OPTIMIZATION-BASED SYNTHESIS OF A DEEP-DIGGING TILLAGE MECHANISM

Abstract

A quasi-Newton optimization method is employed to synthesize a four-bar tillage mechanism, a device for loosening the sub-soil in farm fields. The synthesis routine uses sequential parameter transformations that map from an unconstrained search variable space to a constrained design variable space. The sequential parameter transformations ensure that only a specific mechanism sub-type is considered, that Grashof criteria are satisfied, and that all mechanism parameters satisfy specified upper and lower constraints. Objective functions quantifying the level of satisfaction of the desired task displacements are minimized. It is shown that in addition to task satisfaction, further objective function terms can be added. The addition of objective function terms to increase the minimum transmission angle and to reduce the mechanism size are found to allow the synthesis of a practical mechanism for the deep-digging application. The use of the Broyden-Fletcher-Goldfarb-Shanno (BFGS) method with Fletcher’s Line Search (FLS) algorithm has allowed for the development of an efficient optimization-based synthesis routine. The synthesis results demonstrate that the developed synthesis routine required on the order of 102 fewer iterations per start then the direct-search and Sequential Unconstrained Minimization Technique (SUMT) employed in a previous method.