A novel stiffness model for a wall-climbing hexapod robot based on nonlinear variable stiffness

In this article, the most contribution is to propose a novel general stiffness model to analyze the stiffness of a wall-climbing hexapod robot. First, we propose a new general stiffness model of serial mechanism, which includes the linear and nonlinear stiffness models. By comparison, the nonlinear stiffness model is a variable stiffness model which introduces the external load force as a variable, obtaining that the nonlinear stiffness model can greatly improve the accuracy of stiffness model than linear stiffness model. Then, the stiffness model of one leg of the robot and the overall stiffness model of the robot are derived based on the general stiffness model. Next, to improve the stiffness of the robot, a new minimum and maximum stiffness are introduced, which provide with effective reference for the selection and optimization of the structural parameters of the robot. Finally, we develop a new wall-climbing hexapod robot based on selection and optimization of the structural parameters, then the experiments are used to show that the selection of structure parameters of the robot effectively improve the stiffness of the robot.

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Nonlinear Stiffness Analysis of Spring-Loaded Inverted Slider Crank Mechanisms With a Unified Model

Journal of Mechanisms and Robotics ◽

10.1115/1.4045649 ◽

2020 ◽

Vol 12 (3) ◽

Author(s):

Zhongyi Li ◽

Shaoping Bai ◽

Weihai Chen ◽

Jianbin Zhang

Keyword(s):

Variable Stiffness ◽

Comprehensive Analysis ◽

Unified Model ◽

Nonlinear Stiffness ◽

Stiffness Analysis ◽

Constant Torque ◽

Stiffness Model ◽

Overall Performance ◽

Crank Mechanism

Abstract A mechanism with lumped-compliance can be constructed by mounting springs at joints of an inverted slider crank mechanism. Different mounting schemes bring change in the stiffness performance. In this paper, a unified stiffness model is developed for a comprehensive analysis of the stiffness performance for mechanisms constructed with different spring mounting schemes. With the model, stiffness behaviors of spring-loaded inverted slider crank mechanisms are analyzed. Influences of each individual spring on the overall performance are characterized. The unified stiffness model allows designing mechanisms for a desired stiffness performance, such as constant-torque mechanism and variable stiffness mechanism, both being illustrated with a design example and experiments.

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Numerical simulation of linear and nonlinear optical properties in heterostructure based on triple Gaussian quantum wells: effects of applied external fields and structural parameters

The European Physical Journal Plus ◽

10.1140/epjp/s13360-021-01907-w ◽

2021 ◽

Vol 136 (8) ◽

Author(s):

H. Dakhlaoui ◽

I. Altuntas ◽

M. E. Mora-Ramos ◽

F. Ungan

Keyword(s):

Numerical Simulation ◽

Optical Properties ◽

Quantum Wells ◽

Nonlinear Optical ◽

Structural Parameters ◽

Nonlinear Optical Properties ◽

External Fields ◽

Linear And Nonlinear

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Motion Simulation of Key Components in a Package Machine

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.557-559.2303 ◽

2012 ◽

Vol 557-559 ◽

pp. 2303-2306

Author(s):

Shu Bin Kan

Keyword(s):

Structural Parameters ◽

Center Of Mass ◽

Motion Simulation ◽

Software Environment ◽

Optimization Result ◽

Adams Software ◽

Motion Characteristic ◽

The Moment ◽

Selection Of

The motion characteristic of key components is a decisional factor to the working reliability and stability of a package machine. In this paper, the motion simulation of a key component is carried out in the ADAMS software environment. By analysis of the force, variance of the center-of-mass and the moment of the component, the mutation point in the motion is found, and then the structure is optimized by selection of different structural parameters. The optimization result shows a significant improvement for the reliability and stability of the whole machine.

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LINEAR AND NONLINEAR INTERSUBBAND REFRACTIVE INDEX CHANGES IN WURTZITEAlGaN/GaNDOUBLE QUANTUM WELLS: EFFECTS OF PIEZOELECTRICITY AND SPONTANEOUS POLARIZATION

Surface Review and Letters ◽

10.1142/s0218625x09012226 ◽

2009 ◽

Vol 16 (01) ◽

pp. 11-17

Author(s):

L. ZHANG

Keyword(s):

Refractive Index ◽

Density Matrix ◽

Quantum Wells ◽

Structural Parameters ◽

Matrix Approach ◽

Third Order ◽

Numerical Result ◽

Analytical Formulas ◽

Index Changes ◽

Linear And Nonlinear

Based on the density-matrix approach and iterative treatment, a detailed procedure for the calculation of the linear and nonlinear intersubband refractive index changes (RICs) in wurtzite GaN-based coupling quantum wells (CQWs) is given. The simple analytical formulas for electronic eigenstates and the linear and third-order nonlinear RICs in the systems are also deduced. Numerical result on a typical AlGaN / GaN CQW shows that the linear and nonlinear RICs sensitively depend on the structural parameters of the CQW system as well as the doped fraction of nitride semicondutor.

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An obstacle-avoiding and stiffness-tunable modular bionic soft robot

Robotica ◽

10.1017/s0263574721001867 ◽

2022 ◽

pp. 1-15

Author(s):

Zhaoyu Liu ◽

Yuxuan Wang ◽

Jiangbei Wang ◽

Yanqiong Fei ◽

Qitong Du

Keyword(s):

Variable Stiffness ◽

Air Pressure ◽

Design Parameters ◽

Soft Robot ◽

Working Pressure ◽

Obstacle Avoiding ◽

Stiffness Model ◽

Pass Through ◽

Soft Actuators

Abstract The aim of this work is to design and model a novel modular bionic soft robot for crawling and crossing obstacles. The modular bionic soft robot is composed of several serial driving soft modules, each module is composed of two parallel soft actuators. By analyzing the influence of working pressure and manufacturing size on the stiffness of the modular bionic soft robot, the nonlinear variable stiffness model of the modular bionic soft robot is established. Based on this model, the spatial states and design parameters of the modular bionic soft robot are discussed when the modular bionic soft robot can pass through the obstacle. Experiments show that when the inflation air pressure of the modular bionic soft robot is 70 kPa, its speed can reach 7.89 mm/s and the height of obstacles passed by it can reach 42.8 mm. The feasibility of the proposed modular bionic soft robot and nonlinear variable stiffness model is verified by locomotion experiments.

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On a CPG-Based Hexapod Robot: AmphiHex-II With Variable Stiffness Legs

IEEE/ASME Transactions on Mechatronics ◽

10.1109/tmech.2018.2800776 ◽

2018 ◽

Vol 23 (2) ◽

pp. 542-551 ◽

Cited By ~ 15

Author(s):

Bin Zhong ◽

Shiwu Zhang ◽

Min Xu ◽

Youcheng Zhou ◽

Tao Fang ◽

...

Keyword(s):

Variable Stiffness ◽

Hexapod Robot

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Optimization of Axial Vibration Attenuation of Periodic Structure With Nonlinear Stiffness Without Addition of Mass

Journal of Vibration and Acoustics ◽

10.1115/1.4047197 ◽

2020 ◽

Vol 142 (6) ◽

Cited By ~ 1

Author(s):

Diego P. Vasconcellos ◽

Marcos Silveira

Keyword(s):

Periodic Structure ◽

Total Mass ◽

Periodic Structures ◽

Original Structure ◽

Dynamical Response ◽

Nonlinear Stiffness ◽

Optimal Position ◽

Simplified Approach ◽

Vibration Attenuation ◽

Linear And Nonlinear

Abstract We explore the vibration attenuation of a periodic structure when one absorber with nonlinear cubic stiffness is included without increasing the total mass. Metastructures, and specifically periodic structures, present interesting characteristics for vibration attenuation that are not found in classical structures. These characteristics have been explored for automotive and aerospace applications, among others, as structures with low mass are paramount for these industries, and keeping low vibration levels in wide frequency range is also desirable. It has been shown that the addition of vibration absorbers in a periodic arrangement can provide vibration attenuation for shock input without increasing the total mass of a structure. In this work, the dynamical response of a metastructure with one nonlinear vibration absorber, with same mass as original structure, optimized for vibration attenuation under harmonic input is compared with a base metastructure without absorbers and a metastructure with linear absorbers via the evaluation of the H2 norm of the frequency response. A simplified approach is used to compare linear and nonlinear stiffness based on deformation energy, by considering linear and nonlinear restoring forces to be equal at mean deformation. The dynamical response of the optimal system is obtained numerically, and an optimization procedure based on sequential quadratic programming (SQP) is proposed to find the optimal position and stiffness coefficients of only one nonlinear absorber, showing that it results in lower level of vibrations than original structure and than structure with linear absorbers, while almost the same level as a structure with all nonlinear absorbers.

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Determination of Variable Stiffness of a Human Elbow for Human-Robot Interaction

Volume 5B: 38th Mechanisms and Robotics Conference ◽

10.1115/detc2014-34420 ◽

2014 ◽

Author(s):

Michael Boyarsky ◽

Megan Heenan ◽

Scott Beardsley ◽

Philip Voglewede

Keyword(s):

Experimental Data ◽

Disturbance Rejection ◽

Variable Stiffness ◽

Important Variable ◽

Human Motion ◽

Human Robot Interaction ◽

Robot Interaction ◽

Constant Stiffness ◽

Stiffness Model ◽

Motor Model

This paper aims to emulate human motion with a robot for the purpose of improving human-robot interaction (HRI). In order to engineer a robot that demonstrates functionally similar motion to humans, aspects of human motion such as variable stiffness must be captured. This paper successfully determined the variable stiffness humans use in the context of a 1 DOF disturbance rejection task by optimizing a time-varying stiffness parameter to experimental data in the context of a neuro-motor Simulink model. The significant improved agreement between the model and the experimental data in the disturbance rejection task after the addition of variable stiffness demonstrates how important variable stiffness is to creating a model of human motion. To enable a robot to emulate this motion, a predictive stiffness model was developed that attempts to reproduce the stiffness that a human would use in a given situation. The predictive stiffness model successfully decreases the error between the neuro-motor model and the experimental data when compared to the neuro-motor model with a constant stiffness value.

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