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.

Systems and methods for control of multi-function hydraulic commands of a multi-function electrohydraulic system are provided. In one aspect, a system for hydraulic control includes a first function in fluid communication with a first electrohydraulic control valve and a second function in fluid communication with a second electrohydraulic control valve. The system includes a controller in communication with the first electrohydraulic control valve and the second electrohydraulic control valve. The controller can be configured to receive an input target command, determine an achievable function rate based on the input target command, where the achievable function rate maintains a proportional relationship between the input target command and the achievable function rate. The controller can also map the achievable function rate to an output command based on a predetermined relationship between the achievable function rates and the output commands and supply the output command to the first and second electrohydraulic valves.

A fluid circuit includes a pressure fluid source configured to supply pressure fluid, multiple actuators connected to the pressure fluid source, a direction switching valve configured to switch a supply destination of the pressure fluid supplied from the pressure fluid source, and a discharge amount control mechanism configured to control the output pressure of the pressure fluid source such that a pressure difference ΔP between the output pressure of the pressure fluid source and the maximum load pressure of the load pressures of the multiple actuators reaches a target value ΔPt. The fluid circuit further includes an accumulator configured to accumulate part of return fluid from the actuators.

A method controls the movement of a boom, wherein the boom is moved by a plurality of hydraulic drives. Each hydraulic drive is fed with a hydraulic medium, the pressure and/or volume flow of which is adjustable. The method predefines a desired direction of movement and a desired speed of a boom tip; predictively calculates a pressure and/or a volume flow required for each of the hydraulic drives that are required for the desired direction of movement and desired speed; subsequently generates a supply pressure depending on the predictively calculated pressures and/or subsequently generating a supply volume flow as a function of the predictively calculated volume flows; and subsequently feeds the hydraulic drives required for the desired direction of movement and desired speed with the hydraulic medium having a respective feed pressure and/or a respective feed volume flow such that the boom tip moves in the desired direction of movement at the desired speed.

Systems and methods for control of multi-function hydraulic commands of a multi -function electrohydraulic system are provided. In one aspect, a system for hydraulic control includes a first function in fluid communication with a first electrohydraulic control valve and a second function in fluid communication with a second electrohydraulic control valve. The system includes a controller in communication with the first electrohydraulic control valve and the second electrohydraulic control valve. The controller can be configured to receive an input target command, determine an achievable function rate based on the input target command, where the achievable function rate maintains a proportional relationship between the input target command and the achievable function rate. The controller can also map the achievable function rate to an output command based on a predetermined relationship between the achievable function rates and the output commands and supply the output command to the first and second electrohydraulic valves.

A shovel includes a lower traveling body, and an upper swiveling body mounted on the lower traveling body. The upper swiveling body is rotatable. An attachment is attached to the upper swiveling body. A traveling actuator is configured to drive the lower traveling body. An attachment actuator is configured to move the attachment. A control device is provided in the upper swiveling body. The control device is configured to autonomously operate at least one of the traveling actuator and the attachment actuator depending on an inclination of a ground on which the lower traveling body is traveling.

A marine hydraulic system and method of use for reducing cyclic loading of the pump(s) and motor(s) and an amount of accumulator storage required in a hydraulic system. A closed loop logic controller comprising at least one control algorithm for each pump/motor pair utilized in a single hydraulic system is utilized to reduce load fluctuations on the motors, allow the use of common pressure compensated, variable displacement (VDH) pumps, reduce the number and/or volume of system accumulators and equalize wear throughout the system.

A hydraulic excavator drive system includes: a first pump connected to a boom main control valve and an arm auxiliary control valve by a first pump line; a second pump connected to a boom auxiliary control valve and an arm main control valve by a second pump line; and a controller that does not move the arm auxiliary control valve when arm crowding operation boom raising operations are performed concurrently. The boom auxiliary control valve moves together with the boom main control valve when the boom raising operation is performed. A boom raising second supply line, which connects the boom auxiliary control valve to a boom raising first supply line between the boom main control valve and a boom cylinder, is provided with a check valve that allows a flow from the boom auxiliary control valve toward a head side of the boom cylinder, but prevents a reverse flow.

A time-based power boost control system. A fluid source supplies fluid. A relief device relieves pressure of the fluid supplied by the fluid source when the pressure of the fluid exceeds a relief pressure level. A control device controls the relief device. When a boost mode in which at least a first level of pressure and a second level of pressure, higher than the first level of pressure, are allowed to be selectively used as the relief pressure level is active, a length of a boost-on time in which the second level of pressure is used as the relief pressure level is shorter than a preset maximum boost-on time limit, and a length of a succeeding boost-off time succeeding the boost-on time in which the first level of pressure is used as the relief pressure level is equal to or longer than a preset minimum boost-off time limit.

Even where the differential pressure across a directional control valve associated with each actuator is very small, flow dividing control of the plurality of directional control valves can be performed stable, and even where a demanded flow rate suddenly changes at the time of transition from composite action to single action or the like, a sudden change of the flow rate of hydraulic fluid to be supplied to each actuator is prevented to implement superior combined operability. Further, the meter-in loss of the directional control valves can be reduced to implement a high energy efficiency. To this end, a plurality of pressure compensating valves 7a, 7b and 7c for controlling such that the pressure in the downstream side of the meter-in opening of a plurality of directional control valves 6a, 6b and 6c becomes equal to the highest load pressure are individually arranged in the downstream side of meter-in openings of the plurality of directional control valves 6a, 6b and 6c, and demanded flow rates for the directional control valves 6a, 6b and 6c are calculated from input amounts of operation levers. Besides, the meter-in pressure loss of a predetermined directional control valve is calculated from the demanded flow rates for and meter-in opening areas of the directional control valves 6a, 6b and 6c, and the set pressure of the unloading valve 15 is controlled using the value of the meter-in pressure loss.