OPTIMAL SYNTHESIS OF CRANK-ROCKER LINKAGES FOR CONTINUOUS PATH GENERATION USING ORIENTATIONAL STRUCTURAL ERROR OF THE FIXED LINK

2000 ◽  
Vol 36 (05) ◽  
pp. 42 ◽  
Author(s):  
Hong Zhou
Keyword(s):  
Optimal Synthesis ◽  
Path Generation ◽  
Continuous Path ◽  
Structural Error

Optimal Synthesis of Adjustable Linkages for Precise Continuous Path Generation Using the Optimal Link Length Adjustment

2008 ◽  
Author(s):  
Hong Zhou ◽  
Mohammed Jamal ◽  
Arif Mohammed
Keyword(s):  
Genetic Algorithm ◽  
Penalty Method ◽  
Optimal Solution ◽  
Optimal Synthesis ◽  
Path Generation ◽  
Continuous Path ◽  
Link Length ◽  
Global Optimal Solution ◽  
Global Optimal ◽  
Synthesis Approach

Conventional nonadjustable four-bar linkages can only generate the desired continuous paths approximately. With one link length adjustment, the whole desired continuous path can be generated precisely. In this paper, the length of the driven side link or coupler is adjusted to generate the desired continuous paths precisely. The linkage feasibility conditions and path generation flexibilities of the adjustable four-bar linkages are analyzed. The optimal synthesis model of adjustable four-bar linkages is established based on the required optimal link length adjustment when the desired continuous path is precisely generated. The global optimal solution is searched by a real-valued genetic algorithm in which the involved constraints are handled using the function penalty method. The effectiveness of the optimal synthesis approach proposed in the paper is verified by the demonstrated examples.

Synthesis and Balancing of Cam-Modulated Linkages

1987 ◽  
Author(s):  
P. Pracht ◽  
P. Minotti ◽  
M. Dahan
Keyword(s):  
Systematic Approach ◽  
Kinematic Chain ◽  
Path Generation ◽  
Industrial Manipulator ◽  
High Speeds ◽  
Structural Error ◽  
Mass Balancing ◽  
Four Bar Linkage ◽  
Robotic Applications ◽  
Class Of Functions

Abstract Linkages are inherently light, inexpensive, strong, adaptable to high speeds and have little friction. Moreover the class of functions suitable for linkage representation is large. For all these reasons numerous recent works deal with the problem of design mechanisms for robotic applications, but very often in terms of components such as gripper, transmission, balancing. We investigate a new application for linkages, using them to design industrial manipulator. The selected mechanism for this application is a four bar linkage with an adjustable lengh for exact path generation. This adjustment is performed by a track or cam which is substituted to a bar. By this mean, we define a cam-modulated linkage which possess superior accuracy potential and is capable of accomodating of industrial design restrictions. Such a kinematic chain is free from structural error for path generation and the presence of the track introduces the flexibility and versality in the usefull four bar chain. The synthesis technique of cam modulated linkage utilizes loop closure equations, envelop theory to find the centerline and the profile of the track. These techniques provide a systematic approach to the design of mechanism for path generation when extreme accuracy is required. In order to complete an contribution, we take in consideration the static balancing of the synthesized manipulator. To achieve static mass balancing we use the potential energy storage capabilities of linear springs, and integrated it with the non-linear motion of mechanism to provide an exact value of the desired counter loading functions. Examples are worked to demonstrate applications of these procedures and to illustrate the industrial potential of spring balancing and cam-modulated linkage.

Eliminating Structural Error in Real-Time Adjustable Four-Bar Path Generators Using Iterative Learning Control

2004 ◽  
Author(s):  
Hong-Jen Chen ◽  
Richard W. Longman ◽  
Meng-Sang Chew
Keyword(s):  
Control Systems ◽  
Real Time ◽  
Iterative Learning Control ◽  
Learning Control ◽  
Iterative Learning ◽  
Path Generation ◽  
Structural Error ◽  
Four Bar Linkage

Fundamental concepts of Iterative Learning Control (ILC) are applied to path generating problems in mechanisms. As an illustration to such class of problems, an adjustable four-bar linkage is used. The coupler point of a four-bar traces a coupler curve that will in general deviate from the desired coupler path. Except at the precision points, the coupler curve will exhibit some structural error, which is the deviation from the specified curve. The structural error will repeat itself every cycle at exactly the same points over the range of interest. Since ILC is a methodology that was developed to handle similar repetitive errors in control systems, it is believed that it will be well served to apply it to this class of problems. Results show that ILC can be simple to implement, and it is found to be very well suited for such path generation problems.

An Elitist Ants-Search Based Method for Optimum Synthesis of Rigid-Linkage Mechanisms

2015 ◽  
Author(s):  
Nadim Diab ◽  
Ahmad Smaili
Keyword(s):  
Objective Function ◽  
Linear Constraints ◽  
Optimization Techniques ◽  
Path Generation ◽  
Generation Task ◽  
Optimum Synthesis ◽  
Structural Error ◽  
Constant Quantity ◽  
Future Work ◽  
Exploration Exploitation

Mechanical linkages are widely used in the industry and the synthesis of such mechanisms may require optimization depending on the number of precision positions required. Many intelligent optimization techniques (Genetic, Tabu, Simulated Annealing, etc) have been proposed in the literature, one of them being the Ant-Search which was first proposed by the authors in 2007. In this paper, a Modified Ant-Search (MAS) technique is proposed to optimize the synthesis of a four-bar mechanism with a path generation task. Two major improvements are applied over the previous algorithm: ants pheromone update and exploration/exploitation techniques are both modified. Unlike the previous work where a constant quantity of pheromones was added during each iteration, in this paper, the pheromone deposit rate is proportional to the error of the objective function. Such a modification in the pheromone update rule is expected to differentiate between the behaviors of different ants and better govern their motion in the subsequent iterations. Moreover, the second major improvement targets the exploration/exploitation techniques followed by the ants. Unlike the previous work where exploration dominates during the early iteration stages and exploitation during the late ones, this work implements a more dynamic strategy where ants enter and leave the exploration/exploitation processes as governed by parameters related to the objective function error and pheromone deposit levels. Such modifications applied to the Ant-Search (AS) technique are expected to ensure a better chance of converging to a global minimum. The MAS technique is applied for a few path generation tasks with prescribed timing along with a set of linear constraints. Results are compared with previous work in the literature where the newly proposed technique showed appreciable improvement as evaluated by the structural error objective function. Future work possibilities are also introduced.

Continuous Path Generation with Precise Control of Velocity and Orientation for Industrial Robots

CIRP Annals ◽  
1985 ◽  
Vol 34 (1) ◽  
pp. 511-514 ◽  
Author(s):  
Y. Mizugaki ◽  
H. Hiraoka ◽  
F. Kimura ◽  
T. Sata
Keyword(s):  
Industrial Robots ◽  
Path Generation ◽  
Continuous Path ◽  
Precise Control

Pareto optimal synthesis of four-bar mechanisms for path generation

2009 ◽  
Vol 44 (1) ◽  
pp. 180-191 ◽  
Author(s):  
N. Nariman-Zadeh ◽  
M. Felezi ◽  
A. Jamali ◽  
M. Ganji
Keyword(s):  
Optimal Synthesis ◽  
Pareto Optimal ◽  
Path Generation

Optimal Synthesis of Mechanisms for Path Generation Using Fourier Descriptors and Global Search Methods

1997 ◽  
Vol 119 (4) ◽  
pp. 504-510 ◽  
Author(s):  
Irfan Ullah ◽  
Sridhar Kota
Keyword(s):  
Objective Function ◽  
Design Space ◽  
Initial Guess ◽  
Global Search ◽  
Search Method ◽  
Fourier Descriptors ◽  
Path Generation ◽  
Local Optima ◽  
Structural Error ◽  
Synthesis Of Mechanisms

Generally, success in synthesis of mechanisms for path generation is limited to finding a reasonable local optima at best in spite of a very good initial guess. The most widely used Structural Error objective function is not effective in leading to practical solutions as it misrepresents the nature of the design problem by requiring the shape, size, orientation and position of the coupler curve to be optimized all at once. In this paper, we present an effective objective function based on Fourier descriptors that evaluates only the shape differences between two curves. This function is first minimized using a stochastic global search method derived from simulated annealing followed by Powell’s method. The size, orientation and position of the desired curve are addressed in a later stage by determining analogous points on the desired and candidate curves. In spite of highly non-linear mechanisms design space, our method discovers near-global and practical solutions consistently without requiring any initial guess.

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