Hydro-mechanical threshing rotor control system for an agricultural combine

A hydro-mechanical control system for an agricultural combine threshing rotor is operable 1) to transfer torque to the rotor so as to maintain rotor velocity within an acceptable range of a commanded velocity despite small fluctuations in rotor load and engine speed, 2) to reduce wear on mechanical components of the rotor drive system during rotor acceleration, 3) to employ the most efficient combination of mechanical and hydrostatic rotor drive characteristics during steady state operation of the rotor and 4) to reduce the likelihood of engine stall. The system includes a mechanical motor such as an engine, a hydrostatic motor, and a gearset disposed between both motors and the rotor. A clutch is operable to selectively couple the mechanical motor to the gearset, and a brake is selective operable to selectively arrest a driven gear of the gearset from rotation.