Patterned Bootstrap: A New Method That Gives Efficiency for Some Precision Position Synthesis Problems

2006 ◽  
Vol 129 (2) ◽  
pp. 173-183 ◽  
Author(s):  
Zhenjun Luo ◽  
Jian S. Dai

This paper presents a heuristic global convergence method, termed as patterned bootstrap (PB), for solving systems of equations. In the PB method, multiple directions starting from a given point are searched. A number of intermediate underdetermined systems are selected and solved sequentially using classic globally convergence methods. Numerical experiments demonstrate that the PB method outperforms Levenberg-Marquardt method on solving a number of challenging synthesis problems in no more than 18 variables. On the other hand, Levenberg-Marquardt method normally outperforms the PB method on solving several systems of equations in 30 variables which are derived from the five precision-position motion generation problem of spatial RRR manipulators. In the paper, tunneling functions are also introduced to exclude degenerated solution sets in several synthesis problems. The research reveals that appropriate numerical methods and synthesis equations can be chosen for obtaining most solutions efficiently and provide a complete solution set of a precision position synthesis problem within a domain of interest.

Author(s):  
Xin Ge ◽  
Anurag Purwar ◽  
Q. J. Ge

A 5-SS platform linkage generates a one-degree-of-freedom motion of a moving platform such that each of five moving points on the platform is constrained on a sphere, or in its degenerated case, on a plane. It has been well established a 5-SS platform linkage can be made to guide though seven positions exactly. This paper investigates the cases when the number of given positions are less than seven that allows for partial specification of locations of the moving points. A recently developed novel algorithm with linear structure in the design equations has been extended for the solution of the problem. The formulation of this expanded motion generation problem unifies the treatment of the input positions and constraints on the moving and fixed joints associated with the 5-SS platform linkage. Numerical examples are provided to show the effectiveness of the unified algorithm.


2008 ◽  
Vol 2008 ◽  
pp. 1-10 ◽  
Author(s):  
Shou-qiang Du ◽  
Yan Gao

For solving nonsmooth systems of equations, the Levenberg-Marquardt method and its variants are of particular importance because of their locally fast convergent rates. Finitely many maximum functions systems are very useful in the study of nonlinear complementarity problems, variational inequality problems, Karush-Kuhn-Tucker systems of nonlinear programming problems, and many problems in mechanics and engineering. In this paper, we present a modified Levenberg-Marquardt method for nonsmooth equations with finitely many maximum functions. Under mild assumptions, the present method is shown to be convergent Q-linearly. Some numerical results comparing the proposed method with classical reformulations indicate that the modified Levenberg-Marquardt algorithm works quite well in practice.


Author(s):  
Karl Kunisch ◽  
Philip Trautmann

AbstractIn this work we discuss the reconstruction of cardiac activation instants based on a viscous Eikonal equation from boundary observations. The problem is formulated as a least squares problem and solved by a projected version of the Levenberg–Marquardt method. Moreover, we analyze the well-posedness of the state equation and derive the gradient of the least squares functional with respect to the activation instants. In the numerical examples we also conduct an experiment in which the location of the activation sites and the activation instants are reconstructed jointly based on an adapted version of the shape gradient method from (J. Math. Biol. 79, 2033–2068, 2019). We are able to reconstruct the activation instants as well as the locations of the activations with high accuracy relative to the noise level.


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