Patent ID: 7778756

Claim:
A system for controlling a left hydrostatic drive that drives a left propulsion structure of a vehicle and a right hydrostatic drive that drives a right propulsion structure of a vehicle, the left hydrostatic drive and the right hydrostatic drive being powered by an engine, the engine having an engine speed, the system comprising: a controller that generates a left hydrostatic drive output signal for varying an output of the left hydrostatic drive and a right hydrostatic drive output signal for varying an output of the right hydrostatic drive, the controller using a plurality of operator selectable feedback algorithms to control the left hydrostatic drive output signal and the right hydrostatic drive output signal; at least one of the feedback algorithms employing a load multiplier to scale the left hydrostatic drive output signal and the right hydrostatic drive output signal, the load multiplier being continuously defined as a function of the engine speed and by a band of engine speeds with an upper boundary and a lower boundary, the load multiplier being defined as 0% at and below the lower boundary, the load multiplier being defined as 100% at and above the upper boundary, and the load multiplier increasing from 0% to 100% from the lower boundary to the upper boundary; at least one of the feedback algorithms employing a left propulsion speed correction factor derived from a difference between a calculated speed of the left hydrostatic drive and a measured speed of the left hydrostatic drive; at least one of the feedback algorithms employing a right propulsion speed correction factor derived from a difference between a calculated speed of the right hydrostatic drive and a measured speed of the right hydrostatic drive; at least one of the feedback algorithms employing a left propulsion pressure correction factor derived from a difference between a calculated hydraulic pressure of the left hydrostatic drive and a measured hydraulic pressure of the left hydrostatic drive; at least one of the feedback algorithms employing a right propulsion pressure correction factor derived from a difference between a calculated hydraulic pressure of the right hydrostatic drive and a measured hydraulic pressure of the right hydrostatic drive; the feedback algorithms including a first feedback algorithm that scales the left hydrostatic drive output signal using the load multiplier and the left propulsion speed correction factor, a second feedback algorithm that scales the left hydrostatic drive output signal using the load multiplier and the left propulsion pressure correction factor, a third feedback algorithm that scales the right hydrostatic drive output signal using the load multiplier and the right propulsion speed correction factor, and a fourth feedback algorithm that scales the right hydrostatic drive output signal using the load multiplier and the right propulsion pressure correction factor; and a user interface that allows an operator to manually adjust the upper boundary and the lower boundary of the band of engine speeds.