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Precision micro-manipulation tasks demand high-speed motion but low driving frequency for stick-slip actuators to achieve efficient operation and reduce friction wear. This paper presents a novel parasitic-type linear stick-slip actuator with macro fiber composites (MFCs). Unlike conventional piezoelectric actuators, the proposed stick-slip actuator has large single-step displacements and high motion consistency. It can realize high-speed motion under low driving frequency due to the superior properties of MFCs and the dual-drive method with a single driving foot. The actuator is devised based on a multi-beam-compliant driving mechanism, a pair of MFCs, and a slider. Also, an electromechanical dynamic model is proposed. A switching control strategy guarantees high positioning accuracy under large strokes. Finally, an experimental system is built. The single-step displacement can reach 367.7 μm with the dual-drive method. The actuator still has an effective stepping displacement of 63.4 μm even with a load of 2.1 kg. The maximal speed is 131.80 mm/s at a working frequency of 450 Hz. Thus, the actuator can realize mm/s motion with several Hertz driving voltages. Moreover, the maximum forward-reverse deviation only accounts for 1.31 % for a 2504 μm motion range, and the closed-loop motion resolution is 1.970 nm. Experiments verify the effectiveness and performance of the designed MFC stick-slip actuator. [Display omitted] • Macro-fiber-composite stick-slip actuator with large single-step displacements. • High forward-reverse motion consistency. • Electromechanical dynamic model for the MFC stick-slip actuator. • Nanoscale motion resolution using feedback control. [ABSTRACT FROM AUTHOR]

A novel monolithic compliant Lorentz-force-driven XY nanopositioning system (MCLNS) is designed, analyzed, and experimentally assessed with the aim of high-resolution positioning across a large workspace. A double-symmetric Lorentz-force actuator (DSLA) with the benefits of zero friction, high thrust, and large stroke is proposed to generate the actuation force. Correspondingly, a monolithic four-prismatic parallel compliant mechanism (4P-PCM) is exploited to transmit the actuation motion to the central platform and minimize the parasitic motion. The unique integration of four DSLAs and one 4P-PCM make the proposed MCLNS possess compact structure and stable performance. The characterization of the MCLNS is formulated by a specially established analytical model and validated by finite-element analysis simulation and experimental tests. Experimental studies show that the workspace of the MCLNS prototype is large than 0.87 × 0.87 mm2 and the positioning resolution of the MCLNS prototype is better than 9 nm. By means of a nonlinear forward proportional integral derivative control strategy, the maximum contouring error of the MCLNS is maintained within 2.7% while tracking a 1257 μ m s−1 circular trajectory. [ABSTRACT FROM AUTHOR]

This article aims at presenting a detailed and practical comparison between three designs of robotic soft fingers for industrial grippers. While the soft finger based on the fin ray effect (FRE) shown here has been proposed long ago, few works in the literature have studied its reliance on the presence of the crossbeams or its precision grasp performance compared to its power grasps. Aiming at addressing these gaps, two novel designs are proposed and compared to FRE fingers in this article. First, the three designs are presented. One of these fingers, named PacomeFlex, embeds changeable grasping modes by relying on two sets of kinematic structures with a bistable stopper design. Then, finite element analyses (FEA) are conducted to simulate power and precision grasps of the three fingers followed by the estimation of the grasp forces produced. These FEA are then used to train neural networks capable of predicting these grasp forces. Finally, the grasp strength and pullout resistance of the fingers are experimentally measured, and experimental results are shown to be in good accordance with the FEA and neural network models. As will also be shown, the PacomeFlex finger introduced in this work provides a noticeably higher performance level than all other fingers with respect to typical metrics in soft grasping. [ABSTRACT FROM AUTHOR]

Compliant mechanisms with multiple input loads and output ports are commonly applied in micro-electromechanical systems (MEMS), while compliant mechanisms under design-dependent pressure loadings (such as pneumatic or hydraulic) can generate smooth and compatible deformations. Combining these two types of problems, we propose the design problem of compliant mechanisms under multiple design-dependent loadings. To potentially improve the structural performances, fiber-reinforced composite materials are introduced, and multi-material topology optimization and material orientation optimization are considered simultaneously, which enables the materials to be anisotropic and heterogeneous. Since compliant mechanisms utilize elastic deformation to transmit input forces or displacements to output forces or displacements, anisotropic and heterogeneous material can increase the freedoms in displacement and force transmissions compared to conventional homogeneous isotropic material. The topology optimization is implemented via an extended moving iso-surface threshold (MIST) method for multi-material, in which a novel element-based searching scheme is employed for tracking multiple fluid–structure interfaces. The orientation optimization is achieved via an analytical solution derived for fully anisotropic materials and multi-input-multi-output compliant mechanisms. Numerical examples are presented to show the validity of the present MIST method to design multi-material hinge-free compliant mechanisms under multiple design-dependent loadings. [ABSTRACT FROM AUTHOR]

This paper presents a novel design and control strategies for a parallel two degrees-of-freedom (DOF) flexure-based micropositioning stage for large-range manipulation applications. The motion-guiding beam utilizes a compound hybrid compliant prismatic joint (CHCPJ) composed of corrugated and leaf flexures, ensuring increased compliance in primary directions and optimal stress distribution with minimal longitudinal length. Additionally, a four-beam parallelogram compliant prismatic joint (4BPCPJ) is used to improve the motion decoupling performance by increasing the off-axis to primary stiffness ratio. The mechanism's output compliance and dynamic characteristics are analyzed using the compliance matrix method and Lagrange approach, respectively. The accuracy of the analysis is verified through finite element analysis (FEA) simulation. In order to examine the mechanism performance, a laser interferometer-based experimental setup is established. In addition, a linear active disturbance rejection control (LADRC) is developed to enhance the motion quality. Experimental results illustrate that the mechanism has the capability to provide a range of 2.5 mm and a resolution of 0.4 μm in both the X and Y axes. Furthermore, the developed stage has improved trajectory tracking and disturbance rejection capabilities. [ABSTRACT FROM AUTHOR]

The sequential approximate integer programming (SAIP) method successfully solves multiple types of large-scale topology optimization problems by solving a sequence of separable approximate integer programming subproblems. However, these subproblems must be with quadratic/linear objective function with linear constraints that can be analytically solved by the canonical relaxation algorithm (CRA). Besides, SAIP relies on the decreasing volume fraction strategy so that it owns difficulties to confront topology optimization problems without active volume constraints. The success of MMA (method of moving asymptotic) inspires us to introduce the classical sequential conservative approximate programming that can generate a sequence of steadily improving feasible designs and present a sequential conservative integer programming (SCIP) method for the development of SAIP. This new method generates a sequence of nonlinear approximate integer programming subproblems containing the reciprocal variables, whose conservation is controlled by moving asymptotes. Since CRA is invalid for nonlinear subproblems, a simple design variable update rule derived by the KKT (Karush-Kuhn-Tucker) conditions is given. Based on the above idea, SCIP obtains stable optimization processes without relying on linear constraints, such as the volume constraint, and thus complex discrete variable topology optimization problems can be efficiently solved. Various requirements of topology optimization problems are handled, including equality or inequality constraints, and inactive or active volume constraints. Numerical results show that since the conservative property has been inherited, the convergence of the optimization process can be regulated without additional structural analysis. [ABSTRACT FROM AUTHOR]

Compliant constant-force mechanisms (CCFMs) are compliant mechanisms that provide nearly constant forces over prescribed deflection ranges. This study proposes a topology optimization method for designing hinge-free compliant constant-output-force mechanisms. Bifurcation cause the objective function to oscillate, leading to convergence failure. Therefore, a constraint for preventing bifurcation in constant-output-force mechanisms is proposed. Moreover, a minimum scale constraint method that extends the design domain is utilized in the proposed optimization algorithm. The relationship between the minimum length scale and the force variation in the optimized CCFM is obtained and discussed, and an optimized CCFM is fabricated and tested. The optimized CCFM exhibits a force variation of 0.7% over a constant-force stroke of 26% of the CCFM length and is thus competitive among recently proposed CCFMs. [ABSTRACT FROM AUTHOR]

Fused silica glass is a material with outstanding mechanical, thermal and optical properties. Being a brittle material, it is challenging to shape. In the last decade, the manufacturing of monolithic flexible mechanisms in fused silica has evolved with the femtosecond-laser-assisted etching process. However, instrumenting those structures is demanding. To address this obstacle, this article proposes to inscribe a Bragg Grating sensor inside a flexure and interface it with an optical fibre to record the strain using a spectrum analyser. The strain sensitivity of this Bragg Grating sensor is characterized at 1.2 pm/ μ ϵ (1 μ ϵ = 1 microstrain). Among other applications, deformation sensing can be used to record a force. Its use as a micro-force sensor is estimated. The sensor resolution is limited by our recording equipment to 30 μN over a measurement range above 10 mN. This technology can offer opportunities for surgery applications or others where precision and stability in harsh environments are required. [ABSTRACT FROM AUTHOR]

This study explores the application of concurrent multiscale topology optimization in the design of lightweight hygral-activated porous compliant mechanisms. The proposed approach utilizes two distinct representations of the design problem, namely macro and microscale domains, to achieve an optimized design. By implementing a concurrent multiscale topology optimization framework, the effective properties of the microscale, including elastic and hygral diffusivity tensors and the hygral expansion coefficient, are calculated and used as the hygro-elastic modeling effective properties of the macroscale. Furthermore, this study considers hygral transport in solids and hygral evaporation, thereby enabling simultaneous consideration of hygral transfer physics. A sensitivity analysis of the proposed concurrent optimization scheme was performed to address both macro and microstructure coupling, as well as hygro-elastic physics coupling. Numerical simulations were conducted for various single and multiple microstructure systems to investigate their performance. A study was also carried out to examine the impact of incorporating multiple microstructures into a single macro design domain on the macrostructure's dependency. The results showed that the use of multiple microstructures improved the design freedom and performance-to-weight ratio of the macrostructure. [ABSTRACT FROM AUTHOR]

A morphing flap, a morphing wing section, can deform its geometrical shape seamlessly and continuously to improve the aerodynamic performance. To obtain a compliant morphing flap internal mechanism to realize the target deformation, this study aimed to develop a nonlinear topology optimization method based on a level-set method. However, numerical instability occurs during the design optimization process within the scope of finite deformation analyses. Accordingly, the numerical instability problem caused by an artificial weak material representing a void region in the optimization algorithm was resolved. In particular, this problem was resolved by structural modeling without such weak materials using the mesh adaptation method and by installing a spring component with a negligibly small spring constant. Subsequently, a finite deformation analysis was performed and integrated with the level-set-based topology optimization model. Finally, the proposed method was validated by solving the morphing flap design problem through numerical analyses, wherein an optimum structural configuration under finite deformation was obtained. [ABSTRACT FROM AUTHOR]

Background: The design of compliant mechanisms requires detailed knowledge about the stiffness properties of their flexible segments. However, there are no standardized test methods for flexure hinges, and therefore the influence of manufacturing-specific effects, such as anisotropy, on the stiffness properties cannot be quantified. Objective: This paper presents novel test methods for variable cross-section flexure hinges subjected to large deformations and pure bending loading, which determine the bending stiffness of flexure hinges over their entire deflection range using a universal testing machine. Methods: The novel test methods for flexure hinges are based on the tensile test, the four-point bending test (FPBT), and the column bending test (CBT). These test methods were initially formulated for constant cross-section specimens, but are adapted in this study to examine variable cross-section specimens. The derived test methods are validated by using isotropic materials with well-known properties and by comparing the calculated deflections with deflections measured by means of image processing. Results: The deflection validation shows that the adapted CBT (aCBT) is accurate over the entire deflection range, achieving curvature of up to κ = 0.40 mm - 1 , whereas the maximum curvature in the adapted FPBT (aFPBT) is limited by the test methodology to about κ = 0.15 mm - 1 . At small strains, the flexural modulus determined in the aCBT and aFPBT agrees well with the Young's modulus determined in the tensile test, as would be expected for isotropic materials. Conclusion: The aCBT proves to be a suitable test method for flexure hinges at large deflections, whereas the stiffness characterization at small deflections can be performed with both the aCBT and the aFPBT. The presented test methods validated on isotropic materials form the basis for characterizing anisotropic flexure hinges with geometry-dependent stiffness properties. [ABSTRACT FROM AUTHOR]

Owing to inherent flexibility, compliant actuator with physical elastic elements can implement compliant interactions between robot and environment. Nonlinear stiffness elastic actuators (NSEAs) use one motor to adjust position and stiffness, which improve compactness of variable stiffness actuators, and consider high torque/force resolution and high bandwidth. The primary challenge of designing a NSEA is designing a reliable compliant mechanism with a given torque-deflection profile. In this study, a general design method of torsional compliant mechanism through given discrete torque-deflection points was proposed, where a chain algorithm based on 2R pseudo-rigid-body model was used to describe the large deformation in elastic elements. Moreover, the theoretical model of stiffness of a compliant mechanism based on series flexible beams was developed. Based on the proposed model, the dimensional parameters of proposed compliant mechanism were designed satisfying the condition of the given torque-deflection points. Finally, simulation and physical experiment of the designed compliant mechanism through three given torque-deflection points are conducted to show the effectiveness of the proposed method. The designed compliant mechanism was tested and evaluated in the self-developed NSEA. [ABSTRACT FROM AUTHOR]

A serial 2D planar compliant mechanism has been proposed based on novel "S-shaped" flexure hinges for atomic force microscopy applications. The bridge-lever type mechanism driven by piezoelectric actuators serves as a displacement amplifier. The optimal geometrical parameters were found to maximize the workspace and natural frequency through the Monte-Carlo search algorithm. Also, the performance of the developed system was investigated by Matrix-based Compliance Modeling (MCM), Finite Element Analysis (FEA), and experiments. All models indicate that the mechanism has an approximately linear force-deflection relationship, high safety factor, and a reasonable amplification ratio of about 4.5 and 5.5 for the inner and outer stages in the analytical approach, 4.4 and 5.3 in FEA. Finally, experiments on a fabricated open-loop controlled prototype revealed 4.2 and 5.1 amplification ratio for stages that resulted in a 94 × 124 μm rectangular workspace and a natural frequency of 224.6 Hz, which is about 5% lower than the results predicted using FEA. • Design, model, and analyze a compliant planar 2D mechanism for AFM micropositioning applications. • Novel "S-shaped" flexure hinge used for maximizing workspace with minimum space occupied. • Investigating mechanism performance: Analytical (MCM), numerical (FEA), and experimental (DIC, EMA) approaches used. [ABSTRACT FROM AUTHOR]

As an art of paper folding, origami has been widely explored by artists for centuries. Only in recent decades has it gained attention from mathematicians and engineers for its complex geometry and rich mechanical properties. The surge of origami-inspired metamaterials has opened a new window for designing materials and structures. Typically, to build origami structures, a sheet of material is folded according to the creaselines that are marked with compliant mechanisms. However, despite their importance in origami fabrication, such compliant mechanisms have been relatively unexplored in the setting of origami metamaterials. In this study, we explore the relationship between the design parameters of compliant mechanisms and origami mechanical properties. In particular, we employ single hinge crease and Kresling origami, representative examples of rigid and non-rigid origami units, fabricated using a double-stitch perforation compliant mechanism design. We conduct axial compression tests using different crease parameters and fit the result into the bar-hinge origami model consisting of axial and torsional springs. We extract the relationship between the spring coefficients and crease parameters using Gaussian process regression. Our result shows that the change in the crease parameter contributes significantly to each spring element in a very different manner, which suggests the fine tunability of the compliant mechanisms depending on the mode of deformation. In particular, the spring stiffness varies with the crease parameter differently for rigid and non-rigid origami, even when the same crease parameter is tuned. Furthermore, we report that the qualitative static response of the Kresling origami can be tuned between monostable and bistable, or linear and nonlinear, by only changing the crease parameter while keeping the same fold pattern geometry. We believe that our compiled result proffers a library and guidelines for choosing compliant mechanisms for the creases of origami mechanical metamaterials. [ABSTRACT FROM AUTHOR]

To address coupling motion issues and realize large constant force range of microgrippers, we present a serial two-degree-of-freedom compliant constant force microgripper (CCFMG) in this paper. To realize a large output displacement in a compact structure, Scott–Russell displacement amplification mechanisms, bridge-type displacement amplification mechanisms, and lever amplification mechanisms are combined to compensate stroke of piezoelectric actuators. In addition, constant force modules are utilized to achieve a constant force output. We investigated CCFMG's performances by means of pseudo-rigid body models and finite element analysis. Simulation results show that the proposed CCFMG has a stroke of 781.34 ${\unicode[Times]{x03BC}}\mathrm{m}$ in the X-direction and a stroke of 258.05 ${\unicode[Times]{x03BC}}\mathrm{m}$ in the Y-direction, and the decoupling rates in two directions are 1.1% and 0.9%, respectively. The average output constant force of the clamp is 37.49 N. The amplification ratios of the bridge-type amplifier and the Scott–Russell amplifier are 7.02 and 3, respectively. Through finite element analysis-based optimization, the constant force stroke of CCFMG is increased from the initial 1.6 to 3 mm. [ABSTRACT FROM AUTHOR]

The compliant planar positioning stage actuated by voice coil motors can obtain nanoscale motion accuracy within a millimeter motion range and has received increasing attention in precision engineering. However, there is always a contradiction between the actuation force and the output stiffness in the design of the stage. This study presents the design of a novel redundant actuated planar 3-DOF-compliant nanopositioning stage. A redundant actuated configuration can increase the output stiffness of the stage and decrease the peak actuating force. The analytical stiffness model, kinetostatic model, and dynamic model of the stage are established, which illustrate the high force transmission efficiency and dynamic decoupling feature of the stage. The geometric parameters were optimized based on the established models, and model validation and performance evaluation of the stage were conducted via finite element analysis. Finally, a prototype positioning stage is fabricated. Experimental results show that the proposed stage can achieve a motion range of up to ±2.5 mm × ±2.5 mm × ±2.5° with a resolution of 80 nm and 0.28″, and the tracking error ratio for a composite Lissajous trajectory is within 0.102%. • A novel redundant actuated 4- P PR planar xyθ compliant nanopositioning stage with large motion range is proposed. • The analytical stiffness, kinetostatic and dynamic models of the stage is established. • The high force transmission efficiency of the stage is proved by the analytical models. • A prototype positioning stage is fabricated, nano-scale resolution and positioning accuracy are achieved. [ABSTRACT FROM AUTHOR]

Cutting toolholders, with designed in-built compliant mechanisms, are frequently used for machining microfeatures. In this paper, compliant structures are designed using trusses as they exhibit a superior strength-to-weight ratio. Systematically stacked two-stage truss structures along with flexure hinges are designed to yield the desired precise cutting motion. The materially reduced efficient design amplifies the output force and greatly assists in overcoming cutting resistance during machining. The characteristics of the designed compliant tool holder are analysed by considering the output force and displacement for a given input. Both mathematical modelling to determine the force and finite element analysis to identify the critical stress regions when subjected to a prescribed input displacement are presented. As part of dynamic analysis, modal analysis and harmonic response studies were performed to determine how the trussed compliant structure deforms when subjected to dynamic loadings. The designed tool holder was additively manufactured using functionally rigid polyamide-12-glass-bead (PA12-GB) material. The performance of the developed cutting tool holder is then verified by machining radially graded surfaces following which, the machining results are presented in this paper. [ABSTRACT FROM AUTHOR]

Precision motion systems that call for an ultrahigh resolution are widely used in ultrahigh-precision engineering applications. In this article, a 6-SPS perpendicular compliant parallel micro-manipulation robot is presented. It is difficult to establish the mapping relationship between the applied voltage and end-effector pose due to the existence of compliant joints and piezoelectric actuators. A modeling method for a 6-SPS perpendicular compliant parallel micro-manipulation robot considering the motion in nonfunctional directions and hysteresis effect is proposed to reflect the characteristic from input voltage to output pose. The motion of the spherical compliant joint is regarded as a spatial six degrees-of-freedom mechanism. This method considers the motion errors in multiple nonfunctional directions of the compliant joints. The internal force and torque are also taken into account based on the spatial force and moment balance condition. The slow, fast dynamic modes, and hysteresis nonlinearity behavior are described using a series and parallel hybrid model structures. The kinematic model and compliance model without considering the motion in nonfunctional directions are conducted for comparison. Simulation results show that the presented modeling method has higher modeling accuracy. Finally, experiments on a 6DOF compliant parallel micro-manipulation robot reveal the fine modeling performance of the developed method for the precision motion systems in the presence of intrinsic hysteresis effect and motion error of compliant joints. [ABSTRACT FROM AUTHOR]

Precision motion systems that call for an ultrahigh resolution are widely used in ultrahigh-precision engineering applications. In this article, a 6-SPS perpendicular compliant parallel micro-manipulation robot is presented. It is difficult to establish the mapping relationship between the applied voltage and end-effector pose due to the existence of compliant joints and piezoelectric actuators. A modeling method for a 6-SPS perpendicular compliant parallel micro-manipulation robot considering the motion in nonfunctional directions and hysteresis effect is proposed to reflect the characteristic from input voltage to output pose. The motion of the spherical compliant joint is regarded as a spatial six degrees-of-freedom mechanism. This method considers the motion errors in multiple nonfunctional directions of the compliant joints. The internal force and torque are also taken into account based on the spatial force and moment balance condition. The slow, fast dynamic modes, and hysteresis nonlinearity behavior are described using a series and parallel hybrid model structures. The kinematic model and compliance model without considering the motion in nonfunctional directions are conducted for comparison. Simulation results show that the presented modeling method has higher modeling accuracy. Finally, experiments on a 6DOF compliant parallel micro-manipulation robot reveal the fine modeling performance of the developed method for the precision motion systems in the presence of intrinsic hysteresis effect and motion error of compliant joints. [ABSTRACT FROM AUTHOR]

Compliant mechanisms are often used in combination with piezoelectric drivers in the design of high-precision linear stages. Numerous hinge designs have been developed due to varying requirements for stiffness and flexibility in different areas of the compliant mechanism frame. Their geometry was traditionally limited mostly to 2D shapes due to limitations of typically used manufacturing processes: electrical discharge machining and stamping. Novel additive manufacturing technologies could allow more complex shapes that could result in better performance. The objective of this paper was to minimize internal losses of the stage caused by unwanted material deformation to maximize efficiency and therefore, the displacement of the linear stage. For this purpose, finite element method simulation was used for the preliminary improvement of geometry, which was afterward confirmed with experimental results. The design of a compliant mechanism with perforated hinges achieved promising results in terms of efficiency improvement. [ABSTRACT FROM AUTHOR]

With the increasing implementation of compliant mechanisms in high-precision and high-accuracy applications, the need to evaluate the positioning performance of the flexure hinges becomes evident. In this paper, the determination of the accuracy of planar flexures is addressed by analyzing and comparing the available criteria presented in literature, including a new criterion based on the pole of the displacements. For uniform flexures, an analytical formulation is developed for end-moment loads, whereas complex loading conditions, resulting in an inflection point, are analyzed and numerically evaluated. The accuracy criteria are also applied for analyzing the positioning performance of the cross-axis flexural pivot. Various relations among the different criteria are determined, and their limitations, such as the non-bijective correspondence with the deformed configurations, are discussed. The criteria are applied to the design of a high-accuracy cross-axis pivot. [ABSTRACT FROM AUTHOR]

This paper presents the design, fabrication and testing of a shape memory alloy (SMA)-actuated monolithic compliant gripping mechanism that enables translational motion of the gripper tips for grasping operation suitable for micromanipulation and microassembly. The design is validated using a finite element analysis (FEA), and a prototype is created for experimental testing. The reported gripping structure is simple and easy to build and design. The gripper is demonstrated to have a displacement amplification gain of 3.7 that allows maximum tip displacement up to 1.2 cm to possess good handling range and geometric advantage which cannot be accomplished by conventional grippers. The position of the gripper tip is predicted from the variation in the electrical resistance of the SMA wire based on the self-sensing phenomena. Self-sensing actuation of the SMA allows the design of a compact and lightweight structure; moreover, it supports the control loop/scheme to use the same SMA element both as an actuator and sensor for position control. The geometrical dimensions of the SMA wire-actuated monolithic compliant gripper is 0.09 m × 0.04 m and can be operated to handle objects with a maximum size of 0.012 m weighing up to 35 g. [ABSTRACT FROM AUTHOR]

Minimally invasive surgery (MIS) is a viable alternative to general surgery with distinct advantages. Robotically assisted MIS, has been demonstrated to achieve higher accuracy and repeatability in comparison with those of manual procedures. Despite these advantages, owing to the nature of some surgical procedures in which dexterous tissue manipulations in deep narrow areas of the human body are necessary, there is a need for further miniaturized tools with smaller bending radii. To cater to this requirement, this study proposes a new compliant mechanism based surgical robotic forceps. It can generate four degrees of freedom at the tip of the forceps including two bending motions in two perpendicular axes, grasping and rotation. A better combination of the stress distribution through the elastic material, grasping force, and range of motion was determined based on a series of finite element analyses. In addition, the manufactured prototype underwent a series of laboratory experiments to evaluate its effectiveness. Details of the mechanism, finite element analysis, prototype implementation, and evaluations are presented in this paper. [ABSTRACT FROM AUTHOR]

A foldable compliant XY precision positioning stage with good decoupling property in both axes is developed for precision applications. The compliant rolling-contact element (CORE) is innovatively incorporated in the design of the stage to realize the folding function for compacting the mechanism structure. The input stiffness of the motion platform is determined using the matrix method and is verified by a conventional stiffness modeling method. Finite element analysis (FEA) simulations of three bridge-type amplifiers are conducted and compared to determine the preferable one for magnifying the limited output displacement of the actuator. A foldable stage is then assembled and its decoupling capability and dynamic performances are investigated with the ANSYS software. In addition, a prototype is fabricated to experimentally test the performance of the stage. Results demonstrate that the employed proportional-integral-derivative (PID) feedback controller can settle in 70 ms without overshooting. The closed-loop controlled stage is able to reach a resolution of 2 μm and has small tracking errors within ± 1 μm in the circular-contouring tests. [ABSTRACT FROM AUTHOR]

The paper summarises the results of investigations of a 2D compliant manipulator implementing two independent orthogonal linear displacements. The device is comprised of a steel element with monolithic design, its motion induced by two independent screw-drive actuators. Underpinning the monolithic system design is the classical planar lever mechanism model. Macro-scale motions of the drives are reduced by two variators (variable displacement transmission units) effecting seamless control of displacement limitation via the settings of two additional independent screw-drive actuators. The resultant of thus reduced independent displacements is obtained at one vertex of the square platform where an end-effector or gripper may be mounted. A transformation matrix is formulated containing kinematic and coupling ratios. FEM calculations were performed to estimate the stress levels in flexure hinges in the neighbourhood of the motion stages. The manipulator workspace where elastic stresses will arise in flexure hinges has been determined. Tests conducted with the use of a microscope have validated the predicted motion properties of the monolithic system. • Monolith-design manipulator converts the macro-scale motions of the drive into macro-scale motions of the end-effector. • The patented redactor allows the kinematic ratio to be seamlessly varied and its value maintained. • Observation of the end-effector motions under the microscope enables the manual control of the manipulator. • There is no need to employ piezoelectric drives. [ABSTRACT FROM AUTHOR]

In this study, a vibration isolator is designed as a periodic structure, which is constructed with embedded inertial amplification mechanisms. At first, various compliant inertial amplification mechanism configurations are proposed. Among them, the one with the widest vibration isolation frequency band is selected via conducted parametric studies. Then, the determined mechanism is utilized as the unit cell (i.e., the repetitive building block) of the periodic structure. Finally, the displacement transmissibility (i.e., Frequency Response Function (FRF)) plots are presented to demonstrate the vibration isolation performance of the designed periodic structure. According to the numerical results, the selected unit cell mechanism provides more than 25 % vibration isolation between 190-360 Hz frequency values. On the other hand, the periodic structure formed with linearly incorporating three unit cell mechanisms provides more than 80 % vibration isolation for the same frequency range (i.e., 190-360 Hz). As a conclusion, if the number of unit cells used in the periodic structure is increased further, higher vibration isolation levels will be achieved for 190-360 Hz frequency range. [ABSTRACT FROM AUTHOR]

Replicating animal movements with robots provides powerful research tools because key parameters can be manipulated at will. Facing the lack of standard methods and the high complexity of biological systems, an incremental bioinspired approach is required. We followed this method to design a snake robot capable of reproducing the natural swimming gait of snakes, i.e., the lateral undulations of the whole body. Our goal was to shift away from the classical broken line design of poly-articulated snake robots to mimic the far more complex fluid movements of snakes. First, we examined the musculoskeletal systems of different snake species to extract key information, such as the flexibility or stiffness of the body. Second, we gathered the swimming kinematics of living snakes. Third, we developed a toolbox to implement the data that are relevant to technical solutions. We eventually built a prototype of an artificial body (not yet fitted with motors) that successfully reproduced the natural fluid lateral undulations of snakes when they swim. This basis is an essential step for designing realistic autonomous snake robots. [ABSTRACT FROM AUTHOR]

This paper introduces an original, fully compliant universal joint design. Many mechanisms with different dimensions are investigated. The proposed design is a single-piece compliant mechanism. The number of flexible segments is a design parameter determined as a function of transferred torque. The mechanism can be produced by additive manufacturing from polylactic acid and polypropylene. It is possible to produce the proposed design as a single piece of polypropylene by additive manufacturing and injection molding methods; thus, it has the advantage of ease in manufacturing. The proposed design's bending and torque transmission capacities are determined by applying analytical and numerical methods. Furthermore, a prototype was manufactured, and experiments were conducted. It is verified that the results of the experiments are consistent with theoretical approaches. The proposed fully compliant universal joint design has a great potential in the industry. [ABSTRACT FROM AUTHOR]

An XYZ compliant micropositioner has been widely mentioned in precision engineering, but the displacements in the X, Y, and Z directions are often not the same. In this study, a design and optimization for a new XYZ micropositioner are developed to obtain three same displacements in three axes. The proposed micropositioner is a planar mechanism whose advantage is a generation of three motions with only two actuators. In the design strategy, the proposed micropositioner is designed by a combination of a symmetrical four-lever displacement amplifier, a symmetrical parallel guiding mechanism, and a symmetrical parallel redirection mechanism. The Z-shaped hinges are used to gain motion in the Z-axis displacement. Four flexure right-circular hinges are combined with two rigid joints and two flexure leaf hinges to permit two large X-and-Y displacements. The symmetrical four-lever displacement amplifier is designed to increase the micropositioner's travel. The displacement sensor is built by embedding the strain gauges on the hinges of the micropositioner, which is developed to measure the travel of the micropositioner. The behaviors and performances of the micropositioner are modeled by using the Taguchi-based response surface methodology. Additionally, the geometrical factors of the XYZ micropositioner are optimized by teaching–learning-based optimization. The optimized design parameters are defined with an A of 0.9 mm, a B of 0.8 mm, a C of 0.57 mm, and a D of 0.7 mm. The safety factor gains 1.85, while the displacement achieves 515.7278 µm. The developed micropositioner is a potential option for biomedical sample testing in a nanoindentation system. [ABSTRACT FROM AUTHOR]

The rotational joint plays a vital role in the industrial and civil areas, which is typically utilized to achieve the relative rotation between the adjacent parts. Generally, structuring a conventional rotational joint involves the bulk actuators (e.g., motor and hydraulic cylinders) and complex structures, bringing difficulty for miniaturing the dimension. In this paper, a class of novel rotational mechanisms, which were constructed by the combination of compliant mechanisms (e.g., cartwheel pivot and multileaf pivot) and intelligent actuator (e.g., shape memory alloy (SMA) wire and spring), was proposed to reduce the complexity of the conventional rotational joints. As the case study, a novel SMA wire-driven flexural rotational mechanism (SDFRM), which is constructed by the cartwheel pivot and SMA wire, was developed to demonstrate the feasibility of combining the compliant mechanism and smart actuator. After establishing the static model of the cartwheel pivot and the thermal effect model of the SMA wire, the overall model of SDFRM was developed for the comprehensive performance analysis and the control system design. After that, the model validation and experiments were performed with the proposed prototype and control system. It can be seen from the experimental results that the proposed model can be validated within the error of 3.8%. In addition, the performance study on SDFRM indicates that the prototyped SDFRM system can track the given trajectories within the error of 0.2 mm in the workspace. As a result, the proposed concept was demonstrated as an effective way to reduce the dimension and weight of the conventional rotational joint. [ABSTRACT FROM AUTHOR]

Femtosecond laser direct writing (LDW) is an enabling technique in the fabrication of micro-/nano-scale devices. In a typical LDW system, the high precision motion system serves as the key component for micro-/nano-fabrication. In this paper, a cost-effective LDW system is proposed with a self-developed compliant nanomanipulator. The accuracy of the LDW system with the proposed nanomanipulator is validated through the fabrication of optical grating patterns with micro-scale feature sizes (< 3 μ m). The optical grating patterns are fabricated with different spacings, scan speeds and laser powers, and surface characterization and quantitative analysis of the samples are conducted. The characterization results demonstrate that the proposed LDW system is capable of controlling the spacing accuracy within 300 nm in a millimetre-level working range. Compared with the existing commercial laser direct writing system of sub-micrometer level motion accuracy, the proposed compliant nanomanipulator-based femtosecond laser direct writing system achieves comparable performances with much lower costs, and it has broad potential applications to sub-micron level laser direct writing fabrication. [Display omitted] • A cost-effective laser direct writing system with a compliant nanomanipulator. • Precision grating patterning on the fused silica by femtosecond pulse laser. • Fabrication results show the spacing accuracy ¡ 300 nm in a millimetre-level range. [ABSTRACT FROM AUTHOR]

The quasi-zero stiffness (QZS) mechanism can rely on the combination of negative and positive stiffness elements to achieve very low dynamic stiffness while obtaining high static stiffness to support the isolated payload. It is a nonlinear shock isolation method with good shock isolation performance. In this paper, a new QZS compliant shock isolator is designed for shock isolation under strong acceleration shock excitation(>1000g), by paralleling a fixed-guided beam with negative stiffness and a Roberts configuration compliant beam with positive stiffness. The force-displacement characteristics of the QZS compliant shock isolator is analyzed and calculated theoretically using an elliptic integration method, and are verified by comparison using finite element simulation. The dynamic time-domain response characteristics of the QZS compliant shock isolator under the excitation of ideal shock excitation with different amplitudes, different periods, different payloads, and actual shock excitation are calculated, and compared with the performance of a general positive stiffness compliant shock isolator under the same excitation. The results show that the proposed QZS compliant shock isolator can be applied to shock isolation under strong shock excitation, and exhibits good constant force characteristics in the whole stroke during the shock isolation process, and is less affected by the amplitude and period of shock excitation. Compared with the general positive stiffness compliant shock isolator, the proposed QZS compliant shock isolator can significantly reduce the peak of the shock, reduce the maximum acceleration ratio and improve the shock isolation performance. It can provide some theoretical guidance for the design of the QZS compliant shock isolator under strong shock excitation. • A quasi-zero stiffness shock isolator suitable for strong shock excitation is proposed. • The isolator has a constant force characteristics almost in the whole stroke more than 8 mm. • Compared the performance with the general positive stiffness shock isolator. • The feasibility of using QZS compliant mechanism under strong excitation isolator is verified theoretically. [ABSTRACT FROM AUTHOR]

A compliant mechanism-based micro/nanopositioning stages are used to perform high precision motion in various fields. In recent years, researches proposed various methods to achieve the compliant mechanism. This article presents a design of XYθ micropositioning stage using parametrisation technique. Conceptual design of positioning stage is developed using a combination of simple four bars. This can take a single load for angular displacement of one side or double loading for linear displacement. All the four sides of the stage can take loads depending on the direction of displacement. Conceptual design is converted into a working model using a parameterisation technique in which geometrical parameter is determined. Numerical simulations are performed for single loading and double loading to estimate x, y and θ. A working model is fabricated using a wire EDM process and has been tested for actual and numerical results. [ABSTRACT FROM AUTHOR]

A pseudo static parametric model of the micro-displacement compliant amplification mechanism is proposed based on the dynamic stiffness matrix of flexible beams and the matrix displacement method. This model can be used for rapid motion prediction and parametric motion analysis for the new mechanism. Then the analytical model of displacement amplification ratio is obtained. A new mechanism is obtained by optimizing the dimensions and shape of the structure based on simulated annealing algorithm. Compared with the original structure, its amplification ratio increases by 9% and the natural frequency is 409Hz. The optimization results are compared with FEA simulations with less than 2% difference, which verifies the accuracy of the model. The amplification ratio variation of the new mechanism with load and input displacement and the influence of manufacturing errors at key joints on output displacement are analyzed. The results show that the X-direction manufacturing errors of the top endpoint and output stage have the greatest influence on the output displacement. [ABSTRACT FROM AUTHOR]

A pseudo static parametric model of the micro-displacement compliant amplification mechanism is proposed based on the dynamic stiffness matrix of flexible beams and the matrix displacement method. This model can be used for rapid motion prediction and parametric motion analysis for the new mechanism. Then the analytical model of displacement amplification ratio is obtained. A new mechanism is obtained by optimizing the dimensions and shape of the structure based on simulated annealing algorithm. Compared with the original structure， its amplification ratio increases by 9% and the natural frequency is 409Hz. The optimization results are compared with FEA simulations with less than 2% difference， which verifies the accuracy of the model. The amplification ratio variation of the new mechanism with load and input displacement and the influence of manufacturing errors at key joints on output displacement are analyzed. The results show that the X-direction manufacturing errors of the top endpoint and output stage have the greatest influence on the output displacement. [ABSTRACT FROM AUTHOR]

Recent advances in Minimally Invasive Surgery, multifunctional instruments are essential to improve the efficiency of the surgical procedure. Surgical instruments with combination of wire and links demonstrate high performance, but fabrication and assembly of the instruments are challenging. This open the way for alternate design, and compliant mechanism is the appropriate choice. Compliant mechanism is the flexible mechanism that transfer loads from one point to another through elastic body deformation. This research paper introduces the novel design of compliant forceps, which can cut and collect tissues. Forceps require very high force to cut the tissues and less force to collect the tissues. The concept is developed with respect to the requirement, where switching of functions can be obtained by applying respective input actuation. The concepts of compliant forceps are converted to the realistic model using parameterisation technique. Structural performance of compliant forceps is investigated through the finite element method (FEM). FEM is used to measure the cutting force and grasping force. [ABSTRACT FROM AUTHOR]

The tasks of electrical micro- and nanoprobing require precision that goes beyond human perception and therefore, depend on sensors providing real-time feedback. Efforts towards automation in micro- and nanoprobing and emerging areas such as branched nanowire networks, has resulted in a growing number of applications where electrical probing without simultaneous force control is insufficient. This article presents the design of a novel mesoscale flexure-based load cell dedicated to micro- and nanoprobing. By integrating systems for stiffness adjustment and a zero offset tuning, the force-displacement characteristic of the device can be adapted to suit a wide range of applications, from the measurement of large forces up to 60 mN to a resolution as high as 10.1 nN, and even negative stiffness (bistable) behavior. By controlling the tuning during measurements, a virtual dynamic range of 6.38 ⋅ 106 is achievable, which is one order of magnitude greater than existing commercial products. We validated the results experimentally on a titanium alloy prototype fabricated by electrical discharge machining (EDM). Experimental and finite element results were also used to validate the analytical model of the load-cell. Additionally, the device allows for probe tip replacement, which is a significant advantage compared to existing MEMS load cells, and comprises a gravity compensation system to accommodate a wide range of commercially available probe tips. • A novel design of a load cell with adjustable stiffness and a zero-offset tuning. • A model of the effect of gravity and a method of its compensation. • Design at mesoscale reduces fragility and facilitates the end-effector replacement. • Measurement of small forces with a resolution of 10 nN and high forces up to 60 mN. • Numerical simulation and a metal prototype allowing experimental validation. [ABSTRACT FROM AUTHOR]

Microgrippers act as an end effector in micromanipulation systems, completing the pick-transport-release operations during the working process. This paper presents the design, modeling, optimization, simulation, and experiment of a novel piezoelectrically actuated compliant microgripper for micromanipulation and microassembly. Considering the space and cost constraints of the micromanipulation system, the area-usage efficiency and piezoelectric actuator utilization efficiency are introduced to evaluate its performance. A three-stage amplification mechanism based on bridge-type and leverage mechanisms arranged in series is introduced to achieve a large jaw displacement. The displacement amplification ratio of the microgripper is analyzed via the pseudo-rigid-body model approach. Optimization based on response surface analysis was conducted to determine the structural parameters of the compliant mechanism. Finite-element analysis is performed to evaluate the gripper performance. Moreover, a gripper prototype was fabricated for the experimental test. The investigation results indicate that the gripper allows a maximum gripping displacement of 548.42 μ m, a first natural frequency of 334 Hz, and a motion resolution of ±0.75 μ m. In comparison with previous designs, the reported microgripper has the advantages of a larger displacement, higher area-usage efficiency, and better PEA utilization efficiency. The micromanipulation capability of the developed gripper was demonstrated by gripping three tiny objects of different sizes and shapes. • The design and testing of a novel piezoelectrically actuated compliant microgripper is presented • It offers a high area usage efficiency and high piezoelectric actuator utilization efficiency • Three-stage amplification mechanism is introduced with bridge-type mechanism and leverage mechanism • Analytical modeling, design optimization and FEA simulation study are carried out • Prototype is fabricated and experimental results verify its gripping capability for tiny objects [ABSTRACT FROM AUTHOR]

Bistable mechanisms are prevalent across a broad spectrum of applications due to their ability to maintain two distinct stable states. Their energy consumption is predominantly confined to the process of state transitions, thereby enhancing their efficiency. However, the transition often requires two distinct digital inputs, implicating the requirement of multiple actuators. Here, we propose an elastic and contactless design strategy for inducing state transitions in bistable mechanisms, requiring only a single digital input. The strategy leverages internal information, interpreted as system state, as an extra input to make a weighted decision for transitioning to the subsequent state. We characterize the behavior using a spring-based rigid-body model, consisting of a column near bifurcation, combined with a non-linear spring connected to a bistable element that represents the information state. The results show that a nonlinear spring with a quadratic stiffness function, i.e., representing internal instability, is crucial for regulating state-switching behavior. We then demonstrate this design strategy by developing a monolithic and compliant design embodiment and experimentally evaluate its behavior. [Display omitted] • Design method for state switching in bistable mechanisms with a single digital input. • Quadratic stiffness was identified as key to state-switching behavior. • Developed and experimentally validated a compliant design for state-switching. [ABSTRACT FROM AUTHOR]

Kirigami is an art of paper cutting, which can be used in mechanical metamaterials, actuators, and energy absorption based on its deployable and load-deflection characteristics. Traditional cuts with zero width produce undesirable plastic deformation or even tear fracture due to stress concentration in stretching. This study proposes to enlarge the cut width into a notch flexure, which is applied to an orthogonality-cutted kirigami sheet, which buckles out of plane into a 3D configuration patterns under uniaxial tension. The use of compliant beam as the notch makes the stress distribution around the cuts more uniform in both elastic and elastoplastic regime. The experimental and numerical results show that by tuning the geometric parameters of cuts and material properties of the sheets, the trigger condition of 3D patterns can be adjusted. Potential capability of tunable phononic wave propagation in this kirigami-inspired metamaterial is demonstrated. This design methodology offers a theoretical guide for kirigami-based structures. [ABSTRACT FROM AUTHOR]

Laser scanners with mechanically driven mirrors have exhibited increasing potential for various applications, such as displays and laser radar. Resonant scanners are the predominantly used scanners; however, non-resonant scanners are required for applications where point-to-point driving is desirable. Because a non-resonant drive cannot amplify the drive angle owing to the resonance phenomenon, high values are difficult to achieve for the main performance metrics of the scanners: mirror area, drive angle, and operating frequency. In this paper, we present a two-axis scanner with a piezoelectric actuator made of a piezoelectric single-crystal Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 as the actuation force source. The scanner contains a circular mirror with a diameter of 7 mm and achieves an average static mechanical deflection angle amplitude of 20.8° in two axes with a resonant frequency of 559 Hz. It is equipped with a transmission mechanism that can decouple each axis to achieve high linearity; in our study, the nonlinearity error was less than 1°. [ABSTRACT FROM AUTHOR]

In situ nanoindentation is extensively employed for online observing deformation and mechanical behaviors of bio-materials. However, the existing designs of the positioning stages have limited performances for testing soft or hard biomaterials. Consequently, this paper proposes a new structural design of a compliant one degree of freedom (01-DOF) stage with faster response. In addition to a new design, this article applies an analytical method to estimate the kinematic and dynamic behaviors of the stage. Firstly, the 01-DOF stage is designed with two modules, including a displacement amplifier with six levers and a symmetric parallelogram mechanism. Secondly, a kinetostatic diagram of the stage is built by pseudo-rigid-body method. Then, the dynamic equation of the proposed stage is formulated using the Lagrange method. In order to speed up the response of the indentation system, the structural optimization of the stage is conducted via the Firefly algorithm. The results showed that the theoretical first-order resonant frequency is found at about 226.8458 Hz. The theoretical consequences are nearby to the verified simulation. Besides, this achieved frequency of the presented stage is greater than that of previous stages. In an upcoming study, the prototype will be fabricated by additive manufacturing method or a computerized wire cutting method in order to verify the analytical results with experimental results. [ABSTRACT FROM AUTHOR]

A three-legged compliant parallel mechanism (3L-CPM) achieves fully decoupled motions when its theoretical 6 × 6 stiffness/compliance matrix is a diagonal matrix, which only contains diagonal components, while all non-diagonal components are zeros. Because the motion decoupling capability of 3L-CPMs is essential in the precision engineering field, this paper presents the fundamental criteria for designing 3L-CPMs with fully decoupled motions, regardless of degrees-of-freedom and the types of flexure element. The 6 × 6 stiffness matrix of a general 3L-CPM is derived based on the orientation of each flexure element, e.g., thin/slender beam and notch hinge, etc., and its relative position to the moving platform. Based on an analytical solution, several requirements for the flexure elements were identified and needed to be satisfied in order to design a 3L-CPM with a diagonal stiffness/compliance matrix. In addition, the developed design criteria were used to analyze the decoupled-motion capability of some existing 3L-CPM designs and shown to provide insight into the motion characteristics of any 3L-CPM. [ABSTRACT FROM AUTHOR]

Electron beam lithography (EBL) is an important lithographic process of scanning a focused electron beam (e-beam) to direct write a custom pattern with nanometric accuracy. Due to the very limited field of the focused e-beam, a motion stage is needed to move the sample to the e-beam field for processing large patterns. In order to eliminate the stitching error caused by the existing "step and scan" process, we in this paper propose a large range compliant nano-manipulator so that the manipulator and the e-beam can be moved in a simultaneous manner. We also propose an optimized design of the geometric parameters of the compliant nano-manipulator, so that the dimensions and rotational stiffness are suitable for EBL applications in a vacuum environment. Experimental results demonstrate 1 mm × 1 mm travel range with high linearity, ~0.5% cross-axis error and 5 nm resolution. Moreover, the high natural frequency (~56 Hz) of the manipulator facilitates it to achieve high-precision motion of EBL. [ABSTRACT FROM AUTHOR]

This article presents a novel design of monolithic compliant grippers for surgical applications. Compliant mechanisms are jointless mechanism and overcome the major traditional issues such as wear, friction and assembly error. Performance of compliant mechanism depends on the elastic body deformation to transmit motion between the linkages. In this article, the proposed gripper is designed with three different parts with different intended functions: tilting actuator, linear actuator and gripping jaws. Gripping jaws are developed to cut through shearing and collect tissues. A linear actuator transmits the input force to the gripping jaws. A tilting actuator tilts the whole gripper up and down to increase the shear force to cut the tissues. A conceptual mechanism is developed using topology optimisation for these concepts independently. Later, these parts are assembled and developed as a final solid model using SolidWorks. The structural performance of the gripper is investigated thoroughly using finite-element method. [ABSTRACT FROM AUTHOR]

Continuous, smooth, and highly linear displacement output with centimeter-scale stroke and nanometer-scale resolution is greatly attractive for an ultraprecision positioning system. On the foundation of piezoelectric actuation and compliant mechanism, a novel linear piezomotor with minimized backward and nonlinear motion property is designed. Specifically, a driving unit capable of $xy$ -direction decoupling displacement output is proposed to make the generated motion linear, and a flexure mechanism is introduced into the contact part to make the motion output continuous and nonbackward. Combined with double driving units and the flexure contact mechanism, a motion generation strategy is presented. For performing the motion generation strategy well, the kinematics model of the piezomotor is established. Then, the dimension parameters are optimized. After theoretical derivations, the piezomotor is analyzed and evaluated by finite-element analysis simulation. Finally, a proper control waveform is designed, and the motion generation performance tests are successfully carried out. The results uniformly confirm that the proposed piezomotor can output ultraprecision motion with 8-nm resolution and 10-mm stroke in a continuous and smooth manner, and the backward and nonlinear effects are successfully minimized within 100 Hz. [ABSTRACT FROM AUTHOR]

For piezoelectric-driven compliant microgrippers, realizing flexible, stable, and accurate manipulation simultaneously is a key challenge. The bridge-type compliant displacement amplification mechanism (CDAM) with a single input force can enable stable parallel grasping and enlarge the grasping stroke by matching the output performance of typical piezoelectric actuators used in microgrippers. In this study, a nonlinear analysis of the bridge-type CDAM with a single input force was conducted to improve the prediction accuracy of the output displacement, and nonlinear optimization and testing were performed. For the expected and parasitic output displacements, a two-step nonlinear modelling method was proposed to conduct the nonlinear analysis. Using Castigliano's second theorem, small deflection-based finite element analysis (FEA), and numerical fitting, small deflection-based modelling considering the shearing effect was first performed. Then, the correction coefficients for the geometrical nonlinearity were modelled by combining geometrical nonlinear FEA and numerical fitting. By restricting the parasitic output displacement, a nonlinear constraint was derived. Thereafter, geometric parameter optimization and structural optimization of the bridge-type CDAM with a single input force was performed. Model analysis indicates that for the optimal CDAM, the expected output displacement increases with the input force, whereas a negative correlation exists between the growth rate and the input force. Finally, simulations and experimental tests were conducted to verify the effectiveness of the nonlinear models, optimization, and model analysis. • Two-step nonlinear modelling is proposed to predict the displacements of a bridge-type CDAM with a single input force. • A nonlinear constraint is derived to limit the ratio of the parasitic output displacement and the expected one. • For the optimal CDAM, the expected output displacement increases with the input force, whereas the growth rate decreases. • Simulations and experimental tests are performed to verify the effectiveness of the nonlinear models and optimization. [ABSTRACT FROM AUTHOR]

This paper demonstrates a new robust topology design formulation for a compliant sensor structure considering multi-stress performance. Compliant mechanism design is one of the main applications of topology optimization that can be used to achieve displacement or force requirements based on its elastic deformation. Most compliant mechanisms have hinge joints where high stress is observed and this should be carefully considered in the design formulation. In this paper, we investigate a new design formulation that considers multiple stress components for force measurement and structural safety in a compliant mechanism—a wind tunnel balance. An internal wind tunnel balance is a multi-axis force sensor that measures aerodynamic forces and moments during wind tunnel testing. For the axial section of the balance, it is required to have substantial stress reading (sensor performance) by the axial load. In this paper, two stress measures are used in the design formation: (1) local directional stress to meet the sensor performance by a small axial force, and (2) normalized P-norm stress with a relaxation approach to ensure the safety of the balance by a large normal force. The high force ratio between axial and normal forces (1:10 +) is investigated in this paper. In addition, a robust approach is applied to reflect the manufacturing uncertainties from three different projected design variables. The manufacturable blueprint designs using this approach show satisfactory performance with respect to sensing and structural safety. [ABSTRACT FROM AUTHOR]

To overcome a significant challenge in traditional parameterized level set methods based on globally supported radial basis functions, we propose employing a local differentiation construction of radial basis functions using finite difference, a technique previously applied to solving partial differential equations but novel in the context of topology optimization. We present a novel parameterized level set method for structural topology optimization of compliance minimization and compliant mechanism, with the main aim of reducing computational costs associated with fully dense matrices when approximating systems with a large number of collocation points. The new scheme implemented with rectangular mesh elements and polygonal mesh generation accommodates both rectangular and complex design domains. Numerical results are provided to demonstrate the algorithm's effectiveness. • Local meshless radial basis functions are used in level set method for topology optimization. • Gaussian and multiquadric radial basis functions are combined with finite differences. • Compliance minimization and compliant mechanism are solved numerically. • Polygonal meshes are used for complex design domains. • Numerical results show the new parameterized level set method is effective and efficient. [ABSTRACT FROM AUTHOR]

Safe physical interaction is significant for the protection of the operated target during delicate micromanipulation tasks. This paper proposes the concept design of a series-elastic actuator mainly constructed by a fully compliant mechanism. It can reduce the transient contact force when the tip touches an object and monitor the interaction force in real time for safe handling. The rear end of the actuator is a flexible linear guide connected with a voice coil motor to offer a bidirectional displacement. The actuator's front end features a stiffness-switchable mechanism based on folding flexure beams, which provides two-level force buffering and sensing to accommodate varying degrees of contact status. Three strain gauges are integrated into the flexible beam of the mechanism, one of which is used for displacement sensing and the others for monitoring interactive force. After the structural design of the actuator, an analytical model is developed to assess its kinematic performance, which is further verified by finite-element simulation and experimental testing. The experimental results agree with the model and simulation, confirming the effectiveness and reliability of the actuator. The compliant actuator can be applied to some micromanipulation scenarios requiring precision positioning, contact, and interaction at the operating end. • Compliant series-elastic stiffness-switchable actuator is designed. • It reduces the transient impact force during contact with target object. • It senses the contact force by strain gauges for safe handling. • The stiffness-switchable mechanism features two-level buffering. • Effectiveness of the design is verified by simulation and experiment. [ABSTRACT FROM AUTHOR]