Gait Analysis
Fatemeh Akbarifar; Mohammad Hadi Honarvar; Mostafa Haj Lotfalian
Volume 15, Issue 1 , May 2021, , Pages 1-11
Abstract
Finding the center of rotation (COR) is needed for defining the anatomical axis of the skeletal system and for the kinematic calculation of joints in biomechanical studies. For this purpose, predictive and functional methods can be used. In the predictive methods, regression equations obtained from anthropometric ...
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Finding the center of rotation (COR) is needed for defining the anatomical axis of the skeletal system and for the kinematic calculation of joints in biomechanical studies. For this purpose, predictive and functional methods can be used. In the predictive methods, regression equations obtained from anthropometric measurements are used, and in the functional methods, the relative motion of the two adjacent segments is used to find COR. The purpose of this study is to formulate the circle fitting algorithm as a functional method with two analytical and optimization solutions. In order to evaluate the algorithm, error analysis was performed by both analytical and numerical methods. Also, effective factors in error estimating of COR position such as standard deviation of measurement system error (σ), rotation angle (α) and the distance between marker and COR (r), was evaluated. The results showed a high correlation (r=0.99) between analytical and numerical solution, which proved the accuracy of the error analysis. In this study, optimization method according to the accuracy of better estimates in low quantities α, less influence on high quantities σ and high speed in problem solving, can be taken into consideration to reconstruct human movements in biomechanical studies. Use of functional methods, eliminates the need for attaching markers to anatomical landmarks and provides a new development in motion data acquisition.
Fatemeh Ghafouri; Mohammad Hadi Honarvar; Mohammad Mahdi Jalili
Volume 14, Issue 1 , May 2020, , Pages 1-11
Abstract
Minimizing the energy expenditure as well as structure's size and weight is very important in biped walking robots. To achieve this target, a passive controller, which is a combination of spring and linear damper, is added to a biped walker. The important specification of the studied walker is that it ...
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Minimizing the energy expenditure as well as structure's size and weight is very important in biped walking robots. To achieve this target, a passive controller, which is a combination of spring and linear damper, is added to a biped walker. The important specification of the studied walker is that it has two convex soles at the end of the legs as feet, which is jointed to body with a passive revolute joint. Contact point moves on a sole curve. To reduce system's dynamic complexity, pointed mass approach is used. The main purpose of this research is studying the dynamical behavior of this underactuated walker before and after adding controller. In the first step, a model based on developed pointed mass model is offered and analyzed by adding two rigid convex soles as feet and passive revolute joint as ankle. To make leg length changes during walking, an active dynamic element is used. Next, a passive controller or dynamic element is used with the active one to reduce active element role during movement. Particle swarm optimization method is used to minimize this role by calculating optimized passive element parameters. The results show using the combination of optimized passive and active dynamic elements, the amount of energy consumption is decreased significantly. As a result, we can use a much smaller active element with less power to walk. Also using a passive dynamic element practically improves mechanical specifications of the structure such as dimensions and weight as well as providing simple use for users.
Mahdie Termeh; Afshin Ghanbarzadeh; Mohammad Hadi Honarvar; Kourosh Heidari Shirazi
Volume 13, Issue 4 , December 2019, , Pages 361-372
Abstract
A primary objective in many human upright state movements is control of balance and monitoring, analysis, and intervention to improve it, has become a part of human biomechanics research. In studies with a quantitative approach to human balance, it is necessary to know the numerical quantity of balance ...
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A primary objective in many human upright state movements is control of balance and monitoring, analysis, and intervention to improve it, has become a part of human biomechanics research. In studies with a quantitative approach to human balance, it is necessary to know the numerical quantity of balance in a body state or at any moment during a path. This study proposes a new quantitative Criterion to express stable state during walking cycle. The basis of this quantitative criterion is the Probability of dynamic success in completing the swing phase without losing balance and the initiation of a fall. The probability of motion realization has been calculated and simulated on a seven-link model with a distributed mass. In this study by taking into consideration the kinematic constraints, energy consumption, muscle stimulation level and changes in stimulation beside maximizing balance, the movement in stance phase is calculated as an optimal movement. The optimal step length has been calculated considering a weight for probability of motion realization and energy consumption. In this method both the maximum balance and minimum energy consumption have been considered. For instance, the optimal step length considering the maximum balance constraint in the specific path for an individual with the height of 187 cm and mass of 92 kg was calculated about 27 cm with this probabilistic approach. One of the factors in maintaining balance is cadence rate. By increasing the center of mass average velocity, the probability of balance maintenance decreases, thus also with considering center of mass average velocity beside maximum balance constraint, the optimal step length is calculated 46 cm.
