A Kirigami-Inspired 8R Linkage and Its Evolved Overconstrained 6R Linkages With the Rotational Symmetry of Order Two

2014 ◽  
Vol 6 (2) ◽  
Author(s):  
Ketao Zhang ◽  
Jian S. Dai
Keyword(s):  
Screw Theory ◽  
Rotational Symmetry ◽  
Structural Evolution ◽  
Joint Space ◽  
Geometric Characteristics ◽  
Constraint Analysis ◽  
Motion Parameters ◽  
Motion Characteristics ◽  
The Relationship

This paper presents a novel metamorphic 8R linkage extracted from a kirigami-fold with pregrooved creases and two overconstrained 6R linkages evolved from the 8R linkage by taking the concept of metamorphosis in the sense of structural evolution. The geometric characteristics and the parametric constraints of the evolved 6R linkages are identified following the structural evolution of the 8R linkage. The paper reveals that the evolved 6R linkages are special line-symmetric Bricard 6R loops characterized by the rotational symmetry of order two. The joint space of the overconstrained 6R linkages is analyzed and the relationship between motion parameters of the evolved 6R linkages and reconfiguration parameters of the metamorphic 8R linkage are derived. The motion characteristics of the overconstrained 6R linkages are further verified in terms of screw theory. The bifurcation and trifurcation associated with various transitory positions of the evolved 6R linkages having distinct parametric constraints are consequently identified based on constraint analysis.

A Family of Overconstrained 6R Linkages With the Rotational Symmetry of Order 2

2012 ◽  
Author(s):  
Ketao Zhang ◽  
Jian S. Dai
Keyword(s):  
Screw Theory ◽  
Rotational Symmetry ◽  
Structural Evolution ◽  
Joint Space ◽  
Structure Evolution ◽  
Motion Parameters

This paper presents a family of overconstrained 6R linkages with the rotational symmetry of order 2 which refers to rotation by an angle of 360°/n (n = 2) with respect to a particular axis leaves the linkage unchanged. The overconstrained 6R linkages are evolved from a reconfigurable 8R linkage which is extracted from deployable origami-fold. The structure evolution of the 8R linkage takes the concept of metamorphosis in the sense of structural evolution. This leads to a generic way for investigating new mechanisms inspired from origami fold. The geometry and two-fold rotational symmetry reveal that the overconstrained 6R linkages are special line-symmetric Bricard 6R loops and the parametric constraints of the 6R linkages are identified. The kinematics of the overconstrained 6R linkage is analyzed and motion parameters of the joint space are derived. The unique mobility of the overconstrained 6R linkages is further verified in terms of screw theory.

scholarly journals Research on Kinematics and Pouring Law of a Mobile Heavy Load Pouring Robot

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Long Li ◽  
Chengjun Wang ◽  
Hongtao Wu
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Position Control ◽  
Screw Theory ◽  
Great Influence ◽  
Inverse Kinematic ◽  
The Novel ◽  
Heavy Load ◽  
Motion Characteristics ◽  
The Relationship

In order to meet the requirement of continuous pouring in many varieties and small batches in casting production, a mobile heavy load pouring robot is developed based on a new 4-UPU parallel mechanism due to its strong carrying capacity. Firstly, the instantaneous motion characteristics of the novel 4-UPU parallel mechanism with four degrees of freedom (DOF) are analyzed using screw theory. By using the geometric method, both the forward and inverse kinematic solutions of the proposed robot system are given out. Secondly, based on a common pouring ladle, the volume change of pouring liquid in pouring process and the relationship between tilting angular velocity and flow rate are analyzed, and the results show that the shape of the ladle and the design of the pouring mouth have great influence on the tilting model. It is an important basis for the division of the sectional model. Finally, a numerical example is given to verify the effectiveness of the developed tilting model. The mapping relation between the tilting model and the parallel mechanism shows that the pouring flow can be adjusted by controlling the movement of parallel manipulator. The research of this paper provides an important theoretical basis for the position control of mobile heavy load pouring robot and the research of pouring speed control.

On the Integrability of Screw Spaces

1992 ◽  
Vol 114 (2) ◽  
pp. 251-256 ◽  
Author(s):  
S. W. Peterson
Keyword(s):  
Tangent Space ◽  
Screw Theory ◽  
Joint Space ◽  
Rigid Bodies ◽  
Joint Contact ◽  
A Chain ◽  
Configuration Manifold ◽  
Relationship Of ◽  
The Relationship ◽  
Line Space

In the development of a method for generating the dynamic equations of a chain of rigid bodies in elliptic line space, it has been discovered that the joint freedom spaces from the tangent space of the system’s joint space, called the configuration manifold by dynamicists. The freedom space of a joint can be calculated from the joint contact geometry using reciprocal screw theory. The present paper describes the relationship of the joint freedom spaces to the tangent space of the configuration manifold, and determines the integrability conditions which must be satisfied if the freedom space represents a valid configuration manifold. The paper also shows that the integrability of the tangent space of a chain of rigid bodies is established once the integrability of each joint freedom space has been demonstrated. These conditions are used to define valid generalized coordinates for describing the chain’s configuration. Cylindrical and spherical joints are treated as examples.

scholarly journals Research on Measurement Method of Parachute Scanning Platform Based on MEMS Device

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 402
Author(s):  
Ning Liu ◽  
Tianqi Tian ◽  
Zhong Su ◽  
Wenhao Qi
Keyword(s):  
Physical Simulation ◽  
Inertial Sensors ◽  
Rotational Velocity ◽  
Attitude Measurement ◽  
Matlab Simulation ◽  
Scanning Angle ◽  
Reduce Development Time ◽  
Motion Parameters ◽  
Motion Characteristics ◽  
Scanning Motion

This paper studies the measurement of motion parameters of a parachute scanning platform. The movement of a parachute scanning platform has fast rotational velocity and a complex attitude. Therefore, traditional measurement methods cannot measure the motion parameters accurately, and thus fail to satisfy the requirements for the measurement of parachute scanning platform motion parameters. In order to solve these problems, a method for measuring the motion parameters of a parachute scanning platform based on a combination of magnetic and inertial sensors is proposed in this paper. First, scanning motion characteristics of a parachute-terminal-sensitive projectile are analyzed. Next, a high-precision parachute scanning platform attitude measurement device is designed to obtain the data of magnetic and inertial sensors. Then the extended Kalman filter is used to filter and observe errors. The scanning angle, the scanning angle velocity, the falling velocity, and the 2D scanning attitude are obtained. Finally, the accuracy and feasibility of the algorithm are analyzed and validated by MATLAB simulation, semi-physical simulation, and airdrop experiments. The presented research results can provide helpful references for the design and analysis of parachute scanning platforms, which can reduce development time and cost.

scholarly journals AB0867 INCREASED ADIPONECTIN LEVELS ARE ASSOCIATED WITH HIGHER RADIOGRAPHIC SCORES IN THE KNEE JOINT, BUT NOT IN THE HAND JOINT: THE DONG-GU STUDY

2020 ◽  
Vol 79 (Suppl 1) ◽  
pp. 1740.1-1740
Author(s):  
J. H. Kang ◽  
S. E. Choi ◽  
H. Xu ◽  
D. J. Park ◽  
S. S. Lee
Keyword(s):  
Body Mass Index ◽  
Knee Joint ◽  
Body Mass ◽  
Linear Regression Analysis ◽  
Joint Space ◽  
Serum Adiponectin ◽  
Hand Osteoarthritis ◽  
X Rays ◽  
Subchondral Cyst ◽  
The Relationship

Background:Several studies have evaluated the association between serum adiponectin levels and knee and hand osteoarthritis (OA), with mixed results.Objectives:The aim of this study was to investigate the relationship between OA and serum adiponectin levels according to the radiographic features of knee and hand OA.Methods:A total of 2,402 subjects were recruited from the Dong-gu Study. Baseline characteristics were collected via a questionnaire, and X-rays of knee and hand joints were scored by a semi-quantitative grading system. The relationship between serum adiponectin levels and radiographic severity was evaluated by linear regression analysis.Results:Subjects with higher tertiles of serum adiponectin were older and had a lower body mass index than those with lower tertiles. In the knee joint scores, serum adiponectin levels were positively associated with the total score (P<0.001), osteophyte score (P=0.003), and joint space narrowing (JSN) score (P<0.001) among the three tertiles after adjustment for age, sex, body mass index, smoking, alcohol consumption, education, and physical activity. In the hand joint scores, no association was found between serum adiponectin levels and the total score, osteophyte score, JSN score, subchondral cyst score, sclerosis score, erosion score, and malalignment score among the three tertiles after adjustment.Conclusion:In this study, we found that increased adiponectin levels were associated with higher radiographic scores in the knee joint, but not in the hand joint, suggesting different pathophysiologic mechanisms in the development of OA.Disclosure of Interests:None declared

scholarly journals Relationship between the Track and Structural Evolution of Hurricane Sandy (2012) Using a Regional Ensemble

2018 ◽  
Vol 146 (12) ◽  
pp. 4279-4302 ◽  
Author(s):  
Alex M. Kowaleski ◽  
Jenni L. Evans
Keyword(s):  
Large Scale ◽  
Wrf Model ◽  
Structural Evolution ◽  
Hurricane Sandy ◽  
Weather Research And Forecasting ◽  
Extratropical Transition ◽  
Ensemble Forecasts ◽  
High Predictability ◽  
Regression Mixture ◽  
The Relationship

Abstract An ensemble of 72 Weather Research and Forecasting (WRF) Model simulations is evaluated to examine the relationship between the track of Hurricane Sandy (2012) and its structural evolution. Initial and boundary conditions are obtained from ECMWF and GEFS ensemble forecasts initialized at 0000 UTC 25 October. The 5-day WRF simulations are initialized at 0000 UTC 27 October, 48 h into the global model forecasts. Tracks and cyclone phase space (CPS) paths from the 72 simulations are partitioned into 6 clusters using regression mixture models; results from the 4 most populous track clusters are examined. The four analyzed clusters vary in mean landfall location from southern New Jersey to Maine. Extratropical transition timing is the clearest difference among clusters; more eastward clusters show later Sandy–midlatitude trough interaction, warm seclusion formation, and extratropical transition completion. However, the intercluster variability is much smaller when examined relative to the landfall time of each simulation. In each cluster, a short-lived warm seclusion forms and contracts through landfall while lower-tropospheric potential vorticity concentrates at small radii. Despite the large-scale similarity among the clusters, relevant intercluster differences in landfall-relative extratropical transition are observed. In the easternmost cluster the Sandy–trough interaction is least intense and the warm seclusion decays the most by landfall. In the second most eastward cluster Sandy retains the most intact warm seclusion at landfall because of a slightly later (relative to landfall) and weaker trough interaction compared to the two most westward clusters. Nevertheless, the remarkably similar large-scale evolution of Sandy among the four clusters indicates the high predictability of Sandy’s warm seclusion extratropical transition before landfall.

Automatic Planning of Smooth Trajectories for Pick-and-Place Operations

1991 ◽  
Author(s):  
Clément M. Gosselin ◽  
Ammar Hadj-Messaoud
Keyword(s):  
Joint Space ◽  
Inverse Kinematic ◽  
Planning Problem ◽  
Inverse Kinematic Problem ◽  
Polynomial Solutions ◽  
Joint Coordinates ◽  
Pick And Place ◽  
Lift Off ◽  
The Relationship ◽  
Third Derivative

Abstract This paper proposes some new polynomial solutions to the trajectory planning problem encountered in pick-and-place operations. When a robotic manipulator is used for such operations, it is possible to plan the required trajectory in joint space, provided that the inverse kinematic problem has been solved for the initial and final configurations — and possibly for a lift-off and a set-down configuration — and that the workspace is free of obstacles. Polynomial solutions to this problem can be found in the literature. However, they usually provide continuity up to the second derivative only, leading to a discontinuous jerk. The solutions derived in this paper preserve the continuity of the third derivative of the joint coordinates, thereby ensuring smooth trajectories with smooth variations of the actuator currents. Moreover, whenever possible, unique polynomial expressions valid between the initial and final configurations are used in order to simplify the logic. Polynomial formulations without lift-off and set-down configurations are first presented. Then, these intermediate configurations are introduced, leading to a new set of solutions. A global algorithm is then discussed in order to clearly indicate the relationship between the different solutions. Finally, an example illustrating the application to a pick-and-place operation is solved.

scholarly journals Intra-Articular Pressure in Osteoarthritis of the Knee

2020 ◽  
Author(s):  
kai niu ◽  
le hai Pan
Keyword(s):  
Joint Space Narrowing ◽  
Normal Subjects ◽  
Joint Space ◽  
Positive Pressure ◽  
Osteoarthritis Of The Knee ◽  
Research Subjects ◽  
Pressure Profiles ◽  
Control Knee ◽  
Group 2 ◽  
The Relationship

Abstract Background: IAP （intra-articular pressure）of the knee has been extensively studied in the knee of rheumatoid arthritis1.3 . the relationship between IAP and osteoarthrosis of knee rarely mentioned in the literature. The purpose of the study was to discover the pressure profiles observed in OA(Osteoarthritis ）. The characteristics of osteoarthritis are multiple osteophytes, unstable chondral flaps ,joint-space narrowing，sclerosis. Whether these factors effect of osteoarthritis intra-articular pressure.Methods: Fifty three research subjects were studied. They were divided into two subgroups, group 1: Forty osteoarthritis (OA). group 2: Thirteen control knee of healthy volunteer. IAP was measured using the hand held portable water manometer. before operation of arthroscopic procedures in OAgroup . Research data were analyzed to identify IAP between the two groups. Results: The main findingwasthat Resting IAP was positive pressure in all Osteoarthritis joints, otherwise subatmospheric or weakly atmospheric in normal subjects. Conclusions: The IAP rising is a feature of all patients with OAgroup. Therefore, These observations we recognize that significantly increased resting IAP is major influences by multiple osteophytes, joint-space narrowing，sclerosis , loose bodies and definite deformity of bony ends.

Effect of Pearlite Structure on the Mechanical Properties of Microalloyed Hypereutectoid Steels

2005 ◽  
Vol 500-501 ◽  
pp. 737-744 ◽  
Author(s):  
A.M. Elwazri ◽  
Steve Yue
Keyword(s):  
Mechanical Properties ◽  
Structural Evolution ◽  
Salt Bath ◽  
Austenite Grain Size ◽  
Boundary Area ◽  
Austenite Grain ◽  
Heat Treated ◽  
Hypereutectoid Steels ◽  
The Relationship ◽  
Different Levels

The relationship between mechanical properties and pearlite microstructure was investigated using various heat treatments on a hypereutectoid steels containing 1% carbon with different levels of vanadium and silicon. Specimens were heat treated at various temperatures ranging from 900 to 1200°C and transferred to salt bath conditions at 550, 580 and 620°C to examine the structural evolution of pearlite. The results show that the thickness of the cementite network increases with increasing reheat temperature. This is likely due to the larger austenite grain size reducing the grain boundary area available for proeutectoid cementite nucleation. It was found that the vanadium and silicon additions increased the strength of hypereutectoid steels through refinement of the microstructure and precipitation strengthening.

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