A phase-reduced neuro-mechanical model for insect locomotion: feed-forward stability and proprioceptive feedback

2010 ◽  
Vol 368 (1930) ◽  
pp. 5087-5104 ◽  
Author(s):  
J. Proctor ◽  
R. P. Kukillaya ◽  
P. Holmes
Keyword(s):  
Degrees Of Freedom ◽  
Muscle Activation ◽  
Phase Oscillators ◽  
Joint Torques ◽  
Insect Locomotion ◽  
Phase Reduction ◽  
Activation Dynamics ◽  
Order Of Magnitude ◽  
Sensory Pathway ◽  
Muscle Models

In earlier work, we have developed an integrated model for insect locomotion that includes a central pattern generator (CPG), nonlinear muscles, hexapedal geometry and a representative proprioceptive sensory pathway. Here, we employ phase reduction and averaging theory to replace 264 ordinary differential equations (ODEs), describing bursting neurons in the CPG, their synaptic connections to motoneurons, muscle activation dynamics and sensory neurons, with 24 one-dimensional phase oscillators that describe motoneuronal activation of agonist–antagonist muscle pairs driving the jointed legs. Reflexive feedback is represented by stereotypical spike trains with rates proportional to joint torques, which change phase relationships among the motoneuronal oscillators. Restriction to the horizontal plane, neglect of leg mass and use of Hill-type muscle models yield a biomechanical body–limb system with only three degrees of freedom, and the resulting hybrid dynamical system involves 30 ODEs: reduction by an order of magnitude. We show that this reduced model captures the dynamics of unperturbed gaits and the effects of an impulsive perturbation as accurately as the original one. Moreover, the phase response and coupling functions provide an improved understanding of reflexive feedback mechanisms.

Estimation of Metabolical Costs for Human Locomotion

2005 ◽  
Author(s):  
Werner Schiehlen ◽  
Marko Ackermann
Keyword(s):  
Degrees Of Freedom ◽  
Inverse Dynamics ◽  
Sagittal Plane ◽  
Human Locomotion ◽  
Human Gait ◽  
Joint Torques ◽  
Gait Quality ◽  
Analysis Laboratory ◽  
Muscle Models

Metabolical energy is the chemical energy consumed by skeletal muscles to generate force. This quantity is useful to understand the comfort of human gait and to evaluate, in terms of effort required, the performance of devices or therapies designed to improve gait quality of persons presenting gait disorders. Firstly, this paper presents the frequently used estimations of energy expenditure based lonely on joint torques and mechanical costs obtained by inverse dynamics of passive and active walking devices. Secondly, a more advanced approach is discussed consisting of modeling the musculoskeletal system with Hill-type phenomenological muscle models and computing the metabolical expenditure adopting expressions recently proposed in the literature. As an example a musculoskeletal model of the lower limb in the sagittal plane consisting of thigh, shank and foot with three degrees of freedom and actuated by eight muscles is considered. This model is used to estimate metabolical costs for known normal gait kinematical data obtained in a gait analysis laboratory.

Multibody Dynamics Integrated With Muscle Models and Space-Time Constraints for Optimization of Lifting Movements

2005 ◽  
Author(s):  
Cunjun Huang ◽  
Pradip N. Sheth ◽  
Kevin P. Granata
Keyword(s):  
Multibody Dynamics ◽  
Dynamic Optimization ◽  
Muscle Activation ◽  
Optimization Problems ◽  
Optimization Technique ◽  
Activation Parameters ◽  
Space Time ◽  
Time Constraints ◽  
Joint Torques ◽  
Muscle Models

A multibody dynamics model integrated with space-time constraints based optimization is presented in this paper for generating optimal trajectories of human lifting movements. “Space-time constraints” is a two-point boundary value dynamic optimization technique developed for animation of computer graphics characters and has a significant potential for biomechanics and other mechanical movement based dynamic optimization problems. Optimization results demonstrate the ability to consider different preferences for minimizing the loading of specific joints such as an ankle, or a knee, or a shoulder during the lifting motion and the resulting lifting trajectories are shown to be different. Lumped muscle models to generate the joint torques are incorporated at five joints to model the actuation effects of the muscular system during the dynamic movement. The dynamic optimization is then based on the muscle activation parameters instead of the traditionally used joint torques. The muscle activation model optimization is shown to correlate better with the actual motion tests conducted by the VICON video capture and test data analysis system.

Using Hill-Type Muscle Models and EMG Data in a Forward Dynamic Analysis of Joint Moment

2003 ◽  
Vol 03 (02) ◽  
pp. 169-186 ◽  
Author(s):  
Richard Heine ◽  
Kurt Manal ◽  
Thomas S. Buchanan
Keyword(s):  
Muscle Activation ◽  
Joint Moment ◽  
Model Parameters ◽  
Time Varying ◽  
Muscle Forces ◽  
Joint Moments ◽  
Delay Term ◽  
Activation Dynamics ◽  
Moment Models ◽  
Muscle Models

There has been considerable interest in estimating muscle forces and joint moments from EMG signals, but most approaches have not been very successful. This is largely because robust models of muscle activation dynamics, Hill-type muscle contraction dynamics, and musculoskeletal geometry are generally not included. Here we present a model which includes these sub-models and we determine which model parameters are most important. The models abilities to predict joint moments about the human elbow during time-varying isometric tasks were examined. Inputs to the models were EMGs from eight muscles. Joint moment was the output, which was compared with the measured moment. Models varied in complexity, having up to 59 adjustable parameters. It was found that a seven adjustable parameter model could adequately estimate time-varying joint moments without substantial sacrifice in performance. The key parameters that were fit for each subject were two global gain factors, a time delay term, a non-linear EMG-force term, two muscle activation terms, and a term for skewing the length-tension curve with muscle activation. This approach offers advantages over optimization-based methods for estimating individual muscle forces. Most importantly, it accounts for the way muscles are activated, which makes it potentially powerful to evaluate patients with pathologies.

Complete Solution Sets for Neuromuscular Models Reveal How Mechanical Constraints Limit Neural Control Options

2010 ◽  
Author(s):  
Jason J. Kutch ◽  
Francisco J. Valero-Cuevas
Keyword(s):  
Degrees Of Freedom ◽  
Neural Control ◽  
Muscle Activation ◽  
Complete Solution ◽  
The Body ◽  
Joint Torques ◽  
Mechanical Constraints ◽  
Geometric Methods ◽  
Muscle Activations ◽  
Fingertip Forces

One of the main goals of neuromuscular modeling is to establish the range of feasible muscle activations for a given mechanical output of the body. This is not a trivial problem because there are typically infinitely many combinations of muscle activations that will generate the same joint torques, as most joints are actuated by more muscles than rotational degrees of freedom. Here we show that well-established geometric methods easily provide a complete description of the set of muscle activations that generate a desired set of joint torques or endpoint forces. In contrast to iterative linear programming optimizations, geometric methods provide a set of solutions in muscle activation space simply by converting between the geometric representations of neural and mechanical constraints. As an example, we use geometric methods to find the feasible set of activations that produce fingertip forces in a set of directions. These results show that for a given set of fingertip forces, the range of feasible activation for each muscle can differ with the choice of mechanical constraints. Thus, the mechanical constraints of the task play an important role governing the options the nervous system has when controlling redundant muscles.

scholarly journals Optimization of Joint Torques of Robot Using Dynamic Redundant Degrees of Freedom.

1992 ◽  
Vol 10 (5) ◽  
pp. 682-688
Author(s):  
Tamio ARAI ◽  
Shih-Hsuan CHIU ◽  
Akira SAIKI ◽  
Hisashi OSUMI
Keyword(s):  
Degrees Of Freedom ◽  
Joint Torques

scholarly journals Lower Extremity Motor Impairments in Ambulatory Chronic Hemiparetic Stroke: Evidence for Lower Extremity Weakness and Abnormal Muscle and Joint Torque Coupling Patterns

2017 ◽  
Vol 31 (9) ◽  
pp. 814-826 ◽  
Author(s):  
Natalia Sánchez ◽  
Ana Maria Acosta ◽  
Roberto Lopez-Rosado ◽  
Arno H. A. Stienen ◽  
Julius P. A. Dewald
Keyword(s):  
Lower Extremity ◽  
Degrees Of Freedom ◽  
Joint Torque ◽  
Motor Impairments ◽  
Lower Extremity Weakness ◽  
Joint Torques ◽  
Hemiparetic Stroke ◽  
Chronic Hemiparetic Stroke ◽  
Hip Extension ◽  
Flexion And Extension

Although global movement abnormalities in the lower extremity poststroke have been studied, the expression of specific motor impairments such as weakness and abnormal muscle and joint torque coupling patterns have received less attention. We characterized changes in strength, muscle coactivation and associated joint torque couples in the paretic and nonparetic extremity of 15 participants with chronic poststroke hemiparesis (age 59.6 ± 15.2 years) compared with 8 age-matched controls. Participants performed isometric maximum torques in hip abduction, adduction, flexion and extension, knee flexion and extension, ankle dorsi- and plantarflexion and submaximal torques in hip extension and ankle plantarflexion. Surface electromyograms (EMGs) of 10 lower extremity muscles were measured. Relative weakness (paretic extremity compared with the nonparetic extremity) was measured in poststroke participants. Differences in EMGs and joint torques associated with maximum voluntary torques were tested using linear mixed effects models. Results indicate significant poststroke torque weakness in all degrees of freedom except hip extension and adduction, adductor coactivation during extensor tasks, in addition to synergistic muscle coactivation patterns. This was more pronounced in the paretic extremity compared with the nonparetic extremity and with controls. Results also indicated significant interjoint torque couples during maximum and submaximal hip extension in both extremities of poststroke participants and in controls only during maximal hip extension. Additionally, significant interjoint torque couples were identified only in the paretic extremity during ankle plantarflexion. A better understanding of these motor impairments is expected to lead to more effective interventions for poststroke gait and posture.

A 3D Complexity-Adaptive Approach to Exploit Sparsity in Elastic Wave Propagation

Geophysics ◽  
2021 ◽  
pp. 1-64
Author(s):  
Claudia Haindl ◽  
Kuangdai Leng ◽  
Tarje Nissen-Meyer
Keyword(s):  
Degrees Of Freedom ◽  
Computational Cost ◽  
Parameter Tuning ◽  
Performance Limits ◽  
Absorbing Boundary ◽  
Adaptive Approach ◽  
Order Of Magnitude ◽  
Speed Up ◽  
Complex Settings ◽  
Close Fit

We present an adaptive approach to seismic modeling by which the computational cost of a 3D simulation can be reduced while retaining resolution and accuracy. This Azimuthal Complexity Adaptation (ACA) approach relies upon the inherent smoothness of wavefields around the azimuth of a source-centered cylindrical coordinate system. Azimuthal oversampling is thereby detected and eliminated. The ACA method has recently been introduced as part of AxiSEM3D, an open-source solver for global seismology. We employ a generalization of this solver which can handle local-scale Cartesian models, and which features a combination of an absorbing boundary condition and a sponge boundary with automated parameter tuning. The ACA method is benchmarked against an established 3D method using a model featuring bathymetry and a salt body. We obtain a close fit where the models are implemented equally in both solvers and an expectedly poor fit otherwise, with the ACA method running an order of magnitude faster than the classic 3D method. Further, we present maps of maximum azimuthal wavenumbers that are created to facilitate azimuthal complexity adaptation. We show how these maps can be interpreted in terms of the 3D complexity of the wavefield and in terms of seismic resolution. The expected performance limits of the ACA method for complex 3D structures are tested on the SEG/EAGE salt model. In this case, ACA still reduces the overall degrees of freedom by 92% compared to a complexity-blind AxiSEM3D simulation. In comparison with the reference 3D method, we again find a close fit and a speed-up of a factor 7. We explore how the performance of ACA is affected by model smoothness by subjecting the SEG/EAGE salt model to Gaussian smoothing. This results in a doubling of the speed-up. ACA thus represents a convergent, versatile and efficient method for a variety of complex settings and scales.

Do Arm Postures Vary With the Speed of Reaching?

1999 ◽  
Vol 81 (5) ◽  
pp. 2582-2586 ◽  
Author(s):  
Kiisa C. Nishikawa ◽  
Sara T. Murray ◽  
Martha Flanders
Keyword(s):  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Optimal Solution ◽  
Reaching Movements ◽  
Total Force ◽  
Joint Torques ◽  
Dynamic Factors ◽  
Human Arm ◽  
Wide Range ◽  
Dynamic Forces

Do arm postures vary with the speed of reaching? For reaching movements in one plane, the hand has been observed to follow a similar path regardless of speed. Recent work on the control of more complex reaching movements raises the question of whether a similar “speed invariance” also holds for the additional degrees of freedom. Therefore we examined human arm movements involving initial and final hand locations distributed throughout the three-dimensional (3D) workspace of the arm. Despite this added complexity, arm kinematics (summarized by the spatial orientation of the “plane of the arm” and the 3D curvature of the hand path) changed very little for movements performed over a wide range of speeds. If the total force (dynamic + quasistatic) had been optimized by the control system (e.g., as in a minimization of the change in joint torques or the change in muscular forces), the optimal solution would change with speed; slow movements would reflect the minimal antigravity torques, whereas fast movements would be more strongly influenced by dynamic factors. The speed-invariant postures observed in this study are instead consistent with a hypothesized optimization of only the dynamic forces.

scholarly journals Impedance Model-Based Optimal Regulation on Force and Position of Bimanual Robots to Hold an Object

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Darong Huang ◽  
Hong Zhan ◽  
Chenguang Yang
Keyword(s):  
Degrees Of Freedom ◽  
Target Position ◽  
Internal Force ◽  
Robot System ◽  
Joint Torques ◽  
Impedance Model ◽  
Generalized Momentum ◽  
Optimal Target ◽  
End Effectors ◽  
Bimanual Robot

Bimanual robots have been studied for decades and regulation on internal force of the being held object by two manipulators becomes a research interest in recent years. In this paper, based on impedance model, a method to obtain the optimal target position for bimanual robots to hold an object is proposed. We introduce a cost function combining the errors of the force and the position and manage to minimize its value to gain the optimal coordinates for the robot end effectors (EE). To implement this method, two necessary algorithms are presented, which are the closed-loop inverse kinematics (CLIK) method to work out joint positions from desired EE pose and the generalized-momentum-based external force observer to measure the subjected force acting on the EE so as to properly compensate for the joint torques. To verify the effectiveness, practicality, and adaptivity of the proposed scheme, in the simulation, a bimanual robot system with three degrees of freedom (DOF) in every manipulator was constructed and employed to hold an object, where the results are satisfactory.

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