A variable displacement piston pump, having: a housing, a pivot assembly to pivot between minimal and maximum pivot angles; a pump cover defining an actuator bore with an actuator piston, an actuator arm extending from the actuator piston to the pivot assembly; and an electronic control unit (ECU) coupled to the pump, the ECU having: a pump controller, a linear variable differential transducer (LVDT) coupled to the pump controller and the actuator piston, and an electrohydraulic solenoid valve (EHSV) coupled to the pump controller, the ECU is configured to: determine a pivot differential for the pivot assembly between a target pivot angle and a current pivot angle; determine a position differential for the actuator piston, corresponding to the pivot differential of the pivot assembly; control the EHSV to move the actuator piston by the position differential; and determine, from the LVDT, that the actuator piston moved by the position differential.

A zero turn mower vehicle 10 includes left and right hydrostatic transmissions 11a, 11b driving wheels 15a, 15b. The transmissions 11a, 11b each include a swashplate type axial piston hydraulic pump 17 having a swashplate 22. A system 12 and method controls each pump 17. A controller 31 receives input signals and provides output signals to electric motors 33a, 33b to control each swashplate 22. Operator interface input devices 30a, 30b provide inputs to controller 31. Angle sensors 35a, 35b provide additional inputs to controller 31. Displacement amplifiers 36a, 36b amplify displacement of each swashplate 22, and torque amplifiers 34a, 34b amplify torque of electric motors 33a, 33b.

A hydraulic system comprises: a hydraulic pump that includes an swash plate; an swash plate angle sensor for measuring the angle of the swash plate; an swash plate driving piston for moving the swash plate of the hydraulic pump in response to changes in pressure applied to a large diameter section; an swash plate control hydraulic line for supplying the large diameter section with a portion of the hydraulic oil discharged by the hydraulic pump; a control valve that controls the flow rate of the hydraulic oil that is following into and out of the large diameter section; an electro-proportional pressure reducing valve for producing pilot pressure that is to be transmitted to one side of the control valve; and a control device for controlling the electro-proportional pressure reducing valve according to an operation signal of an operation device and the angle information from the swash plate angle sensor.

A method for controlling a hydrostatic drive unit of a work vehicle may generally include determining a reference swashplate position of a hydraulic pump of the hydrostatic drive unit, wherein the reference swashplate position is associated with an uncompensated current command, and determining an actual swashplate position of the hydraulic pump, wherein the actual swashplate position differs from the reference swashplate position due to a loading condition of the work vehicle. The method may also include determining a closed-loop current command based a on the actual and reference swashplate positions and generating a modified current command based on the uncompensated current command and/or the closed-loop current command. The modified current command may differ from the closed-loop current command when an operator input is within a predetermined control input range and may be equal to the closed-Loop current command when the operator input is outside the predetermined control input range.