PKM mechatronic clamping adaptive device

This study proposes a novel adaptive fixturing device based on active clamping systems for smart micropositioning of thin-walled precision parts. The modular architecture and the structure flexibility make the system suitable for various industrial applications. The proposed device is realized as a Parallel Kinematic Machine (PKM), opportunely sensorized and controlled, able to perform automatic error-free workpiece clamping procedures, drastically reducing the overall fixturing set-up time. The paper describes the kinematics and dynamics of this mechatronic system. A first campaign of experimental trails has been carried out on the prototype, obtaining promising results

DEVELOPMENT OF A NOVEL Z-AXIS PRECISION POSITIONING STAGE WITH MILLIMETER TRAVEL RANGE BASED ON A LINEAR PIEZOELECTRIC MOTOR

Piezoelectric-based positioners are incorporated into stereotaxic devices for microsurgery, scanning tunneling microscopes for the manipulation of atomic and molecular-scale structures, nanomanipulator systems for cell microinjection and machine tools for semiconductor-based manufacturing. Although several precision positioning systems have been developed for planar motion, most are not suitable to provide long travel range with large load capacity in vertical axis because of their weights, size, design and embedded actuators. This thesis develops a novel positioner which is being developed specifically for vertical axis motion based on a piezoworm arrangement in flexure frames. An improved estimation of the stiffness for Normally Clamped (NC) clamp is presented. Analytical calculations and finite element analysis are used to optimize the design of the lifting platform as well as the piezoworm actuator to provide maximum thrust force while maintaining a compact size. To make a stage frame more compact, the actuator is integrated into the stage body. The complementary clamps and the amplified piezoelectric actuators based extenders are designed such that no power is needed to maintain a fixed vertical position, holding the payload against the force of gravity. The design is extended to a piezoworm stage prototype and validated through several tests. Experiments on the prototype stage show that it is capable of a speed of 5.4 mm/s, a force capacity of 8 N and can travel over 16 mm

Engineering Electromagnetic Systems for Next-Generation Brain-Machine Interface

MagnetoElectric Nanoparticles (MENPs) are known to be a powerful tool for a broad range of applications spanning from medicine to energy-efficient electronics. MENPs allow to couple intrinsic electric fields in the nervous system with externally controlled magnetic fields. This thesis exploited MENPs to achieve contactless brain-machine interface (BMIs). Special electromagnetic devices were engineered for controlling the MENPs’ magnetoelectric effect to enable stimulation and recording. The most important engineering breakthroughs of the study are summarized below. (I) Metastable Physics to Localize Nanoparticles: One of the main challenges is to localize the nanoparticles at any selected site(s) in the brain. The fundamental problem is due to the fact that according to the Maxwell’s equations, magnetic fields could not be used to localize ferromagnetic nanoparticles under stable equilibrium conditions. Metastable physics was used to overcome this challenge theoretically and preliminary results show the potential of single neuron localization in neural cell culture. 3D electromagnetic sources generated a time varying magnetic field pattern which effectively kept the nanoparticles in a metastable diamagnetic state. (II) Electromagnetic Systems to Locally Stimulate Neurons: Assuming a magnetoelectric coefficient of 1 V/cm/Oe, application of a 1000 Oe field can lead to a local electric field of 1000 V/cm, which can be sufficient to induce stimulation. Two approaches for achieving local stimulation relied on localization of nanoparticles and field profiles, respectively. The nanoparticles were localized via the aforementioned metastable physics. As for the field profiles, they were controlled by specially designed electromagnetic sources. Both approaches were used to achieve sub-mm firing in hippocampal cell cultures. This controllably induced neural firing was confirmed via standard calcium ion imaging and electroencephalography. (III) Engineering Electromagnetic Systems to Record Neural Activity with MENPs: A theoretical model was developed to use MENPs for contactless recording of local neural activity. With MENPs, neural firing from a 1 mm3 depth could generate a magnetic field of 100 pT a few millimeters above the skull. For comparison, this value is approximately 3 orders of magnitude higher than the field generated by the same brain volume without using MENPs, i.e., on the order of 100 fT. Such amplification of the magnetic field generated by MENPs has the potential to enable cost-effective magnetoencephalography (MEG) based brain imaging systems which could operate at room temperature in a shield-free environment

A state-of-the-art assessment of active structures

A state-of-the-art assessment of active structures with emphasis towards the applications in aeronautics and space is presented. It is felt that since this technology area is growing at such a rapid pace in many different disciplines, it is not feasible to cover all of the current research but only the relevant work as relates to aeronautics and space. Research in smart actuation materials, smart sensors, and control of smart/intelligent structures is covered. In smart actuation materials, piezoelectric, magnetostrictive, shape memory, electrorheological, and electrostrictive materials are covered. For sensory materials, fiber optics, dielectric loss, and piezoelectric sensors are examined. Applications of embedded sensors and smart sensors are discussed

FEM IMPLEMENTATIONS OF MAGNETOSTRICTIVE-BASED APPLICATIONS

Magnetostrictive transducers are used in a broad variety of applications that include linear pump drive mechanisms, active noise and vibration control systems and sonar systems. Optimization of their performance relies on accurate modeling of the static and dynamic behavior of magnetostrictive materials. The nonlinearity of some properties of magnetostrictive materials along with eddy current power losses occurring in both the magnetostrictive material and the magnetic circuit of the system makes this task particularly difficult. This thesis presents continuum level, three dimensional, finite element analysis of magnetostrictive-based applications for different operating conditions. The Finite element models (FEMs) are based on boundary value problems which are first introduced in the "differential" form (Chapter 2) and then derived to a "weak" form (Chapter 3) suitable for the implementation on the commercial finite element software, FEMLAB 3.1©. Structural mechanics and electromagnetics BVPs are used to predict the behavior of, respectively, structurally-involved parts and the electromagnetic circuit of a magnetostrictive-based application. In order to capture the magnetostrictive material's behavior, static and dynamic three-dimensional multi-physics BVPs include magneto-mechanical coupling to model magnetostriction and the effect of the magnetic stress tensor, also known as Maxwell stress tensor, and electromagnetic coupling to model eddy current power losses (time-harmonic and dynamic case only). The dynamic formulation is inspired by the finite element formulation in the Galerkin form introduced by Perez-Aparicio and Sosa [1], but focuses on a weak form formulation of the problem suitable for implementation in the commercial finite element software FEMLAB 3.1©. Implementation methods of the introduced models are described in Chapter 4. Finally, examples of these models are presented and, for the coupled magneto-mechanical FEM, compared to experimental results

An RST control design based on interval technique for piezomicropositoning systems with rate-dependent hysteresis nonlinearities

We propose a feedforward-feedback con-trol of piezomicropositioing systems devoted to pre-cise positioning over different operating conditions. Such systems exhibit rate-dependent hysteresis non-linearities and badly damped oscillations character-istics. First, we introduce a rate-dependent Prandtl-Ishlinskii (RDPI) inverse model for feeforward com-pensation of hysteresis. This yields to compensation that can be characterized by an uncertain linear model with disturbances. To model the uncertainties, we suggest to use intervals then we propose a new interval design for a RST structured feedback controller. The proposed design method permits to satisfy prescribed performances. Simulation and experiments on a piezo-electric tube actuator are carried out and demonstrate the efficiency of the proposed control design

Vibration control of structures with self-sensing piezoelectric actuators incorporating adaptive mechanisms.

Law Wai Wing.Thesis (M.Phil.)--Chinese University of Hong Kong, 2002.Includes bibliographical references (leaves 64-66).Abstracts in English and Chinese.摘要 --- p.iABSTRACT --- p.iiACKNOWLEDGEMENTS --- p.iiiCONTENTS --- p.ivLIST OF FIGURES --- p.viLIST OF TABLES --- p.ixChapter 1 --- INTRODUCTIONChapter 1.1 --- Background --- p.1Chapter 1.1.1 --- Piezoelectric Materials --- p.1Chapter 1.1.2 --- Self-sensing Actuation --- p.2Chapter 1.2 --- Literature Review --- p.3Chapter 1.3 --- Motivation --- p.5Chapter 1.4 --- Thesis Organization --- p.6Chapter 2 --- STRUCTURE MODELING AND FORMULATIONChapter 2.1 --- Overview of Piezoelectricity --- p.7Chapter 2.2 --- Modeling of the Smart Structure --- p.8Chapter 2.2.1 --- Electromechanical Conversion --- p.8Chapter 2.2.2 --- Model Derivation Using Hamilton's Principle --- p.10Chapter 2.3 --- Discretization of Equation of Motion --- p.15Chapter 2.4 --- Sensing Model of the Piezoelectric Sensor --- p.20Chapter 2.4.1 --- Strain Sensing Model --- p.21Chapter 2.4.2 --- Strain Rate Sensing Model --- p.23Chapter 2.5 --- Model Validation --- p.25Chapter 3 --- CONTROL OF SMART STRUCTUREChapter 3.1 --- Strain Rate Feedback Control --- p.27Chapter 3.2 --- Positive Position Feedback Control --- p.31Chapter 3.3 --- Unbalanced Bridge Effect on Closed Loop Stability --- p.36Chapter 3.4 --- Self-Compensation of Capacitance Variation --- p.39Chapter 4 --- EXPERIMENTAL STUDIESChapter 4.1 --- Experiment Setup --- p.47Chapter 4.2 --- Experiment Results --- p.48Chapter 4.2.1 --- Open Loop Response --- p.48Chapter 4.2.2 --- Closed Loop Response with Balanced Bridge --- p.49Chapter 4.2.3 --- Closed Loop Response with Unbalanced Bridge --- p.51Chapter 4.2.4 --- Closed Loop Response upon Sudden Change in Bridge Parameter --- p.53Chapter 4.2.5 --- Closed Loop Response upon Temperature Variation --- p.57Chapter 4.2.6 --- Frequency Response --- p.58Chapter 5 --- SUMMARYChapter 5.1 --- Conclusion --- p.51Chapter 5.2 --- Future Work --- p.62BIBLIOGRAPHY --- p.6

Self-Contained Hybrid Electro-Hydraulic Actuators using Magnetostrictive and Electrostrictive Materials

Hybrid electro-hydraulic actuators using smart materials along with flow rectification have been widely reported in recent years. The basic operation of these actuators involves high frequency bidirectional operation of an active material that is converted into unidirectional fluid motion by a set of valves. While theoretically attractive, practical constraints limit the efficacy of the solid-fluid hybrid actuation approach. In particular, inertial loads, fluid viscosity and compressibility combine with loss mechanisms inherent in the active material to limit the effective bandwidth of the driving actuator and the total output power. A hybrid actuator was developed by using magnetostrictive TerFeNOL-D as the active driving element and hydraulic oil as the working fluid. Tests, both with and without an external load, were carried out to measure the unidirectional performance of the actuator at different pumping frequencies and operating conditions. The maximum no-load output velocity was 84 mm/s with a 51 mm long rod and 88 mm/s with a 102 mm long rod, both noted around 325 Hz pumping frequency, while the blocked force was close to 89 N. Dynamic tests were performed to analyze the axial vibration characteristics of the Terfenol-D rods and frequency responses of the magnetic circuits. A second prototype actuator employing the same actuation principle was then designed by using the electrostrictive material PMN-32%PT as the driving element. Tests were conducted to measure the actuator performance for varying electrical input conditions and fluid bias pressures. The peak output velocity obtained was 330 mm/s while the blocked force was 63 N. The maximum volume flow rate obtained with the PMN-based actuator was more than double that obtained from the Terfenol-D-based actuator. Theoretical modeling of the dynamics of the coupled structural-hydraulic system is extremely complex and several models have been proposed earlier. At high pumping frequencies, the fluid inertia dominates the viscous effects and the problem becomes unsteady in nature. Due to high pressures inside the actuator and the presence of entrained air, compressibility of the hydraulic fluid is important. A new mathematical model of the hydraulic hybrid actuator was formulated in time-domain to show the basic operational principle under varying operating conditions and to capture the phenomena affecting system performance. Linear induced strain behavior was assumed to model the active material. Governing equations for the moving parts were obtained from force equilibrium considerations, while the coupled inertia-compliance of the fluid passages was represented by a lumped parameter approach to the transmission line model, giving rise to strongly coupled ordinary differential equations. Compressibility of the working fluid was incorporated by using the bulk modulus. The model was then validated using the measured performance of both the magnetostrictive and electrostrictive-based hybrid actuators

Design, Modeling and Performance Optimization of a Novel Rotary Piezoelectric Motor

This work has demonstrated a proof of concept for a torsional inchworm type motor. The prototype motor has shown that piezoelectric stack actuators can be used for rotary inchworm motor. The discrete linear motion of piezoelectric stacks can be converted into rotary stepping motion. The stacks with its high force and displacement output are suitable actuators for use in piezoelectric motor. The designed motor is capable of delivering high torque and speed. Critical issues involving the design and operation of piezoelectric motors were studied. The tolerance between the contact shoes and the rotor has proved to be very critical to the performance of the motor. Based on the prototype motor, a waveform optimization scheme was proposed and implemented to improve the performance of the motor. The motor was successfully modeled in MATLAB. The model closely represents the behavior of the prototype motor. Using the motor model, the input waveforms were successfully optimized to improve the performance of the motor in term of speed, torque, power and precision. These optimized waveforms drastically improve the speed of the motor at different frequencies and loading conditions experimentally. The optimized waveforms also increase the level of precision of the motor. The use of the optimized waveform is a break-away from the traditional use of sinusoidal and square waves as the driving signals. This waveform optimization scheme can be applied to any inchworm motors to improve their performance. The prototype motor in this dissertation as a proof of concept was designed to be robust and large. Future motor can be designed much smaller and more efficient with lessons learned from the prototype motor

Design and control of a self-sensing piezoelectric reticle assist device

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (p. 233-239).This thesis presents the design and control techniques of a device for managing the inertial loads on photoreticle of lithography scanners. Reticle slip, resulting from large inertial loads, is a factor limiting the throughput and accuracy of the lithography scanners. Our reticle-assist device completely eliminates reticle slip by carrying 96% of the inertial loads. The primary contributions of this thesis include the design and implementation of a practical high-force density reticle assist device, the development of a novel charge-controlled power amplifier with DC hysteresis compensation, and the development of a sensorless control method. A lithography scanner exposes a wafer by sweeping a slit of light passing through a reticle. The scanner controls the motion of the reticle and the wafer. The reticle-stage moves the photoreticle. To avoid deforming the reticle, it is held using a vacuum clamp. Each line scan consists of acceleration at the ends of the line and a constant-speed motion in the middle of the line, where exposure occurs. If the reticle's inertial force approaches or exceeds the clamp's limit, nanometer-level pre-sliding slip or sliding slip will occur. The assist device carries the inertial load by exerting a feedforward force on the reticle's edge. The device retracts back during the sensitive exposure interval to avoid disturbing the reticle. The reticle is at the heart of the scanner, where disturbances directly affect the printing accuracy. Our reticle assist device consists of an approach mechanism and a piezoelectric stack actuator. The approach mechanism positions the actuator 1-m from the reticle edge. The actuator, with 15-[mu]m range, extends to push on the reticle. We have developed control techniques to enable high-precision high-bandwidth force compensation without using any sensors. We have also developed a novel charge-controlled amplifier with a more robust feedback circuit and a method for hysteresis compensation at DC. These technologies were key to achieving high-bandwidth high-precision sensorless force control. When tested with a trapezoidal force profile with 6400 N/s rate and 60 N peak force, the device canceled 96% of the inertial force.by Darya Amin-Shahidi.Ph.D