Multiresponse Optimization of Linkage Parameters of a Compliant Mechanism Using Hybrid Genetic Algorithm-Based Swarm Intelligence

This research focuses on the synthesis of linkage parameters for a bistable compliant system (BSCS) to be widely implemented within space applications. Initially, BSCS was theoretically modeled as a crank-slider mechanism, utilizing pseudo-rigid-body model (PRBM) on stiffness coefficient (v), with a maximum vertical footprint (bmax) for enhancing vibration characteristics. Correlations for mechanism linkage parameters (MLPs) and responses (v and bmax) were set up by utilizing analysis of variance for response surface (RSM) technique. RSM evaluated the impact of MLPs at individual/interacting levels on responses. Consequently, a hybrid genetic algorithm-based particle swarm/flock optimization (GA-PSO) technique was employed and optimized at multiple levels for assessing ideal MLP combinations, in order to minimize characteristics (10% v + 90% of bmax). Finally, GA-PSO estimated the most appropriate Pareto-frontal optimum solutions (PFOS) from nondominance set and crowd/flocking space approaches. The resulting PFOS from validation trials demonstrated significant improvement in responses. The adapted GA-PSO algorithm was executed with ease, extending the convergence period (through GA) and exhibiting a good diversity of objectives, allowing the development of large-scale statistics for all MLP permutations as optimal solutions. A vast set of optimal solutions can be used as a reference manual for mechanism developers.

TOWARDS THE DESIGN OF KRESLING TOWER ORIGAMI AS A COMPLIANT BUILDING BLOCK

In this paper, the use of the Kresling tower origami as a building block for compliant mechanism design is considered. Design tools to help building systems using this origami are introduced. First, a model which can describe the tower kinematics during its deployment is introduced. This model is exploited to link the origami pattern geometry to the main Kresling tower characteristics which include the position of stable configurations, the helical motion and the configuration of panels during the tower deployment. Second, a local modification of fold geometry is introduced to adjust the tower stiffness. This aims at modifying the actuation force without affecting the kinematics and consists in the removal of material on the fold line where constraints are concentrated during the folding. Experimental evaluation is conducted to verify the relevance of the proposed models and the impact of fold line modification. As a result, the design relationships derived from the model are precise enough for the synthesis, with a global relative mean error around 0.8% for the prediction of the helical motion, and 3.1% for the assessment of stable configurations. The capacity to significantly modify the actuation force thanks to the fold line modification is also observed with a reduction of about 73% of the maximal force to switch between two stable configurations.

Optimization Parameter for Micro-Gripper Based on Triple-Stair Compliant Mechanism Using GTs-TOPSIS

In manipulating the assembly of micro-components, the symmetrical microgripper mechanism often causes destruction, damaging the micro-components during manipulation. The reason is due to the phenomenon of non-uniform clamping force output of the clamp. From this disadvantage, a new asymmetric microgripper structure is proposed with stable output clamping force. The asymmetric microgripper structure will have a smaller output displacement than the symmetric structure. Therefore, to increase the output displacement gain, a flexible hinge with a triple stair half bridge-style mechanism is adopted to design the amplifier of the asymmetrical microgripper. The finite element method is applied to analyze the displacement and stress. The optimization process is performed based on the geometric parametric properties of the structure. Using the technology for order preference by similarity to ideal solution (TOPSIS) based on the grey relationship analysis (GRA) obtained the maximal displacement output and minimal stress. The results show that the maximum output displacement is 5,818 mm, stress after analysis is 2,432MPa. The test is conducted to verify the optimal results and the effectiveness of the optimization method. Finally, experimental experiments were performed, with a 4.8% difference from the FEA results. The results from the experimental test verify that the microgripper's maximum displacement amplification ratio is approximately 58.2 times.

Axially rigid steerable needle with compliant active tip control

Steerable instruments allow for precise access to deeply-seated targets while sparing sensitive tissues and avoiding anatomical structures. In this study we present a novel omnidirectional steerable instrument for prostate high-dose-rate (HDR) brachytherapy (BT). The instrument utilizes a needle with internal compliant mechanism, which enables distal tip steering through proximal instrument bending while retaining high axial and flexural rigidity. Finite element analysis evaluated the design and the prototype was validated in experiments involving tissue simulants and ex-vivo bovine tissue. Ultrasound (US) images were used to provide visualization and shape-reconstruction of the instrument during the insertions. In the experiments lateral tip steering up to 20 mm was found. Manually controlled active needle tip steering in inhomogeneous tissue simulants and ex-vivo tissue resulted in mean targeting errors of 1.4 mm and 2 mm in 3D position, respectively. The experiments show that steering response of the instrument is history-independent. The results indicate that the endpoint accuracy of the steerable instrument is similar to that of the conventional rigid HDR BT needle while adding the ability to steer along curved paths. Due to the design of the steerable needle sufficient axial and flexural rigidity is preserved to enable puncturing and path control within various heterogeneous tissues. The developed instrument has the potential to overcome problems currently unavoidable with conventional instruments, such as pubic arch interference in HDR BT, without major changes to the clinical workflow.

Accuracy and precision: A new viewon kinematic assessment of solid-state hinges and compliant mechanisms

Compliant mechanisms are alternatives to conventional mechanisms which exploit elastic strain to produce desired deformations instead of using moveable parts. They are designed for a kinematic task (providing desired deformations) but do not possess a kinematics in the strict sense. This leads to difficulties while assessing the quality of a compliant mechanism’s design. The kinematics of a compliant mechanism can be seen as a fuzzy property. There is no unique kinematics, since every deformation need a particular force system to act; however, certain deformations are easier to obtain than others. A parallel can be made with measurement theory: the measured value of a quantity is not unique, but exists as statistic distribution of measures. A representative measure of this distribution can be chosen to evaluate how far the measures divert from a reference value. Based on this analogy, the concept of accuracy and precision of compliant systems are introduced and discussed in this paper. A quantitative determination of these qualities based on the eigenvalue analysis of the hinge’s stiffness is proposed. This new approach is capable of removing most of the ambiguities included in the state-of-the-art assessment criteria (usually based on the concepts of path deviation and parasitic motion).