A method and control system operable to control movement of a work implement of a work vehicle. The control system includes a reservoir that retains fluid, a pump in fluid communication with the reservoir, and an actuator in fluid communication with the pump. The actuator has a first side and a second side. A control valve is fluidly positioned between the pump and the actuator, a first proportional relief valve is fluidly positioned between the pump and the first side of the actuator, and a second proportional relief valve is fluidly positioned between the pump and the second side of the actuator. The first proportional relief valve is configured to permit flow of fluid from the first side of the actuator to the reservoir when a pressure at the first side of the actuator exceeds a pressure set point.

A flow control valve includes a valve body having an inner circumferential surface defining a longitudinal bore to which first and second fluid passages are connected. A spool is slidably inserted into the bore to allow a flow of fluid from the first to second fluid passage. A valve regulates a flow rate of fluid flowing through the first fluid passage. A first seat surface is defined between an area in which the first fluid passage is connected to the bore and an area in which the second fluid passage is connected to the bore. When the flow of fluid from the first to second fluid passage is initiated, an area of a gap between the first seat surface and the spool on a plane taken in a transverse direction is 5%˜50%, preferably 10%˜20% of an area of an opening defined by the first seat surface.

An actuator control arrangement includes a hydraulic actuator having a housing and a piston rod axially moveable within the housing, a stop disposed within the housing to limit the extent of movement of the piston rod into the housing, and a solenoid valve arranged between a pressure source and the actuator. The solenoid valve is switchable between a first mode and a second mode in response to an electric control signal, wherein, in the first mode, the solenoid valve creates a fluid flow path from the pressure source to the actuator so as to locate the stop in its neutral position and in the second mode, the solenoid valve creates a fluid flow path to release pressure from the actuator to permit the stop to move to its retracted position. In the event of electrical failure, the stop will set the actuator to its neutral position.

Windrow mergers employ one or more design features as described herein in connection with a suspension assembly that allows the pickup head to rise or fall relative to a frame of the merger. One feature maintains a substantially constant force or pressure between a pickup head of the merger and the terrain regardless of a height of the head. Another feature maintains a substantially constant hydraulic pressure in a hydraulic actuator that connects the pickup head to a frame assembly of the merger. Still another feature employs a hydraulic pump driven by a power takeoff (PTO) of the tractor to charge and discharge a hydraulic actuator arranged to raise and lower the pickup head of the merger between an upper limit and a lower limit.

Windrow mergers employ one or more design features as described herein in connection with a suspension assembly that allows the pickup head to rise or fall relative to a frame of the merger. One feature maintains a substantially constant force or pressure between a pickup head of the merger and the terrain regardless of a height of the head. Another feature maintains a substantially constant hydraulic pressure in a hydraulic actuator that connects the pickup head to a frame assembly of the merger. Still another feature employs a hydraulic pump driven by a power takeoff (PTO) of the tractor to charge and discharge a hydraulic actuator arranged to raise and lower the pickup head of the merger between an upper limit and a lower limit.

Even where the differential pressure across a directional control valve associated with each actuator is very small, flow dividing control of the plurality of directional control valves can be performed stable, and even where a demanded flow rate suddenly changes at the time of transition from composite action to single action or the like, a sudden change of the flow rate of hydraulic fluid to be supplied to each actuator is prevented to implement superior combined operability. Further, the meter-in loss of the directional control valves can be reduced to implement a high energy efficiency. To this end, a plurality of pressure compensating valves 7a, 7b and 7c for controlling such that the pressure in the downstream side of the meter-in opening of a plurality of directional control valves 6a, 6b and 6c becomes equal to the highest load pressure are individually arranged in the downstream side of meter-in openings of the plurality of directional control valves 6a, 6b and 6c, and demanded flow rates for the directional control valves 6a, 6b and 6c are calculated from input amounts of operation levers. Besides, the meter-in pressure loss of a predetermined directional control valve is calculated from the demanded flow rates for and meter-in opening areas of the directional control valves 6a, 6b and 6c, and the set pressure of the unloading valve 15 is controlled using the value of the meter-in pressure loss.

A mobile hydraulic system includes a hydraulic actuator coupled to a load, and a control unit coupled to the load and/or to the hydraulic actuator. The control unit is adapted to anticipate an over-center transition of the load relative to a gravity vector prior to the over-center transition through the use of sensors configured with accelerometers, gyroscopes and magnetometers. In some examples, the over-center transition is from an overrunning driving of the load to a passive driving of the load. In some examples, the over-center transition is from a passive driving of the load to an overrunning driving of the load. In some examples, the control unit is adapted to control change in a metered flow through one or more ports of the associated actuator to minimize and/or prevent one or more hydraulic effects of the anticipated over-center transition. In some examples, the control unit controls the metered flow by causing one or more actuators (e.g., a solenoid) to shift one or more valve positions to change the flow through one or more ports of the associated actuator.

A flow valve control method, apparatus, and storage medium are provided. The method comprises: conducting a median current value teach-in of a flow valve starting from an initial median current value of the flow valve; and correcting a flow-current curve of the flow valve based on a deviation value obtained by the teach-in. Each teach-in process comprises: controlling current output to a flow valve, so that the flow valve successively goes through: when there is a flow passing through, an output flow enables a shifting mechanism to return to position, and when there is a flow passing through again, an output flow again enables the shifting mechanism to return to position; recording a current value the twice when there is a flow passing through the flow valve as a maximum median current value; and acquiring a deviation value of the maximum median current value from the initial median current value.

A hydraulic system may include an electrohydraulic control valve disposed in fluid communication between a source of pressured fluid and a hydraulic actuator. The hydraulic system may be controlled to correct for offset errors between a target actuator pressure and a current actuator pressure output from the control valve, without amplifying pressure oscillations in the fluid between the control valve and the hydraulic actuator.

A flow valve control method, apparatus, and storage medium are provided. The method comprises: conducting a median current value teach-in of a flow valve starting from an initial median current value of the flow valve; and correcting a flow-current curve of the flow valve based on a deviation value obtained by the teach-in. Each teach-in process comprises: controlling current output to a flow valve, so that the flow valve successively goes through: when there is a flow passing through, an output flow enables a shifting mechanism to return to position, and when there is a flow passing through again, an output flow again enables the shifting mechanism to return to position; recording a current value the twice when there is a flow passing through the flow valve as a maximum median current value; and acquiring a deviation value of the maximum median current value from the initial median current value.