Control of Hysteresis in Smart Actuators with Application to Micro-Positioning

Hysteresis in smart material actuators makes the effective use of these actuators quite challenging. The Preisach operator has been widely used to model smart material hysteresis. Motivated by positioning applications of smart actuators, this paper addresses the value inversion problem for a class of discretized Preisach operators, i.e., to find an optimal input trajectory given a desired output value. This problem is solved through optimal state transition of a finite state machine (FSM) that corresponds to the discretized Preisach operator. A state-space reduction scheme for the FSM is developed, which significantly saves the memory and the computation time. As an example, micro-positioning control of a magnetostrictive actuator is investigated. Experimental results are presented to demonstrate the effectiveness of the proposed approach

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

MODELING, ANALYSIS AND CONTROL OF FLEXIBLE SOLID-STATE HYSTERETIC ACTUATORS

A distributed parameters modeling and control framework for flexible solid-state hysteretic actuator is presented in this work. For the simplicity of analysis, the actuator dynamic behavior is decoupled and treated separately from the hysteresis nonlinearity. To include the effects of widely-used flexural mechanisms, a mass-spring-damper boundary condition is considered for system. Moreover, the effect of electromechanical actuation is included as a concentrate force at the boundary. The problem is then divided into two parts: first part deals with free motion analysis of system in order to obtain eigenvalues and eigenfunctions using the expansion theorem and a standard eigenvalue problem procedure. The effects of different boundary mass and spring values on the natural frequencies and mode shapes are demonstrated, which indicate their significant contribution to system performance. In the second part, forced motion analysis of system and its state-space representation are presented. A frequency based control strategy utilizing widely used Lyapunov theorem is designed to obtain an accurate control over the actuator motion. A robust variable structure control is incorporated into the developed controller for compensation of ever-present plant structural uncertainties. A full order state feedback observer is designed to accurately mimic the states of an unobservable plant. An optimization algorithm is developed to compute the optimal observer gain matrix. Various frequency tracking simulations are performed using feedback controller-observer model to observe the effect of modes deficiency on the tracking frequency bandwidth of the controller. Finally, for the accurate prediction of nonlinear multi-loop hysteresis effect, a major source of inaccuracies at quasi-static frequency, a recently developed hysteresis model based on three hysteric properties of piezoelectric material namely targeting of turning points, curve alignment and the wiping-out effect is used. Initially, the hysteresis nonlinearity is decoupled from the looping effect and modeled separately using an exponential function. The obtained exponential function is then utilized in a nonlinear mapping procedure, where it is mapped between consequent turning points recorded in model memory unit. This mapping also uses four constant shaping parameters - two for the ascending and two for the descending hysteresis trajectories. A proportional integral (PI) controller is used for the compensation of hysteresis nonlinearity. Performance of PI controller is validated using several numerical simulations. Finally, the method of combining robust feedback control strategy with the feedforward hysteresis compensation technique is presented to accomplish the precise control over actuator motion

Modeling and inverse feedforward control for conducting polymer actuators with hysteresis

Conducting polymer actuators are biocompatible with a small footprint, and operate in air or liquid media under low actuation voltages. This makes them excellent actuators for macro- and micro-manipulation devices, however, their positioning ability or accuracy is adversely affected by their hysteresis non-linearity under open-loop control strategies. In this paper, we establish a hysteresis model for conducting polymer actuators, based on a rate-independent hysteresis model known as the Duhem model. The hysteresis model is experimentally identified and integrated with the linear dynamics of the actuator. This combined model is inverted to control the displacement of the tri-layer actuators considered in this study, without using any external feedback. The inversion requires an inverse hysteresis model which was experimentally identified using an inverse neural network model. Experimental results show that the position tracking errors are reduced by more than 50% when the hysteresis inverse model is incorporated into an inversion-based feedforward controller, indicating the potential of the proposed method in enabling wider use of such smart actuators

Towards improving positioning accuracy of conducting polymer actuators

Recently, there have been significant developments in conducting polymers, particularly in their synthesis and use as electromechanical actuators. This is mainly due to their many promising features including biocompatibility, high force to weight ratio, suitability to open loop control. On the other hand, they suffer from nonlinear problems such as hysteresis and creep. With this in mind, it is the aim of this study to evaluate the existence level of these nonlinearities and their mathematical modeling in order to improve the positioning accuracy of conducting polymer actuators. The polymer actuator considered in this study which has a symmetrical structure can operate in both liquid and non-liquid media as opposed to its predecessor. The actuator drives a rigid link, like positioning a payload. The experimental results demonstrate that while the hysteresis is negligibly small, the level of the creep is significant enough to model it and subsequently employ the model to improve steady-state positioning of the actuator. Based on experimental results, a viscoelastic model is employed to describe the creep behaviour. The outcomes of this study will pave the way towards understanding of the limitations as well as potential usefulness of conducting polymer actuators in many cutting edge applications ranging from biomedical to micro/nano manipulation systems

Shape memory alloys for aerospace, recent developments, and new applications: a short review

Shape memory alloys (SMAs) show a particular behavior that is the ability to recuperate the original shape while heating above specific critical temperatures (shape memory effect) or to withstand high deformations recoverable while unloading (pseudoelasticity). In many cases the SMAs play the actuator's role. Starting from the origin of the shape memory effect, the mechanical properties of these alloys are illustrated. This paper presents a review of SMAs applications in the aerospace field with particular emphasis on morphing wings (experimental and modeling), tailoring of the orientation and inlet geometry of many propulsion system, variable geometry chevron for thrust and noise optimization, and more in general reduction of power consumption. Space applications are described too: to isolate the micro-vibrations, for low-shock release devices and self-deployable solar sails. Novel configurations and devices are highlighted too

A robust loop-shaping approach to fast and accurate nanopositioning

Peer reviewedPreprin

Butterworth Pattern-based Simultaneous Damping and Tracking Controller Designs for Nanopositioning Systems

Peer reviewedPublisher PD

Advances in Tracking Control for Piezoelectric Actuators Using Fuzzy Logic and Hammerstein-Wiener Compensation

first_page settings Open AccessArticle Advances in Tracking Control for Piezoelectric Actuators Using Fuzzy Logic and Hammerstein-Wiener Compensation by Cristian Napole 1,* [OrcID] , Oscar Barambones 1,* [OrcID] , Isidro Calvo 1 [OrcID] , Mohamed Derbeli 1 [OrcID] , Mohammed Yousri Silaa 1 [OrcID] and Javier Velasco 2 [OrcID] 1 System Engineering and Automation Deparment, Faculty of Engineering of Vitoria-Gasteiz, Basque Country University (UPV/EHU), 01006 Vitoria-Gasteiz, Spain 2 Fundación Centro de Tecnologías Aeronáuticas (CTA), Juan de la Cierva 1, 01510 Miñano, Spain * Authors to whom correspondence should be addressed. Mathematics 2020, 8(11), 2071; https://doi.org/10.3390/math8112071 Received: 23 October 2020 / Revised: 16 November 2020 / Accepted: 17 November 2020 / Published: 20 November 2020 (This article belongs to the Special Issue Fuzzy Applications in Industrial Engineering) Download PDF Browse Figures Abstract Piezoelectric actuators (PEA) are devices that are used for nano- microdisplacement due to their high precision, but one of the major issues is the non-linearity phenomena caused by the hysteresis effect, which diminishes the positioning performance. This study presents a novel control structure in order to reduce the hysteresis effect and increase the PEA performance by using a fuzzy logic control (FLC) combined with a Hammerstein–Wiener (HW) black-box mapping as a feedforward (FF) compensation. In this research, a proportional-integral-derivative (PID) was contrasted with an FLC. From this comparison, the most accurate was taken and tested with a complex structure with HW-FF to verify the accuracy with the increment of complexity. All of the structures were implemented in a dSpace platform to control a commercial Thorlabs PEA. The tests have shown that an FLC combined with HW was the most accurate, since the FF compensate the hysteresis and the FLC reduced the errors; the integral of the absolute error (IAE), the root-mean-square error (RMSE), and relative root-mean-square-error (RRMSE) for this case were reduced by several magnitude orders when compared to the feedback structures. As a conclusion, a complex structure with a novel combination of FLC and HW-FF provided an increment in the accuracy for a high-precision PEA.This research was funded by Basque Government and UPV/EHU projects

Workshop on "Control issues in the micro / nano - world".

International audienceDuring the last decade, the need of systems with micro/nanometers accuracy and fast dynamics has been growing rapidly. Such systems occur in applications including 1) micromanipulation of biological cells, 2) micrassembly of MEMS/MOEMS, 3) micro/nanosensors for environmental monitoring, 4) nanometer resolution imaging and metrology (AFM and SEM). The scale and requirement of such systems present a number of challenges to the control system design that will be addressed in this workshop. Working in the micro/nano-world involves displacements from nanometers to tens of microns. Because of this precision requirement, environmental conditions such as temperature, humidity, vibration, could generate noise and disturbance that are in the same range as the displacements of interest. The so-called smart materials, e.g., piezoceramics, magnetostrictive, shape memory, electroactive polymer, have been used for actuation or sensing in the micro/nano-world. They allow high resolution positioning as compared to hinges based systems. However, these materials exhibit hysteresis nonlinearity, and in the case of piezoelectric materials, drifts (called creep) in response to constant inputs In the case of oscillating micro/nano-structures (cantilever, tube), these nonlinearities and vibrations strongly decrease their performances. Many MEMS and NEMS applications involve gripping, feeding, or sorting, operations, where sensor feedback is necessary for their execution. Sensors that are readily available, e.g., interferometer, triangulation laser, and machine vision, are bulky and expensive. Sensors that are compact in size and convenient for packaging, e.g., strain gage, piezoceramic charge sensor, etc., have limited performance or robustness. To account for these difficulties, new control oriented techniques are emerging, such as[d the combination of two or more ‘packageable' sensors , the use of feedforward control technique which does not require sensors, and the use of robust controllers which account the sensor characteristics. The aim of this workshop is to provide a forum for specialists to present and overview the different approaches of control system design for the micro/nano-world and to initiate collaborations and joint projects