Special Issue "Cooperative Microactuator Systems"

A special issue of Actuators (ISSN 2076-0825). This special issue belongs to the section "Miniaturized and Micro Actuators".

Deadline for manuscript submissions: closed (15 September 2021) | Viewed by 7951

Special Issue Editors

Prof. Dr. Manfred Kohl
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Guest Editor
Institute of Microstructure Technology, Karlsruhe Institute of Technology (KIT), Postfach 3640, D-76021 Karlsruhe, Germany
Interests: smart materials; shape memory materials; piezoelectrics; magnetic materials; microtechnology; multistable microactuators; cooperative microactuators; intrinsic sensors
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Stefan Seelecke
E-Mail Website
Guest Editor
Department of Systems Engineering and Department of Material Science and Engineering, Saarland University, 66119 Saarbrücken, Germany
Interests: smart material systems; actuators; sensors; dielectric elastomers; shape memory alloys; elastocalorics
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Ulrike Wallrabe
E-Mail Website
Guest Editor
Laboratory for Microactuators IMTEK—Department of Microsystems Engineering University of Freiburg Georges-Koehler-Allee 102 79110 Freiburg, Germany
Interests: actuation mechanism for adaptive optical elements; unusual field patterns in piezoelectric actuators; magnetic micro actuators; processes and application of 3D solenoidal micro coils; wireless energy transfer
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Isssue collects the emerging research activities in the field of cooperative microactuator systems, which are expected to generate new synergies, e.g. through parallelization, cascading and multistability as well as through inherent sensing. New theoretically founded concepts will be required for understanding the complex coupling and synergy effects due to the close neighbourhood of microactuators in small space. Furthermore, new methods for design, fabrication and control will be needed to enable the cooperation of similar or different microactuators. This Special Issue seeks contributions in the fields of:

  1. Locomotion systems
  2. Manipulation of objects at different length and time scales
  3. Adaptive optical and mechanical systems
  4. Fluid flow control systems

Prof. Dr. Manfred Kohl
Prof. Dr. Stefan Seelecke
Prof. Dr. Ulrike Wallrabe
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Microactuator systems
  • Inherent sensing 
  • Microsystems technology
  • Integration of smart materials
  • Modeling of multiphysical coupling effects
  • Coupled simulation of complex systems
  • Control and systems engineering

Published Papers (9 papers)

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Research

Article
System-Level Modelling and Simulation of a Multiphysical Kick and Catch Actuator System
Actuators 2021, 10(11), 279; https://doi.org/10.3390/act10110279 - 21 Oct 2021
Viewed by 498
Abstract
This paper presents a system-level model of a microsystem architecture deploying cooperating microactuators. An assembly of a piezoelectric kick-actuator and an electromagnetic catch-actuator manipulates a structurally unconnected, magnetized micromirror. The absence of mechanical connections allows for large deflections and multistability. Closed-loop feedback control [...] Read more.
This paper presents a system-level model of a microsystem architecture deploying cooperating microactuators. An assembly of a piezoelectric kick-actuator and an electromagnetic catch-actuator manipulates a structurally unconnected, magnetized micromirror. The absence of mechanical connections allows for large deflections and multistability. Closed-loop feedback control allows this setup to achieve high accuracy, but requires fast and precise system-level models of each component. Such models can be generated directly from large-scale finite element (FE) models via mathematical methods of model order reduction (MOR). A special challenge lies in reducing a nonlinear multiphysical FE model of a piezoelectric kick-actuator and its mechanical contact to a micromirror, which is modeled as a rigid body. We propose to separate the actuator–micromirror system into two single-body systems. This step allows us to apply the contact-induced forces as inputs to each sub-system and, thus, avoid the nonlinear FE model. Rather, we have the linear model with nonlinear input, to which established linear MOR methods can be applied. Comparisons between the reference FE model and the reduced order model demonstrate the feasibility of the proposed methodology. Finally, a system-level simulation of the whole assembly, including two actuators, a micromirror and a simple control circuitry, is presented. Full article
(This article belongs to the Special Issue Cooperative Microactuator Systems)
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Article
Investigation of the Dynamics of a 2-DoF Actuation Unit Cell for a Cooperative Electrostatic Actuation System
Actuators 2021, 10(10), 276; https://doi.org/10.3390/act10100276 - 18 Oct 2021
Viewed by 768
Abstract
The mechanism of the inchworm motor, which overcomes the intrinsic displacement and force limitations of MEMS electrostatic actuators, has undergone constant development in the past few decades. In this work, the electrostatic actuation unit cell (AUC) that is designed to cooperate with many [...] Read more.
The mechanism of the inchworm motor, which overcomes the intrinsic displacement and force limitations of MEMS electrostatic actuators, has undergone constant development in the past few decades. In this work, the electrostatic actuation unit cell (AUC) that is designed to cooperate with many other counterparts in a novel concept of a modular-like cooperative actuator system is examined. First, the cooperative system is briefly discussed. A simplified analytical model of the AUC, which is a 2-Degree-of-Freedom (2-DoF) gap-closing actuator (GCA), is presented, taking into account the major source of dissipation in the system, the squeeze-film damping (SQFD). Then, the results of a series of coupled-field numerical simulation studies by the Finite Element Method (FEM) on parameterized models of the AUC are shown, whereby sensible comparisons with available analytical models from the literature are made. The numerical simulations that focused on the dynamic behavior of the AUC highlighted the substantial influence of the SQFD on the pull-in and pull-out times, and revealed how these performance characteristics are considerably determined by the structure’s height. It was found that the pull-out time is the critical parameter for the dynamic behavior of the AUC, and that a larger damping profile significantly shortens the actuator cycle time as a consequence. Full article
(This article belongs to the Special Issue Cooperative Microactuator Systems)
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Article
Large Stepwise Discrete Microsystem Displacements Based on Electrostatic Bending Plate Actuation
Actuators 2021, 10(10), 272; https://doi.org/10.3390/act10100272 - 15 Oct 2021
Viewed by 413
Abstract
We present the design, fabrication, and experimental characterization of microsystems achieving large and stepwise discrete displacements. The systems consist of electrostatic bending plate actuators linked in a chain with increasing electrode gaps to allow a stepwise system displacement. A derived analytic transfer function [...] Read more.
We present the design, fabrication, and experimental characterization of microsystems achieving large and stepwise discrete displacements. The systems consist of electrostatic bending plate actuators linked in a chain with increasing electrode gaps to allow a stepwise system displacement. A derived analytic transfer function permits to evaluate the influence of the system components on both the total and the stepwise system displacement. Based on calculation and simulation results, systems featuring 5, 8, 10, 13, and 16 steps are modeled and fabricated using a dicing-free SOI-fabrication process. During experimental voltage- and time-dependent system characterization, the minimum switching speed of the electrostatic actuators is 1 ms. Based on the guiding spring stiffness and the switching time, step-by-step and collective activations of the microsystems are performed and the system properties are derived. Furthermore, we analyze the influence of the number of steps on the total system displacement and present 16-step systems with a total maximum displacement of 230.7 ± 0.9 µm at 54 V. Full article
(This article belongs to the Special Issue Cooperative Microactuator Systems)
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Article
On the Static Pull-In of Tilting Actuation in Electromagnetically Levitating Hybrid Micro-Actuator: Theory and Experiment
Actuators 2021, 10(10), 256; https://doi.org/10.3390/act10100256 - 29 Sep 2021
Cited by 1 | Viewed by 644
Abstract
This work presents the results of the experimental and theoretical study of the static pull-in of tilting actuation executed by a hybrid levitation micro-actuator (HLMA) based on the combination of inductive levitation and electrostatic actuation. A semi-analytical model to study such a pull-in [...] Read more.
This work presents the results of the experimental and theoretical study of the static pull-in of tilting actuation executed by a hybrid levitation micro-actuator (HLMA) based on the combination of inductive levitation and electrostatic actuation. A semi-analytical model to study such a pull-in phenomenon is developed, for the first time, as a result of using the qualitative technique based on the Lagrangian approach to analyze inductive contactless suspensions and a recent progress in the calculation of mutual inductance and force between two circular filaments. The obtained non-linear model, accounting for two degrees of freedom of the actuator, allows us to predict accurately the static pull-in displacement and voltage. The results of modeling were verified experimentally and agree well with measurements. Full article
(This article belongs to the Special Issue Cooperative Microactuator Systems)
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Article
Model-Based Design Optimization of Soft Polymeric Domes Used as Nonlinear Biasing Systems for Dielectric Elastomer Actuators
Actuators 2021, 10(9), 209; https://doi.org/10.3390/act10090209 - 27 Aug 2021
Cited by 1 | Viewed by 702
Abstract
Due to their unique combination of features such as large deformation, high compliance, lightweight, energy efficiency, and scalability, dielectric elastomer (DE) transducers appear as highly promising for many application fields, such as soft robotics, wearables, as well as micro electro-mechanical systems (MEMS). To [...] Read more.
Due to their unique combination of features such as large deformation, high compliance, lightweight, energy efficiency, and scalability, dielectric elastomer (DE) transducers appear as highly promising for many application fields, such as soft robotics, wearables, as well as micro electro-mechanical systems (MEMS). To generate a stroke, a membrane DE actuator (DEA) must be coupled with a mechanical biasing system. It is well known that nonlinear elements, such as negative-rate biasing springs (NBS), permit a remarkable increase in the DEA stroke in comparison to standard linear springs. Common types of NBS, however, are generally manufactured with rigid components (e.g., steel beams, permanent magnets), thus they appear as unsuitable for the development of compliant actuators for soft robots and wearables. At the same time, rigid NBSs are hard to miniaturize and integrate in DE-based MEMS devices. This work presents a novel type of soft DEA system, in which a large stroke is obtained by using a fully polymeric dome as the NBS element. More specifically, in this paper we propose a model-based design procedure for high-performance DEAs, in which the stroke is maximized by properly optimizing the geometry of the biasing dome. First, a finite element model of the biasing system is introduced, describing how the geometric parameters of the dome affect its mechanical response. After conducting experimental calibration and validation, the model is used to develop a numerical design algorithm which finds the optimal dome geometry for a given DE membrane characteristics. Based on the optimized dome design, a soft DEA prototype is finally assembled and experimentally tested. Full article
(This article belongs to the Special Issue Cooperative Microactuator Systems)
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Article
Design and Characterization of an Electrostatic Constant-Force Actuator Based on a Non-Linear Spring System
Actuators 2021, 10(8), 192; https://doi.org/10.3390/act10080192 - 11 Aug 2021
Cited by 1 | Viewed by 849
Abstract
In recent years, tissue engineering with mechanical stimulation has received considerable attention. In order to manipulate tissue samples, there is a need for electromechanical devices, such as constant-force actuators, with integrated deflection measurement. In this paper, we present an electrostatic constant-force actuator allowing [...] Read more.
In recent years, tissue engineering with mechanical stimulation has received considerable attention. In order to manipulate tissue samples, there is a need for electromechanical devices, such as constant-force actuators, with integrated deflection measurement. In this paper, we present an electrostatic constant-force actuator allowing the generation of a constant force and a simultaneous displacement measurement intended for tissue characterization. The system combines a comb drive structure and a constant-force spring system. A theoretical overview of both subsystems, as well as actual measurements of a demonstrator system, are provided. Based on the silicon-on-insulator technology, the fabrication process of a moveable system with an extending measurement tip is shown. Additionally, we compare measurement results with simulations. Our demonstrator reaches a constant-force of 79 ± 2 μN at an operating voltage of 25 V over a displacement range of approximately 40 μm, and the possibility of adjusting the constant-force by changing the voltage is demonstrated. Full article
(This article belongs to the Special Issue Cooperative Microactuator Systems)
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Article
Design and Optimal Control of a Multistable, Cooperative Microactuator
Actuators 2021, 10(8), 183; https://doi.org/10.3390/act10080183 - 04 Aug 2021
Cited by 3 | Viewed by 679
Abstract
In order to satisfy the demand for the high functionality of future microdevices, research on new concepts for multistable microactuators with enlarged working ranges becomes increasingly important. A challenge for the design of such actuators lies in overcoming the mechanical connections of the [...] Read more.
In order to satisfy the demand for the high functionality of future microdevices, research on new concepts for multistable microactuators with enlarged working ranges becomes increasingly important. A challenge for the design of such actuators lies in overcoming the mechanical connections of the moved object, which limit its deflection angle or traveling distance. Although numerous approaches have already been proposed to solve this issue, only a few have considered multiple asymptotically stable resting positions. In order to fill this gap, we present a microactuator that allows large vertical displacements of a freely moving permanent magnet on a millimeter-scale. Multiple stable equilibria are generated at predefined positions by superimposing permanent magnetic fields, thus removing the need for constant energy input. In order to achieve fast object movements with low solenoid currents, we apply a combination of piezoelectric and electromagnetic actuation, which work as cooperative manipulators. Optimal trajectory planning and flatness-based control ensure time- and energy-efficient motion while being able to compensate for disturbances. We demonstrate the advantage of the proposed actuator in terms of its expandability and show the effectiveness of the controller with regard to the initial state uncertainty. Full article
(This article belongs to the Special Issue Cooperative Microactuator Systems)
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Article
3-Bit Digital-to-Analog Converter with Mechanical Amplifier for Binary Encoded Large Displacements
Actuators 2021, 10(8), 182; https://doi.org/10.3390/act10080182 - 04 Aug 2021
Cited by 4 | Viewed by 798
Abstract
We present the design, fabrication, and characterization of a MEMS-based 3-bit Digital-to-Analog Converter (DAC) that allows the generation of large displacements. The DAC consists of electrostatic bending-plate actuators that are connected to a mechanical amplifier (mechAMP), enabling the amplification of the DAC output [...] Read more.
We present the design, fabrication, and characterization of a MEMS-based 3-bit Digital-to-Analog Converter (DAC) that allows the generation of large displacements. The DAC consists of electrostatic bending-plate actuators that are connected to a mechanical amplifier (mechAMP), enabling the amplification of the DAC output displacement. Based on a parallel binary-encoded voltage signal, the output displacement of the system can be controlled in an arbitrary order. Considering the system design, we present a simplified analytic model, which was confirmed by FE simulation results. The fabricated systems showed a total stroke of approx. 149.5 ± 0.3 µm and a linear stepwise displacement of 3 bit correlated to 23 ≙ eight defined positions at a control voltage of 60 V. The minimum switching time between two input binary states is 0.1 ms. We present the experimental characterization of the system and the DAC and derive the influence of the mechAMP on the functionality of the DAC. Furthermore, the resonant behavior and the switching speed of the system are analyzed. By changing the electrode activation sequence, 27 defined positions are achieved upgrading the 3-bit systems into a 3-tri-state (33) system. Full article
(This article belongs to the Special Issue Cooperative Microactuator Systems)
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Article
Bi-Directional Origami-Inspired SMA Folding Microactuator
Actuators 2021, 10(8), 181; https://doi.org/10.3390/act10080181 - 03 Aug 2021
Viewed by 1222
Abstract
We present the design, fabrication, and characterization of single and antagonistic SMA microactuators allowing for uni- and bi-directional self-folding of origami-inspired devices, respectively. Test devices consist of two triangular tiles that are interconnected by double-beam-shaped SMA microactuators fabricated from thin SMA foils of [...] Read more.
We present the design, fabrication, and characterization of single and antagonistic SMA microactuators allowing for uni- and bi-directional self-folding of origami-inspired devices, respectively. Test devices consist of two triangular tiles that are interconnected by double-beam-shaped SMA microactuators fabricated from thin SMA foils of 20 µm thickness with memory shapes set to a 180° folding angle. Bi-directional self-folding is achieved by combining two counteracting SMA microactuators. We present a macromodel to describe the engineering stress–strain characteristics of the SMA foil and to perform FEM simulations on the characteristics of self-folding and the corresponding local evolution of phase transformation. Experiments on single-SMA microactuators demonstrate the uni-directional self-folding and tunability of bending angles up to 180°. The finite element simulations qualitatively describe the main features of the observed torque-folding angle characteristics and provide further insights into the angular dependence of the local profiles of the stress and martensite phase fraction. The first antagonistic SMA microactuators reveal bi-directional self-folding in the range of −44° to +40°, which remains well below the predicted limit of ±100°. Full article
(This article belongs to the Special Issue Cooperative Microactuator Systems)
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