Adaptation in a variable parallel elastic actuator for rotary mechanisms towards energy efficiency

Mohseni, Omid; Shahri, Majid Abedinzadeh; Davoodi, Ayoob; Ahmadabadi, Majid Nili

doi:10.1016/j.robot.2021.103815

Cited by 7 publications

(4 citation statements)

References 25 publications

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“…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. Similarly, PEAs, which incorporate compliant elements in parallel with actuators, excel in tasks requiring agility and responsiveness due to their enhanced bandwidth [8,9]. Because an elastic element with fixed stiffness is used in SEA and PEA, the link stiffness is fixed, limiting their usage in human-friendly robotic systems.…”

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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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: 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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“…One prominent example is legged robots powered by pneumatic artificial muscles (PAMs), which mirror human muscular characteristics regarding flexibility and linear actuation. Their antagonistic placement at joint locations provides elasticity and produces vertical forces for hopping (Dowling and Vamos, 1993;Kubo et al, 1999;Roberts and Azizi, 2011;Mohseni et al, 2021;Zhao et al, 2022). Moreover, the configuration Takahashi et al 10.3389/frobt.2023.1293365 across multiple joints offers redundancy in joint degrees of freedom, resulting in efficient force transmission at each joint (Gregoire et al, 1984;Pandy et al, 1990;Zajac et al, 2002;Ruppert and Badri-Spröwitz, 2019).…”

Section: Introductionmentioning

confidence: 99%

Enhancing postural stability in a musculoskeletal hopping robot through stretch reflex application on biarticular thigh muscles

Takahashi,

Murakami,

Hosoda

2023

Front. Robot. AI

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Postural stabilization during rapid and powerful hopping actions represents a significant challenge for legged robotics. One strategy utilized by humans to negotiate this difficulty is the robust activation of biarticular thigh muscles. Guided by this physiological principle, this study aims to enhance the postural stability of a hopping robot through the emulation of this human mechanism. A legged robot powered by pneumatic artificial muscles (PAMs) was designed to mimic human anatomical structures. A critical aspect of this development was creating a tension-oriented stretch reflex system engineered to initiate muscle activation in response to perturbations. Our research encompassed three experiments: 1) assessing the trunk pitch angle with and without the integration of stretch reflexes, 2) evaluating the consistency of hops made with and without reflexes, and 3) understanding the correlation between the reflex strength equilibrium in the biarticular thigh muscles and trunk pitch angle. The results indicated that the integration of the stretch reflex minimized perturbations, thereby allowing the robot to perform double the continuous hops. As hypothesized, adjusting the reflex strength equilibrium caused a shift in the angle. This reflex mechanism offers potential application to PAM-driven robots and signifies a promising avenue for enhancing postural stability in diverse forms of locomotion, including walking and running.

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“…However, it cannot lower the peak torque requirements and is limited in terms of energy consumption reduction (Beckerle et al, 2016 ). In contrast, parallel elasticity can overcome these limitations as it can modify the system's natural dynamics by directly affecting the motor torque (Sharbafi et al, 2020 ; Mohseni et al, 2021 ). Therefore, a system with both series and parallel compliance can be very flexible for various locomotion tasks' torque and power requirements.…”

Section: Introductionmentioning

confidence: 99%

Exploring the effects of serial and parallel elasticity on a hopping robot

Zhao

Mohseni²,

Murcia³

et al. 2022

Front. Neurorobot.

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The interaction between the motor control and the morphological design of the human leg is critical for generating efficient and robust locomotion. In this paper, we focus on exploring the effects of the serial and parallel elasticity on hopping with a two-segmented robotic leg called electric-pneumatic actuation (EPA)-Hopper. EPA-Hopper uses a hybrid actuation system that combines electric motors and pneumatic artificial muscles (PAM). It provides direct access to adjust the physical compliance of the actuation system by tuning PAM pressures. We evaluate the role of the serial and parallel PAMs with different levels of compliance with respect to four criteria: efficiency, performance, stability, and robustness of hopping against perturbations. The results show that the serial PAM has a more pronounced impact than the parallel PAM on these criteria. Increasing the stiffness of the serial PAM decreases the leg stiffness of the unloading phase during hopping. The stiffer the leg, the more efficient and the less robust the movement. These findings can help us further understand the human hopping mechanism and support the design and control of legged robots and assistive devices.

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Adaptation in a variable parallel elastic actuator for rotary mechanisms towards energy efficiency

Cited by 7 publications

References 25 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

Enhancing postural stability in a musculoskeletal hopping robot through stretch reflex application on biarticular thigh muscles

Exploring the effects of serial and parallel elasticity on a hopping robot

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