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 system and method are provided for adaptive calibration of a self-propelled work vehicle comprising a chassis and a blade front-mounted thereto for working a ground surface. First sensor signals correspond to a blade slope, and second sensor signals correspond to a chassis slope. During a first operating mode, a blade position is controlled relative to the chassis, based at least on a stored calibration value and a detected difference between the blade slope and a target slope of the ground surface, and a difference is also determined between the chassis slope and the target slope of the ground surface. During a second operating mode, the position of the blade is controlled relative to the chassis until the chassis slope corresponds to the target slope of the ground surface, and the stored calibration value is altered based on adjustments to the blade position during the second operating mode.

A machine comprises a first ground engaging unit connected to a first leg, a second ground engaging unit connected to a second leg, and a hydraulic system to control heights of the legs, the hydraulic system comprises a fluid circuit to control fluid between the first and second legs, a load holding valve to allow fluid into the fluid circuit, a control valve system to let fluid into the load holding valve, the control valve connected to a hydraulic fluid source and a reservoir, a first lock valve to control flow of fluid between the first and second legs in a first direction, a second lock valve to control flow of fluid between the second and first legs in a second direction, and first and float valves configured to connect the first and second legs to the control valve system, respectively.

A working machine includes a switching valve to switch between a first state and a second state, the first state allowing a revolving speed of a traveling motor to be a first speed, the second state allowing the revolving speed of the traveling motor to be a second speed, and a controller device to reduce the revolving speed of the prime mover in either acceleration to switch from the first state to the second state or deceleration to switch from the second state to the first state. The controller device associates a return timing with a switch timing in either the acceleration or deceleration, the return timing allowing an actual revolving speed of a prime mover to start returning toward a first target revolving speed after the actual revolving speed is reduced, the switch timing allowing the switching valve to switch to either an acceleration side or a deceleration side.

A work machine that can keep the control accuracy of actuators irrespective of temperature variation of a hydraulic operating fluid that passes through flow rate controllers that control the flow rates of supply to the actuators is provided. For this purpose, the flow rate controllers each have a valve body that is disposed on a main hydraulic line connecting a delivery line of a hydraulic pump and the actuator and that moves according to an operation pressure from a solenoid proportional pressure reducing valve, a sampling hydraulic line that branches from the main hydraulic line, and a temperature sensor set on the sampling hydraulic line. The controller is configured to correct a command electrical signal to the solenoid proportional pressure reducing valve according to a signal from the temperature sensor.

A control unit for a hydraulic system includes a hydraulic actuator including an actuator chamber the hydraulic actuator including a first actuator portion and a second actuator portion wherein the first actuator portion can move relative to the second actuator portion, the actuator chamber being in fluid communication with a flow rale control arrangement adapted to control a rate of flow from the actuator chamber. The control unit is adapted to receive a load signal indicative of the magnitude of the load applied to the hydraulic actuator, receive a requested speed signal indicative of a desired relative movement speed between the first actuator portion and the second actuator portion in a direction that reduces the chamber volume, and based on the load signal and the requested speed signal, issue a control signal to the flow rate control arrangement indicative of a desired flow rate from the actuator chamber.

A hydraulic system includes a first hydraulic actuator, a second hydraulic actuator, a first pump to supply operation fluid to the first hydraulic actuator, a second pump to supply operation fluid to the second hydraulic actuator, a second control valve to control operation fluid to be supplied from the second pump to the second hydraulic actuator, and a first control valve including a main control valve to control operation fluid to be supplied from the first pump to the first hydraulic actuator, and a subordinate control valve configured to control operation fluid to be supplied from the second pump to the second control valve and to the first hydraulic actuator. The operation fluid supplied from the second pump is confluent with operation fluid to be supplied from the first pump to the first pump, in a case of activating both of the first hydraulic actuator and the second hydraulic actuator.

The articulated self-propelled work machine (1), such as, for example, an articulated telescopic handler or the like, comprises: a front frame (11), provided with a pair of front wheels (111); a lift arm (2), adapted to support a load, hinged to the front frame (11) and mobile with respect thereto by means of at least one actuator (21, 22); a rear frame (12), provided with a pair of rear wheels (121) and articulated to the front frame (11); detecting means (51, 53, 54) for detecting an angular parameter relative to a steering angle between the front frame (11) and the rear frame (12); and electronic processing means (6) configured to control the operation of the actuator (21, 22) on the basis of the angular parameter.

A work machine includes a boom, a work tool configured to drive with respect to the boom, an actuator configured to drive the work tool, a sub-link attached to the boom, and a control section. The sub-link is configured to transmit driving force of the actuator to the work tool. The control section is configured to control the actuator based on a posture of the sub-link with respect to the boom. A method of controlling a work machine includes controlling an actuator based on a posture of a sub-link with respect to a boom, the sub-link being configured to transmit driving force of the actuator to a work tool configured to drive with respect to the boom.

A hydraulic drive system for a hydraulic excavator that enables leveling work and a jack-up operation by a blade in a float state, that can prevent a body from falling even when an operator has falsely operated the hydraulic excavator during the jack-up operation by the blade, and that yet can perform favorable leveling work with the blade turned into the float state is provided. A float switch 37, a float valve 38, and a controller 34 are provided, the float valve 38 is changed over to a float position VI upon operating the float switch 37 when the blade is not in a jack-up state, the float valve 38 is changed over from the float position VI to a normal position V when the float valve 38 is in a state of being at the float position VI and an operation lever device 22 has been operated, and the float valve 38 is kept at the normal position V when the float valve 38 is at the normal position V and the float switch 37 has been operated in the jack-up state.