Variable stiffness characteristics of embeddable multi-stable composites

2014 ◽  
Vol 97 ◽  
pp. 12-18 ◽  
Author(s):  
Andres F. Arrieta ◽  
Izabela K. Kuder ◽  
Tobias Waeber ◽  
Paolo Ermanni
Keyword(s):  
Variable Stiffness ◽  
Stiffness Characteristics

scholarly journals Spring Effects on Workspace and Stiffness of a Symmetrical Cable-Driven Hybrid Joint

Symmetry ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 101 ◽  
Author(s):  
Shan Zhang ◽  
Zheng Sun ◽  
Jili Lu ◽  
Lei Li ◽  
Chunlei Yu ◽  
...  
Keyword(s):  
Variable Stiffness ◽  
Robotic Manipulator ◽  
Spring Model ◽  
Cable Tension ◽  
Stiffness Analysis ◽  
Hybrid Joint ◽  
Compression Spring ◽  
Spring Force ◽  
Basic Parameters ◽  
Stiffness Characteristics

This paper aims to investigate how to determine the basic parameters of the helical compression spring which supports a symmetrical cable-driven hybrid joint (CDHJ) towards the elbow joint of wheelchair-mounted robotic manipulator. The joint design of wheelchair-mounted robotic manipulator needs to consider lightweight but robust, workspace requirements, and variable stiffness elements, so we propose a CDHJ which becomes a variable stiffness joint due the spring under bending and compression provides nonlinear stiffness characteristics. Intuitively, different springs will make the workspace and stiffness of CDHJ different, so we focus on studying the spring effects on workspace and stiffness of CDHJ for its preliminary design. The key to workspace and stiffness analysis of CDHJ is the cable tension, the key to calculate the cable tension is the lateral bending and compression spring model. The spring model is based on Castigliano’s theorem to obtain the relationship between spring force and displacement. The simulation results verify the correctness of the proposed spring model, and show that the spring, with properly chosen parameters, can increase the workspace of CDHJ whose stiffness also can be adjusted to meet the specified design requirements. Then, the modelling method can be extended to other cable-driven mechanism with a flexible compression spring.

scholarly journals Conceptual mechanical design of antagonistic variable stiffness joint based on equivalent quadratic torsion spring

2020 ◽  
Vol 103 (3) ◽  
pp. 003685042094129
Author(s):  
Jishu Guo
Keyword(s):  
Degrees Of Freedom ◽  
Modular Design ◽  
Angular Displacement ◽  
Variable Stiffness ◽  
Human Robot Interaction ◽  
Design Calculation ◽  
Robot Arm ◽  
Compact Structure ◽  
Torsion Spring ◽  
Stiffness Characteristics

The variable stiffness joint is a kind of flexible actuator with variable stiffness characteristics suitable for physical human–robot interaction applications. In the existing variable stiffness joints, the antagonistic variable stiffness joint has the advantages of simple implementation of variable stiffness mechanism and easy modular design of the nonlinear elastic element. The variable stiffness characteristics of antagonistic variable stiffness joints are realized by the antagonistic actuation of two nonlinear springs. A novel design scheme of the equivalent nonlinear torsion spring with compact structure, large angular displacement range, and desired stiffness characteristics is presented in this article. The design calculation for the equivalent quadratic torsion spring is given as an example, and the actuation characteristics of the antagonistic variable stiffness joint based on the equivalent quadratic torsion spring are illustrated. Based on the design idea of constructing the antagonistic variable stiffness joint with compact structure and high compliance, as well as the different design requirements of the joints at different positions of the multi–degrees of freedom robot arm, nine types of mechanical schemes of antagonistic variable stiffness joint with the open design concept are proposed in this article. Finally, the conceptual joint configuration schemes of the robot arm based on the antagonistic variable stiffness joint show the application scheme of the designed antagonistic variable stiffness joint in the multi–degrees of freedom robot.

The Dynamic Strength Calculation on the Reel Fulcrum of Crane Based on ADAMS and FEA

2014 ◽  
Vol 599-601 ◽  
pp. 551-554 ◽  
Author(s):  
Feng Qi Wu
Keyword(s):  
System Dynamics ◽  
Dynamic Strength ◽  
Variable Stiffness ◽  
Virtual Prototype ◽  
Wire Rope ◽  
Dynamics Model ◽  
Coupling Force ◽  
Simulation Results ◽  
The Wire ◽  
Stiffness Characteristics

Based on the multi-body system dynamics in the ADAMS environment, a virtual prototype of the reel fulcrum of crane was developed. In this model, the whole system was disassembled lifting mechanism system with flexible body dynamics model of the wire rope. The virtual running environment was established according to the actual crane operation cases, which is designed the hanging & lifting working process. It is the key step to build the reel fulcrum dynamics model for performance analysis of system dynamics, which is the basis for the optimize design of the reel fulcrum of crane. Theoretical model analysis usually does not consider the coupling force status of the reel fulcrum of crane. It is a steady-state analysis to the reel fulcrum of crane models. These models have played an important role in the assessment of the reel fulcrum of crane performance and the system parameters, but do not reveal the interaction of the reel fulcrum of crane and the wire rope, which fail to be a comprehensive understanding practical system dynamics characteristic. Virtual prototype simulation results will be applied to prototype design and evaluation, and save a lot of manpower and material resources. At the same time,the method has an advantage for dynamics analysis to simulating some dangerous movement conditions, which is hard to be replayed or simulated at the test actual working condition site. In particular, some cases cannot be recurrence in the accident handling process. The simulation results show that the response value. Variable stiffness characteristics of wire rope of hoisting mechanism are implemented successfully through discrete multiple rigid body being applied to the wire rope in this paper. The establishment of the Reel fulcrum dynamic model is based on ADAMS, which realizes the reel fulcrum of crane system coupling modeling. These results show that the model reflects the actual dynamics of the reel fulcrum of crane, and also presents that some of the theoretical analysis results cannot be usually confirmed.

Hybrid modeling and analysis of multidirectional variable stiffness of the linear rolling guideway under combined loads

2020 ◽  
Vol 234 (13) ◽  
pp. 2716-2727
Author(s):  
Lei Yang ◽  
Lei Wang ◽  
Wanhua Zhao
Keyword(s):  
Machine Tool ◽  
High Speed ◽  
Complex Loading ◽  
Variable Stiffness ◽  
Time Varying ◽  
Modeling And Analysis ◽  
Combined Loads ◽  
Machine Tool Structure ◽  
High Feed ◽  
Stiffness Characteristics

In the working process of high-speed multiaxis machine tools, inertial loads due to high feed acceleration and time-varying gravity loads due to changing configuration of multiaxis structure result in time-varying complex loads applied to linear rolling guideway. Existing models cannot efficiently represent the effect of complex loads on multidirectional stiffness variation of linear rolling guideway. In this paper, a hybrid model of multidirectional stiffness of linear rolling guideway and the solving algorithm are proposed. The complex loading conditions of linear rolling guideway in high-speed multiaxis machine tool structure are considered. And contact flexibilities between rolling balls and grooves are modeled with the effect of elastic deformations of runner block and rail. The proposed model can calculate the multidirectional stiffness with high accuracy. Meanwhile the differences between the stiffness characteristics in different directions are represented correctly. The variations of multidirectional stiffness of linear rolling guideway under time-varying combined loads are analyzed. This study provides an effective way to comprehensively evaluate the stiffness characteristics of linear rolling guideway which can contribute to the dynamic analysis and active design of high-speed machine tool structure.

scholarly journals Elastic Actuator Design Based on Bending of Cylindrical Beam for Robotic Applications

Actuators ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 80
Author(s):  
Reis Murat ◽  
Nafiseh Ebrahimi ◽  
Amir Jafari
Keyword(s):  
High Performance ◽  
Low Cost ◽  
Variable Stiffness ◽  
Circular Disk ◽  
Torsional Stiffness ◽  
Steel Beams ◽  
Elastic Coupling ◽  
Stiffness Characteristics ◽  
Living Organisms ◽  
Mechanical Devices

The lack of suitable actuators has hampered the development of high-performance machines or robots that can compete with living organisms in terms of motion, safety, and energy efficiency. The adaptation properties of biological systems to environmental variables—for example, the control performance of biological muscle with variable stiffness properties—exceeds the performance of mechanical devices. The variable stiffness characteristics of elastic actuators are different from the operating principle of conventional solids. Although there has been a lot of work on the design of elastic actuators in recent years, a low-cost and compact elastic actuator that can be used in place of standard rigid servo actuators is not yet available. In this study, a standard servo motor has been transformed into an elastic actuator by an elastic coupling attached to the gear system. The elastic coupling consists of four small steel beams with a cylindrical cross section placed on the circular disk, and the stiffness of the actuator is adjusted by varying the clutch length of the cylindrical beams. In this study, this innovative design is explained, then the equations expressing the variation of the torsional stiffness of the cylindrical beams with the coupling length and solutions of these equations are given. The experimental results are presented to show the ability of the proposed actuator to control position and regulate the stiffness independently.

scholarly journals Novel Design and Modeling of a Soft Pneumatic Actuator Based on Antagonism Mechanism

Actuators ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 107
Author(s):  
Yinglong Chen ◽  
Junhao Zhang ◽  
Yongjun Gong
Keyword(s):  
Mechanical Characteristics ◽  
Artificial Muscle ◽  
Variable Stiffness ◽  
Pneumatic Artificial Muscle ◽  
Human Machine Interaction ◽  
Soft Actuator ◽  
Stiffness Characteristics ◽  
Machine Interaction ◽  
Novel Design ◽  
Compound Action

The soft actuator possesses the characteristics of flexibility, environmental adaptability, and human–machine interaction. Firstly, aiming to resolve the limitation of variable stiffness performance of a traditional pneumatic artificial muscle (PAM) actuator, based on the antagonistic mechanism of extensor and contractor muscles, a novel pneumatic soft actuator coupled of extensor and contractor muscles is proposed in this paper. The actuator can perform the compound action of elongation/contraction, and the stiffness of it can be controlled by adjusting the elongation and contraction forces. Secondly, based on the deformation principle of woven and elastic fabric layers, the mechanical characteristics model of the actuator is established and simulated. The mechanical properties of the actuator are tested under different pressures and deformation displacement and the variable stiffness characteristics of the actuator are verified. Finally, actuators are utilized to manufacture a soft mechanical manipulator, which can achieve variable stiffness in a fixed bending attitude.

scholarly journals ALLOWANCE FOR THE SHEAR WHEN CALCULATING SHIPBOARD BEAMS BEARING INTENSIVE LOCALY DISTRIBUTED LOADS

2018 ◽  
pp. 7-16
Author(s):  
Evgeny Petrovich Burakovskiy ◽  
Pavel Evgenievich Burakovskiy
Keyword(s):  
Minimum Weight ◽  
Variable Stiffness ◽  
Local Loads ◽  
Elastic Plastic ◽  
Ship Hulls ◽  
Limit Value ◽  
Shear Effects ◽  
Stiffness Characteristics ◽  
Effect Of The Support ◽  
The Impact

In the process of operation, shipboard beams are subjected to the impact of various types of loads, the greatest danger being intense local distributed loads which are the main cause of damage to ship hulls. Therefore, designing ship hulls with minimum weight characteristics, as well as choosing the optimum sizes of connections when reinforcing the beams, require to use methods for calculating hull structures under the action of local loads beyond the elastic limit. The paper presents design models that allow taking into account shear effects in the beam walls, as well as the effect of the support forces on elastic-plastic base on their deformation. These problems can be avoided, if the sector of the frame on which shearing force has reached the limit value can be replaced by an ideal cable lying on the elastic-plastic base with variable stiffness characteristics. The results of the calculation of the shipboard beams have been compared using the described approach and the method of "instantaneous variation of bending parameters". It is shown that for large deflections the discrepancy is insignificant, which is explained by the dominant influence of the support forces on the side skin and longitudinal forces on the behavior of locally loaded frames. The proposed technique allows taking into account the impact of shear effects on deformation of locally loaded frames, which can be used in design and modernization of ship hulls to select the optimum sizes of connections.

Modeling and Analysis of Fixel Designs for Micromanufacturing Active Fixturing

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Troy B. Rippere ◽  
Koustubh J. Rao ◽  
Gloria J. Wiens
Keyword(s):  
Manufacturing Systems ◽  
Compliant Mechanisms ◽  
Variable Stiffness ◽  
Theoretical Models ◽  
Milling Process ◽  
Contact Forces ◽  
Modeling And Analysis ◽  
Design Alternatives ◽  
Expected Performance ◽  
Stiffness Characteristics

This paper presents an investigation of fixel design alternatives for active (dynamic) fixturing to be incorporated into mesoscale manufacturing systems. Using simple compliant mechanisms and components, fixels exhibiting mechanically adjustable stiffness characteristics are achievable. Via manual or automated stiffness adjustments, these fixels provide functionality for enabling greater control of the dynamic response of the workpiece subject to vibrations and/or variations in contact forces at the tool-workpiece-fixture interface. To quantify the fixel functionality, this paper presents theoretical models of the stiffness characteristics expressed as a function of the mechanical variable(s), thus forming a basis for exploring the adjustability in stiffness achievable for each fixel design. Also presented are results of the dynamic behavior of the active fixturing implemented in a milling process based on a “regenerative force, dynamic deflection model” augmented with the active fixturing variable stiffness model and inclusion of tool runout. These simulation results indicate the expected performance of the active fixturing upon its implementation in actual fixturing for the creation of micron features on micro- and macroparts.

scholarly journals Research on Variable-Stiffness Mechanisms of Robot Wrists for Compliant Assembling-Clamping

2021 ◽  
Author(s):  
Kangkang Li ◽  
Pu Xing ◽  
Xu-Kun Zhang ◽  
Qing-Guo Xia
Keyword(s):  
Degrees Of Freedom ◽  
Variable Stiffness ◽  
Geometrical Parameters ◽  
Robot Wrist ◽  
Stiffness Variation ◽  
Low Stiffness ◽  
Stiffness Characteristics ◽  
Wrist Stiffness ◽  
Stiffness Distribution

Abstract The stiffness requirements of robot wrists vary with processes during automatic assembling-clamping of robots. The precision of robots moving workpieces to operating positions in the process of rigid localization is achieved if robot wrists equip with a large stiffness. The pose errors of workpieces in the process of compliant assembling-clamping can easily be compensated if robot wrists with a low stiffness is utilized. The present compliant wrist can not meet the stiffness requirements of different processes. A robot wrist with a large stiffness variation is proposed and its mechanisms of rigid localization and compliant assembling-clamping are studied. The pose models of wrists caused by deformations are established. The influences of wrist stiffness on the deformation of itself are researched. The mechanism of modulating wrist stiffness during compliant assembling-clamping is revealed. A structure of 3-DOF (degrees of freedom) robot wrist with a stiffness variation is proposed. The wrist stiffness is changed by modulating the pretension. The influences of pretensions and geometrical parameters on the variable-stiffness characteristics and the stiffness distribution of a wrist are researched. Finally, the experiments are carried out to verify the feasibility of the wrists finishing assembling-clamping operations by modulating the stiffness.

Sign in / Sign up

Export Citation Format

Share Document