The objective of the research was to develop common analytical structures for proportion «power–width–linear velocity» at the design stage of machine units. Existing method for calculating the power of machine-tractor units is suitable for use in science of machine and tractor operation. To widen and implement the above proportion at the design stage, performance model was enhanced by developing a set of two equations one of which is nonlinear. Graphical-analytical and numeric methods were used. As a result, the system analytical model comprising several equations on the basis of describing private laws (sections) of performance space was developed. In particular, the plane section of the relation “velocity–width” in the form of hyperbole was plotted, based on the synthesis of crosssections numerical solution of the problem was obtained. Such approach was implemented at the design of multiprocess units on the basis of the fifth generation of mobile power means equipped by stepless drive of translational motion. For mobile power means of the class 50 kN parameters for different units were calculated: for sowing and harvesting machine-tractor units (direct seeding of green manure crops) power – 220 kW, width (the same for both groups of machines) – 6 m, linear velocity – 10 km/h; for forage and tilling machine-tractor units power is the same, width – 3.2 m, linear velocity – 9-10 km/h. The developed analytical models for calculating the performance of machine-tractor unit at design based on the set of equations enables to calculate optimal ratios in the system of three physical parameters of machine-tractor unit on the basis of the fifth generation of mobile power means.
