Varying mechanical compliance benefits energy efficiency of a knee joint actuator

Baček, Tomislav; Moltedo, Marta; Geeroms, Joost; Vanderborght, Bram; Rodriguez–Guerrero, Carlos; Lefeber, Dirk

doi:10.1016/j.mechatronics.2019.102318

Cited by 10 publications

(7 citation statements)

References 51 publications

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“…The second parameter investigated in this study is the actuator's stiffness level. The influence of this parameter on the actuator's performance has been already shown in several test-bench experiments [37,40]. In [37] it was shown that no single stiffness level of the ankle actuator used in the MAPO could be defined as optimal based on the actuator's torque tracking performance, due to the dependence of the benefits of a specific actuator's stiffness level on both the assistive torque reference and the user's ankle kinematics.…”

Section: Introductionmentioning

confidence: 93%

Walking with a powered ankle-foot orthosis: the effects of actuation timing and stiffness level on healthy users

Moltedo

Baček

Serrien

et al. 2020

J NeuroEngineering Rehabil

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Background: In the last decades, several powered ankle-foot orthoses have been developed to assist the ankle joint of their users during walking. Recent studies have shown that the effects of the assistance provided by powered ankle-foot orthoses depend on the assistive profile. In compliant actuators, the stiffness level influences the actuator's performance. However, the effects of this parameter on the users has not been yet evaluated. The goal of this study is to assess the effects of the assistance provided by a variable stiffness ankle actuator on healthy young users. More specifically, the effect of different onset times of the push-off torque and different actuator's stiffness levels has been investigated. Methods: Eight healthy subjects walked with a unilateral powered ankle-foot orthosis in several assisted walking trials. The powered orthosis was actuated in the sagittal plane by a variable stiffness actuator. During the assisted walking trials, three different onset times of the push-off assistance and three different actuator's stiffness levels were used. The metabolic cost of walking, lower limb muscles activation, joint kinematics, and gait parameters measured during different assisted walking trials were compared to the ones measured during normal walking and walking with the powered orthosis not providing assistance. Results: This study found trends for more compliant settings of the ankle actuator resulting in bigger reductions of the metabolic cost of walking and soleus muscle activation in the stance phase during assisted walking as compared to the unassisted walking trial. In addition to this, the study found that, among the tested onset times, the earlier ones showed a trend for bigger reductions of the activation of the soleus muscle during stance, while the later ones led to a bigger reduction in the metabolic cost of walking in the assisted walking trials as compared to the unassisted condition. Conclusions: This study presents a first attempt to show that, together with the assistive torque profile, also the stiffness level of a compliant ankle actuator can influence the assistive performance of a powered ankle-foot orthosis.

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Section: Introductionmentioning

confidence: 93%

Walking with a powered ankle-foot orthosis: the effects of actuation timing and stiffness level on healthy users

Moltedo

Baček

Serrien

et al. 2020

J NeuroEngineering Rehabil

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“…1). The actuator's defining features are a simple rotational joint (viable choice for knee orthosis [25], [32]), anthropomorphic shape designed to minimise potential negative effects of its 2.2 kg mass [33], and a spring in series with an EC motor to deliver torque in the sagittal plane (see [34], [35] for detailed actuator specifications and performance).…”

Section: A Knee Joint Orthosismentioning

confidence: 99%

“…The motor is controlled at a low level using a controller provided by the manufacturer. This cascaded controller allows reliable delivery of any desired torque within the actuator's hardware/software limitations without measuring the torque [35].…”

Section: B Control Architecturementioning

confidence: 99%

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Human Musculoskeletal and Energetic Adaptations to Unilateral Robotic Knee Gait Assistance

Baček

Moltedo

Serrien

et al. 2022

IEEE Trans. Biomed. Eng.

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This paper aims to analyse the human musculoskeletal and energetic adaptation mechanisms when physically interacting with a unilateral knee orthosis during treadmill walking. Methods: Test subjects participated in two walking trials, whereby the orthosis was controlled to deliver five predefined torque profiles of different duration (as % of a gait cycle). The adaptations to assistive torques of different duration were analysed in terms of gait parameters, metabolic effort, and muscle activity. Results: Orthotic assistance's kinematic effects remain local to the assisted leg and joint, unlike the muscles spanning the knee joint, which engage in a balancing-out action to retain stability. Duration of assistive torque significantly affects only the timing of the knee joint's peak flexion angle in the stance phase, while the observed joint kinematics and muscle activity demonstrate different recovery times upon changing robotic support (washout effects). Conclusion: Human body adaptations to external robotic knee joint assistance during walking take place on multiple levels and to a different extent in a joint effort to keep the gait stable. Significance: This paper provides important insights into the human body's multiple adaptation mechanisms in the presence of external robotic assistance.

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“…In Li et al (2019), a compliant crank-slider mechanism can be constructed by adding constant-stiffness springs at its joints. In Baček et al (2020), the authors analyzed the effects that changing mechanical compliance has on the actuator's overall performance in different ideal conditions in an experimental test setup.…”

Section: Introductionmentioning

confidence: 99%

Biped Robots With Compliant Joints for Walking and Running Performance Growing

Maiorino

Muscolo

2020

Front. Mech. Eng.

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This paper deals with the problem of compliance in biped robots locomotion. After a first literature review, we designed and simulated a 3D virtual model of a biped robot conceived with the same link dimensions (and weights) of a standard man. In all simulation, the same input to the robot actuators are proposed, modifying only the compliance of the attached links. We first validated the model and then compared results increasing and reducing compliance on hip, knee and ankle joints. The very good results underline how the robot performances may be increased including the compliant element in the knee. In particular, we noted how including a proper value of the compliance in the knee, power and torque of the actuators may be reduced increasing robot speed.

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Varying mechanical compliance benefits energy efficiency of a knee joint actuator

Cited by 10 publications

References 51 publications

Walking with a powered ankle-foot orthosis: the effects of actuation timing and stiffness level on healthy users

Walking with a powered ankle-foot orthosis: the effects of actuation timing and stiffness level on healthy users

Human Musculoskeletal and Energetic Adaptations to Unilateral Robotic Knee Gait Assistance

Biped Robots With Compliant Joints for Walking and Running Performance Growing

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