A parallel-guided compliant mechanism with variable stiffness based on layer jamming

Zeng, Xianpai; Hurd, Cart; Su, Hai‐Jun; Song, Siyang; Wang, Junmin

doi:10.1016/j.mechmachtheory.2020.103791

Cited by 30 publications

(15 citation statements)

References 14 publications

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“…It is therefore complicated to design and control the stages using multi-actuators. [15][16][17] For example, the voice coil motor with coarse resolution and piezoelectric actuator with fine resolution are applied to implement the micropositioning stage. Therefore, a single-drive micropositioning stage with multi resolutions can be designed by varying the stiffness of the stages.…”

Section: Introductionmentioning

confidence: 99%

Design of compliant mechanisms with piecewise stiffness variation using self-contact

Niu

2022

Proceedings of the Institution of Mechanical Engineers, Part C:

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Compliant mechanisms with stiffness variation are required in engineering applications. But most studies in the field of compliant mechanisms have only focused on a mechanism with a single stiffness. This paper presents a design method of compliant mechanisms with multi-level stiffness variation using internal self-contact between rigid parts. The contact changes the reconfigurations of compliant mechanisms to vary their stiffness for a specific motion range. We avoid the need for an external control to achieve piecewise stiffness variation. We derived the general design guideline by which the desired multiple stiffness and motion ranges can be acquired through rational design of the structural parameter. To illustrate the effectiveness of the design idea, we fabricated proof-of-concept prototypes for experimental investigations, and the experimental results demonstrated that the designed compliant mechanism has a multiple-motion range corresponding to different stiffness. The design ideas can also be extended to the multi-axis spatial compliant mechanisms. This design idea enriches the theory and application of compliant mechanisms.

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Section: Introductionmentioning

confidence: 99%

Design of compliant mechanisms with piecewise stiffness variation using self-contact

Niu

2022

Proceedings of the Institution of Mechanical Engineers, Part C:

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“…Nanopositioning systems with tunable stiffness enable adjustment of the working range and mechanical bandwidth according to the operating conditions. Several controllable stiffness solutions, including cross-section shaping [ 17 ], the implementation of multilayer beams [ 18 ], preloading and boundary condition adjustment [ 19 ], layer jamming [ 20 ], and fluid-based approaches [ 21 ], have been applied in the design of compliant mechanisms and nanopositioning systems. However, the essential tuning mechanisms significantly affect the mechanical structure of the nanopositioning systems.…”

Section: Introductionmentioning

confidence: 99%

Design and Analysis of a Novel Flexure-Based Dynamically Tunable Nanopositioner

2021

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Various tools, such as biomedical manipulators, optical aligners, and ultraprecision manufacturing tools, implement nanopositioners that must be dynamically tunable to satisfy the requirements of different working conditions. In this paper, we present the design and analysis of a flexure-based nanopositioner with dynamically tunable characteristics for the implementation of a high-performance servomechanism. The nanopositioner is composed of four flexure beams that are positioned in parallel and symmetric configurations sandwiched between magnetorheological elastomers (MREs). The properties of MREs impart dynamicity to the nanopositioner, allowing the workspace, stiffness, and damping characteristics in particular to be tuned under the action of an external magnetic field. By utilizing elastic beam theory and electromagnetic field coupling analysis, kinetostatic and dynamic models of the proposed nanopositioner were established to predict the variable stiffness property and dynamically tunable characteristics. The models were validated by performing a finite element analysis. Herein, it is shown that the proposed nanopositioner model can actively adjust the trade-offs between the working range, speed, and sustained load capability by changing the magnetic field. The proposed dynamic tuning method offers new insight into the design of flexure-based nanopositioners for real applications.

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“…According to the realization principle of variable stiffness, wearable robots can be classified into three types: functional material-based [11][12][13][14][15][16][17][18], vacuum-based [19][20][21][22][23][24][25][26][27], and friction-based [28][29][30]. In particular, functional material-based type robots have obvious advantages in terms of volume and weight, and a shape memory alloy (SMA) is the most frequently employed functional material in the variable stiffness structure design [11,12].…”

Section: Introductionmentioning

confidence: 99%

“…The emergence of a vacuum-based jamming mechanism provides an alternative for achieving variable stiffness in wearable robots [19]. Vacuum-based jamming can be categorized into two types: granular [20,21] and layer jamming [22][23][24][25][26][27]. Choi et al [20] proposed a soft wearable robot for wrist support with a variable stiffness mechanism based on granular jamming.…”

Section: Introductionmentioning

confidence: 99%

“…However, the maximum bending torque in the experiments was only 1.6 Nm, making it difficult to support and buffer human knee joint motion. In contrast, a variable stiffness structure based on layer jamming has also been investigated by many researchers [22][23][24][25]. A variable stiffness exosuit based on layer jamming was proposed by Ibrahimi et al [26], where the exosuit was utilized to maintain a supportive function and improve the comfort of the patients while sitting.…”

Section: Introductionmentioning

confidence: 99%

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Friction Prediction and Validation of a Variable Stiffness Lower Limb Exosuit Based on Finite Element Analysis

Zuo

Chen

et al. 2021

Actuators

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The variable stiffness exosuit has great potential for human augmentation and medical applications. However, the model of the variable stiffness mechanism in exosuits is far from satisfactory for the accurate prediction and control of friction force. This paper presents a friction prediction model of a variable stiffness lower limb exosuit, verifies its prediction performance, and identifies its applicability. The friction force model was established by the Coulomb friction hypothesis. The equivalent coefficient, which is the core parameter of the model, was determined based on friction and squeezing force data obtained by tests and an ANSYS simulation. Experiments show that the prediction error of the proposed model can reach 15% with a proper structural dimension change constraint. The friction force control test showed that the achieved model can shorten the settling time of the step response by 26% and eliminate the steady-state error. Verifications indicate that the proposed method can provide guidance to the modeling of other friction/stiffness structures, especially friction-based wearable robot structure models and predictions.

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A parallel-guided compliant mechanism with variable stiffness based on layer jamming

Cited by 30 publications

References 14 publications

Design of compliant mechanisms with piecewise stiffness variation using self-contact

Design of compliant mechanisms with piecewise stiffness variation using self-contact

Design and Analysis of a Novel Flexure-Based Dynamically Tunable Nanopositioner

Friction Prediction and Validation of a Variable Stiffness Lower Limb Exosuit Based on Finite Element Analysis

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