Frederik Stefanski

Design, modelling and control of a micro-positioning actuator based on magnetic shape memory alloys

This paper presents an actuator based on magnetic shape memory alloys (MSMAs) suitable for precise positioning in a wide range (up to 1 mm). The actuator is based on the spring returned operating mode and uses a Smalley wave spring to maintain the same operating parameters of a classical coil spring, while being characterized by a smaller dimension. The MSMA element inside the actuator provides a deformation when excited by an external magnetic field, but its behavior is characterized by an asymmetric and saturated hysteresis. Thus, two models are exploited in this work to represent such a non-linear behavior, i.e., the modified and generalized Prandtl–Ishlinskii models. These models are particularly suitable for control purposes due to the existence of their analytical inversion that can be easily exploited in real time control systems. To this aim, this paper investigates three closed-loop control strategies, namely a classical PID regulator, a PID regulator with direct hysteresis compensation, and a combined PID and feedforward compensation strategy. The effectiveness of both modelling and control strategies applied to the designed MSMA-based actuator is illustrated by means of experimental results.

Share Mode Magnetorheological Dampers for Vibration Attenuation in Domestic Washing Machines

The article presents a new approach for noise reduction of a household washing machine. The noise sources and phenomenon were described. After investigation of a currently used solution, and alternative available solutions, a new approach was presented. Design and tests of a low costs magnetorheological fluid, semi-active damper were presented. The input parameters for the new damper were identified on the base of investigation of a viscous damper, used in washing machines. The described MR damper was applied in a washing machine suspension system. Next, a study of washing machine acceleration RMS for different unbalanced masses and durum rotations, were performed. During this research the new damper was switched on and off, to shows it influence on the acceleration. The end results show that the new designed dampers can strongly reduce the vibrations of the washing machine housing and its plastic components.

Hysteresis Modelling of a Piezoelectric Tube Actuator

The article concerns about a piezoelectric tube actuator hysteresis. The actuator can bend in two directions and application of this piezo elements can entail new features and capabilities of mechatronic devices. Unfortunately as other smart materials, piezoelectric materials are distinguished by hysteresis phenomenon. Authors present result of displacement measurement, which was performed for decreasing amplitude cosine input signal. Based on this result phenomenological generalized Prandtl-Ishlinskii model was matched. The results of the piezoelectric tube and the model displacement were compered.

Research of Basic Parameters of Piezoelectric Tube Actuator

The article present basic research of the piezoelectric tube actuator. In this study the actuator was tested for various DC voltages. Further hysteresis and creep effect of the piezo ceramic material were presented. The next point of this research was positioning control of tube under closed loop control. For this purpose classic PID control algorithm was applied, with a negative feedback from laser displacement sensor. The control software was developed under Matlab Simulink and dSPACE control system, which allows fast modification and testing.

Accuracy of Hysteresis Modeling in Smart Actuator with MSMA

This paper is focused on hysteresis modeling in actuator with magnetic shape memory alloy, briefly MSMA. MSMAs are new group of active materials which change shape in external magnetic field. Active element is made of Ni2MnGa, and it is very suitable to use in actuators for positioning, because this alloy combines great strains (up to 6%) and good dynamic properties. On the other side, it is distinguished by nonlinear behavior. In this case, it is wide saturated asymmetric hysteresis. Reason for that is a kind of internal friction called twining stress. Such drawback does not allow to precise position control in open-loop control system. Described in this paper method for hysteresis modeling is based on mathematical formulation, which utilizes so-called phenomenological models. Hysteresis modeling is provided by generalized Prandtl-Ishlinskii model (GPIM) where hyperbolic tangents were used as envelop functions in play operator. This paper describes modeling accuracy for different GPIM structures. Actuator is designed for high-strain applications up to 1 mm. Data acquisition was provided by dSPACE system.

Open loop control of piezoelectric tube transducer

Abstract This paper is focused on the open loop control of a piezoelectric tube actuator, hindered by a strong hysteresis. The actuator was distinguished with 22 % hysteresis, which hinders the positioning of piezoelectric actuator. One of the possible ways to solve this problem is application of an accurate analytical inversed model of the hysteresis in the control loop. In this paper generalized Prandtl-Ishlinskii model was used for both modeling and open loop control of the piezoelectric actuator. Achieved modeling error does not exceed max. 2.34 % of the whole range of tube deflection. Finally, the inverse hysteresis model was applied to the control line of the tube. For the same input signal (damped sine 0.2 Hz) as for the model estimation the positioning error was max. 4.6 % of the tube deflection. Additionally, for a verification reason three different complex harmonic functions were applied. For the verification functions, still a good positioning was obtained with positioning error of max.4.56 %, 6.75 %and5.6%of the tube deflection.

Magnetic Shape Memory Alloys Modelling and Pneumatic Applications

Very generally material science could be divided into two groups: scientists who try to invent new materials or improve existing ones and those who work on finding the best applications for the modern materials. Among them there is group named “smart materials” or “active materials”, which have ability to change theirs properties according to the external stimulation. One of the relatively most recent smart material is magnetic shape memory alloy, MSMA in abbreviation. The authors of the article focus on testing samples of this material and try to adapt them to use in fluid devices. The paper mentions about some most interesting valves’ designs equipped with smart materials and summaries the previous MSMA research of the authors. It begins with literature overview of smart material applications in pneumatic or hydraulic valves. There is only one example of MSMA application in valve, therefore the overview concerns mainly the use of piezoelectric, thermal shape memory alloys and giant magnetostrictive materials. Next section describes general properties of the magnetic shape memory alloys and underlines the differences between more widely known Thermal Shape Memory Alloys and MSMA materials. One of the most important property is wide, nonsymmetrical hysteresis in static characteristics of the material, which can be seen as advantage or disadvantage, depending on the application. The material preserves its shape until perpendicular magnetic field or additional force appear. The authors mention about modeling MSMA hysteresis aspect. Three different hysteresis models were briefly described: Generalized Prandtl-Ischlinski, Preisach and Krasnoselskii-Pokrovskii. The last section treats about the current MSMA based valve design concept. It assumes usage of two identical pieces of MSMA materials and energize them oppositely. There is flapper mounted between MSMA samples, which displacement depends on the MSMA elongations. This actuator type is called “push-push” type. Lack of the return spring result in remaining of the flapper in its final position after decreasing of the supply current. The advantage of the solution could be lowering energy consumption of the valve, when the valve setting changes relatively rare during its work. In the future, the presented hysteresis models could improve the work of such MSMA based valve.

Pneumatic single flapper nozzle valve driven by piezoelectric tube

The article presents a construction, static testing and modelling of a single flapper nozzle pneumatic valve. Authors show testing of piezo tube PT230 which distinguishing feature is deflection in two directions. This testing is preliminary work in design of a novel electropneumatic valve. Studies have been performed on a special designed bench which consists of a pneumatic valve, which used piezo tube as a flapper. Data acquisition process and control were performed by dSPACE system. The preformed static pressure control tests, confirmed applicability of tube actuator in flapper nozzle type valves. Obtained results were compared with simulation model prepared in Matlab Simulink software. Streszczenie. Artykul zawiera opis konstrukcji, badania statyczne i modelowanie zaworu typu dysza przyslona. Autorzy zaprezentowali badania piezo rurki model PT230, ktorej cechą charakterystyczną jest mozliwośc odksztalcenia w dwoch kierunkach. Praca ta jest przygotowaniem do konstrukcji nowego zaworu elektropneumatycznego. Badania zostaly wykonane na specjalnie w tym celu wykonanym stanowisku zawierającym zawor, ktorym zastosowano piezo rurke jako przyslone. Procesy akwizycji danych oraz sterowania wykonane zostaly w systemie dSPACE. Przeprowadzone badania statyczne sterowania ciśnieniem wyjściowym, potwierdzają mozliwośc zastosowania piezo rurki w zaworach typu dysza przyslona. Zarejestrowane wyniki poddano porownaniu z modelem przygotowanym w oprogramowaniu Matlab Simulink. (Zawor pneumatyczny typu dysza przyslona z rurką piezoelektryczną jako elementem zadającym)

Multichannel High Voltage Amplifier for Piezo Actuators

This paper describes investigations of a low cost high voltage amplifier, which was based on specialized operational amplifiers. The purpose of the amplifier is to control piezoelectric actuators with many electrodes, such as bimorph benders, piezoelectric tubes, ring and disc benders. Proposed amplifier has two independent channels which can be configured for the specific research aim. Every channel of the device can works in inverted or non inverted mode. Also the voltage gain and current limit can be set separately.

Characteristics of the Improved Magnetic Shape Memory Alloy Actuator Test Stand

The article describes improved magnetic shape memory alloy actuator (MSMA actuator) test stand and the previously made stand. There are pointed weak sides of the first stand and the improvements in the new one. Several quasi-static measurements were performed and results were compared between both measurement stands. The MSMA actuator characterises with significant hysteresis loop, but improved test stand allowed to reduce its width. The increased rigidity of the stand excluded influence of stand deformations on the results. The described stand resulted with similar but improved measurements of the MSMA actuator characteristics, which also proved the correctness of the previous results.