Design of a parallel compliance device with variable stiffness

2020 ◽  
pp. 095440622093259
Author(s):  
Yong Zhao ◽  
Kunyong Chen ◽  
Jue Yu ◽  
Shunzhou Huang
Keyword(s):  
Mechanical Characteristics ◽  
Variable Stiffness ◽  
Spring Stiffness ◽  
Synthesis Algorithm ◽  
Stiffness Properties ◽  
Linear Spring ◽  
Endpoint Stiffness ◽  
Stiffness Adjustment ◽  
Translational Stiffness

This paper presents a parallel compliance device with variable translational stiffness properties. The variation of endpoint stiffness depends on the change of the spring stiffness in each limb. A synthesis algorithm for realizing the desired force compliance performance is built. Based on the proposed algorithm, a group of optimal spring stiffness can be derived. For the implementation of this device, an electromagnetic linear spring with current-controlled stiffness is developed. After testing the mechanical characteristics of the electromagnetic spring, a prototype of the parallel compliance device is built. The endpoint stiffness under different combinations of spring stiffness values is exhibited in the form of stiffness ellipsoids. A case is studied and verifies the ability of the presented compliance device to realize the desired endpoint stiffness. As the stiffness adjustment range of electromagnetic spring is limited, the bound of physically realizable stiffness of the presented compliance device is also discussed.

A novel variable stiffness mechanism with linear spring characteristic for machining operations

Robotica ◽  
2016 ◽  
Vol 35 (7) ◽  
pp. 1627-1637 ◽  
Author(s):  
Ngoc-Dung Vuong ◽  
Renjun Li ◽  
Chee-Meng Chew ◽  
Amir Jafari ◽  
Joseph Polden
Keyword(s):  
Energy Efficient ◽  
Mechanical Design ◽  
Variable Stiffness ◽  
Stiffness Properties ◽  
Pros And Cons ◽  
Linear Spring ◽  
Working Principle ◽  
Machining Operations ◽  
Novel Design

SUMMARYVariable stiffness mechanisms are able to mechanically reconfigure themselves in order to adjust their system stiffness. It is generally accepted that only antagonistic designs, featuring quadratic springs, can produce linear spring-like behaviour (i.e., a linear relationship between the displacement and its resultant force). However, these antagonistic designs typically are not as energy efficient as series-based designs. In this work, we propose a novel variable stiffness mechanism that can achieve both linear-spring behaviour whilst maintaining an energy efficient characteristic. This paper will present the working principle, mechanical design and characterization of the joints stiffness properties (verified via experimental procedure). The pros and cons of this novel design with reference to the other Variable Stiffness Actuator (VSA) designs will be discussed based on experimental results and in the context of general machining tasks.

A stiffness adjustment mechanism maximally utilizing elastic energy of a linear spring for a robot joint

2015 ◽  
Vol 29 (20) ◽  
pp. 1331-1337 ◽  
Author(s):  
M. Uemura ◽  
K. Matsusaka ◽  
Y. Takagi ◽  
S. Kawamura
Keyword(s):  
Elastic Energy ◽  
Adjustment Mechanism ◽  
Linear Spring ◽  
Stiffness Adjustment

scholarly journals Analysis of Stiffness and Energy Consumption of Nonlinear Elastic Joint Legged Robot

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Dongliang Chen ◽  
Jindong Zhang ◽  
Xutao Weng ◽  
Yunjian Zhang ◽  
Zhonghui Shi
Keyword(s):  
Energy Consumption ◽  
Variable Stiffness ◽  
Legged Robot ◽  
Spring Stiffness ◽  
Simulation Experiments ◽  
Torsion Spring ◽  
Elastic Joint ◽  
Output Torque ◽  
Nonlinear Elastic ◽  
Elastic Unit

In order to reduce the energy consumption of the legged robot in walking, this paper designs a kind of nonlinear elastic joint from the flexible variable-stiffness joint based on the mammal walking on the limb and optimizes the leg structure of the legged robot. The motor is rigidly connected to the articulated lever. When the lever is accelerated or decelerated, the elastic unit is introduced. The system can be considered as a special variable-rate elastic system. This paper will study it from theory and simulation experiments. Based on the dynamic analysis, a functional relationship between the output torque and the torsion spring stiffness and between the energy consumption and the torsion spring stiffness was established. By finding the extremum, the two optimum torsional spring stiffness that can minimize the required output average torque and the energy consumed during one cycle of motion were deduced. The results show that using this design in a reasonable position can effectively reduce the energy consumption of the system and can achieve up to a 50% reduction in energy consumption.

scholarly journals 1A1-C01 Variable Stiffness Unit Using Component of Force of Linear Spring

2008 ◽  
Vol 2008 (0) ◽  
pp. _1A1-C01_1-_1A1-C01_2
Author(s):  
Naoyuki TAKESUE ◽  
Raizo KOSAKA ◽  
Hideo FUJIMOTO
Keyword(s):  
Variable Stiffness ◽  
Linear Spring

Probabilistic Elastic Element Design for Robust Natural Dynamics of Structure-Controlled Variable Stiffness Actuators

2017 ◽  
Vol 10 (1) ◽  
Author(s):  
Florian Stuhlenmiller ◽  
Jochen Schuy ◽  
Philipp Beckerle
Keyword(s):  
Elastic Element ◽  
Material Selection ◽  
Probabilistic Approach ◽  
Design Procedure ◽  
Variable Stiffness ◽  
Actuation System ◽  
Lumped Parameter ◽  
Stiffness Properties ◽  
Natural Dynamics ◽  
Variable Stiffness Actuators

This paper proposes a probabilistic approach for the design of elastic elements to be used in structure-controlled variable stiffness actuators (VSA) for robotic applications. Considering the natural dynamics of the elastic actuation system, requirements are defined and material selection as well as geometry calculation are performed using lumped parameter models. Monte Carlo simulations are integrated in the design procedure to ensure a robust implementation of the required dynamical characteristics. Thereby, effects of uncertainties that might be caused by manufacturing or deviations of material properties are taken into account. To validate the suitability of the overall approach and the particular methods, a torsional elastic element is implemented and experimentally evaluated. The evaluation shows a fulfillment of the key requirements, i.e., specific natural dynamic behavior, that is only achieved due to considering uncertainties. Further, the transferability of the approach to other structure-controlled elastic actuators is discussed and implications are given. Only the governing equations of stiffness properties in certain load situation need to be adapted, e.g., from torsion to bending. Due to the simple transfer, the proposed probabilistic and model-based approach is promising for application to various actuator concepts with structure-controlled variable stiffness.

scholarly journals Comparative study on stiffness properties of WOODCAST and conventional casting materials

2012 ◽  
Vol 37 (4) ◽  
pp. 336-339 ◽  
Author(s):  
Eija Pirhonen ◽  
Antti Pärssinen ◽  
Mika Pelto
Keyword(s):  
Mechanical Properties ◽  
Comparative Study ◽  
Clinical Relevance ◽  
Variable Stiffness ◽  
Clinical Use ◽  
Plaster Of Paris ◽  
Synthetic Materials ◽  
Stiffness Properties ◽  
Materials Used ◽  
Cylindrical Samples

Background and Aim: Plaster-of-Paris and synthetic materials (e.g. fibreglass) have been in clinical use as casting materials for decades. An innovative casting material, WOODCAST, brings interesting alternatives to the traditional materials. The aim of this study was to compare the stiffness properties of the WOODCAST material to traditional casting materials. Technique: In immobilization by casting, materials with variable stiffness properties are required. Ring stiffness of cylindrical samples correlates well with cast rigidity. Discussion: For load-bearing structures, the use of the WOODCAST Splint is recommended as equally high stiffness was obtained with the WOODCAST Splint as was with fibreglass. The WOODCAST 2 mm product is optimal for structures where some elasticity is required, and WOODCAST Ribbon can be used in any WOODCAST structure where further reinforcement is needed. The results show that WOODCAST material can be used in replacing traditional casting materials used in extremity immobilization. Clinical relevance The mechanical properties of casting material play an important role in safe and effective fracture immobilization. Stiffness properties of the WOODCAST casting material and conventional materials – fibreglass and plaster-of-Paris – were analysed in this study. The WOODCAST Splint appears to compare favorably with traditional materials such as Scotchcast.

A New Seismic-Isolation Device Applied in Continuous Beam Bridge

2011 ◽  
Vol 194-196 ◽  
pp. 2008-2013
Author(s):  
Bin Yan
Keyword(s):  
Seismic Performance ◽  
Seismic Isolation ◽  
Viscous Damper ◽  
Continuous Beam ◽  
Spring Stiffness ◽  
Continuous Beam Bridge ◽  
Linear Spring ◽  
Meizoseismal Area ◽  
Isolation Device ◽  
Beam Bridge

Continuous beam bridge was widely used, while seismic problem of it was prominent in meizoseismal area. According to seismic-isolation principle and mechanism of PSD, seismic performance of PSD were studied and the parameters of PSD were analyzed later, based on south approach of North Branch of Xia-Zhang Sea-Crossing Bridge. It was found that PSD, a combination of preloaded spring and liquid viscous damper, was an effective seismic-isolation device which could significantly reduce the seismic response of continuous beam bridge in longitudinal and transverse direction. Damper coefficient was the main parameter of PSD, while preloaded force, linear spring stiffness and damper index had a little effect on seismic performance of PSD.

Improved Feasible Load Range and Its Effect on the Frequency Response of Origami-Inspired Vibration Isolators With Quasi-Zero-Stiffness Characteristics1

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Kazuya Inamoto ◽  
Sachiko Ishida
Keyword(s):  
Numerical Analysis ◽  
Vibration Isolator ◽  
Spring Stiffness ◽  
Frequency Range ◽  
Torsional Buckling ◽  
Load Range ◽  
Nonlinear Characteristics ◽  
Vibration Isolators ◽  
Initial Load ◽  
Linear Spring

We describe herein a method for extending the load range of a vibration isolator using a foldable cylinder consisting of a torsional buckling pattern and evaluate the vibration isolating performance through excitation experiments. A previous study determined that the foldable cylinder is bistable and acts as a vibration isolator with nonlinear characteristics in a displacement region, where the spring stiffness is zero. Its spring characteristics and vibration isolating performance were clarified by numerical analysis and excitation experiments. The findings indicated that the vibration in a certain frequency range is reduced where the spring stiffness is zero. However, this vibration isolator has a disadvantage in that it can only support an initial load that transfers to the zero-spring-stiffness region. Therefore, in this research, we improve the position of the linear spring attached to the isolator. As a result, the initial load range is extended by two to four times that of the conventional vibration isolator. Furthermore, the isolating performance is maintained even when the initial load is changed within a given load range.

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