Bias deployable grids with horizontal compound scissor-like elements: A geometric study of the folding/deployment process

2021 ◽  
pp. 095605992110640
Author(s):  
Manuel J Freire-Tellado ◽  
Manuel Muñoz-Vidal ◽  
Juan Pérez-Valcárcel
Keyword(s):  
Structural Unit ◽  
Kinematic Model ◽  
Three Dimensional ◽  
Angular Distortion ◽  
Structural Units ◽  
Load Bearing ◽  
Stable Structures ◽  
Geometric Study

Bias deployable structural units are two-way structures arranged in a rotational pattern with respect to the edges. They have interesting advantages such as robust three-dimensional operation with supports around their entire base perimeter and the exclusive use of load-bearing scissor-like elements (SLEs). However, they do not have edge trims and their resistance to angular distortion is limited. This article proposes a series of deployable bi-stable structures that address these problems and incorporate new, resilient features. A method of analysing the incompatibilities of the structural unit is developed based solely on the geometric study of the deployment process, which allows the level of incompatibility of the proposal to be graduated, varying from stress-free structures to bi-stable structures. A kinematic model of one of the proposals allows the research undertaken to be contrasted.

New Efficient and Accurate Method of Nonlinear Analysis of Offshore Tubular Frames (the Idealized Structural Unit Method)

1985 ◽  
Vol 107 (2) ◽  
pp. 204-211 ◽  
Author(s):  
Y. Ueda ◽  
S. M. H. Rashed ◽  
K. Nakacho
Keyword(s):  
Residual Stresses ◽  
Nonlinear Analysis ◽  
Structural Unit ◽  
Three Dimensional ◽  
Nonlinear Behavior ◽  
Accurate Method ◽  
Large Deflections ◽  
Structural Units ◽  
High Degree

The Idealized Structural Unit Method [1, 2] is applied to the analysis of nonlinear behavior of three-dimensional offshore tubular frames. To this purpose the “tubular structural unit” is developed and used to analyze the entire behavior of the frame until final collapse. In this method large deflections, instability, plasticity and the effect of residual stresses and initial out of straightness are considered. Modeling of a structure is very simple since large structural units are regarded as elements. The required computer effort is very small while attaining a high degree of accuracy and reliability.

Research on the printing error of tilted vertical beams in delta-robot 3D printers

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yuezong Wang ◽  
Jinghui Liu ◽  
Mengfei Guo ◽  
LiuQIan Wang
Keyword(s):  
3D Printing ◽  
Kinematic Model ◽  
Three Dimensional ◽  
3D Printer ◽  
Simulation Approach ◽  
Content Type ◽  
Printing Quality ◽  
Delta Robot ◽  
Error Generation ◽  
Error Simulation

Purpose A three-dimensional (3D) printing error simulation approach is proposed to analyze the influence of tilted vertical beams on the 3D printing accuracy. The purpose of this study is to analyze the influence of such errors on printing accuracy and printing quality for delta-robot 3D printer. Design/methodology/approach First, the kinematic model of a delta-robot 3D printer with an ideal geometric structure is proposed by using vector analysis. Then, the normal kinematic model of a nonideal delta-robot 3D robot with tilted vertical beams is derived based on the above ideal kinematic model. Finally, a 3D printing error simulation approach is proposed to analyze the influence of tilted vertical beams on the 3D printing accuracy. Findings The results show that tilted vertical beams can indeed cause 3D printing errors and further influence the 3D printing quality of the final products and that the 3D printing errors of tilted vertical beams are related to the rotation angles of the tilted vertical beams. The larger the rotation angles of the tilted vertical beams are, the greater the geometric deformations of the printed structures. Originality/value Three vertical beams and six horizontal beams constitute the supporting parts of the frame of a delta-robot 3D printer. In this paper, the orientations of tilted vertical beams are shown to have a significant influence on 3D printing accuracy. However, the effect of tilted vertical beams on 3D printing accuracy is difficult to capture by instruments. To reveal the 3D printing error mechanisms under the condition of tilted vertical beams, the error generation mechanism and the quantitative influence of tilted vertical beams on 3D printing accuracy are studied by simulating the parallel motion mechanism of a delta-robot 3D printer with tilted vertical beams.

scholarly journals Formation of integrated structural units using the systematic and integrated method when implementing high-rise construction projects

2018 ◽  
Vol 33 ◽  
pp. 03075 ◽  
Author(s):  
Ivan Abramov
Keyword(s):  
Construction Projects ◽  
Structural Unit ◽  
System Analysis ◽  
Research Priorities ◽  
Structural Units ◽  
Factors Affecting ◽  
Reliability Criterion ◽  
Integrated Method ◽  
Destabilizing Factors ◽  
The Impact

Development of design documentation for a future construction project gives rise to a number of issues with the main one being selection of manpower for structural units of the project’s overall implementation system. Well planned and competently staffed integrated structural construction units will help achieve a high level of reliability and labor productivity and avoid negative (extraordinary) situations during the construction period eventually ensuring improved project performance. Research priorities include the development of theoretical recommendations for enhancing reliability of a structural unit staffed as an integrated construction crew. The author focuses on identification of destabilizing factors affecting formation of an integrated construction crew; assessment of these destabilizing factors; based on the developed mathematical model, highlighting the impact of these factors on the integration criterion with subsequent identification of an efficiency and reliability criterion for the structural unit in general. The purpose of this article is to develop theoretical recommendations and scientific and methodological provisions of an organizational and technological nature in order to identify a reliability criterion for a structural unit based on manpower integration and productivity criteria. With this purpose in mind, complex scientific tasks have been defined requiring special research, development of corresponding provisions and recommendations based on the system analysis findings presented herein.

scholarly journals Calibration of Kinematic Parameters of Robot Arm Using Laser Tracking System: Compensation for Non-Geometric Errors by Neural Networks and Selection of Optimal Measuring Points by Genetic Algorithm

2012 ◽  
Vol 6 (1) ◽  
pp. 29-37 ◽  
Author(s):  
Seiji Aoyagi ◽  
◽  
Masato Suzuki ◽  
Tomokazu Takahashi ◽  
Jun Fujioka ◽  
...  
Keyword(s):  
Genetic Algorithm ◽  
Neural Networks ◽  
Tracking System ◽  
Kinematic Model ◽  
Three Dimensional ◽  
Geometric Parameters ◽  
Geometric Errors ◽  
Robot Arm ◽  
Positioning Accuracy ◽  
Laser Tracking

Offline teaching based on high positioning accuracy of a robot arm is desired to take the place of manual teaching. In offline teaching, joint angles are calculated using a kinematic model of the robot arm. However, a nominal kinematic model does not consider the errors arising in manufacturing or assembly, not to mention the non-geometric errors arising in gear transmission, arm compliance, etc. Therefore, a method of precisely calibrating the parameters in a kinematic model is required. For this purpose, it is necessary to measure the three-dimensional (3-D) absolute position of the tip of a robot arm. In this paper, a laser tracking system is employed as the measurement apparatus. The geometric parameters in the robot kinematic model are calibrated by minimizing errors between the measured positions and the predicted ones based on the model. The residual errors caused by non-geometric parameters are further reduced by using neural networks, realizing high positioning accuracy of sub-millimeter order. To speed up the calibration process, a smaller number of measuring points is preferable. Optimal measuring points, which realize high positioning accuracy while remaining small in number, are selected using Genetic Algorithm (GA).

A Mobile Motion Capture System Based on Inertial Sensors and Smart Shoes

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Pyeong-Gook Jung ◽  
Sehoon Oh ◽  
Gukchan Lim ◽  
Kyoungchul Kong
Keyword(s):  
Motion Capture ◽  
Inertial Sensors ◽  
Kinematic Model ◽  
Three Dimensional ◽  
Health Condition ◽  
Body Motion ◽  
Whole Body ◽  
Motion Capture System ◽  
Outdoor Sports ◽  
Motion Capture Systems

Motion capture systems play an important role in health-care and sport-training systems. In particular, there exists a great demand on a mobile motion capture system that enables people to monitor their health condition and to practice sport postures anywhere at any time. The motion capture systems with infrared or vision cameras, however, require a special setting, which hinders their application to a mobile system. In this paper, a mobile three-dimensional motion capture system is developed based on inertial sensors and smart shoes. Sensor signals are measured and processed by a mobile computer; thus, the proposed system enables the analysis and diagnosis of postures during outdoor sports, as well as indoor activities. The measured signals are transformed into quaternion to avoid the Gimbal lock effect. In order to improve the precision of the proposed motion capture system in an open and outdoor space, a frequency-adaptive sensor fusion method and a kinematic model are utilized to construct the whole body motion in real-time. The reference point is continuously updated by smart shoes that measure the ground reaction forces.

The adaptable amphibious wheel-legged robot

2018 ◽  
Vol 42 (3) ◽  
pp. 323-339
Author(s):  
Jicheng Liu ◽  
Jinshuai Yang ◽  
Binglu Yan ◽  
Zheng Liu
Keyword(s):  
Large Diameter ◽  
Kinematic Model ◽  
Three Dimensional ◽  
Legged Robot ◽  
Loop Control ◽  
Walking Gait ◽  
Closed Loop Control System ◽  
Loop Control System ◽  
Amphibious Robot ◽  
Foot Trajectory

A new category of large-diameter adaptable amphibious wheel-legged robot is proposed in this paper. The proposed mechanism can climb obstacles better than existing designs. The Denavit–Hartenberg (D–H) coordinate system is used for kinematic analysis, and the constructed kinematic model is used to solve for these joint variables for a redundant robot. The control strategy is to plan both the foot trajectory of the amphibious robot, to optimize the operational performance in special environments, as well as the walking gait. Then the closed-loop control system is used. A simulation is used to verify the usefulness of the planned foot trajectory and walking gait for an entire running cycle, and a circuit is designed to solve a communication problem between the Arduino and the AX-12 servo. Finally, the foot trajectory of a single robot leg is captured by a three-dimensional motion-capture system to verify the rationality of the foot trajectory and walking gait.

Radula-centric and odontophore-centric kinematic models of swallowing inAplysia californica

2002 ◽  
Vol 205 (14) ◽  
pp. 2029-2051 ◽  
Author(s):  
Richard F. Drushel ◽  
Greg P. Sutton ◽  
David M. Neustadter ◽  
Elizabeth V. Mangan ◽  
Benjamin W. Adams ◽  
...  
Keyword(s):  
Kinematic Model ◽  
Three Dimensional ◽  
Rigid Bodies ◽  
High Temporal Resolution ◽  
Buccal Mass ◽  
Kinematic Models ◽  
Dimensional Shape ◽  
Position Parameter ◽  
Three Dimensional Shape

SUMMARYTwo kinematic models of the radula/odontophore of the marine mollusc Aplysia californica were created to characterize the movement of structures inside the buccal mass during the feeding cycle in vivo. Both models produce a continuous range of three-dimensional shape changes in the radula/odontophore, but they are fundamentally different in construction. The radulacentric model treats the radular halves as rigid bodies that can pitch, yaw and roll relative to a fixed radular stalk, thus creating a three-dimensional shape. The odontophore-centric model creates a globally convex solid representation of the radula/odontophore directly, which then constrains the positions and shapes of internal structures. Both radula/odontophore models are placed into a pre-existing kinematic model of the I1/I3 and I2 muscles to generate three-dimensional representations of the entire buccal mass. High-temporal-resolution, mid-sagittal magnetic resonance(MR) images of swallowing adults in vivo are used to provide non-invasive, artifact-free shape and position parameter inputs for the models. These images allow structures inside the buccal mass to be visualized directly, including the radula, radular stalk and lumen of the I1/I3 cavity. Both radula-centric and odontophore-centric models were able to reproduce two-dimensional, mid-sagittal radula/odontophore and buccal mass kinematics,but the odontophore-centric model's predictions of I1/I3, I2 and I7 muscle dimensions more accurately matched data from MR-imaged adults and transilluminated juveniles.

The three-dimensional stable mandibular landmarks in patients between the ages of 12.5 to 17.1 years

2020 ◽  
Author(s):  
Gui Chen ◽  
Mona Al Awadi ◽  
David William Chambers ◽  
Manuel O Lagravère-Vich ◽  
Tianmin Xu ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Growth Period ◽  
Mandibular Canal ◽  
Mental Foramen ◽  
Three Dimensions ◽  
Head Orientation ◽  
Facial Growth ◽  
Linear Distance ◽  
The Right ◽  
Stable Structures

Abstract Background: With the aid of implants, Björk identified the two-dimensional mandibular stable structures in cephalogram during facial growth. However, we don't know the three-dimensional stable structures exactly. The purpose of this study was to identify the most stable mandibular landmarks in growing patients using three-dimensional images.Methods: The sample was comprised of two cone-beam computed tomography (CBCT) scans taken about 4.6 years apart in 20 growing patients between the ages of 12.5 (T1) to 17.1 years (T2). After head orientation, landmarks were located on the chin (Pog), internal symphysis (Points C, D and E), and mandibular canals, which included the mental foramina (MF and MFA) and mandibular foramina (MdF). The linear distance change between Point C and these landmarks was measured on each CBCT to test stability through time. The reliability of the suggested stable landmarks was also evaluated. Results: The total distance changes between Point C and points D, E, Pog, MF, and MFA were all less than 1.0 mm from T1 to T2. The reliability measures of these landmarks, which were measured by the Cronbach alpha, were above 0.94 in all three dimensions for each landmark. From T1 to T2, distance changes from Point C to the right and left mandibular foramina were respectively 3.39±3.29 mm and 3.03±2.83 mm. Conclusions: During a growth period that averaged 4.6-years, ranging from 11.2 to 19.8 years, the structures that appeared relatively stable and could be used in mandibular regional superimposition included Pog, landmarks on the inferior part of the internal symphysis, and the mental foramen. The centers of the mandibular foramina, the starting points of the mandibular canal, underwent significant changes in the transverse and sagittal dimensions.

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