Performance Analysis of Series Elastic Actuator Based on Maximum Torque Transmissibility

Lee, Chan; Oh, Sehoon

doi:10.1109/tcst.2021.3059284

Cited by 8 publications

(10 citation statements)

References 17 publications

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“…Cascaded PID can achieve higher bandwidths without showing oscillating behavior. The former is theoretically expected, while the latter can be attributed to the lower noise sensitivity achieved by PD-DOB and Cascaded PID controllers compared to the FSF variants or to the fact that the controller gains negatively influence the maximum torque a SEA controller can track simply by their controller gains, which is a persistent problem of SEAs (Lee and Oh 2021). Additionally, it can be concluded that FSF variants are more sensitive to system parameter errors, since it was necessary to adapt the target bandwidth to achieve the desired bandwidths.…”

Section: Discussionmentioning

confidence: 99%

“…For the 40 Hz conditions, amplitudes of 2.5 Nm in the range of ω ∈ [16, 80] Hz were applied for all controllers besides MRAC which needed amplitudes of 1 Nm. The overall decrease in amplitude with frequency is necessary to not saturate the motor current, and thus guarantee accurate tracking (Lee and Oh 2021). The 40 Hz controllers showed strong oscillations for the FSFt, FSFm and MRAC controller in the pauses between excitations, and were not included in the analysis as a result.…”

Section: Identification Experimentsmentioning

confidence: 99%

See 1 more Smart Citation

Evaluation and comparison of SEA torque controllers in a unified framework

Rampeltshammer¹,

Arvid²,

Menno³

et al. 2022

Preprint

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Series elastic actuators (SEA) with their inherent compliance offer a safe torque source for robots that are interacting with various environments, including humans. These applications have high requirements for the SEA torque controllers, both in the torque response as well as interaction behavior with its the environment. To differentiate state of the art torque controllers, this work is introducing a unifying theoretical and experimental framework that compares controllers based on their torque transfer behavior, their apparent impedance behavior, and especially the passivity of the apparent impedance, i.e. their interaction stability, as well as their sensitivity to sensor noise. We compare classical SEA control approaches such as cascaded PID controllers and full state feedback controllers with advanced controllers using disturbance observers, acceleration feedback and adaptation rules. Simulations and experiments demonstrate the trade-off between stable interactions, high bandwidths and low noise levels. Based on these tradeoffs, an application specific controller can be designed and tuned, based on desired interaction with the respective environment.

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Section: Discussionmentioning

confidence: 99%

Section: Identification Experimentsmentioning

confidence: 99%

Evaluation and comparison of SEA torque controllers in a unified framework

Rampeltshammer¹,

Arvid²,

Menno³

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…Several exoskeletons use serial elastic actuators to control interactive torque at the human robot joint, and thereby provide assistance for people with disabilities [11][12][13][14][15]. However, due to the complex relationship between the torque resolution, bandwidth, and impedance of these actuators, several of these exoskeletons cannot simultaneously provide high torque and bandwidth needed for balance and gait [16,17]. As a result, these devices have predominantly been used for reducing the energetic cost of walking by supplementing a part of human generated torque during activities [18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Development of a Hip Abduction-Adduction Exoskeleton for Mediolateral Assistance

Nalam,

Alili,

Fleming

et al. 2024

Preprint

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Lower limb exoskeletons are gaining prevalence to augment mobility of people with gait impairments. However, current exoskeletons using serial elastic actuators do not have the torque and bandwidth capabilities to assist in balance control in daily activities. Considering the critical role of mediolateral stability in balance control of individuals affected by neurological and age-related gait impairments, we propose an abduction-adduction exoskeleton for mediolateral assistance. The exoskeleton utilizes harmonic gear driven actuators with active torque feedback to ensure high bandwidth and admittance control capabilities, designed as an assistive device for enhanced balance. The exoskeleton is developed to be able to provide assistance up to a bandwidth of 5 Hz at the hip to individuals weighing up to 90 Kgs. Benchtop testing of the exoskeleton showed closed loop velocity bandwidth of more than 5 Hz while under loading with a user weighing 85 Kgs. Further, analysis of admittance controller using both static and dynamic testing showed that the developed controller can simulate stiffnesses up to 95 Nm/rad with an R 2 of over 99%. Pilot human testing individuals showed that the exoskeleton can modulate step width behavior of individuals while ensuring compliance with the users, facilitating seamless human robot interaction. The implication of the developed exoskeleton for balance control in elderly and neurologically impaired populations, and future avenues of research are discussed.

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“…6–9 Among those solutions, the Serial Elastic Actuator (SEA) design that was initially proposed by Pratt and Williamson 10 has gained much attention in the robotics field over the year. 11–16 This innovative design enables the actuator to be more flexible in humanoid robot applications since it replicates the elastic tendon in the human body. By utilizing the SEA design, many humanoid robots and bio-inspired robots have successfully demonstrated their smooth motion capabilities.…”

Section: Introductionmentioning

confidence: 99%

Terminal super-twisting sliding mode based on high order sliding mode observer for two DOFs lower limb system

Tran

Duong

Nguyen

et al. 2023

Measurement and Control

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In this paper, a novel backstepping terminal super-twisting sliding mode (TSTSM) with high order sliding mode observer (HOSMO) is proposed to control the two degrees of freedom (DOFs) Serial Elastic Actuator (SEA), inspired by a lower limb of humanoid robots. First, the dynamic model, extended from our previous study, is presented for developing the control algorithm. Secondly, the backstepping technique is utilized to separate the overall system into two subsystems. One of the challenges of SEA is to deal with the evident oscillations caused by the elastic element, which might lead to the degrading performance of load position control. In order to reduce this adverse effect, a TSTSM is proposed to control the position tracking of two subsystems. The advantages of TSTSM are the finite-time convergence despite the bounded perturbation and the dramatic reduction of the chattering phenomenon. To construct and implement the TSTSM controller, it requires the knowledge of all states, which is not available in the current lower limb system setup. Therefore, a HOSMO is utilized to estimate the unknown states. Finally, experiment results are carried out to assess the effectiveness of the proposed controller and compare it with those of different control schemes.

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Performance Analysis of Series Elastic Actuator Based on Maximum Torque Transmissibility

Cited by 8 publications

References 17 publications

Evaluation and comparison of SEA torque controllers in a unified framework

Evaluation and comparison of SEA torque controllers in a unified framework

Development of a Hip Abduction-Adduction Exoskeleton for Mediolateral Assistance

Terminal super-twisting sliding mode based on high order sliding mode observer for two DOFs lower limb system

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