Design Of Compliant Mechanisms Research Articles

Design of a stiffness-adjustable compliant linear-motion mechanism

A stiffness-adjustable compliant linear-motion mechanism (CLMM) is desired in practical applications. In this paper loads are applied at the secondary stage of a paired double parallelogram (DP-DP) to adjust stiffness, based on the analysis of a combination of parallelograms. Pre-loaded parallelograms and loading springs are utilized to solve the loading problem in practical applications, and the redundant degree of freedom (DOF) is restricted to a certain extent. Meanwhile, the parasitic motion of the primary stage is diminished by arranging the configuration symmetrically. Furthermore, a model, capable of predicting stiffness characteristics, is developed through an energy approach based on the relation between applied forces and internal forces, and a Lagrange multiplier is exploited to deal with the constraints. Finally, the analytical model is verified by finite element analysis (FEA) and experiments, and the errors caused by parasitic motion are corrected for this analytical model.

Design of Large-Displacement Compliant Mechanisms by Topology Optimization Incorporating Modified Additive Hyperelasticity Technique

This paper is focused on the topology design of compliant mechanisms undergoing large displacement (over 20% of the structural dimension). Based on the artificial spring model and the geometrically nonlinear finite element analysis, the optimization problem is formulated so as to maximize the output displacement under a given material volume constraint. A modified additive hyperelasticity technique is proposed to circumvent numerical instabilities that occurred in the low-density or intermediate-density elements during the optimization process. Compared to the previous method, the modified technique is very effective and can provide more accurate response analysis for the large-displacement compliant mechanism. The whole optimization process is carried out by the gradient-based mathematical programming method. Numerical examples of a force-inverting mechanism and a microgripping mechanism are presented. The obtained optimal solutions verify the applicability of the proposed numerical techniques and show the necessity of considering large displacement in the design problem.

Design and Development of Compliant Mechanisms Using Parameterization Technique

Design and development of compliant mechanism based systems with precision motion are the need of the hour in micro-precision industry. Compliant mechanisms coupled with the proper flexure hinge can provide excellent accuracy contrary to conventional rigid body mechanism. Various design methods are proposed to design a compliant mechanism such as structural optimization technique, Pseudo Rigid Body Model, Inverse Methods and Intuitive methods. Developing a manufacturable monolithic compliant mechanism is highly challenging. In this paper we have attempted a novel approach to design a compliant mechanism with circular based contemporary flexure hinge. The initial design of flexure hinge is designed intuitively and selection of appropriate geometrical parameters of the flexure hinges is another critical task in the design process. The developed hinges are parameterised using the general screening algorithm in ANSYS Workbench to obtain precise dimensions. The initial design of flexure hinge is designed as a curved beam which have fixed centre of rotation during execution. The method is implemented to design a four bar compliant mechanism and compared with the mathematical results. Scott-Russell straight line mechanism is also developed using this approach and verified its effectiveness. Dimensions of the developed hinges are also provided in the paper to enable future researchers to implement and improve the design.

Design of Compliant Mechanisms for New Age Industry Devices - A Topology Optimisation Approach

Design of Compliant Mechanisms for New Age Industry Devices - A Topology Optimisation Approach

Multi-material topology optimization for the design of compliant mechanisms using a level set method

Multi-material topology optimization for the design of compliant mechanisms using a level set method

Elasto-kinematic comparison of flexure hinges undergoing large displacement

The design of precision compliant mechanisms requires the assessment of the elasto-kinematic characteristics of the flexure hinges connecting bulky parts. Due to geometrical nonlinearities, a comprehensive analysis requires the functional properties to be evaluated within the feasible range of relative displacement. This investigation proposes the use of kinematic invariants to characterize the main features of a compliant mechanism. In particular, this paper offers the comparison of five common flexure hinges in terms of the relative motion kinematic invariants. By using the dynamic spline formulation, for each hinge typology, a flexible multibody model is developed to obtain the fixed and moving centrodes and the diameter of the inflection circle of the relative motion. In order to fully characterize the elasto-kinematic behaviour, the simulative models are also used to compute the equivalent stiffness as a function of the rotation angle. The results show that the differences among the various types of hinges is relevant in terms of both kinematic and compliance characteristics. The findings and the methodology herein outlined are new tools for the optimal design and synthesis of flexure joints.

Design of monolithic compliant mechanisms with beam elements of distributed stiffness

Lightweight structures made of fiber‐reinforced composites exhibit a considerable application potential for designing fully compliant monolithic mechanisms. The substitution of classical joints by flexible elements exhibits benefits in assembling these linkages. The inherently high ability for function integration and the specifically adjustable compliances offers the possibility to transmit motions only by structural deformations. Especially flexible beam elements with distributed stiffness enhance the synthesis of compliant mechanisms. With the predefined beam deflection with constant curvature, the adjusted material properties are directly defined without solving the Bernoulli – ordinary differential equation. The generalized synthesis of bistable monolithic compliant mechanisms deals with a three body system connected by three flexible elements by solving a two pose tasks.

Design, modeling, analysis and testing of a novel piezo-actuated XY compliant mechanism for large workspace nano-positioning

In this paper, a new piezo-actuated XY parallel compliant mechanism for large workspace nano-positioning with decoupled motions is developed by incorporating a novel Z-shaped flexure hinge (ZFH)-based mechanism into the mirror-symmetrically distributed structure. The bridge-type mechanism and two-stage leverage mechanisms serve as preliminary displacement amplifiers, while further amplification with motion transfer and decoupled output motions are achieved by means of the ZFH mechanism. Based on finite element theory, a high-precision analytical model of the XY compliant mechanism is established by considering all the connecting linkages as flexible components. Through the improved differential evolution algorithm, the optimized compliant mechanism is capable of performing millimeter-scale workspace nano-positioning with decoupled motions. In addition, the input displacement unbalance, resulting from the lateral force which has potential to damage the piezoelectric actuators, is markedly lowered to a negligible value. The performance of the fabricated compliant mechanism with optimized parameters is investigated to well agree with both the analytical model and ANSYS simulation. In addition, based on the inverse kinematics derived from the model and experimental results, different elliptical vibration trajectories are accurately acquired.

Synthesis of auxetic structures using optimization of compliant mechanisms and a micropolar material model

Aim of this work is the synthesis of auxetic structures using a topology optimization approach for micropolar (or Cosserat) materials. A distributed compliant mechanism design problem is formulated, adopting a SIMP---like model to approximate the constitutive parameters of 2D micropolar bodies. The robustness of the proposed approach is assessed through numerical examples concerning the optimal design of structures that can expand perpendicularly to an applied tensile stress. The influence of the material characteristic length on the optimal layouts is investigated. Depending on the inherent flexural stiffness of micropolar solids, truss---like solutions typical of Cauchy solids are replaced by curved beam---like material distributions. No homogenization technique is implemented, since the proposed design approach applies to elements made of microstructured material with prescribed properties and not to the material itself.

Pseudo-rigid-body models for circular beams under combined tip loads

Circular beams can offer potential advantages to designers of compliant mechanisms and provide useful alternatives to other types of compliant elements. However, they pose unique challenges due to lack of effective models for predicting deformation upon loading. In this work, the kinematic and stiffness properties of circular beams with uniform cross sections subjected to combined force and moment loads are represented using pseudo-rigid-body models. The pseudo-rigid-body models serve as numerical approximations for easy derivation of mechanism equations, and also enable quick solutions using multi-body software packages. The models are derived by comparisons against beam theory, and the values of the parameters are presented in the form of fitting functions for a large range of arc angles. The validity and applicability of these models in analysis are demonstrated with the example of a micro-force sensor. Their use in design is demonstrated with the case of developing flexure mechanisms for microspines in grasping applications, with comparisons against Finite Element Analysis to prove their accuracy and speed. The PRB models can serve as tools facilitating design of compliant mechanisms with circular beams.

A new method for designing a compliant mechanism based displacement amplifier

Advancement of precision industries, displacement amplifying device is essential to produce precise and long range of motion for micro-actuator. Compliant mechanism based displacement amplifier (DA) is more appropriate to attain high precision motion. Compliant mechanism utilizes elastic nature of material to achieve required motion. In this research paper, compliant mechanism design is developed using topology optimization. The output of the topologically optimized design is impossible to fabricate as it is due to the presence of senseless regions. Hence, this optimized design is considered as a primary design of compliant mechanism which provides the configuration of kinematic linkages and also provides the details of the geometrical locations of the flexure hinges. Selection of appropriate geometrical parameters of the flexure hinges is another critical task in the design process and parameterization technique is used to determine flexure hinge parameters. Structural performance of mechanical amplifier confirmed using finite element method (FEM).

Experimental validation of the kinematic design of 3-PRS compliant parallel mechanisms

In this paper, a procedure for the kinematic design of a 3-PRS compliant parallel manipulator of 3 degree of freedom is proposed. First, under the assumption of small displacements, the solid body kinematics of the 3-PRS has been studied, performing a comprehensive analysis of the inverse and forward kinematic problem, and calculating the rotations that the revolute and spherical flexure joints must perform. Then, after defining some design requirements and therefore the necessary displacements to fulfill, a design process based on the finite element calculations has been stablished, giving the necessary guidelines to reach the optimal solution on a 3-PRS compliant mechanism. Also, a prototype has been tested, using a coordinate measuring machine to verify its dimensions and the resulting displacements in the end effector and the actuated joints. Finally, those measurements have been compared with the FEM and the rigid body kinematics predictions, contrasting the validity of those two modelling approaches for the kinematic design of compliant mechanisms.

DAS-2D: a concept design tool for compliant mechanisms

Abstract. Compliant mechanisms utilize the deformation of the elastic members to achieve the desired motion. Currently, design and analysis of compliant mechanisms rely on several commercial dynamics and finite element simulation tools. However, these tools do not implement the most recently developed theories in compliant mechanism research. In this article, we present DAS-2D (Design, Analysis and Synthesis), a conceptual design tool which integrates the recently developed pseudo-rigid-body models and kinetostatic analysis/synthesis theories for compliant mechanisms. Coded in Matlab, the software features a kinematic solver for general rigid-body mechanisms, a kinetostatic solver for compliant mechanisms and a fully interactive graphical user interface. The implementation details of all modules of the program are presented and demonstrated with four different case studies. This tool can be beneficial to classroom teaching as well as engineering practices in design of compliant mechanisms.

Design and formal verification of a cloud compliant secure logging mechanism

Security concerns are still retarding cloud adoption. While the research community work on clearing these concerns, an optimistic fair cloud compliant logging scheme may ease the cloud to spread. This study proposes a secure logging mechanism. The mechanism employs an online bulletin board as a public write-only storage for the log records. The bulletin board also acts as a trusted third party during conflict resolution. The secure logging protocol describes how the log records are distributed to the stakeholders. The protocol's security is verified with model checking tools and no security threats could be found.

Dynamic performance of dierent knee mechanisms with compliant joints

Loss of lower extremities has been one of the main problems in human life. Although most of the available knee devices are aesthetically acceptable, there is a necessity for lighter and more compact mechanisms, especially for younger amputees. This problem can be solved by the combining compliant mechanism design with traditional mechanism design methods. In this study, one group of the prosthetics that is known as the compliant knee mechanisms" is evaluated. At rst, the di erent knee mechanisms, such as fourand six-bar knee linkages are investigated to calculate the values of the control moments (actuator torque). Then, the suitable location (where the actuator torque is to be exerted) is determined to reduce the knee control moment. Finally, the compliant joints are employed to provide the improved designs. Furthermore, an optimization method is employed to determine the optimum values of sti ness instead of using an experimental technique. The obtained results show that use of the compliant joints in the knee mechanisms reduces the values of the control moments, signi cantly. In fact, the compliant members decrease the peak torques during the stance phase. Therefore, by applying a compliant joint, a higher energy eciency and lighter knee mechanism can be achieved for ambulation.

Design, modeling and test of a novel compliant orthogonal displacement amplification mechanism for the compact micro-grasping system

In the compact micro-grasping system, the combination of precisely orthogonal movement transformation, displacement amplification and simple structure is important. The typical solution of the combination issue requires bidirectional symmetric input forces/displacements. However, under a certain driving condition, numerous actuators used in micro-manipulation only supply unidirectional input froce/displacement for the driven mechanism, which makes the typical solution infeasible. In this study, a novel compliant orthogonal displacement amplification mechanism (DAM) is proposed to solve the combination issue for numerous actuators used in micro-grasping. The proposed mechanism is a triangulation amplification-based mechanism with undetermined structural parameters. The number of the undetermined parameters and the solution principle are analyzed. The design process is presented. Finite element analysis (FEA) is used to verify the design method. The FEA results show that, for the design examples, the errors evaluating the orthogonal movement transformation are smaller than 0.56ź% and 0.15 % respectively, and the displacement amplification ratios are larger than 4.6. The orthogonal displacement amplification is realized. A precise model of the displacement amplification ratio is derived. The dynamic performances of the proposed orthogonal DAM are modeled and FEA verified. Furthermore, a microgripper utilizing the proposed mechanism is presented. The performances of the gripper, including the displacement amplification and the parallel movement of the jaws, are verified by FEA and experiments.

Topology optimization of 3D self-supporting structures for additive manufacturing

The potential of topology optimization to amplify the benefits of additive manufacturing (AM), by fully exploiting the vast design space that AM allows, is widely recognized. However, existing topology optimization approaches do not consider AM-specific limitations during the design process, resulting in designs that are not self-supporting. This leads to additional effort and costs in post-processing and use of sacrificial support structures. To overcome this difficulty, this paper presents a topology optimization formulation that includes a simplified AM fabrication model implemented as a layerwise filtering procedure. Unprintable geometries are effectively excluded from the design space, resulting in fully self-supporting optimized designs. The procedure is demonstrated on numerical examples involving compliance minimization, eigenfrequency maximization and compliant mechanism design. Despite the applied restrictions, in suitable orientations fully printable AM-restrained designs matched the performance of reference designs obtained by conventional topology optimization.

Efficient Piezoelectric Energy Harvesters Utilizing (001) Textured Bimorph PZT Films on Flexible Metal Foils

Extracting energy from low vibration frequencies (<10 Hz) using piezoelectric energy harvester promises continuous self‐powering for sensors and wearables. The piezoelectric compliant mechanism (PCM) design provides a significantly higher efficiency by fostering a uniform strain for its 1st mode shape, and so is interesting for this application. In this paper, a PCM energy harvester with bimorph Pb(Zr,Ti)O3 (PZT) films on Ni foil deposited by rf magnetron sputtering is shown to have high efficiency and large power for low frequency mechanical vibration. In particular, {001} textured PZT films are deposited on both sides of polished Ni foils with (100) oriented LaNiO3 seed layers on HfO2 buffer layers. The performance of PCM with an active area of 5.2 cm2 is explored for various excitation accelerations (0.02–0.16 g [g = 9.8 m s−2]) around 6 Hz. The PCM device provides a power level of 3.9 mW cm−2 g2 and 65% mode shape efficiencies.

Pseudorigid-Body Models of Compliant DNA Origami Mechanisms

In this paper, we introduce a strategy for the design and computational analysis of compliant DNA origami mechanisms (CDOMs), which are compliant nanomechanisms fabricated via DNA origami self-assembly. The rigid, compliant, and flexible parts are constructed by bundles of many double-stranded DNA (dsDNA) helices, bundles of a few dsDNA helices or a single dsDNA helix, and single-stranded DNA (ssDNA) strands, respectively. Similar to its macroscopic counterparts, a CDOM generates its motion via deformation of at least one structural member. During the motion, strain energy is stored and released in the compliant components. Therefore, these CDOMs have the advantage of suppressing thermal fluctuations due to the internal mechanical energy barrier for motion. Here, we show that classic pseudorigid-body (PRB) models for compliant mechanism are successfully employed to the analysis of these DNA origami nanomechanisms and can serve to guide the design and analysis method. An example of compliant joint and a bistable four-bar CDOM fabricated with DNA origami are presented.

Analysis and design of an underactuated compliant five-bar mechanism

Generally, the pseudo-rigid-body model of compliant mechanisms is single degree-of-freedom in the literature. In order to obtain more flexibility, compliant mechanisms can also be synthesized from multi degree-of-freedom pseudo-rigid-body models. In this study, analysis and design procedures for such a compliant five-bar mechanism are presented with underactuation. Analysis is performed with different loading scenarios. An approximate method for dead center estimation is introduced. Some results are verified by using finite element analysis. A generalized design procedure for the mechanism is proposed. An advantage of underactuation over constrained mechanisms is presented with an example.