Design and Control of a Novel Variable Stiffness Series Elastic Actuator

Sarıyıldız, Emre; Mutlu, Rahim; Roberts, Jon; Kuo, Chin-Hsing; Uğurlu, Barkan

doi:10.1109/tmech.2022.3232471

Cited by 19 publications

(6 citation statements)

References 45 publications

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“…Note that b * 0 is supposed to be zero in the numerator of the transfer function due to the biproper nature of the AVSA system (i.e., the system output does not instantaneously follow the input voltage change). By cross multiplication of the transfer function in (7) and obtaining the inverse z-transform, we obtain the following:…”

Section: Nonlinear Sta¡c Func¡onmentioning

confidence: 99%

“…Series elastic actuators (SEAs) and parallel elastic actuators (PEAs) have emerged as prominent solutions, albeit with inherent disadvantages. SEAs, characterized by compliant elements such as springs integrated in series with actuators, offer notable advantages in precise force control and shock absorption [6,7]. However, their reliance on mechanical springs introduces inertia and limits their bandwidth, constraining their suitability for applications demanding rapid and dynamic movements especially with low stiffness.…”

Section: Introductionmentioning

confidence: 99%

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Data-Driven Position and Stiffness Control of Antagonistic Variable Stiffness Actuator Using Nonlinear Hammerstein Models

Javadi,

Haghighi,

Pornpipatsakul

et al. 2024

JSAN

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In this paper, an optimal PID controller is introduced for an antagonistic variable stiffness actuator (AVSA) based on Hammerstein models. A set of Hammerstein models is developed for the AVSA using the voltage difference method. For each stiffness level, linear and nonlinear Hammerstein models are identified using the least squares method. Experimental results confirm that the outputs of the Hammerstein models fit the measured data better than linear models, as Hammerstein models can incorporate nonlinear effects such as friction. A genetic algorithm is utilized to find optimal PID gains for different stiffness levels and reference position amplitudes. The final gains are obtained by linearly interpolating the optimal gains obtained. To demonstrate the effectiveness of the proposed design, several scenarios with different reference positions and stiffness profiles are provided. Specifically, square, sinusoidal, and sawtooth waves are used for reference positions and stiffness values. The robustness of the proposed approach is further analyzed by applying a disturbance force on the actuator link. The results are compared with the linear method, showing that the proposed design can handle soft transitions in stiffness variation and ensure perfect tracking.

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Section: Nonlinear Sta¡c Func¡onmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Data-Driven Position and Stiffness Control of Antagonistic Variable Stiffness Actuator Using Nonlinear Hammerstein Models

Javadi,

Haghighi,

Pornpipatsakul

et al. 2024

JSAN

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“…To develop a mechanically safer robot actuator without lowering the transmission ratio, an elastic element can be inserted between the actuator and the output link to form a series elastic actuator (SEA) [11][12][13][14][15][16][17][18][19]. The elastic element can provide an energy buffer to filter the impact force between humans and robots.…”

Section: Volume XX 2023mentioning

confidence: 99%

“…Fig. 10 shows the models of existing SEAs [11][12][13][14][15][16][17][18][19] and our proposed compliant actuators. In Fig.…”

Section: A Comparison With Existing Series Elastic Actuatorsmentioning

confidence: 99%

Toward Inherently Safer Human-Robot Interaction Using Compliant Actuators With High Torque-to-Inertia Ratios and Low Torque-to-Stiffness Ratios

Yu,

Huang,

Lan

2023

IEEE Access

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Existing robots rely on external sensors to detect and prevent potential human-robot collisions. However, with the growing demand for complex and high-speed human-robot interaction, robots with inherently safer actuators are becoming more desirable. Such robots offer robust protection against excessive impact force even when external sensors fail or become unavailable. Robot actuators with low reflected inertia and low effective stiffness are necessary to achieve mechanically safer human-robot interaction. This paper presents novel compliant actuators with high torque-to-inertia ratios and low torqueto-stiffness ratios without compromising the output torque and output stiffness of an actuator. Comparisons with existing actuators demonstrate that a robot with the proposed compliant actuators has a much lower effective mass sensed at the end-effector. Impact analysis is presented to verify the effectiveness of high torque-to-inertia ratios and low torque-to-stiffness ratios. To assess the performance of the proposed robot, a pose repeatability experiment is conducted, which shows that the end-effector position control precision is comparable to existing stiff robots despite the inherent compliance of the actuators. These compliant actuators can be used to build various human-friendly robots and are expected to improve the safety and reliability of human-robot interaction.INDEX TERMS Compliant actuator, human-robot interaction, torque-to-inertia ratio, torque-to-stiffness ratio, back-drivability, head injury criterion, repeatability.

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“…Lightweight robots are built to operate in temporary working environments without safety cages, and considerable effort is put into achieving lightweight, compact, and affordable designs with compliant and back-drivable behavior [1,2]. The ability of Additive Manufacturing (AM) to produce complex structures with undercuts and cavities has led engineers to rethink the designs of many products, such as running shoes [3] and highperformance engine pistons [4], and may eventually influence the design and production of future lightweight robots.…”

Section: Introduction 1motivationmentioning

confidence: 99%

Design, Topology Optimization, and Additive Manufacturing of a Pneumatically Actuated Lightweight Robot

et al. 2023

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Soft robotics research has rapidly incorporated Additive Manufacturing (AM) into its standard prototyping repertoire. While numerous publications have highlighted the suitability of AM for producing soft pneumatic actuators, fluidic components, and lightweight structures, their integration into an industry-like robotic arm has not yet been shown. Against this background, a pneumatically actuated robot was developed that incorporates additively manufactured soft structures into rigid articulated hinges that generally allow for integration into today’s industrial production lines. The development of the robot, including pneumatic soft rotary bellows and rotary vane actuators (RVAs), is summarized, and its functionality is proven. It was found that using AM can increase the structural stiffness of robot links to a significant degree as manufacturing-related constraints in topology optimization are largely eliminated. Moreover, it was found that multi-material polyjet printing of soft rotary bellows actuators allows for highly integrated designs that provide low leakage and friction. However, these soft rotary actuators are still inferior in terms of endurance and performance if compared to AM replicas of RVAs. Our work narrows the gap between soft robotics research and today’s industrial applications, may realign research directions, and may provide impulses for the industry towards soft robotics and AM.

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Design and Control of a Novel Variable Stiffness Series Elastic Actuator

Cited by 19 publications

References 45 publications

Data-Driven Position and Stiffness Control of Antagonistic Variable Stiffness Actuator Using Nonlinear Hammerstein Models

Data-Driven Position and Stiffness Control of Antagonistic Variable Stiffness Actuator Using Nonlinear Hammerstein Models

Toward Inherently Safer Human-Robot Interaction Using Compliant Actuators With High Torque-to-Inertia Ratios and Low Torque-to-Stiffness Ratios

Design, Topology Optimization, and Additive Manufacturing of a Pneumatically Actuated Lightweight Robot

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