Optimal synthesis of a mechanism protecting a cultivating tool from overload with a selected plough safety device as an example. Part II. Minimization of criterion of optimization

Abstract

The aim of this work was such definition of the values of constructional parameters of work process of a selected safety device protecting a cultivating tool (e.g. plough body) from overload to be able to obtain the least difference between protecting forces: a force realized by a safety device F_x and a force expected by a user F_xo. The task was limited to the search for the minimal value of objective function, which described that difference and it was realized with the method of nonlinear optimization using the software package Mathcad. As a criterion of optimization, an error mean-square between functions of the mentioned forces F_x and F_xo in defined ranges of working depth h of a cultivating element and a regulation parameter r of the force value was assumed. To define selectively fragments of variation of objective function significant for realized process (following from rank of selection of values of overload forces) variation ranges of parameters h and r were digitized. Values of force F_xo were given in a table but for a force F_x a mathematical model from part I of this work was used, which among other things defined a set of parameters of work process of a safety device, which influenced its value and admissible values of the parameters. Constructional parameters were divided into two subsets: constant parameters X_Ks (sssumed values, following from assignment of a safety device and cultivating tool) and matched parameters X_Kd (matched values as a result of realized optimal synthesis). Two limitations were introduced: necessary condition of obtainment of para-uelism of a frame of a cultivating tool to soil surface during its cultivation and not large force (max 6 kN) on an adjusting nut allowing to change easily (by a user) the value of overload force according to using conditions. Algorithm of selection of desired values was given. Assumed and matched values of parameters of safety device work process were shown in a table and realization of optimal synthesis was illustrated in the work.