A Compact Adjustable Stiffness Rotary Actuator Based on Linear Springs: Working Principle, Design, and Experimental Verification

Vo, Cong Phat; Phan, Van Du; Nguyen, Thanh Ha; Ahn, Kyoung Kwan

doi:10.3390/act9040141

Cited by 10 publications

(2 citation statements)

References 28 publications

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“…Stiff springs provide high force range but reduce force fidelity [ 7 , 12 ]. Variable stiffness actuators (VSAs) attempt to overcome this trade-off by tuning the stiffness of a passive mechanical element with a secondary motor [ 13 , 14 ]. However, these systems are often complicated and bulky, hampering their application in lightweight, wearable robots.…”

Section: Introductionmentioning

confidence: 99%

Design and Control of a Series–Parallel Elastic Actuator for a Weight-Bearing Exoskeleton Robot

Wang

Zheng

Zhao

et al. 2022

Sensors

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Weight-bearing exoskeletons are robots that need to carry loads and interact with humans frequently. Therefore, the actuators of these exoskeletons are supposed to be capable of outputting sufficient force with high compliance and little weight. A series–parallel elastic actuator (SPEA) is designed, in this work, to meet the demanding requirements of an exoskeleton robot called PALExo. A gas spring is installed in parallel with an electric cylinder to adjust the force output range of the actuator according to the needs of the exoskeleton. A series elastic module (SEM) is installed in series with the electric cylinder and gas spring to improve the compliance of the actuator, the stiffness of which is variable to adapt to the different stiffness requirements of the exoskeleton’s legs in the standing phase and swinging phase. A force controller combining dynamic compensation and a cascade control with an inner velocity loop and a disturbance observer is designed for the SPEA. The performance of the force controller is verified by experiments and the results demonstrate that the controller has good adaptability to the stiffness of the SEM.

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Section: Introductionmentioning

confidence: 99%

Design and Control of a Series–Parallel Elastic Actuator for a Weight-Bearing Exoskeleton Robot

Wang

Zheng

Zhao

et al. 2022

Sensors

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“…To develop the FTC scheme, various types of control methods are presented such as integral sliding mode control (ISMC) [26], adaptive control [27], intelligent control [28], and so on. Among them, the ISMC has received considerable attention for many practical applications because of the impressive benefits for instance high robustness, reduced steady-state error, pursuing finitetime stability [29]- [31]. Besides, several important research results including [32]- [35] have introduced the outstanding properties of feedback linearization (FBL).…”

Section: Introductionmentioning

confidence: 99%

Actuator Fault-Tolerant Control for an Electro-Hydraulic Actuator Using Time Delay Estimation and Feedback Linearization

Phan

Dao

et al. 2021

IEEE Access

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This article proposes a novel fault-tolerant controller for a double-rod electro-hydraulic actuator whilst the motion control system faces with system disturbances/uncertainties and internal leakage fault. Firstly, taking the advantage of the coordinate transformation, the nonlinear system is converted to a linear system to apply the control design tools in linear control theory. Besides, the matched, mismatched disturbances, and internal leakage fault are integrated into a new lumped uncertainty based on this transformation. Inspired by the great capability of time delay estimation technique, the suggested controller is developed to effectively detect and compensate for the internal leakage fault. To enhance the performance of the control system, an adaptive integral sliding mode control approach is deployed to effectively suppress the lump estimated error, and the effects of fault. The perfect combination of inputoutput feedback linearization, adaptive integral sliding mode, and time delay estimation is investigated to achieve high-precision tracking control and strong robustness in the presence of matched, mismatched disturbances, and faults, simultaneously. Moreover, the global stability of the suggested control algorithm is demonstrated by the Lyapunov theory. Finally, several tracking performance comparisons of the proposed approach with the existing controllers to demonstrate the efficiency are exhibited through simulation analyses and experiment results.

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Adaptive neural tracking control for flexible joint robot including hydraulic actuator dynamics with disturbance observer

Phan,

Vo,

Ahn

2024

Intl J Robust & Nonlinear

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In this paper, a disturbance observer‐based adaptive neural backstepping integral sliding mode control (BISMC) is developed for a flexible joint robot (FJR) with the integration of an adjustable stiffness rotary actuator (ASRA). This system suffers from unknown system dynamics, external disturbance, and the influence of variable stiffness, which is a challenge for achieving precision tracking performance. Considering the lumped disturbances in FJR generated by the hydraulic system and the stiffness modulation of the ASRA, we investigate the structural dynamics nonlinear model of the FJR system, including hydraulic actuator dynamics. While other linear control strategies are applied for the FJR, the proposed controller uses BISMC, neural networks (NN), and nonlinear disturbance observers to deal with the disadvantages mentioned above. Radial basis function neural networks (RBFNN) are designed to tackle unknown nonlinear functions, and the disturbance observers are introduced to compensate for the influence of the variable stiffness, disturbance, and the approximation error caused by NN. Simulations and experiments are independently implemented to demonstrate the effectiveness and feasibility of the proposed controller. Results exhibit that the integral absolute error‐index is reduced by 20.4% when the proposed method is deployed for the experiment with a multistep trajectory.

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A Compact Adjustable Stiffness Rotary Actuator Based on Linear Springs: Working Principle, Design, and Experimental Verification

Cited by 10 publications

References 28 publications

Design and Control of a Series–Parallel Elastic Actuator for a Weight-Bearing Exoskeleton Robot

Design and Control of a Series–Parallel Elastic Actuator for a Weight-Bearing Exoskeleton Robot

Actuator Fault-Tolerant Control for an Electro-Hydraulic Actuator Using Time Delay Estimation and Feedback Linearization

Adaptive neural tracking control for flexible joint robot including hydraulic actuator dynamics with disturbance observer

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