The Design of a Chain of Spherical Stephenson Mechanisms for a Gearless Pitch-Roll Wrist

2004 ◽  
Author(s):  
S. Herna´ndez ◽  
S. P. Bai ◽  
J. Angeles
Keyword(s):  
Unmodeled Dynamics ◽  
Manufacturing Cost ◽  
Interference Avoidance ◽  
Dimensional Synthesis ◽  
Bevel Gears ◽  
Industrial Manipulators ◽  
Differential Mechanism ◽  
Gear Trains ◽  
Robot Performance ◽  
A Chain

Although bevel-gear wrists are widely used in industrial manipulators due to their simple kinematics and low manufacturing cost, their gear trains function under rolling and sliding, the latter bringing about noise and vibration. Sliding is inherent to the straight teeth of the bevel gears of these trains. Moreover, un-avoidable backlash introduces unmodeled dynamics, which mars robot performance. To alleviate these drawbacks, a gearless pitch-roll wrist is currently under design for low backlash and high stiffness. The wrist consists of spherical cam-rollers and spherical Stephenson linkages; two roller-carrying disks drive a combination of cams and Stephenson mechanisms rotating as a differential mechanism. In this paper, the design of the chain of spherical Stephenson mechanisms (SSMs) is introduced. The problem of the dimensional synthesis is addressed and interference avoidance is discussed. An embodiment of the concept is also included.

The Design of a Chain of Spherical Stephenson Mechanisms for a Gearless Robotic Pitch-Roll Wrist

2005 ◽  
Vol 128 (2) ◽  
pp. 422-429 ◽  
Author(s):  
S. Hernandez ◽  
S. Bai ◽  
J. Angeles
Keyword(s):  
Unmodeled Dynamics ◽  
Manufacturing Cost ◽  
Interference Avoidance ◽  
Dimensional Synthesis ◽  
Bevel Gears ◽  
Industrial Manipulators ◽  
Differential Mechanism ◽  
Gear Trains ◽  
Robot Performance ◽  
A Chain

Although bevel-gear robotic wrists are widely used in industrial manipulators due to their simple kinematics and low manufacturing cost, their gear trains function under rolling and sliding, the latter bringing about noise and vibration. Sliding is inherent to the straight teeth of the bevel gears of these trains. Moreover, unavoidable backlash introduces unmodeled dynamics, which mars robot performance. To alleviate these drawbacks, a gearless pitch-roll wrist is currently under development for low backlash and high stiffness. The wrist consists of spherical cam-rollers and spherical Stephenson linkages, besides two roller-carrying disks that drive a combination of cams and Stephenson mechanisms, the whole system rotating as a differential mechanism. The paper focuses on the design of the chain of spherical Stephenson mechanisms. The problem of the dimensional synthesis is addressed, and interference avoidance is discussed. An embodiment of the concept is also included.

Systematic Synthesis and Applications of Novel Multi-Degree-of-Freedom Differential Systems

1992 ◽  
Author(s):  
Sridhar Kota ◽  
Srinivas Bidare
Keyword(s):  
Degrees Of Freedom ◽  
Building Blocks ◽  
Degree Of Freedom ◽  
Differential Systems ◽  
Practical Applications ◽  
Epicyclic Gear ◽  
Differential Mechanism ◽  
Long Time ◽  
Gear Trains ◽  
Drive Systems

Abstract A two-degree-of-freedom differential system has been known for a long time and is widely used in automotive drive systems. Although higher degree-of-freedom differential systems have been developed in the past based on the well-known standard differential, the number of degrees-of-freedom has been severely restricted to 2n. Using a standard differential mechanism and simple epicyclic gear trains as differential building blocks, we have developed novel whiffletree-like differential systems that can provide n-degrees of freedom, where n is any integer greater than two. Symbolic notation for representing these novel differentials is also presented. This paper presents a systematic method of deriving multi-degree-of-freedom differential systems, a three and four output differential systems and some of their practical applications.

Influence of the Glassfiber Filaments Distribution on Quality and Performance of Hole Processing on Printboards

2019 ◽  
Vol 946 ◽  
pp. 223-227
Author(s):  
Aleksey N. Shulgin ◽  
Aleksandr A. Dyakonov ◽  
Anastasia E. Gorodkova
Keyword(s):  
Glass Fibers ◽  
Maximum Shear Stress ◽  
Base Material ◽  
Dielectric Materials ◽  
Basic Material ◽  
Manufacturing Cost ◽  
Base Materials ◽  
Material Choice ◽  
And Performance ◽  
A Chain

The description of the basic material for the printboards production is given, its basic physical properties are formulated, the features of machining are shown and the range of problems that arise in this case is determined. We specified common mistakes that could lead to mass marriage in the manufacture of printboard assemblies. The structure and composition of base materials for the production of clad dielectric materials are described in this paper. An equation for calculating the maximum shear stress for a composite material is given. It is shown that nesting and, as a consequence, an increased content of glass fibers through a chain of interrelated factors affects the quality and reliability of the printboard operation and the entire product as a whole. In addition, the dense laying of fibers increases the cutting tool wear significantly. The article provides the technique of the base material choice depending on the distribution structure of glassfiber filaments on which the labor productivity, the quality, the cutter power and the manufacturing cost of the printboards depends.

Kinematic Analysis and Dimensional Synthesis of a Meso-Gripper

2016 ◽  
Author(s):  
Guochao Bai ◽  
Xianwen Kong ◽  
James Millar Ritchie
Keyword(s):  
3D Printing ◽  
Kinematic Analysis ◽  
Size Range ◽  
Dimensional Synthesis ◽  
Mesoscopic Scale ◽  
Robotic Hands ◽  
Printing Technology ◽  
Digital Multimedia ◽  
3D Printing Technology ◽  
Differential Mechanism

In recent years, applications in industrial assemblies within a size range from 0.5mm to 100mm are increasing due to the large demands for digital multimedia products. Research on grippers or robotic hands within the mesoscopic scale of this range has not been well explored. This paper proposes a mesoscopic scale gripper (meso-gripper) which has two modes: passive adjusting mode and an angled precision gripping mode. The gripper adjusts its shape automatically according to the appropriate mode. This form of gripping and the associated mechanism are novel in their implementation and operation. The meso-gripper which has metamorphic characteristics is generated by integrating a remote center of motion (RCM) mechanism with a cross four-bar (CFB) linkage. The dimensional synthesis of the gripper is outlined for a specified task-based gripping followed by the analysis of the synthesizing mechanism. A differential mechanism is adopted to increase the flexibility of the meso-gripper. Prototype is fabricated and tested using 3D printing technology to verify the feasibility of the design.

Comparison of the Dynamics of Conventional and Worm-Gear Differentials

1989 ◽  
Vol 111 (4) ◽  
pp. 605-610 ◽  
Author(s):  
J. S. Freeman ◽  
S. A. Velinsky
Keyword(s):  
High Performance ◽  
Equations Of Motion ◽  
Worm Gear ◽  
Road Vehicles ◽  
Bevel Gears ◽  
Full Vehicle ◽  
Lagrange Formulation ◽  
Differential Mechanism ◽  
Interesting Behavior ◽  
Gear Differential

The differential mechanism has been used for many years and a variety of unique designs have been developed for particular applications. This paper investigates the performance of both the conventional bevel-gear differential and the worm-gear differential as used in vehicles. The worm-gear differential is a design in which the bevel gears of the conventional differential are replaced by worm gear/worm wheel pairs. The resultant differential exhibits some interesting behavior which has made this differential desirable for use in high performance and off-road vehicles. In this work, an Euler-Lagrange formulation of the equations of motion of the conventional and worm-gear differentials allows comparison of their respective behavior. Additionally, each differential is incorporated into a full vehicle model to observe their effects on gross vehicle response. The worm-gear differential is shown to exhibit the desirable characteristics of a limited-slip differential while maintaining the conventional differential’s ability to differentiate output shaft speeds at all power levels.

scholarly journals Kinematic Analysis of Spatial Geared Mechanisms

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Julie Penaud ◽  
Daniel Alazard ◽  
Alexandre Amiez
Keyword(s):  
Adjacency Matrix ◽  
Kinematic Analysis ◽  
Polar Coordinates ◽  
Constraint Matrix ◽  
New Approach ◽  
Bevel Gears ◽  
Gear Trains ◽  
Complex Coefficients ◽  
Two Degree Of Freedom ◽  
General Method

In this paper, a general method for kinematic analysis of complex gear mechanisms, including bevel gear trains and noncollinear input and output axes, is presented. This new approach is based on the nullspace of the kinematic constraint matrix computed from the mechanism graph or its adjacency matrix. The novelty is that the elements of the adjacency matrix are weighted with complex coefficients allowing bevel gears to be taken into account and the angular velocity of each link to be directly expressed using polar coordinates. This approach is illustrated on a two-degree-of-freedom car differential and applied to a helicopter main gear box. A MATLAB open source software was developed to implement this method.

scholarly journals Kinematic Precision of Gear Trains

1983 ◽  
Vol 105 (3) ◽  
pp. 317-326 ◽  
Author(s):  
F. L. Litvin ◽  
R. N. Goldrich ◽  
J. J. Coy ◽  
E. V. Zaretsky
Keyword(s):  
Gear Tooth ◽  
Contact Point ◽  
Approximate Methods ◽  
Gear Noise ◽  
Bevel Gears ◽  
Tooth Surfaces ◽  
Noise Measurements ◽  
Gear Trains ◽  
Helicopter Transmission ◽  
General Method

Kinematic precision is affected by errors which are the result of either intentional adjustments or accidental defects in manufacturing and assembly of gear trains. This paper explains a general method for the determination of kinematic precision of gear trains. The general method is based on the exact kinematic relations for the contact point motions of the gear tooth surfaces under the influence of errors. An approximate method is also explained. Example applications of the general and approximate methods are demonstrated for gear trains consisting of involute (spur and helical) gears, circular-arc (Wildhaber-Novikov) gears, and spiral-bevel gears. Gear noise measurements from a helicopter transmission are presented and discussed with relation to the kinematic precision theory.

scholarly journals Precision of Spiral-Bevel Gears

1983 ◽  
Vol 105 (3) ◽  
pp. 310-316 ◽  
Author(s):  
F. L. Litvin ◽  
R. N. Goldrich ◽  
J. J. Coy ◽  
E. V. Zaretsky
Keyword(s):  
Tooth Surface ◽  
Surface Geometry ◽  
Spiral Bevel Gears ◽  
Gear Teeth ◽  
Bevel Gears ◽  
Bearing Contact ◽  
Order Of Magnitude ◽  
Gear Trains ◽  
Spiral Bevel ◽  
Kinematic Errors

An analytical method was derived for determining the kinematic errors in spiral-bevel gear trains caused by the generation of nonconjugate surfaces, by axial displacements of the gear assembly, and by eccentricity of the assembled gears. Such errors are induced during manufacturing and assembly. Two mathematical models of spiral-bevel gears were included in the investigation. One model corresponded to the motion of the contact ellipse across the tooth surface (geometry I) and the other along the tooth surface (geometry II). The following results were obtained: 1) Kinematic errors induced by errors of manufacture may be minimized by applying special machine settings. The original error may be reduced by an order of magnitude. The procedure is most effective for geometry II gears. 2) When trying to adjust the bearing contact pattern between the gear teeth for geometry I gears, it is more desirable to shim the gear axially; for geometry II gears, shim the pinion axially. 3) The kinematic accuracy of spiral-bevel drives is most sensitive to eccentricities of the gear and less sensitive to eccentricities of the pinion. The pecision of mounting accuracy and manufacture is most crucial for the gear, and less so for the pinion.

Kinematic and Kinetostatic Synthesis of Planar Coupled Serial Chain Mechanisms

2002 ◽  
Vol 124 (2) ◽  
pp. 301-312 ◽  
Author(s):  
Venkat Krovi ◽  
G. K. Ananthasuresh ◽  
Vijay Kumar
Keyword(s):  
Degree Of Freedom ◽  
Dimensional Synthesis ◽  
Single Degree Of Freedom ◽  
End Effector ◽  
Solution Approach ◽  
Single Degree ◽  
Design Specifications ◽  
Serial Chain ◽  
Gear Trains ◽  
External Loads

Single Degree-of-freedom Coupled Serial Chain (SDCSC) mechanisms form a novel class of modular and compact mechanisms with a single degree-of-freedom, suitable for a number of manipulation tasks. Such SDCSC mechanisms take advantage of the hardware constraints between the articulations of a serial-chain linkage, created using gear-trains or belt/pulley drives, to guide the end-effector motions and forces. In this paper, we examine the dimensional synthesis of such SDCSC mechanisms to perform desired planar manipulation tasks, taking into account task specifications on both end-effector motions and forces. Our solution approach combines precision point synthesis with optimization to realize optimal mechanisms, which satisfy the design specifications exactly at the selected precision points and approximate them in the least-squares sense elsewhere along a specified trajectory. The designed mechanisms can guide a rigid body through several positions while supporting arbitrarily specified external loads. Furthermore, torsional springs are added at the joints to reduce the overall actuation requirements and to enhance the task performance. Examples from the kinematic and the kinetostatic synthesis of planar SDCSC mechanisms are presented to highlight the benefits.

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