The present disclosure relates to a load dependent flow control system for directing hydraulic fluid to a hydraulic actuator. The load dependent flow control system includes a closed-center valve device for controlling hydraulic fluid flow to the actuator. The closed-center valve device includes a valve spool and an electro-actuator that adjusts a position of the valve spool to adjust a rate of the hydraulic fluid flow supplied to the hydraulic actuator. A pressure sensor is provided for sensing a pressure of the hydraulic fluid provided to the hydraulic actuator. The system also includes an electronic controller configured to receive an operator flow command from an operator interface. The operator flow command corresponds to a base flow through the closed-center valve device. The electronic controller interfaces with the electro-actuator of the closed-center valve device and with the pressure sensor. At least when the sensed pressure is above a threshold pressure, the electronic controller uses the operator flow command and the sensed pressure to generate a pressure-modified flow command that is sent to the closed-center valve device to control flow through the closed-center valve device. The pressure-modified flow command corresponds to a pressure-modified flow through the closed-center valve device. The pressure-modified flow is less than the base flow through the closed-center valve device.

A method and system for the hydraulic control of a concrete placing boom (14) comprising a plurality of boom arms (16), wherein hydraulic drive cylinders (18) for the boom arms (16), which are connected to one another in an articulated manner, are controlled by a hydraulic circuit (34), wherein a supply pressure is supplied via a hydraulic pump (32) to the hydraulic circuit (34), and wherein a pressure signal is captured in the drive cylinders (18) by at least one pressure sensor (38) for each cylinder. The maximum pressure in the drive cylinders (18) is determined from the pressure signals and the supply pressure is adjusted by an electronic control unit (36) according to the maximum pressure.

An actuation pressure to actuate one or more hydraulic actuators may be determined based on a load on the one or more hydraulic actuators of a robotic device. Based on the determined actuation pressure, a pressure rail from among a set of pressure rails at respective pressures may be selected. One or more valves may connect the selected pressure rail to a metering valve. The hydraulic drive system may operate in a discrete mode in which the metering valve opens such that hydraulic fluid flows from the selected pressure rail through the metering valve to the one or more hydraulic actuators at approximately the supply pressure. Responsive to a control state of the robotic device, the hydraulic drive system may operate in a continuous mode in which the metering valve throttles the hydraulic fluid such that the supply pressure is reduced to the determined actuation pressure.

A hydraulic system having a hydraulic pump, having a plurality of hydraulic loads and having a plurality of load-sensing valves for adjusting the pump performance of the hydraulic pump. An association unit is arranged between the hydraulic pump and the hydraulic loads and in a first switched state defines a first hydraulic path between the hydraulic pump and the hydraulic loads and in a second switched state defines a second hydraulic path between the hydraulic pump and the hydraulic loads. The system comprises a controller, which processes a state value of a hydraulic load as an input variable and which determines a control signal for the switched state of the association unit. The invention also relates to a method for controlling a hydraulic system.

To provide a construction machine that can highly precisely control branch flows from a hydraulic pump to a plurality of hydraulic actuators without being affected by load conditions. A controller (100) has a meter-out valve control section (140) configured to calculate a target opening area of a second meter-out valve (65a) (65b) according to a pressure difference between a supply pressure and a second meter-in pressure, or calculate a target opening area of a first meter-out valve (55a) (55b) according to a pressure difference between the supply pressure and the first meter-in pressure.

A hydraulic circuit having a function of compensation and energy recovery comprises a distribution module, a three-way compensated regulator device, a variable flow rate or pressure feeding assembly, an energy recovery device connected to the three-way compensated regulator device. The distribution module comprises a spool including an inlet recess and a drain recess configured so that the flow rate of fluid inlet to the utility is equal to or less than the one outlet therefrom, possibly net of a correction factor. There is also a respective first driving channel and a second driving channel configured so that a pressure taken upstream of the drain recess acts on a first side of the regulator device, and so that a pressure taken downstream of the drain recess in the first channel acts on a second side of the regulator device, and an additional force.

Flow control over a hydraulic pump and flow dividing control of a plurality of directional control valves associated with actuators can stably be exercised even in a case in which differential pressures across the directional control valves are quite low, an abrupt change in a flow rate of the hydraulic fluid supplied to each actuator is prevented and excellent combined operability is realized even in an abrupt change in a demanded flow rate at a time of transition from a combined operation to a sole operation, and realizing excellent combined operability, and a meter-in loss in each directional control valve is reduced to realize high energy efficiency. Demanded flow rates of the directional control valves are calculated from input amounts of operation levers, openings of flow control valves are controlled using the demanded flow rates, a meter-in pressure loss of a predetermined directional control valve is calculated from the demanded flow rates and meter-in opening areas of the directional control valves, and a set pressure of an unloading valve is controlled using a value of the meter-in pressure loss.

An actuation pressure to actuate one or more hydraulic actuators may be determined based on a load on the one or more hydraulic actuators of a robotic device. Based on the determined actuation pressure, a pressure rail from among a set of pressure rails at respective pressures may be selected. One or more valves may connect the selected pressure rail to a metering valve. The hydraulic drive system may operate in a discrete mode in which the metering valve opens such that hydraulic fluid flows from the selected pressure rail through the metering valve to the one or more hydraulic actuators at approximately the supply pressure. Responsive to a control state of the robotic device, the hydraulic drive system may operate in a continuous mode in which the metering valve throttles the hydraulic fluid such that the supply pressure is reduced to the determined actuation pressure.

Flow control over a hydraulic pump and flow dividing control of a plurality of directional control valves associated with actuators can stably be exercised even in a case in which differential pressures across the directional control valves are quite low, an abrupt change in a flow rate of the hydraulic fluid supplied to each actuator is prevented and excellent combined operability is realized even in an abrupt change in a demanded flow rate at a time of transition from a combined operation to a sole operation, and realizing excellent combined operability, and a meter-in loss in each directional control valve is reduced to realize high energy efficiency. Demanded flow rates of the directional control valves are calculated from input amounts of operation levers, openings of flow control valves are controlled using the demanded flow rates, a meter-in pressure loss of a predetermined directional control valve is calculated from the demanded flow rates and meter-in opening areas of the directional control valves, and a set pressure of an unloading valve is controlled using a value of the meter-in pressure loss.

A method and system for the hydraulic control of a concrete placing boom (14) comprising a plurality of boom arms (16), wherein hydraulic drive cylinders (18) for the boom arms (16), which are connected to one another in an articulated manner, are controlled by a hydraulic circuit (34), wherein a supply pressure is supplied via a hydraulic pump (32) to the hydraulic circuit (34), and wherein a pressure signal is captured in the drive cylinders (18) by at least one pressure sensor (38) for each cylinder. The maximum pressure in the drive cylinders (18) is determined from the pressure signals and the supply pressure is adjusted by an electronic control unit (36) according to the maximum pressure.