Two Basic Features of Instantaneous Conjugate Motion and Their Importance in Facilitating Motion Analysis

2004 ◽  
Vol 126 (1) ◽  
pp. 119-127 ◽  
Author(s):  
Chih-Hsin Chen ◽  
Janet Hong-Jian Chen
Keyword(s):  
Motion Analysis ◽  
Mechanical Systems ◽  
Body Motion ◽  
Geometrical Constraints ◽  
Free Body ◽  
Basic Features

Two basic features of instantaneous conjugate motion, which distinguishes it from instantaneous free body motion, are pointed out. Their influences on the geometrical constraints requisite for surface/line conjugation are discussed. Their importance in facilitating motion analysis of mechanical systems through linearization of relevant equations is clarified. Two illustrative examples are cited.

Structures of the Phosphazenes [ClC(NPCl3)2]+PCl6 − and [CH3C(NPCl3)2]+SbCl6 − at 90 K

1997 ◽  
Vol 53 (6) ◽  
pp. 953-960 ◽  
Author(s):  
F. Belaj
Keyword(s):  
Rigid Body ◽  
Motion Analysis ◽  
Rigid Body Motion ◽  
Body Motion ◽  
Torsion Angles ◽  
Ionic Compounds ◽  
Intramolecular Motions

The asymmetric units of both ionic compounds [N-(chloroformimidoyl)phosphorimidic trichloridato]trichlorophosphorus hexachlorophosphate, [ClC(NPCl3)2]+PCl^{-}_{6} (1), and [N-(acetimidoyl)phosphorimidic trichloridato]trichlorophosphorus hexachloroantimonate, [CH3C(NPCl3)2]+SbCl^{-}_{6} (2), contain two formula units with the atoms located on general positions. All the cations show cis–trans conformations with respect to their X—C—N—P torsion angles [X = Cl for (1), C for (2)], but quite different conformations with respect to their C—N—P—Cl torsion angles. Therefore, the two NPCl3 groups of a cation are inequivalent, even though they are equivalent in solution. The very flexible C—N—P angles ranging from 120.6 (3) to 140.9 (3)° can be attributed to the intramolecular Cl...Cl and Cl...N contacts. A widening of the C—N—P angles correlates with a shortening of the P—N distances. The rigid-body motion analysis shows that the non-rigid intramolecular motions in the cations cannot be explained by allowance for intramolecular torsion of the three rigid subunits about specific bonds.

scholarly journals An SMA Passive Ankle Foot Orthosis: Design, Modeling, and Experimental Evaluation

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Liberty Deberg ◽  
Masood Taheri Andani ◽  
Milad Hosseinipour ◽  
Mohammad Elahinia
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Motion Analysis ◽  
Experimental Evaluation ◽  
Mechanical Systems ◽  
Drop Foot ◽  
Ankle Foot Orthosis ◽  
New Device ◽  
Superelastic Behavior ◽  
Foot Orthosis

Shape memory alloys (SMAs) provide compact and effective actuation for a variety of mechanical systems. In this work, the distinguished superelastic behavior of these materials is utilized to develop a passive ankle foot orthosis to address the drop foot disability. Design, modeling, and experimental evaluation of an SMA orthosis employed in an ankle foot orthosis (AFO) are presented in this paper. To evaluate the improvements achieved with this new device, a prototype is fabricated and motion analysis is performed on a drop foot patient. Results are presented to demonstrate the performance of the proposed orthosis.

Dynamics of Mechanical Systems and the Generalized Free-Body Diagram—Part I: General Formulation

2008 ◽  
Vol 75 (6) ◽  
Author(s):  
József Kövecses
Keyword(s):  
Configuration Space ◽  
Dynamic Equilibrium ◽  
Mechanical Systems ◽  
Constrained Systems ◽  
Dynamic Equations ◽  
Analytical Mechanics ◽  
Constrained Motion ◽  
Equilibrium Equations ◽  
Free Body Diagram ◽  
Free Body

In this paper, we generalize the idea of the free-body diagram for analytical mechanics for representations of mechanical systems in configuration space. The configuration space is characterized locally by an Euclidean tangent space. A key element in this work relies on the relaxation of constraint conditions. A new set of steps is proposed to treat constrained systems. According to this, the analysis should be broken down to two levels: (1) the specification of a transformation via the relaxation of the constraints; this defines a subspace, the space of constrained motion; and (2) specification of conditions on the motion in the space of constrained motion. The formulation and analysis associated with the first step can be seen as the generalization of the idea of the free-body diagram. This formulation is worked out in detail in this paper. The complement of the space of constrained motion is the space of admissible motion. The parametrization of this second subspace is generally the task of the analyst. If the two subspaces are orthogonal then useful decoupling can be achieved in the dynamics formulation. Conditions are developed for this orthogonality. Based on this, the dynamic equations are developed for constrained and admissible motions. These are the dynamic equilibrium equations associated with the generalized free-body diagram. They are valid for a broad range of constrained systems, which can include, for example, bilaterally constrained systems, redundantly constrained systems, unilaterally constrained systems, and nonideal constraint realization.

Modeling of Flexible Bodies for Multibody Dynamic Systems Using Ritz Vectors

1994 ◽  
Vol 116 (2) ◽  
pp. 437-444 ◽  
Author(s):  
H. T. Wu ◽  
N. K. Mani
Keyword(s):  
Dynamic Analysis ◽  
Mechanical Systems ◽  
Normal Modes ◽  
Body Motion ◽  
Constraint Forces ◽  
Flexible Bodies ◽  
Static Correction ◽  
Ritz Vectors ◽  
Regeneration Procedure ◽  
Special Distribution

Vibration normal modes and static correction modes have been previously used to model flexible bodies for dynamic analysis of mechanical systems. The efficiency and accuracy of using these modes to model a system depends on both the flexibility of each body and the applied loads. This paper develops a generalized method for the generation of a set of Ritz vectors to be used in addition to vibration normal modes to form the modal basis to model flexible bodies for dynamic analysis of multibody mechanical systems. The Ritz vectors are generated using special distribution of the D’Alembert force and the kinematic constraint forces due to gross-body motion of a flexible body. Combined with vibration normal modes, they form more efficient vector bases for the modeling of flexible bodies comparing to using vibration normal modes alone or using the combination of static correction modes and vibration normal modes. Ritz vectors can be regenerated when the system undergoes significant changes of its configuration and the regeneration procedure is inexpensive. The effectiveness of using the combination of vibration normal modes and the proposed Ritz vectors is demonstrated using a planar slider-crank mechanism.

Validity of the Perception Neuron inertial motion capture system for upper body motion analysis

Measurement ◽  
2020 ◽  
Vol 149 ◽  
pp. 107024 ◽  
Author(s):  
Ryan Sers ◽  
Steph Forrester ◽  
Esther Moss ◽  
Stephen Ward ◽  
Jianjia Ma ◽  
...  
Keyword(s):  
Motion Analysis ◽  
Motion Capture ◽  
Body Motion ◽  
Upper Body ◽  
Motion Capture System ◽  
Inertial Motion
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