A method of controlling a hydraulic actuator, wherein the hydraulic actuator includes a linear double-acting output member, and at least three working chambers in fluid connection with the output member, the working chambers having respective effective areas with a non-binary relationship; wherein the method includes selectively fluidly connecting each working chamber to either a high-pressure side or a low-pressure side to provide a plurality of discrete pressurization states of the hydraulic actuator; determining at least one of the pressurization states as a prevented pressurization state; and transitioning between a plurality of allowed pressurization states among the pressurization states while preventing transition to the at least one prevented pressurization state. A hydraulic actuator and a hydraulic system are also provided.

To reduce the burden of an operator when performing a task for identifying which posture information detection sensor is mounted on which front member in a construction machine where the posture information detection sensors are mounted on multiple front members constituting a working machine. An automatic identification system is provided which has an identification task start button for being operated to start an identification task, a front member control means for outputting a control instruction for driving and stopping multiple front members sequentially, individually, and automatically, and a sensor identification means for identifying IMU mounted on each front member based on changes of a detection value of IMU as said each front member is driven by the front member control means.

A hydraulic system of a construction machine includes: control valves interposed between a main pump and hydraulic actuators; and first solenoid proportional valves connected to pilot ports of the control valves. The hydraulic system further includes: a brake for a slewing motor; and a second solenoid proportional valve connected to a brake release port of the brake by a secondary pressure line and connected to an auxiliary pump by a primary pressure line. A switching valve including a pilot port connected to the secondary pressure line by a pilot line is interposed between the auxiliary pump and the first solenoid proportional valves.

Provided is a construction machine which can promptly adjust the rotational speed of a swing motor to a target rotational speed. A controller calculates a target rotational speed of the swing motor based on input from an operation device, calculates a degree of deviation of a rotational speed detected by a rotational speed sensor from the target rotational speed, sets a target driving pressure of the swing motor according to a moment of inertia about a swing axis of a swing structure and a work device and controls a pressure adjusting device in such a manner as to reduce a difference between a driving pressure detected by a pressure sensor and the target driving pressure, when the degree of deviation is larger than a predetermined value, and controls the pressure adjusting device in such a manner as to reduce a difference between the rotational speed detected by the rotational speed sensor and the target rotational speed, when the degree of deviation is equal to or smaller than the predetermined value.

A hydraulic excavator drive system includes a regeneration line, which connects an arm pushing and an arm crowding supply line, each of which extends between an arm cylinder and arm control valve. The regeneration line includes regeneration and switching valves. A release line that is branched off from the regeneration line at a position between the regeneration valve and the switching valve is provided with a release valve. A secondary pressure from a first solenoid proportional valve is fed to a pilot port of the regeneration valve such that the regeneration valve opens at a time of arm crowding. A secondary pressure from a second solenoid proportional valve is fed to a pilot port of the release valve such that release valve opens at a time of arm pushing. An arm pushing pilot pressure for moving the arm control valve is led to a pilot port of the switching valve.

A method for controlling an attachment provided to a boom of a vehicle, the method including: sensing a ground force on the attachment; determining if the ground force is outside a target deadband, wherein the target deadband is based on a height of the attachment over the ground, and, if the ground force is outside the target deadband, adjusting a cylinder pressure to bring the ground force within the deadband. A system for controlling an attachment on a boom, the system including: a control system; a hydraulic system for at least a first piston provided to the boom; and a first pressure sensor for sensing a pressure related to the attachment and communicating the sensed pressure to the control system, wherein the control system determines if the pressure is outside a target deadband, and, if so, adjusts a pressure at the piston to bring the sensed pressure within the deadband.

A hydraulic work system can include a continuously variable displacement hydraulic pump that is powered by an engine and is in communication with a hydraulic actuator. A run-time displacement of the hydraulic pump for movement of the hydraulic actuator can be controlled based on a speed of the engine.

A working machine includes a machine body, a dozer, a boom, an arm, a working tool, a boom cylinder, and an arm cylinder. The working machine also includes an arm crowd restricting unit and a crowd restriction releasing unit. The arm crowd restricting unit imposes a restriction on a stroke of the arm cylinder in an arm crowd direction so that a swing track of a distal end portion of the working tool is spaced from the boom cylinder. The crowd restriction releasing unit releases the restriction on the stroke of the arm cylinder to enable the arm to swing to an end of a swing range in the arm crowd direction when the boom is at a swing position at which the working tool in an operating position close to a working-tool dump position is disposed in a vicinity of a blade.

A multiple mode operational system for a work machine may comprise a frame, a ground-engaging mechanism coupled to the frame, an attachment, an object detector, and a multiple mode control system. The multiple mode control system may include a control device and a controller receiving a signal from the control device. The controller may have a first operational mode and a second operational mode. The first operational mode may enable a first sensitivity response to the control device and the second operational mode may enable a second sensitivity response to the control device. The controller may be configured to receive an object signal from the object detector and modify the operational mode of the controller based on a detected distance of the object from a reference point.

A carrier comprising a hydraulic cylinder having a piston, a controller and a piston position sensor, wherein the carrier is arranged to carry an accessory through the use of the hydraulic cylinder and wherein the controller is configured to: receive piston position information; determine a direction of movement of the piston; and if the piston position equals a stop distance from an end wall of the hydraulic cylinder in the direction of movement, abort the movement.