A Novel Two-Layer and Two-Loop Deployable Linkage With Accurate Vertical Straight-Line Motion

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Wen-ao Cao ◽  
De Zhang ◽  
Huafeng Ding
Keyword(s):  
Screw Theory ◽  
Kinematic Model ◽  
Degree Of Freedom ◽  
Kinematics Model ◽  
Vertical Straight Line ◽  
Straight Line ◽  
Structure Decomposition

Abstract This paper presents a novel two-layer and two-loop spatial deployable linkage which can only accurately output vertical straight-line motion. First, the degree-of-freedom (DOF) of the linkage is analyzed based on structure decomposition and screw theory, and the characteristic of the straight-line motion of the linkage is verified by checking the output twist of the end platform. Then, the kinematic model of the mechanism is established based on the conditions of the straight-line motion and the single DOF. Finally, several potentially typical applications of the linkage are exhibited. The straight-line linkage has relatively simple joint layouts and kinematics model and can be used as a deployable unit to construct some special deployable mechanisms.

Design and kinematics of a novel double-ring truss deployable antenna mechanism

2021 ◽  
pp. 1-14
Author(s):  
Wen-ao Cao ◽  
Sheng Xi ◽  
Huafeng Ding ◽  
Ziming Chen
Keyword(s):  
Topological Structure ◽  
Screw Theory ◽  
Structural Characteristics ◽  
Kinematic Model ◽  
Structure Design ◽  
Structural Symmetry ◽  
Double Ring ◽  
Joint Axis ◽  
Structure Decomposition ◽  
Topological Scheme

Abstract This paper aims to present the topological structure design and kinematic analysis of a novel double-ring truss deployable satellite antenna mechanism. First, a new topological scheme and a new rectangular prism deployable linkage unit are proposed for constructing the kind of antenna mechanisms. Second, the degree-of-freedom (DOF) of the deployable unit and the antenna mechanism are analyzed based on structure decomposition and screw theory. Third, the kinematic model of the double-ring truss deployable antenna mechanism is established based on its structural characteristics. Finally, a typical numerical example is used to illustrate the effectiveness of the designed mechanism and the established kinematic model. The new double-ring truss deployable antenna mechanism consists of the units with the better structural symmetry, and has simpler joint axis layouts, comparing with the same type of most existing mechanisms.

Single-Vertex Multicrease Rigid Origami With Nonzero Thickness and Its Transformation Into Deployable Mechanisms

2017 ◽  
Vol 10 (1) ◽  
Author(s):  
Chenhan Guang ◽  
Yang Yang
Keyword(s):  
Computer Aided Design ◽  
Screw Theory ◽  
Kinematic Model ◽  
Degree Of Freedom ◽  
Single Vertex ◽  
Geometrical Characteristics ◽  
Computer Aided ◽  
Deployable Mechanism ◽  
Aided Design ◽  
Basic Configuration

The radial folding ratio of single-vertex multicrease rigid origami, from the folded configuration to the unfolded configuration, is satisfactory. In this study, we apply two approaches to add nonzero thickness for this kind of origami and identify different geometrical characteristics. Then, the model of the secondary folding origami, which can help to further decrease the folding ratio, is constructed. We apply the method of constraining the edges of the panels on prescribed planes to geometrically obtain the kinematic model. Based on the kinematic model and the screw theory, the nonzero thickness origami is transformed into the deployable mechanism with one degree-of-freedom (1DOF). Other similar mechanisms can be derived based on this basic configuration. The computer-aided design examples are presented to indicate the feasibility.

scholarly journals A New Method for Type Synthesis of 2R1T and 2T1R 3-DOF Redundant Actuated Parallel Mechanisms with Closed Loop Units

2020 ◽  
Vol 33 (1) ◽  
Author(s):  
Yongquan Li ◽  
Yang Zhang ◽  
Lijie Zhang
Keyword(s):  
Closed Loop ◽  
Screw Theory ◽  
Line Graph ◽  
Degree Of Freedom ◽  
Parallel Mechanisms ◽  
Type Synthesis ◽  
Allocation Criteria ◽  
Grassmann Line Geometry ◽  
Moving Platform ◽  
Atlas Method

Abstract The current type synthesis of the redundant actuated parallel mechanisms is adding active-actuated kinematic branches on the basis of the traditional parallel mechanisms, or using screw theory to perform multiple getting intersection and union to complete type synthesis. The number of redundant parallel mechanisms obtained by these two methods is limited. In this paper, based on Grassmann line geometry and Atlas method, a novel and effective method for type synthesis of redundant actuated parallel mechanisms (PMs) with closed-loop units is proposed. Firstly, the degree of freedom (DOF) and constraint line graph of the moving platform are determined successively, and redundant lines are added in constraint line graph to obtain the redundant constraint line graph and their equivalent line graph, and a branch constraint allocation scheme is formulated based on the allocation criteria. Secondly, a scheme is selected and redundant lines are added in the branch chains DOF graph to construct the redundant actuated branch chains with closed-loop units. Finally, the branch chains that meet the requirements of branch chains configuration criteria and F&C (degree of freedom & constraint) line graph are assembled. In this paper, two types of 2 rotational and 1 translational (2R1T) redundant actuated parallel mechanisms and one type of 2 translational and 1 rotational (2T1R) redundant actuated parallel mechanisms with few branches and closed-loop units were taken as examples, and 238, 92 and 15 new configurations were synthesized. All the mechanisms contain closed-loop units, and the mechanisms and the actuators both have good symmetry. Therefore, all the mechanisms have excellent comprehensive performance, in which the two rotational DOFs of the moving platform of 2R1T redundant actuated parallel mechanism can be independently controlled. The instantaneous analysis shows that all mechanisms are not instantaneous, which proves the feasibility and practicability of the method.

Dynamics of a Two-DOF Parallel Pointing Mechanism

2005 ◽  
Author(s):  
Alessandro Cammarata ◽  
Rosario Sinatra
Keyword(s):  
Numerical Simulation ◽  
Parallel Mechanism ◽  
Inverse Dynamics ◽  
Kinematic Model ◽  
Degree Of Freedom ◽  
Numerical Examples ◽  
Proposed Model ◽  
Dynamic Analyses ◽  
Moving Platform ◽  
Two Degree Of Freedom

This paper presents kinematic and dynamic analyses of a two-degree-of-freedom pointing parallel mechanism. The mechanism consists of a moving platform, connected to a fixed platform by two legs of type PUS (prismatic-universal-spherical). At first a simplified kinematic model of the pointing mechanism is introduced. Based on this proposed model, the dynamics equations of the system using the Natural Orthogonal Complement method are developed. Numerical examples of the inverse dynamics results are presented by numerical simulation.

Analysis of Five-Degree-of-Freedom Robot Arms

1983 ◽  
Vol 105 (1) ◽  
pp. 23-27 ◽  
Author(s):  
K. Sugimoto ◽  
J. Duffy
Keyword(s):  
Arc Welding ◽  
Degrees Of Freedom ◽  
Screw Theory ◽  
Industrial Robot ◽  
Degree Of Freedom ◽  
Numerical Example ◽  
Robot Arms ◽  
Special Cases ◽  
Computer Controlled ◽  
Five Axes

Many kinds of robot arms with five degrees of freedom are widely used in industry for arc welding, spray painting, assembling etc. It is necessary to be able to compute joint displacements when such devices are computer controlled. A solution to this problem is presented and the analysis is illustrated by a numerical example using the most common industrial robot with five axes. Further, special cases are discussed using screw theory.

Duration of Experienced Expansion and Contraction of a Circle

1975 ◽  
Vol 41 (2) ◽  
pp. 507-518 ◽  
Author(s):  
Kristian Holt-Hansen
Keyword(s):  
Full Length ◽  
Full Size ◽  
Vertical Straight Line ◽  
Straight Line

The stimulus was a white outline circle which for 60 msec. was projected onto a screen 2 m. from S. The diameter of the circle was 10 cm. and the circle line was approximately 1.5 mm. wide. Fixating the center of the circle Ss reported experiencing the circle as expanding from the point of fixation to full size and then contracting to the point of fixation. Ss' experiences fell in two classes. The durations of Ss' experience of expansion-contraction were measured in msec. Ss also participated in experiments in which they fixated the nethermost point of a 17-cm. vertical straight line which was 2 mm. wide. Ss experienced the line as lengthening from the point of fixation to full length and then shortening to the point of fixation. For a given S the durations of the experienced expansion-contraction of the circle and the experienced lengthening-shortening of the straight line were the same.

Analysis of Parasitic Motion in Compliant Mechanisms Using Eigenwrenches and Eigentwists

2018 ◽  
Author(s):  
Werner W. P. J. van de Sande ◽  
Just L. Herder
Keyword(s):  
Compliant Mechanisms ◽  
Screw Theory ◽  
Compliant Mechanism ◽  
Degree Of Freedom ◽  
Compliance Matrix ◽  
Parasitic Motion ◽  
Actual Degree ◽  
Motion Metrics ◽  
Mechanism Kinematic ◽  
Kinematic Information

Parasitic motion is undesired in precision mechanisms, it causes unwanted kinematics. These erroneous motions are especially apparent in compliant mechanisms. Usually an analysis of parasitic motion is only valid for one type of mechanism. Kinematic information is imbedded in the compliance matrix of any mechanism; an eigenscrew decomposition expresses this kinematic information as screws. It uses screw theory to identify the lines along which a force yields a parallel translation and a rotation yields a parallel moment. These lines are called eigenwrenches and eigentwists. Any other load on the compliant mechanism will lead to parasitic motion. This article introduces two parasitic motion metrics using eigenscrew decomposition: the parasitic resultant from an applied screw and the deviation of an actual degree of freedom from a desired degree of freedom. These metrics are applicable to all compliant mechanism and allow comparison between two compliant mechanisms. These metrics are applied to some common compliant mechanisms as an example.

Kinematic modeling and control of mobile robot for large-scale workpiece machining

2020 ◽  
pp. 095440542093370
Author(s):  
Bo Tao ◽  
Xingwei Zhao ◽  
Sijie Yan ◽  
Han Ding
Keyword(s):  
Mobile Robot ◽  
Large Scale ◽  
Screw Theory ◽  
Kinematic Model ◽  
Speed Control ◽  
Constant Speed ◽  
Mobile Platform ◽  
Robot Arm ◽  
Kinematic Modeling ◽  
Robotic Machining

Safety and reliability are significant in the sense of robotic machining for large-scale workpieces. In this article, a control scheme is proposed to ensure the safe motion of the mobile robot. Screw theory is used to analyze the motion of the mobile robot. The mobile platform with Mecanum wheels can be considered as a mechanism with four driven screws in series. An auxiliary reference position of the mobile platform is calculated based on the kinematic model, and the motion of the mobile platform and robot arm can be decoupled to handle its redundant degrees of freedom. Constant speed control is investigated to reduce the interaction force between the robot and platform. Experiments are conducted on the mobile robotic machining task for a large-scale wind turbine blade. The mobile robot moves steadily and smoothly owing to the constant speed control with an auxiliary target.

Stiffness-based trajectory planning of a 6-DOF cable-driven parallel manipulator

2016 ◽  
Vol 231 (21) ◽  
pp. 3999-4011 ◽  
Author(s):  
Wenjia Zhang ◽  
Weiwei Shang ◽  
Bin Zhang ◽  
Fei Zhang ◽  
Shuang Cong
Keyword(s):  
Velocity Profile ◽  
Trajectory Planning ◽  
Parallel Manipulator ◽  
Kinematic Model ◽  
Degree Of Freedom ◽  
Performance Indices ◽  
Curved Trajectories ◽  
Quintic Polynomial ◽  
Point To Point ◽  
Six Degree Of Freedom

The stiffness of the cable-driven parallel manipulator is usually poor because of the cable flexibility, and the existing methods on trajectory planning mainly take the minimum time and the optimal energy into account, not the stiffness. To solve it, the effects of different trajectories on stiffness are studied for a six degree-of-freedom cable-driven parallel manipulator, according to the kinematic model and the dynamic model. The condition number and the minimum eigenvalue of the dimensionally homogeneous stiffness matrix are selected as performance indices to analyze the stiffness changes during the motion. The simulation experiments are implemented on a six degree-of-freedom cable-driven parallel manipulator, to study the stiffness of three different trajectory planning approaches such as S-type velocity profile, quintic polynomial, and trigonometric function. The accelerations of different methods are analyzed, and the stiffness performances for the methods are compared after planning the point-to-point straight and the curved trajectories. The simulation results indicate that the quintic polynomial and S-type velocity profile have the optimal performance to keep the stiffness stable during the motion control and the travel time of the quintic polynomial can be optimized sufficiently while keeping stable.

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