An Analytical Examination of Muscle Force Estimations Using Optimization Techniques

1993 ◽  
Vol 207 (3) ◽  
pp. 139-148 ◽  
Author(s):  
J H Challis ◽  
D G Kerwin
Keyword(s):  
Objective Function ◽  
Muscle Force ◽  
Human Movement ◽  
Optimization Techniques ◽  
Muscle Model ◽  
Muscle Forces ◽  
Objective Functions ◽  
Physiological Properties ◽  
Maximal Activation

Muscle forces are often estimated during human movement using optimization procedures. The optimization procedures involve the minimization of an objective function relating to the muscle forces. In this study 15 different objective functions were evaluated by examining the analytical solutions to the objective functions and by comparing their force predictions with the forces estimated using a validated muscle model. The muscle forces estimated by the objective functions were shown to give poor correspondence with the muscle model predicted muscle forces. The objective function estimates were criticized for not taking sufficient account of the physiological properties of the muscles. As a consequence of the analysis of the objective functions an alternative, simpler function was presented with which to estimate muscle forces in vivo. This function required that to satisfy a given joint moment, the force exerted by each of the muscles divided by the maximum force possible by the muscle was constant for all muscles. For this function the maximum muscle force was determined using a muscle model assuming maximal activation.

scholarly journals Comparative Study of Popular Objective Functions for Damping Power System Oscillations in Multimachine System

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Naz Niamul Islam ◽  
M. A. Hannan ◽  
Hussain Shareef ◽  
Azah Mohamed ◽  
M. A. Salam
Keyword(s):  
Power System ◽  
Objective Function ◽  
Search Algorithm ◽  
Optimization Techniques ◽  
Stable Region ◽  
Objective Functions ◽  
Linearized Model ◽  
Oscillation Damping ◽  
Power System Oscillations ◽  
Damping Controller

Power oscillation damping controller is designed in linearized model with heuristic optimization techniques. Selection of the objective function is very crucial for damping controller design by optimization algorithms. In this research, comparative analysis has been carried out to evaluate the effectiveness of popular objective functions used in power system oscillation damping. Two-stage lead-lag damping controller by means of power system stabilizers is optimized using differential search algorithm for different objective functions. Linearized model simulations are performed to compare the dominant mode’s performance and then the nonlinear model is continued to evaluate the damping performance over power system oscillations. All the simulations are conducted in two-area four-machine power system to bring a detailed analysis. Investigated results proved that multiobjective D-shaped function is an effective objective function in terms of moving unstable and lightly damped electromechanical modes into stable region. Thus, D-shape function ultimately improves overall system damping and concurrently enhances power system reliability.

Appropriate Objective Functions for Quantifying Iris Mechanical Properties Using Inverse Finite Element Modeling

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Anup D. Pant ◽  
Syril K. Dorairaj ◽  
Rouzbeh Amini
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Objective Function ◽  
Inverse Modeling ◽  
Measurement Errors ◽  
Ex Vivo ◽  
Treatment Strategies ◽  
Objective Functions ◽  
Estimation Of Parameters

Quantifying the mechanical properties of the iris is important, as it provides insight into the pathophysiology of glaucoma. Recent ex vivo studies have shown that the mechanical properties of the iris are different in glaucomatous eyes as compared to normal ones. Notwithstanding the importance of the ex vivo studies, such measurements are severely limited for diagnosis and preclude development of treatment strategies. With the advent of detailed imaging modalities, it is possible to determine the in vivo mechanical properties using inverse finite element (FE) modeling. An inverse modeling approach requires an appropriate objective function for reliable estimation of parameters. In the case of the iris, numerous measurements such as iris chord length (CL) and iris concavity (CV) are made routinely in clinical practice. In this study, we have evaluated five different objective functions chosen based on the iris biometrics (in the presence and absence of clinical measurement errors) to determine the appropriate criterion for inverse modeling. Our results showed that in the absence of experimental measurement error, a combination of iris CL and CV can be used as the objective function. However, with the addition of measurement errors, the objective functions that employ a large number of local displacement values provide more reliable outcomes.

Efficiency of grey wolf optimization algorithm for damage detection of skeletal structures via expanded mode shapes

2020 ◽  
Vol 23 (13) ◽  
pp. 2850-2865 ◽  
Author(s):  
Parsa Ghannadi ◽  
Seyed Sina Kourehli ◽  
Mohammad Noori ◽  
Wael A Altabey
Keyword(s):  
Objective Function ◽  
Damage Identification ◽  
Optimization Techniques ◽  
Mode Shapes ◽  
Grey Wolf ◽  
Objective Functions ◽  
Expansion Process ◽  
Grey Wolf Optimization ◽  
Skeletal Structures ◽  
Equivalent Reduction

Vibration-based structural damage identification through optimization techniques has become an interesting research topic in recent years. Dynamic characteristics such as frequencies and mode shapes are used to construct the objective function. The objective functions based on only frequencies are not very sensitive to damage in large structures. However, objective functions based on both mode shapes and frequencies are very effective. In real measurement condition, the number of installed sensors is limited, and there are no economic reasons for measuring the mode shapes at all degrees of freedom. In this kind of circumstances, mode expansion methods are used to address the incompleteness of mode shapes. In this article, the system equivalent reduction and expansion process is applied to determine the unmeasured mode shapes. Two experimental examples including a cantilever beam and a truss tower are investigated to show system equivalent reduction and expansion process’ efficiency in estimating unmeasured mode shapes. The results show that the technique used for expansion is influential. Damage identification is formulated as an optimization problem, and the residual force vector based on expanded mode shapes is considered as an objective function. In order to minimize the objective function, grey wolf optimization and Harris hawks optimization are used. Numerical studies on a 56-bar dome space truss and experimental validation on a steel frame are performed to demonstrate the efficiency of the developed approach. Both numerical and experimental results indicate that the combination of the grey wolf optimization and expanded mode shapes with system equivalent reduction and expansion process can provide a reliable approach for determining the severities and locations of damage of skeletal structures when it compares with those obtained by Harris hawks optimization.

Determining Muscle Forces in the Leg During Normal Human Walking—An Application and Evaluation of Optimization Methods

1978 ◽  
Vol 100 (2) ◽  
pp. 72-78 ◽  
Author(s):  
D. E. Hardt
Keyword(s):  
Linear Programming ◽  
Muscle Force ◽  
Tensile Force ◽  
Optimization Techniques ◽  
Joint Torque ◽  
Human Walking ◽  
Programming Algorithm ◽  
Optimization Approach ◽  
Muscle Forces ◽  
Optimal Criterion

The individual muscle forces in the leg during human walking are unknown, because of a greater number of muscles when compared to degrees of freedom at the joints. The muscle force-joint torque equations can be solved, however, using optimization techniques. A linear programming solution of these equations applied at discrete, time-independent steps in the walking cycle using dynamic joint torque data is presented. The use of this technique, although capable of providing unique solutions, gives questionable muscle force histories when compared to electromyographic data. The reasons for the lack of confidence in the solution are found in the inherent limitations imposed by the linear programming algorithm and in the simplistic treatment of the muscles as tensile force sources rather than complex mechanochemical transducers. The definition of a physiologically rationalized optimal criterion requires both a global optimization approach and more complete modelling of the system.

ESTIMATION OF MUSCLE FORCE DERIVED FROM IN VIVO MR ELASTOGRAPHY TESTS: A PRELIMINARY STUDY

2013 ◽  
Vol 16 (03) ◽  
pp. 1350015 ◽  
Author(s):  
Sabine F. Bensamoun ◽  
Tien Tuan Dao ◽  
Fabrice Charleux ◽  
Marie-Christine Ho Ba Tho
Keyword(s):  
Magnetic Resonance ◽  
Muscle Force ◽  
Swing Phase ◽  
Human Motion ◽  
Magnetic Resonance Elastography ◽  
Muscle Disease ◽  
Muscle Forces ◽  
Rheological Models ◽  
Tensile Forces

The objective is to estimate the vastus medialis (VM) muscle force from multifrequency magnetic resonance elastography (MMRE) tests and two different rheological models (Voigt and springpot). Healthy participants (N = 13) underwent multifrequency (70, 90 and 110 Hz) magnetic resonance elastography MMRE tests. Thus, in vivo experimental elastic (μ) properties of the VM in passive and active (20% MVC) conditions were characterized. Moreover, the muscle viscosity (η) was determined with Voigt and springpot rheological models, in both muscle states. Subsequently, the VM muscle forces were calculated with a generic musculoskeletal model (OpenSIM) where the active and passive shear moduli (μ) were implemented. The viscosity measured with the two rheological models increased when the muscle is contracted. During the stance and the swing phases, the VM tensile forces decrease and the VM force was lower with the springpot model. It can be noted that during the swing phase, the muscle forces estimated from springpot model showed a higher standard deviation compared to the Voigt model. This last result may indicate a strong sensitivity of the muscle force to the change of active and passive contractile components in the swing phase of gait. This study provides for the first time an estimation of the muscle tensile forces for lower limb, during human motion, from in vivo experimental muscle mechanical properties. The assessment of individualized muscle forces during motion is valuable for finite element models, increasing the patient specific parameters. This novel muscle database will be of use for the clinician to better elucidate the muscle pathophysiology and to better monitor the effects of the muscle disease.

An Objective Function for Optimization Techniques in Simultaneous Multiple-Element Analysis by Inductively Coupled Plasma Spectrometry

1982 ◽  
Vol 36 (1) ◽  
pp. 37-40 ◽  
Author(s):  
J. J. Leary ◽  
A. E. Brookes ◽  
A. F. Dorrzapf ◽  
D. W. Golightly
Keyword(s):  
Objective Function ◽  
Inductively Coupled Plasma ◽  
Optimization Technique ◽  
Optimization Techniques ◽  
Operating Conditions ◽  
Objective Functions ◽  
Element Analysis ◽  
Plasma Spectrometry ◽  
Inductively Coupled ◽  
Inductively Coupled Plasma Spectrometry

This work considers several composite objective functions and uses the sequential simplex optimization technique to evaluate the performance of a proposed objective function in locating optimal instrumental operating conditions for simultaneous multiple-element determinations by inductively coupled plasma spectrometry. The proposed objective function, combined with a generalized approach to optimization, can be applied to any group of analysis elements and is of value in routine optimization procedures for simultaneous multiple-element methods of analysis.

Direct Validation of Model-Predicted Muscle Forces in the Cat Hindlimb During Locomotion

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Derya Karabulut ◽  
Suzan Cansel Dogru ◽  
Yi-Chung Lin ◽  
Marcus G. Pandy ◽  
Walter Herzog ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Muscle Force ◽  
Medial Gastrocnemius ◽  
Electromyographic Activity ◽  
Muscle Forces ◽  
Static Optimization ◽  
Individual Muscle ◽  
Length Changes ◽  
Musculoskeletal Systems

Abstract Various methods are available for simulating the movement patterns of musculoskeletal systems and determining individual muscle forces, but the results obtained from these methods have not been rigorously validated against experiment. The aim of this study was to compare model predictions of muscle force derived for a cat hindlimb during locomotion against direct measurements of muscle force obtained in vivo. The cat hindlimb was represented as a 5-segment, 13-degrees-of-freedom (DOF), articulated linkage actuated by 25 Hill-type muscle-tendon units (MTUs). Individual muscle forces were determined by combining gait data with two widely used computational methods—static optimization and computed muscle control (CMC)—available in opensim, an open-source musculoskeletal modeling and simulation environment. The forces developed by the soleus, medial gastrocnemius (MG), and tibialis anterior muscles during free locomotion were measured using buckle transducers attached to the tendons. Muscle electromyographic activity and MTU length changes were also measured and compared against the corresponding data predicted by the model. Model-predicted muscle forces, activation levels, and MTU length changes were consistent with the corresponding quantities obtained from experiment. The calculated values of muscle force obtained from static optimization agreed more closely with experiment than those derived from CMC.

Feasibility of Highly Constrained Muscle Force Predictions for the Knee During Gait

2011 ◽  
Author(s):  
Jonathan P. Walter ◽  
Darryl D. D’Lima ◽  
Thor F. Besier ◽  
Benjamin J. Fregly
Keyword(s):  
Cerebral Palsy ◽  
Muscle Force ◽  
Human Muscle ◽  
Accurate Assessment ◽  
Muscle Forces

Accurate assessment of human muscle forces during walking could significantly aid in the analysis and treatment of common neuromusculoskeletal disorders such as osteoarthritis [1], stroke, and cerebral palsy. However, the inability to measure muscle forces in vivo along with the inability to calculate muscle forces directly has greatly hindered achievement of this goal. Due to its complexity, the knee is a particularly difficult joint for assessing in vivo muscle forces.

Use of Optimization Techniques to Predict Muscle Forces

1978 ◽  
Vol 100 (2) ◽  
pp. 88-92 ◽  
Author(s):  
R. D. Crowninshield
Keyword(s):  
Muscle Strength ◽  
Muscle Force ◽  
Optimization Techniques ◽  
Emg Activity ◽  
Muscle Action ◽  
Muscle Forces ◽  
Distribution Problem ◽  
Joint Function ◽  
Individual Muscle ◽  
Synergistic Muscle

Optimization solutions to the indeterminate distribution problem of determining muscle forces are discussed. A method of predicting muscle force during joint function is presented which encourages the prediction of synergistic muscle action with physiologically reasonable individual muscle forces. The method uses limits on muscle strength that are a set portion of the lowest muscle strength that will permit a solution at the particular joint moment. The method is shown to correlate well with recorded EMG activity.

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