A large manipulator includes a chassis, a turntable arranged on the chassis and rotatable around a vertical axis via a rotary drive, and an articulated mast including two or more mast segments pivotably-movably connected, via articulated joints, with the respectively adjacent turntable or mast segment via a respective drive. The large manipulator further includes a mast sensor system configured to detect position of at least one point of the articulated mast or a pivot angle of at least one articulated joint and configured to generate sensor output signals. The large manipulator further includes a control device configured to actuate the drive in a normal operation for mast movement and to limit speed of movement of the articulated mast depending upon the sensor output signals. The drive is manually controllable in an emergency operation. The large manipulator further includes at least one limiting means, which, in the emergency operation, limit speed of the drive to a pre-specified maximum value.

A valve includes a bore within a valve body having a central axis. A plurality of galleries in the bore define flow paths for hydraulic fluid. A spool is positioned in the bore, and the spool is moveable along the central axis between a first position in which hydraulic fluid from a central pump gallery is prevented from flowing to first and second working galleries and from flowing to one or more tank galleries; a second position in which hydraulic fluid from the central pump gallery is in fluid communication with both the first and second working galleries simultaneously; and a third position in which the first and second working galleries are in fluid communication with the one or more tank galleries simultaneously.

A hydraulic system includes first and second control valves controlling a flow rate of operation fluid to be supplied to first and second hydraulic actuators, respectively, a supply fluid tube connecting the first control valve and the second control valve and being connected to a return fluid tube, and a discharge fluid tube connected to the second control valve. The second control valve is switched between primary, secondary, and tertiary positions, the primary position blocking between the supply fluid tube and the discharge fluid tube and allowing return fluid to be supplied to the second hydraulic actuator, the secondary position communicating between the supply fluid tube and the discharge fluid tube and stopping supplying the return fluid to the second hydraulic actuator, and the tertiary position communicating between the supply fluid tube and the discharge fluid tube and allowing the return fluid to be supplied to the second hydraulic actuator.

A controller (25) of the hydraulic excavator (1) includes a signal separation section (150) that separates each of target speed signals for a plurality of front members (8, 9, 10) into a low frequency component and a high frequency component, a high fluctuation target speed calculation section (143) that allocates the separated high frequency components preferentially to a front member having a relatively small inertial load to calculate high fluctuation target speeds individually for the plurality of front members, a high fluctuation target actuator speed calculation section (141c) that calculates high fluctuation target speeds individually for the plurality of actuators from the high fluctuation target speeds for the plurality of front members, a low fluctuation target actuator speed calculation section (141b) that calculates low fluctuation target speeds individually for the plurality of actuators from the low frequency components separated by the signal separation section, and an actuator controller (200) that controls the plurality of actuators individually based on values obtained by adding the high fluctuation target speeds and the low fluctuation target speeds.

A work machine operation assistance device enables setting of a manipulation gain appropriate for a skill level and habits of an operator and/or actual work contents. The work machine operation assistance device includes: a manipulation gain storage section storing a manipulation gain; a manipulated variable detection section detecting a manipulated variable of the operating device; a time integration section adding up time that the operating device is operated; a manipulated-variable frequency arithmetic section computing a manipulated-variable frequency of the operating device; a manipulated-variable frequency criterion setting section presetting a criterion value for the manipulated-variable frequency; a manipulation gain update arithmetic section performing a computation to update the manipulation gain; a manipulation gain display section displaying a result of the manipulation gain computed; and a manipulation gain update selection section to select whether or not an update to the manipulation gain displayed on the manipulation gain display section is performed.

A hydraulic system includes first and second control valves controlling a flow rate of operation fluid to be supplied to first and second hydraulic actuators, respectively, a supply fluid tube connecting the first control valve and the second control valve and being connected to a return fluid tube, and a discharge fluid tube connected to the second control valve. The second control valve is switched between primary, secondary, and tertiary positions, the primary position blocking between the supply fluid tube and the discharge fluid tube and allowing return fluid to be supplied to the second hydraulic actuator, the secondary position communicating between the supply fluid tube and the discharge fluid tube and stopping supplying the return fluid to the second hydraulic actuator, and the tertiary position communicating between the supply fluid tube and the discharge fluid tube and allowing the return fluid to be supplied to the second hydraulic actuator.

A controller according to the present invention has: a storage section that stores a first relationship between manipulated variables of an operating lever preset for each vehicle-body weight and target delivery pressures of a hydraulic pump; a target delivery pressure computation section that applies the vehicle-body weight inputted through an input device and the manipulated variable of the operating lever corresponding to a pilot pressure detected by pilot pressure sensors, to a first relationship stored in the storage section in order to calculate a target delivery pressure of the hydraulic pump; and a feedback control section that performs feedback control on the center bypass selector valve such that the delivery pressure of the hydraulic pump detected by the delivery pressure sensor agrees with the target delivery pressure of the hydraulic pump calculated by the target delivery pressure computation section.

A work vehicle includes a first frame, a second frame pivotally coupled to the first frame at an articulation joint, and a control circuit operable to control relative movement of the first and second frames about the articulation joint. The control circuit includes a pump, an actuator in fluid communication with the pump, and a first valve assembly coupled to a user-manipulable control. The first valve assembly is configured to direct fluid from the pump to the actuator in response to movement of the user-manipulable control to pivot the first and second frames. The control circuit also includes a second valve assembly configured to direct fluid from the pump to the actuator in response to receiving an electronic control signal to pivot the first and second frames.

A method for controlling a speed of a hydraulic cylinder (2) in a hydraulic system (1) is provided. The hydraulic system (1) may include a hydraulic cylinder (2) fluidly connected to a load-holding valve arrangement (3) including a first load-holding valve (4) connected to a first end (5) of the hydraulic cylinder (2) and a second load-holding valve (6) connected to a second end (7) of the hydraulic cylinder (2). The hydraulic system (1) may further include a flow-control valve arrangement (8) comprising a directional flow-control valve (9) and at least one hydraulic pump (10).

A hydraulic system for a work machine includes a first control valve including a first direction switch to switch a direction in which the operation fluid is to flow through a first hydraulic actuator and a pressure compensator to maintain a differential pressure to a constant pressure, the differential pressure being a difference between a pressure of the operation fluid to be inputted to the pressure compensator and a pressure of the operation fluid to be outputted from the pressure compensator. And, the hydraulic system includes a second control valve including a second direction switch to switch a direction in which the operation fluid is to flow through a second hydraulic actuator and a flow rate prioritizer to prioritize a flow rate of the operation fluid to be outputted to the second hydraulic actuator.