A hydraulic drive system raises and lowers an object by supplying and discharging operating oil to and from two ports of an actuator and includes a control device, first to fifth electromagnetic proportional control valves, first and second hydraulic pumps, a first and second control valve, and a lock valve. When a fourth pilot pressure is output, the second control valve causes the operating oil to be discharged from a first port in order to lower the object. The lock valve prevents the operating oil from being discharged from the first port by closing a path between the first port and the second control valve, and when a fifth pilot pressure is output from the fifth electromagnetic proportional control valve per an operating device, discharges the operating oil from the first port by opening the path between the first port and the second control valve, to lower the object.

A control calculation device performs a calculation of compensating for a volume change amount of each pressure chamber caused by a positional change of a pressure receiving plate inside a cylinder chamber for each position command value applied to two servo amplifiers, outputs each of the compensated position command values to the two servo amplifiers, and executes origin positioning for a position of a slider in order to compensate for the volume change amount.

A linear actuator system includes a linear actuator and at least one integrated pump assembly connected to the linear actuator to provide fluid to operate the linear actuator. The integrated pump assembly includes a pump with at least one fluid driver comprising a prime mover and a fluid displacement assembly to be driven by the prime mover such that fluid is transferred from a first port of the pump to a second port of the pump. The pump assembly also includes two valve assembles to isolate the pump from the system. The linear actuator system also includes a controller that establishes at least one of a speed and a torque of the at least one prime mover to exclusively adjust at least one of a flow and a pressure in the linear actuator system to an operational set point.

A downforce control system for an agricultural ground engaging unit provides individual control of each agricultural ground engaging row unit by providing a proportional pressure control valve connected to the retracting chamber of a double acting cylinder which varies the upward force produced by the retracting chamber of the cylinder against a constant counteracting downward force produced by an extending chamber of the cylinder, the valve control based on a comparison of a sensed resultant downward force on the agricultural ground engaging row unit and a predetermined target downward force.

A hydraulic control system includes a first hydraulic cylinder, a second hydraulic cylinder, a fluid supply apparatus, a first control valve bank, a second control valve bank, a third control valve bank, and a first check valve. The first control valve bank is configured to independently control the first hydraulic cylinder; the second control valve bank is configured to independently control the second hydraulic cylinder; and the third control valve bank is configured to synchronously control the first hydraulic cylinder and the second hydraulic cylinder. Synchronous volume control is implemented through series connection of the hydraulic cylinders, and has quite high synchronization precision, which is measured to be up to two percent.

A hydraulic system (600) and method for reducing boom dynamics of a boom (30), while providing counter-balance valve protection, includes a hydraulic cylinder (110), first and second counter-balance valves (300, 400), and first and second control valves (700, 800). A net load (90) is supported by a first chamber (116, 118) of the hydraulic cylinder, and a second chamber (118, 116) of the hydraulic cylinder may receive fluctuating hydraulic fluid flow from the second control valve to produce a vibratory response (950) that counters environmental vibrations (960) on the boom. The first control valve may apply a holding pressure and thereby hold the first counter-balance valve closed and the second counter-balance valve open.

A vehicle includes: a prime mover; a hydraulic fluid manifold; a hydraulic machine; a hydraulic accumulator; one or more hydraulic actuators; a valve arrangement; and a controller. The controller is configured to receive an actuator demand signal indicative of a demand to move the one or more hydraulic actuators; and to control the hydraulic machine and the valve arrangement to cause movement of the one or more actuators in accordance with the actuator demand signal by bringing the hydraulic accumulator into fluid communication with a first actuator chamber of the one or more hydraulic actuators, and to synchronise therewith changing a pressure in a second actuator chamber of the one or more hydraulic actuators. The second actuator chamber is in fluid communication with the hydraulic machine.

An agricultural machine includes a float cylinder interconnecting a header linkage system and a frame. A rod side accumulator is in fluid communication with a rod side fluid port of the float cylinder. A float control valve is selectively controllable between an open position allowing fluid communication between a pressure source and the rod side accumulator, and a closed position blocking fluid communication between the pressure source and the rod side accumulator. A downforce accumulator is in fluid communication with a piston side fluid port of the float cylinder. A downforce control valve controls fluid communication between the pressure source and the downforce accumulator. A downforce return valve controls fluid communication between the downforce accumulator and the tank.

Provided is a fluid actuator capable of safely driving a drive target. An air actuator using air as a working fluid includes an X-axis pressure sensor that measures air pressures PX+ and PX− along one drive axis, which drives a drive target in an X direction, a Y-axis pressure sensor that measures air pressures PY1+, PY1−, PY2+, and PY2− along two drive axes, which drive the drive target in a Y direction, and an acceleration detection unit that detects translational acceleration and rotational acceleration generated in the drive target on the basis of the measured air pressures PX+, PX−, PY1+, PY1−, PY2+, and PY2−.

Agricultural planting implements, as well as other ground-engaging implements, can utilize supplemental force assemblies to provide up and/or down force at the row or rows of the implements. The force can be used to overcome changing field conditions, obstructions, as well as changing particulate amounts and weights carried by the rows of the implements, and the implement itself. The up force can be set at system pressure, or can include control valves at each of the row units to control the amount of up force provided. The down force can be controlled by control valves at each of the row units, and can be used to overcome the up pressure or provide a designated amount of down force to the row.