Papers by Keyword: Compliant Mechanism

Abstract: This paper presents a design of the 1 degree-of-freedom (DOF) compliant mechanism to support rotation, which can be used as the compliant bearing in rotary motor. With the simple idea of replacing the traditional bearings with the compliant counterparts, the compliant motor built by the developed mechanism is capable of creating frictionless and repeatable rotations for precise applications. The compliant bearing is synthesized based on a specific connection of beam-type flexures; its stiffness characteristic is analytically determined in this paper. Finite element analysis (FEA) is then used to verify the analytical results. The correctness of the bearing design is demonstrated through the small deviation between the analytical and FEA methods. With the simple structure of this compliant mechanism, a low-cost flexure-based bearing can be achieved to support rotary motions in precision devices such as actuators, sensors, positioners, etc.

Abstract: This paper presents the development of a three degrees-of-freedom (DOF) compliant parallel mechanism (CPM) with spatial motions, i.e., two rotations about the X and Y axes and one translation along the Z axis (θX-θY-Z). Such CPM is synthesized by the improved beam-based structural optimization method. The obtained results suggest that the proposed CPM is able to produce totally decoupled motions illustrated by a diagonal stiffness/compliance matrix, a large workspace of ±22,5 degrees × ±22,5 degrees × ±9,6 mm, fast dynamic response with the first natural frequency of ~100 Hz and high stiffness ratios between actuating and non-actuating directions (with stiffness ratios of 6210 and 2706 for translations and rotations respectively). Finite element analysis (FEA) is employed to evaluate the actual performance of the synthesized CPM with Ti6Al4V material in order to verify the correctness of the synthesis method. The effectiveness of the improved beam-based structural method is demonstrated by the good agreement between the simulation and predicted data with the highest deviations are 8.8% and 6.7% for the stiffness and dynamic properties respectively. In addition, some comparisons are carried out to investigate the advantages as well as disadvantages of the proposed CPM and existing designs. The comparison results show that the 3-DOF CPM presented in this paper has many merits compared to its counterparts. It can be used in various applications, e.g., the micro/nano positioners and alignment systems in precision engineering field due to its good mechanical properties (high stiffness ratios and fast dynamic behavior), large work range and fully-decoupled motion characteristic.

Abstract: Electron beam melting (EBM) technology has been popularly used to fabricate flexible devices that performance is directly determined by the elastic deformation of thin beams/flexures. This paper presents the experimental investigation on the effective thickness which determines the mechanical properties of beam-based flexures built by EBM method and Ti6Al4V material. The findings show that the effective thickness of EBM-printed beams is different from the designed value regarding to the building direction. A coefficient factor is proposed to compensate this difference. The experimental results suggest that with EBM-printed flexures having large thickness of ≥ 0.7 mm, the coefficient factors become consistent.

Abstract: A Compliant XY micropositioning stage is purported for situating a material sample in nanoindentation tester process. This paper aims to develop, analyze and optimize a XY compliant micropositioning stage. The working stroke of proposed XY stage is amplified by combining the four-lever and a bridge amplification mechanism. To enhance the performances of the stage, the main geometric parameters are optimized by an integration method of Taguchi method, response surface method (RSM) and genetic algorithm (GA). Firstly, static analysis and dynamic analysis are conducted by the finite element analysis in order to predict initial performances of the XY stage. Secondly, the number of experiments and the data are retrieved by combination of the finite element analysis-integrated Taguchi method. Thirdly, the effects of main design variables on the output response sensitivity are considered. Later on, mathematical model for the amplification ratio was established by the RSM. Finally, based on the mathematical equation, the GA is adopted to define the optimal design variables. The results of numerical validations are in a good agreement with the predicted results. The results depicted that the proposed hybrid approach ensures a high reliability for engineering optimization problems.

Abstract: The geometric nonlinearity resulting from large deformation of compliant members has continued to be an interesting research topic in nonlinear mechanics. In this study, two standard variational iteration algorithms, VIM-I and VIM-III are employed to investigate the large deformation of the continuum compliant beam under point load. The VIM is an efficient technique that bypasses the linearization process and proffers solutions to nonlinear problems. The horizontal and vertical displacements of the continuum compliant cantilever beam free end are expressed in explicit analytical forms. Numerical experiment and simulations were carried out to validate the efficacy and applicability of the semi-analytical method. The VIM-I was split into two; VIM-I(A) and VIM-I(B), with the difference being the initial approximations. The results from the VIM-I(A), VIM-I(B) and VIM-III algorithms were compared with the experimental and exact solution. The outcomes reveal that both algorithms correlated well with the analytical solution and experimental result.

Abstract: Flexure hinges have been used in many precision mechanisms where repeatable, friction free motion and high precision are required. Many kinds of flexure profiles have been proposed during the past decade. This paper presents a new type of flexure hinge which combines circular longitudinal axis beams to form hollow joint. This novel design will help to improve the range of motion, reduce stress level and increase the maximum load before yielding. Due to its special design, the cavity inside the hinge can also be filled with an elastomeric filler material to provide vibration damping. In order to synthesis this hinge, shape optimization integrating genetic algorithm and response surface methodology is used. The optimization procedure is programmed in MATLAB whereas finite element analysis in ANSYS is also embedded into the codes to enhance the calculation process. The new flexure hollow hinge is compared to the conventional straight-axis solid hinges (circular, elliptical and corner-filleted flexure hinges) in terms of stiffness, rotational precision and stress levels. It is also supposed that this new design would increase the precision of the mechanism due to reducing the parasitic motion. Finite element analysis in ANSYS is used to verify for the viability of the design before it can be fabricated and tested.

Abstract: Traditional bearings with one degree of freedom (1-DOF) translation are due to sliding between rigid bodies; however, the wear, backlash, and low precision are existing defects. For high-precision mechanism to overcome these limitations, a flexible bearing with 1-DOF translation in this paper is designed alternatively by the use of the concept of compliant mechanism because its motion replies on elastic elements. Besides, the fatigue strength, fracture, and crack are frequently appeared as mechanical failures due to high stress at the fixed end of flexible hinges. To reduce mechanical failures, experiments are conducted by an L₂₇ orthogonal array of the Taguchi multiple quality method to optimize design parameters, including an applied force and the length, width, thickness, and filleted radius of flexible hinges considering the stress concentration. The results demonstrate that the resulting stress of the new design flexible bearing is almost 99.7% smaller than that of the original design.

Abstract: The paper presents the model and design of a flexure-based precise 4 DOF degree of freedom positioning system for micro-positioning uses. The positioning system is featured with monolithic architecture, flexure-based joints and ultra-fine adjustment screws. The mathematical model for the output displacements of the positioning system has been verified by finite element analysis (FEA).

Abstract: According to the flexibility relationships of the 3-RRR compliant parallel micromotion platform along the X, Y direction and the rotation around the Z axis, using the Taguchi Design and Monte Carlo Simulation methods, considering the strong robustness of the flexibility in X direction and the existence of errors of the flexible hinge geometrical sizes, the flexibility iterative optimization for the compliance of the micromotion platform along the translation in Y-direction and the rotation around the Z axis are carried out respectively, the best geometry sizes of flexible hinge are find out, which provides a new solution of robust optimization design with multiple response problems of compliant mechanism consider uncertainty disturbance situation. Finally the correctness and validity of the method are verified with an example.

Abstract: Optimal robust design for multiple response problems is becoming more important for compliant mechanism. However, there are now still need effective methods for complex multiple response problems in the design process of compliant mechanism. In this paper, through the Response Surface Methodology (RSM), a novel optimal robust design method for the flexibility relationships of the 3-RRR compliant parallel micromotion platform along the X、Y direction and the rotation around the Z axis is proposed. Analysed the influence of different size parameters of flexible hinge to the compliant parallel micromotion platform different direction flexibility, the optimized complex multiple response variables of the compliant parallel micromotion platform and the best robust solutions are developed. And a real case study is used to demonstrate the implementation and potential applications of the proposed method for optimization design of compliant mechanism with considering complex multiple response problems.