A system including a pneumatic actuator having an actuator element, the system further including a compressed-air provision device which is configured to carry out a closed-loop position control of the actuator element by applying compressed air to the pneumatic actuator. The compressed-air provision device is further configured to carry out an assistance procedure in which the actuator element is set in an oscillation movement, pressure values and position values are detected, and, on the basis of the detected pressure values and the detected position values, friction information and/or mass information is determined and/or verified.

A servo valve for precisely controlling a position of a pneumatic cylinder does not require a servo amplifier and a small sized and/or high durability servo valve unit. The servo valve comprises a unit body having first and second portions, first and second valve portions, first and second seal members that open and close the first and second valve portions, respectively, first and second drive mechanisms that drive first and second seal members by first and second electric pulses, respectively, a supply flow path between the first end and first valve, an exhaust flow path between the second end and second valve, a common flow path connected to the supply and exhaust flow paths via first and second valve portions, and a drive flow path connected to the pneumatic actuator. First and second drive mechanisms are arranged in a drive mechanism arrangement portion located between first and second end portions.

A servo valve for precisely controlling a position of a pneumatic cylinder does not require a servo amplifier and a small sized and/or high durability servo valve unit. The servo valve comprises a unit body having first and second portions, first and second valve portions, first and second seal members that open and close the first and second valve portions, respectively, first and second drive mechanisms that drive first and second seal members by first and second electric pulses, respectively, a supply flow path between the first end and first valve, an exhaust flow path between the second end and second valve, a common flow path connected to the supply and exhaust flow paths via first and second valve portions, and a drive flow path connected to the pneumatic actuator. First and second drive mechanisms are arranged in a drive mechanism arrangement portion located between first and second end portions.

The subject matter of this specification can be embodied in, among other things, a fluid valve assembly that includes a first fluid port, a second fluid port, a third fluid port, a valve spool configured to be positioned at a first position, a second position away from the first position, a third position away from the first position opposite the second valve position, the valve spool defining a first fluid duct configured to fluidly connect the first fluid port to the second fluid port in the first valve position, a second fluid duct configured to fluidly connect the first fluid port to the third fluid port in the second valve position, and a third fluid duct configured to fluidly connect the first fluid port to the second fluid port in the third valve position.

The subject matter of this specification can be embodied in, among other things, a fluid valve assembly that includes a first fluid port, a second fluid port, a third fluid port, a valve spool configured to be positioned at a first position, a second position away from the first position, a third position away from the first position opposite the second valve position, the valve spool defining a first fluid duct configured to fluidly connect the first fluid port to the second fluid port in the first valve position, a second fluid duct configured to fluidly connect the first fluid port to the third fluid port in the second valve position, and a third fluid duct configured to fluidly connect the first fluid port to the second fluid port in the third valve position.

A hydraulic circuit includes a pump connected to a tank for supplying hydraulic liquid under pressure to a component via a directional control slide valve provided with a feed port connected to an inlet of the component and with a return port connected to an outlet of the component. The hydraulic circuit further includes a pressure limiter connected to the inlet of the component and the tank, and a feed control system for the hydraulic component including a pressure sensor installed upstream of the hydraulic component downstream of the feed port for supplying information about the pressure of the hydraulic liquid and a setpoint pressure. The feed control system further including an actuator for controlling the movement of the directional control slide valve, and a control unit for generating a control signal for the actuator based on information about the pressure measured at the feed port.

An example robot includes a hydraulic actuator cylinder controlling motion of a member of the robot. The hydraulic actuator cylinder comprises a piston, a first chamber, and a second chamber. A valve system controls hydraulic fluid flow between a hydraulic supply line of pressurized hydraulic fluid, the first and second chambers, and a return line. A controller may provide a first signal to the valve system so as to begin moving the piston based on a trajectory comprising moving in a forward direction, stopping, and moving in a reverse direction. The controller may provide a second signal to the valve system so as to cause the piston to override the trajectory as it moves in the forward direction and stop at a given position, and then provide a third signal to the valve system so as to resume moving the piston in the reverse direction based on the trajectory.

An example robot includes a hydraulic actuator cylinder controlling motion of a member of the robot. The hydraulic actuator cylinder comprises a piston, a first chamber, and a second chamber. A valve system controls hydraulic fluid flow between a hydraulic supply line of pressurized hydraulic fluid, the first and second chambers, and a return line. A controller may provide a first signal to the valve system so as to begin moving the piston based on a trajectory comprising moving in a forward direction, stopping, and moving in a reverse direction. The controller may provide a second signal to the valve system so as to cause the piston to override the trajectory as it moves in the forward direction and stop at a given position, and then provide a third signal to the valve system so as to resume moving the piston in the reverse direction based on the trajectory.

The subject matter of this specification can be embodied in, among other things, a controller apparatus that includes a digital controller configured to provide a digital position signal based on a setpoint and a differential analog feedback signal, and a converter circuit configured to provide a differential analog electrohydraulic servo valve position control signal based on the digital position signal, and provide the differential analog feedback signal based on the differential analog electrohydraulic servo valve position control signal.

The subject matter of this specification can be embodied in, among other things, a controller apparatus that includes a digital controller configured to provide a digital position signal based on a setpoint and a differential analog feedback signal, and a converter circuit configured to provide a differential analog electrohydraulic servo valve position control signal based on the digital position signal, and provide the differential analog feedback signal based on the differential analog electrohydraulic servo valve position control signal.