Repelling-Screw Based Force Analysis of Origami Mechanisms

2016 ◽  
Vol 8 (3) ◽  
Author(s):  
Chen Qiu ◽  
Ketao Zhang ◽  
Jian S. Dai
Keyword(s):  
Parallel Mechanism ◽  
Screw Theory ◽  
Reaction Force ◽  
Theoretical Background ◽  
Force Analysis ◽  
Modeling Approach ◽  
Reaction Forces ◽  
Redundantly Actuated

This paper provides an approach to model the reaction force of origami mechanisms when they are deformed. In this approach, an origami structure is taken as an equivalent redundantly actuated mechanism, making it possible to apply the forward-force analysis to calculating the reaction force of the origami structure. Theoretical background is provided in the framework of screw theory, where the repelling screw is introduced to integrate the resistive torques of folded creases into the reaction-force of the whole origami mechanism. Two representative origami structures are then selected to implement the developed modeling approach, as the widely used waterbomb base and the waterbomb-based integrated parallel mechanism. With the proposed kinematic equivalent, their reaction forces are obtained and validated, presenting a ground for force analysis of origami-inspired mechanisms.

Force analysis of the redundantly actuated parallel mechanism 2RPR+P considering different control methodologies

2021 ◽  
pp. 103783
Author(s):  
Yundou Xu ◽  
Ze Jiang ◽  
Zhongjin Ju ◽  
Zengzhao Wang ◽  
Wenlan Liu ◽  
...  
Keyword(s):  
Parallel Mechanism ◽  
Force Analysis ◽  
Redundantly Actuated

Reaction Force Analysis in Generalized Machine Systems

1973 ◽  
Vol 95 (2) ◽  
pp. 617-623 ◽  
Author(s):  
D. A. Smith
Keyword(s):  
Dynamic Systems ◽  
Virtual Work ◽  
Reaction Force ◽  
Inertial Forces ◽  
Force Analysis ◽  
Lagrange’S Equation ◽  
Reaction Forces ◽  
Applied Forces ◽  
Machine Systems ◽  
Centers Of Mass

A method is developed which reduces the calculation of reaction forces for multi-degree-of-freedom, constrained, mechanical, dynamic systems to a process of accumulating a sum of terms representing inertial forces, applied forces, and Lagrange multiplier forces. This method results in an approach to reaction force calculations which is computationally more efficient than either virtual work or equilibrium when these methods are applied in conventional ways. The method is based on selecting a tree for the network being simulated in which the chords of the network correspond to revolute pairs (for two-dimensional systems). When such a tree is determined, Lagrange’s equation with constraint is used to represent the mechanical system. If the paths to the centers of mass and the paths associated with applied forces are developed from tree branches, the Lagrange multipliers are directly interpretable in terms of the total reaction forces at the chords of the network. These multipliers are obtained in the process of determining the system motion. The remaining reaction forces and torques are determined by a sequence of additions.

Stiffness modelling and comparison of the 5-UPS/PRPU parallel machine tool with its non-redundant counterpart

2016 ◽  
Vol 231 (9) ◽  
pp. 1646-1657 ◽  
Author(s):  
Xin Zhou ◽  
Yundou Xu ◽  
Jiantao Yao ◽  
Kuijing Zheng ◽  
Yongsheng Zhao
Keyword(s):  
Machine Tool ◽  
Stiffness Matrix ◽  
Parallel Mechanism ◽  
Screw Theory ◽  
Virtual Work ◽  
Matrix Decomposition ◽  
Parallel Machine ◽  
Stiffness Model ◽  
Redundantly Actuated ◽  
Parallel Machine Tool

This article presents a derivation of the stiffness matrix of a general redundantly actuated parallel mechanism based on the overall Jacobian. The Jacobian of the constraints and actuations is derived using reciprocal screw theory. Based on the mapping relationship between constraint, actuated and external forces combined with the principle of virtual work, a compatibility equation for the deformation of all of the limbs is achieved, and the stiffness model of the general redundantly actuated parallel mechanism is derived. The 5-UPS/PRPU redundantly actuated parallel machine tool is used to illustrate this method. The parallel machine tool comprehensively reveals the effect of the elastic deformation of active–passive joints and some basic transmission parts. The stiffness model is further validated by experimental data. Moreover, the global stiffness matrix of the general redundantly actuated parallel mechanism can be separated into two parts via matrix decomposition. The first part is the stiffness matrix of the corresponding non-redundant parallel mechanism, and the second part is the stiffness matrix of the redundantly actuated limbs (actuators). The redundantly actuated 5-UPS/PRPU parallel machine tool is also investigated for further analysis. The different stiffness characteristics of the machine tool and its corresponding non-redundant 5-UPS/PRPU parallel machine tool are compared. Actuation redundancy is found to improve the stiffness performance of the machine tool efficiently.

Stiffness Design, Analysis and Validation of a Parallel-Mechanism Equivalent Suspension System

2015 ◽  
Author(s):  
Chen Qiu ◽  
Ketao Zhang ◽  
Jing Shan Zhao ◽  
Jian S. Dai
Keyword(s):  
Parallel Mechanism ◽  
Optimization Design ◽  
Screw Theory ◽  
Suspension System ◽  
Force Analysis ◽  
Design Constraint ◽  
Kinematic Design ◽  
Simulation Validation ◽  
Element Simulation ◽  
Stiffness Design

This paper provides a systematic approach to design a vehicle’s independent suspension system. In this approach, multi-link type suspension is selected. By treating it as a parallel mechanism, both the kinematic design and force analysis are conducted in the same framework of screw theory. Regarding the kinematic design, constraint-based approach is used to find suitable layouts of constraint limbs in accordance with desired degree of freedom. In the force analysis, stiffness matrix of the suspension mechanism is developed, leading to the deformation and stress analysis under various critical loads. The developed formulae are further utilized to design suitable suspension mechanism, followed by finite-element-simulation validation as well as optimization design to reduce the resulted maximum stresses.

Topological Reaction Force Analysis

1979 ◽  
Vol 101 (2) ◽  
pp. 192-198 ◽  
Author(s):  
J. R. Milner ◽  
D. A. Smith
Keyword(s):  
Reaction Force ◽  
Mechanical Systems ◽  
Computational Approach ◽  
Alternative Methods ◽  
Force Analysis ◽  
Dynamic Mechanical ◽  
Reaction Forces ◽  
Linear Graphs

A method of using directed linear graphs for the determination of reaction forces in dynamic mechanical systems is developed. The method is compatible with other more classical techniques for calculating reaction forces and results in a more efficient computational approach than alternative methods. Example problems are discussed and analyzed using these topological techniques.

A force analysis of a 3-RPS parallel mechanism by using screw theory

Robotica ◽  
2011 ◽  
Vol 29 (7) ◽  
pp. 959-965 ◽  
Author(s):  
Y. Zhao ◽  
J. F. Liu ◽  
Z. Huang
Keyword(s):  
Parallel Mechanism ◽  
Screw Theory ◽  
Mechanical Design ◽  
Parallel Manipulators ◽  
Simultaneous Equations ◽  
Force Analysis ◽  
New Approach ◽  
Numerical Example ◽  
And Control

SUMMARYThe force analysis of parallel manipulators is one of the important issues for mechanical design and control, but it is quite difficult often because of the excessive unknowns. A new approach using screw theory for a 3-RPS parallel mechanism is proposed in this paper. It is able to markedly reduce the number of unknowns and even make the number of simultaneous equations to solve not more than six each time, which may be called force decoupling. With this method, first the main-pair reactions need to be solved for, and then, the active forces and constraint reactions of all other kinematic pairs can be simultaneously obtained by analyzing the equilibrium of each body one by one. Finally, a numerical example and a discussion are given.

Ground reaction force analysis for assessing the efficacy of focused and radial shockwaves in the treatment of symptomatic plantar heel spur

2020 ◽  
pp. 1-9
Author(s):  
Piotr Król ◽  
Andrzej Franek ◽  
Tomasz Król ◽  
Arkadiusz Stanula ◽  
Paweł Dolibog ◽  
...  
Keyword(s):  
Shock Wave ◽  
Reaction Force ◽  
Extracorporeal Shock Wave Therapy ◽  
Therapeutic Effects ◽  
Force Analysis ◽  
Heel Spur ◽  
Temporal Parameters ◽  
Extracorporeal Shock Wave ◽  
Reaction Forces ◽  
Foot Function

BACKGROUND: Extracorporeal shock wave therapy is among the conservative treatments for symptomatic heel spur. OBJECTIVE: The purpose of this trial is to evaluate and compare the therapeutic effects of radial shock wave (RSWT) and focused shock wave (FSWT) applied in the treatment of symptomatic heel spur. METHODS: Fifty-five participants were randomly divided into two comparative groups that were administered FSWT and RSWT, respectively. The severity of dysfunction (Foot Function Index, FFI), ground reaction forces (GRF) and walking temporal parameters were measured in all patients at baseline and at weeks 1, 3, 6, 12 and 24 after treatment. RESULTS: In both groups, a gradual decrease in the FFI values occurred after treatment. The percentage reduction in the FFI was comparable for both groups. Statistically significant changes were only noted between some measurements of GRF and walking temporal parameters. The percentage changes in the values of the force and temporal parameters were similar between the groups. CONCLUSIONS: Both FSWT and RSWT are efficacious in the treatment of symptomatic heel spur and their therapeutic effects are comparable. Objective data registered by force platforms during walking are not useful for tracing the progress of treatment applied to patients with symptomatic heel spur between consecutive procedures.

Intramolecular Proton Transfer in the Isomerization of Hydroxyacetone: A Detailed Characterization Based on Reaction Force Analysis and the Bond Fragility Spectrum

2020 ◽  
Author(s):  
Wallace Derricotte ◽  
Huiet Joseph
Keyword(s):  
Chemical Potential ◽  
Reaction Force ◽  
Intramolecular Proton Transfer ◽  
Intermediate Energy ◽  
Force Analysis ◽  
Activation Energy Barrier ◽  
Detailed Characterization ◽  
Proton Transfers ◽  
Reaction Force Constant

The mechanism of isomerization of hydroxyacetone to 2-hydroxypropanal is studied within the framework of reaction force analysis at the M06-2X/6-311++G(d,p) level of theory. Three unique pathways are considered: (i) a step-wise mechanism that proceeds through formation of the Z-isomer of their shared enediol intermediate, (ii) a step-wise mechanism that forms the E-isomer of the enediol, and (iii) a concerted pathway that bypasses the enediol intermediate. Energy calculations show that the concerted pathway has the lowest activation energy barrier at 45.7 kcal mol<sup>-1</sup>. The reaction force, chemical potential, and reaction electronic flux are calculated for each reaction to characterize electronic changes throughout the mechanism. The reaction force constant is calculated in order to investigate the synchronous/asynchronous nature of the concerted intramolecular proton transfers involved. Additional characterization of synchronicity is provided by calculating the bond fragility spectrum for each mechanism.

scholarly journals Running ground reaction forces across footwear conditions are predicted from the motion of two body mass components

2019 ◽  
Vol 126 (5) ◽  
pp. 1315-1325 ◽  
Author(s):  
Andrew B. Udofa ◽  
Kenneth P. Clark ◽  
Laurence J. Ryan ◽  
Peter G. Weyand
Keyword(s):  
Ground Reaction Force ◽  
Lower Limb ◽  
Reaction Force ◽  
Ground Reaction Forces ◽  
Vertical Ground Reaction Force ◽  
Time Patterns ◽  
Foot Strike ◽  
Reaction Forces ◽  
Vertical Ground ◽  
Force Time

Although running shoes alter foot-ground reaction forces, particularly during impact, how they do so is incompletely understood. Here, we hypothesized that footwear effects on running ground reaction force-time patterns can be accurately predicted from the motion of two components of the body’s mass (mb): the contacting lower-limb (m1 = 0.08mb) and the remainder (m2 = 0.92mb). Simultaneous motion and vertical ground reaction force-time data were acquired at 1,000 Hz from eight uninstructed subjects running on a force-instrumented treadmill at 4.0 and 7.0 m/s under four footwear conditions: barefoot, minimal sole, thin sole, and thick sole. Vertical ground reaction force-time patterns were generated from the two-mass model using body mass and footfall-specific measures of contact time, aerial time, and lower-limb impact deceleration. Model force-time patterns generated using the empirical inputs acquired for each footfall matched the measured patterns closely across the four footwear conditions at both protocol speeds ( r2 = 0.96 ± 0.004; root mean squared error  = 0.17 ± 0.01 body-weight units; n = 275 total footfalls). Foot landing angles (θF) were inversely related to footwear thickness; more positive or plantar-flexed landing angles coincided with longer-impact durations and force-time patterns lacking distinct rising-edge force peaks. Our results support three conclusions: 1) running ground reaction force-time patterns across footwear conditions can be accurately predicted using our two-mass, two-impulse model, 2) impact forces, regardless of foot strike mechanics, can be accurately quantified from lower-limb motion and a fixed anatomical mass (0.08mb), and 3) runners maintain similar loading rates (ΔFvertical/Δtime) across footwear conditions by altering foot strike angle to regulate the duration of impact. NEW & NOTEWORTHY Here, we validate a two-mass, two-impulse model of running vertical ground reaction forces across four footwear thickness conditions (barefoot, minimal, thin, thick). Our model allows the impact portion of the impulse to be extracted from measured total ground reaction force-time patterns using motion data from the ankle. The gait adjustments observed across footwear conditions revealed that runners maintained similar loading rates across footwear conditions by altering foot strike angles to regulate the duration of impact.

scholarly journals Ground Reaction Forces and Kinematics of Ski Jump Landing Using Wearable Sensors

Sensors ◽  
2019 ◽  
Vol 19 (9) ◽  
pp. 2011 ◽  
Author(s):  
Bessone ◽  
Petrat ◽  
Schwirtz
Keyword(s):  
Wearable Sensors ◽  
Reaction Force ◽  
Ground Reaction Forces ◽  
Inertial Motion ◽  
Jump Landing ◽  
The Past ◽  
Landing Biomechanics ◽  
Reaction Forces ◽  
The Hill ◽  
Kinematics And Kinetics

In the past, technological issues limited research focused on ski jump landing. Today, thanks to the development of wearable sensors, it is possible to analyze the biomechanics of athletes without interfering with their movements. The aims of this study were twofold. Firstly, the quantification of the kinetic magnitude during landing is performed using wireless force insoles while 22 athletes jumped during summer training on the hill. In the second part, the insoles were combined with inertial motion units (IMUs) to determine the possible correlation between kinematics and kinetics during landing. The maximal normal ground reaction force (GRFmax) ranged between 1.1 and 5.3 body weight per foot independently when landing using the telemark or parallel leg technique. The GRFmax and impulse were correlated with flying time (p < 0.001). The hip flexions/extensions and the knee and hip rotations of the telemark front leg correlated with GRFmax (r = 0.689, p = 0.040; r = −0.670, p = 0.048; r = 0.820, p = 0.007; respectively). The force insoles and their combination with IMUs resulted in promising setups to analyze landing biomechanics and to provide in-field feedback to the athletes, being quick to place and light, without limiting movement.

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