Variable Stiffness Spring Actuators for Low-Energy-Cost Human Augmentation

Braun, David J.; Chalvet, Vincent; Chong, Tze-Hao; Apte, Salil; Hogan, Neville

doi:10.1109/tro.2019.2929686

Cited by 58 publications

(32 citation statements)

References 59 publications

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“…Thus, combining features from active and passive exoskeletons to create a new class of pseudo-passive (or semi-active) devices may yield a promising future direction for exoskeleton technology [59]. For example, rather than continuously modulating the assistance torque profile, a pseudo-passive device might inject small amounts of power to change the mechanical properties of an underlying passive structure during periods when it is unloaded [62]. The pseudo-passive approach likely benefits from the streamlined structural design (e.g., small motors) and adaptability that requires only small amounts of energy input (e.g., small batteries).…”

Section: Leading Approaches and Technologies For Advancing Exoskeletonsmentioning

confidence: 99%

The exoskeleton expansion: improving walking and running economy

Sawicki

Beck

Kang

et al. 2020

J NeuroEngineering Rehabil

309

201

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Since the early 2000s, researchers have been trying to develop lower-limb exoskeletons that augment human mobility by reducing the metabolic cost of walking and running versus without a device. In 2013, researchers finally broke this 'metabolic cost barrier'. We analyzed the literature through December 2019, and identified 23 studies that demonstrate exoskeleton designs that improved human walking and running economy beyond capable without a device. Here, we reviewed these studies and highlighted key innovations and techniques that enabled these devices to surpass the metabolic cost barrier and steadily improve user walking and running economy from 2013 to nearly 2020. These studies include, physiologically-informed targeting of lower-limb joints; use of off-board actuators to rapidly prototype exoskeleton controllers; mechatronic designs of both active and passive systems; and a renewed focus on human-exoskeleton interface design. Lastly, we highlight emerging trends that we anticipate will further augment wearable-device performance and pose the next grand challenges facing exoskeleton technology for augmenting human mobility.

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Section: Leading Approaches and Technologies For Advancing Exoskeletonsmentioning

confidence: 99%

The exoskeleton expansion: improving walking and running economy

Sawicki

Beck

Kang

et al. 2020

J NeuroEngineering Rehabil

309

201

View full text Add to dashboard Cite

show abstract

“…Assuming that the average energy rate of the limbs ¯ E • is maximized by the human to achieve the top speed, As the leg extends, the spring is compressed and the stiffness of the spring is increased. The latter can be achieved by a variable stiffness mechanism, which increases stiffness by decreasing the effective length of the spring [see (28,(30)(31)(32), Materials and Methods, and movie S1]. The exoskeleton provides mechanical advantage to the human such that large leg extension, small leg force, and small leg stiffness provide small spring compression, large spring force, and large spring stiffness.…”

Section: Discussionmentioning

confidence: 99%

“…1A), the leg extends to compress the spring and to simultaneously increase the stiffness of the spring. The stiffness of the spring is increased by coupling the leg to a variable stiffness mechanism, which decreases the effective length of the spring (28,30,32,33). As a result, the force of the spring and the energy stored by the spring increase F = k(Δ l leg ) Δl(Δ l leg ) + O(Δ l 3 ) and E spr = ∫ 0…”

Section: Variable Stiffness Springmentioning

confidence: 99%

How to run 50% faster without external energy

Sutrisno

Braun

2020

Sci. Adv.

Self Cite

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Technological innovations may enable next-generation running shoes to provide unprecedented mobility. But how could a running shoe increase the speed of motion without providing external energy? We found that the top speed of running may be increased more than 50% using a catapult-like exoskeleton device, which does not provide external energy. Our finding uncovers the hidden potential of human performance augmentation via unpowered robotic exoskeletons. Our result may lead to a new-generation of augmentation devices developed for sports, rescue operations, and law enforcement, where humans could benefit from increased speed of motion.

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“…As a typical representative of the flexible actuator, the variable stiffness actuator (VSA) [11][12][13] aims to imitate the characteristics in dynamics and kinematics of a biosystem. Same as series elastic actuator [14][15][16], VSA can increase peak power output [17] and reduce energy consumption [18] by storing and releasing the potential energy stored in the elastic element. In addition to the advantages of series elastic actuator, VSA can increase the adaptability of manipulators by actively adjusting its own stiffness to meet different task requirements for improving performances [19] and exhibits advantages in terms of energy efficiency [20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Mechanical design and analysis of a novel variable stiffness actuator with symmetrical pivot adjustment

2021

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The safety of human-robot interaction is an essential requirement for designing collaborative robotics. Thus, this paper aims to design a novel variable stiffness actuator (VSA) that can provide safer physical human-robot interaction for collaborative robotics. VSA follows the idea of modular design, mainly including a variable stiffness module and a drive module. The variable stiffness module transmits the motion from the drive module in a roundabout manner, making the modularization of VSA possible. As the key component of the variable stiffness module, a stiffness adjustment mechanism with a symmetrical structure is applied to change the positions of a pair of pivots in two levers linearly and simultaneously, which can eliminate the additional bending moment caused by the asymmetric structure. The design of the double-deck grooves in the lever allows the pivot to move freely in the groove, avoiding the geometric constraint between the parts. Consequently, the VSA stiffness can change from zero to infinity as the pivot moves from one end of the groove to the other. To facilitate building a manipulator in the future, an expandable electrical system with a distributed structure is also proposed. Stiffness calibration and control experiments are performed to evaluate the physical performance of the designed VSA. Experiment results show that the VSA stiffness is close to the theoretical design stiffness. Furthermore, the VSA with a proportional-derivative feedback plus feedforward controller exhibits a fast response for stiffness regulation and a good performance for position tracking.

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Variable Stiffness Spring Actuators for Low-Energy-Cost Human Augmentation

Cited by 58 publications

References 59 publications

The exoskeleton expansion: improving walking and running economy

The exoskeleton expansion: improving walking and running economy

How to run 50% faster without external energy

Mechanical design and analysis of a novel variable stiffness actuator with symmetrical pivot adjustment

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