A servo actuator (1) comprises an actuator housing (4); an actuator member (2) located within the actuator housing (4) and at least one spool (8) located in a cavity (6) formed within the actuator housing (4). The housing (4) also comprises a first set of internal ports including an inlet port (P), an outlet port (T) and a pair of control ports (SI, S2), the inlet port (P) being arranged for connection to a first pressurised supply and a second set of internal ports comprising an inlet port (P), an outlet port (T) and a pair of control ports (SI, S2), the inlet port (P) being arranged for connection to a second pressurised supply. In use, movement of the spool (8) alters the flow path of fluid through the first and second set of internal ports to control the movement of the actuator member (2).

A hydraulic system for an aircraft having an engine and an auxiliary power unit includes a first hydraulic subsystem including a first hydraulic pump and a first set of hydraulic-powered components in fluid communication with the first hydraulic pump. The first hydraulic pump is powered by the engine to pump shared hydraulic fluid to the first set of hydraulic-powered components. The hydraulic system includes a second hydraulic subsystem including a second hydraulic pump and a second set of hydraulic-powered components in fluid communication with the second hydraulic pump. The second hydraulic pump is powered by the auxiliary power unit to pump the shared hydraulic fluid to the second set of hydraulic-powered components. A shared return line subsystem and reservoir is in fluid communication with the first and second hydraulic subsystems to return the shared hydraulic fluid to the first and second hydraulic pumps.

A method includes receiving pump cycle location data associated with a fluid power system. The fluid power system includes a plurality of pumps (including at least a first pump, a second pump, and a third pump). Based on the pump cycle location data having a first value, the method includes activating the first pump as a primary pump. Based on the pump cycle having a second value, the method includes activating the second pump as the primary pump. The method also includes activating the third pump as a secondary pump when the fluid power system is in a multiple-pump operating mode.

A method includes receiving pump cycle location data associated with a fluid power system. The fluid power system includes a plurality of pumps (including at least a first pump, a second pump, and a third pump). Based on the pump cycle location data having a first value, the method includes activating the first pump as a primary pump. Based on the pump cycle having a second value, the method includes activating the second pump as the primary pump. The method also includes activating the third pump as a secondary pump when the fluid power system is in a multiple-pump operating mode.

A spool for a hydraulic spool valve, comprising: a pressure chamber for connecting a pressure line to a hydraulic cylinder; at least one return chamber for connecting the hydraulic cylinder to a reservoir; and an actuator slot for receiving a drive lever; wherein the spool further comprises a fluid path connecting said pressure chamber to said actuator slot and a pressure plate movably mounted in the slot such that in use it is disposed between the fluid path and the drive lever.

A spool for a hydraulic spool valve, comprising: a pressure chamber for connecting a pressure line to a hydraulic cylinder; at least one return chamber for connecting the hydraulic cylinder to a reservoir; and an actuator slot for receiving a drive lever; wherein the spool further comprises a fluid path connecting said pressure chamber to said actuator slot and a pressure plate movably mounted in the slot such that in use it is disposed between the fluid path and the drive lever.

A hydraulic motor has a primary side and a secondary side. A hydraulic pump is to be driven by the engine to supply an operation fluid to the primary side. A bypass circuit is to connect the primary side and the secondary side. An electromagnetic valve is configured to control a flowing amount of the operation fluid in the bypass circuit to control an amount of the operation fluid supplied to the primary side. A filter is disposed in a fluid tube connected to the secondary side. A relief valve is disposed between the hydraulic pump and the primary side. A controller is to control the electromagnetic valve to drive the hydraulic motor in a case where a temperature of the operation fluid is low when the engine is started.

A hydraulic motor has a primary side and a secondary side. A hydraulic pump is to be driven by the engine to supply an operation fluid to the primary side. A bypass circuit is to connect the primary side and the secondary side. An electromagnetic valve is configured to control a flowing amount of the operation fluid in the bypass circuit to control an amount of the operation fluid supplied to the primary side. A filter is disposed in a fluid tube connected to the secondary side. A relief valve is disposed between the hydraulic pump and the primary side. A controller is to control the electromagnetic valve to drive the hydraulic motor in a case where a temperature of the operation fluid is low when the engine is started.

The present disclosure relates to an adjustment system a method for compensating for temperature variations in a spool valve. The spool valve and adjustment system may be parts in a duplex hydraulic actuator. The adjustment device comprises a spring, a pivot point, and a shape memory alloy (SMA) device. The spring and SMA device are disposed on either side of the pivot point to hold the pivot point in a first position. The SMA device is configured to change size in response to a temperature change so as move the pivot point to a second location. This may eliminate force fight in the duplex hydraulic actuator by preventing asynchronous activation of the spool valves due to thermal expansion within the spool valves.

Example embodiments may relate to a robotic system that includes a hydraulic actuator and an electric actuator both coupled to a joint of the robotic system. Operation of the actuators may be based on various factors such as based on desired joint parameters. For instance, such desired joint parameters may include a desired output torque/force of the joint, a desired output velocity of the joint, a desired acceleration of the joint, and/or a desired joint angle, among other possibilities. Given a model of power consumption as well as a model of the actuators, the robotic system may determine operating parameters such as hydraulic and electric operating parameters as well as power system parameters, among others. The robotic system may then control operation of the actuators, using the determined operating parameters, to obtain the desired joint parameters such that power dissipation in the system is minimized (i.e., maximizing actuation efficiency).