Special Issue "Modeling, Design, and Optimization of Flexible Mechanical Systems"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Mechanical Engineering".

Deadline for manuscript submissions: closed (31 March 2021).

Special Issue Editors

Prof. Dr. Renato Vidoni
E-Mail Website
Guest Editor
Faculty of Science and Technology, Free University of Bozen-Bolzano, 39100 Bolzano, Italy
Interests: high-performance automatic machines; optimal motion planning of industrial robots and automatic systems; agrirobotics and mechatronics
Dr.-Ing. Erich Wehrle
E-Mail Website
Guest Editor
Faculty of Science and Technology, Free University of Bozen-Bolzano, 39100 Bolzano, Italy
Interests: design optimization of lightweight mechanical structures and systems; vibrations; crash; multibody and structural dynamics
Dr. Ilaria Palomba
E-Mail Website
Guest Editor
Faculty of Science and Technology, Free University of Bozen-Bolzano, 39100 Bolzano, Italy
Interests: theoretical and experimental investigations in the fields of mechanics of machines, mechanical vibrations, multibody dynamics, and industrial and collaborative robotics
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Special Issue Information

Dear Colleagues,

Flexible mechanical systems are present in a growing number of fields, which include robotics, aerospace and manufacturing. In the development of, e.g., compliant mechanisms and collaborative robots, flexibility is a desired design feature. Flexibility, however, can also be a negative result of lightweight design, high loads, and high-speed operation, which need to be constrained. Consideration of flexibility is therefore of great consequence in the design and analysis of high-performance mechanisms. As such, dynamic models must take flexibility into account to ensure accuracy but be as simple as possible to maintain adequate numerical conditioning and computational efficiency. Innovative and novel modeling approaches are of special interest, as well as techniques of model validation and parameter identification. Once properly modeled and their requirements formulated, diverse methods can be used to design and dimension of flexible mechanical systems. These include structural modification and design optimization, which can be used to optimally design such systems. This Special Issue of the journal Applied Sciences encompasses the modeling, analysis, design, and optimization of flexible mechanical systems.

We invite contributions to this Special Issue on topics including but not limited to the following:

  • Modeling of flexible and compliant mechanisms with:
    • Multibody dynamics;
    • Finite elements;
  • Modeling aspects:
    • Vibrations;
    • Nonlinear dynamics;
    • Nonlinear geometry for large deformations;
    • Numerical aspects;
    • Design sensitivity;
  • Model validation:
    • Parameter identification;
    • Model updating;
  • Design of flexible and compliant mechanisms:
    • Utilizing natural motion;
    • Analytical methods;
    • Design optimization;
    • Topology optimization;
    • Structural modification;
  • Applications including, but not limited to:
    • Lightweight robotics;
    • Morphing aerospace structures;
    • Mechatronic systems;
    • Manufacturing systems.
Prof. Dr. Renato Vidoni
Dr.-Ing. Erich Wehrle
Dr. Ilaria Palomba
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 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

  • Flexible multibody systems
  • Compliant mechanisms
  • Nonlinear dynamic models
  • Finite element models
  • Parameter identification
  • Model validation
  • Design optimization

Published Papers (11 papers)

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Research

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Open AccessArticle
Multiresolution Topology Optimization of Large-Deformation Path-Generation Compliant Mechanisms with Stress Constraints
Appl. Sci. 2021, 11(6), 2479; https://doi.org/10.3390/app11062479 - 10 Mar 2021
Viewed by 309
Abstract
Topology optimization is a powerful numerical tool in the synthesis of lightweight structures and compliant mechanisms. Compliant mechanisms present challenges for topology optimization, as they typically exhibit large displacements and rotations. Path-generation mechanisms are a class of mechanisms that are designed to follow [...] Read more.
Topology optimization is a powerful numerical tool in the synthesis of lightweight structures and compliant mechanisms. Compliant mechanisms present challenges for topology optimization, as they typically exhibit large displacements and rotations. Path-generation mechanisms are a class of mechanisms that are designed to follow an exact path. The characteristics of compliant mechanisms therefore exclude the validity of linear finite-element analysis to ensure the proper modeling of deformation and stresses. As stresses can exceed the limit when neglected, stress constraints are needed in the synthesis of compliant mechanisms. Both nonlinear finite-element analysis as well as the consideration of stress constraints significantly increase computational cost of topology optimization. Multiresolution topology optimization, which employs different levels of discretization for the finite-element analysis and the representation of the material distribution, allows an important reduction of computational effort. A multiresolution topology optimization methodology is proposed integrating stress constraints based on nonlinear finite-element analysis for path-generation mechanisms. Two objective formulations are used to motivate and validate this methodology: maximum-displacement mechanisms and path-generation mechanisms. The formulation of the stress constraints and their sensitivities within nonlinear finite-element analysis and multiresolution topology optimization are explained. We introduce two academic benchmark examples to demonstrate the results for each of the objective formulations. To show the practical, large-scale application of this method, results for the compliant mechanism structure of a droop-nose morphing wing concept are shown. Full article
(This article belongs to the Special Issue Modeling, Design, and Optimization of Flexible Mechanical Systems)
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Open AccessFeature PaperArticle
Active Approaches to Vibration Absorption through Antiresonance Assignment: A Comparative Study
Appl. Sci. 2021, 11(3), 1091; https://doi.org/10.3390/app11031091 - 25 Jan 2021
Cited by 1 | Viewed by 410
Abstract
Vibration absorption is a core research topic in structural dynamics and the mechanics of machines, and antiresonance assignment is an effective solution to such a problem in the presence of harmonic excitation forces. Due to recent developments in the theory of feedback control [...] Read more.
Vibration absorption is a core research topic in structural dynamics and the mechanics of machines, and antiresonance assignment is an effective solution to such a problem in the presence of harmonic excitation forces. Due to recent developments in the theory of feedback control systems, the use of active control approaches to antiresonance assignment has been recently gaining more attention in the literature. Therefore, several methods exploiting state feedback or output feedback have been proposed in recent years. These techniques that just rely on servo-controlled actuators are becoming an interesting alternative to active approaches that emulate the well-known Tuned Mass Damper in an active (or semi-active) framework. This paper reviews and compares the most important approaches, with a greater focus on the methods exploiting the concept of control theory without adding new degrees of freedom in the system. The theoretical results, with the underlying theory, are discussed to highlight the key features of each assignment techniques. Several numerical examples where different techniques are applied and compared, also providing some analysis usually neglected in the literature, enrich the paper and demonstrate the key concepts. Full article
(This article belongs to the Special Issue Modeling, Design, and Optimization of Flexible Mechanical Systems)
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Open AccessArticle
Simulation Analysis and Experimental Verification of the Locking Torque of the Microgravity Platform of the Chinese Space Station
Appl. Sci. 2021, 11(1), 102; https://doi.org/10.3390/app11010102 - 24 Dec 2020
Viewed by 302
Abstract
The Microgravity Platform (MP) of the Chinese Space Station is locked and released by Lock-or-Release (L/R) mechanism on both sides. In order to ensure the safety and reliability of the MP under the vibration environment during the rocket launch, the L/R mechanism must [...] Read more.
The Microgravity Platform (MP) of the Chinese Space Station is locked and released by Lock-or-Release (L/R) mechanism on both sides. In order to ensure the safety and reliability of the MP under the vibration environment during the rocket launch, the L/R mechanism must output the appropriate locking torque value. Based on the structural characteristics of the Scientific Experiment Cabinet (SEC), this paper proposes a method of evaluating locking torque by combining theory with experiment, and the relationship between locking force and locking torque of L/R mechanism is proved that the locking force on both sides can reach 2000 N at 25 Nm driving torque. Finally, it is verified by vibration test that the locking torque obtained by this method can effectively guarantee the safety and reliability of the MP under vibration environment. Full article
(This article belongs to the Special Issue Modeling, Design, and Optimization of Flexible Mechanical Systems)
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Open AccessArticle
Experimental and Numerical Investigation of Solar Panels Deployment with Tape Spring Hinges Having Nonlinear Hysteresis with Friction Compensation
Appl. Sci. 2020, 10(21), 7902; https://doi.org/10.3390/app10217902 - 07 Nov 2020
Viewed by 534
Abstract
In this work, experimental and numerical investigation on the deployment of solar panels with tape spring (TS) hinges showing complex nonlinear hysteresis behavior caused by the snap-through buckling was conducted. Subsequently, it was verified by comparing simulation results by multi-body dynamics (MBD) analysis [...] Read more.
In this work, experimental and numerical investigation on the deployment of solar panels with tape spring (TS) hinges showing complex nonlinear hysteresis behavior caused by the snap-through buckling was conducted. Subsequently, it was verified by comparing simulation results by multi-body dynamics (MBD) analysis with test results on ground-based deployment testing considering gravity compensation, termed zero-gravity (Zero-G) device. It has been difficult to predict the folding and unfolding behavior of TS hinges because their moment–rotation relationship showed a nonlinear hysteresis behavior. To realize this attribute, an algorithm that checks the sign of angular velocity of the revolute joints was used to distinguish folding from unfolding. The nonlinear hysteresis was implemented in terms of two path-dependent nonlinear moment–rotation curves with the aid of the expression function (a kind of user subroutine) in MBD software RecurDyn. Finally, it was found that the results of the deployment analysis were in excellent agreement with those of the test when the friction torques of the revolute joints were properly identified by an inverse analysis with the test frames, thus validating the MBD model. Full article
(This article belongs to the Special Issue Modeling, Design, and Optimization of Flexible Mechanical Systems)
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Open AccessArticle
Minimization of the Energy Consumption in Industrial Robots through Regenerative Drives and Optimally Designed Compliant Elements
Appl. Sci. 2020, 10(21), 7475; https://doi.org/10.3390/app10217475 - 24 Oct 2020
Viewed by 406
Abstract
This paper describes a method for reducing the energy consumption of industrial robots and electrically actuated mechanisms performing cyclic tasks. The energy required by the system is reduced by outfitting it with additional devices able to store and recuperate energy, namely, compliant elements [...] Read more.
This paper describes a method for reducing the energy consumption of industrial robots and electrically actuated mechanisms performing cyclic tasks. The energy required by the system is reduced by outfitting it with additional devices able to store and recuperate energy, namely, compliant elements coupled in parallel with axles and regenerative motor drives. Starting from the electromechanical model of the modified system moving following a predefined periodic path, the relationship between the electrical energy and the stiffness and preload of the compliant elements is analyzed. The conditions for the compliant elements to be optimal are analytically derived. It is demonstrated that under these conditions the compliant elements are always beneficial for reducing the energy consumption. The effectiveness of the design method is verified by applying it to two test cases: a five-bar mechanism and a SCARA robot. The numerical validations show that the system energy consumption can be reduced up to the 77.8% while performing a high-speed, standard, not-optimized trajectory. Full article
(This article belongs to the Special Issue Modeling, Design, and Optimization of Flexible Mechanical Systems)
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Open AccessArticle
Iterative Coordinate Reduction Algorithm of Flexible Multibody Dynamics Using a Posteriori Eigenvalue Error Estimation
Appl. Sci. 2020, 10(20), 7143; https://doi.org/10.3390/app10207143 - 14 Oct 2020
Viewed by 409
Abstract
Coordinate reduction has been widely used for efficient simulation of flexible multibody dynamics. To achieve the reduction of flexible bodies with reasonable accuracy, the appropriate number of dominant modes used for the reduction process must be selected. To handle this issue, an iterative [...] Read more.
Coordinate reduction has been widely used for efficient simulation of flexible multibody dynamics. To achieve the reduction of flexible bodies with reasonable accuracy, the appropriate number of dominant modes used for the reduction process must be selected. To handle this issue, an iterative coordinate reduction strategy is introduced. In the iteration step, more dominant modes of flexible bodies are selected than the ones in the previous step. Among the various methods, the conventional frequency cut-off rule is here considered. As a stop criterion, a novel a posteriori error estimator that can evaluate the relative eigenvalue error between full and reduced flexible bodies is proposed. Through the estimated relative eigenvalue error obtained, the number of dominant modes is automatically selected to satisfy the error tolerance up to the desired mode range. The applicability to the automation process is verified through numerical examples. It is also evaluated that efficient and accurate flexible multibody dynamics simulation is available with the reduced flexible body, generated by the proposed algorithm. Full article
(This article belongs to the Special Issue Modeling, Design, and Optimization of Flexible Mechanical Systems)
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Open AccessArticle
Dynamic Behaviour of a Conveyor Belt Considering Non-Uniform Bulk Material Distribution for Speed Control
Appl. Sci. 2020, 10(13), 4436; https://doi.org/10.3390/app10134436 - 27 Jun 2020
Cited by 1 | Viewed by 615
Abstract
For the conveyor belt, variable material flow influences the energy efficiency of the speed control technology significantly. The fluctuation of material flow on the conveyor belt will lead to the detrimental vibrations on both the belt and the conveyor while the conveyor works [...] Read more.
For the conveyor belt, variable material flow influences the energy efficiency of the speed control technology significantly. The fluctuation of material flow on the conveyor belt will lead to the detrimental vibrations on both the belt and the conveyor while the conveyor works at certain speeds. In order to improve the model inaccuracy caused by the uniform bulk material flow assumption in the current conveyor belt model, the paper establishes a high-precision dynamic model that can consider speed control of a conveyor belt under non-uniform bulk material transportation. In this dynamic model, a non-uniform bulk material distribution model is firstly proposed based on laser scanning technology. Then, a high-precision longitudinal dynamic model is proposed to investigate the dynamic behavior of a belt conveyor. Considering the micro-units of actual load on a conveyor belt, it can well describe the transient state of the conveyor belt. These models can be used to determine the optimal speed for safety and energy conservation in operation. Experimental results are used to validate the proposed dynamic model for analyzing belt mechanical behavior under non-uniform bulk material distribution on the belt. The results show that the proposed models can be used for optimizing the operating procedures of belt conveyor systems. Full article
(This article belongs to the Special Issue Modeling, Design, and Optimization of Flexible Mechanical Systems)
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Open AccessArticle
SiMFlex Micromanipulation Cell with Modular Structure
Appl. Sci. 2020, 10(8), 2861; https://doi.org/10.3390/app10082861 - 20 Apr 2020
Cited by 1 | Viewed by 731
Abstract
During recent years, there has been a trend towards the miniaturization of the products and of the tools necessary in the industrial processes, including those for micromanipulation. For micromanipulation, the best devices are microgrippers built such as the compliant mechanisms. In this paper, [...] Read more.
During recent years, there has been a trend towards the miniaturization of the products and of the tools necessary in the industrial processes, including those for micromanipulation. For micromanipulation, the best devices are microgrippers built such as the compliant mechanisms. In this paper, a modular structure for a micromanipulation cell is proposed. The cell has three main modules: a base platform for the working area, a micro-positioning system, and a micromanipulation system. Each module has different design variants which can be combined for specific applications, the FE (finite elements). The analysis and experimental results validate the prototype proposed for this study. In the end, an application of the SiMFlex manipulation cell for an optical microscope is proposed. Full article
(This article belongs to the Special Issue Modeling, Design, and Optimization of Flexible Mechanical Systems)
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Open AccessArticle
Kinematic Modelling and Experimental Validation of a Foldable Pneumatic Soft Manipulator
Appl. Sci. 2020, 10(4), 1447; https://doi.org/10.3390/app10041447 - 20 Feb 2020
Cited by 1 | Viewed by 677
Abstract
A foldable pneumatic soft manipulator, which has the foldability to switch between a contraction state and an expanded state, is proposed in this investigation. The soft manipulator is a structure composed of pneumatic actuators and inflatable straight arms. The directional movement is driven [...] Read more.
A foldable pneumatic soft manipulator, which has the foldability to switch between a contraction state and an expanded state, is proposed in this investigation. The soft manipulator is a structure composed of pneumatic actuators and inflatable straight arms. The directional movement is driven by the pneumatic actuators and the foldability is realized by the inflatable straight arms. Based on this design, the kinematic model of one foldable pneumatic module is developed and presented. The shape deformation and workspace of the pneumatic module is numerically calculated and analyzed. To validate the correctness of the kinematic model, the prototype of one foldable pneumatic module, as well as the relevant pneumatic control system, is designed and developed. The repeatability of the pneumatic module and the model prediction accuracy are tested and validated by the experiment. Full article
(This article belongs to the Special Issue Modeling, Design, and Optimization of Flexible Mechanical Systems)
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Open AccessArticle
Dynamic Analysis of Spatial Truss Structures Including Sliding Joint Based on the Geometrically Exact Beam Theory and Isogeometric Analysis
Appl. Sci. 2020, 10(4), 1231; https://doi.org/10.3390/app10041231 - 12 Feb 2020
Cited by 1 | Viewed by 604
Abstract
With increasing of the size of spatial truss structures, the beam component will be subjected to the overall motion with large deformation. Based on the local frame approach and the geometrically exact beam theory, a beam finite element, which can effectively reduce the [...] Read more.
With increasing of the size of spatial truss structures, the beam component will be subjected to the overall motion with large deformation. Based on the local frame approach and the geometrically exact beam theory, a beam finite element, which can effectively reduce the rotational nonlinearity and is appropriate for finite motion and deformation issues, is developed. Dynamic equations are derived in the Lie group framework. To obtain the symmetric Jacobian matrix of internal forces, the linearization operation is conducted based on the previously converged configuration. The iteration matrix corresponding to the rotational parameters, including the Jacobian matrix of inertial and internal forces in the initial configuration, can be maintained in the simulation, which drastically improves the computational efficiency. Based on the Lagrangian multiplier method, the constraint equation and its Jacobian matrix of sliding joint are derived. Furthermore, the isogeometric analysis (IGA) based on the non-uniform rational B-splines (NURBS) basis functions, is adopted to interpolate the displacement and rotation fields separately. Finally, three dynamic numerical examples including a deployment dynamic analysis of spatial truss structure are conducted to verify the availability and the applicability of the proposed formulation. Full article
(This article belongs to the Special Issue Modeling, Design, and Optimization of Flexible Mechanical Systems)
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Review

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Open AccessReview
Development of Everting Tubular Net Structures Using Simulation for Growing Structures
Appl. Sci. 2020, 10(18), 6466; https://doi.org/10.3390/app10186466 - 17 Sep 2020
Viewed by 626
Abstract
Many living beings show the ability and necessity to develop invertible, tubular structures to enable additional functions temporarily. The biological archetypes always demonstrate a high change of volume of the structure between an inactive and active state. This makes the principle interesting for [...] Read more.
Many living beings show the ability and necessity to develop invertible, tubular structures to enable additional functions temporarily. The biological archetypes always demonstrate a high change of volume of the structure between an inactive and active state. This makes the principle interesting for many technical applications, where a certain geometry or an additional volume has to be generated situationally for a task and can only be accepted temporarily, for example, in minimally invasive robotics. A possibility was sought to transfer the archetype into the technical context and to evaluate geometric-constructive dependencies based on an inversion of the structure. The result is a practicable design for repeatedly invertible net structures, which can be used for products with temporary additional functions and volumes. Full article
(This article belongs to the Special Issue Modeling, Design, and Optimization of Flexible Mechanical Systems)
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