An analytical method for calculating the natural frequencies of spatial compliant mechanisms

Compliant mechanisms are becoming increasingly important in both research and industry. The design and the static analysis of such mechanisms has made much progress in recent years, yet comparatively little research has been done on their dynamic behaviour. The aim of this paper is to advance the dynamic analysis of spatial compliant mechanisms by pursuing the calculation of their natural frequencies. So far, their determination is only possible with time-consuming 3D-FEM simulations or via pseudo-rigid-body models and Lagrangian equations. An analytical method is developed to simplify and accelerate the calculation of the natural frequencies of compliant mechanisms. The method is integrated into an algorithm on which a graphical user interface is developed to allow the design and calculation of the system in the most time efficient and intuitive way. The results are verified by 3D-FEM simulations and validated through an experiment. The evaluation shows good agreement with the reference models. The results of this paper allow a reliable and efficient calculation of natural frequencies and serve to facilitate further work regarding the dynamic analysis of compliant mechanisms

Analysis of planar compliant mechanisms based on non-linear analytical modeling including shear and lateral contraction

Compliant mechanisms are commonly used in precision engineering while analyzing their deflection is particularly challenging. Often, FEM simulations are chosen in an iterative process. Analytical approaches that consider pure bending, shear or other effects are usually limited to the mechanism as a system. However, certain configurations comprise compliant elements with different aspect ratios. The aim of this paper is to integrate the theories of shear and lateral contraction into a unified form with the existing theory of bending for large deflections and make them applicable individually for specific sections of continuous compliant mechanisms. Recommendations are made as to when which theory should be used. Building on that, a comprehensive tool for analyzing compliant mechanisms developed in Python is introduced. The tool offers the possibility to create arbitrary compliant mechanisms including branched links and various boundary conditions. A tool for parametric studies allows to optimize the given geometry for realizing a specific motion task. Further, FEM and measurement results correlate well with the application results. The presented user interface can be beneficial for the accelerated analysis and synthesis of compliant mechanisms

On the Mechanical Compliance of Technical Systems

In the safe physical human-machine interaction the compliance of technical systems is an elementary requirement. The physical compliance of technical systems can be provided either by control functions implementation and/or intrinsic by structural configuration and material properties optimization. The latter is advantageous because of higher reliability as well as general simplicity of the design and production technologies. In the paper we focus on mechanical systems with intrinsic mechanical compliance. In general the deformability of structures is primarly characterised by their stiffness. Compliant mechanisms are mechanisms, whose functionality is based on its deformability. The goal of each engineer is by the design of mechanisms the setting of compliance depending upon the purpose of its application. It should be considered, that the compliance is dependent on a variety of parameters. The optimal design of these mechanisms can be realized only with precise knowledge of the influence parameters and possible types of compliance

Mathematical synthesis of compliant mechanism as cochlear implant

Cochlear implants can be successfully used to reduce the inner ear profound deafness. The implant is inserted into the inner ear by the surgeon’s hand. Because the cochlea has a spiral-like structure (cochlear duct), the insertion of the implant is often difficult, furthermore the basilar membrane could be easily damaged. One of the aims of our investigation is to develop a mathematical model based an synthesis method for implants with hydraulic actuation. This hydraulic actuation, which is integrated in the implant, facilitates the insertion of the implant structure to the shape of cochlear duct. Thus, the implant can follow the spiral-shaped cochlear duct without damaging the sensitive tissue of the basilar membrane. Some examples for hydraulic actuated cochlear implants based on compliant mechanisms technology are presented in this paper

Modeling and Design of Flexure Hinge-Based Compliant Mechanisms

A compliant mechanism gains its mobility fully or partially from the compliance of its elastically deformable parts rather than from conventional joints. Due to many advantages, in particular the smooth and repeatable motion, monolithic mechanisms with notch flexure hinges are state of the art in numerous precision engineering applications with required positioning accuracies in the low micrometer range. However, the deformation and especially motion behavior are complex and depend on the notch geometry. This complicates both the accurate modeling and purposeful design. Therefore, the chapter provides a survey of different methods for the general and simplified modeling of the elasto-kinematic properties of flexure hinges and compliant mechanisms for four hinge contours. Based on non-linear analytical calculations and FEM simulations, several guidelines like design graphs, design equations, design tools or a geometric scaling approach are presented. The obtained results are analytically and simulatively verified and show a good correlation. Using the example of a path-generating mechanism, it will be demonstrated that the suggested angle-based method for synthesizing a compliant mechanism with individually shaped hinges can be used to design high-precise and large-stroke compliant mechanisms. The approaches can be used for the accelerated synthesis of planar and spatial flexure hinge-based compliant mechanisms

Modeling of corner-filleted flexure hinges under various loads

Compliant mechanisms are widely applied in precision engineering, measurement technology and microtechnology, due to their potential for the reduction of mass and assembly effort through the integration of functions into fewer parts and an increasing motion repeatability through less backlash and wear, if designed appropriately. However, a challenge during the design process is the handling of the multitude of geometric parameters and the complex relations between loads, deformations and strains. Furthermore, some tasks such as the dimensioning by means of optimization or the modeling for a controller design require a high number of analysis calculations. From this arises the need for sufficient computational analysis models with low calculation time. Existing studies of analysis models are mostly based on selected load cases, which may limits their general validity. The scope of this article is the comparison of models for the analysis of corner-filleted flexure hinges under various loads, to determine their advantages, disadvantages and application fields. The underlying methods of the study can further be used to evaluate future models based on a broad selection of possible load cases

Theoretical considerations on 3D tensegrity joints for the use in manipulation systems

This paper presents a comprehensive analysis of a three-dimensional compliant tensegrity joint structure, examining its actuation, kinematics, and response to external loads. The study investigates a baseline configuration and two asymmetric variants of the joint. The relationship between the shape parameter and the parameters of the tensioned segments is derived, enabling the mathematical description of cable lengths for joint actuation. Geometric nonlinear static finite element simulations are performed to analyze the joint's response under various load conditions. The results reveal the joint's range of motion, the effect of different stiffness configurations, and its deformation behavior under external forces. The study highlights the asymmetric nature of the joint and its potential for targeted motion restriction. These findings advance the general understanding of the behavior of the considered tensegrity joint and provide valuable insights for their design and application in soft robotic systems

Konzeption eines Mechanotherapie-Systems zur Rehabilitation der Handfunktionalität für den Einsatz in der medizinischen Trainingstherapie

Die Hände des Menschen gelten als die am intensivsten eingesetzten Körperteile. Sie werden bei der Ausübung unterschiedlichster Tätigkeiten sowie zur Durchführung notwendiger alltäglicher Bedürfnisse eingesetzt. Im Gegensatz zu anderen Körperteilen sind die Hände, bedingt durch ihre exponierte Lage und den häufigen Gebrauch, einem höheren Verletzungsrisiko ausgesetzt. Durch die Selbstverständlichkeit, mit der der Mensch seine Hände einsetzt, wird deren Wichtigkeit erst nach einer Verletzung bzw. Krankheit bewusst. Bleibende Beeinträchtigungen beschränken sich nicht nur auf die körperliche Leistungsfähigkeit, sondern können auch seelische Auswirkungen auf den Patienten haben. Deshalb ist eine möglichst vollständige Rehabilitation der Hand anzustreben. Für die Handrehabilitation werden bisher technische Systeme eingesetzt, die nur eine sehr beschränkte Anzahl therapienotwendiger Bewegungsaufgaben übernehmen können. Motiviert durch diese Tatsachen wird ein Mechanotherapie-System konzeptioniert, welches fluidisch angetrieben und modular aufgebaut ist. Im ersten Schritt, wird sich auf die Konzeption für einen Finger beschränkt. Die gefundene Lösung ist aber auf die restlichen Langfinger übertragbar.The hands are regarded as the most intensively used parts of the human body. They are used to perform very different activities, and to carry out daily necessary needs. Due to their exposed location and the frequent use, hands have a high risk of injury. Through the naturalness with which humans use their hands, the major importance of them only becomes aware after the Hands are injured. Permanent damages are not limited to physical performance, but can also have psychological effects on the patient. Therefore, a preferably full rehabilitation of the hand is desirable. Only a very limited number of therapy necessary movement tasks can take on by nowadays used technical systems for hand rehabilitation. Motivated by these facts, a mechanotherapy-system is conceived, which is fluidly driven and modular. In this paper the conception of the mechanotherapy-system will be limited to one finger. However, the found solution is transferable to the remaining long fingers

An approach to compliant mechanisms with particular effects

This paper presents a classification of the deformation behaviour of compliant mechanisms to simplify their systematic construction. The described mechanisms with fluid drive exemplify special effects of presented systematic. Compared to conventional miniaturizable bending structures the mechanisms discussed in this paper have advantageous properties such as larger movement range, greater flexibility and less sensory effort. Typical applications of the discussed mechanisms are medicine technology and robotics for gripping or manipulating tasks