US Patent 7778756 Track trencher propulsion system with load control

A system and process for controlling propulsion and steering of a track trencher excavation machine powered by an engine includes a multiple mode propulsion and steering control system that performs a plurality of functions depending on a selection of one of a plurality of operational modes. A controller generates a vehicle propulsion hydrostatic drive signal using an engine speed to determine a load multiplier. The load multiplier being defined as a function of the engine speed and an operator adjustable load control setting.