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Fosha RA, Matsangas P, Cravalho PF, Thornburg KM. Small Boat Recovery Task Performance in a Moving Environment. HUMAN FACTORS 2024; 66:209-220. [PMID: 35166615 DOI: 10.1177/00187208211065504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
OBJECTIVE Assess operator performance in a simulation of US Coast Guard small boat recovery to a larger vessel on a large scale, six degree-of-freedom, full motion simulator. BACKGROUND Studies of human performance in small boat recovery task have never been conducted on a high amplitude, low frequency simulator. Empirical evidence of small boat recovery task performance in challenging motion conditions is needed to inform future maritime systems designs. METHOD Experienced active-duty boat crewmembers (N = 13) conducted a small boat recovery task in three sea states on the Vertical Motion Simulator (VMS) at the NASA Ames Research Center. Task performance was assessed using a task equivalent for time to complete the task. Participant behaviors associated with increasing motion severity were observed. RESULTS Task performance declined as motion conditions became more severe. Participants were more likely to use at least one hand to maintain balance during motion conditions, becoming more frequent with increasing motion severity. Many participants used one hand to complete the task despite contrary instructions and previous experience. CONCLUSION Two design recommendations were proposed to counter declining task performance in increasingly severe motion conditions. Handholds available to participants during the task, and task design supporting single handed completion were recommended for small boat recovery systems. APPLICATION This research is directly applicable to gross motor tasks requiring simultaneous maintenance of balance in a maritime environment, and may be extended to other environments where humans experience complex motions while completing tasks.
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Affiliation(s)
- Rebecca A Fosha
- Human Systems Integration Division, USCG Headquarters, Washington, DC, USA
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2
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Shanbhag J, Wolf A, Wechsler I, Fleischmann S, Winkler J, Leyendecker S, Eskofier BM, Koelewijn AD, Wartzack S, Miehling J. Methods for integrating postural control into biomechanical human simulations: a systematic review. J Neuroeng Rehabil 2023; 20:111. [PMID: 37605197 PMCID: PMC10440942 DOI: 10.1186/s12984-023-01235-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Accepted: 08/09/2023] [Indexed: 08/23/2023] Open
Abstract
Understanding of the human body's internal processes to maintain balance is fundamental to simulate postural control behaviour. The body uses multiple sensory systems' information to obtain a reliable estimate about the current body state. This information is used to control the reactive behaviour to maintain balance. To predict a certain motion behaviour with knowledge of the muscle forces, forward dynamic simulations of biomechanical human models can be utilized. We aim to use predictive postural control simulations to give therapy recommendations to patients suffering from postural disorders in the future. It is important to know which types of modelling approaches already exist to apply such predictive forward dynamic simulations. Current literature provides different models that aim to simulate human postural control. We conducted a systematic literature research to identify the different approaches of postural control models. The different approaches are discussed regarding their applied biomechanical models, sensory representation, sensory integration, and control methods in standing and gait simulations. We searched on Scopus, Web of Science and PubMed using a search string, scanned 1253 records, and found 102 studies to be eligible for inclusion. The included studies use different ways for sensory representation and integration, although underlying neural processes still remain unclear. We found that for postural control optimal control methods like linear quadratic regulators and model predictive control methods are used less, when models' level of details is increasing, and nonlinearities become more important. Considering musculoskeletal models, reflex-based and PD controllers are mainly applied and show promising results, as they aim to create human-like motion behaviour considering physiological processes.
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Affiliation(s)
- Julian Shanbhag
- Engineering Design, Department of Mechanical Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.
| | - Alexander Wolf
- Engineering Design, Department of Mechanical Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Iris Wechsler
- Engineering Design, Department of Mechanical Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Sophie Fleischmann
- Machine Learning and Data Analytics Lab, Department Artificial Intelligence in Biomedical Engineering (AIBE), Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Jürgen Winkler
- Department of Molecular Neurology, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Sigrid Leyendecker
- Institute of Applied Dynamics, Department of Mechanical Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Bjoern M Eskofier
- Machine Learning and Data Analytics Lab, Department Artificial Intelligence in Biomedical Engineering (AIBE), Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Anne D Koelewijn
- Machine Learning and Data Analytics Lab, Department Artificial Intelligence in Biomedical Engineering (AIBE), Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Sandro Wartzack
- Engineering Design, Department of Mechanical Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Jörg Miehling
- Engineering Design, Department of Mechanical Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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Standing Balance Control of a Bipedal Robot Based on Behavior Cloning. Biomimetics (Basel) 2022; 7:biomimetics7040232. [PMID: 36546932 PMCID: PMC9776061 DOI: 10.3390/biomimetics7040232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 12/03/2022] [Accepted: 12/07/2022] [Indexed: 12/14/2022] Open
Abstract
Bipedal robots have gained increasing attention for their human-like mobility which allows them to work in various human-scale environments. However, their inherent instability makes it difficult to control their balance while they are physically interacting with the environment. This study proposes a novel balance controller for bipedal robots based on a behavior cloning model as one of the machine learning techniques. The behavior cloning model employs two deep neural networks (DNNs) trained on human-operated balancing data, so that the trained model can predict the desired wrench required to maintain the balance of the bipedal robot. Based on the prediction of the desired wrench, the joint torques for both legs are calculated using robot dynamics. The performance of the developed balance controller was validated with a bipedal lower-body robotic system through simulation and experimental tests by providing random perturbations in the frontal plane. The developed balance controller demonstrated superior performance with respect to resistance to balance loss compared to the conventional balance control method, while generating a smoother balancing movement for the robot.
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Sozzi S, Do MC, Schieppati M. Vertical ground reaction force oscillation during standing on hard and compliant surfaces: The “postural rhythm”. Front Neurol 2022; 13:975752. [PMID: 36119676 PMCID: PMC9475112 DOI: 10.3389/fneur.2022.975752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 08/10/2022] [Indexed: 11/14/2022] Open
Abstract
When a person stands upright quietly, the position of the Centre of Mass (CoM), the vertical force acting on the ground and the geometrical configuration of body segments is accurately controlled around to the direction of gravity by multiple feedback mechanisms and by integrative brain centres that coordinate multi-joint movements. This is not always easy and the postural muscles continuously produce appropriate torques, recorded as ground reaction force by a force platform. We studied 23 young adults during a 90 s period, standing at ease on a hard (Solid) and on a compliant support (Foam) with eyes open (EO) and with eyes closed (EC), focusing on the vertical component of the ground reaction force (VGRF). Analysis of VGRF time series gave the amplitude of their rhythmic oscillations (the root mean square, RMS) and of their frequency spectrum. Sway Area and Path Length of the Centre of Pressure (CoP) were also calculated. VGRF RMS (as well as CoP sway measures) increased in the order EO Solid ≈ EC Solid < EO Foam < EC Foam. The VGRF frequency spectra featured prevailing frequencies around 4–5 Hz under all tested conditions, slightly higher on Solid than Foam support. Around that value, the VGRF frequencies varied in a larger range on hard than on compliant support. Sway Area and Path Length were inversely related to the prevailing VGRF frequency. Vision compared to no-vision decreased Sway Area and Path Length and VGRF RMS on Foam support. However, no significant effect of vision was found on VGRF mean frequency for either base of support condition. A description of the VGRF, at the interface between balance control mechanisms and sway of the CoP, can contribute information on how upright balance is maintained. Analysis of the frequency pattern of VGRF oscillations and its role in the maintenance of upright stance should complement the traditional measures of CoP excursions in the horizontal plane.
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Affiliation(s)
- Stefania Sozzi
- Istituti Clinici Scientifici Maugeri IRCCS, Centro Studi Attività Motorie (CSAM), Pavia, Italy
| | - Manh-Cuong Do
- Complexité, Innovation, Activités Motrices et Sportives (CIAMS), Université Paris-Saclay, Orsay, France
- Complexité, Innovation, Activités Motrices et Sportives (CIAMS), Université d'Orléans, Orléans, France
| | - Marco Schieppati
- Istituti Clinici Scientifici Maugeri IRCCS, Centro Studi Attività Motorie (CSAM), Pavia, Italy
- *Correspondence: Marco Schieppati ;
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Effectiveness of Custom Foot Insoles to Decrease Plantar Pressure: A Cross-over Randomized Trial Study. Healthcare (Basel) 2022; 10:healthcare10030575. [PMID: 35327053 PMCID: PMC8948636 DOI: 10.3390/healthcare10030575] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 03/14/2022] [Accepted: 03/18/2022] [Indexed: 11/17/2022] Open
Abstract
Background: Harderness insoles decrease plantar pressure and reduce the foot injury incidence in sport. The purpose of our study was to analyze the plantar pressure variation in moto riders after riding in a real speed circuit with a custom foot 520 Shore EVA insole. Methods: A crossover randomized trial study was performed (consent no. #050520165316). Riders were assessed by an expert motorsport senior podiatry. The participants’ mean age was 35 ± 3.29. Participants completed a 20 min training riding with their own motorcycle in a real speed circuit. Plantar pressures were registered with a baropodometric platform evaluating an Ethyl Vinyl Acetate custom foot insole (CFI) manufactured with 3 mm thickness and 52° Shore A hardness. The Plantar pressures were registered before riding, after riding without EVA insole, and after riding with EVA insole. Results: Total Plantar pressures in right and left foot, and total surface area decrease after riding with EVA insoles. Conclusion: The use of an EVA insole with 520 shore A hardness riding on a motorcycle in speed circuit decreased the total plantar pressures and surface areas values.
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Chumacero EA, Yang J. Basin of Attraction and Limit Cycle Amplitude of an Ankle-Hip Model of Balance on a Balance Board. J Biomech Eng 2019; 141:2732255. [PMID: 31017633 DOI: 10.1115/1.4043563] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Indexed: 11/08/2022]
Abstract
The study of upright posture (UP) stability is of relevance to estimating risk of falls, especially among people with neuromuscular deficits. Several studies have addressed this problem from a system dynamic approach based on parameter bifurcation analyses, which provide the region of stability (RoS) and the delimiting bifurcation curves (usually Hopf and pitchfork) in some parameter-spaces. In contrast, our goal is to determine the effect of parameter changes on the size of the basin of attraction (BoA) of the UP equilibrium and the amplitude of the limit cycle oscillations (LCOs) emerging from the Hopf bifurcations (HBs). The BoA is an indicator of the ability of the UP to maintain balance without falling while LCOs may explain the sway motion commonly observed during balancing. In this study, a three degree of freedom model for a human balancing on a balance board was developed. Analysis of the model revealed the BoAs and the amplitude of the LCOs. Results show that physical parameters (time-delays and feedback control gains) have a large impact on the size of the BoA and the amplitude of the LCOs. Particularly, the size of the BoA increases when balancing on a rigid surface and decreases when either proprioceptive or combined visual and vestibular feedback gain is too high. With respect to the LCOs, it is shown that they emerge from both the subcritical and supercritical HBs and increase their amplitudes as some parameters vary.
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Affiliation(s)
- Erik A Chumacero
- Human-Centric Design Research Lab, Department of Mechanical Engineering, Texas Tech University, Lubbock, TX 79401
| | - James Yang
- ASME Fellow, Human-Centric Design Research Lab, Department of Mechanical Engineering, Texas Tech University, Lubbock, TX 79401
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Ivanenko Y, Gurfinkel VS. Human Postural Control. Front Neurosci 2018; 12:171. [PMID: 29615859 PMCID: PMC5869197 DOI: 10.3389/fnins.2018.00171] [Citation(s) in RCA: 205] [Impact Index Per Article: 34.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 03/05/2018] [Indexed: 12/21/2022] Open
Abstract
From ancient Greece to nowadays, research on posture control was guided and shaped by many concepts. Equilibrium control is often considered part of postural control. However, two different levels have become increasingly apparent in the postural control system, one level sets a distribution of tonic muscle activity (“posture”) and the other is assigned to compensate for internal or external perturbations (“equilibrium”). While the two levels are inherently interrelated, both neurophysiological and functional considerations point toward distinct neuromuscular underpinnings. Disturbances of muscle tone may in turn affect movement performance. The unique structure, specialization and properties of skeletal muscles should also be taken into account for understanding important peripheral contributors to postural regulation. Here, we will consider the neuromechanical basis of habitual posture and various concepts that were rather influential in many experimental studies and mathematical models of human posture control.
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Affiliation(s)
- Yury Ivanenko
- Laboratory of Neuromotor Physiology, IRCCS Fondazione Santa Lucia, Rome, Italy
| | - Victor S Gurfinkel
- Biomedical Engineering Department, Oregon Health and Science University, Portland, OR, United States
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Kammermeier S, Maierbeck K, Dietrich L, Plate A, Lorenzl S, Singh A, Bötzel K, Maurer C. Qualitative postural control differences in Idiopathic Parkinson's Disease vs. Progressive Supranuclear Palsy with dynamic-on-static platform tilt. Clin Neurophysiol 2018; 129:1137-1147. [PMID: 29631169 DOI: 10.1016/j.clinph.2018.03.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 03/05/2018] [Accepted: 03/08/2018] [Indexed: 10/17/2022]
Abstract
OBJECTIVES We aimed to assess whether postural abnormalities in Progressive Supranuclear Palsy (PSP) and Idiopathic Parkinson's Disease (IPD) are qualitatively different by analysing spontaneous and reactive postural control. METHODS We assessed postural control upon platform tilts in 17 PSP, 11 IPD patients and 18 healthy control subjects using a systems analysis approach. RESULTS Spontaneous sway abnormalities in PSP resembled those of IPD patients. Spontaneous sway was smaller, slower and contained lower frequencies in both PSP and IPD as compared to healthy subjects. The amount of angular body excursions as a function of platform angular excursions (GAIN) in PSP was qualitatively different from both IPD and healthy subjects (GAIN cut-off value: 2.9, sensitivity of 94%, specificity of 72%). This effect was pronounced at the upper body level and at low as well as high frequencies. In contrast, IPD patients' stimulus-related body excursions were smaller compared to healthy subjects. Using a systems analysis approach, we were able to allocate these different postural strategies to differences in the use of sensory information as well as to different error correction efforts. CONCLUSIONS While both PSP and IPD patients show abnormal postural control, the underlying pathology seems to be different. SIGNIFICANCE The identification of disease-specific postural abnormalities shown here may be helpful for diagnostic as well as therapeutic discriminations of PSP vs. IPD.
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Affiliation(s)
- Stefan Kammermeier
- Klinikum der Universität München, Ludwig-Maximilians-Universität LMU, Neurologische Klinik und Poliklinik, Marchioninistraße 15, 81377 München, Germany.
| | - Kathrin Maierbeck
- Klinikum der Universität München, Ludwig-Maximilians-Universität LMU, Neurologische Klinik und Poliklinik, Marchioninistraße 15, 81377 München, Germany; Klinikum der Universität München, Ludwig-Maximilians-Universität LMU, Klinik für Anästhesiologie, Marchioninistraße 15, 81377 München, Germany
| | - Lucia Dietrich
- Klinikum der Universität München, Ludwig-Maximilians-Universität LMU, Neurologische Klinik und Poliklinik, Marchioninistraße 15, 81377 München, Germany; Abteilung für Allgemeinchirurgie, Kliniken Ostallgäu-Kaufbeuren, Dr.-Gutermann-Straße 2, 87600 Kaufbeuren, Germany
| | - Annika Plate
- Klinikum der Universität München, Ludwig-Maximilians-Universität LMU, Neurologische Klinik und Poliklinik, Marchioninistraße 15, 81377 München, Germany
| | - Stefan Lorenzl
- Klinikum der Universität München, Ludwig-Maximilians-Universität LMU, Neurologische Klinik und Poliklinik, Marchioninistraße 15, 81377 München, Germany; Abteilung für Neurologie, Krankenhaus Agatharied, Norbert-Kerkel-Platz, 83734 Hausham, Germany
| | - Arun Singh
- Klinikum der Universität München, Ludwig-Maximilians-Universität LMU, Neurologische Klinik und Poliklinik, Marchioninistraße 15, 81377 München, Germany; Department of Neurology, University of Iowa, Iowa, IA, United States
| | - Kai Bötzel
- Klinikum der Universität München, Ludwig-Maximilians-Universität LMU, Neurologische Klinik und Poliklinik, Marchioninistraße 15, 81377 München, Germany
| | - Christoph Maurer
- Klinik für Neurologie und Neurophysiologie, Universitätsklinikum Freiburg, Breisacher Str. 64, 79106 Freiburg im Breisgau, Germany
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Lippi V, Mergner T. Human-Derived Disturbance Estimation and Compensation (DEC) Method Lends Itself to a Modular Sensorimotor Control in a Humanoid Robot. Front Neurorobot 2017; 11:49. [PMID: 28951719 PMCID: PMC5599790 DOI: 10.3389/fnbot.2017.00049] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 08/24/2017] [Indexed: 11/25/2022] Open
Abstract
The high complexity of the human posture and movement control system represents challenges for diagnosis, therapy, and rehabilitation of neurological patients. We envisage that engineering-inspired, model-based approaches will help to deal with the high complexity of the human posture control system. Since the methods of system identification and parameter estimation are limited to systems with only a few DoF, our laboratory proposes a heuristic approach that step-by-step increases complexity when creating a hypothetical human-derived control systems in humanoid robots. This system is then compared with the human control in the same test bed, a posture control laboratory. The human-derived control builds upon the identified disturbance estimation and compensation (DEC) mechanism, whose main principle is to support execution of commanded poses or movements by compensating for external or self-produced disturbances such as gravity effects. In previous robotic implementation, up to 3 interconnected DEC control modules were used in modular control architectures separately for the sagittal plane or the frontal body plane and successfully passed balancing and movement tests. In this study we hypothesized that conflict-free movement coordination between the robot's sagittal and frontal body planes emerges simply from the physical embodiment, not necessarily requiring a full body control. Experiments were performed in the 14 DoF robot Lucy Posturob (i) demonstrating that the mechanical coupling from the robot's body suffices to coordinate the controls in the two planes when the robot produces movements and balancing responses in the intermediate plane, (ii) providing quantitative characterization of the interaction dynamics between body planes including frequency response functions (FRFs), as they are used in human postural control analysis, and (iii) witnessing postural and control stability when all DoFs are challenged together with the emergence of inter-segmental coordination in squatting movements. These findings represent an important step toward controlling in the robot in future more complex sensorimotor functions such as walking.
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Affiliation(s)
- Vittorio Lippi
- Neurology, University Clinics of FreiburgFreiburg, Germany
| | - Thomas Mergner
- Neurology, University Clinics of FreiburgFreiburg, Germany
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Horak FB, Kluzik J, Hlavacka F. Velocity dependence of vestibular information for postural control on tilting surfaces. J Neurophysiol 2016; 116:1468-79. [PMID: 27486101 DOI: 10.1152/jn.00057.2016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 06/20/2016] [Indexed: 11/22/2022] Open
Abstract
Vestibular information is known to be important for postural stability on tilting surfaces, but the relative importance of vestibular information across a wide range of surface tilt velocities is less clear. We compared how tilt velocity influences postural orientation and stability in nine subjects with bilateral vestibular loss and nine age-matched, control subjects. Subjects stood on a force platform that tilted 6 deg, toes-up at eight velocities (0.25 to 32 deg/s), with and without vision. Results showed that visual information effectively compensated for lack of vestibular information at all tilt velocities. However, with eyes closed, subjects with vestibular loss were most unstable within a critical tilt velocity range of 2 to 8 deg/s. Subjects with vestibular deficiency lost their balance in more than 90% of trials during the 4 deg/s condition, but never fell during slower tilts (0.25-1 deg/s) and fell only very rarely during faster tilts (16-32 deg/s). At the critical velocity range in which falls occurred, the body center of mass stayed aligned with respect to the surface, onset of ankle dorsiflexion was delayed, and there was delayed or absent gastrocnemius inhibition, suggesting that subjects were attempting to actively align their upper bodies with respect to the moving surface instead of to gravity. Vestibular information may be critical for stability at velocities of 2 to 8 deg/s because postural sway above 2 deg/s may be too fast to elicit stabilizing responses through the graviceptive somatosensory system, and postural sway below 8 deg/s may be too slow for somatosensory-triggered responses or passive stabilization from trunk inertia.
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Affiliation(s)
- Fay B Horak
- Department of Neurology, Oregon Health & Science University, Portland, Oregon; VA Portland Health Care System, Portland, Oregon;
| | - JoAnn Kluzik
- Sargent College of Health and Rehabilitation Sciences, Boston University, Boston, Massachusetts; and
| | - Frantisek Hlavacka
- Institute of Normal and Pathological Physiology, Slovak Academy of Sciences, Bratislava, Slovak Republic
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Validation of the Inverted Pendulum Model in standing for transtibial prosthesis users. Clin Biomech (Bristol, Avon) 2016; 31:100-6. [PMID: 26472063 DOI: 10.1016/j.clinbiomech.2015.09.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 09/15/2015] [Accepted: 09/16/2015] [Indexed: 02/07/2023]
Abstract
BACKGROUND Often in balance assessment variables associated with the center of pressure are used to draw conclusions about an individual's balance. Validity of these conclusions rests upon assumptions that movement of the center of pressure is inter-dependent on movement of the center of mass. This dependency is mechanical and is referred to as the Inverted Pendulum Model. The following study aimed to validate this model both kinematically and kinetically, in transtibial prosthesis users and a control group. METHODS Prosthesis users (n=6) and matched control participants (n=6) stood quietly while force and motion data were collected under three conditions (eyes-open, eyes-closed, and weight-bearing feedback). Correlation coefficients were used to investigate the relationships between height and excursion of markers and center of masses in mediolateral/anteroposterior-directions, difference between center of pressure and center of mass and the center of mass acceleration in mediolateral/anteroposterior directions, magnitude of mediolateral/anteroposterior-component forces and center of mass acceleration, angular position of ankle and excursion in mediolateral/anteroposterior-directions, and integrated force signals. FINDINGS Results indicate kinematic validity of similar magnitudes (mean (SD) marker-displacement) between prosthesis users and control group for mediolateral- (r=0.77 (0.17); 0.74 (0.19)) and anteroposterior-directions (r=0.88 (0.18); 0.88 (0.19)). Correlation between difference of center of pressure and center of mass and the center of mass acceleration was negligible on the prosthetic side (r = 0.08 (0.06)) vs. control group (r=-0.51(0.13)). INTERPRETATION Results indicate kinematic validity of the Inverted Pendulum Model in transtibial prosthesis users but kinetic validity is questionable, particularly on the side with a prosthesis.
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Assländer L, Hettich G, Mergner T. Visual contribution to human standing balance during support surface tilts. Hum Mov Sci 2015; 41:147-64. [PMID: 25816794 PMCID: PMC4427279 DOI: 10.1016/j.humov.2015.02.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 01/31/2015] [Accepted: 02/23/2015] [Indexed: 11/03/2022]
Abstract
Contributions of visual position and velocity cues to standing balance are analyzed. Both visual cues reduce sway responses to support surface tilt and sway variability. Model simulations are used for data interpretation and data reproduction. Visual cues improve disturbance estimates by reduction of estimation thresholds. Reduction of noise by visual cues appears to be an instrumental factor.
Visual position and velocity cues improve human standing balance, reducing sway responses to external disturbances and sway variability. Previous work suggested that human balancing is based on sensory estimates of external disturbances and their compensation using feedback mechanisms (Disturbance Estimation and Compensation, DEC model). This study investigates the visual effects on sway responses to pseudo-random support surface tilts, assuming that improvements result from lowering the velocity threshold in a tilt estimate and the position threshold in an estimate of the gravity disturbance. Center of mass (COM) sway was measured with four different tilt amplitudes, separating the effect of visual cues across the conditions ‘Eyes closed’ (no visual cues), ‘4 Hz stroboscopic illumination’ (visual position cues), and ‘continuous illumination’ (visual position and velocity cues). In a model based approach, parameters of disturbance estimators were identified. The model reproduced experimental results and showed a specific reduction of the position and velocity threshold when adding visual position and velocity cues, respectively. Sway variability was analyzed to explore a hypothesized relation between estimator thresholds and internal noise. Results suggest that adding the visual cues reduces the contribution of vestibular noise, thereby reducing sway variability and allowing for lower thresholds, which improves the disturbance compensation.
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Affiliation(s)
- Lorenz Assländer
- Neurological University Clinic, Neurocenter, Breisacher Str. 64, 79106 Freiburg, Germany; Institute for Sport and Sportscience, University of Freiburg, Schwarzwaldstr. 175, 79117 Freiburg, Germany.
| | - Georg Hettich
- Neurological University Clinic, Neurocenter, Breisacher Str. 64, 79106 Freiburg, Germany; Institute for Sport and Sportscience, University of Freiburg, Schwarzwaldstr. 175, 79117 Freiburg, Germany
| | - Thomas Mergner
- Neurological University Clinic, Neurocenter, Breisacher Str. 64, 79106 Freiburg, Germany
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Honeine JL, Schieppati M. Time-interval for integration of stabilizing haptic and visual information in subjects balancing under static and dynamic conditions. Front Syst Neurosci 2014; 8:190. [PMID: 25339872 PMCID: PMC4186340 DOI: 10.3389/fnsys.2014.00190] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 09/17/2014] [Indexed: 01/22/2023] Open
Abstract
Maintaining equilibrium is basically a sensorimotor integration task. The central nervous system (CNS) continually and selectively weights and rapidly integrates sensory inputs from multiple sources, and coordinates multiple outputs. The weighting process is based on the availability and accuracy of afferent signals at a given instant, on the time-period required to process each input, and possibly on the plasticity of the relevant pathways. The likelihood that sensory inflow changes while balancing under static or dynamic conditions is high, because subjects can pass from a dark to a well-lit environment or from a tactile-guided stabilization to loss of haptic inflow. This review article presents recent data on the temporal events accompanying sensory transition, on which basic information is fragmentary. The processing time from sensory shift to reaching a new steady state includes the time to (a) subtract or integrate sensory inputs; (b) move from allocentric to egocentric reference or vice versa; and (c) adjust the calibration of motor activity in time and amplitude to the new sensory set. We present examples of processes of integration of posture-stabilizing information, and of the respective sensorimotor time-intervals while allowing or occluding vision or adding or subtracting tactile information. These intervals are short, in the order of 1–2 s for different postural conditions, modalities and deliberate or passive shift. They are just longer for haptic than visual shift, just shorter on withdrawal than on addition of stabilizing input, and on deliberate than unexpected mode. The delays are the shortest (for haptic shift) in blind subjects. Since automatic balance stabilization may be vulnerable to sensory-integration delays and to interference from concurrent cognitive tasks in patients with sensorimotor problems, insight into the processing time for balance control represents a critical step in the design of new balance- and locomotion training devices.
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Affiliation(s)
- Jean-Louis Honeine
- Department of Public Health, Experimental and Forensic Medicine, University of Pavia Pavia, Italy
| | - Marco Schieppati
- Department of Public Health, Experimental and Forensic Medicine, University of Pavia Pavia, Italy ; Centro Studi Attività Motorie (CSAM), Fondazione Salvatore Maugeri (IRCSS), Scientific Institute of Pavia Pavia, Italy
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Hettich G, Assländer L, Gollhofer A, Mergner T. Human hip–ankle coordination emerging from multisensory feedback control. Hum Mov Sci 2014; 37:123-46. [DOI: 10.1016/j.humov.2014.07.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2013] [Revised: 07/25/2014] [Accepted: 07/27/2014] [Indexed: 12/20/2022]
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15
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Keshner EA, Slaboda JC, Day LL, Darvish K. Visual conflict and cognitive load modify postural responses to vibrotactile noise. J Neuroeng Rehabil 2014; 11:6. [PMID: 24418107 PMCID: PMC3901028 DOI: 10.1186/1743-0003-11-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 12/16/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Underlying the increased incidence of falls during multitasking is a reduced ability to detect or attend to the sensory information signaling postural instability. Adding noise to a biological system has been shown to enhance the detection and transmission of weakened or sub-threshold cutaneous signals. If stochastic resonance is to become an effective adjunct to rehabilitation, we need to determine whether vibrotactile noise can be effective when added to an environment presenting with other sensory noise. METHODS Sub-threshold vibration noise was applied for 30 sec at the soles of the feet in 21 healthy adults (20-29 yrs) between two 30-sec periods of no vibration. During the trials, subjects stood quietly with eyes closed or while viewing a visual scene that rotated in continuous upward pitch at 30 deg/sec. Subjects were also tested with these two visual conditions while performing a mental calculation task. It was hypothesized that sub-threshold vibration would increase regularity of postural sway, thereby improving postural stabilization during an attention demanding task but exerting less effect with multiple sensory demands. An ellipse fit to the covariance matrix revealed excursion of center of pressure (COP) and center of mass (COM) responses in the anterior-posterior and lateral planes. RMS values and approximate entropy of the COP and COM were calculated and statistically compared. RESULTS The addition of vibrotactile noise to the plantar surface during quiet stance with eyes closed reduced the area of the COM and COP responses, which then returned to pre-vibration levels after vibration was removed. Postural sway was generally increased with both visual field rotations and mental calculation compared to the eyes closed condition. The effect of sub-threshold vibratory noise on postural behavior was modified when visual field rotations and mental calculation was combined. It was shown that the measure of approximate entropy reflected increased task complexity. CONCLUSIONS Our results suggest that the impact of destabilizing signals is modulated when combined with vibrotactile stimulation. The strong aftereffects of the vibration stimulus suggest that the system has adapted to the sensory array even in the short time period tested here. The results imply that application of vibrotactile stimulation has the potential for diminishing sway magnitudes while increasing the potential for response variability, thereby presenting a non-invasive method of reducing the potential for falls.
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Affiliation(s)
- Emily A Keshner
- Department of Physical Therapy, Temple University, 3307 N, Broad St,, 19140 Philadelphia, PA, USA.
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16
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The effect of vision elimination during quiet stance tasks with different feet positions. Gait Posture 2013; 38:708-11. [PMID: 23566634 DOI: 10.1016/j.gaitpost.2013.03.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Revised: 12/17/2012] [Accepted: 03/06/2013] [Indexed: 02/02/2023]
Abstract
Literature confirms the effects of vision and stance on body sway and indicates possible interactions between the two. However, no attempts have been made to systematically compare the effect of vision on the different types of stance which are frequently used in clinical and research practice. The biomechanical changes that occur after changing shape and size of the support surface suggest possible sensory re-weighting might take place. The purpose of this study was to assess the effect of vision on body sway in relation to different stance configurations and width. Thirty-eight volunteers performed four quiet stance configurations (parallel, semi-tandem, tandem and single leg), repeating them with open and closed eyes. Traditional parameters, recurrence quantification analysis and sample entropy were analyzed from the CoP trajectory signal. Traditional and recurrence quantification analysis parameters were affected by vision removal and stance type. Exceptions were frequency of oscillation, entropy and trapping time. The most prominent effect of vision elimination on traditional parameters was observed for narrower stances. A significant interaction effect between vision removal and stance type was present for most of the parameters observed (p<0.05). The interaction effect between medio-lateral and antero-posterior traditional parameters differed in linearity between stances. The results confirm the effect of vision removal on the body sway. However, for the medio-lateral traditional parameters, the effects did not increase linearly with the change in width and stance type. This suggests that removal of vision could be more effectively compensated by other sensory systems in semi-tandem stance, tandem and single legged stance.
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17
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Leg muscle activity during tandem stance and the control of body balance in the frontal plane. Clin Neurophysiol 2013; 124:1175-86. [DOI: 10.1016/j.clinph.2012.12.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Revised: 11/12/2012] [Accepted: 12/03/2012] [Indexed: 12/24/2022]
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18
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Abstract
Balancing on a tightrope or a slackline is an example of a neuromechanical task where the whole body both drives and responds to the dynamics of the external environment, often on multiple timescales. Motivated by a range of neurophysiological observations, here we formulate a minimal model for this system and use optimal control theory to design a strategy for maintaining an upright position. Our analysis of the open and closed-loop dynamics shows the existence of an optimal rope sag where balancing requires minimal effort, consistent with qualitative observations and suggestive of strategies for optimizing balancing performance while standing and walking. Our consideration of the effects of nonlinearities, potential parameter coupling and delays on the overall performance shows that although these factors change the results quantitatively, the existence of an optimal strategy persists.
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Affiliation(s)
- P Paoletti
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
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19
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Slaboda JC, Lauer RT, Keshner EA. Continuous visual field motion impacts the postural responses of older and younger women during and after support surface tilt. Exp Brain Res 2011; 211:87-96. [PMID: 21479659 DOI: 10.1007/s00221-011-2655-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Accepted: 03/23/2011] [Indexed: 10/18/2022]
Abstract
The effect of continuous visual flow on the ability to regain and maintain postural orientation was examined. Fourteen young (20-39 years old) and 14 older women (60-79 years old) stood quietly during 3° (30°/s) dorsiflexion tilt of the support surface combined with 30° and 45°/s upward or downward pitch rotations of the visual field. The support surface was held tilted for 30 s and then returned to neutral over a 30-s period while the visual field continued to rotate. Segmental displacement and bilateral tibialis anterior and gastrocnemius muscle EMG responses were recorded. Continuous wavelet transforms were calculated for each muscle EMG response. An instantaneous mean frequency curve (IMNF) of muscle activity, center of mass (COM), center of pressure (COP), and angular excursion at the hip and ankle were used in a functional principal component analysis (fPCA). Functional component weights were calculated and compared with mixed model repeated measures ANOVAs. The fPCA revealed greatest mathematical differences in COM and COP responses between groups or conditions during the period that the platform transitioned from the sustained tilt to a return to neutral position. Muscle EMG responses differed most in the period following support surface tilt indicating that muscle activity increased to support stabilization against the visual flow. Older women exhibited significantly larger COM and COP responses in the direction of visual field motion and less muscle modulation when the platform returned to neutral than younger women. Results on a Rod and Frame test indicated that older women were significantly more visually dependent than the younger women. We concluded that a stiffer body combined with heightened visual sensitivity in older women critically interferes with their ability to counteract posturally destabilizing environments.
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Affiliation(s)
- Jill C Slaboda
- Department of Physical Therapy, College of Health Professions and Social Work, Temple University, Philadelphia, PA 19140, USA.
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20
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Sensori-motor integration during stance: Time adaptation of control mechanisms on adding or removing vision. Hum Mov Sci 2011; 30:172-89. [DOI: 10.1016/j.humov.2010.06.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2009] [Revised: 06/24/2010] [Accepted: 06/26/2010] [Indexed: 11/19/2022]
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21
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Iqbal K. Mechanisms and models of postural stability and control. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2011; 2011:7837-7840. [PMID: 22256156 DOI: 10.1109/iembs.2011.6091931] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Though simple in appearance, postural stabilization is a complex neuromuscular task requiring coordination among multiple joints. Mechanisms of postural stability and control in the body include supraspinal processes responsible for anticipatory postural adjustments (APA) and internal model control, lower level motor servo, and passive viscoelasticity of the musculo-tendon complex (MTC). Nevertheless, active control mechanisms may have limited effectiveness due to intrinsic delays in the reflex pathways and muscle low-pass characteristics. The use of control-oriented mathematical models, aided by analytical methods, help provide insight into neuro-physiology. Control of balance in human upright standing is particularly well suited for modeling, and is also a popular experimental paradigm. This paper examines neuro-physiological basis of postural stability and control in the background of popular biomechanic and neuroscientific models.
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Affiliation(s)
- Kamran Iqbal
- University of Arkansas at Little Rock, 2801 S University Ave Little Rock, AR 72204, USA.
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22
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Earhart GM, Henckens JM, Carlson-Kuhta P, Horak FB. Influence of vision on adaptive postural responses following standing on an incline. Exp Brain Res 2010; 203:221-6. [PMID: 20336282 DOI: 10.1007/s00221-010-2208-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2009] [Accepted: 02/25/2010] [Indexed: 12/01/2022]
Abstract
Previous studies demonstrated a leaning after-effect (LAE) following standing or walking on an inclined surface consistent with a long-lasting, somatosensory memory for body orientation relative to the surface. Here, we asked whether providing a brief visual reference during LAE resets postural orientation to the new visual reference. The results showed that subjects immediately return to upright when eyes were opened briefly during the post-incline period. However, the subjects also immediately resumed leaning after closing their eyes again following 20 s of eyes open. The duration of LAE was not influenced by 1 or 2 brief periods of vision. Also, the amplitude of the lean following the brief vision period was often larger than when subjects had their eyes closed for the entire post-incline period. These results suggest a powerful somatosensory memory contribution to postural orientation in space that is not eliminated or recalibrated with brief exposure to a visual reference.
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Affiliation(s)
- Gammon M Earhart
- Program in Physical Therapy, Washington University in St. Louis, St. Louis, MO, USA
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23
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Cenciarini M, Loughlin PJ, Sparto PJ, Redfern MS. Stiffness and damping in postural control increase with age. IEEE Trans Biomed Eng 2009; 57:267-75. [PMID: 19770083 DOI: 10.1109/tbme.2009.2031874] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Upright balance is believed to be maintained through active and passive mechanisms, both of which have been shown to be impacted by aging. A compensatory balance response often observed in older adults is increased co-contraction, which is generally assumed to enhance stability by increasing joint stiffness. We investigated the effect of aging on standing balance by fitting body sway data to a previously developed postural control model that includes active and passive stiffness and damping parameters. Ten young (24 +/- 3 years) and seven older (75 +/- 5 years) adults were exposed during eyes-closed stance to perturbations consisting of lateral pseudorandom floor tilts. A least-square fit of the measured body sway data to the postural control model found significantly larger active stiffness and damping model parameters in the older adults. These differences remained significant even after normalizing to account for different body sizes between the young and older adult groups. An age effect was also found for the normalized passive stiffness, but not for the normalized passive damping parameter. This concurrent increase in active stiffness and damping was shown to be more stabilizing than an increase in stiffness alone, as assessed by oscillations in the postural control model impulse response.
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Affiliation(s)
- Massimo Cenciarini
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15261, USA.
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24
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Kim S, Horak FB, Carlson-Kuhta P, Park S. Postural feedback scaling deficits in Parkinson's disease. J Neurophysiol 2009; 102:2910-20. [PMID: 19741108 DOI: 10.1152/jn.00206.2009] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Many differences in postural responses have been associated with age and Parkinson's disease (PD), but until now there has been no quantitative model to explain these differences. We developed a feedback control model of body dynamics that could reproduce the postural responses of young subjects, elderly subjects, and subjects with PD, and we investigated whether the postural impairments of subjects with PD can be described as an abnormal scaling of postural feedback gain. Feedback gains quantify how the nervous system generates compensatory joint torques based on kinematic responses. Seven subjects in each group experienced forward postural perturbations to seven different backward support surface translations ranging from 3- to 15-cm amplitudes and with a constant duration of 275 ms. Ground reaction forces and joint kinematics were measured to obtain joint torques from inverse dynamics. A full-state feedback controller with a two-segment body dynamic model was used to simulate joint kinematics and kinetics in response to perturbations. Results showed that all three subject groups gradually scaled postural feedback gains as a function of perturbation amplitudes, and the scaling started even before the maximum allowable ankle torque was reached. This result implies that the nervous system takes body dynamics into account and adjusts postural feedback gains to accommodate biomechanical constraints. PD subjects showed significantly smaller than normal ankle feedback gain with low scaling and larger hip feedback gain, which led to an early violation of the flat-foot constraint and unusually small (bradykinetic) postural responses. Our postural feedback control model quantitatively described the postural abnormality of the patients with PD as abnormal feedback gains and reduced ability to modify postural feedback gain with changes in postural challenge.
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Affiliation(s)
- Seyoung Kim
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 335 Gwahak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea.
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25
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Mergner T, Schweigart G, Fennell L, Maurer C. Posture control in vestibular-loss patients. Ann N Y Acad Sci 2009; 1164:206-15. [PMID: 19645901 DOI: 10.1111/j.1749-6632.2008.03722.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Patients with chronic bilateral loss of vestibular functions normally replace these by visual or haptic referencing to stationary surroundings, resulting in an almost normal stance control. But with eyes closed, they show abnormally large body sway, and may tend to fall when there are external disturbances to the body or when standing on an unstable support surface. Patients' postural responses depend on joint angle proprioception and ground reaction-force cues (occasionally referred to as "somatosensory graviception"). It is asked why the force cues do not allow patients to fully substitute loss of the vestibular cues. In recent years, four sets of observations of experimental situations where patients, eyes closed, show impaired stance control or even may fall were identified: (1) with unstable or compliant support ("inevitable falls"); (2) with large external disturbances such as support surface tilts or pull stimuli impacting on their bodies (leading to abnormally large body movements); (3) with fast body-support tilts (also abnormally large body movements); and (4) with transient support tilt (overshooting body-support stabilization and abnormaly late body-space [BS] stabilization). When patients' data were modeled, it was found that their problems stem mainly from the force cues. It was hypothesized that patients have difficulties decomposing this sensory information into its constituents in order to be able to get rid of an active force component. Normals do not have this difficulty, because the vestibular system performs the decomposition.
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Affiliation(s)
- Thomas Mergner
- Department of Neurology, University Clinics, University of Freiburg, Freiburg, Germany.
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26
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Abstract
This article presents a biologically-inspired framework for humanoid postural control. It complies with the main features of human postural control that are extracted from recent studies. In this article, the human body is abstracted as a single-inverted pendulum jointed with a foot that rests freely on a supporting surface. In particular, disturbances affecting posture are addressed and accommodated within the proposed framework. Among these are external forces and motion of support surface on which the body stands. The main components of this framework are: 1. A state-feedback mechanism for stabilizing the unstable dynamics of the body. 2. A tracking loop for robustly achieving desired voluntary orientations. 3. A feed-forward control primarily for improving the response to voluntary motions. 4. A stand-alone vestibular sensory fusion algorithm for estimating body orientation. 5. An external-disturbance estimator and a corresponding compensation for minimizing the effect of external disturbances. These components are interconnected in a way that qualifies this framework to modularly address the multi-segment body postural control problem. Although no postural stability measure is explicitly incorporated, experiments run on a special-purpose humanoid demonstrate the stability and the performance merits of the presented framework.
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Affiliation(s)
- Karim A Tahboub
- Neurological University Clinic, Neurocenter, University of Freiburg, Breisacherstr. 64, 79106 Freiburg, Germany
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27
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Abstract
There is considerable recent interest in developing humanoid robots. An important substrate for many motor actions in both humans and biped robots is the ability to maintain a statically or dynamically stable posture. Given the success of the human design, one would expect there are lessons to be learned in formulating a postural control mechanism for robots. In this study we limit ourselves to considering the problem of maintaining upright stance. Human stance control is compared to a suggested method for robot stance control called zero moment point (ZMP) compensation. Results from experimental and modeling studies suggest there are two important subsystems that account for the low- and mid-frequency (DC to approximately 1Hz) dynamic characteristics of human stance control. These subsystems are (1) a "sensory integration" mechanism whereby orientation information from multiple sensory systems encoding body kinematics (i.e. position, velocity) is flexibly combined to provide an overall estimate of body orientation while allowing adjustments (sensory re-weighting) that compensate for changing environmental conditions and (2) an "effort control" mechanism that uses kinetic-related (i.e., force-related) sensory information to reduce the mean deviation of body orientation from upright. Functionally, ZMP compensation is directly analogous to how humans appear to use kinetic feedback to modify the main sensory integration feedback loop controlling body orientation. However, a flexible sensory integration mechanism is missing from robot control leaving the robot vulnerable to instability in conditions where humans are able to maintain stance. We suggest the addition of a simple form of sensory integration to improve robot stance control. We also investigate how the biological constraint of feedback time delay influences the human stance control design. The human system may serve as a guide for improved robot control, but should not be directly copied because the constraints on robot and human control are different.
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Affiliation(s)
- Robert J Peterka
- Biomedical Engineering Division, Oregon Health & Science University, OHSU West Campus, 505 NW 185th Avenue, Beaverton, OR 97006, USA.
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28
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Abstract
Many of our motor activities require stabilization against external disturbances. This especially applies to biped stance since it is inherently unstable. Disturbance compensation is mainly reactive, depending on sensory inputs and real-time sensor fusion. In humans, the vestibular system plays a major role. When there is no visual space reference, vestibular-loss clearly impairs stance stability. Most humanoid robots do not use a vestibular system, but stabilize upright body posture by means of center of pressure (COP) control. We here suggest using in addition a vestibular sensor and present a biologically inspired vestibular sensor along with a human-inspired stance control mechanism. We proceed in two steps. First, in an introductory review part, we report on relevant human sensors and their role in stance control, focusing on own models of transmitter fusion in the vestibular sensor and sensor fusion in stance control. In a second, experimental part, the models are used to construct an artificial vestibular system and to embed it into the stance control of a humanoid. The robot's performance is investigated using tilts of the support surface. The results are compared to those of humans. Functional significance of the vestibular sensor is highlighted by comparing vestibular-able with vestibular-loss states in robot and humans. We show that a kinematic body-space sensory feedback (vestibular) is advantageous over a kinetic one (force cues) for dynamic body-space balancing. Our embodiment of human sensorimotor control principles into a robot is more than just bionics. It inspired our biological work (neurorobotics: 'learning by building', proof of principle, and more). We envisage a future clinical use in the form of hardware-in-the-loop simulations of neurological symptoms for improving diagnosis and therapy and designing medical assistive devices.
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Affiliation(s)
- Thomas Mergner
- Neurologie der Universität Freiburg, Neurozentrum, Breisacher Strasse 64, Freiburg, Germany.
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29
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Horlings C, Küng U, Honegger F, Van Engelen B, Van Alfen N, Bloem B, Allum J. Vestibular and proprioceptive influences on trunk movements during quiet standing. Neuroscience 2009; 161:904-14. [DOI: 10.1016/j.neuroscience.2009.04.005] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Revised: 03/25/2009] [Accepted: 04/04/2009] [Indexed: 11/26/2022]
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30
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Reflex pathways connect receptors in the human lower leg to the erector spinae muscles of the lower back. Exp Brain Res 2009; 196:217-27. [PMID: 19484229 DOI: 10.1007/s00221-009-1849-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2008] [Accepted: 05/01/2009] [Indexed: 10/20/2022]
Abstract
Reflex pathways connect all four limbs in humans. Presently, we tested the hypothesis that reflexes also link sensory receptors in the lower leg with muscles of the lower back (erector spinae; ES). Taps were applied to the right Achilles' tendon and electromyographic activity was recorded from the right soleus and bilaterally from ES. Reflexes were compared between sitting and standing and between standing with the eyes open versus closed. Reflexes were evoked bilaterally in ES and consisted of an early latency excitation, a medium latency inhibition, and a longer latency excitation. During sitting but not standing, the early excitation was larger in the ES muscle ipsilateral to the stimulation (iES) than in the contralateral ES (cES). During standing but not sitting, the longer latency excitation in cES was larger than in iES. This response in cES was also larger during standing compared to sitting. Responses were not significantly different between the eyes open and eyes closed conditions. Taps applied to the lateral calcaneus (heel taps) evoked responses in ES that were not significantly different in amplitude or latency than those evoked by tendon taps, despite a 75-94% reduction in the amplitude of the soleus stretch reflex evoked by the heel taps. Electrical stimulation of the sural nerve, a purely cutaneous nerve at the ankle, evoked ES reflexes that were not significantly different in amplitude but had significantly longer latencies than those evoked by the tendon and heel taps. These results support the hypothesis that reflex pathways connect receptors in the lower leg with muscles of the lower back and show that that the amplitude of these reflexes is modulated by task. Responses evoked by stimulation of the sural nerve establish that reflex pathways connect the ES muscles with cutaneous receptors of the foot. In contrast, the large volley in muscle spindle afferents induced by the tendon taps compared to the heel taps did not alter the ES responses, suggesting that the reflex connection between triceps surae muscle spindles and the ES muscles may be relatively weak. These heteronymous reflexes may play a role in stabilizing the trunk for maintaining posture and balance.
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Johansson R, Fransson PA, Magnusson M. Optimal coordination and control of posture and movements. ACTA ACUST UNITED AC 2009; 103:159-77. [DOI: 10.1016/j.jphysparis.2009.08.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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32
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Cnyrim C, Mergner T, Maurer C. Potential roles of force cues in human stance control. Exp Brain Res 2009; 194:419-33. [PMID: 19219426 DOI: 10.1007/s00221-009-1715-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2008] [Accepted: 01/14/2009] [Indexed: 10/21/2022]
Abstract
Human stance is inherently unstable. A small deviation from upright body orientation is enough to yield a gravitational component in the ankle joint torque, which tends to accelerate the body further away from upright ('gravitational torque'; magnitude is related to body-space lean angle). Therefore, to maintain a given body lean position, a corresponding compensatory torque must be generated. It is well known that subjects use kinematic sensory information on body-space lean from the vestibular system for this purpose. Less is known about kinetic cues from force/torque receptors. Previous work indicated that they are involved in compensating external contact forces such as a pull or push having impact on the body. In this study, we hypothesized that they play, in addition, a role when the vestibular estimate of the gravitational torque becomes erroneous. Reasons may be sudden changes in body mass, for instance by a load, or an impairment of the vestibular system. To test this hypothesis, we mimicked load effects on the gravitational torque in normal subjects and in patients with chronic bilateral vestibular loss (VL) with eyes closed. We added/subtracted extra torque to the gravitational torque by applying an external contact force (via cable winches and a body harness). The extra torque was referenced to body-space lean, using different proportionality factors. We investigated how it affected body-space lean responses that we evoked using sinusoidal tilts of the support surface (motion platform) with different amplitudes and frequencies (normals +/-1 degrees, +/-2 degrees, and +/-4 degrees at 0.05, 0.1, 0.2, and 0.4 Hz; patients +/-1 degrees and +/-2 degrees at 0.05 and 0.1 Hz). We found that added/subtracted extra torque scales the lean response in a systematic way, leading to increase/decrease in lean excursion. Expressing the responses in terms of gain and phase curves, we compared the experimental findings to predictions obtained from a recently published sensory feedback model. For the trials in which the extra torque tended to endanger stance control, predictions in normals were better when the model included force cues than without these cues. This supports our notion that force cues provide an automatic 'gravitational load compensation' upon changes in body mass in normals. The findings in the patients support our notion that the presumed force cue mechanism provides furthermore vestibular loss compensation. Patients showed a body-space stabilization that cannot be explained by ankle angle proprioception, but must involve graviception, most likely by force cues. Our findings suggest that force cues contribute considerably to the redundancy and robustness of the human stance control system.
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Affiliation(s)
- Christian Cnyrim
- Neurological University Clinics, Neurozentrum, Breisacher Str. 64, 79106, Freiburg, Germany
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