A propeller hydraulic actuation system, includes a double-acting dual chamber hydraulic pitch change actuator. The pitch change actuator includes a first pressure circuit having first fluid supply lines and a first hydraulic chamber and a second pressure circuit having second fluid supply lines and a second hydraulic chamber. A piston separates the first and second chambers. At least one pressure sensor is provided for obtaining pressure measurements from which a load differential (F) applied to the piston by the circuits can be calculated. A closed loop controller is arranged to control the fluid supplied to the first and second pressure circuits, wherein the closed loop controller includes an actuator position loop arranged to utilise feedback on the actuator position to control the actuator position.

A controller for a valve assembly that is configured to meet requirements for use in hazardous areas. These configurations may regulate flow of instrument air to a pneumatic actuator to operate a valve. The controller may comprise enclosures, including a first enclosure and a second enclosure, each having a peripheral wall forming an interior space, and circuitry comprising a barrier circuit disposed in the interior space of one of the enclosures that power limits digital signals that exits that enclosure. In one example, the peripheral wall of enclosures are configured to allow instrument air into the interior space of the first enclosure but to prevent instrument air from the interior space of the second enclosure.

In a closed loop control method for an electropneumatic field device, an electronic target value input of a command variable corresponding to a target value of a control center is received by the open loop and/or closed loop control electronics, an electronic output for a manipulating variable to pilot the electropneumatic converter is generated by the open loop and/or closed loop control electronics; and, in a predetermined operating condition of the field device, the manipulating variable is determined by a closed loop control algorithm based on the command variable and on another controlled variable different from an actual control member position measurement value.

An electropneumatic control apparatus, which has a carrier module, on which a control unit, which is equipped with control electronics and control valve elements, and an expansion module assembly, which has at least one expansion module, are installed independently of each other. By means of a drive fastening interface, the control apparatus can be installed on the actuating drive to be controlled, in order to form a process control device.

An electropneumatic controller has an electropneumatic control unit on which is provided an expansion interface, on which an expansion module arrangement is fitted. In the expansion module arrangement there extends at least one expansion working channel which is connected to a main working output and which is fluidically connected to the control unit at the expansion interface for connection to control valve means. The control unit further contains control electronics for electrically controlling the control valve means. Also proposed is a process control device equipped with a controller of this type.

A controller for a valve assembly that is configured to meet requirements for use in hazardous areas. These configurations may regulate flow of instrument air to a pneumatic actuator to operate a valve. The controller may comprise enclosures, including a first enclosure and a second enclosure, each having a peripheral wall forming an interior space, and circuitry comprising a barrier circuit disposed in the interior space of one of the enclosures that power limits digital signals that exits that enclosure. In one example, the peripheral wall of enclosures are configured to allow instrument air into the interior space of the first enclosure but to prevent instrument air from the interior space of the second enclosure.

Methods and apparatus are disclosed for automatically detecting the failure configuration of a pneumatic actuator. A control module is operatively coupled to the actuator, and the actuator is operatively coupled to a valve having a flow control member. When a number of pilot valves included in the control module is indicative of a double-acting actuator, the failure configuration of the actuator is determined based on the number of pilot valves. When the number of pilot valves included in the control module is indicative of a single-acting actuator, the failure configuration of the actuator is determined by comparing a first measurement value obtained in response to moving the flow control member in a first direction to a first position and a second measurement value obtained in response to moving the flow control member in a second direction opposite the first direction to a second position.

An adjustable electro-pneumatic converter or transducer based on the nozzle/baffle plate principle is proposed. A defined roughness (Rz) of the baffle plate surface can prevent the occurrence of Bernoulli forces at output pressures close to the initial pressure, i.e. when the exhaust nozzle (140) is almost completely closed by the baffle plate (100). The system thus becomes more dynamically controllable under these conditions. Such a converter can be used to control any consumer system, e.g. air power amplifiers for electro-pneumatic positioners.

A fluid valve assembly for controlling a single-acting or double-acting actuator comprises a valve body having a central bore with at least one supply port for receiving a supply of fluid under pressure, at least one actuator port (C1,C2) for providing a control fluid pressure to an actuator, and at least one exhaust port (EX1,EX2). At least one pair of counter-acting metering edges operationally tied together by a stem movable within central bore in an axial direction a pilot force. Each metering edge of each counter-acting pair comprises a mating seat surface (PS1,PS2,PS3,PS4) on the valve body or the stem, and a poppet ring (PR1,PR2, PR3,PR4) supported by a flexible element (SD1,SD2,SD3,SD4) to the valve body or the stem in a manner allowing a relative axial movement of the poppet ring and the supporting valve body or stem also in a closed state of the respective metering edge.

A positioner according to the present invention includes: an electro-pneumatic converter that converts an input electric signal into a pneumatic signal and controls the valve opening of a regulating valve by driving an operational unit in accordance with the pneumatic signal; an operating-point searching unit that changes the electric signal by performing open loop control to search for an operating point indicating a target valve-opening value of the regulating valve when an output air pressure of the pneumatic signal starts to change; and a PST executing unit that executes a PST on the regulating valve by using the operating point found by the operating-point searching unit. The operating-point searching unit sets the operating point based on a value of the electric signal when the output air pressure matches a first reference value.