scholarly journals Study on trunk posture support device utilizing variable stiffness characteristics by pneumatic soft actuator

2021 ◽  
Author(s):  
Hayato YASE ◽  
Daisuke SASAKI ◽  
Jun KADOWAKI ◽  
Takumi YASUHARA
Keyword(s):  
Variable Stiffness ◽  
Soft Actuator ◽  
Trunk Posture ◽  
Support Device ◽  
Stiffness Characteristics

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 Fully-Printable Soft Actuator with Variable Stiffness by Phase Transition and Hydraulic Regulations

Actuators ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 269
Author(s):  
Tingchen Liao ◽  
Manivannan Sivaperuman Kalairaj ◽  
Catherine Jiayi Cai ◽  
Zion Tsz Ho Tse ◽  
Hongliang Ren
Keyword(s):  
Transition Period ◽  
Shape Memory Polymer ◽  
Variable Stiffness ◽  
Pressure Variation ◽  
Soft Actuator ◽  
Output Force ◽  
Load Carrying ◽  
Force Variation ◽  
Stiffness Variation ◽  
Short Transition

Actuators with variable stiffness have vast potential in the field of compliant robotics. Morphological shape changes in the actuators are possible, while they retain their structural strength. They can shift between a rigid load-carrying state and a soft flexible state in a short transition period. This work presents a hydraulically actuated soft actuator fabricated by a fully 3D printing of shape memory polymer (SMP). The actuator shows a stiffness of 519 mN/mm at 20 ∘C and 45 mN/mm at 50 ∘C at the same pressure (0.2 MPa). This actuator demonstrates a high stiffness variation of 474 mN/mm (10 times the baseline stiffness) for a temperature change of 30 ∘C and a large variation (≈1150%) in average stiffness. A combined variation of both temperature (20–50 ∘C) and pressure (0–0.2 MPa) displays a stiffness variation of 501 mN/mm. The pressure variation (0–0.2 MPa) in the actuator also shows a large variation in the output force (1.46 N) at 50 ∘C compared to the output force variation (0.16 N) at 20 ∘C. The pressure variation is further utilized for bending the actuator. Varying the pressure (0–0.2 MPa) at 20 ∘C displayed no bending in the actuator. In contrast, the same variation of pressure at 50 ∘C displayed a bending angle of 80∘. A combined variation of both temperature (20–50 ∘C) and pressure (0–0.2 MPa) shows the ability to bend 80∘. At the same time, an additional weight (300 g) suspended to the actuator could increase its bending capability to 160∘. We demonstrated a soft robotic gripper varying its stiffness to carry objects (≈100 g) using two individual actuators.

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.

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 Soft Actuator Model for a Soft Robot With Variable Stiffness by Coupling Pneumatic Structure and Jamming Mechanism

IEEE Access ◽  
2020 ◽  
Vol 8 ◽  
pp. 26356-26371 ◽  
Author(s):  
Feng-Yu Xu ◽  
Feng-You Jiang ◽  
Quan-Sheng Jiang ◽  
Yu-Xuan Lu
Keyword(s):  
Variable Stiffness ◽  
Soft Robot ◽  
Soft Actuator

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.

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