Patent ID: 8393150

Claim:
A machine including an engine and a hydraulic system having a reservoir connected to a drain passage, the hydraulic system including an implement valve disposed to operate an implement, the implement valve providing fluid at a load sensing pressure within a control conduit during operation, the machine comprising: a manual control device adapted to provide a request signal; a variable displacement pump operably connected to the engine, disposed to receive a torque limit from the engine, and associated with the hydraulic system, the variable displacement pump providing an operating fluid flow at a supply pressure to the hydraulic system, the operating fluid flow being correlated to a load during operation; a control valve fluidly connected to the control conduit and operating to adjust a displacement setting of the variable displacement pump based on a pressure difference between a reference pressure and the supply pressure; an electro-hydraulic relief valve in fluid communication with the control conduit and the drain passage, the electro-hydraulic relief valve disposed to selectively vent fluid from the control conduit into the drain passage in response to a command signal; an electronic controller associated with the implement valve, the electro-hydraulic relief valve and the engine, and disposed to receive at least one signal that is indicative of at least one machine operating parameter, the electronic controller being further disposed to calculate the reference pressure and provide the command signal to the electro-hydraulic relief valve based on the reference pressure; wherein the electronic controller is further disposed to receive a pressure signal that is indicative of a pressure of fluid at an outlet of the variable displacement pump, wherein the reference pressure is at least partially based on a derivative of the pressure signal.