetic actuator is bent using a ferromagnetic thin film and that the deflection of the magnetic actuator is obvious enough to study the magnetization reversal of the ferromagnetic thin film. The magnetic actuator consisting of a 76×0.75×0.3 µm3 silicon oxide microcantilever and a 75×9×0.3 µm3 silicon oxide plate deposited on a ferromagnetic multilayer thin film is successfully fabricated using electron beam lithography and electron beam evaporation, and placed in various magnetic fields to observe its flexure. In this study, three shapes of magnetic element are designed: 60×1×0.09 µm3, 60×3×0.09 µm3, and 60×6×0.09 µm3. In the sweep-down process, the magnetization of the 60×6×0.09 µm3 ferromagnetic thin film is reversed at -147 G; the magnetization of the 60×3×0.09 µm3 ferromagnetic thin film is reversed at -313 G; and the magnetization of the 60×6×0.09 µm3 ferromagnetic thin film is reversed at -643 G. The study is useful for applications of the magnetic actuator.

Deflections of Magnetic Actuators with Different Widths of Microcantilevers

Two magnetic actuators with different widths of microcantilevers are fabricated using electron beam lithography and electron beam evaporation and placed in various magnetic fields to observe the discrepancy between their flexures. One magnetic actuator of a 76×0.75×0.3 µm3 silicon oxide microcantilever and a 75×9×0.3 µm3 silicon oxide plate deposited on a 60×1×0.09 µm3 ferromagnetic thin film; the other of a 76×0.85×0.3 µm3 silicon oxide microcantilever and a 75×9×0.3 µm3 silicon oxide plate deposited on a 60×1×0.09 µm3 ferromagnetic thin film. The magnetic actuator is bent by magnetic torque produced by the ferromagnetic thin film under an external magnetic field owing to the fabrication of a highly sensitive microcantilever and the design of a high magnetic shape anisotropy. In this study, we prove the effect of the width of the microcantilever by the deflection of the magnetic actuator. The deflection of the magnetic actuator can be forecasted, when the magnetic actuator is used for gripping a cell.

Topology optimization of planar shape memory alloy thermal actuators using element connectivity parameterization

AbstractThis paper presents the direct application of topology optimization to the design of shape memory alloy (SMA) thermal actuators. Because SMAs exhibit strongly nonlinear, temperature‐dependent material behavior, designing effective multidimensional SMA actuator structures is a challenging task. We pursue the use of topology optimization to address this problem. Conventional material scaling topology optimization approaches are hampered by the complexity of the SMA constitutive behavior combined with large actuator deflections. Therefore, for topology optimization we employ the element connectivity parameterization approach, which offers improved analysis convergence and robustness, as well as an unambiguous treatment of nonlinear materials. A path‐independent SMA constitutive model, aimed particularly at the NiTi R‐phase transformation, is employed, allowing efficient adjoint sensitivity analysis. The effectiveness of the proposed SMA topology optimization is demonstrated by numerical examples of constrained and unconstrained formulations of actuator stroke maximization, which provide insight into the characteristics of optimal SMA actuators. Copyright © 2011 John Wiley & Sons, Ltd.

Load Balancing in Control Allocation

Next-generation aircraft with a large number of actuators will require advanced control allocation methods to compute the actuator commands needed to follow desired trajectories while respecting system constraints. Previously, algorithms were proposed to minimize the l 1 or l 2 norms of the tracking error and of the actuator deflections. This paper discusses the alternative choice of the l ∞ norm, or the sup norm. Minimization of the control effort translates into the minimization of the maximum actuator deflection (min―max optimization). This paper shows how the problem can be solved effectively by converting it into a linear program and solving it using a simplex algorithm. Properties of the algorithm are also investigated through examples. In particular, the min―max criterion results in a type of load balancing, where the load is the desired command and the algorithm balances this load among various actuators. The solution using the l ∞ norm also results in better robustness to failures and lower sensitivity to nonlinearities in illustrative examples. This paper also discusses the extension of the results to a normalized l ∞ norm, where the norm of the actuator deflections are scaled by the actuator limits. Minimization of the control effort then translates into the minimization of the maximum actuator deflection as a percentage of its range of motion.

Comparative analysis of the planar capacitor and IDT piezoelectric thin-film micro-actuator models

A comparison of the analysis of similarly developed microactuators is presented. Accurate modeling and simulation techniques are vital for piezoelectrically actuated microactuators. Coupling analytical and numerical modeling techniques with variational design parameters, accurate performance predictions can be realized. Axi-symmetric two-dimensional and three-dimensional static deflection and harmonic models of a planar capacitor actuator are presented. Planar capacitor samples were modeled as unimorph diaphragms with sandwiched piezoelectric material. The harmonic frequencies were calculated numerically and compared well to predicted values and deformations. The finite element modeling reflects the impact of the d31 piezoelectric constant. Two-dimensional axi-symmetric models of circularly interdigitated piezoelectrically membranes are also presented. The models include the piezoelectric material and properties, the membrane materials and properties, and incorporates various design considerations of the model. These models also include the electro-mechanical coupling for piezoelectric actuation and highlight a novel approach to take advantage of the higher d33 piezoelectric coupling coefficient. Performance is evaluated for varying parameters such as electrode pitch, electrode width, and piezoelectric material thickness. The models also showed that several of the design parameters were naturally coupled. The static numerical models correlate well with the maximum static deflection of the experimental devices. Finally, this paper deals with the development of numerical harmonic models of piezoelectrically actuated planar capacitor and interdigitated diaphragms. The models were able to closely predict the first two harmonics, conservatively predict the third through sixth harmonics and predict the estimated values of center deflection using plate theory. Harmonic frequency and deflection simulations need further correlation by conducting extensive iterative harmonic simulations and experiments. The results, conclusions and potential improvements are discussed.

Flight Control Design for a Tailless Aircraft Using Eigenstructure Assignment

We apply eigenstructure assignment to the design of a flight control system for a wind tunnel model of a tailless aircraft. The aircraft, known as the innovative control effectors (ICEs) aircraft, has unconventional control surfaces plus pitch and yaw thrust vectoring. We linearize the aircraft in straight and level flight at an altitude of 15,000 feet and Mach number 0.4. Then, we separately design flight control systems for the longitudinal and lateral dynamics. We use a control allocation scheme with weights so that the lateral pseudoinputs are yaw and roll moment, and the longitudinal pseudoinput is pitching moment. In contrast to previous eigenstructure assignment designs for the ICE aircraft, we consider the phugoid mode, thrust vectoring, and stability margins. We show how to simultaneously stabilize the phugoid mode, satisfy MIL-F-8785C mode specifications, and satisfy MIL-F-9490D phase and gain margin specifications. We also use a cstar command system that is preferable to earlier pitch-rate command systems. Finally, we present simulation results of the combined longitudinal/lateral flight control system using a full 6DOF nonlinear simulation with approximately 20,000 values for the aerodynamic coefficients. Our simulation includes limiters on actuator deflections, deflection rates, and control system integrators.

Thermal Analysis and Simulation of MEMS Thermal Actuator for Food Industry

Micro-actuator technology is important base of design and fabrication MEMS. According to a kind of bimorph thermal actuator, this paper obtains the thermal deflection and temperature distribution of MEMS thermal actuator by using finite element analysis. The relationship between the thermal deflection and some parameter such as length of flexure are analyzed in detail. Through simulation comparison, the influences of the length of flexure on thermal deflection and fatigue life are verified, which provides a good guide for the design of MEMS thermal actuator further.

Micromachined scanning proximal probes with integrated piezoresistive readout and bimetal actuator for high eigenmode operation

The fabrication process, application, and properties of a novel piezoresistive multiprobe with an integrated thermal tip deflection actuator are described in this article. The optimized fabrication process of the microprobe enables high-frequency sensor operation and integration of a high sharp conical tip, which was additionally covered with titanium using atomic layer deposition to improve mechanical endurance and ensure electrical conductivity. This microprobe was applied in high-resolution self-assembled monolayer surface investigations in which the piezoresistive cantilever with the integrated thermal deflection actuator was excited at two of its flexural-resonant eigenmodes. The excited second eigenmode and phase show different contrasts com-pared with images recorded at the first eigenmode.

Mechanical characteristics of a thermo-responsive two-way shape change polymeric laminate

A thermo-responsive bimorph actuator consisting of all-polymeric components, primarily a polyvinylchloride (PVC) plate and a carbon fiber-reinforced plastic plate (CFRP), was fabricated. The strain change of the CFRP plate resulting from environmental temperature change was quite small, while that of the PVC plate was quite large. Such a large strain disparity caused the deflection of bimorph actuator. The bimorph actuator exhibited reversible deflection in accordance with the environmental temperature without hysteresis. The reversible deflection was induced even under a load. Deflection of the bimorph actuator in response to the environmental temperature was theoretically calculated and was in good agreement with the experimental result. Further theoretical analysis predicted a fairly large deflection of the bimorph actuator even under a relatively heavy load.

QUANTIFYING THE PERFORMANCE OF MULTIPLE-OUTPUT PIEZOELECTRIC OPTICAL SWITCHES

Optical switch prototypes are developed based on the new concept that the input fiber is directly moved by the deflection of a piezoelectric tube actuator. The piezoelectric tube actuators used in the switch prototypes are manufactured by an electrophoretic deposition process. The tubes are low cost and compact in size with an inner diameter of less than 1mm. They have a deflection of 65 µm which is adequate to actuate the input fiber for switching. A number of multimode 1×2 fiber optical switch prototypes have previously been built. To develop the new 1×4 optical switch, a new output fiber alignment device was fabricated. The conductive coating on the piezoelectric tube actuator was sectored into four. Also, the power supply unit was redesigned in order to provide high voltage for the four-sectored tube. The success in the 1×4 prototype development proves that the new multiple-output piezoelectric switching concept is feasible. The concept demonstrates an advantage over some other opto-mechanical switches which need to be cascaded to achieve a multiple-output configuration.

High-rate sputtering of thick PZT thin films for MEMS

Crack and void free polycrystalline Lead Zirconate Titanate (PZT) thin films in the range of 5 µm to 10 µm have been successfully deposited on silicon substrates using a novel high rate sputtering process. The sputtered PZT layers show a high dielectric constant er between 1,000 and 1,800 with a moderate dissipation factor tan (δ) = 0,002 − 0,01 measured at f = 1 kHz, a distinct ferroelectric hysteresis loop with a remanent polarisation of 17 µC/cm2 and coercive field strength of 5.4 kV/mm. The piezoelectric coefficients d33,f = 80 pm/V are measured by using a Double Beam Laser Interferometer (DBLI). Based on this deposition process a membrane actuator mainly consisting of a SOI layer and a sputtered PZT thin film was prepared. The deflection of this membrane actuator depending on the driving voltage was measured with a white light interferometer and compared to the results of finite element analysis (FEA). With this approach a transverse piezoelectric coefficient of about e31 = −11.2 C/m2 was calculated, whereas all the other material parameters in the model were lent from PZT-5A.

Cantilever deflection measurement and actuation by an interdigitated transducer

A scheme that allows all-electrical high-bandwidth readout of a cantilever deflection by means of an integrated interdigitated transducer is presented. The present approach takes advantage of the piezoelectricity of the chosen cantilever substrate material to generate and detect surface-acoustic-waves by means of an interdigitated transducer (IDT) and to determine cantilever deflections. We shall also show that the same IDT can be used to excite the oscillation modes of the lever. Our scheme is compatible with implementations exploiting wireless excitation and readout and in mass sensing applications.

Determining maximum load-carrying capacity of robots using adaptive robust neural controller

SUMMARYIn this paper, the combination of neural network (NN), proportional derivative (PD), and robust controller are used for determining the maximum load-carrying capacity (MLCC) of articulated robots, subject to both actuator and end-effector deflection constraints. The proposed technique is then applied to articulated robots, and MLCC is obtained for a given trajectory. In the practical simulations, it's impossible to determine the parameters of robot model exactly, so the trajectory tracking performance of the proportional integral derivative (PID) and computed torque methods significantly decrease. The PD control of robot has major problem, it cannot guarantee zero steady state error. For this reason, the NN controller with PD and robust controller are used. The multilayer neural network is also used to compensate gravity and friction effects. By using Lyapunov Direct Method it is shown that the stability of closed loop system would be guaranteed, if the weights of multilayer had certain learning rules. Standard back propagation algorithm is used as a learning algorithm to update the connection weights of the NN controller. The simulation results of the proposed adaptive robust neural network (ARNN) controller are compred with sliding mode and feedback linearization methods for flexible joint robot, and compared with open loop controller for 3D industrial robot. The obtained results assured the robustness and improvement in MLCC in the presence of uncertainties in dynamic model of the robot arm and external disturbances. In fact, adaptive robust NN controller suppresses disturbances accurately and achieves very small errors between commanded and actual trajectories.

CHARACTERISTICS OF SMART PIEZOELECTRIC ACTUATORS FOR PRECISE MOTION APPLICATIONS

In this paper, the static and dynamic characteristics of piezoelectric actuators (micromanipulator) are investigated theoretically and experimentally. A physical measurement setup is established for bimorph bending actuators. The actuator deflection is calculated for different driving voltages and compared with the measured values. Transient response due to a step input was very fast, the bandwidth obtained was 101Hz.The Transient, and frequency responses are obtained under different operating conditions.

Force Characterization and Rigidity Analysis of a Monolithic Cochlear Prosthesis Actuator

Cochlear implants continue to be used in the treatment of profound deafness. Because of the tonotopic nature of the cochlea, more controlled insertion is perhaps the most important factor affecting device performance. The implant stiffness, and therefore the scala tympani (ST) wall contact force, contributes to insertion difficulties. Attempts to correlate the implant carrier structural properties and the intracochlear contact forces during insertion are limited. Researchers in the Michigan Center for Wireless Integrated Microsystems are developing perimodiolar-shaped silicon and parylene-based thin film cochlear electrode arrays and backing devices for a more controllable implantation. We report a method developed for measuring the thin film actuated electrode array rigidity to quantify the ST and modiolus wall contact forces during and after insertion. The method used a pneumatically actuated polyethylene terephthalate (PET) monolithic electrode actuator using pressurized air (0–200 kPa) for actuation. The prototype actuators consisted of PET tubes with an ID of 365 μm and a wall thickness of 58 μm. Force calculations using cantilever beam bending theory were performed to estimate the tube bending forces as a function of internal pressure and therefore variable structural stiffness. Based on estimations, a method was developed to measure such small forces avoiding the use of commercially available, relatively insensitive load cells. A fixture was fabricated incorporating two brass microcantilevers (reference and deflection arms) sensitive to sub-mN forces applied by the actuator on the deflection arm of the cantilevers. Microcantilver deflection data, captured by an interferometric microscope, was used to calculate the actuator force and eventually the reaction force acting on the actuator. The implant actuation forces ranged from 0–0.76 mN over an actuation pressure range of 0–140 kPa, from nearly straight to the relaxed perimodiolar post-implantation shape. For estimating the implant rigidity (EI), the actuator stiffness and the actuation pressure was correlated. The actuator stiffness at different actuation pressures was obtained both theoretically (using beam bending theory and PET tube structural properties) and experimentally (using the derived unconstrained actuator deflections at measured actuator forces). The theoretical and experimental stiffness values ranged from 3.6E-08 to 5.34E-07 N/μm and 2.5E-08 to 7.8E-06 N/μm respectively over the working pressure range. The calculated rigidity constant (EI) of the best prototype insertion tool from the experimental stiffness measurement was 6.71E06 Nμm2. The insertion tool-ST wall contact forces were calculated, using the estimated rigidity, in a hypothetical insertion situation. Force calculations assumed that the implant is equipped with actuator deflection feedback sensors and the actuator's stiffness remains constant over its entire length for a given operating pressure. A contact force of 1.19 mN was found acting on the cochlear ST wall when the insertion tool hits the wall and deflects by 200 μm at an actuation pressure of 140 kPa.