169,753 research outputs found
A Computational Framework Towards the Tele-Rehabilitation of Balance Control Skills
No full textMobility has been one of the most impacted aspects of human life due to the spread of the COVID-19 pandemic. Home confinement, the lack of access to physical rehabilitation, and prolonged immobilization of COVID-19-positive patients within hospitals are three major factors that affected the mobility of the general population world-wide. Balance is one key indicator to monitor the possible movement disorders that may arise both during the COVID-19 pandemic and in the coming future post-COVID-19. A systematic quantification of the balance performance in the general population is essential for preventing the appearance and progression of certain diseases (e.g., cardiovascular, neurodegenerative, and musculoskeletal), as well as for assessing the therapeutic outcomes of prescribed physical exercises for elderly and pathological patients. Current research on clinical exercises and associated outcome measures of balance is still far from reaching a consensus on a “golden standard” practice. Moreover, patients are often reluctant or unable to follow prescribed exercises, because of overcrowded facilities, lack of reliable and safe transportation, or stay-at-home orders due to the current pandemic. A novel balance assessment methodology, in combination with a home-care technology, can overcome these limitations. This paper presents a computational framework for the in-home quantitative assessment of balance control skills. Novel outcome measures of balance performance are implemented in the design of rehabilitation exercises with customized and quantifiable training goals. Using this framework in conjunction with a portable technology, physicians can treat and diagnose patients remotely, with reduced time and costs and a highly customized approach. The methodology proposed in this research can support the development of innovative technologies for smart and connected home-care solutions for physical therapy rehabilitation
How dynamic is dynamic walking? Human vs. robotic gait
No full textFor design and control of biped walking robots, it is important to quantify the different level of dynamicity. We propose the Dynamic Gait Measure (DGM) that quantifies the dynamicity of a given biped walking motion. The DGM is associated with the gait stability, and quantifies the effects of inertia in terms of the Zero-Moment Point (ZMP) and the ground projection of center of mass (GCOM). Also, DGM takes into account the stance foot dimension and the relative threshold between static and dynamic walking. Human-like and robotic walking motions are generated for a planar biped system from an optimization problem. The resulting DGMs demonstrate their dependence on the stance foot dimension as well as the walking motion. The DGM results verify the dynamic nature of normal human walking. For a given gait motion, smaller foot dimension results in increased dynamicity. Moreover, the DGMs for normal human walking are greater than those for robotic walking. The proposed results will benefit the development of walking robots. Copyright © 2011 by ASME
Passive and dynamic gait measures for biped mechanism: Formulation and simulation analysis
No full textUnderstanding and mimicking human gait is essential for design and control of biped walking robots. The unique characteristics of normal human gait are described as passive dynamic walking, whereas general human gait is neither completely passive nor always dynamic. To study various walking motions, it is important to quantify the different levels of passivity and dynamicity, which have not been addressed in the current literature. In this paper, we introduce the initial formulations of Passive Gait Measure (PGM) and Dynamic Gait Measure (DGM) that quantify passivity and dynamicity, respectively, of a given biped walking motion, and the proposed formulations will be demonstrated for proof-of-concepts using gait simulation and analysis. The PGM is associated with the optimality of natural human walking, where the passivity weight functions are proposed and incorporated in the minimization of physiologically inspired weighted actuator torques. The PGM then measures the relative contribution of the stance ankle actuation. The DGM is associated with the gait stability, and quantifies the effects of inertia in terms of the Zero-Moment Point and the ground projection of center of mass. In addition, the DGM takes into account the stance foot dimension and the relative threshold between static and dynamic walking. As examples, both human-like and robotic walking motions during single support phase are generated for a planar biped system using the passivity weights and proper gait parameters. The calculated PGM values show more passive nature of human-like walking as compared with the robotic walking. The DGM results verify the dynamic nature of normal human walking with anthropomorphic foot dimension. In general, the DGMs for human-like walking are greater than those for robotic walking. The resulting DGMs also demonstrate their dependence on the stance foot dimension as well as the walking motion; for a given walking motion, smaller foot dimension results in increased dynamicity. Future work on experimental validation and demonstration will involve actual walking robots and human subjects. The proposed results will benefit the human gait studies and the development of walking robots. © 2012 Cambridge University Press
Sensitivity of balancing in legged systems under torque constraint variations
No full textThe balancing capabilities of a legged system can be influenced by several properties of the system itself, for instance, the strength of joint motors in a robot or muscle strength in living systems. In this work, the changes in the balancing capabilities of a legged system are evaluated as the joint actuator torque limits of the system change. The legged system is modeled with an inverted pendulum model with an actuated ankle and a finite foot size. The effect of variations of the ankle torque limits on the system balance stability is quantified through the local properties of Lagrange multipliers in optimization theory and are validated through numerical experiments. With the proposed method, the information on the balance stability boundary of a legged system is used to predict the balance stability characteristics of the system with altered joint torque limits, hence providing quantifiable guidelines to the design of such systems
Contact-Dependent Balance Stability of Walking Robots
No full textA novel theoretical framework for the identification of the balance stability regions of biped systems is implemented on a real robotic platform. With the proposed method, the balance stability capabilities of a biped robot are quantified by a balance stability region in the state space of center of mass (COM) position and velocity. The boundary of such a stability region provides a threshold between balanced and falling states for the robot by including all possible COM states that are balanced with respect to a specified feet/ground contact configuration. A COM state outside of the stability region boundary is the sufficient condition for a falling state, from which a change in the specified contact configuration is inevitable. By specifying various positions of the robot’s feet on the ground, the effects of different contact configurations on the robot’s balance stability capabilities are investigated. Experimental walking trajectories of the robot are analyzed in relationship with their respective stability boundaries, to study the robot balance control during various gait phases.</jats:p
Balanced and falling states for biped systems: Applications to robotic versus human walking stability
No full textContact-dependent balance stability of biped robots
No full textA theoretical-algorithmic framework for the construction of balance stability boundaries of biped robots with multiple contacts with the environment is proposed and implemented on a robotic platform. Comprehensive and univocal definitions of the states of balance of a generic legged system are introduced with respect to the system's contact configuration. Theoretical models of joint-space and center of mass (COM)-space dynamics under multiple contacts, distribution of contact wrenches, and robotic system parameters are established for their integration into a nonlinear programing (NLP) problem. In the proposed approach, the balance stability capabilities of a biped robot are quantified by a partition of the state space of COM position and velocity. The boundary of such a partition provides a threshold between balanced and falling states of the biped robot with respect to a specified contact configuration. For a COM state to be outside of the stability boundary represents the sufficient condition for falling, from which a change in the system's contact is inevitable. Through the calculated stability boundaries, the effects of different contact configurations (single support (SS) and double support (DS) with different step lengths) on the robot's balance stability capabilities can be quantitatively evaluated. In addition, the balance characteristics of the experimental walking trajectories of the robot at various speeds are analyzed in relation to their respective stability boundaries. The proposed framework provides a contact-dependent balance stability criterion for a given system, which can be used to improve the design and control of walking robots
An agent-specific stochastic model of generalized reaching task difficulty
No full textThe ability of an agent to accomplish a trajectory during a certain motor task depends on the fit between external (environment) and internal (agent) constraints, also known as affordance. A model of difficulty for a generalized reaching motor task is proposed as an affordance-related measure, as perceived by a specific agent for a given environment and task. By extending the information-based Index of Difficulty of a trajectory, a stochastic model of difficulty is formulated based on the observed variability of spatial trajectories executed by a given agent during a repetitive motor task. The model is tested on an experimental walking dataset available in the literature, where the repetitive stride movement of differently aged subjects (14 “old” subjects aged 50-73; 20 “young” subjects aged 21-37) at multiple speed conditions (comfortable, ~30% faster, ~30% slower) is analyzed. Reduced trajectory variability in older as compared to younger adults results in a higher Index of Difficulty (slower: +24%, p < 0.0125; faster: +38%, p < 0.002) which is interpreted in this context as reduced affordance. The model overcomes the limits of existing difficulty measures by capturing the stochastic dependency of task difficulty on a subject’s age and average speed. This model provides a benchmarking tool for motor performance in biomechanics and ergonomics applications
Laser in periodontal pockets: in vivo and in vitro study
No full textThe aim of this study was to verify the sterilizing effectiveness of the laser in the treatment of the periodontal pockets in vivo, with the recording of clinicians' parameters and microbiological analysis, and in vitro with particular attention to the presence of specific bacterial stocks. During our study, in particular, it has been used the diodes laser. In order to estimate the effectiveness of the treatment of the periodontal pockets with laser, it has been examined the microbial content of the pockets carrying out withdrawals of the sulcular material before, immediately after and twenty minutes from the radiation. The microbiological results of the studies assert that, although substantial qualitative discrepancies between the several colonies of pathogen do not exist, quantitative differences are taken place with respect to the lessening of number and dimension of the present colonie
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