Structural Kinematics of Partially-Parallel Robotic Mechanisms

1987 ◽  
Author(s):  
M. Gaber Mohamed
Keyword(s):  
Carrying Capacity ◽  
Kinematic Chain ◽  
Performance Criteria ◽  
Load Carrying Capacity ◽  
Parallel Mechanisms ◽  
Type Synthesis ◽  
Load Carrying ◽  
Parallel Kinematic ◽  
New Generation ◽  
Robotic Applications

Abstract This paper introduces a new generation of robotic mechanisms. Such mechanisms are intermediate between the familiar serial and the fully-parallel robotic mechanisms. They usually comprise several subassemblies that are serially connected to one another. Each subassembly is basically an over constrained fully parallel kinematic chain. Such mechanisms are called “Partially-Parallel Robotic Mechanisms.” A type synthesis of planar and spatial partially-parallel robotic mechanisms is performed. Several practical designs are then introduced and studied for future robotic applications. Several performance criteria of this type of mechanisms are discussed and compared with those of serial as well as fully-parallel robotic mechanisms. Partially-parallel mechanisms are superior than serial mechanisms in rigidity, strength precision positioning and load carrying capacity. Furthermore, they are relatively less complex and have larger range of motion than fully-parallel mechanisms.

Isotropic Analysis of Line Vector Forces and its Application in the Type Synthesis of Redundantly Actuated 3-DOF Translational Parallel Mechanisms

2016 ◽  
Author(s):  
Yundou Xu ◽  
Xin Zhou ◽  
Ling Lu ◽  
Jiantao Yao ◽  
Yongsheng Zhao
Keyword(s):  
Carrying Capacity ◽  
Kinematic Chain ◽  
Conical Surface ◽  
Load Carrying Capacity ◽  
Parallel Mechanisms ◽  
Type Synthesis ◽  
Active Joint ◽  
Isotropic Line ◽  
Load Carrying ◽  
Redundantly Actuated

The load-carrying capacity of a mechanism is closely related to its line vector force. This article presents a thorough isotropic analysis of line vector forces. The results show that the isotropic condition can be satisfied when the line vector forces are evenly distributed on a conical surface with a cone-top angle of 109.472 degrees. By combining the isotropic line vector forces, a method for the type synthesis of 3-DOF, redundantly actuated translational parallel mechanisms (PMs) is proposed, in which the arrangement of the active joints is taken into account in advance. Using this method, a kinematic chain with a twist system reciprocal to both the constraint and actuation wrenches is constructed firstly, and then the active joint reciprocal to the constraint wrenches but not to the actuation wrench is constructed. Thus, a series of typical redundantly actuated PMs with isotropic actuation forces are obtained. Finally, the 4-PRRR PM is analyzed as an example, and the results show that the isotropy of the load-carrying capacity can always be satisfied during its movement.

Pavement Damage Due to Conventional and New Generation of Wide-Base Super Single Tires

2005 ◽  
Vol 33 (4) ◽  
pp. 210-226 ◽  
Author(s):  
I. L. Al-Qadi ◽  
M. A. Elseifi ◽  
P. J. Yoo ◽  
I. Janajreh
Keyword(s):  
Carrying Capacity ◽  
Material Properties ◽  
Three Dimensional ◽  
Fe Analysis ◽  
Load Carrying Capacity ◽  
Inflation Pressure ◽  
3D Finite Element ◽  
Load Carrying ◽  
Pavement Damage ◽  
New Generation

Abstract The objective of this study was to quantify pavement damage due to a conventional (385/65R22.5) and a new generation of wide-base (445/50R22.5) tires using three-dimensional (3D) finite element (FE) analysis. The investigated new generation of wide-base tires has wider treads and greater load-carrying capacity than the conventional wide-base tire. In addition, the contact patch is less sensitive to loading and is especially designed to operate at 690kPa inflation pressure at 121km/hr speed for full load of 151kN tandem axle. The developed FE models simulated the tread sizes and applicable contact pressure for each tread and utilized laboratory-measured pavement material properties. In addition, the models were calibrated and properly validated using field-measured stresses and strains. Comparison was established between the two wide-base tire types and the dual-tire assembly. Results indicated that the 445/50R22.5 wide-base tire would cause more fatigue damage, approximately the same rutting damage and less surface-initiated top-down cracking than the conventional dual-tire assembly. On the other hand, the conventional 385/65R22.5 wide-base tire, which was introduced more than two decades ago, caused the most damage.

Shape Optimization of Robotic Manipulators for Maximum Stiffness and Load Carrying Capacity

1989 ◽  
Author(s):  
S. Lamancusa ◽  
D. A. Saravanos ◽  
H. J. Sommer
Keyword(s):  
Carrying Capacity ◽  
Robotic Manipulators ◽  
Performance Criteria ◽  
Geometrical Shape ◽  
Load Carrying Capacity ◽  
Robotic Arms ◽  
Specific Strength ◽  
Specific Stiffness ◽  
Maximum Stiffness ◽  
Load Carrying

Abstract Structural optimization can result in robotic arms with significantly improved stiffness and load carrying capacity. The geometrical shape of the manipulator links can be optimized for maximum stiffness-to-weight and strength-to-weight ratios. The problem of stiffening and strengthening a manipulator is solved by optimal redistribution of the available material without increasing the total mass of the manipulator. Since manipulators are programmed to move through a range of postures, thereby creating different loading conditions on the links, a multi-posture design criteria is implemented to provide a more uniform stiffness and strength over the range of possible postures. Finite element based performance criteria are developed which facilitate the simultaneous maximization of specific stiffness and strength. Three application examples on a SCARA class arm illustrate the dramatic potential for simultaneous improvements in specific stiffness and specific strength. The significance of multiple postures on the optimal design, the merits of tapered versus straight link shapes, and the relation of maximum stiffness to maximum strength, are also examined.

scholarly journals Analysis of Gear Wheel-shaft Joint Characterized by Comparable Pitch Diameter and Mounting Diameter

10.14311/472 ◽  
2003 ◽  
Vol 43 (5) ◽  
Author(s):  
J. Ryś ◽  
H. Sanecki ◽  
A. Trojnacki
Keyword(s):  
Carrying Capacity ◽  
Small Difference ◽  
Design Procedure ◽  
Gear Wheel ◽  
Combined Loading ◽  
Strength Analysis ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Load Intensity ◽  
New Generation

This paper presents the design procedure for a gear wheel-shaft direct frictional joint. The small difference between the operating pitch diameter of the gear and the mounting diameter of the frictional joint is the key feature of the connection. The contact surface of the frictional joint must be placed outside the bottom land of the gear, and the geometry of the joint is limited to the specific type of solutions.The strength analysis is based on the relation between the torque and statistical load intensity of the gear transmission. Several dimensionless parameters are introduced to simplify the calculations. Stress-strain verifying analysis with respect to combined loading, the condition of appropriate load-carrying capacity of the frictional joint and the fatigue strength of the shaft are applied to obtain the relations between the dimensions of the joint and other parameters. The final engineering solution may then be suggested. The approach is illustrated by a numerical example.The proposed procedure can be useful in design projects for small, high-powered modern reducers and new-generation geared motors, in particular when manufactured in various series of types.

A Scale Dependent Simulation of Liquid Lubricated Textured Surfaces

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Robert L. Jackson
Keyword(s):  
Data Storage ◽  
Friction Force ◽  
Carrying Capacity ◽  
Scale Effects ◽  
Hydrodynamic Lubrication ◽  
Surface Texturing ◽  
Performance Criteria ◽  
Load Carrying Capacity ◽  
Textured Surfaces ◽  
Load Carrying

Over the past few years, the importance of nanoscale technology in industries, such as data storage, micro-electro-mechanical systems (MEMs), and conventional sliding and rolling element bearings, has increased significantly. This is due to increased performance criteria and emerging technologies at smaller scales. One way to increase tribological performance of such applications is through nanoscale surface texturing. These textures will allow for precise control of the performance of lubricated surfaces with very thin films. This work examines how the behavior of the lubricant changes as the geometry of the texture is decreased toward the nanoscale. This work uses existing scale dependent lubrication theories to model the hydrodynamic lubrication of textured surfaces in attempt to predict how nanoscale textures will perform. The theoretical results show that the scale effects of a lubricant between textured surfaces can decrease the load carrying capacity while also decreasing the friction force. Overall, the friction force decreases more than the load carrying capacity and so the effective friction coefficient is decreased. It should be noted that relative to larger scale textured surfaces, the load support can also decrease with the decreasing scale of the texture.

Modeling and Applications of a Family of Five-Degree-of-Freedom Parallel Mechanisms With Kinematic and Actuation Redundancy

2018 ◽  
Vol 10 (5) ◽  
Author(s):  
Long Kang ◽  
Wheekuk Kim ◽  
Byung-Ju Yi
Keyword(s):  
Carrying Capacity ◽  
Screw Theory ◽  
Degree Of Freedom ◽  
Load Carrying Capacity ◽  
Parallel Mechanisms ◽  
Actuation Redundancy ◽  
Moving Platforms ◽  
Load Carrying ◽  
Dynamic Simulator ◽  
Schönflies Motion

This paper introduces a family of statically balanced five-degree-of-freedom (5DOF) parallel mechanisms (PMs) with kinematic and actuation redundancy. Moving platforms of this family of PMs can provide 4DOF Schönflies motion. Three applications are considered in this work. The first and second applications use kinematic redundancy to avoid parallel singularities and perform an auxiliary grasping task in sequence. The third application incorporates actuation redundancy into a kinematically redundant manipulator to increase the load-carrying capacity. Screw theory was used to derive the Jacobian of the 5DOF PM with kinematic and actuation redundancy. Parallel singularities can be completely alleviated by controlling the orientation of the redundant link, thereby obtaining a large rotational workspace, and actuation redundancy increases the load-carrying capacity. Using a commercially available multibody dynamic simulator, an example of trajectory was performed to illustrate the large rotational workspace of the first and second applications and compare the Euclidean norm of the vector of actuation torque of nonredundant and redundant PMs. Three prototypes were also developed to demonstrate the output motion and static balancing property.

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