Impedance-Controlled Variable Stiffness Actuator for Lower Limb Robot Applications

Liu, Lin; Leonhardt, Steffen; Ngo, Chuong; Misgeld, Berno J.E.

doi:10.1109/tase.2019.2954769

Cited by 71 publications

(23 citation statements)

References 38 publications

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“…The parameters of the observer (4) are selected as L 1 = diag [25,25], L 2 = diag[2600, 6000], and L 3 = diag [18600,60000]. The parameters of the controller (21) are settledas p = 0.5, B = diag[50, 50], K 1 = diag[50, 35],and K 2 = diag [3,5]. Remark 4.…”

Section: Matlab Simulation Resultsmentioning

confidence: 99%

“…1 Understandably, there has been much interest from the field such as medicine and rehabilitation. [2][3][4][5] As a typical human-robot collaboration system, the lower extremity exoskeleton includes the wear's lower limbs and mechanical limbs. Correspondingly, its input torque includes the active torque provided by the wearer and the auxiliary torque provided by the mechanical limbs.…”

Section: Introductionmentioning

confidence: 99%

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Observer-based finite-time control for trajectory tracking of lower extremity exoskeleton

Wang

Guo

2021

Proceedings of the Institution of Mechanical Engineers, Part I:

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In this article, an advanced observer-based finite-time trajectory tracking controller is investigated for lower extremity exoskeleton without available joint angular velocities to improve the movement ability of dependent persons, which is robust against uncertain dynamics, human active joint torque and external disturbances. First, the Lagrange principle is applied to analyze the dynamic properties of lower extremity exoskeleton driven by artificial pneumatic muscles, and its swing phase model is established. After that, a novel finite-time extended state observer is proposed to observe the lumped disturbances and unavailable angular velocities of the lower limb exoskeleton simultaneously. Furthermore, a finite-time sliding mode controller of exoskeleton is designed based on the extended state observer, and the finite-time convergence of tracking error is rigorously demonstrated based on the Lyapunov theory. Finally, the control system simulation is established and experimental tests are conducted with a voluntary subject during flexion of wearer’s knee and hip joints, the obtained results demonstrate fast and high-precision tracking performance of the proposed approach.

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Section: Matlab Simulation Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Observer-based finite-time control for trajectory tracking of lower extremity exoskeleton

Wang

Guo

2021

Proceedings of the Institution of Mechanical Engineers, Part I:

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“…As a consequence, numerous methods were developed for controlling such robots with elastic joints in terms of regulation or tracking tasks, e.g., PD-regulator with gravity compensation [11] [12], feedback linearization [13] [14], backstepping [15]. Recently, control methods based on inverse dynamics [16] and linear quadratic regulator [17] have been developed for VSA that allow the active variation of the mechanical stiffness. In [18] [19], passivity-based control laws are proposed and showed excellent performance for the impedance control on the robots with relatively stiff joints.…”

Section: Introductionmentioning

confidence: 99%

Elastic Structure Preserving Impedance Control of Bidirectional Antagonistic Variable Stiffness Actuation

Meng

Keppler

Ott

2021

2021 European Control Conference (ECC)

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We propose an impedance controller for articulated soft robots implemented by bidirectional antagonistic variable stiffness (BAVS) actuation, where two motors are connected via nonlinear elastic elements to a single link allowing for a joint stiffness modulation. Naturally, the highly elastic elements introduce undesired oscillatory dynamics into the plant. To address this problem, we present a controller that allows to impose a desired link-side stiffness and damping behavior while preserving the intrinsic inertial elastic properties of the system. This allows us to solve the global asymptotic regulation problem while simultaneously imposing a desired joint stiffness preset on the BAVS actuator. We provide a passivity and stability analysis based on a physically motivated storage and Lyapunov function. Experimental results on the underarm BAVS joint of DLR David validate our control law.

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“…Using the derivatives and integrals operations in fractional orders may be adjusted for the frequency response of the control system directly and continuously (Oh and Kong, 2016). The controllers based on fractional-order derivatives and integrals are usually used in industrial applications and other various fields such as system identification, haptic, power electronics, robotic arms and magnetic levitation system control (Liu et al , 2019; Tosun and Patoglu, 2020; Fotuhi et al , 2020; Zhang et al , 2019). It should be noted that the behavior of many physical systems can be determined using FOC theory and can be controlled with fractional hybrid impedance control (FHIC) even if the system has unstable or time delay behaviors (Ugurlu et al , 2015; Braun et al , 2018).…”

Section: Introductionmentioning

confidence: 99%

Novel fractional hybrid impedance control of series elastic muscle-tendon actuator

Fotuhi

Bingül

2021

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Purpose This paper aims to develope a novel fractional hybrid impedance control (FHIC) approach for high-sensitive contact stress force tracking control of the series elastic muscle-tendon actuator (SEM-TA) in uncertain environments. Design/methodology/approach In three different cases, the fractional parameters of the FHIC were optimized with the particle swarm optimization algorithm. Its adaptability to the pressure of the sole of the foot on real environments such as grass (soft), carpet (medium) and solid floors (hard) is far superior to traditional impedance control. The main aim of this paper is to derive the dynamic simulation models of the SEM-TA, to develop a control architecture allowing for high-sensitive contact stress force control in three cases and to verify the simulation models and the proposed controller with experimental results. The performance of the optimized controllers was evaluated according to these parameters, namely, maximum overshoot, steady-state error, settling time and root mean squared errors of the positions. Moreover, the frequency robustness analysis of the controllers was made in three cases. Findings Different simulations and experimental results were conducted to verify the control performance of the controllers. According to the comparative results of the performance, the responses of the proposed controller in simulation and experimental works are very similar. Originality/value Origin approach and origin experiment.

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Impedance-Controlled Variable Stiffness Actuator for Lower Limb Robot Applications

Cited by 71 publications

References 38 publications

Observer-based finite-time control for trajectory tracking of lower extremity exoskeleton

Observer-based finite-time control for trajectory tracking of lower extremity exoskeleton

Elastic Structure Preserving Impedance Control of Bidirectional Antagonistic Variable Stiffness Actuation

Novel fractional hybrid impedance control of series elastic muscle-tendon actuator

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