A method of controlling a rotatable load by a hydraulic system, the method includes determining if the hydraulic system is in a first operating state or a second operating state; controlling the rotatable load in a valve control mode if the hydraulic system is in the first operating state, the valve control mode including controlling the rotatable load by controlling a valve arrangement; controlling the rotatable load in a displacement control mode if the hydraulic system is in the second operating state, the displacement control mode including controlling the rotatable load mainly by controlling the displacement of a hydraulic machine; and applying a non-zero absolute minimum displacement limitation to the hydraulic machine at least in the valve control mode.

An excavation position determination system achieves appropriate determination of an excavation start position in accordance with a shape or contour of an excavation target. The excavation position determination system includes: a photographing device that photographs an excavation target having a mountain shape and a bucket included in a working machine; a start position determinator that determines an excavation start position of the bucket to the excavation target. The start position determinator determines, on the basis of detected data from the photographing device, a position of the bucket where the bucket is not wholly hidden by the excavation target but a part of the excavation target and a part of the bucket overlap each other when the bucket is seen from a machine body of the working machine as the excavation start position.

Provided is a work machine that allows assisting a loading work without giving uncomfortable feeling to an operator. The control device 40 of the work machine 1 includes an allowable range calculation section 46 that calculates an allowable range indicating a range in which the front work device 2 is movable in a height direction allowed in a swing operation; an operation determining section 45 that determines whether the work machine 1 is under a convey operation; and an operation control section 4 that controls a turn operation of a boom 8 such that the position of the front work device 2 in the height direction remains within the allowable range when the work machine 1 is determined to be under the convey operation.

A follower pinion apparatus can include a swing gear system comprised of a swing gear and a swing motor pinion. The follower pinion apparatus can also include a nonmetallic follower pinion positioned to mesh with the swing gear and a sensor configured to sense a position of the follower pinion.

A swing drive system for an excavator is provided which utilizes a prime mover mechanically connected to a first hydraulic pump/motor and a second hydraulic pump/motor mechanically connected to a swing mechanism. The system includes a hydraulic circuit connecting a hydraulic fluid reservoir, a hydraulic accumulator, the first hydraulic pump/motor, and the second hydraulic pump/motor. The system is operable in one mode where the second hydraulic pump/motor acts as a pump to retard movement of the swing mechanism and pressurized hydraulic fluid from the second hydraulic pump/motor is pumped into the hydraulic accumulator. The system is operable in another mode where the pressurized fluid from the hydraulic accumulator is used to assist the prime mover in driving hydraulic consumers, including the swing drive.

A shovel includes a traveling undercarriage, an upper turning structure, an attachment, an end attachment position detecting device, an object detecting device, and a processor. The upper turning structure is turnably mounted on the traveling undercarriage. The attachment is attached to the upper turning structure, and includes an end attachment at an end thereof. The end attachment position detecting device is configured to detect the position of the end attachment. The object detecting device is configured to detect the position of an object. The processor is configured to control the movement of at least one of the attachment and the upper turning structure, based on the relative positional relationship between the excavation completion position of the end attachment and the position of the object.

A system and method for indicating to an operator a forward direction of travel of a machine having a ground-engaging traveling device, a superstructure rotatably mounted to the traveling device and an operator station defining an operator point of view are provided. The system includes a system controller, a rotation-sensing system connected to the system controller for determining a rotational relationship of the superstructure with respect to the traveling device, and a singaler mounted to the operator station and connected to the system controller for indicating to the operator the forward direction of travel of the machine in accordance with the operator point of view. The method includes receiving a rotational relationship of the superstructure with respect to the traveling device, and indicating to the operator the forward travel direction of the machine in accordance with the operator point of view.

The construction machine includes: an input interface which permits an input of a provisional target position of the attachment in a virtual space; a target position calculation part which calculates an actual target position that is a target position of the attachment in a real space from the provisional target position; an operational amount calculation part which calculates an operational amount required to make a current position of the attachment coincide with the actual target position of the attachment coincide with the actual target position with respect to at least one driven target selected from a lower traveling body, an upper slewing body, a working device, and the attachment; and a control part which controls an operation of one of the actuators for driving the driven target in accordance with the calculated target operational amount.

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.