Planter Depth Control - Theory and Practice

A review of prior art and current research in the field of planter depth control is presented. Industry trends towards heavier, wider machines with improvements in trash flow and compromises in seed placement accuracy are discussed. Two-dimensional models of planter frame geometry and terrain following ability from the literature is extended to a realistic three-dimensional representation. Dynamic modelling of a simple single disc opener suspension system is reported from the literature. A state space description is then developed which recognises each seed drop as a discrete process and allows the governing differential equations to be solved by a finite difference method. Results of experiments to determine the load/depth characteristics of coulters and openers together with stiffness constants and viscous coefficients of press wheels are included. Various terrain evaluation techniques are examined with regard to the demands on sowing depth regulation systems. Experiments to quantify the relationships between surface topography and the depth to the drying front are also described. Conclusions are drawn as to the utility and limitations of the model for the design of planter depth control systems and component layouts.