Quiet standing was, for many years, studied as a single inverted pendulum, based on the principle... more Quiet standing was, for many years, studied as a single inverted pendulum, based on the principle that the ankle joint is the most important joint of this movement. However, studies show that hip and knee joints perform, as well, an important role in quiet standing. The aim of this paper is to present a three-segment-inverted pendulum model, using Lagrange’s dynamics, to study human quiet stance in the sagittal plane and, therefore, allow, in future work, its appliance to a lower-limb exoskeleton. As a preliminary study, lower limb kinematic and dynamic data were recorded from 15 healthy subjects while balancing using an optical motion capture system. The center-of-pressure (CoP) was calculated with reference to the ankle joint and the projection of the center-of-mass (CoM) in the sagittal plane was estimated, using the positions given by the mathematical model. The contributions of each joint to the estimated projection of CoM and CoP were also investigated. Finally, a correlation between joints kinematics and kinetics was also made. The first results show a good relationship between estimated CoM and CoP and between joints, supporting the theory that, together, the three joints control the body CoM and, thus, allow postural control.
Humanoid robots are a good option for rescue missions in disaster scenarios when the safety of th... more Humanoid robots are a good option for rescue missions in disaster scenarios when the safety of the rescue team can be compromised. Thus, allowing saving lives without the need of risking the safety of the rescue team. In this study we propose a reactive walking algorithm that provides statically stable locomotion when negotiating difficult terrains (combinations of inclined planes and flat ground) in the case that computer vision is not an option due to occluded terrains. Furthermore, we have tested the algorithm in simulation using the DRCSim software package obtaining good results.
Industrial Robot-an International Journal, Oct 20, 2014
Purpose – The purpose of this study is to present a variable stiffness actuator, one of whose mai... more Purpose – The purpose of this study is to present a variable stiffness actuator, one of whose main features is that the compliant elements simultaneously allow measuring of the torque exerted by the joint. Conceived as a force-controlled actuator, this actuator with Adjustable Rigidity and Embedded Sensor (ARES) is intended to be implemented in the knee of the ATLAS exoskeleton for children to allow the exploitation of the intrinsic dynamic during the locomotion cycle. Design/methodology/approach – A set of simulations were performed to evaluate the behavior of the actuator mechanism and a prototype of the variable impedance actuator was incorporated into the exoskeleton’s knee and evaluations of the torque measurements capabilities along with the rigidity adjustments were made. Findings – Mass and inertia of the actuator are minimized by the compact design and the utilization of the different component for more than one utility. By a proper match of the compliance of the joint and the performed task, good torque measurements can be achieved and no bandwidth saturation is expected. Originality/value – In the actuator, the compliant elements simultaneously allow measuring of the torque exerted by the join. By a proper match of the compliance of the joint and the performed task, good torque measurements can be achieved and no bandwidth saturation is expected.
Quiet standing was, for many years, studied as a single inverted pendulum, based on the principle... more Quiet standing was, for many years, studied as a single inverted pendulum, based on the principle that the ankle joint is the most important joint of this movement. However, studies show that hip and knee joints perform, as well, an important role in quiet standing. The aim of this paper is to present a three-segment-inverted pendulum model, using Lagrange’s dynamics, to study human quiet stance in the sagittal plane and, therefore, allow, in future work, its appliance to a lower-limb exoskeleton. As a preliminary study, lower limb kinematic and dynamic data were recorded from 15 healthy subjects while balancing using an optical motion capture system. The center-of-pressure (CoP) was calculated with reference to the ankle joint and the projection of the center-of-mass (CoM) in the sagittal plane was estimated, using the positions given by the mathematical model. The contributions of each joint to the estimated projection of CoM and CoP were also investigated. Finally, a correlation between joints kinematics and kinetics was also made. The first results show a good relationship between estimated CoM and CoP and between joints, supporting the theory that, together, the three joints control the body CoM and, thus, allow postural control.
Humanoid robots are a good option for rescue missions in disaster scenarios when the safety of th... more Humanoid robots are a good option for rescue missions in disaster scenarios when the safety of the rescue team can be compromised. Thus, allowing saving lives without the need of risking the safety of the rescue team. In this study we propose a reactive walking algorithm that provides statically stable locomotion when negotiating difficult terrains (combinations of inclined planes and flat ground) in the case that computer vision is not an option due to occluded terrains. Furthermore, we have tested the algorithm in simulation using the DRCSim software package obtaining good results.
Industrial Robot-an International Journal, Oct 20, 2014
Purpose – The purpose of this study is to present a variable stiffness actuator, one of whose mai... more Purpose – The purpose of this study is to present a variable stiffness actuator, one of whose main features is that the compliant elements simultaneously allow measuring of the torque exerted by the joint. Conceived as a force-controlled actuator, this actuator with Adjustable Rigidity and Embedded Sensor (ARES) is intended to be implemented in the knee of the ATLAS exoskeleton for children to allow the exploitation of the intrinsic dynamic during the locomotion cycle. Design/methodology/approach – A set of simulations were performed to evaluate the behavior of the actuator mechanism and a prototype of the variable impedance actuator was incorporated into the exoskeleton’s knee and evaluations of the torque measurements capabilities along with the rigidity adjustments were made. Findings – Mass and inertia of the actuator are minimized by the compact design and the utilization of the different component for more than one utility. By a proper match of the compliance of the joint and the performed task, good torque measurements can be achieved and no bandwidth saturation is expected. Originality/value – In the actuator, the compliant elements simultaneously allow measuring of the torque exerted by the join. By a proper match of the compliance of the joint and the performed task, good torque measurements can be achieved and no bandwidth saturation is expected.
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Papers by Daniel Sanz-Merodio