Method and device for detecting a fault in a valve control device and / or recovering from a fault in a valve control device

Abstract

An apparatus includes an input signal generator that provides a digital input signal to a first translator. The first translator corresponds to one of a supply translator or a drain translator. The supply translator controls actuation of a supply relay to deliver pressurized fluid to an actuator that is operably coupled to a valve in a process control system. The drain translator controls actuation of a drain relay to drain pressurized fluid from the actuator. The digital input signal triggers application of a current to the first translator to open the first translator. The apparatus also includes a fault detector to: determine a difference in at least one of a pressure in the actuator or a position of a flow control member in the valve; and detect a fault when the difference satisfies a fault threshold.

Description

Technical Field

[0001] The present disclosure relates generally to valve controllers and, more particularly, to methods and apparatus for detecting and / or recovering from faults in valve control devices. Background Art

[0002] Control valves (e.g., sliding stem valves, rotary valves, axial flow valves, ball valves, etc.) are commonly used in industrial processes, such as oil and gas pipeline distribution systems and chemical processing plants, to control the flow of process fluids. These control valves are typically automated using pressure-operated actuators controlled by remotely operated field instruments or control devices. The field instruments communicate with the process control computer to command changes in fluid flow within the valve, thereby achieving the desired control strategy through the pressure-operated actuators. Electro-pneumatic converters, such as current-to-pressure (I / P) converters, are commonly used in field instruments to provide conversion of signals to volumetric flow or pressure outputs to control the actuators and, therefore, the control valves. Summary of the Invention

[0003] The example device disclosed herein includes an input signal generator for providing a digital input signal to a first converter at a first point in time. The first converter corresponds to one of a supply converter or a discharge converter. The supply converter controls the actuation of a supply relay to deliver pressurized fluid to an actuator, which is operably coupled to a valve in a process control system. The discharge converter controls the actuation of a discharge relay to discharge pressurized fluid from the actuator. The digital input signal triggers the application of current to the first converter to open the first converter. The device also includes a fault detector for: determining a difference in at least one of the pressure in the actuator or the position of the flow control member in the valve for a time period after the first point in time; and detecting a fault in at least one of the supply converter, the discharge converter, the supply relay, or the discharge relay when the difference meets a fault threshold.

[0004] Some example instructions disclosed herein, when executed, cause a machine to provide a digital input signal to a first converter at least at a first point in time. The first converter corresponds to one of a supply converter or a discharge converter. The supply converter controls actuation of a supply relay to deliver pressurized fluid to an actuator, which is operably coupled to a valve in a process control system. The discharge converter controls actuation of a discharge relay to discharge pressurized fluid from the actuator. The digital input signal triggers application of a current to the first converter to open the first converter. The example instructions also cause the machine to determine a difference in at least one of a pressure in the actuator or a position of a flow control member in the valve for a time period after the first point in time. The example instructions also cause the machine to detect a fault in at least one of the supply converter, the discharge converter, the supply relay, or the discharge relay when the difference meets a fault threshold.

[0005] The example method includes providing a digital input signal to a first converter at a first point in time. The first converter corresponds to one of a supply converter or a discharge converter. The supply converter controls the actuation of a supply relay to deliver pressurized fluid to an actuator, which is operably coupled to a valve in a process control system. The discharge converter controls the actuation of a discharge relay to discharge pressurized fluid from the actuator. The digital input signal triggers the application of current to the first converter to open the first converter. The example method also includes determining a difference in at least one of a pressure in the actuator or a position of a flow control member in the valve for a time period after the first point in time. The example method also includes detecting a fault in at least one of the supply converter, the discharge converter, the supply relay, or the discharge relay when the difference meets a fault threshold. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a schematic diagram of an example process control system including an example control device constructed according to the teachings disclosed herein.

[0007] Figure 2 Shows the implementation Figure 1 An example control device and an example logic circuit device are provided.

[0008] Figure 3 It means that it can be executed to achieve Figure 1 and / or Figure 2 A flow chart of example machine readable instructions for an example logic circuit device.

[0009] Figure 4 is constructed to execute Figure 3 Example instructions to implement Figure 1 and / or Figure 2 A block diagram of an example processing platform of an example logic circuit device.

[0010] The drawings are not drawn to scale. Generally, the same reference numerals are used throughout the drawings and the accompanying written description to represent the same or similar parts. As used in this patent, stating that any part (e.g., a layer, film, region, area, or plate) is in any way on another part (e.g., positioned on another part, set on another part, arranged on another part, or formed on another part, etc.) indicates that the mentioned part is in contact with the other part, or the mentioned part is above the other part, with one or more intermediate parts located therebetween. Unless otherwise specified, connection references (e.g., attachment, coupling, connection, and engagement) should be interpreted broadly and may include intermediate members between a set of elements and relative movement between elements. Similarly, connection references do not necessarily imply that two elements are directly connected and are in a fixed relationship to each other. Stating that any part is "in contact" with another part means that there is no intermediate part between the two parts.

[0011] The descriptors "first," "second," "third," etc., are used herein to identify multiple elements or components that can be referred to individually. Unless otherwise specified or understood based on the context of their use, such descriptors are not intended to imply any meaning of priority, physical order or arrangement in a list, or chronological order, but are merely used as labels to individually reference multiple elements or components to facilitate understanding of the disclosed examples. In some examples, the descriptor "first" may be used to refer to an element in the detailed description, while the same element may be referred to by a different descriptor, such as "second" or "third," in the claims. In such cases, it should be understood that the use of such descriptors is merely for convenience in referencing multiple elements or components. DETAILED DESCRIPTION

[0012] Certain field instruments and / or control devices (e.g., current-to-pressure (I / P) converters, digital valve controllers (DVCs)) are configured to control the operation of a pneumatic actuator that causes a control valve to change its operating state or position (e.g., fully open, fully closed, and / or any suitable intermediate position therebetween). Typically, such control devices include an electro-pneumatic converter (also known as an electro-pneumatic transducer, a latching pneumatic converter, or a current-to-pressure (I / P) converter) to convert an electrical input signal into a pneumatic pressure signal that actuates the pneumatic actuator to move the control valve in a desired manner. As used herein, references to moving a control valve, changing the position of a control valve, and other similar phrases refer to movement of a flow control member (e.g., a ball, disk, plug, etc.) within the valve relative to the body of the valve (e.g., by rotation, by linear translation, etc.). Similarly, as used herein, references to movement or change of the position of an actuator refer to changes in the actuator's actuating mechanism to cause a corresponding change in the position or movement of the flow control member of the associated control valve. Furthermore, for the sake of brevity, the term "converter" is used herein interchangeably with the term "electro-pneumatic converter."

[0013] In many cases, the electrical input signal provided to the electro-pneumatic converter corresponds to and / or is based on a control signal from a controller or other device in an associated process control system. More specifically, in some cases, the control signal can be provided directly to the electro-pneumatic converter for direct conversion from an electrical signal to a pneumatic signal. In other cases, the control signal defines a set point that is analyzed relative to sensor feedback data by a logic circuit device (e.g., a microprocessor) within a control device containing the electro-pneumatic converter. In this case, the logic circuit device generates an appropriate input signal for the electro-pneumatic converter based on an error specified by the difference between the set point and the sensor feedback data. The sensor feedback data may include pressure feedback data indicating the current pressure in the associated actuator and / or position feedback data indicating the current position of the corresponding control valve.

[0014] Typically, a control device for operating a pneumatic actuator also includes a relay or amplifier operably coupled to the electro-pneumatic converter to increase or amplify the output pressure and / or flow rate of the fluid to the pneumatic actuator to facilitate actuation or movement of the control valve. That is, in some examples, an electrical input signal is provided to the control device to drive the electro-pneumatic converter, and the converter's output activates the relay, which in turn provides a pneumatic output to the pneumatic actuator.

[0015] Historically, the electrical input signal provided to a control device for operating a pneumatic actuator has been an analog signal capable of proportionally controlling the output of an electro-pneumatic converter of the control device. For example, the electrical input signal provided to the converter may correspond to a signal having a continuous current varying between 4 mA and 20 mA. In such an example, a particular output of the converter (and therefore a corresponding pressure output to the pneumatic actuator) is based on (e.g., proportional to) the current value along a calibrated range (e.g., from 4 mA to 20 mA), with one end of the range corresponding to a fully closed position of the valve and the opposite end of the range corresponding to a fully open position.

[0016] Unlike such historical control devices, the example control devices disclosed herein are implemented using a digital (on / off) electro-pneumatic converter controlled based on a digital (on / off) input signal. More specifically, the electrical input signal used to drive the electro-pneumatic converter in the example control devices disclosed herein corresponds to a digital signal having discrete values ​​that define when the converter is in a closed state (sometimes referred to as closed or unlocked) and an open state (sometimes referred to as open or latched). In the closed state, pressurized fluid is not provided downstream of the converter (e.g., to a relay and / or actuator). In the open state, pressurized fluid is allowed to flow downstream of the electro-pneumatic converter. In some examples, a first input signal indicating that the converter is to be in the open state causes a first current to be applied to the converter to open the converter. In some examples, the first current continues to be applied to the converter to maintain it in the open state until a second input signal is provided to shut down the converter and return it to the closed state. In some examples, the second input signal causes a second current to be applied to the converter to shut down the converter. Additionally or alternatively, in some examples, the converter may have a default state, wherein when no current is applied, the converter remains in the default state (or returns to the default state). For example, a first input signal can cause a first current to be applied to the converter to switch the converter to an open state, thereby allowing the flow of pressurized fluid. A second input signal can remove the application of the first current, so that no current is applied to the converter. In some such examples, the converter can automatically revert to a closed state. In some such examples, even when the converter is configured to have a default state in which it automatically closes when no current is applied, the second signal can cause a second current to be applied to the converter to close the converter.

[0017] Some example control devices include two independent electro-pneumatic converters controlled by corresponding digital (on / off) input signals. In some such examples, the first converter is referred to herein as a supply electro-pneumatic converter (or supply converter), and the second converter is referred to herein as an exhaust electro-pneumatic converter (or exhaust converter). In some examples, the control device also includes a first (supply) relay pneumatically coupled to the supply converter and a second (exhaust) relay pneumatically coupled to the exhaust converter. In the examples disclosed herein, the supply converter and the supply relay cooperate to supply or provide pressurized fluid to the actuator to actuate the valve to move in a first direction toward a first state (e.g., toward a fully closed position or toward a fully open position). Conversely, the exhaust converter and the exhaust relay cooperate to discharge or remove pressurized fluid from the actuator to actuate the valve to move away from the first state (e.g., away from a fully closed position or away from a fully open position) in a second direction.

[0018] Implementing a control device using a digital (on / off) converter means that the converter only produces one of two outputs (providing pressure (when in an open state) or not providing pressure (when in a closed state)), making direct proportional control impossible. Therefore, in some examples, the operation of a pneumatic actuator is controlled via the example control device disclosed herein based on the timing of the supply and exhaust converters switching between their open and closed states. More specifically, in some examples, the amount of time that the supply converter needs to be open to apply pressure to the actuator is calculated. An initial input signal is then provided to the supply converter to trigger the application of a first current to cause the supply converter to open. The supply converter remains open for the calculated amount of time, and then a second input signal is provided to disconnect the first current and / or apply a second current to cause the converter to close. Based on sensor feedback data indicating the actual (e.g., measured) pressure in the actuator and / or the actual (e.g., measured) position of the associated control valve, the amount of time that the supply converter or exhaust converter is open can be calculated and / or updated in substantially real time.

[0019] In some examples, the converter can switch between an open (on) state and a closed (off) state relatively quickly to provide small increments of pressurized fluid to the actuator or remove small increments of pressurized fluid from the actuator. The relatively rapid switching between the states of the two converters allows for relatively high precision in actuation. In some examples, a changing digital input signal can be provided to either the supply or exhaust converter to frequently open or close the corresponding converter every 50 milliseconds (e.g., providing up to 20 different digital input signals per second). In other examples, the digital signal can be provided at a rate greater than or less than 20 times per second. However, in some examples, due to power budget constraints on the control device, the option of providing control signals at a more frequent rate is not available.

[0020] As described above, in some examples, a single input signal can switch the converter to an open position, which remains in that state for any relevant time period until a second input signal causes the converter to close. In some examples, the converter is maintained in the open position based on a continuously applied current. However, in some examples, the amount of current required to maintain the converter in the open position is less than the amount of current required to initially open the converter. Thus, in some examples, a single input signal can trigger the application of a first (relatively high) current to initially open the converter, and then apply a second (reduced) current for the remaining duration that the converter will be open (e.g., until pressurized fluid is added to or discharged from the actuator sufficient to move the valve to the desired set point). Applying a reduced current to maintain the converter in the open position reduces the overall power consumption of the device because the higher current to open the converter is only required for a relatively short period of time when the input signal is first provided to open the converter.

[0021] While the above approach reduces power requirements, there may be situations where the converter fails to turn on in response to an initial high current, which is applied before the current decreases over the duration that the converter will turn on. If the converter does not turn on when the high current is applied, the converter will not subsequently turn on even if a lower current is applied because the lower current is insufficient to turn on the converter. Therefore, the example control device disclosed herein monitors sensor feedback data (e.g., position and / or pressure data) over time to detect potential faults in the intended operation of the control device. If a fault is detected, the control device can automatically provide a new input signal to the appropriate converter, which again triggers the high current required to switch the state of the converter in an attempt to resolve the fault condition and restore the device to normal operation. A situation in which an example control device temporarily fails and therefore fails to operate as expected in response to a particular input signal, and then subsequently begins operating as expected in response to a similar input signal at a later point in time without any direct intervention by maintenance personnel is referred to herein as an intermittent fault. Conversely, a situation in which an example control device stops operating and does not return to normal operation after a threshold period of time despite providing additional input signals to drive the operation of the control device is referred to herein as a complete fault.

[0022] There are different ways in which an example control device may fail (intermittently or completely). As described above, a converter may fail to respond to a particular input signal for switching the converter state. Even if the converter operates as expected in response to the input signal, the corresponding relay may fail to open or close in response to the opening or closing of the corresponding converter. In other words, any one of the supply converter, the exhaust converter, the supply relay, or the exhaust relay may not be functioning properly and be the basis for the detected fault. In some examples, it may not be known which component caused a particular detected fault. Therefore, as disclosed in more detail below, in some examples, different procedures are implemented to attempt to recover from a detected fault that describes different potential sources of the fault.

[0023] An exemplary control device may exhibit one or more intermittent faults that occur before and / or lead to a complete failure. As such, tracking and / or monitoring intermittent faults can be a useful diagnostic tool in methods for predicting complete failure of a control device. Methods for predicting complete failure of a control device can enable maintenance personnel to take appropriate action at a more convenient and / or cost-effective time. For example, if maintenance personnel are aware that a control device is beginning to malfunction (e.g., has been malfunctioning intermittently) but has not yet exhibited a complete failure, the personnel can replace the affected equipment during a scheduled maintenance period prior to the complete failure. In contrast, if intermittent faults are not tracked or detected, personnel may be surprised when equipment fails completely at an inappropriate time, resulting in an unscheduled shutdown of the process control system to allow the equipment to be replaced. Therefore, as further disclosed herein, an exemplary control device tracks and / or monitors faults in the operation of any of the supply converter, the exhaust converter, the supply relay, and the exhaust relay. Furthermore, in some examples, detection of such a fault is reported to a processor controller and / or triggers an alarm, which is provided to an operator, maintenance personnel, and / or other individuals to take appropriate responsive action.

[0024] Figure 1 is a schematic diagram of an example process control system 100 including an example control device 102 constructed according to the teachings disclosed herein. In this example, the control device 102 includes an example supply electro-pneumatic converter 104, an example exhaust electro-pneumatic converter 106, an example supply relay 108, an example exhaust relay 110, an example position sensor 112, an example pressure sensor 114, and an example logic circuit device 116. In some examples, the logic circuit device 116 is implemented by one or more analog or digital circuits, logic circuits, programmable processors, programmable controllers, microcontrollers, graphics processing units (GPUs), digital signal processors (DSPs), application specific integrated circuit devices (ASICs), programmable logic devices (PLDs), and / or field programmable logic devices (FPLDs).

[0025] As shown in the illustrated example, the supply converter 104 is pneumatically coupled to a first pressure supply source 118, the exhaust converter 106 is pneumatically coupled to a second pressure supply source 120, and the supply relay 108 is pneumatically coupled to a third pressure supply source 122. The pressure supply sources 118, 120, 122 can be, for example, plant air (e.g., compressed fluid such as air or natural gas distributed through a process plant), pressurized fluid from a fluid handling system, and / or pressurized fluid from any other fluid source. In some examples, one or more of the first, second, and / or third pressure supply sources 118, 120, 122 correspond to a single pressure supply source. In some examples, the third pressure supply source 122 coupled to the supply relay 108 corresponds to a relatively high pressure supply, while the first and second pressure supply sources 118, 120 coupled to the converters 104, 106 correspond to two separate or a single relatively low pressure supply. In some examples, the relatively low pressure supplies provided by the first and second pressure supplies 118 , 120 are drawn from a relatively high pressure supply 122 and regulated to a relatively low pressure.

[0026] In the illustrated example, the logic circuitry 116 generates an input signal that causes an electrical current to be applied to the supply switch 104 to switch the supply switch 104 to an open position. More specifically, in some examples, the supply switch 104 includes a solenoid having a coil wound around a core positioned adjacent to a movable armature. In some such examples, the coil can be electrically activated (e.g., by an applied electrical current triggered by the input signal) to cause the armature within the switch 104 to move between a first (closed) position and a second (open) position closer to the core of the solenoid. In some examples, the armature in the closed position prevents pressurized fluid from flowing between a supply port (e.g., pneumatically coupled to the first pressure supply source 118) and an outlet port of the supply switch 104 (e.g., pneumatically coupled to the supply relay 108). In contrast, in some examples, the armature in the open position allows pressurized fluid (e.g., from the first pressure supply source 118) to pass between the supply port and the outlet port toward the supply relay 108.

[0027] In some examples, the logic circuit device 116 initially applies a higher current to the solenoid within the supply converter 104 to move the armature to the open position, and then reduces the current to a lower current. Once the armature moves closer to the core of the solenoid (based on the higher current), less magnetic force is required to hold the armature in the second position. Therefore, less current is required to generate a magnetic field sufficient to hold the armature in place in the open position. Therefore, in some examples, once the armature is moved to the open position, the logic circuit device 116 reduces the current, thereby reducing the total power consumed by the converter 104.

[0028] In some examples, after the supply current has been maintained in the open position for an appropriate amount of time (determined by the control logic of the control device 102), the logic circuit device 116 provides a second input signal to the supply switch 104 to switch the supply switch 104 to the closed position. In some examples, this input signal reduces the current applied to the supply switch 104 to zero, wherein the armature is urged to the closed position by the biasing spring. Additionally or alternatively, in some examples, the input signal causes another current to be applied in the reverse direction to the coil of the solenoid in the switch 104 to facilitate movement of the armature to the closed position. In some such examples, the current is provided for a relatively short period of time because the biasing spring within the switch 104 will maintain the armature in the closed position after the reverse current is removed.

[0029] As described above, when the supply switch 104 is open, pressurized fluid from the first pressure supply source 118 is supplied to the supply relay 108 to move an actuating member within the supply relay 108, which opens the supply relay 108 such that an input port of the supply relay 108 is in fluid communication with an output port of the supply relay 108. In some examples, the input port of the supply relay 108 is pneumatically coupled to the third pressure supply source 122, and the output port of the relay 108 is pneumatically coupled to the pneumatic actuator 124. Therefore, when the supply switch 104 is in the open state, pressurized fluid from the first pressure supply source 118 causes the supply relay 108 to move to the open state, thereby providing pressurized fluid from the third pressure supply source 122 to the pneumatic actuator 124. Conversely, when the supply switch 104 is in the closed state (in response to the applied current being reduced to zero or in response to a reverse current flow triggered by another input signal from the logic circuitry 116), the pressurized fluid is prevented from reaching the supply relay 108, causing the supply relay 108 to move to the closed state (e.g., due to a biasing spring). When the supply relay 108 is in the closed state, the pressurized fluid from the third pressure supply source 122 is prevented from reaching the pneumatic actuator 124.

[0030] In some examples, the bleed converter 106 and the bleed relay 110 are constructed and function in a substantially similar manner to the supply converter 104 and the supply relay 108, except that the bleed relay 110 is arranged to bleed or remove pressurized fluid from the pneumatic actuator 124. More specifically, in some examples, the logic circuitry 116 provides an input signal to the bleed converter 106 to switch the bleed converter 106 to an open state, thereby opening the bleed relay 110 and bleed pressurized fluid from the actuator 124. In some examples, the input signal provided to the bleed converter 106 triggers an initial current to move the armature within the bleed converter 106 toward the solenoid. Once the armature has moved to the open position, the initial current is reduced to a lower second current, as desired, to maintain the armature in the open position, according to the control logic of the operating control 102. When the bleed converter 106 is open, pressurized fluid from the second pressure supply source 120 is provided to the bleed relay 110, causing it to open, thereby enabling the pressurized fluid to be bleed from the pneumatic actuator 124. When the bleed switch 106 is closed (e.g., in response to another input signal to close the bleed switch 106), pressurized fluid from the second pressure supply source 120 is prevented from reaching the bleed relay 110. As a result, the bleed relay 110 will move to a closed state (e.g., due to a biasing spring), thereby preventing pressurized fluid from being discharged from the pneumatic actuator 124.

[0031] Based on the fluid pressure added to the actuator 124 (when the supply switch 104 and the supply relay 108 are open) and / or removed from the actuator 124 (when the exhaust switch 106 and the exhaust relay 110 are open), the pneumatic actuator 124 actuates or moves the associated control valve 126. In some examples, the pneumatic actuator 124 is a single-acting actuator. In some examples, the pneumatic actuator 124 is a double-acting actuator.

[0032] In some examples, logic circuitry 116 determines whether to provide an input signal to open (or close) converters 104, 106 and how long each converter remains in the closed or open state based on sensor feedback data compared to a set point defining a specific position of control valve 126. In some examples, the set point is defined by a control command received from a remote process controller 128 in communication with logic circuitry 116. In some examples, the set point is provided via a different device (e.g., a handheld field device) in communication with control device 102. In some examples, the set point is provided by a user entering the set point via a user interface on control device 102.

[0033] In some examples, the sensor feedback data includes position feedback data generated by the position sensor 112, which measures the rotational and / or linear motion of the pneumatic actuator 124 and / or the control valve 126. Additionally or alternatively, in some examples, the sensor feedback data includes pressure feedback data generated by a pressure sensor that measures the pressure within the pneumatic actuator 124, which is operatively coupled to the control valve 126. Figure 1 The example control device 102 is shown as including both a position sensor 112 and a pressure sensor 114, but in some examples, one or both of the position sensor 112 and the pressure sensor 114 are implemented separately from the control device 102 (e.g., external to the control device 102 but communicatively coupled thereto). In some examples, the position sensor 112 or the pressure sensor 114 is omitted entirely, such that the feedback sensor data is exclusively limited to position feedback data or pressure feedback data. In some examples, the control device 102 includes and / or communicates with more than one position sensor 112 and / or more than one pressure sensor 114.

[0034] In some examples, the amount of error in the position and / or pressure measurements relative to the set point determines the duration that the supply switch 104 or the exhaust switch 106 is open to supply pressurized fluid to or exhaust pressurized fluid from the actuator 124. Furthermore, the direction of the error relative to the set point (e.g., whether it is high or low) determines which of the supply switch 104 or exhaust switch 106 is open. In some examples, the input signals for opening and / or closing each of the switches 104, 106 can be provided in a relatively rapid sequence (e.g., a new input signal approximately every 50 ms) to add or remove relatively small increments of pressurized fluid from the actuator 124 for relatively precise control. Of course, when moving the valve 126 from one position to a different position, there may be relatively long periods of time (e.g., greater than 1 second) during which pressurized fluid is supplied to or exhausted from the pneumatic actuator 124.

[0035] For purposes of explanation, the time period during which the logic circuitry 116 directs the supply switch 104 (and, therefore, the supply relay 108) to open is referred to herein as a supply action of the example control device 102. In contrast, the time period during which the logic circuitry 116 directs the bleed switch 106 (and, therefore, the bleed relay 110) to open is referred to herein as a bleed action of the example control device 102. As described above, the supply action or bleed action can last for any relevant time period determined by the logic circuitry 116 to cause the pressure in the actuator 124 and / or the position of the actuator 124 (and / or the associated valve 126) to conform to a setpoint defining a desired position for the control valve 126. In some examples, the supply action or bleed action is triggered by a single input signal to the corresponding supply switch 104 or bleed switch 106, which directs the corresponding switch to switch to an open state. In some examples, an input signal for opening a supply switch 104 or a drain switch 106 triggers a first current that is applied to the solenoid of the corresponding switch 104, 106 for a first (relatively short) period of time to initially move the armature of the solenoid in the switch 104, 106 toward the open position, thereby placing the switch in the open state. Thereafter, a second current, less than the first current, is applied to the solenoid for the remainder of the supply or drain action to maintain the switch in the open state. Thus, in some examples, the entire duration of the supply or drain action is achieved in response to a single input signal to the appropriate switch 104, 106. In some examples, when the supply or drain action ends, the logic circuit device 116 provides a subsequent input signal to the corresponding switch 104, 106 to switch the switch to the closed state (e.g., by triggering a third current applied to the solenoid in a direction opposite to the first and second currents or simply stopping the application of current to the solenoid).

[0036] The above-described method reduces the power requirements for implementing the control device because the relatively high current (e.g., the first current) required to activate or turn on the converters 104, 106 is limited to the initial opening of the converters, and then a reduced current (e.g., the second current) is applied thereafter. In some examples, the high current is approximately 3 mA and the low or reduced current is approximately 1 mA. In some examples, the lower current is insufficient to open the corresponding converter 104, 106 from the closed position. Therefore, if either converter 104, 106 fails to open in response to the relatively brief application of the high current, the converter 104, 106 will not be able to subsequently open despite the continued application of the lower current thereafter. Therefore, in some examples, a failure in the intended operation of the example control device 102 is detected, so that a subsequent input signal can be provided to re-initiate appropriate action (e.g., reapplying a high current to attempt to open the particular converter 104, 106 before again reducing the applied current to a low current to maintain the converter in the open state).

[0037] As described above, detecting and attempting to recover from and / or correct a fault in the intended operation of control device 102 is important because otherwise the control device may become stuck indefinitely in a supply or exhaust action. As an example, assume that sensor feedback data (whether position data and / or pressure data) indicates that pressurized fluid needs to be added to pneumatic actuator 124 to move valve 126 toward the position defined by the current set point. Therefore, logic circuitry 116 determines that a supply action is required and, accordingly, provides an input signal to supply switch 104 to switch supply switch 104 to an open state, thereby causing supply relay 108 to also open and supply pressurized fluid to actuator 124. If control device 102 is functioning properly, actuator 124 will be pressurized, thereby moving control valve 126 toward the set point, as indicated by changes or differences in the sensor feedback data over time. Once the sensor feedback data indicates that valve 126 has moved to the desired position, the supply action can be terminated by providing a new input signal to close supply switch 104. However, if the control device 102 is not functioning properly (e.g., the supply switch 104 does not open in response to the initial input signal to begin the supply action), the pressure intended to move the control valve 126 will not be supplied to the actuator 124. As a result, the control valve 126 will not move as intended, and the sensor feedback data will continue to indicate that additional pressurized fluid is still needed to move toward the set point. Therefore, if such a fault is not detected, no new input signal will be provided because the control logic implemented by the logic circuit device will operate as if the supply switch 104 is already open based on the input signal previously provided to open the supply switch 104.

[0038] To prevent the control device 102 from becoming trapped in the aforementioned fault state, the logic circuitry 116 detects faults by monitoring sensor feedback data over a period of time and identifying when changes in the sensor feedback data (e.g., position changes and / or pressure changes) during the period do not match progress toward a set point during a supply action. That is, if the control logic implemented by the logic circuitry 116 indicates that pressurized fluid is being added to the actuator (e.g., a supply action) during a period of time, but the sensor feedback data indicates a relatively small increase (e.g., less than a threshold value) in pressure at the actuator 124 (or a relatively small change in the corresponding position of the valve 126) during the period of time, the logic circuitry 116 can infer that a fault has occurred that prevents proper implementation of the supply action. In some examples, upon detecting such a fault, the logic circuitry 116 automatically attempts to recover from the fault by reissuing the input signal that initiated the supply action in the first place. In this manner, although the supply converter 104 in the aforementioned example does not respond to the initial input signal, the supply converter 104 can respond to a second or subsequent input signal that triggers the reapplication of the first (relatively high) current to open the converter. If the supply switch 104 does respond to the second or subsequent input signal, the control device 102 may continue to operate as desired to appropriately control the valve 126 .

[0039] The above examples are described with reference to a failure of the supply converter 104 to respond to an input signal. However, there are other situations that may cause a similar fault condition in which the actuator 124 is not pressurized despite an input signal being provided to open the supply converter 104. For example, although the supply converter 104 may respond appropriately to the input signal, the supply relay 108 may fail to open, resulting in no pressurized fluid being provided to the actuator 124. In some examples, reissuing the input signal to the supply converter 104 one or more subsequent times may resolve the problem by causing the supply relay 108 to open.

[0040] Another fault scenario occurs when the bleed relay 110 opens when it is expected to be closed (which may or may not be based on the bleed converter 106 opening when it is expected to be closed). In this case, even if both the supply converter 104 and the supply relay 108 are functioning properly, the pneumatic actuator 124 may not be pressurized as expected because the pressurized fluid supplied to the actuator 124 is immediately vented via the improperly opened bleed relay 110. In this case, reissuing the input signal to open the supply converter 104 will not resolve the fault, as the fault is based on a failure of the bleed converter 106 and / or the bleed relay 110. Therefore, in some examples, in addition to reissuing the input signal to open the supply converter 104 after detecting a fault in the supply operation, the logic circuitry 116 may also provide an input signal to direct the bleed converter 106 to the closed state. Providing such an input signal after a fault is detected during a supply event may address intermittent faults in the drain converter 106 and / or drain relay 110 that prevent these devices from closing in response to a previous input signal directing such closure.

[0041] In some examples, similar faults can be detected in conjunction with the implementation of a bleed action. Furthermore, after such a fault is detected during a bleed action, a similar process of reissuing input signals can be implemented to attempt to recover from such a fault. For example, in some examples, if the sensor feedback data indicates that pressurized fluid in the pneumatic actuator 124 is to be bleed to move the control valve 126 toward the set point, but the change in sensor feedback data over a threshold time period during the bleed action does not indicate significant progress in bleed fluid, the logic circuit device 116 can provide a new input signal to the bleed converter 106 to attempt to cause the bleed converter 106 and the bleed relay 110 to open (which may not have been done in response to a similar input signal previously provided when the bleed action was initiated). Additionally or alternatively, in some examples, the logic circuit device 116 can provide an input signal to the supply converter 104 to cause the supply converter 104 to close in response to the detected fault (in the event that the supply converter 104 and / or the supply relay 108 previously failed to close at the end of the last supply action).

[0042] In some examples, the logic circuit device 116 records each detected fault so that the number, frequency, and / or time intervals of the faults can be tracked over time. In some examples, faults detected during a supply action are tracked independently of faults detected during a discharge action. In some examples, faults occurring during a supply action or a discharge action can be tracked together. In some examples, faults detected by the logic circuit device 116 can be reported to the process controller 128 as alarms for presentation to a control room operator and / or other personnel (e.g., maintenance personnel). In some examples, reporting of the fault occurs after each fault is detected. In other examples, fault reporting occurs after the number of faults reaches a particular threshold and / or when a threshold number of faults are detected within a particular time frame. In some examples, the specific conditions that trigger reporting of the detected faults can be configured by an end user of the control device 102.

[0043] Figure 2 Shows the implementation Figure 1 Example manner of the example logic circuit device 116 of the example control device 102. Figure 2 As shown, the exemplary logic circuit device 116 includes an exemplary communication interface 202 , an exemplary sensor interface 204 , an exemplary sensor feedback analyzer 206 , an exemplary input signal generator 208 , an exemplary drive percentage analyzer 210 , an exemplary fault detector 212 , an exemplary counter 214 , an exemplary timer 216 , and an exemplary memory 218 .

[0044] exist Figure 2 In the example shown, the example communication interface 202 enables communication between the control device 102 and the process controller 128 and / or other components in the process control system. Thus, in some examples, the control device 102 receives setpoints and / or other control signals from the process controller 128 via the example communication interface 202. In some examples, the setpoints can be stored in the example memory 218. Additionally, in some examples, the logic circuitry 116 provides data (e.g., sensor feedback data, detected faults, etc.) to the process controller 128.

[0045] exist Figure 2 In the example shown, the example sensor interface 204 receives sensor feedback data from the position sensor 112 and / or the pressure sensor 114. Figure 2 In the illustrated example, the example sensor feedback analyzer 206 analyzes sensor feedback data relative to set points stored in the example memory 218. Based on the analysis, the example input signal generator 208 generates an input signal provided to the supply converter 104 or the exhaust converter 106 to open or close the converter 104, 106.

[0046] exist Figure 2 In the illustrated example, example actuation percentage analyzer 210 determines the current supply actuation percentage and exhaust actuation percentage of the control device. As used herein, the supply actuation percentage defines the proportion or percentage of the most recent time period during which an input signal provided to supply switch 104 actuated supply switch 104 to an open state, thereby adding (supplying) pressurized air to actuator 124. That is, the supply actuation percentage is the percentage corresponding to the most recent time period of the supply action. Similarly, as used herein, the exhaust actuation percentage defines the proportion or percentage of the most recent time period during which an input signal provided to exhaust switch 106 actuated exhaust switch 106 to an open state, thereby removing (exhausting) pressurized air from actuator 124. That is, the exhaust actuation percentage is the percentage corresponding to the most recent time period of the exhaust action. For purposes of explanation, the most recent time period used to calculate the supply and exhaust supply actuation percentages is referred to herein as the actuation percentage time window. The actuation percentage actuation window can correspond to any suitable duration (e.g., 1 second, 2 seconds, 3 seconds, 5 seconds, 10 seconds, 15 seconds, etc.).

[0047] In some examples, rather than defining the actuation percentage actuation window by a specific duration, the actuation percentage actuation window is defined by a set number of control actions corresponding to periodic times when a new input signal may be provided to either the supply converter 104 or the exhaust converter 106. The control action may be a supply actuation action (in which the supply converter 104 is directed to move (or remain) open), an exhaust actuation action (in which the exhaust converter 106 is directed to move (or remain) open), or a neutral actuation action (in which both converters 104, 106 are directed to move (or remain) closed). As described above, in some examples, the control action is limited to once every 50 ms (or any other suitable time interval defined by the power constraints of the system). While the control action may occur every 50 ms, this does not necessarily mean that a new input signal is actually provided to one of the converters every 50 ms. Instead, as described above, an initial input signal may be provided to open one of the converters 104, 106, followed by waiting an appropriate amount of time (e.g., a duration of 5 control actions, 20 control actions, 100 control actions, etc.) before providing another input signal to close the corresponding converter.

[0048] As described above, the actuation percentage time window corresponds to a recent time period (or a corresponding number of control actions). Thus, as time passes, the input signals (and / or corresponding control actions) that actuate converters 104, 106 change on a rolling basis, which input signals contribute to the calculation of the supply and emission actuation percentages. For example, assume that the actuation percentage time window is 20 seconds. Further assume that, at a first point in time, the recent 20 seconds may be characterized by both converters 104, 106 being actuated to a closed state (corresponding to a neutral control action) for the first 2 seconds, followed by the supply converter 104 being actuated to an open state (corresponding to a supply control action) for the next 6 seconds, followed by both converters 104, 106 being closed (corresponding to a neutral control action) for 2 seconds, and the emission converter 106 being actuated to an open state (corresponding to an emission control action) for the final 10 seconds (until the first point in time). In this example, at the first time point, the supply drive percentage is 30% (corresponding to 6 seconds of the 20 seconds in which the supply converter 104 is driven to the open state), and the exhaust drive percentage is 50% (corresponding to 10 seconds of the 20 seconds in which the exhaust converter 106 is driven to the open state).

[0049] Now, assume that another five seconds have passed, during which no new input signals are provided to converters 104, 106, causing the control sequence to continue driving exhaust converter 106 to the open state while supply converter 104 remains closed. At this second point in time (five seconds after the first point in time), the initial two seconds when both converters 104, 106 were closed, and the subsequent three seconds during which supply converter 104 was driven to the open state, are no longer within the actuation percentage time window (e.g., the most recent 20 seconds). Therefore, the input signals associated with this five-second time frame do not contribute to the calculation of the supply and exhaust actuation percentages at the second point in time. Consequently, at the second point in time, the supply actuation percentage is now 15% (only three of the most recent 20 seconds were associated with driving supply converter 104 to the open state), while the exhaust actuation percentage is 75% (corresponding to the last 15 of the most recent 20 seconds in the actuation percentage time window).

[0050] In some examples, the drive percentage analyzer 210 determines whether the supply drive percentage meets (e.g., exceeds) a supply drive threshold and / or whether the emission drive percentage meets (e.g., exceeds) an emission drive threshold. In some examples, the supply drive percentage or emission drive percentage meeting the corresponding threshold serves as a precondition for detecting a fault, as further described below. More specifically, in some examples, a fault is inferred only if the supply drive percentage or emission drive percentage meets (e.g., exceeds) a relatively high threshold (e.g., 75%, 80%, 85%, 90%, 95%, 100%, etc.) within a given time period. In some examples, the supply drive threshold and / or emission drive threshold are set high enough to exclude situations where both a supply control action and an emission control action have occurred within the drive percentage time window. That is, in some examples, the threshold is met only if all or substantially all control actions within the drive percentage time window are supply control actions or emission control actions (with a relatively small possibility of neutral control actions in some examples). When the supply actuation percentage or the exhaust actuation percentage is relatively high within a given time period (e.g., an actuation percentage time window), relatively large changes in pressure in the actuator 124 and / or movement of the valve 126 can be expected. Accordingly, if one or more components of the example control device 102 are not functioning properly (e.g., the supply switch 104 does not open in response to an open input signal), such that pressurized fluid is not added to or removed from the actuator 124 as expected, the change in pressure in the actuator 124 and / or movement of the valve 126 during a given time period will likely be much smaller. Thus, a fault can be inferred when the change in pressure and / or position feedback data during these times is relatively small. Conversely, when the supply actuation percentage and the exhaust actuation percentage are not particularly high within a given time period, relatively small changes in pressure and / or corresponding movement of the actuator 124 and / or control valve 126 may exist, making it impossible to rely on comparisons of actual (e.g., measured) changes in the feedback data to indicate a fault.

[0051] In some examples, both the supply-driven percentage and the exhaust-driven percentage can be compared to the same common drive threshold. In other examples, a supply-driven threshold can be defined for the supply-driven percentage that is different from the exhaust-driven threshold defined for the exhaust-driven percentage. In some examples, the supply-driven threshold and the exhaust-driven threshold (and / or the common drive threshold) are stored in example memory 218.

[0052] exist Figure 2In the example shown, the example fault detector 212 compares sensor feedback data at different points in time (associated with a given time period when either the supply actuation percentage or the exhaust actuation percentage meets a threshold) to determine whether a fault has occurred. More specifically, as described above, in some examples, a fault is detected based on changes in sensor feedback data measured at different points in time when a fault threshold is met. In some examples, the fault threshold is defined as a certain ratio of the difference between the high and low limits of the operating range of pressure and / or position of the associated actuator 124 and control valve 126. That is, in some examples, the fault threshold for pressure change is defined as a percentage (e.g., 1%, 2%, 5%, 10%, etc.) of the difference between the high and low pressure limits defined for the operating range of the pneumatic actuator 124. Similarly, in some examples, the fault threshold for position change is defined as a percentage (e.g., 1%, 2%, 5%, 10%, etc.) of the difference between the 0% and 100% positions of the calibrated travel span (whether linear or rotary) of the control member in the control valve 126. In some examples, a specific value for the fault threshold is defined based on the minimum expected change in pressure and / or position of the pneumatic actuator 124 and / or control valve 126 over a given time period during which sensor feedback data is collected and compared. Thus, assuming the fault threshold is defined as 2% (because a change of at least 2% is expected over the relevant time period), a fault is inferred when the actual (measured) change in position over the given time period is less than 2% of the full travel span of the control valve 126 and / or the change in pressure over the given time period is less than 2% of the difference between the minimum and maximum operating pressures of the pneumatic actuator 124. In some examples, different fault thresholds can be defined for each of the position change and the pressure change. In some examples, the same fault threshold can be defined for both the position change and the pressure change. In some examples, both the pressure change and the position change must meet the corresponding threshold to determine a fault. In other examples, only one of the pressure change or the position change needs to meet the corresponding threshold to determine a fault.

[0053] In some examples, the given time period during which sensor feedback data is compared corresponds to a threshold time period defined based on the example counter 214 exceeding a particular count threshold. Additionally or alternatively, the threshold time period can be specified based on an elapsed time period determined by the example timer 216. The threshold time period can correspond to any suitable duration (e.g., 1 second, 2 seconds, 3 seconds, 5 seconds, 10 seconds, 15 seconds, etc.). In some examples, the fault detector 212 determines when to start and / or reset the example counter 214 and / or the example timer 216. More specifically, in some examples, the fault detector 212 resets and / or starts the example counter 214 and / or the example timer 216 in response to the start of a new supply action and / or a new bleed action (e.g., in response to the input signal generator 208 providing an input signal to open the supply converter 104 or the bleed converter 106). However, as described above, in some examples, fault detection is limited to instances where the supply drive percentage or the bleed drive percentage meets the corresponding drive threshold determined by the drive percentage analyzer 210. Thus, in some examples, the example counter 214 and / or the example timer 216 are started and / or reset only when the drive threshold is met.

[0054] In some examples, when the counter 214 and / or the timer 216 are reset or enabled, the fault detector 212 causes the sensor feedback data received by the sensor interface 204 to be stored in the memory 218. The stored sensor feedback data serves as an initial reference point for comparison with the reference feedback data after the counter 214 and / or the timer 216 meet the corresponding threshold. Thus, in some examples, once the counter 214 exceeds the corresponding threshold count and / or the timer 216 passes the corresponding threshold time period, the example fault detector 212 determines the difference between the sensor feedback data at the current point in time and the initial sensor feedback data stored in the memory 218 when the counter 214 and / or the timer 216 were enabled. In some examples, if the difference or change in the sensor feedback data meets (e.g., is less than) the fault threshold, the example fault detector 212 determines that a fault has occurred.

[0055] In some examples, once fault detector 212 has detected a fault, fault detector 212 may record the fault by incrementing a fault counter in example memory 218. Furthermore, in some examples, fault detector 212 may initiate a recovery process to attempt to resolve and / or recover from the detected fault. In some examples, the recovery process includes input signal generator 208 generating a second input signal that is identical to a previous input signal that initiated a supply action or a drain action associated with the detected fault. In some examples, this new input signal constitutes the start of a new supply action or drain action. Thus, in some such examples, fault detector 212 initializes counter 214 and / or timer 216 and updates stored sensor feedback data to detect the fault again after counter 214 and / or timer 216 have reached an appropriate threshold corresponding to the relevant time period.

[0056] Furthermore, in some examples, in response to a fault detected during a drain action, input signal generator 208 may provide an input signal to shut down supply converter 104 to address the possibility that the fault is caused by supply converter 104 and / or associated supply relay 108 not properly closing. Furthermore, in some examples, in response to a fault detected during a drain action, input signal generator 208 may provide an input signal to shut down drain converter 106 to address the possibility that the fault is caused by drain converter 106 and / or associated drain relay 110 not properly closing.

[0057] Although Figure 2 The implementation is shown in Figure 1 The example of the logic circuit device 116 is as follows, but Figure 2 One or more of the elements, processes and / or devices shown in the drawings may be combined, divided, rearranged, omitted, eliminated and / or implemented in any other manner. Figure 1The example communication interface 202, the example sensor interface 204, the example sensor feedback analyzer 206, the example input signal generator 208, the example drive percentage analyzer 210, the example fault detector 212, the example counter 214, the example timer 216, the example memory 218, and / or more generally, the example logic circuitry 116 can be implemented by hardware, software, firmware, and / or any combination of hardware, software, and / or firmware. Thus, for example, any of the example communication interface 202, the example sensor interface 204, the example sensor feedback analyzer 206, the example input signal generator 208, the example drive percentage analyzer 210, the example fault detector 212, the example counter 214, the example timer 216, the example memory 218, and / or more generally, the example logic circuitry 116 can be implemented by one or more analog or digital circuits, logic circuits, programmable processors, programmable controllers, graphics processing units (GPUs), digital signal processors (DSPs), application specific integrated circuit devices (ASICs), programmable logic devices (PLDs), and / or field programmable logic devices (FPLDs). When any apparatus or system claims of this patent are read to cover pure software and / or firmware implementations, at least one of the example communication interface 202, the example sensor interface 204, the example sensor feedback analyzer 206, the example input signal generator 208, the example drive percentage analyzer 210, the example fault detector 212, the example counter 214, the example timer 216, and / or the example memory 218 is expressly defined herein to include a non-transitory computer-readable storage device or storage disk, such as a memory, digital versatile disk (DVD), compact disk (CD), Blu-ray disk, etc., including the software and / or firmware. Furthermore, Figure 1 Example logic circuitry 116 may include Figure 2 In addition to or in place of the components, processes and / or devices shown Figure 2 One or more of the elements, processes and / or devices shown, and / or may include more than one of any or all of the elements, processes and devices shown. As used herein, the phrase "communication" (including variations thereof) includes direct communication and / or indirect communication through one or more intermediate components, and does not require direct physical (e.g., wired) communication and / or constant communication, but rather includes selective communication at periodic intervals, scheduled intervals, non-periodic intervals and / or one-time events.

[0058] Figure 3 shows a representation for implementing Figure 1 and / or Figure 2116 of the logic circuit device 116, a flowchart of exemplary hardware logic, machine readable instructions, hardware-implemented state machine and / or any combination thereof. The machine readable instructions may be one or more executable programs or a portion of an executable program for use by, for example, the following in combination Figure 4 The program is executed by a computer processor of the processor 412 shown in the exemplary processor platform 400 discussed. The program may be implemented in software stored on a non-transitory computer-readable storage medium such as a CD-ROM, floppy disk, hard drive, DVD, Blu-ray disk, or memory associated with the processor 412, but the entire program and / or portions thereof may also be executed by a device other than the processor 412 and / or implemented in firmware or dedicated hardware. In addition, although reference is made to Figure 3 The flowchart shown describes an example program, but alternatively, many other methods of implementing the example logic circuit device 116 can be used. For example, the order of execution of the blocks can be changed, and / or some of the blocks described can be changed, eliminated, or combined. Additionally or alternatively, any or all of these blocks can be implemented by one or more hardware circuits (e.g., discrete and / or integrated analog and / or digital circuit devices, FPGAs, ASICs, comparators, operational amplifiers (op-amps), logic circuits, etc.) that are configured to perform the corresponding operations without executing software or firmware.

[0059] The machine-readable instructions described herein may be stored in one or more of a compressed format, an encrypted format, a segmented format, a compiled format, an executable format, an encapsulated format, and the like. The machine-readable instructions described herein may be stored as data (e.g., portions of instructions, code, representations of code, and the like) that can be used to create, manufacture, and / or generate machine-executable instructions. For example, the machine-readable instructions may be segmented and stored on one or more storage devices and / or computing devices (e.g., servers). The machine-readable instructions may need to be installed, modified, adapted, updated, combined, supplemented, configured, decrypted, decompressed, unpacked, distributed, redistributed, compiled, and the like so that they can be directly read, interpreted, and / or executed by a computing device and / or other machine. For example, the machine-readable instructions may be stored in multiple parts that are separately compressed, encrypted, and stored on separate computing devices, where the parts, when decrypted, decompressed, and combined, form a set of executable instructions that implement a program such as described herein.

[0060] In another example, the machine-readable instructions may be stored in a state in which they are readable by a computer, but require the addition of a library (e.g., a dynamic link library (DLL)), a software development kit (SDK), an application programming interface (API), etc., in order to execute the instructions on a particular computing device or other device. In another example, the machine-readable instructions and / or corresponding program may need to be configured (e.g., stored settings, data inputs, recorded network addresses, etc.) before the machine-readable instructions and / or corresponding program can be executed in whole or in part. Therefore, the disclosed machine-readable instructions and / or corresponding program are intended to cover such machine-readable instructions and / or programs regardless of the particular format or state of the machine-readable instructions and / or program when stored or otherwise at rest or in transport.

[0061] The machine-readable instructions described herein may be represented by any past, present, or future instruction language, scripting language, programming language, etc. For example, the machine-readable instructions may be represented using any of the following languages: C, C++, Java, C#, Perl, Python, JavaScript, Hypertext Markup Language (HTML), Structured Query Language (SQL), Swift, etc.

[0062] As described above, the present invention may be implemented using executable instructions (e.g., computer and / or machine readable instructions) stored on a non-transitory computer and / or machine readable medium. Figure 3 In an exemplary process, the non-transitory computer and / or machine-readable medium is, for example, a hard drive, flash memory, read-only memory, optical disk, digital versatile disk, cache, random access memory, and / or any other storage device or storage disk in which information is stored for any duration (e.g., for an extended period of time, permanently, for a brief instance, for temporary buffering, and / or for caching of information). As used herein, the term non-transitory computer-readable medium is expressly defined to include any type of computer-readable storage device and / or storage disk and to exclude propagating signals and to exclude transmission media.

[0063] "Include" and "comprising" (and all forms and tenses thereof) are used herein as open-ended terms. Thus, whenever a claim employs any form of "include" or "comprising" (e.g., includes, comprises, includes, including, having, etc.) as a preamble or in any type of claim recitation, it should be understood that additional elements, terms, etc. may be present without falling outside the scope of the corresponding claim or recitation. As used herein, when the phrase "at least" is used as a transition term, such as in the preamble of a claim, it is open-ended in the same manner that the terms "include" and "comprising" are open-ended. When used, for example, in a form such as A, B, and / or C, the term "and / or" refers to any combination or subset of A, B, and C, such as (1) A alone, (2) B alone, (3) C alone, (4) A and B, (5) A and C, (6) B and C, and (7) A and B and C. As used herein in the context of describing structures, components, items, objects, and / or things, the phrase "at least one of A and B" is intended to refer to implementations that include any of (1) at least one A, (2) at least one B, and (3) at least one A and at least one B. Similarly, as used herein in the context of describing structures, components, items, objects, and / or things, the phrase "at least one of A or B" is intended to refer to implementations that include any of (1) at least one A, (2) at least one B, and (3) at least one A and at least one B. As used herein in the context of describing the operation or performance of processes, instructions, acts, activities, and / or steps, the phrase "at least one of A and B" is intended to refer to implementations that include any of (1) at least one A, (2) at least one B, and (3) at least one A and at least one B. Similarly, as used herein in the context of describing the operation or performance of processes, instructions, actions, activities and / or steps, the phrase "at least one of A or B" is intended to refer to an implementation that includes any of (1) at least one A, (2) at least one B, and (3) at least one A and at least one B.

[0064] As used herein, singular references (e.g., "a," "an," "first," "second," etc.) do not exclude a plurality. The terms "a" or "an" entity as used herein refer to one or more of that entity. The terms "a" (or "an"), "one or more," and "at least one" are used interchangeably herein. Furthermore, although listed separately, multiple devices, elements, or method actions may be implemented by, for example, a single unit or processor. Additionally, although individual features may be included in different examples or claims, these features may be combined, and inclusion in different examples or claims does not mean that a combination of features is not feasible and / or disadvantageous.

[0065] Figure 3The example process begins at block 302, where the example input signal generator 208 generates input signals based on setpoints and sensor feedback data to drive the supply converter 104 and the exhaust converter 106. At block 304, the example drive percentage analyzer 210 determines whether the supply drive percentage satisfies a supply drive threshold. In some examples, the supply drive threshold is relatively high (e.g., 75%, 80%, 85%, 90%, 95%), and the supply drive threshold is satisfied when the supply drive percentage exceeds the threshold. If the example drive percentage analyzer 210 determines that the supply drive threshold has been satisfied, control proceeds to block 306, where the example fault detector 212 determines whether a new supply action has been initiated. If the example input signal generator 208 generates (e.g., at block 302) a new input signal instructing the supply converter 104 to turn on and move to the open state, then a new supply action has been initiated. If a new supply action has been initiated, control proceeds to block 308, where the example fault detector 212 resets and / or starts a supply action counter (e.g., the example counter 214). Additionally or alternatively, in some examples, the fault detector 212 resets and / or starts a timer (e.g., the example timer 216). At block 310, the example fault detector 212 stores the sensor feedback data (e.g., the current position of the valve 126 measured by the example position sensor 112 and / or the current pressure in the actuator 124 measured by the pressure sensor 114). Thereafter, control returns to block 302 to continue driving the converters 104, 106 based on the set point and the sensor feedback data.

[0066] Returning to block 306, if the example fault detector 212 determines that a new supply action has not yet begun (e.g., a supply action was previously initiated in the past and is still in progress), control proceeds to block 312 where the example fault detector 212 increments the supply action counter. In some examples, the logic circuitry 116 iterates through the supply action counter periodically (e.g., every 50 ms). Figure 3 The process of supplying an action counter such that the increment of the supply action counter represents the corresponding elapsed time period. Therefore, at block 314, the example fault detector 212 determines whether the supply action counter meets (e.g., exceeds) a supply action time threshold. In other examples, where the example timer 216 is used instead of the counter 214, block 312 may be omitted and corresponds to the example fault detector 212 determining whether the elapsed time has met (e.g., exceeded) a supply action time threshold. If the supply action time threshold is not met, control returns to block 302. Once the supply action time threshold is met, control proceeds to block 316.

[0067] At block 316, the example fault detector 212 calculates the difference between the stored sensor feedback data (e.g., stored at block 308) and the current sensor feedback data. That is, in some examples, the fault detector 212 calculates the absolute value of the difference between the position of the valve 126 at the time the supply action time threshold is met (determined at block 314) and the position of the valve 126 at the time the supply action counter (or timer) is reset and / or initialized (stored at block 308). Additionally or alternatively, the example fault detector 212 calculates the absolute value of the difference between the pressure in the actuator 124 at the time the supply action time threshold is met (determined at block 314) and the pressure in the actuator 124 stored at block 310 at the time the supply action counter (or timer) is reset and / or initialized (at block 308). At block 318, the example fault detector 212 determines whether the difference in the sensor feedback data meets a fault threshold. In some examples, a different fault threshold is assigned to position sensor data than to pressure sensor data. In some examples, fault detector 212 determines that a fault threshold has been met when both the position sensor data and the pressure sensor data meet corresponding fault thresholds. In other examples, fault detector 212 determines that a fault threshold has been met when at least one of the position sensor data or the pressure sensor data meets the corresponding fault threshold. In some examples, the fault threshold is relatively low (e.g., 1%, 2%, 3%, etc.), and the fault threshold is met when the sensor feedback data is less than the threshold.

[0068] If the difference in the sensor feedback data does not meet (e.g., is not below) the fault threshold, no inference is made regarding a fault, and control returns to block 302. However, if the example fault detector 212 determines at block 318 that the sensor feedback data does meet the fault threshold, a fault is inferred. Therefore, in this case, control proceeds to block 320, where the example fault detector 212 increments the supply fault counter to record the detected fault. Thereafter, control proceeds to block 322, where the example input signal generator 208 generates an input signal to shut down the emissions converter 106. The input signal generated at block 322 is used to attempt to recover from a possible intermittent fault in the emissions converter 106 and / or emissions relay 110, which may have caused the detected fault based on a fault that was expected to open in response to a previous input signal (e.g., previously provided at block 302). At block 324, the example input signal generator 208 generates an input signal to open the emissions converter 106. The input signal generated at block 324 is used to attempt to recover from a possible intermittent fault in the supply converter 104 and / or the drain relay 108, which may have caused the detected fault based on a fault opening as expected in response to a previous input signal (e.g., previously provided at block 302). In some examples, the input signal provided at block 324 constitutes the start of a new supply action, which will cause the counter (or timer) at blocks 306 and 308 to be reset and / or initialized, thereby initiating a new sequence to test for another fault (or confirm that a previously detected fault has been resolved and is therefore only intermittent).

[0069] At block 326, the example fault detector 212 determines whether to report a detected fault. If so, control proceeds to block 328, where the example communication interface reports the fault. In some examples, each detected fault is reported. In other examples, a fault is reported after a supply fault counter is incremented a threshold number of times. In some examples, a fault is reported when a supply fault counter is incremented a threshold number of times within a threshold time period. After reporting the fault, control proceeds to block 330. Returning to block 326, if a detected fault is not to be reported, control proceeds directly to block 330. At block 330, the logic circuit device determines whether to continue the process. If so, control returns to block 302. Otherwise, Figure 3 The example process ends.

[0070] Returning to block 304, if the example drive percentage analyzer 210 determines that the supply drive percentage does not meet (e.g., does not exceed) the supply drive threshold, control proceeds to block 332, where the example drive percentage analyzer 210 determines whether the exhaust drive percentage meets the exhaust drive threshold. In some examples, the exhaust drive threshold is the same as the supply drive threshold. In other examples, the exhaust drive threshold and the supply drive threshold are different. If the exhaust drive threshold does not meet (e.g., does not exceed) the exhaust drive threshold, control returns to block 302. Otherwise, control proceeds to block 334.

[0071] In the illustrated example, blocks 334-348 generally correspond to blocks 306-320, but blocks 334-348 are implemented in conjunction with a drain action, whereas blocks 306-320 correspond to a supply action. Thus, at block 334, the example fault detector 212 determines whether a new drain action has been initiated. If so, the example fault detector resets and / or initializes a drain action counter and / or timer (block 336) and stores current sensor feedback data (block 338) before control returns to block 302. If the example fault detector 212 determines at block 334 that a new drain action has not been initiated (e.g., a drain action was previously initiated in the past and is still in progress), the example fault detector 212 increments the drain action counter (block 340) and / or allows the timer to elapse until a drain action time threshold is met (as determined at block 342). In some examples, the drain action time threshold is the same as the supply action time threshold. In other examples, the drain action time threshold is different from the supply action time threshold. At block 344, the example fault detector 212 calculates the difference between the stored sensor feedback data (e.g., stored at block 338) and the current sensor feedback data. If the difference does not meet (e.g., is not less than) the fault threshold, as determined at block 344, control returns to block 302. If the difference does meet (e.g., is less than) the fault threshold, control proceeds to block 348, where the example fault detector 212 increments an exhaust fault counter to record the detected fault. In some examples, the fault threshold for the difference in sensor feedback data is the same for both the supply action and the exhaust action. In other examples, the fault threshold for the difference in sensor feedback data is different between the supply action and the exhaust action. Furthermore, while the example process indicates separate supply fault counters and exhaust fault counters, in other examples, a single counter may be used to jointly track faults detected during both the supply action and the exhaust action.

[0072] At block 350, the example input signal generator 208 generates an input signal to turn off the supply converter (e.g., to attempt to recover from a possible fault in the supply converter 104 and / or the supply relay 108). At block 352, the example input signal generator 208 generates an input signal to turn on the exhaust converter (e.g., to attempt to recover from a possible fault in the exhaust converter 106 and / or the exhaust relay 110). Thereafter, control proceeds to block 326 to proceed as described above.

[0073] Figure 4 is constructed to execute Figure 3 Instructions to achieve Figure 1 and / or Figure 2 The processor platform 400 may be, for example, a server, a personal computer, a workstation, a self-learning machine (e.g., a neural network), a mobile device (e.g., a cellular phone, a smartphone, an iPad, etc.). TM tablet computer), personal digital assistant (PDA), Internet appliance, or any other type of computing device.

[0074] The processor platform 400 of the illustrated example includes a processor 412. The processor 412 of the illustrated example is hardware. For example, the processor 412 can be implemented by one or more integrated circuits, logic circuits, processors, GPUs, DSPs, or controllers from any desired series or manufacturer. The hardware processor can be a semiconductor-based (e.g., silicon-based) device. In this example, the processor implements the example sensor feedback analyzer 206, the example input signal generator 208, the example drive percentage analyzer 210, the example fault detector 212, the example counter 214, and the example timer 216.

[0075] The processor 412 of the illustrated example includes a local memory 413 (e.g., a cache). The processor 412 of the illustrated example communicates with a main memory including a volatile memory 414 and a non-volatile memory 416 via a bus 418. The volatile memory 414 may be comprised of synchronous dynamic random access memory (SDRAM), dynamic random access memory (DRAM), Dynamic Random Access Memory The non-volatile memory 416 may be implemented by flash memory and / or any other desired type of memory device. Access to the main memories 414, 416 is controlled by a memory controller.

[0076] The processor platform 400 of the illustrated example also includes an interface circuit 420. The interface circuit 420 may be implemented by any type of interface standard, such as an Ethernet interface, a universal serial bus (USB), interface, near field communication (NFC) interface, and / or PCI express interface.

[0077] In the example shown, one or more input devices 422 are connected to the interface circuitry 420. The input devices 422 allow a user to enter data and / or commands into the processor 412. The input devices may be implemented by, for example, an audio sensor, a microphone, a camera (still or video), a keyboard, buttons, a mouse, a touch screen, a trackpad, a trackball, isopoint, and / or a voice recognition system.

[0078] One or more output devices 424 are also connected to the interface circuit 420 of the illustrated example. Output device 424 can be implemented, for example, by a display device (e.g., a light emitting diode (LED), an organic light emitting diode (OLED), a liquid crystal display (LCD), a cathode ray tube display (CRT), an in-place switch (IPS) display, a touch screen, etc.), a tactile output device, a printer, and / or a speaker. Thus, the interface circuit 420 of the illustrated example typically includes a graphics driver card, a graphics driver chip, and / or a graphics driver processor.

[0079] The interface circuitry 420 of the illustrated example also includes communication devices, such as transmitters, receivers, transceivers, modems, residential gateways, wireless access points, and / or network interfaces, to facilitate exchanging data with external machines (e.g., any type of computing device) via a network 426. Communication may be via, for example, an Ethernet connection, a digital subscriber line (DSL) connection, a telephone line connection, a coaxial cable system, a satellite system, a field-line wireless system, a cellular telephone system, etc.

[0080] The processor platform 400 of the illustrated example also includes one or more mass storage devices 428 for storing software and / or data. Examples of such mass storage devices 428 include floppy disk drives, hard disk drives, optical disk drives, Blu-ray disk drives, redundant array of independent disks (RAID) systems, and digital versatile disk (DVD) drives.

[0081] Figure 3 The machine-executable instructions 432 may be stored in the mass storage device 428, in the volatile memory 414, in the non-volatile memory 416, and / or on a removable, non-transitory computer-readable storage medium such as a CD or DVD.

[0082] As can be appreciated from the foregoing, exemplary methods, apparatus, and articles have been disclosed that enable control devices with electro-pneumatic converters to operate with less power than other similar devices because the converters are switched on based on a digital input signal that triggers a first current to initially open the converter, followed by a reduced second current to maintain the converter in the open state. While this implementation saves power, it creates the possibility that the control device may intermittently fail due to not responding to the initial high current and remain stuck in that state. The examples disclosed herein overcome this technical challenge by monitoring sensor feedback over time to detect such faults and automatically reissuing an input signal to the converter in response to the detected fault. The reissuing input signal is provided in an attempt to automatically resolve the fault and restore the control device to normal operation without direct human involvement. Furthermore, in some examples, detected faults can be tracked or recorded over time to provide an indication of the frequency with which intermittent faults occur, allowing maintenance personnel to predict the likelihood of a complete fault in the device and, therefore, replace or otherwise fix the device before a complete fault occurs.

[0083] Disclosed herein are example methods, apparatuses, systems, and articles of manufacture for detecting and / or recovering from failures in valve control devices. Other examples and combinations thereof include the following:

[0084] Example 1 includes an apparatus comprising an input signal generator for providing a digital input signal to a first converter at a first point in time, the first converter corresponding to one of a supply converter or a discharge converter, the supply converter for controlling actuation of a supply relay to deliver pressurized fluid to an actuator of a valve operably coupled to a process control system, the discharge converter for controlling actuation of a discharge relay to discharge pressurized fluid from the actuator, the digital input signal for triggering application of a current to the first converter to open the first converter, and a fault detector for determining a difference in at least one of a pressure in the actuator or a position of a flow control member in the valve over a time period after the first point in time, and detecting a fault in at least one of the supply converter, the discharge converter, the supply relay, or the discharge relay when the difference meets a fault threshold.

[0085] Example 2 includes the apparatus of Example 1, further comprising a drive percentage analyzer for determining a supply drive percentage during a time window corresponding to a most recent time period, the supply drive percentage corresponding to a first time proportion associated with one or more supply actions during the time window, and determining an emission drive percentage during the time window, the emission drive percentage corresponding to a second time proportion associated with one or more emission actions during the time window, the fault detector for determining the difference in at least one of the following circumstances: (1) the supply drive percentage remains above a supply drive threshold as the time window advances through the time period, or (2) the emission drive percentage remains above an emission drive threshold as the time window advances through the time period.

[0086] Example 3 includes the apparatus of Example 2, wherein the supply actuation threshold and the exhaust actuation threshold are greater than 75%.

[0087] Example 4 includes the apparatus of Example 1, wherein the current is a first current, the digital input signal triggers application of a second current after application of the first current, the second current being lower than the first current.

[0088] Example 5 includes the apparatus of Example 4, wherein the digital input signal is a first digital input signal, the input signal generator automatically provides a second digital input signal to the first converter in response to the fault detector detecting the fault, the second digital input signal triggering subsequent application of the first current to the first converter to turn on the first converter.

[0089] Example 6 includes the apparatus of Example 1, wherein the digital input signal is a first digital input signal and the current is a first current, the input signal generator automatically provides a second digital input signal to a second converter in response to the fault detector detecting the fault, the second converter corresponding to one of the supply converter or the discharge converter that is different from the first converter, the second digital input signal triggering application of a second current to the second converter to shut down the second converter.

[0090] Example 7 includes the apparatus of Example 1, wherein the fault detection apparatus is configured to record the fault in a memory.

[0091] Example 8 includes the apparatus of Example 1, further comprising a communication interface to report a fault to a controller in a process control system.

[0092] Example 9 includes the apparatus of Example 1, wherein the fault threshold corresponds to a percentage of at least one of a pressure operating range of the actuator or a calibrated travel span of the valve.

[0093] Example 10 includes the apparatus of Example 9, wherein the difference satisfies the fault threshold when the difference is less than the fault threshold, the fault threshold being less than 10% of the corresponding pressure operating range or position operating range.

[0094] Example 11 includes non-transitory computer-readable media, which includes instructions that, when executed, cause a machine to provide a digital input signal to at least a first converter at a first point in time, the first converter corresponding to one of a supply converter or a discharge converter, the supply converter controlling actuation of a supply relay to deliver pressurized fluid to an actuator operably coupled to a valve in a process control system, the discharge converter controlling actuation of a discharge relay to discharge pressurized fluid from the actuator, the digital input signal triggering application of current to the first converter to open the first converter, determining a difference in at least one of a pressure in the actuator or a position of a flow control member in the valve within a time period after the first point in time, and detecting a fault in at least one of the supply converter, the discharge converter, the supply relay, or the discharge relay when the difference meets a fault threshold.

[0095] Example 12 includes the non-transitory computer-readable medium of Example 11, wherein the instructions further cause the machine to determine a supply-driven percentage during a time window corresponding to a recent time period, the supply-driven percentage corresponding to a first proportion of time associated with one or more supply actions during the time window, and determine a drain-driven percentage during the time window, the drain-driven percentage corresponding to a second proportion of time associated with one or more drain actions during the time window. The difference is determined when at least one of: (1) the supply-driven percentage remains above a supply-driven threshold as the time window progresses through the time period, or (2) the drain-driven percentage remains above a drain-driven threshold as the time window progresses through the time period.

[0096] Example 13 includes the non-transitory computer-readable medium of Example 12, wherein the supply actuation threshold and the exhaust actuation threshold are greater than 75%.

[0097] Example 14 includes the non-transitory computer-readable medium of Example 11, wherein the current is a first current, the digital input signal triggers application of a second current after application of the first current, the second current being lower than the first current.

[0098] Example 15 includes the non-transitory computer-readable medium of Example 14, wherein the digital input signal is a first digital input signal, and the instructions further cause the machine to automatically provide a second digital input signal to the first converter in response to detecting the fault, the second digital input signal triggering a subsequent application of the first current to the first converter to turn on the first converter.

[0099] Example 16 includes the non-transitory computer-readable medium of Example 11, wherein the digital input signal is a first digital input signal and the current is a first current, the instructions further causing the machine to automatically provide a second digital input signal to a second converter in response to detecting the fault, the second converter corresponding to one of the supply converter or the exhaust converter that is different from the first converter, the second digital input signal triggering application of a second current to the second converter to shut down the second converter.

[0100] Example 17 includes the non-transitory computer-readable medium of Example 11, wherein the instructions further cause the machine to record the fault in a memory.

[0101] Example 18 includes the non-transitory computer-readable medium of Example 11, wherein the instructions further cause the machine to report the fault to a controller in the process control system.

[0102] Example 19 includes the non-transitory computer-readable medium of Example 11, wherein the fault threshold corresponds to a percentage of at least one of a pressure operating range of the actuator or a calibrated travel span of the valve.

[0103] Example 20 includes the non-transitory computer-readable medium of Example 19, wherein the difference satisfies the fault threshold when the difference is less than the fault threshold, the fault threshold being less than 10% of a corresponding pressure operating range or position operating range.

[0104] Example 21 includes a method comprising providing a digital input signal to a first converter at a first point in time, the first converter corresponding to one of a supply converter or a discharge converter, the supply converter controlling actuation of a supply relay to deliver pressurized fluid to an actuator operably coupled to a valve in a process control system, the discharge converter controlling actuation of a discharge relay to discharge pressurized fluid from the actuator, the digital input signal triggering application of a current to the first converter to open the first converter, determining a difference in at least one of a pressure in the actuator or a position of a flow control member in the valve for a time period after the first point in time, and detecting a fault of at least one of the supply converter, the discharge converter, the supply relay, or the discharge relay when the difference meets a fault threshold.

[0105] Example 22 includes the method of Example 21, further comprising determining a supply-driven percentage during a time window corresponding to a most recent time period, the supply-driven percentage corresponding to a first time proportion associated with one or more supply actions during the time window, and determining an emission-driven percentage during the time window, the emission-driven percentage corresponding to a second time proportion associated with one or more emission actions during the time window, wherein the difference is determined in at least one of the following circumstances: (1) the supply-driven percentage remains above a supply-driven threshold as the time window advances through the time period, or (2) the emission-driven percentage remains above an emission-driven threshold as the time window advances through the time period.

[0106] Example 23 includes the method of Example 22, wherein the supply actuation threshold and the exhaust actuation threshold are greater than 75%.

[0107] Example 24 includes the method of Example 21, wherein the current is a first current, and the digital input signal triggers application of a second current after application of the first current, the second current being lower than the first current.

[0108] Example 25 includes the method of Example 24, wherein the digital input signal is a first digital input signal, and the method further includes: in response to detecting the fault, automatically providing a second digital input signal to the first converter, the second digital input signal triggering a subsequent application of the first current to the first converter to turn on the first converter.

[0109] Example 26 includes the method of Example 21, wherein the digital input signal is a first digital input signal and the current is a first current, the method further comprising, in response to detecting the fault, automatically providing a second digital input signal to a second converter, the second converter corresponding to one of the supply converter or the exhaust converter that is different from the first converter, the second digital input signal triggering application of a second current to the second converter to shut down the second converter.

[0110] Example 27 includes the method of Example 21, further comprising recording the fault in a memory.

[0111] Example 28 includes the method of Example 21, further comprising reporting the fault to a controller in the process control system.

[0112] Example 29 includes the method of Example 21, wherein the fault threshold corresponds to a percentage of at least one of a pressure operating range of the actuator or a calibrated travel span of the valve.

[0113] Example 30 includes the method of Example 29, wherein the difference satisfies the fault threshold when the difference is less than the fault threshold, the fault threshold being less than 10% of the corresponding pressure operating range or position operating range.

[0114] Although certain example methods, apparatus, and articles of manufacture have been disclosed herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus, and articles of manufacture fairly falling within the scope of the claims of this patent.

[0115] The following claims are incorporated into this Detailed Description by reference, with each claim standing on its own as a separate embodiment of the disclosure.

Claims

1. A device comprising: an input signal generator for providing a digital input signal to a first converter at a first point in time, the first converter corresponding to one of a supply converter or a drain converter, the supply converter for controlling actuation of a supply relay to deliver pressurized fluid to an actuator operatively coupled to a valve in a process control system, the drain converter for controlling actuation of a drain relay to drain the pressurized fluid from the actuator, the digital input signal for triggering application of a current to the first converter to open the first converter; Drive Percentile Analyzer for: determining a supply-driven percentage during a time window, the time window corresponding to a recent time period, the supply-driven percentage corresponding to a first time proportion associated with one or more supply actions during the time window; as well as determining an emission-driven percentage during the time window, the emission-driven percentage corresponding to a second time proportion associated with one or more emission actions during the time window, Fault detectors for: determining a difference in at least one of a pressure in the actuator or a position of a flow control member in the valve for a time period after the first time point when at least one of: (1) the supply actuation percentage remains above a supply actuation threshold as the time window advances through the time period, or (2) the exhaust actuation percentage remains above an exhaust actuation threshold as the time window advances through the time period; as well as When the difference satisfies a fault threshold, a fault is detected in at least one of: the supply converter, the exhaust converter, the supply relay, or the exhaust relay. 2 . The apparatus of claim 1 , wherein the supply actuation threshold and the exhaust actuation threshold are greater than 75%. 3 . The apparatus of claim 1 , wherein the current is a first current, the digital input signal triggering application of a second current after application of the first current, the second current being lower than the first current.

4. The apparatus of claim 3 , wherein the digital input signal is a first digital input signal, the input signal generator automatically providing a second digital input signal to the first converter in response to the fault detector detecting the fault, the second digital input signal triggering subsequent application of the first current to the first converter to turn on the first converter.

5. The apparatus according to any one of claims 1 to 2, wherein the digital input signal is a first digital input signal, and the current is a first current, the input signal generator automatically provides a second digital input signal to a second converter in response to the fault detector detecting the fault, the second converter corresponding to one of the supply converter or the exhaust converter that is different from the first converter, the second digital input signal triggering application of a second current to the second converter to shut down the second converter.

6. The apparatus according to any one of claims 1 to 4, wherein the fault detector records the fault in a memory.

7. The apparatus according to any one of claims 1 to 4, further comprising a communication interface for reporting the fault to a controller in the process control system.

8. The apparatus of any one of claims 1-4, wherein the fault threshold corresponds to a percentage of at least one of a pressure operating range of the actuator or a calibrated travel span of the valve. 9 . The apparatus of claim 8 , wherein the difference satisfies the fault threshold when the difference is less than the fault threshold, the fault threshold being less than 10% of the corresponding pressure operating range or the calibrated travel span.

10. A computer-readable medium comprising instructions that, when executed, cause a machine to at least: providing a digital input signal to a first converter at a first point in time, the first converter corresponding to one of a supply converter or a drain converter, the supply converter being configured to control actuation of a supply relay to deliver pressurized fluid to an actuator operatively coupled to a valve in a process control system, the drain converter being configured to control actuation of a drain relay to drain the pressurized fluid from the actuator, the digital input signal triggering application of a current to the first converter to open the first converter; determining a supply-driven percentage during a time window, the time window corresponding to a recent time period, the supply-driven percentage corresponding to a first time proportion associated with one or more supply actions during the time window; determining an emission-driven percentage during the time window, the emission-driven percentage corresponding to a second time proportion associated with one or more emission actions during the time window, determining a difference in at least one of a pressure in the actuator or a position of a flow control member in the valve for a time period after the first time point when at least one of: (1) the supply actuation percentage remains above a supply actuation threshold as the time window advances through the time period, or (2) the exhaust actuation percentage remains above an exhaust actuation threshold as the time window advances through the time period; as well as When the difference satisfies a fault threshold, a fault of at least one of: the supply converter, the exhaust converter, the supply relay, or the exhaust relay is detected.

11. The computer-readable medium of claim 10, wherein the supply-driven threshold and the exhaust-driven threshold are greater than 75%.

12. The computer-readable medium of claim 10, wherein the current is a first current, the digital input signal triggering application of a second current after application of the first current, the second current being lower than the first current.

13. The computer-readable medium of claim 12, wherein the digital input signal is a first digital input signal, the instructions further causing the machine to automatically provide a second digital input signal to the first converter in response to detecting the fault, the second digital input signal triggering a subsequent application of the first current to the first converter to turn on the first converter.

14. The computer-readable medium of any one of claims 10-11, wherein the digital input signal is a first digital input signal and the current is a first current, the instructions further causing the machine to automatically provide a second digital input signal to a second converter in response to detecting the fault, the second converter corresponding to one of the supply converter or the exhaust converter that is different from the first converter, the second digital input signal triggering application of a second current to the second converter to shut down the second converter.

15. The computer-readable medium of any one of claims 10-13, wherein the instructions further cause the machine to log the fault in a memory.

16. The computer-readable medium of any one of claims 10-13, wherein the instructions further cause the machine to report the fault to a controller in the process control system.

17. The computer-readable medium of any one of claims 10-13, wherein the fault threshold corresponds to a percentage of at least one of a pressure operating range of the actuator or a calibrated travel span of the valve.

18. The computer-readable medium of claim 17, wherein the difference satisfies the fault threshold when the difference is less than the fault threshold, the fault threshold being less than 10% of the corresponding pressure operating range or the calibrated travel span.

19. A method comprising: providing a digital input signal to a first converter at a first point in time, the first converter corresponding to one of a supply converter or a drain converter, the supply converter being configured to control actuation of a supply relay to deliver pressurized fluid to an actuator operatively coupled to a valve in a process control system, the drain converter being configured to control actuation of a drain relay to drain the pressurized fluid from the actuator, the digital input signal triggering application of a current to the first converter to open the first converter; determining a supply-driven percentage during a time window, the time window corresponding to a recent time period, the supply-driven percentage corresponding to a first time proportion associated with one or more supply actions during the time window; determining an emission-driven percentage during the time window, the emission-driven percentage corresponding to a second time proportion associated with one or more emission actions during the time window; determining a difference in at least one of a pressure in the actuator or a position of a flow control member in the valve for a time period after the first time point when at least one of: (1) the supply actuation percentage remains above a supply actuation threshold as the time window advances through the time period, or (2) the exhaust actuation percentage remains above an exhaust actuation threshold as the time window advances through the time period; as well as When the difference satisfies a fault threshold, a fault is detected in at least one of: the supply converter, the exhaust converter, the supply relay, or the exhaust relay.

20. The method of claim 19, wherein the supply actuation threshold and the exhaust actuation threshold are greater than 75%.

21. The method of claim 19, wherein the current is a first current, and the digital input signal triggers application of a second current after application of the first current, the second current being lower than the first current.

22. The method of claim 21 , wherein the digital input signal is a first digital input signal, the method further comprising: A second digital input signal is automatically provided to the first converter in response to detecting the fault, the second digital input signal triggering subsequent application of the first current to the first converter to turn on the first converter.

23. The method according to any one of claims 19-20, wherein the digital input signal is a first digital input signal and the current is a first current, the method further comprising: In response to detecting the fault, a second digital input signal is automatically provided to a second converter, the second converter corresponding to one of the supply converter or the exhaust converter that is different from the first converter, the second digital input signal triggering application of a second current to the second converter to shut down the second converter.

24. The method of any one of claims 19-22, further comprising recording the fault in a memory.

25. The method of any one of claims 19-22, further comprising reporting the fault to a controller in the process control system.

26. The method of any one of claims 19-22, wherein the fault threshold corresponds to a percentage of at least one of a pressure operating range of the actuator or a calibrated travel span of the valve.

27. The method of claim 26, wherein the difference satisfies the fault threshold when the difference is less than the fault threshold, the fault threshold being less than 10% of the corresponding pressure operating range or the calibrated travel span.

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