A lightweight variable stiffness knee exoskeleton driven by shape memory alloy

Zhang, Jiaqi; Cong, Ming; Liu, Dong; Du, Yu; Ma, Hongjiang

doi:10.1108/ir-11-2021-0262

Cited by 16 publications

(4 citation statements)

References 39 publications

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“…Compared with traditional rigid grippers actuated by electric motors (S and R, 2018), pneumatic (Walker et al , 2020; Zhong et al , 2019; Zhong et al , 2021) and electrohydraulic (Park et al , 2020), etc., the flexible grippers actuated by smart materials are smaller, more adaptable and safer to better interact with unstructured environments and can perform tasks with more postures (Yoon, 2019; Shintake et al , 2018; Ogawa et al , 2022; Wang et al , 2022; Cardin-Catalan et al , 2022; Pi et al , 2021). Service robot grippers usually need to actively grasp objects to avoid falling during the grasping process and can adapt to various shapes of objects well (Zhang et al , 2020b; Wang et al , 2021; Zhang et al , 2022a, 2022b). Therefore, it is very important to design a suitable actuation system and a properly flexible jaw for the development of a smart mechanical gripper with enhanced performance.…”

Section: Introductionmentioning

confidence: 99%

“…The grippers actuated by SMA wire have been widely studied, including embedded, external and so on (Wang et al, 2016;Mehrabi and Aminzahed, 2020). To enlarge a relatively small actuation stroke or achieve a large actuation stroke, various amplification mechanisms, such as series and winding arrangements (Leng et al, 2016;Lu et al, 2019;Zhang et al, 2022aZhang et al, , 2022b, are, therefore, developed. Because SMA strips have a larger cross-sectional area and can, therefore, generate more force than SMA wires, they have been used to design grippers that require higher output forces (Engeberg et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

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A novel dual-stage shape memory alloy actuated gripper

Liu

Tong

et al. 2022

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Purpose The paper aims to propose a novel dual-stage shape memory alloy (SMA) actuated gripper (DAG), of which the grasp performance is improved through primary and secondary actuation. Design/methodology/approach This paper presents a method of integrating the design of dual-stage actuation modules based on the SMA bias actuation principle to enhance the grasping shape adaptability and force modulation of a DAG. The actuation angle range and grasping performance of the DAG are investigated by thermomechanical analysis and the finite element method based numerical simulation. Findings The results of present experiments and simulations indicate that the actuation angle scope of the DAG is about 20° under no load, which enables the grasping space occupied by an object in the DAG from 60 mm to 120 mm. The grasping force adjusted by changing the input power of the primary main actuation module and secondary fine-tuning actuation module can reach a maximum of 2 N, which is capable of grasping objects of various sizes, weights, shapes, etc. Originality/value The contribution of this paper is to design a DAG based on SMA, and establish the solution methods for the primary main actuation module and secondary fine-tuning actuation module, respectively. It lays a foundation for the research of lightweight and intelligent robotic grippers.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A novel dual-stage shape memory alloy actuated gripper

Liu

Tong

et al. 2022

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“…The inherent compliance of soft materials enables soft grippers to safely deal with deformable and fragile objects and adaptability to uneven shapes (Shintake et al, 2016). A significant number of actuation methods have been investigated, including cabledriven mechanisms (Wang et al, 2020a(Wang et al, , 2020b(Wang et al, , 2020c, soft pneumatic actuators (SPAs) (Liu et al, 2019), dielectric elastomer actuators (Chen et al, 2019), magnetic actuators (Tang et al, 2021) and shape memory materials including metal alloys (Zhang et al, 2022) and polymers (Wang et al, 2019). Among these methods, SPA is one of the oldest and the most widespread technologies used for soft grippers owing to several advantages such as lightweight, high power-to-weight ratio, large stroke, force production, ease of fabrication, robustness and low-cost materials (Sun et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

A novel soft gripper with enhanced gripping adaptability based on spring-reinforced soft pneumatic actuators

Cheng

Yan

et al. 2022

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Purpose Soft grippers have safer and more adaptable human–machine and environment–machine interactions than rigid grippers. However, most soft grippers with single gripping postures have a limited gripping range. Therefore, this paper aims to design a soft gripper with variable gripping posture to enhance the gripping adaptability. Design/methodology/approach This paper proposes a novel soft gripper consisting of a conversion mechanism and four spring-reinforced soft pneumatic actuators (SSPAs) as soft fingers. By adjusting the conversion mechanism, four gripping postures can be achieved to grip objects of different shapes, sizes and weights. Furthermore, a quasi-static model is established to predict the bending deformation of the finger. Finally, the bending angle of the finger is measured to validate the accuracy of the quasi-static model. The gripping force and gripping adaptability are tested to explore the gripping performance of the gripper. Findings Through experiments, the results have shown that the quasi-static model can accurately predict the deformation of the finger; the gripper has the most significant gripping force under the parallel posture, and the gripping adaptability of the gripper is highly enhanced by converting the four gripping postures. Originality/value By increasing the gripping posture, a novel soft gripper with enhanced gripping adaptability is proposed to enlarge the gripping range of the soft gripper with a single posture. Furthermore, a quasi-static model is established to analyze the deformation of SSPA.

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“…Some energy storage assisted exoskeletons can also be adjusted according to the anatomical differences of different people [14]. Their actuating methods mainly include cable actuator [15], pneumatic muscle [16], and new intelligent material drive [17].…”

mentioning

confidence: 99%

Stiffness Optimal Modulation of a Variable Stiffness Energy Storage Hip Exoskeleton and Experiments on Its Assistance Effect

Feng-chen

Cheng

et al. 2023

IEEE Trans. Neural Syst. Rehabil. Eng.

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Lower limb energy storage assisted exoskeletons realize walking assistance by using the energy stored by elastic elements during walking. Such exoskeletons are characterized by a small volume, light weight and low price. However, energy storage assisted exoskeletons adopt fixed stiffness joints typically, which cannot adapt to changes of the wearer's height, weight, or walking speed. In this study, based on the analysis of the energy flow characteristics and stiffness change characteristics of lower limb joints during a human walking on flat ground, a novel variable stiffness energy storage assisted hip exoskeleton is designed, and a stiffness optimization modulation method is proposed to store most of the negative work done by the human hip joint when walking. Through the analysis of the surface electromyography signals of the rectus femoris and long head of the biceps femoris, it is found that the muscle fatigue of the rectus femoris is reduced by 8.5% under the optimal stiffness assistance condition, and the exoskeleton provides better assistance under the optimal stiffness assistance condition.

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A lightweight variable stiffness knee exoskeleton driven by shape memory alloy

Cited by 16 publications

References 39 publications

A novel dual-stage shape memory alloy actuated gripper

A novel dual-stage shape memory alloy actuated gripper

A novel soft gripper with enhanced gripping adaptability based on spring-reinforced soft pneumatic actuators

Stiffness Optimal Modulation of a Variable Stiffness Energy Storage Hip Exoskeleton and Experiments on Its Assistance Effect

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