Patent ID: 8935009
Filing Date: 2015-01-13
Classification: F04B,G05D

Abstract:
1. A hydraulic system for providing hydraulic power to a load comprising: a first variable displacement hydraulic pump including a first swashplate pivotably supported with respect to the first pump and a first control valve for controlling an angle of inclination of the first swashplate, the first pump having a first discharge port out of which pressurized hydraulic fluid is discharged from the first pump and an associated discharge pressure; a second variable displacement hydraulic pump including a second swashplate pivotably supported with respect to the second pump and a second control valve for controlling an angle of inclination of the second swashplate, the second pump having a second discharge port out of which pressurized hydraulic fluid is discharged from the second pump and an associated discharge pressure, wherein the first and second discharge ports are connected such that the first and second pump have the same discharge pressure; and at least one controller in communication with the first and second control valves, the controller being configured with a first desired pump displacement control law for the first pump under which the first control valve is controlled as a function of pump displacement and a second desired pump discharge pressure control law for the second pump under which the second control valve is controlled as a function of the discharge pressure of the first and second pumps and being configured to use the first control law to determine a first intermediate control variable and to use the second control law to determine a second intermediate control variable; the controller combining the control of the first and second pumps using the first and second intermediate control variables and determining a desired control valve setting for the control valve of the first pump using the combined first and second intermediate control variables and the first control law and determining a desired control valve setting for the control valve of the second pump using the combined first and second intermediate control variables and the second control law.