Reliability integration into tillage machine design process is a new strategy to overcome the drawbacks of
classical design approaches and to achieve designs with a required reliability level. Furthermore, design
optimization of soil tillage equipments under uncertainty seeks to design structures which should be
both economic and reliable. The originality of this research is to develop an efficient methodology that
controls the reliability levels for complex statistical distribution cases of random tillage forces. This
developed strategy is based on design sensitivity concepts in order to determine the influence of each
random parameter. The application of this method consists in taking into account the uncertainties on
the soil tillage forces. The tillage forces are calculated in accordance with analytical model of McKyes
and Ali with some modifications to include the effect of both soil–metal adhesion and tool speed. The
different developments and applications show the importance of the developed method to improve
the performance of the soil tillage equipments considering both random geometry and loading parameters.
The developed method so-called OSF (Optimum Safety Factor) can satisfy a required reliability level
without additional computing time relative to the deterministic design optimization study. Since the
agricultural equipment parameters are extremely nonlinear, we extended the OSF approach to several
nonlinear probabilistic distributions such as lognormal, uniform, Weibull and Gumbel probabilistic
distribution laws.