Showing papers by "Benliang Zhu published in 2019"

A 213-line topology optimization code for geometrically nonlinear structures

Abstract: This paper presents a 213-line MATLAB code for topology optimization of geometrically nonlinear structures. It is developed based on the density method. The code adopts the ANSYS parametric design language (APDL) that provides convenient access to advanced finite element analysis (FEA). An additive hyperelasticity technique is employed to circumvent numerical difficulties in solving the material density-based topology optimization of elastic structures undergoing large displacements. The sensitivity information is obtained by extracting the increment of the element strain energy. The validity of the code is demonstrated by the minimum compliance problem and the compliant inverter problem.

Recent advances in non-contact force sensors used for micro/nano manipulation

Abstract: Micro/nano manipulation for both mechanical and biological structures is currently a popular research field. To protect small-scale structures and acquire their mechanical properties, a micro-scale force sensor is needed. This paper focuses on reviewing the research on non-contact micro-force sensor parts that can be integrated in this manipulation system. The content involves the structure, working principle, resolution and sensitivity of different force sensor parts, including electrical and optical force sensors. The electrical force sensors include piezoresistive, piezoelectric, capacitive, electrothermal and strain gauge-based types; while the optical force sensors focus on but are not restricted to the optical fiber-based force sensors and the vision-based sensing systems. All of these sensors are analysed and compared. Electrical force sensors are currently widely used but are restricted by the sensing properties and size; optical force sensors have high sensitivity, small structure and anti-electromagnetic-interference properties, but they are hardly applied in micro/nano manipulation systems for force measurement. As a result, optical force sensors may become the new generation of sensors that can be integrated with micro/nano manipulation systems.

Effects of Temperature and Residual Stresses on the Output Characteristics of a Piezoresistive Pressure Sensor

Abstract: The effects of temperature on the output performance of piezoresistive pressure sensors are studied in this paper. The influences of the environmental temperature, the residual stress due to the fabrication process, and the residual stress due to the packaging on the piezoresistive coefficient and resistance are theoretically investigated. The simulation results are obtained via finite element analysis through ANSYS. The results of experimental studies performed on piezoresistive pressure sensors fabricated using MEMS techniques are reported to verify the simulation results. The output characteristics of piezoresistive pressure sensors are shown to be substantially affected by not only the environmental temperature but also the residual stresses from the fabrication and packing processes.

Origami Kaleidocycle-Inspired Symmetric Multistable Compliant Mechanisms

Abstract: Compliant kaleidocycles can be widely used in a variety of applications, including deployable structures, origami structures, and metamorphic robots, due to their unique features of continuous rotatability and multistability. Inspired by origami kaleidocycles, a type of symmetric multistable compliant mechanism with an arbitrary number of units is presented and analyzed in this paper. First, the basic dimension constraints are developed based on mobility analysis using screw theory. Second, the kinematic relationships of the actual rotation angle are obtained. Third, a method to determine the number of stabilities and the position of stable states, including the solution for the parameterized boundaries of stable regions, is developed. Finally, experimental platforms are established, and the validity of the proposed multistable mechanisms is verified.

Nonlinear topology optimization of parallel-grasping microgripper

Abstract: This paper presents a piezo-driven microgripper which can realize parallel grasping in a large displacement range (more than 140 μ m ). The proposed microgripper is derived by a two-step nonlinear topology optimization method. A conventional linear topology optimization problem with loose boundary condition is solved first, and its solution is used as the initial design domain of the following nonlinear topology optimization. The comparison of the convergence results shows that this method can find a better structure of microgripper and save computation time simultaneously. Both the finite element analysis and experiment are used to verify the performance of the proposed microgripper. The experimental results show that the parasitic movement of the jaw is only 0.299 % of the grasping movement and the average inclination angle of the jaw is 0.055mrad/ μ m . A pair of strain gages is integrated as a displacement sensor, and its performance is presented and verified by experiments.

Online Precise Motion Measurement of 3-DOF Nanopositioners Based on Image Correlation

Abstract: Fast and accurate measuring motion with multi-degrees-of-freedom (multi-DOFs) and high resolution has been highly demanded in the development of nanopositioning systems in recent years. This paper develops an efficient and practical image correlation method capable of measuring micromotions of the planar 3-DOF ( $x,y,\theta _{z}$ ) nanopositioners. In this method, the measurement of 3-DOF micromotion is first transformed into a problem of three-variable optimization by utilizing the correlation function of sum of squared difference. Subsequently, an optimal algorithm based on the inverse compositional Gaussian–Newton searching is developed to instantaneously solve these three variables. Simulation results show that in the image space, accuracy of translational components ( $x$ , $y$ ) and rotation component ( $\theta _{Z}$ ) of the proposed algorithm can reach to 0.02 pixels and 0.01°, respectively. Experimental results demonstrate that the proposed method can realize real-time motion tracking of a 3-DOF nanopositioner with the performance similar to commonly used multicapacitive sensor scheme.

Design of Planar Large-Deflection Compliant Mechanisms With Decoupled Multi-Input-Output Using Topology Optimization

Abstract: This paper presents a method for topology optimization of large-deflection compliant mechanisms with multiple inputs and outputs by considering the coupling issue. First, the objectives of the design problem are posed by modeling the output loads using several springs to enable control of the input–output behavior. Second, a scheme is proposed to obtain a completely decoupled mechanism. Both input coupling and output coupling are considered. Third, with the implementation of an energy interpolation scheme to stabilize the numerical simulations, the geometrical nonlinearity is considered to appropriately capture the large displacements of compliant mechanisms. Finally, several numerical examples are presented to demonstrate the validity of the proposed method. Comparison studies with the obtained results without considering the coupling issues are also presented.

Topological and Shape Optimization of Flexure Hinges for Designing Compliant Mechanisms Using the Level Set Method

Abstract: A flexure hinge is a major component in designing compliant mechanisms that offers unique possibilities in a wide range of application fields in which high positioning accuracy is required. Although various flexure hinges with different configurations have been successively proposed, they are often designed based on designers’ experiences and inspirations. This study presents a systematic method for topological optimization of flexure hinges by using the level set method. Optimization formulations are developed by considering the functional requirements and geometrical constraints of flexure hinges. The functional requirements are first constructed by maximizing the compliance in the desired direction while minimizing the compliances in the other directions. The weighting sum method is used to construct an objective function in which a self-adjust method is used to set the weighting factors. A constraint on the symmetry of the obtained configuration is developed. Several numerical examples are presented to demonstrate the validity of the proposed method. The obtained results reveal that the design of a flexure hinge starting from the topology level can yield more choices for compliant mechanism design and obtain better designs that achieve higher performance.

Topological design of compliant orthogonal displacement amplification mechanism under the unidirectional input force

Abstract: The orthogonal displacement amplification mechanism is used to output and amplify the displacement perpendicular to the direction of the input force, and its configuration often uses a typical bridge-type. However, the bridge-type amplifier to achieve orthogonal shift conversion must enter the bidirectional symmetric input forces, otherwise the output will produce parasitic displacement. In view of this problem, the topology optimization method is used to find the new configuration of the displacement amplification mechanism, so that it can still realize the orthogonal displacement transformation under the unidirectional input force condition. Based on the solid isotropic material with penalization (SIMP) topological description method, the ratio of output and input displacements is maximized as the objective function, the ratio of parasitic displacement and output displacement as one of constraint functions, and the topological optimization mathematical model of the compliant orthogonal displacement amplifier is established under the unidirectional input force. The sensitivity information of the objective and constraint functions is deduced by the adjoint matrix method, and the optimization problem is solved by the method of moving asymptotes (MMA). The topology optimization results of orthogonal displacement amplifier are given through numerical examples, and the effect of spring stiffness on the topology optimization result is also discussed. Finally, the parasitic motions of the displacement amplification mechanism obtained from topology optimization and the bridge-type amplification mechanism are compared through the finite element analysis and experiment. Finite element simulation and experiment confirm the correctness and validity of the proposed method.

A Novel Reconfigurable Wheel-Legged Mobile Mechanism

Abstract: This paper presents a novel wheel-legged mobile robot with a reconfigurable frame, which uses a compliant kaleidocycles inspired spring-hinged eight-bar mechanism. The kinematic model of the mechanism is established and the relationships between actual rotation angle and the joint angles is thoroughly obtained in the spherical coordinate system. According to the analysis of the multivariable potential energy surface, the relationship among multistable performance, under-actuated behavior and potential mechanism energy is studied. On account of under-actuated kinematic relationship and multistability of the proposed mechanism, a cable-driven approach is used and its feasibility is finally verified by the experiment of the prototype robot.

Planar complex structural space and large stroke type lamina emergent torsional joint

Abstract: The invention discloses a planar complex structural space and large stroke type lamina emergent torsional joint. The planar complex structural space and large stroke type lamina emergent torsional joint comprises a rectangular plane unit for realizing out-of-plane twisting function, and a fork-shaped plane unit for realizing in-plane rotating function, wherein the fork-shaped plane unit is of a fork-shaped structure which is formed by intersecting two flexible straight-beam thin sheets, and the fork-shaped structure is provided with an included angle; and the rectangular plane unit and the fork-shaped plane unit are connected in an outer linking manner or an embedding manner. The planer complex structural space and large stroke type lamina emergent torsional joint overcomes problems of anexisting planar structural lamina emergent torsional joint, such as that the existing planar structural lamina emergent torsional joint is equivalent to a single-degree-of-freedom large stroke low movement pair, an LEMs (Lamina Emergent Mechanisms) are equivalent to a multi-degree-of-freedom lamina emergent torsional joint, and the overall stroke is small

Topological Synthesis of Compliant Mechanisms Using a Level Set-Based Robust Formulation

Abstract: Topology optimized compliant mechanisms have been widely utilized as the microdevices in microelectromechanical system. In applying topology optimization to design compliant mechanisms, one of the longstanding problems is that the obtained mechanisms often have highly localized compliance regions which make them very difficult to fabricate. In order to obtain manufacturable topology optimized compliant mechanisms, this paper presents a robust formulation based on the level set method. In the formulation, the goal is to maximize the objective for the worst case of three different structural configurations which are represented by three different level set functions. Not only the formulation can eliminate the highly localized compliance regions, it also can precisely control the minimum length scale in the obtained mechanisms. The validity and different aspects of the proposed formulation are demonstrated on several benchmark problems.

Multistable compliant mechanism and stability state analysis method thereof

Abstract: A multistable compliant mechanism and a stability state analysis method thereof. The multistable compliant mechanism is formed by sequentially connecting a plurality of basic units (101) end to end, so as to form a closed annular structure (1). Each basic unit (101) comprises two flexible hinge portions (102, 103) perpendicular to each other on different planes, and two rigid connecting portions (104, 105) for connecting the flexible hinge portions (102, 103). The two flexible hinge portions (102, 103) are connected via one of the rigid connecting portions (104) disposed therebetween, and one of the flexible hinge portions (103) is connected to a flexible hinge portion (102) of an adjacent basic unit (101) via the other rigid connecting portion (105). The lengths of two rigid connecting portions (104, 105) in the same basic unit (101) must be equal, but the lengths of rigid connecting portions (104, 105) in different basic units are not necessarily equal.