scholarly journals An Alternative Method for Shaking Force Balancing of the 3RRR PPM through Acceleration Control of the Center of Mass

2020 ◽  
Vol 10 (4) ◽  
pp. 1351 ◽  
Author(s):  
Mario Acevedo ◽  
María T. Orvañanos-Guerrero ◽  
Ramiro Velázquez ◽  
Vigen Arakelian
Keyword(s):  
Center Of Mass ◽  
Substantial Reduction ◽  
Robotic Manipulators ◽  
Mass Redistribution ◽  
Planar Parallel Manipulator ◽  
Analytic Expressions ◽  
Common Center ◽  
The Common ◽  
Driving Torque ◽  
Shaking Moment

The problem of shaking force balancing of robotic manipulators, which allows the elimination or substantial reduction of the variable force transmitted to the fixed frame, has been traditionally solved by optimal mass redistribution of the moving links. The resulting configurations have been achieved by adding counterweights, by adding auxiliary structures or, by modifying the form of the links from the early design phase. This leads to an increase in the mass of the elements of the mechanism, which in turn leads to an increment of the torque transmitted to the base (the shaking moment) and of the driving torque. Thus, a balancing method that avoids the increment in mass is very desirable. In this article, the reduction of the shaking force of robotic manipulators is proposed by the optimal trajectory planning of the common center of mass of the system, which is carried out by “bang-bang” profile. This allows a considerable reduction in shaking forces without requiring counterweights, additional structures, or changes in form. The method, already presented in the literature, is resumed in this case using a direct and easy to automate modeling technique based on fully Cartesian coordinates. This permits to express the common center of mass, the shaking force, and the shaking moment of the manipulator as simple analytic expressions. The suggested modeling procedure and balancing technique are illustrated through the balancing of the 3RRR planar parallel manipulator (PPM). Results from computer simulations are reported.

scholarly journals Workspace Delineation of Cable-Actuated Parallel Manipulators

2004 ◽  
Author(s):  
Ethan Stump ◽  
Vijay Kumar
Keyword(s):  
Parallel Manipulator ◽  
Parallel Manipulators ◽  
Extensive Literature ◽  
Reachable Workspace ◽  
Planar Parallel Manipulator ◽  
Analytic Expressions

While there is extensive literature available on parallel manipulators in general, there has been much less attention given to cable-driven parallel manipulators. In this paper, we address the problem of analyzing the reachable workspace using the tools of semi-definite programming. We build on earlier work [1, 2] done using similar techniques by deriving limiting conditions that allow us to compute analytic expressions for the boundary of the reachable workspace. We illustrate this computation for a planar parallel manipulator with four actuators.

scholarly journals Balancing and Simulation of a Double Crank-Rocker Engine Model for Optimum Reduction of Shaking Forces and Shaking Moments

2021 ◽  
Vol 8 (2) ◽  
pp. 237-245
Author(s):  
Anwr M. Albaghdadi ◽  
Masri B. Baharom ◽  
Shaharin A. Sualiman
Keyword(s):  
Dynamic Analysis ◽  
Objective Function ◽  
Conventional Method ◽  
Optimization Process ◽  
New Model ◽  
Engine Model ◽  
Design Variables ◽  
Driving Torque ◽  
Related Design ◽  
Shaking Moment

In this paper, a new configuration of Crank-Rocker (CR) model has been proposed by duplicating its mechanism. The method has been implemented to overcome vibration problem on a single-piston Crank-Rocker engine caused by system unbalance. The new method suggests combining conventional method of adding counterweights to reduce shaking forces and eliminating the inertial moments on system by implementing the new layout. A dynamic study of the new model is presented, then the objective function is derived and implemented to perform the optimization process. Related design variables and system constraints are introduced to determine attached counterweights optimized characteristics. For results validation, the simulation, dynamic analysis, and optimization process were conducted using ADAMS VIEW® software. The output results were presented and discussed to verify the validity of the suggested method. It was noticed that the method was very effective and has managed to reduce the total shaking forces by about 91%, shaking moment by about 66%; and the driving torque by 27%.

Integrated Kinematic and Dynamic Optimal Synthesis of Spatial Mechanisms

1987 ◽  
Author(s):  
A. J. Kakatsios ◽  
S. J. Tricamo
Keyword(s):  
Nonlinear Programming ◽  
Simultaneous Optimization ◽  
Programming Formulation ◽  
Joint Torques ◽  
Spatial Mechanism ◽  
Spatial Mechanisms ◽  
Structural Error ◽  
Integrated Technique ◽  
Driving Torque ◽  
Shaking Moment

Abstract A novel integrated technique permitting the simultaneous optimization of kinematic and dynamic characteristics in the synthesis of spatial mechanisms is shown. The nonlinear programming formulation determines mechanism variables which simultaneously minimize the maximum values of bearing reactions, joint torques, driving torque, shaking moment, and shaking force while constraining the maximum kinematic structural error to a prescribed bound. The method is applied to the design of a path generating RRSS spatial mechanism with prescribed input link timing. Dynamic reactions in the mechanisms synthesized using the integrated technique were substantially reduced when compared to those of a mechanism synthesized to satisfy only the specified kinematic conditions.

Optimum Design of a Planar Robotic Manipulator

1996 ◽  
Author(s):  
D. F. Berner ◽  
J. A. Snyman
Keyword(s):  
Objective Function Value ◽  
Substantial Reduction ◽  
Weighted Average ◽  
Vertical Motion ◽  
Robotic Manipulators ◽  
Optimization Method ◽  
Constrained Problem ◽  
Design Variables ◽  
Function Formulation ◽  
Optimization Methodology

Abstract A general optimization methodology for the optimal design of robotic manipulators is presented and illustrated by its application to a realistic and practical three link re volute-joint planar manipulator. The end-effector carries out a prescribed vertical motion for which the weighted average torque requirement from electrical driving motors is minimized with respect to positional and dimensional design variables. In addition to simple physical bounds placed on the variables the maximum deliverable torques of the driving motors represent further constraints on the system. The optimization is carried out via a penalty function formulation of the constrained problem to which a proven robust unconstrained optimization method is applied. The problem of degeneracy or lock-up, which may occur for certain choices of design variables, is successfully dealt with by means of a specially proposed procedure in which a high artificial objective function value is computed for such “lock-up trajectories”. Designs are obtained that represent substantial reduction in torque requirement in comparison to that of arbitrarily chosen practical designs.

scholarly journals Comparison of turbulence in HII regions and molecular clouds

1991 ◽  
Vol 147 ◽  
pp. 476-479
Author(s):  
C. R. O'Dell
Keyword(s):  
Molecular Clouds ◽  
Center Of Mass ◽  
Hii Regions ◽  
Emission Lines ◽  
General Increase ◽  
Hii Region ◽  
Velocity Relation ◽  
Common Center ◽  
The One ◽  
Kolmogorov Theory

Both the HII Regions and the Molecular Clouds show broadening of their emission lines beyond that expected from thermal motion and this is ascribed to turbulence. Turbulence in molecular clouds generally agrees with a model where the velocity of motion is determined by the Alfv én velocity.Turbulence in Galactic HII Regions and Giant Extragalactic HII Regions can also be studied by the width of the emission lines. The magnitude of the turbulent velocities in these regions are characteristically about 10 km/s. There is a general increase in turbulent velocity with the size of the HII Region, and this relation is close to but different from the one third power dependence expected from the most naive application of Kolmogorov theory. When a detailed study is conducted of each Galactic HII Region by means of the structure function, one finds that there is not agreement with Kolmogorov theory.The Size-Turbulent versus Velocity relation for Galactic HII Regions differs slightly from the better defined velocity relation for Giant Extragalactic HII Regions. This difference is probably due to the fact that the larger extragalactic objects are probably complexes of multiple individual HII Regions. There is no evidence that broadening of extragalactic HII Regions is due to motion about a common center of mass.

Complete Shaking Force and Shaking Moment Balancing of Link Mechanisms Using Balancing Idler Loops

1982 ◽  
Vol 104 (2) ◽  
pp. 482-493 ◽  
Author(s):  
Cemil Bagci
Keyword(s):  
Angular Momentum ◽  
Total Angular Momentum ◽  
Center Of Mass ◽  
Numerical Example ◽  
Shaking Moment

A method for completely balancing the shaking forces and shaking moments in mechanisms is presented. The method introduces shaking moment balancing idler parallelogram loop (or loops) which transfers the motion of a coupler link to a shaft on the frame of the mechanism, where the rotary balancers balance the shaking moment. The complete balancing of a mechanism is accomplished by maintaining the total center of mass of the mechanism stationary meanwhile achieving that the total angular momentum of the moving links of the mechanism vanishes. Positioning of the idler loops is illustrated for a series of multiloop mechanisms. Theorems on the complete balancing of shaking forces and shaking moments in mechanisms are established. Design equations for completely balancing some single and multiloop mechanisms are given. A numerical example is included.

Robust Multibit Image Watermarking Based on Contrast Modulation and Affine Rectification

2019 ◽  
Vol 33 (14) ◽  
pp. 1954036
Author(s):  
Xin Zhong ◽  
Frank Y. Shih
Keyword(s):  
Image Processing ◽  
Lower Bound ◽  
State Of The Art ◽  
Image Watermarking ◽  
Center Of Mass ◽  
Experimental Results ◽  
Superior Performance ◽  
The Common ◽  
Distortion Parameters ◽  
Watermarking Scheme

In this paper, we present a robust multibit image watermarking scheme to undertake the common image-processing attacks as well as affine distortions. This scheme combines contrast modulation and effective synchronization for large payload and high robustness. We analyze the robustness, payload, and the lower bound of fidelity. Regarding watermark resynchronization under affine distortions, we develop a self-referencing rectification method to detect the distortion parameters for reconstruction by the center of mass in affine covariant regions. The effectiveness and advantages of the proposed scheme are confirmed by experimental results, which show the superior performance as comparing against several state-of-the-art watermarking methods.

An essay of Dr. John Wallis, exhibiting his hypothesis about the flux and reflux of the sea, taken from the consideration of the common center of gravity of the Earth and Moon

1665 ◽  
Vol 1 (16) ◽  
pp. 263-281 ◽  
Keyword(s):  
Center Of Gravity ◽  
The Earth ◽  
Common Center ◽  
The Common ◽  
John Wallis

How abstruse a subject in philosophy, the flux and reflux of the sea hath proved hitherto, and how much the same hath in all ages perplexed the minds even of the best of naturalists, when they have attempted to render an account of the cause thereof, is needless here to represent.

scholarly journals A General and Numerically Efficient Framework to Design Sector-Type and Cylindrical Counterweights for Balancing of Planar Linkages

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
B. Demeulenaere ◽  
M. Verschuure ◽  
J. Swevers ◽  
J. De Schutter
Keyword(s):  
Iterative Procedure ◽  
Numerical Experiments ◽  
Optimization Problems ◽  
Computation Time ◽  
Efficient Design ◽  
Convex Optimization Problems ◽  
Sector Type ◽  
Planar Linkages ◽  
Driving Torque ◽  
Shaking Moment

This paper extends previous work concerning convex reformulations of counterweight balancing by developing a general and numerically efficient design framework for counterweight balancing of arbitrarily complex planar linkages. At the numerical core of the framework is an iterative procedure, in which successively solving three convex optimization problems yields practical counterweight shapes in typically less than 1 CPU s. Several types of counterweights can be handled. The iterative procedure allows minimizing and/or constraining shaking force, shaking moment, driving torque, and bearing forces. Numerical experiments demonstrate the numerical superiority (in terms of computation time and balancing result) of the presented framework compared to existing approaches.

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