scholarly journals Jumping in frogs: assessing the design of the skeletal system by anatomically realistic modeling and forward dynamic simulation

2002 ◽  
Vol 205 (12) ◽  
pp. 1683-1702 ◽  
Author(s):  
William J. Kargo ◽  
Frank Nelson ◽  
Lawrence C. Rome
Keyword(s):  
Degrees Of Freedom ◽  
The Body ◽  
Joint Torque ◽  
Rotational Degree ◽  
Skeletal System ◽  
Dynamic Simulations ◽  
Inverse Dynamic ◽  
Maximal Distance ◽  
Out Of Plane ◽  
Rotational Degrees Of Freedom

SUMMARY Comparative musculoskeletal modeling represents a tool to understand better how motor system parameters are fine-tuned for specific behaviors. Frog jumping is a behavior in which the physical properties of the body and musculotendon actuators may have evolved specifically to extend the limits of performance. Little is known about how the joints of the frog contribute to and limit jumping performance. To address these issues, we developed a skeletal model of the frog Rana pipiens that contained realistic bones, joints and body-segment properties. We performed forward dynamic simulations of jumping to determine the minimal number of joint degrees of freedom required to produce maximal-distance jumps and to produce jumps of varied take-off angles. The forward dynamics of the models was driven with joint torque patterns determined from inverse dynamic analysis of jumping in experimental frogs. When the joints were constrained to rotate in the extension—flexion plane, the simulations produced short jumps with a fixed angle of take-off. We found that, to produce maximal-distance jumping,the skeletal system of the frog must minimally include a gimbal joint at the hip (three rotational degrees of freedom), a universal Hooke's joint at the knee (two rotational degrees of freedom) and pin joints at the ankle,tarsometatarsal, metatarsophalangeal and iliosacral joints (one rotational degree of freedom). One of the knee degrees of freedom represented a unique kinematic mechanism (internal rotation about the long axis of the tibiofibula)and played a crucial role in bringing the feet under the body so that maximal jump distances could be attained. Finally, the out-of-plane degrees of freedom were found to be essential to enable the frog to alter the angle of take-off and thereby permit flexible neuromotor control. The results of this study form a foundation upon which additional model subsystems (e.g. musculotendon and neural) can be added to test the integrative action of the neuromusculoskeletal system during frog jumping.

Dynamic Modeling of a High-Dynamic Flight Simulator

2014 ◽  
Vol 687-691 ◽  
pp. 610-615 ◽  
Author(s):  
Hui Liu ◽  
Li Wen Guan
Keyword(s):  
Dynamic Modeling ◽  
Degrees Of Freedom ◽  
Flight Simulator ◽  
Inverse Dynamic ◽  
Dynamic Formulation ◽  
Time Histories ◽  
Rotational Degrees Of Freedom ◽  
High Dynamic ◽  
Euler Approach ◽  
Simulation Results

High-dynamic flight simulator (HDFS), using a centrifuge as its motion base, is a machine utilized for simulating the acceleration environment associated with modern advanced tactical aircrafts. This paper models the HDFS as a robotic system with three rotational degrees of freedom. The forward and inverse dynamic formulations are carried out by the recursive Newton-Euler approach. The driving torques acting on the joints are determined on the basis of the inverse dynamic formulation. The formulation has been implemented in two numerical simulation examples, which are used for calculating the maximum torques of actuators and simulating the time-histories of kinematic and dynamic parameters of pure trapezoid Gz-load command profiles, respectively. The simulation results can be applied to the design of the control system. The dynamic modeling approach presented in this paper can also be generalized to some similar devices.

Design Human-Robot Collaborative Lifting Task Using Optimization

2021 ◽  
Author(s):  
Asif Arefeen ◽  
Yujiang Xiang
Keyword(s):  
Degrees Of Freedom ◽  
Joint Angle ◽  
Joint Torque ◽  
Robotic Arm ◽  
Inverse Dynamic ◽  
Floating Base ◽  
Grasping Forces ◽  
Design Variables ◽  
Human Arm ◽  
Lifting Task

Abstract In this paper, an optimization-based dynamic modeling method is used for human-robot lifting motion prediction. The three-dimensional (3D) human arm model has 13 degrees of freedom (DOFs) and the 3D robotic arm (Sawyer robotic arm) has 10 DOFs. The human arm and robotic arm are built in Denavit-Hartenberg (DH) representation. In addition, the 3D box is modeled as a floating-base rigid body with 6 global DOFs. The interactions between human arm and box, and robot and box are modeled as a set of grasping forces which are treated as unknowns (design variables) in the optimization formulation. The inverse dynamic optimization is used to simulate the lifting motion where the summation of joint torque squares of human arm is minimized subjected to physical and task constraints. The design variables are control points of cubic B-splines of joint angle profiles of the human arm, robotic arm, and box, and the box grasping forces at each time point. A numerical example is simulated for huma-robot lifting with a 10 Kg box. The human and robotic arms’ joint angle, joint torque, and grasping force profiles are reported. These optimal outputs can be used as references to control the human-robot collaborative lifting task.

Muscle Synergies Modify Optimization Estimates of Joint Stiffness During Walking

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Mohammad S. Shourijeh ◽  
Benjamin J. Fregly
Keyword(s):  
Degrees Of Freedom ◽  
Computational Models ◽  
Joint Stiffness ◽  
The Body ◽  
Grand Challenge ◽  
Lower Body ◽  
Inverse Dynamic ◽  
Co Activation ◽  
Muscle Activations ◽  
The Cost

Abstract Because of its simplicity, static optimization (SO) is frequently used to resolve the muscle redundancy problem (i.e., more muscles than degrees-of-freedom (DOF) in the human musculoskeletal system). However, SO minimizes antagonistic co-activation and likely joint stiffness as well, which may not be physiologically realistic since the body modulates joint stiffness during movements such as walking. Knowledge of joint stiffness is limited due to the difficulty of measuring it experimentally, leading researchers to estimate it using computational models. This study explores how imposing a synergy structure on the muscle activations estimated by optimization (termed “synergy optimization,” or SynO) affects calculated lower body joint stiffnesses during walking. By limiting the achievable muscle activations and coupling all time frames together, a synergy structure provides a potential mechanism for reducing indeterminacy and improving physiological co-activation but at the cost of a larger optimization problem. To compare joint stiffnesses produced by SynO (2–6 synergies) and SO, we used both approaches to estimate lower body muscle activations and forces for sample experimental overground walking data obtained from the first knee grand challenge competition. Both optimizations used a custom Hill-type muscle model that permitted analytic calculation of individual muscle contributions to the stiffness of spanned joints. Both approaches reproduced inverse dynamic joint moments well over the entire gait cycle, though SynO with only two synergies exhibited the largest errors. Maximum and mean joint stiffnesses for hip and knee flexion in particular decreased as the number of synergies increased from 2 to 6, with SO producing the lowest joint stiffness values. Our results suggest that SynO increases joint stiffness by increasing muscle co-activation, and furthermore, that walking with a reduced number of synergies may result in increased joint stiffness and perhaps stability.

Semiactive Control of Multiple Degree of Freedom Systems

1997 ◽  
Author(s):  
Mehdi Ahmadian
Keyword(s):  
Degrees Of Freedom ◽  
Hybrid Control ◽  
Control Policy ◽  
The Body ◽  
Semiactive Control ◽  
Dynamic Simulations ◽  
Passive Dampers ◽  
Suspension Model ◽  
The Cost ◽  
Resonance Control

Abstract Semiactive control of systems with multiple degrees of freedom is addressed. Two systems representing a pitch-plane model of a vehicle and a single suspension are used to illustrate the results. The dynamic simulations show the well-known compromise between resonance control and isolation, due to passive dampers. It is shown that semiactive dampers also compromise between controlling different bodies. For skyhook and groundhook control policies, the control of one body is achieved at the cost of less control on the other bodies. For instance, in a single suspension model, skyhook semiactive dampers better control the body resonance, but significantly increase the axle resonance (wheelhop). The groundhook dampers provide a better control of wheelhop at the expense of increasing body resonance. A hybrid control policy that combines the effect of skyhook and groundhook policies is introduced. This policy can be used to provide the proper control on all bodies, while using the hardware common to existing semiactive dampers.

scholarly journals Effect of Molecular Rotational Degrees of Freedom on Mechanical and Thermodynamic Properties of Solid Methane at Temperatures above 50 K

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Antonina V. Leont’eva ◽  
Andrew Yu. Prokhorov ◽  
Anatoly Yu. Zakharov ◽  
Alexander I. Erenburg
Keyword(s):  
Temperature Interval ◽  
Spectral Properties ◽  
Degrees Of Freedom ◽  
Reliable Data ◽  
The Body ◽  
Data Set ◽  
Rotational Degrees Of Freedom ◽  
Triple Point Temperature ◽  
Equilibrium Vapor Pressure ◽  
Solid Methane

The paper presents an analysis of extensive data set of mechanical, structural, thermophysical, and spectral properties of solid methane in the temperature interval 0.5 · Ttr–Ttr (Ttr is the triple point temperature) under equilibrium vapor pressure. It is shown that the anomalies of the studied properties (or lack of reliable data) at temperatures 60–70 K have been observed in the body of the reviewed papers. We proposed that the observed anomalies are due to a transition between classical and quantum regimes of collective rotational degrees of freedom of methane molecules in this temperature interval.

Inverse Kinematics and Dynamics of a 3-DOF Spatial Parallel Manipulator

2012 ◽  
Vol 229-231 ◽  
pp. 2280-2284
Author(s):  
Jian Xin Yang ◽  
Ben Zhao ◽  
Chun Li Li
Keyword(s):  
Inverse Kinematics ◽  
Parallel Manipulator ◽  
Control Algorithm ◽  
Degrees Of Freedom ◽  
Rotational Degree ◽  
Kinematics Analysis ◽  
Inverse Dynamic ◽  
Generalized Coordinates ◽  
Euler Approach ◽  
Position And Orientation

Recently the parallel manipulator with less DOFs has attracted industry and academia, but the research on its dynamics is still an open problem. In this paper, the inverse dynamic of a spatial parallel manipulator with two translational degrees of freedom and one rotational degree of freedom is studied based on the Newton-Euler approach. The kinematics analysis is firstly performed in a closed form. The inverse dynamic equation of this manipulator is formulated by using the Lagrange multiplier approach and choosing the Cartesian position and orientation as the generalized coordinates. Finally a numerical example is given for the kinematic and dynamic simulation of this manipulator. The model will be useful to improve the design of the mechanical components and the control algorithm.

Design and Evaluation of a Passive Ankle Prosthesis With Rotational Power Generation by a Compliant Coupling Between Leg Deflection and Ankle Rotation

2014 ◽  
Author(s):  
Jacob J. Rice ◽  
Joseph M. Schimmels
Keyword(s):  
Degrees Of Freedom ◽  
Gait Cycle ◽  
The Body ◽  
Degree Of Freedom ◽  
Rotational Degree ◽  
Kinematic Data ◽  
Active Behavior ◽  
Ankle Prosthesis ◽  
Compression Spring ◽  
Translational Degree

This paper presents the design and simulation results of a passive prosthetic ankle prosthesis that has mechanical behavior similar to a natural ankle. The presented design achieves active behavior with powered push-off to propel the body forward. The design contains a conventional compression spring network that allows coupling between two degrees of freedom. There is a translational degree of freedom along the leg and a rotational degree of freedom about the ankle joint. During a standard gait cycle, potential energy from the person’s weight is stored in the spring network from deflection along the leg. The energy is released by the spring network as rotation of the foot. With this design, capping the allowable leg deflection at 15 millimeters produces 45% of the rotational work that a natural ankle will produce. This is based on simulation using published average kinetic and kinematic data from gait analyses.

Estimation of Muscle Response Using Three-Dimensional Musculoskeletal Models Before Impact Situation: A Simulation Study

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Tae Soo Bae ◽  
Peter Loan ◽  
Kuiwon Choi ◽  
Daehie Hong ◽  
Mu Seong Mun
Keyword(s):  
Degrees Of Freedom ◽  
Motion Tracking ◽  
Tracking System ◽  
Three Dimensional ◽  
Dynamic Simulations ◽  
Inverse Dynamic ◽  
Low Speed ◽  
Car Crash ◽  
Musculoskeletal Models ◽  
Ankle Joints

When car crash experiments are performed using cadavers or dummies, the active muscles’ reaction on crash situations cannot be observed. The aim of this study is to estimate muscles’ response of the major muscle groups using three-dimensional musculoskeletal model by dynamic simulations of low-speed sled-impact. The three-dimensional musculoskeletal models of eight subjects were developed, including 241 degrees of freedom and 86 muscles. The muscle parameters considering limb lengths and the force-generating properties of the muscles were redefined by optimization to fit for each subject. Kinematic data and external forces measured by motion tracking system and dynamometer were then input as boundary conditions. Through a least-squares optimization algorithm, active muscles’ responses were calculated during inverse dynamic analysis tracking the motion of each subject. Electromyography for major muscles at elbow, knee, and ankle joints was measured to validate each model. For low-speed sled-impact crash, experiment and simulation with optimized and unoptimized muscle parameters were performed at 9.4 m/h and 10 m/h and muscle activities were compared among them. The muscle activities with optimized parameters were closer to experimental measurements than the results without optimization. In addition, the extensor muscle activities at knee, ankle, and elbow joint were found considerably at impact time, unlike previous studies using cadaver or dummies. This study demonstrated the need to optimize the muscle parameters to predict impact situation correctly in computational studies using musculoskeletal models. And to improve accuracy of analysis for car crash injury using humanlike dummies, muscle reflex function, major extensor muscles’ response at elbow, knee, and ankle joints, should be considered.

Bayesian Optimization Based Terrestrial Gait Tuning for a 12-DOF Alligator-Inspired Robot With Active Body Undulation

2018 ◽  
Author(s):  
Krishna Agrawal ◽  
Kushagra Jain ◽  
Dhawal Gupta ◽  
Raunak Srivastav ◽  
Abhijeet Agnihotri ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Critical Role ◽  
Parameter Tuning ◽  
The Body ◽  
Experimental Results ◽  
Bayesian Optimization ◽  
Terrestrial Locomotion ◽  
Gait Parameters ◽  
Rotational Degrees Of Freedom ◽  
The One

In addition to aiding in swimming, body undulation of an alligator plays a critical role in terrestrial locomotion by imparting stability. This paper reports design, fabrication and terrestrial locomotion control incorporating active body undulation of a 12-DOF alligator-inspired robot. Each of the four legs of the developed robot has two rotational degrees of freedom while the body can perform undulation using additional four rotational degrees of freedom. This paper also presents a Bayesian optimization based approach to tune the gait parameters of both leg oscillation and body undulation in order to maximize the average robot speed. We obtained improvement by a factor of 1.93 in average robot speed in comparison to the one obtained by randomly generated parameters and report the experimental results in this paper. In future, we plan to generalize the developed Bayesian optimization based parameter tuning approach for the swimming gait and thereby impart amphibious capabilities to the developed robot.

Delayed Position-Feedback Controller for the Reduction of Payload Pendulations of Rotary Cranes

2003 ◽  
Vol 9 (1-2) ◽  
pp. 257-277 ◽  
Author(s):  
Ziyad N. Masoud ◽  
Ali H. Nayfeh ◽  
Amjed Al-Mousa
Keyword(s):  
Control Strategy ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Scaled Model ◽  
Heavy Equipment ◽  
Position Feedback ◽  
Out Of Plane ◽  
Rotary Crane ◽  
Rotational Degrees Of Freedom ◽  
Successful Control

In this paper, we show that, in rotary cranes, it is possible to reduce payload pendulations significantly by controlling the crane's translational and rotational degrees of freedom. Such a control can be achieved with the heavy equipment that is already part of the crane, so that retrofitting existing cranes with such a controller would require little effort. Moreover, the control is superimposed transparently on the commands of the operator. The successful control strategy is based on delayed position feedback of the payload's in-plane and out-of-plane motions. Its effectiveness is demonstrated with a fully nonlinear three-dimensional computer simulation and with an experiment on a scaled model of a rotary crane. The results demonstrate that the pendulations can be significantly reduced, and therefore the rate of operation can be greatly increased. The effectiveness of the controller is demonstrated for both rotary and gantry modes of operation.

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