The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
Gregory S Sawicki - One of the best experts on this subject based on the ideXlab platform.
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A benchtop biorobotic platform for in vitro observation of Muscle-tendon dynamics with parallel mechanical assistance from an elastic exoskeleton
Journal of Biomechanics, 2017Co-Authors: Benjamin D Robertson, Siddarth Vadakkeveedu, Gregory S SawickiAbstract:We present a novel biorobotic framework comprised of a Biological Muscle-tendon unit (MTU) mechanically coupled to a feedback controlled robotic environment simulation that mimics in vivo inertial/gravitational loading and mechanical assistance from a parallel elastic exoskeleton. Using this system, we applied select combinations of Biological Muscle activation (modulated with rate-coded direct neural stimulation) and parallel elastic assistance (applied via closed-loop mechanical environment simulation) hypothesized to mimic human behavior based on previously published modeling studies. These conditions resulted in constant system-level force-length dynamics (i.e., stiffness), reduced Biological loads, increased Muscle excursion, and constant Muscle average positive power output—all consistent with laboratory experiments on intact humans during exoskeleton assisted hopping. Mechanical assistance led to reduced estimated metabolic cost and MTU apparent efficiency, but increased apparent efficiency for the MTU + Exo system as a whole. Findings from this study suggest that the increased natural resonant frequency of the artificially stiffened MTU + Exo system, along with invariant movement frequencies, may underlie observed limits on the benefits of exoskeleton assistance. Our novel approach demonstrates that it is possible to capture the salient features of human locomotion with exoskeleton assistance in an isolated Muscle-tendon preparation, and introduces a powerful new tool for detailed, direct examination of how assistive devices affect Muscle-level neuromechanics and energetics.
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An In Vitro Approach for Directly Observing Muscle-Tendon Dynamics with Parallel Elastic Mechanical Assistance
Converging Clinical and Engineering Research on Neurorehabilitation II, 2016Co-Authors: Gregory S Sawicki, Benjamin D RobertsonAbstract:Lower-limb exoskeletons are a promising tool for restoring or augmenting locomotion performance. While engineering advances have led to marked improvements on the machine side of the human machine interface, fundamental aspects of the physiological response of the human user remain unknown—especially at the level of individual leg Muscles. One complication is that it is difficult to make direct measurements from Muscles in humans without being invasive. Here we offer a novel benchtop approach by introducing a ‘smart’ robotic interface into the framework of Biological Muscle-tendon work loop experiments in order to simulate the local dynamical environment Muscles experience in vivo during locomotion with exoskeleton assistance. Using this framework we demonstrate that providing force in parallel with a Muscle-tendon using an ‘exo-tendon’ can have unintended consequences, disrupting the ‘tuned’ spring-like mechanics of the underlying Biological Muscle tendon unit.
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unconstrained Muscle tendon workloops indicate resonance tuning as a mechanism for elastic limb behavior during terrestrial locomotion
Proceedings of the National Academy of Sciences of the United States of America, 2015Co-Authors: Benjamin D Robertson, Gregory S SawickiAbstract:In terrestrial locomotion, there is a missing link between observed spring-like limb mechanics and the physiological systems driving their emergence. Previous modeling and experimental studies of bouncing gait (e.g., walking, running, hopping) identified Muscle-tendon interactions that cycle large amounts of energy in series tendon as a source of elastic limb behavior. The neural, biomechanical, and environmental origins of these tuned mechanics, however, have remained elusive. To examine the dynamic interplay between these factors, we developed an experimental platform comprised of a feedback-controlled servo-motor coupled to a Biological Muscle-tendon. Our novel motor controller mimicked in vivo inertial/gravitational loading experienced by Muscles during terrestrial locomotion, and rhythmic patterns of Muscle activation were applied via stimulation of intact nerve. This approach was based on classical workloop studies, but avoided predetermined patterns of Muscle strain and activation-constraints not imposed during real-world locomotion. Our unconstrained approach to position control allowed observation of emergent Muscle-tendon mechanics resulting from dynamic interaction of neural control, active Muscle, and system material/inertial properties. This study demonstrated that, despite the complex nonlinear nature of musculotendon systems, cyclic Muscle contractions at the passive natural frequency of the underlying biomechanical system yielded maximal forces and fractions of mechanical work recovered from previously stored elastic energy in series-compliant tissues. By matching movement frequency to the natural frequency of the passive biomechanical system (i.e., resonance tuning), Muscle-tendon interactions resulting in spring-like behavior emerged naturally, without closed-loop neural control. This conceptual framework may explain the basis for elastic limb behavior during terrestrial locomotion.
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EMBC - Influence of parallel spring-loaded exoskeleton on ankle Muscle-tendon dynamics during simulated human hopping
Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Inte, 2011Co-Authors: Benjamin D Robertson, Gregory S SawickiAbstract:Robotic assistance for rehabilitation and enhancement of human locomotion has become a major goal of biomedical engineers in recent years. While significant progress to this end has been made in the fields of neural interfacing and control systems, little has been done to examine the effects of mechanical assistance on the biomechanics of underlying Muscle-tendon systems. Here, we model the effects of mechanical assistance via a passive spring acting in parallel with the triceps surae-Achilles tendon complex during cyclic hopping in humans. We examine system dynamics over a range of Biological Muscle activation and exoskeleton spring stiffness. We find that, in most cases, uniform cyclic mechanical power production of the coupled system is achieved. Furthermore, unassisted power production can be reproduced throughout parameter space by trading off decreases in Muscle activation with increases in ankle exoskeleton spring stiffness. In addition, we show that as mechanical assistance increases the Biological Muscle-tendon unit becomes less ‘tuned’ resulting in higher mechanical power output from active components of Muscle despite large reductions in required force output.
Benjamin D Robertson - One of the best experts on this subject based on the ideXlab platform.
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A benchtop biorobotic platform for in vitro observation of Muscle-tendon dynamics with parallel mechanical assistance from an elastic exoskeleton
Journal of Biomechanics, 2017Co-Authors: Benjamin D Robertson, Siddarth Vadakkeveedu, Gregory S SawickiAbstract:We present a novel biorobotic framework comprised of a Biological Muscle-tendon unit (MTU) mechanically coupled to a feedback controlled robotic environment simulation that mimics in vivo inertial/gravitational loading and mechanical assistance from a parallel elastic exoskeleton. Using this system, we applied select combinations of Biological Muscle activation (modulated with rate-coded direct neural stimulation) and parallel elastic assistance (applied via closed-loop mechanical environment simulation) hypothesized to mimic human behavior based on previously published modeling studies. These conditions resulted in constant system-level force-length dynamics (i.e., stiffness), reduced Biological loads, increased Muscle excursion, and constant Muscle average positive power output—all consistent with laboratory experiments on intact humans during exoskeleton assisted hopping. Mechanical assistance led to reduced estimated metabolic cost and MTU apparent efficiency, but increased apparent efficiency for the MTU + Exo system as a whole. Findings from this study suggest that the increased natural resonant frequency of the artificially stiffened MTU + Exo system, along with invariant movement frequencies, may underlie observed limits on the benefits of exoskeleton assistance. Our novel approach demonstrates that it is possible to capture the salient features of human locomotion with exoskeleton assistance in an isolated Muscle-tendon preparation, and introduces a powerful new tool for detailed, direct examination of how assistive devices affect Muscle-level neuromechanics and energetics.
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An In Vitro Approach for Directly Observing Muscle-Tendon Dynamics with Parallel Elastic Mechanical Assistance
Converging Clinical and Engineering Research on Neurorehabilitation II, 2016Co-Authors: Gregory S Sawicki, Benjamin D RobertsonAbstract:Lower-limb exoskeletons are a promising tool for restoring or augmenting locomotion performance. While engineering advances have led to marked improvements on the machine side of the human machine interface, fundamental aspects of the physiological response of the human user remain unknown—especially at the level of individual leg Muscles. One complication is that it is difficult to make direct measurements from Muscles in humans without being invasive. Here we offer a novel benchtop approach by introducing a ‘smart’ robotic interface into the framework of Biological Muscle-tendon work loop experiments in order to simulate the local dynamical environment Muscles experience in vivo during locomotion with exoskeleton assistance. Using this framework we demonstrate that providing force in parallel with a Muscle-tendon using an ‘exo-tendon’ can have unintended consequences, disrupting the ‘tuned’ spring-like mechanics of the underlying Biological Muscle tendon unit.
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unconstrained Muscle tendon workloops indicate resonance tuning as a mechanism for elastic limb behavior during terrestrial locomotion
Proceedings of the National Academy of Sciences of the United States of America, 2015Co-Authors: Benjamin D Robertson, Gregory S SawickiAbstract:In terrestrial locomotion, there is a missing link between observed spring-like limb mechanics and the physiological systems driving their emergence. Previous modeling and experimental studies of bouncing gait (e.g., walking, running, hopping) identified Muscle-tendon interactions that cycle large amounts of energy in series tendon as a source of elastic limb behavior. The neural, biomechanical, and environmental origins of these tuned mechanics, however, have remained elusive. To examine the dynamic interplay between these factors, we developed an experimental platform comprised of a feedback-controlled servo-motor coupled to a Biological Muscle-tendon. Our novel motor controller mimicked in vivo inertial/gravitational loading experienced by Muscles during terrestrial locomotion, and rhythmic patterns of Muscle activation were applied via stimulation of intact nerve. This approach was based on classical workloop studies, but avoided predetermined patterns of Muscle strain and activation-constraints not imposed during real-world locomotion. Our unconstrained approach to position control allowed observation of emergent Muscle-tendon mechanics resulting from dynamic interaction of neural control, active Muscle, and system material/inertial properties. This study demonstrated that, despite the complex nonlinear nature of musculotendon systems, cyclic Muscle contractions at the passive natural frequency of the underlying biomechanical system yielded maximal forces and fractions of mechanical work recovered from previously stored elastic energy in series-compliant tissues. By matching movement frequency to the natural frequency of the passive biomechanical system (i.e., resonance tuning), Muscle-tendon interactions resulting in spring-like behavior emerged naturally, without closed-loop neural control. This conceptual framework may explain the basis for elastic limb behavior during terrestrial locomotion.
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EMBC - Influence of parallel spring-loaded exoskeleton on ankle Muscle-tendon dynamics during simulated human hopping
Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Inte, 2011Co-Authors: Benjamin D Robertson, Gregory S SawickiAbstract:Robotic assistance for rehabilitation and enhancement of human locomotion has become a major goal of biomedical engineers in recent years. While significant progress to this end has been made in the fields of neural interfacing and control systems, little has been done to examine the effects of mechanical assistance on the biomechanics of underlying Muscle-tendon systems. Here, we model the effects of mechanical assistance via a passive spring acting in parallel with the triceps surae-Achilles tendon complex during cyclic hopping in humans. We examine system dynamics over a range of Biological Muscle activation and exoskeleton spring stiffness. We find that, in most cases, uniform cyclic mechanical power production of the coupled system is achieved. Furthermore, unassisted power production can be reproduced throughout parameter space by trading off decreases in Muscle activation with increases in ankle exoskeleton spring stiffness. In addition, we show that as mechanical assistance increases the Biological Muscle-tendon unit becomes less ‘tuned’ resulting in higher mechanical power output from active components of Muscle despite large reductions in required force output.
Joseph M. Schimmels - One of the best experts on this subject based on the ideXlab platform.
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Design of a Quadratic, Antagonistic, Cable-Driven, Variable Stiffness Actuator
Journal of Mechanisms and Robotics, 2021Co-Authors: Ryan Moore, Joseph M. SchimmelsAbstract:Abstract Antagonistically actuated variable stiffness actuators (VSAs) take inspiration from Biological Muscle structures to control both the stiffness and positioning of a joint. This paper presents the design of an elastic mechanism that utilizes a cable running through a set of three pulleys to displace a linear spring, yielding quadratic spring behavior in each actuator. A joint antagonistically actuated by two such mechanisms yields a linear relationship between force and deflection from a selectable equilibrium position. A quasi-static model is used to optimize the mechanism. Testing of the fabricated prototype yielded a good match to the desired elastic behavior.
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Design of a Quadratic, Antagonistic, Cable-Driven, Variable Stiffness Actuator
Volume 10: 44th Mechanisms and Robotics Conference (MR), 2020Co-Authors: Ryan Moore, Joseph M. SchimmelsAbstract:Abstract Antagonistically actuated Variable Stiffness Actuators (VSAs) take inspiration from Biological Muscle structures to control both the stiffness and positioning of a joint. The design presented utilizes a cable running through a set of three pulleys, to displace a linear spring, yielding quadratic spring behavior. A quasi-static model of the mechanism is used to assess and optimize the force-displacement behavior. The mechanism prototype yielded a good match to the desired elastic behavior.
H. Harry Asada - One of the best experts on this subject based on the ideXlab platform.
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Broadcast Control for a Large Array of Stochastically Controlled Piezoelectric Actuators
Microbiorobotics, 2012Co-Authors: Jun Ueda, H. Harry AsadaAbstract:A cellular actuator concept inspired by Biological Muscle structure connects many small actuator units in series or in parallel and composes in totality a single actuator. Piezoelectric ceramic material, such as lead zirconate titanate (PZT), has large stress and bandwidth, but its extremely small strain, i.e., only 0.1%, has been a major bottleneck for broad applications. A strain amplification design that increases strain exponentially through its hierarchical cellular structure is presented. Piezoelectric cellular actuators using the strain amplification are developed for over 20% strain that is comparable to natural skeletal Muscles. By applying this architecture, a cellular actuator with tunable resonant frequencies is developed. A stochastic control method, named “broadcast control,” for coordinating a vast number of actuator units is presented. The broadcast control method can tolerate a certain level of non-uniformities and failures, having high robust performances.
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Broadcast Feedback of Stochastic Cellular Actuators Inspired by Biological Muscle Control
The International Journal of Robotics Research, 2007Co-Authors: Jun Ueda, Lael U. Odhner, H. Harry AsadaAbstract:This paper presents a broadcast feedback approach to the distributed stochastic control of an actuator system consisting of many cellular units. This control architecture was inspired by skeletal Muscles comprising a vast number of tiny functional units, called sarcomeres. The output of the actuator system is an aggregate e fect of numerous cellular units, each taking a bistable ON—OFF state. A central controller “broadcasts” the error between the aggregate output and a reference input. Rather than ordering the individual units to take specific states, the central controller merely broadcasts the overall error signal to all the cellular units uniformly. In turn each cellular unit makes a stochastic decision with a state transition probability, which is modulated in relation to the broadcasted error. Stochastic properties of both open-loop and closed-loop control systems are analyzed. Stability conditions of the broadcast feedback system are obtained by using a stochastic Lyapunov function. The proposed method is simulated for an artificial cellular actuator, consisting of many segments of smart actuator material. Theoretical results are verified through simulation. It is demonstrated that, even in the absence of deterministic coordination, the ensemble of the cellular units can track a given trajectory stably and robustly.
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broadcast feedback of large scale distributed stochastic control systems inspired by Biological Muscle control
American Control Conference, 2007Co-Authors: Jun Ueda, Lael U. Odhner, H. Harry AsadaAbstract:This paper presents a broadcast feedback approach to the distributed stochastic control of an actuator system consisting of many cellular units. This control architecture was inspired by skeletal Muscles comprising a vast number of tiny functional units, called sarcomeres. The output of the actuator system is an aggregate effect of numerous cellular units, each taking a bistable on-off state. A central controller "broadcasts" the error between the aggregate output and a reference input. Rather than dictating the individual units to take specific states, the central controller merely broadcasts the overall error signal to all the cellular units uniformly. In turn each cellular unit makes a stochastic decision with a state transition probability, which is modulated in relation to the broadcasted error. Stability conditions of the broadcast feedback system are obtained by using a stochastic Lyapunov function. It is demonstrated that, even in the absence of deterministic coordination, the ensemble of the cellular units can track a given trajectory stably and robustly.
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ACC - Broadcast Feedback of Large-Scale, Distributed Stochastic Control Systems Inspired by Biological Muscle Control
2007 American Control Conference, 2007Co-Authors: Jun Ueda, Lael U. Odhner, H. Harry AsadaAbstract:This paper presents a broadcast feedback approach to the distributed stochastic control of an actuator system consisting of many cellular units. This control architecture was inspired by skeletal Muscles comprising a vast number of tiny functional units, called sarcomeres. The output of the actuator system is an aggregate effect of numerous cellular units, each taking a bistable on-off state. A central controller "broadcasts" the error between the aggregate output and a reference input. Rather than dictating the individual units to take specific states, the central controller merely broadcasts the overall error signal to all the cellular units uniformly. In turn each cellular unit makes a stochastic decision with a state transition probability, which is modulated in relation to the broadcasted error. Stability conditions of the broadcast feedback system are obtained by using a stochastic Lyapunov function. It is demonstrated that, even in the absence of deterministic coordination, the ensemble of the cellular units can track a given trajectory stably and robustly.
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IROS - Segmentation architecture of multi-axis SMA array actuators inspired by Biological Muscles
2004 IEEE RSJ International Conference on Intelligent Robots and Systems (IROS) (IEEE Cat. No.04CH37566), 1Co-Authors: Kyu-jin Cho, H. Harry AsadaAbstract:A new approach to artificial Muscle actuators assimilating the morphological and kinesiological structure of Biological Muscles is presented and is implemented using shape memory alloys. Like a Biological Muscle consisting of short Muscle fibers arranged in an overlapping series, an array of SMA actuators are segmented into many independently controlled, spatially discrete volumes, each contributing a small displacement to create a large motion. Furthermore, the segmented architecture of SMA wires is extended to a multi-axis actuator array by arranging them in a two-dimensional array. The multi-axis control is streamlined and coordinated using a two-dimensional segmentation method in order to activate multiple bones (links) of a skeletal robot structure in a coordinated manner. Moreover, the 2-D segmentation is so designed that coordinated gross motion as well as independent fine movements may be generated with minimum complexity and minimum control loops.
Byungkyu Kim - One of the best experts on this subject based on the ideXlab platform.
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Investigation of generative contactile force of frog Muscle under electrical stimulation
Journal of Mechanical Science and Technology, 2006Co-Authors: Sukho Park, Byungkyu Kim, Changyeol Jee, Jiwoon Kwon, Sungjin Park, Jongoh ParkAbstract:Recently, the microrobots powered by Biological Muscle actuators were proposed. Among the Biological Muscle actuators, frog Muscle is well known as a good Muscle actuator and has a large displacement, actuation forces and piezoelectric properties. Therefore, for the application of the biomimetic microrobot, this paper reports the electromechanical properties of frog Muscle. First of all, the experimental setup has been established for measuring generative force of the frog Muscle. Through the various electrical stimulating inputs to the frog Muscle, we measured the contractile force of the frog Muscle. From the measuring results, we found that the actuating contractile force responses of the frog Muscle are determined by the amplitude, frequency, duty ratio, and wave form of the stimulation signal. This study will be beneficial for the development of the microrobot actuated by frog Muscle.
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Contractile force measurements of cardiac myocytes using a micro-manipulation system
Journal of Mechanical Science and Technology, 2006Co-Authors: Sukho Park, Seokkyu Ryu, Seok Chang Ryu, Deok-ho Kim, Byungkyu KimAbstract:In order to develop a cell based robot, we present a micro-mechanical force measurement system for the Biological Muscle actuators, which utilize glucose as a power source. The proposed measurement system is composed of a micro-manipulator, a force transducer with a glass probe, a signal processor, an inverted microscope and video recording system. Using this measurement system, the contractile force and frequency of the cardiac myocytes were measured in real time and the magnitudes of the contractile force of each cardiac myocyte under different conditions were compared. From the quantitative experimental results, we could estimate that the force of cardiac myocytes is about 20~40 μN, and show that there are differences between the control cells and the micro-patterned cells.
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Comparative Quantification of Contractile Force of Cardiac Muscle Using a Micro-mechanical Force Sensing System
2005Co-Authors: Seok Chang Ryu, Sukho Park, Deok-ho Kim, Byungkyu KimAbstract:To facilitate the cell based robot research, we presented a micro-mechanical force measurement system for the Biological Muscle actuators, which utilize glucose as a power source for potential application in a human body or blood vessels. The system is composed of a micro-manipulator, a force transducer with a glass probe, a signal processor, an inverted microscope and video recoding system. Using this measurement system, the contractile force and frequency of the cardiac myocytes were measured in real time and the magnitude of the contractile force of each cardiac myocyte on a different condition was compared. From the quantitative experimental results, we estimated that the force of cardiac myocytes is about 20~40 μN, and showed that there is difference between the control cells and the micro-patterned cells. Index Terms – Cardiac myocytes, Cell force measurement, Micro-manipulation, Piezo resistive sensor.
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IROS - Contractile force measurements of cardiac myocytes using a micro-manipulation system
2005 IEEE RSJ International Conference on Intelligent Robots and Systems, 2005Co-Authors: Sukho Park, Seok Chang Ryu, Deok-ho Kim, Byungkyu KimAbstract:Recently, the microrobot powered by Biological Muscle actuators was proposed. The cell based actuator utilizes glucose as a power source and thus can apply to the application of a human body or blood vessels. For the structural design of the cell based micro-robot, the contractile force of the Muscle powered by cardiac myocytes should be measured. In addition, the contractile force measurement can be used in the static or dynamic simulations of the micro-robot. In this paper, the contractile force measurement system, which is composed of a micro-manipulator, a force transducer, a signal processor and an inverted microscope is proposed. By using the measuring system, the contractile force for both control and micro-patterned cardiac myocytes are measured. From the experimental results, we estimated that the contractile force of cardiac myocytes is about 20-40 /spl mu/N when it is compared between the control cell and the cell on micro-pattern.