Model based control of series elastic actuators

Grün, Markus; Müller, Roman; Konigorski, Ulrich

doi:10.1109/biorob.2012.6290300

Cited by 31 publications

(13 citation statements)

References 9 publications

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“…In [37], a PD torque controller was coupled to a disturbance observer to compensate for modelling errors and plant variations. This approach has been modified in [38] where also the model of the actuator was taken into account.…”

Section: Controlmentioning

confidence: 99%

Design and Characterization of a Novel High-Power Series Elastic Actuator for a Lower Limb Robotic Orthosis

Accoto

Carpino

Sergi

et al. 2013

International Journal of Advanced Robotic Systems

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A safe interaction is crucial in wearable robotics in general, while in assistive and rehabilitation applications, robots may also be required to minimally perturb physiological movements, ideally acting as perfectly transparent machines. The actuation system plays a central role because the expected performance, in terms of torque, speed and control bandwidth, must not be achieved at the expense of lightness and compactness. Actuators embedding compliant elements, such as series elastic actuators, can be designed to meet the above-mentioned requirements in terms of high energy storing capacity and stability of torque control. A number of series elastic actuators have been proposed over the past 20 years in order to accommodate the needs arising from specific applications. This paper presents a novel series elastic actuator intended for the actuation system of a lower limb wearable robot, recently developed in our lab. The actuator is able to deliver 300 W and has a novel architecture making its centre of mass not co-located with its axis of rotation, for an easier integration into the robotic structure. A custom-made torsion spring with a stiffness of 272.25 N·m·rad −1 is directly connected to the load. The delivered torque is calculated from the measurement of the spring deflection, through two absolute encoders. Testing on torque measurement accuracy and torque/stiffness control are reported.

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Section: Controlmentioning

confidence: 99%

Design and Characterization of a Novel High-Power Series Elastic Actuator for a Lower Limb Robotic Orthosis

Accoto

Carpino

Sergi

et al. 2013

International Journal of Advanced Robotic Systems

View full text Add to dashboard Cite

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“…D. Ragonesi established a torque controller utilizing PI controller [2]. Markus Grün proposes a force controller based on the dynamical model of SEA [3]. Nicholas Paine develops a force controller based on combinations of PID, model-based and disturbance observer [1].…”

Section: Introductionmentioning

confidence: 99%

Force Control of Series Elastic Actuator: Implications for Series Elastic Actuator Design

Huashan

2015

2015 Fifth International Conference on Instrumentation and Measurement, Computer, Communication and Control (IMCCC)

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The force controller of series elastic actuator (SEA) is an important issue, because it determines the output performance of SEA (the bandwidth and the resonant peak). However, the existing force controllers of SEA attach little importance to the determinants of the performance. This paper develops four different kinds of force controllers and selects the optimal controller by comparing their capabilities. The comparison demonstrates that the parameters of dynamical models are key factors affecting the output performance. Finally, the experiments reveal that the equivalent mass and the damping coefficient of SEA are determinants. The conclusion can provide theoretical implications to SEA design.

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“…For example, using a disturbance rejection approach, some uncertain dynamics in the human-robot interaction could be included as disturbance forces; in this case, the disturbance observer can be used to handle the uncertainty. The authors in [19] assumed that the disturbance is constant and designed a disturbance observer to reject the modeling error. In [29], the authors used a feedback plus feedforward force control, which was enhanced by a disturbance observer to compensate for plant variations, where feedback and feedforward controls were optimally designed.…”

Section: Introductionmentioning

confidence: 99%

“…The main contribution of this paper is that the proposed control method has the following improvements over those methods presented in [19], [29], and [30]: 1) The nonlinear friction in the actuation system is compensated for. This can help improve transparency of the assistive robot which interacts with the human.…”

Section: Introductionmentioning

confidence: 99%

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Human–Robot Interaction Control of Rehabilitation Robots With Series Elastic Actuators

et al. 2015

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Rehabilitation robots, by necessity, have direct physical interaction with humans. Physical interaction affects the controlled variables and may even cause system instability. Thus, human-robot interaction control design is critical in rehabilitation robotics research. This paper presents an interaction control strategy for a gait rehabilitation robot. The robot is driven by a novel compact series elastic actuator, which provides intrinsic compliance and backdrivablility for safe human-robot interaction. The control design is based on the actuator model with consideration of interaction dynamics. It consists mainly of human interaction compensation, friction compensation, and is enhanced with a disturbance observer. Such a control scheme enables the robot to achieve low output impedance when operating in human-in-charge mode and achieve accurate force tracking when operating in force control mode. Due to the direct physical interaction with humans, the controller design must also meet the stability requirement. A theoretical proof is provided to show the guaranteed stability of the closed-loop system under the proposed controller. The proposed design is verified with an ankle robot in walking experiments. The results can be readily extended to other rehabilitation and assistive robots driven with compliant actuators without much difficulty.

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Model based control of series elastic actuators

Cited by 31 publications

References 9 publications

Design and Characterization of a Novel High-Power Series Elastic Actuator for a Lower Limb Robotic Orthosis

Design and Characterization of a Novel High-Power Series Elastic Actuator for a Lower Limb Robotic Orthosis

Force Control of Series Elastic Actuator: Implications for Series Elastic Actuator Design

Human–Robot Interaction Control of Rehabilitation Robots With Series Elastic Actuators

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