A Spatial Eight-Bar Linkage and Its Association With the Deployable Platonic Mechanisms

2014 ◽  
Vol 6 (2) ◽  
Author(s):  
Guowu Wei ◽  
Jian S. Dai
Keyword(s):  
Closed Form ◽  
Degrees Of Freedom ◽  
Structure Parameters ◽  
Reciprocating Motion ◽  
Motion Feature ◽  
Plane Symmetric ◽  
Dual Plane ◽  
Straight Line ◽  
First Time ◽  
Geometry And Kinematics

This paper presents for the first time a novel two degrees of freedom (2-DOF) single-looped dual-plane-symmetric spatial eight-bar linkage with exact straight-line motion. Geometry and kinematics of the eight-bar linkage are investigated and closed-form equations are presented revealing the exact straight-line motion feature of the linkage on the condition that two symmetric inputs are given. In order to secure two symmetric inputs, a geared eight-bar linkage is then proposed converting the linkage into a 1-DOF linkage of exact straight-line motion. The direction of the straight-line motion produced by the proposed eight-bar linkage is changeable and is only dependent on the structure parameters of the two pairs of V-shaped R-R dyads of the linkage. Further, the proposed eight-bar linkage is applied to the synthesis and construction of a group of deployable Platonic mechanisms with radially reciprocating motion. The virtual-center-based (VCB) method is presented for the synthesis and prototypes of the deployable Platonic mechanisms are fabricated verifying the mobility and motion of the proposed mechanisms.

Synthesis, Mobility, and Multifurcation of Deployable Polyhedral Mechanisms With Radially Reciprocating Motion

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Guowu Wei ◽  
Yao Chen ◽  
Jian S. Dai
Keyword(s):  
Geometric Constraints ◽  
Reciprocating Motion ◽  
Single Plane ◽  
Plane Symmetric ◽  
Loop Equation ◽  
Dual Plane ◽  
Potential Applications ◽  
Number Synthesis ◽  
First Time ◽  
Geometry And Kinematics

Extending the method coined virtual-center-based (VCB) for synthesizing a group of deployable platonic mechanisms with radially reciprocating motion by implanting dual-plane-symmetric 8-bar linkages into the platonic polyhedron bases, this paper proposes for the first time a more general single-plane-symmetric 8-bar linkage and applies it together with the dual-plane-symmetric 8-bar linkage to the synthesis of a family of one-degree of freedom (DOF) highly overconstrained deployable polyhedral mechanisms (DPMs) with radially reciprocating motion. The two 8-bar linkages are compared, and geometry and kinematics of the single-plane-symmetric 8-bar linkage are investigated providing geometric constraints for synthesizing the DPMs. Based on synthesis of the regular DPMs, synthesis of semiregular and Johnson DPMs is implemented, which is illustrated by the synthesis and construction of a deployable rectangular prismatic mechanism and a truncated icosahedral (C60) mechanism. Geometric parameters and number synthesis of typical semiregular and Johnson DPMs based on the Archimedean polyhedrons, prisms and Johnson polyhedrons are presented. Further, movability of the mechanisms is evaluated using symmetry-extended rule, and mobility of the mechanisms is verified with screw-loop equation method; in addition, degree of overconstraint of the mechanisms is investigated by combining the Euler's formula for polyhedrons and the Grübler–Kutzbach formula for mobility analysis of linkages. Ultimately, singular configurations of the mechanisms are revealed and multifurcation of the DPMs is identified. The paper hence presents an intuitive and efficient approach for synthesizing PDMs that have great potential applications in the fields of architecture, manufacturing, robotics, space exploration, and molecule research.

Geometry and Kinematics of a Plane-Symmetric Spatial Eight-Bar Linkage With Exact Straight-Line Motion

2011 ◽  
Author(s):  
Guowu Wei ◽  
Jian S. Dai
Keyword(s):  
Isosceles Triangle ◽  
Plane Symmetric ◽  
Straight Line ◽  
Translation Motion ◽  
Motion Characteristics ◽  
First Time ◽  
The Relationship ◽  
Special Case ◽  
Kinematic Properties ◽  
Geometry And Kinematics

In this paper, a novel plane-symmetric spatial eight-bar linkage with exact straight-line motion is proposed for the first time. Geometry and kinematics of the eight-bar linkage are studied and closed-form equations are presented revealing the exact straight-line motion characteristics of the linkage. It is found in this paper that, for the plane-symmetric eight-bar linkage, the angle α between the base and the straight-line traced by the trajectory of the end-effector point is only dependent on the angle φ of the isosceles triangle vertexes of the linkage but independent of the length of the links and dimension of the vertexes. The relationship between α and φ is studied and a special case that leads to parallel translation motion is revealed. Numerical example is then given to illustrate the kinematic properties of the eight-bar linkage.

scholarly journals Branch Reconfiguration of Bricard Linkages Based on Toroids Intersections: Plane-Symmetric Case

2018 ◽  
Vol 10 (3) ◽  
Author(s):  
P. C. López-Custodio ◽  
J. S. Dai ◽  
J. M. Rico
Keyword(s):  
Degrees Of Freedom ◽  
Symmetric Case ◽  
Complete Theory ◽  
Plane Symmetry ◽  
Special Configuration ◽  
Conical Singularities ◽  
Plane Symmetric ◽  
Isolated Points ◽  
First Time ◽  
Special Plane

This paper for the first time reveals a set of special plane-symmetric Bricard linkages with various branches of reconfiguration by means of intersection of two generating toroids, and presents a complete theory of the branch reconfiguration of the Bricard plane-symmetric linkages. An analysis of the intersection of these two toroids reveals the presence of coincident conical singularities, which lead to design of the plane-symmetric linkages that evolve to spherical 4R linkages. By examining the tangents to the curves of intersection at the conical singularities, it is found that the linkage can be reconfigured between the two possible branches of spherical 4R motion without disassembling it and without requiring the usual special configuration connecting the branches. The study of tangent intersections between concentric singular toroids also reveals the presence of isolated points in the intersection, which suggests that some linkages satisfying the Bricard plane-symmetry conditions are actually structures with zero finite degrees-of-freedom (DOF) but with higher instantaneous mobility. This paper is the second part of a paper published in parallel by the authors in which the method is applied to the line-symmetric case.

scholarly journals Additive Manufacturing for Effective Smart Structures: The Idea of 6D Printing

2021 ◽  
Vol 5 (5) ◽  
pp. 119
Author(s):  
Stelios K. Georgantzinos ◽  
Georgios I. Giannopoulos ◽  
Panteleimon A. Bakalis
Keyword(s):  
Additive Manufacturing ◽  
Degrees Of Freedom ◽  
Smart Structures ◽  
Interaction Mechanism ◽  
Modeling And Simulations ◽  
Environmental Stimulus ◽  
Material Component ◽  
Design And Manufacturing ◽  
First Time ◽  
Printing Techniques

This paper aims to establish six-dimensional (6D) printing as a new branch of additive manufacturing investigating its benefits, advantages as well as possible limitations concerning the design and manufacturing of effective smart structures. The concept of 6D printing, to the authors’ best knowledge, is introduced for the first time. The new method combines the four-dimensional (4D) and five-dimensional (5D) printing techniques. This means that the printing process is going to use five degrees of freedom for creating the final object while the final produced material component will be a smart/intelligent one (i.e., will be capable of changing its shape or properties due to its interaction with an environmental stimulus). A 6D printed structure can be stronger and more effective than a corresponding 4D printed structure, can be manufactured using less material, can perform movements by being exposed to an external stimulus through an interaction mechanism, and it may learn how to reconfigure itself suitably, based on predictions via mathematical modeling and simulations.

scholarly journals Thermos Array: Two-Dimensional Sparse Array with Reduced Mutual Coupling

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Lei Sun ◽  
Minglei Yang ◽  
Baixiao Chen
Keyword(s):  
Closed Form ◽  
Degrees Of Freedom ◽  
Mutual Coupling ◽  
Doa Estimation ◽  
Two Dimensional ◽  
Spatial Smoothing ◽  
Planar Arrays ◽  
Half Wavelength ◽  
Planar Array ◽  
Small Spacing

Sparse planar arrays, such as the billboard array, the open box array, and the two-dimensional nested array, have drawn lots of interest owing to their ability of two-dimensional angle estimation. Unfortunately, these arrays often suffer from mutual-coupling problems due to the large number of sensor pairs with small spacing d (usually equal to a half wavelength), which will degrade the performance of direction of arrival (DOA) estimation. Recently, the two-dimensional half-open box array and the hourglass array are proposed to reduce the mutual coupling. But both of them still have many sensor pairs with small spacing d, which implies that the reduction of mutual coupling is still limited. In this paper, we propose a new sparse planar array which has fewer number of sensor pairs with small spacing d. It is named as the thermos array because its shape seems like a thermos. Although the resulting difference coarray (DCA) of the thermos array is not hole-free, a large filled rectangular part in the DCA can be facilitated to perform spatial-smoothing-based DOA estimation. Moreover, it enjoys closed-form expressions for the sensor locations and the number of available degrees of freedom. Simulations show that the thermos array can achieve better DOA estimation performance than the hourglass array in the presence of mutual coupling, which indicates that our thermos array is more robust to the mutual-coupling array.

scholarly journals Huber-Based Robust Unscented Kalman Filter Distributed Drive Electric Vehicle State Observation

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 750
Author(s):  
Wenkang Wan ◽  
Jingan Feng ◽  
Bao Song ◽  
Xinxin Li
Keyword(s):  
Kalman Filter ◽  
Real Time ◽  
Degrees Of Freedom ◽  
Unscented Kalman Filter ◽  
State Parameter ◽  
State Observation ◽  
Straight Line ◽  
Distributed Drive Electric Vehicle ◽  
Huber Method ◽  
Yaw Moment

Accurate and real-time acquisition of vehicle state parameters is key to improving the performance of vehicle control systems. To improve the accuracy of state parameter estimation for distributed drive electric vehicles, an unscented Kalman filter (UKF) algorithm combined with the Huber method is proposed. In this paper, we introduce the nonlinear modified Dugoff tire model, build a nonlinear three-degrees-of-freedom time-varying parametric vehicle dynamics model, and extend the vehicle mass, the height of the center of gravity, and the yaw moment of inertia, which are significantly influenced by the driving state, into the vehicle state vector. The vehicle state parameter observer was designed using an unscented Kalman filter framework. The Huber cost function was introduced to correct the measured noise and state covariance in real-time to improve the robustness of the observer. The simulation verification of a double-lane change and straight-line driving conditions at constant speed was carried out using the Simulink/Carsim platform. The results show that observation using the Huber-based robust unscented Kalman filter (HRUKF) more realistically reflects the vehicle state in real-time, effectively suppresses the influence of abnormal error and noise, and obtains high observation accuracy.

scholarly journals Simple and Exact Closed-Form Expression for Determination of a Penetrated Ray Path in a Ray Tracing

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Hyun Wook Moon ◽  
Woojoong Kim ◽  
Sewoong Kwon ◽  
Jaeheung Kim ◽  
Young Joong Yoon
Keyword(s):  
Closed Form ◽  
Approximate Method ◽  
Ray Tracing ◽  
Conventional Method ◽  
Closed Form Expression ◽  
Indoor Environments ◽  
Straight Line ◽  
Ray Path ◽  
Ray Tracing Simulation

A simple and exact closed-form equation to determine a penetrated ray path in a ray tracing is proposed for an accurate channel prediction in indoor environments. Whereas the penetrated ray path in a conventional ray tracing is treated as a straight line without refraction, the proposed method is able to consider refraction through the wall in the penetrated ray path. Hence, it improves the accuracy in ray tracing simulation. To verify the validation of the proposed method, the simulated results of conventional method, approximate method, and proposed method are compared with the measured results. The comparison shows that the proposed method is in better agreement with the measured results than the conventional method and approximate method, especially in high frequency bands.

Free Vibration Analysis of Two-Stage Planetary Gear With Friction

2018 ◽  
Author(s):  
Wei Liu ◽  
Yunbo Yuan ◽  
Tao He ◽  
Donghua Wang
Keyword(s):  
Free Vibration ◽  
Degrees Of Freedom ◽  
Sliding Friction ◽  
Free Vibration Analysis ◽  
Planetary Gear ◽  
Two Stage ◽  
Second Stage ◽  
Torsional Coupling ◽  
Coupling Dynamic ◽  
First Time

Considering the effect of teeth surface sliding friction, free vibration of two-stage planetary gears (TPG) is studied theoretically for the first time. The lateral-torsional coupling dynamic model and equation are established with three degrees of freedom: two translations and one rotation. The change rule of natural frequency is discussed with the case of first stage planetary gear’s number 4 and second stage planetary gear’s number 3, 4 and 5. Afterwards three vibration modes are summarized by calculating the free vibration. In order to understand the behavior of friction, the effect of friction on natural frequencies is analyzed for the case of considering friction and not considering friction. Furthermore, the ‘self-coupling’ phenomenon is obtained from the vibration of center component of TPG Meanwhile, the ‘mutual coupling’ is obtained between the first-stage planetary gear (FPG) and the second-stage planetary gear (SPG).

Performance of a Short Multi-Grooved Capillary Compensated Hydrostatic Journal Bearing

1968 ◽  
Vol 183 (16) ◽  
pp. 107-115
Author(s):  
J. K. Patrick ◽  
N. N. S. Chen
Keyword(s):  
Journal Bearing ◽  
Load Capacity ◽  
Flow Characteristics ◽  
Lubricating Oil ◽  
Load Carrying Capacity ◽  
Straight Line ◽  
Load Carrying ◽  
Capillary Type ◽  
First Time ◽  
Oil Film Pressure

This paper presents the results of an extensive experimental investigation into the performance of a short multi-grooved bearing subjected to a range of static and alternating loads. Lubricating oil was supplied, at pressures of up to 2000 lb/in2, to capillary type restrictors connected to 10 closed-end axial grooves in the bearing. The bearing had a length/diameter ratio of 1/3 and operated with a journal speed and load frequency of 327 c/min. Measured load capacity, stiffness, and flow characteristics indicate that bearings of this type have a significant load-carrying capacity at zero journal speed and that the load capacity is increased by journal rotation. A feature of the journal behaviour under alternating loads is the movement of the journal centre along a straight line coincident with the load plane. The extensive oil film pressure surveys indicate for the first time the pressure distribution within narrow hydrostatic bearings and provide a basis for a realistic theoretical analysis of this type of bearing.

scholarly journals A Closed-Form Buckling Formula for Open-Coiled and Properly Supported Circular-Bar Helical Springs

2018 ◽  
Vol 68 (3) ◽  
pp. 33-48
Author(s):  
Yildirim Vebil
Keyword(s):  
Closed Form ◽  
Elementary Theory ◽  
Circular Section ◽  
Helical Springs ◽  
Helix Pitch ◽  
Wide Range ◽  
The Mean ◽  
Artificial Neural Network Ann ◽  
Circular Bar ◽  
First Time

AbstractAs a continuation of the author’s previous studies on the buckling analysis of helical springs, a closed-form formula having been obtained with the help of the artificial neural network (ANN) is proposed and discussed in detail for the first time for a cylindrical close/open-coiled helical spring with fixed ends and having a solid circular section. As far as the author knows there is no such a formula in the open-literature to consider the effects of all stress resultants (torsional and bending moments, axial and shearing forces), large helix pitch angles together with the axial and shear deformations on the buckled state. The present formula may be used in a wide range of the total number of active turns, the ratio of the free axial length to the mean helix diameter, and the spring index. It is yet again revealed that it is not appropriate to use the elementary theory to determine the critical buckling loads for open-coiled springs. The present formula may allow the deeper understanding of spring buckling mechanism and to be used directly and safely in the design processes of such closely/open-coiled springs.

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