WO2007130215A2

WO2007130215A2 - Digital electronic process controller

Info

Publication number: WO2007130215A2
Application number: PCT/US2007/006275
Authority: WO
Inventors: Richard Parker; Helen W. Miao; William A. Schaeffer; Jason W. Doughty
Original assignee: Parker Hannifin Corporation
Priority date: 2006-05-04
Filing date: 2007-03-12
Publication date: 2007-11-15
Also published as: WO2007130215A3

Abstract

A digital electronic process controller unit (10) for controlling fluid applications is disclosed. The digital electronic process controller unit (10) generally receives a control set point value from a first external device. The control set point value corresponds to a characteristic associated with a valve (22). A signal having a characteristic associated with the valve (22) is sensed by the unit (10). The set point value and the sensed signal are processed in a microcontroller (12) utilizing an algorithm (68) to generate a signal. The associated valve (22) may be adjusted based on the signal. In another embodiment, the microcontroller (12) controls an external device that is logically coupled to the microcontroller (12) based upon one or more of the parameters being monitored and/or controlled by the microcontroller (12). In another embodiment, the microcontroller (12) may receive one or more inputs from an external device and use the inputs to control one or more operations of the process controller unit (10).

Description

DIGITAL ELECTRONIC PROCESS CONTROLLER

Related Application Data

This application claims the benefit of U.S. Provisional Application No. 60/746,400 filed May 4, 2006 and U.S. Provisional Application No. 60/891,451 filed February 23, 2007, both of which are incorporated herein by reference.

Field of the Invention

The invention herein described relates to a digital electronic process controller and related system and method for controlling same. As will be appreciated, principles of the present invention are applicable to a wide variety of fluidic applications.

Background

Numerous mechanical and electrical systems have been devised for controlling fluid flow in industrial and manufacturing environments. Fluid systems that require precise control are employed in numerous phases of industry, including the control of robots, the operation of presses for manufacturing rubber and plastic parts, for tensioning devices in the paper industry, for gas chromatography applications, for flow cytomography applications, etc.

In many of the relevant industrial applications, pressurized fluid is typically circulated from a high pressure source, through a load, and then exhausted to a lower pressure supply or reservoir. A high level of control is generally need to properly control and alter the amount of fluid flowing in such systems in order to achieve the desired results.

There are a variety of drawbacks with conventional prior art electronic pressure and/or flow controllers. One drawback is that such devices are generally dumb devices that do not include any decision making capability. For example, the device is set to a certain pressure and/or flow rate and no other parameters are specified and/or controlled by the electronic pressure and/or flow controllers. Another drawback is the requirement of one or more other devices to sense a condition and generate a control signal to trigger a function and/or operation to be performed by another device. Another drawback is the difficulty in combining a controller with multiple sensors. For example, custom electronics are generally needed for each sensor to properly communicate with the controller. Another drawback is the difficulty in providing access to all process parameters including the. ability to remotely view such parameters over a computer networks, such as the Internet, for example. Another drawback with conventional controllers is the ability to monitor and control multiple channels. Generally such devices are used to control a single channel.

Thus, a need exists for a digital process controller that that overcomes the deficiencies set forth above.

Summary of the Invention The present invention relates to a system and method for controlling fluid flow by a digital electronic process controller unit.

An aspect of the invention relates to a digital electronic pressure controller unit for controlling output pressure for an output port comprising: a first input port for receiving a control set point value from a first external device for use in controlling a physical characteristic associated with a valve; a first output port for coupling to the valve to control operation of the valve; a sensor for sensing a characteristic associated with the valve and generating a sensed signal; a microcontroller for processing the sensed signal and the received control set point value with an algorithm stored in the microcontroller, wherein the microcontroller generates a signal at the first output port for use in controlling the associated valve.

Another aspect of the invention relates to a method for controlling fluid flow, the method comprising: receiving a control set point value. from a first external device for use in controlling a characteristic associated with a valve; sensing a signal having a characteristic associated with the valve; processing the sensed signal and the received control set point value with an algorithm stored in a microcontroller and generating a signal; and adjusting an output port coupled to the associated valve based upon the generated signal.

Another aspect of the invention relates to a method for controlling fluid flow, the method comprising: receiving a control set point value for use in controlling a physical characteristic of a valve; sensing a characteristic associated with the valve with a sensor; processing at least one signal associated with the sensed characteristic and the received control set point value with an algorithm stored in a microcontroller and generating a signal; adjusting the valve based upon the generated signal; and controlling an associated external device logically coupled to the microcontroller based on a control signal generated from the microcontroller.

Another aspect of the invention relates to a method for controlling fluid flow, the method comprising: receiving a control set point value from a host controller at a remote process controller, wherein the control set point value for use in controlling a physical characteristic associated with a valve; sensing a characteristic associated with the valve with a sensor housed within the remote process controller; processing at least one value associated with the sensed characteristic and the received control set point value at the host controller and generating a signal; and receiving a control signal from the host controller at the remote process controller for adjusting the valve based upon the generated signal received from the host controller; and controlling an external device logically coupled to the remote process controller based on a control signal generated from the host controller. To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.

Brief Description of the Drawings Figure 1 is an exemplary schematic block diagram in accordance with aspects of the present invention.

Figures 2 and 3 are exemplary systems in accordance with aspects of the present invention.

Figure 4 and 5 are exemplary methods in accordance with aspects of the present invention.

Detailed Description

In the detailed description that follows, corresponding components have been given the same reference numerals, regardless of whether they are shown in different embodiments of the present invention. To illustrate the present invention in a clear and concise manner, the drawings may not necessarily be to scale.

Aspects of the present invention relate to a system and method of a digital electronic pressure controller unit and/or process controller unit to control output pressure of gas and/or liquid (collectively "fluids") applications for a plurality of output channels (also referred to as output ports) associated with the unit. In general operation, the unit receives a control set point that corresponds to a physical characteristic to be controlled by the unit (e.g., pressure, position, displacement, temperature, etc.) at an input port. An internal sensor (e.g., a pressure sensor, position sensor, displacement sensor, thermometer, etc.) detects the amount of and/or the signal associated with the physical characteristic to be controlled at an output port of the unit. A microcontroller processes the detected signal and/or value and the control set point to generate a signal. The microcontroller adjusts one or more output ports of the unit, which may be coupled to a valve, based on the generated signal. In another embodiment, the microcontroller controls an external device that is logically coupled to the microcontroller based upon one or more of the parameters being monitored and/or controlled by the microcontroller. In another embodiment, the microcontroller may receive one or more inputs from an external device and use the inputs to control one or more operations of the process controller.

Referring to Figure 1 , an exemplary schematic block diagram of a process controller unit 10 in accordance with aspects of the present invent is disclosed. For clarity purposes, the components that are housed within the process controller unit 10 are identified within the dashed line and components that may be coupled to and/or receive an output signal from the process controller 10 are schematically illustrated outside of the dashed line. The input and output ports of the process controller unit 10 may be shown schematically outside of the dashed line for clarity purposes. However, the input and output ports are internally housed in the process controller unit 10. The process controller 10 includes a microcontroller 12, a first sensor 14, a second sensor 16, a first control drive 18, and a second control drive 20. In general operation, a control set point value may be received for the first sensor 14 at a first input port 30. The control set point value may correspond to the physical characteristic (e.g., pressure, displacement, pressure, temperature, etc.) to be controlled by the first control drive 18, which is an output port that drives valve 22. For example, the first sensor 14 may be a pressure sensor that detects the pressure at an output port 18 or other type of sensor depending on the physical characteristic being sensed. The sensor 14 is coupled to valve 22 through an output port (e.g., control drive 18). The microcontroller 12 executes a control algorithm, which determines whether the output port (e.g., control drive 18) should be adjusted by sending a control signal to open the valve, close the valve or leaving the valve unchanged. Likewise, a control set point value may be received for the second sensor 16. The sensor 16 may be a pressure sensor or any type of sensor that detects depending on the physical characteristic to be sensed. Again, the control set point value may correspond to a desired physical characteristic to be controlled (e.g., the desired pressure to be controlled by the output port to second pressure control drive 20, which drives valve 24). The second pressure 16 detects the desired physical characteristic (e.g., pressure) at valve 24. The microcontroller determines whether the valve should be adjusted by opening the valve, closing the valve or leaving the valve unchanged. In the present embodiment, valves 22 and 24 are proportional valves. One of ordinary skill in the art will readily appreciate the valves 22 and 24 may be any type of valve that is capable of being controlled by an electrical signal.

The process controller unit 10 provides closed loop feedback device that may be used to control fluid flow. The process controller unit 10 maintains accurate pressure levels by sending an appropriate signal to open, close and/or control the output device (e.g., valve) with feedback being provided by the corresponding sensors 14 and/or 16.

The sensors 14 and 16 may be pressure transducers that are suitable to monitor pressure at an output port (e.g., ports 18, 20). For example, the sensors may monitor pressure at the output ports (e.g., ports 18, 20) coupled to valves 22 and 24. The sensors 14 and 16 may be used to control inlet valve characteristics, output valve characteristics or any another characteristic associated with the valves 22, 24 or any device connected to the microcontroller through an input and/or output port. Generally, the sensors 14 and 16 convert the sensed pressure to an analog and/or digital signal that corresponds to the sensed pressure. The sensors 14 and 16 may receive digital input signals and/or analog input signals. Analog input signals received are routed through an analog to digital (AJD) converter 26 and converted to corresponding digital signals for use by the microcontroller 12. The A/D converter 26 converts analog signals to digital signals for use by the microcontroller 12. In general, the A/D converter 26 has an output range from 0 Volts to 5 Volts over a 13 bit control line (e.g., a serial peripheral interface (SPI) link). As shown in Figure 1 , the A/D converter 26 may be configured to convert a variety signals for use by the microcontroller 12. For example, the A/D converter 26 may receive input from a manifold air temperature sensor 28, which is housed internally to the process controller 10. The sensor 28 generally measures the temperature of the process controller 10.

In addition, the A/D converter 26 may receive analog signals from external sources. In particular, as shown in Figure 1 , three analog signals from one or more external devices may input to the process controller 10 at analog channel 1 input port 30, analog channel 2 input port 32, and analog channel 3 input port 34. The analog signals may be generated by any type of electronic device. The process controller 10 is generally configured to output a control signal to maintain the desired pressure indicated by set point voltage values associated with the ports 30, 32 and 34. While the process controller 10 is illustrated with three analog port, one of ordinary skill in the art will readily appreciate that the scope of the present invention is not limited to a process controller with three analog inputs.

The process controller unit 10 also allows for bi-directional digital data communication with an RS-232 port 38. The port 38 allows the process controller 10 to be a slave to another electronic device (e.g., a personal computer, a personal digital assistant, host controller, etc.). Thus, the process controller 10 is a robust control device that can utilize its own embedded software to control the fluidic processes or can be a slave to another host controller and/or other computing device. In addition, the process controller unit 10 includes a re-programming connector 40 to allow for modification and/or re-programming of the various software features included in the microcontroller 12. For example, a control algorithm 66 may be modified on a personal computer or other electronic device and downloaded to the microcontroller 12 through the port 38. Likewise, the RS-232 port 38 may also be used to facilitate communication network communications (e.g., viewing various control parameters over a network, e.g., a local area network, a wide area network, the Internet, etc.).

The process controller unit 10 may also include a temperature sensor 42, housed internally to the process controller unit 10. The temperature sensor 42 measures the temperature of the circuit board to allow and may output the temperature to the microcontroller 12 for temperature drift correction. The process controller 10 further includes an input port for allowing a external temperature sensor 44 to be interfaced with the microcontroller 12. This provides the process controller 10 with added functionality. For example, the microcontroller 12 may monitor a temperature sensor and perform an action based on the detected temperature and/or generate a control signal for another device to perform an action.

The process controller further includes an input power port 46. The port 46 generally receives a 12 Volt direct current power supply to provide sufficient electrical power to the process controller 10. In addition, the process controller 10 also includes a reset switch 48 for resetting the microcontroller 12. The reset switch 48 may activated manually and/or electronically by the microcontroller 12. The microcontroller 12 includes a plurality of outputs. As stated above, the microcontroller outputs control signals to output ports (e.g., control drives 18 and 20) to control valves 22 and 24, respectively. In one embodiment, the control drives 18 and 20 generally output a pulse width modulated (PWM) signal to the corresponding valve 22 and/or 24, respectively. It is desirable to provide the valves 22, 24 with a control input of 1 :25000. In order to obtain this resolution the PVVM signal is approximately 14.4 bits. The microcontroller 12 generally operates with an internal oscillator of 118 MHz. In order to provide the 1 :25000 resolution, the PWM signal will operate at approximately 2.36 KHz. Preferably a PWM signal frequency of 4.59 KHz is applied to the valves 22, 24. In addition, the microcontroller 12 includes a plurality (e.g. five) of additional input/output ports. The ports may be configured in a variety of ways. For example, port 50 may be configured to receive input signals for the microcontroller or output signals to an external device. In addition, the output signal from port 50 may be amplified depending on the signal to be output and/or the external device being coupled to the port. In addition, information input from the port 50 and/or output from the microcontroller 12 to port 50 may also be stored internally at block 52.

Like port 50, port 54 may also be configured to receive input signals for the microcontroller 12 or output signals to an external device. In addition, the output signal from port 54 may be amplified depending on the external device being coupled to the port. As shown in Figure 1, ports 56, 58 and 60 are configured to be input/output ports. That is, the ports 56, 58 and 60 may input a signal to the microcontroller 12 and/or receive an output signal from the microcontroller 12.

Figure 1 also illustrates that output signals may be provided to inform the user of the status of one or more parameters associated with the process controller 10. For example, LEDs are provided in the form of a status and/or error display 62. In addition, the user may be provided with a pressure monitor signal output 64 to indicate the amount of pressure in a particular application. One of ordinary skill in the art will readily appreciate that there a variety of parameters that may be displayed and/or presented and/or a variety of formats that may be desirable for display to an associated user, all such variations are deemed to be within the scope of the present invention. The microcontroller 12 is configured to carry out overall control of the functions and operations of the process controller 10. The microcontroller 12 executes code stored in a memory 66 within the microcontroller and/or in a separate memory (not shown), in order to carry out operation of the process controller 10. The separate memory may be, for example, one or more of a buffer, a flash memory, a hard drive, a removable media, a volatile memory, a non-volatile memory or other suitable device. It will be apparent to a person having ordinary skill in the art of computer programming, and specifically in applications programming for microcontrollers or other electronic devices, how to program the process controller 10 to operate and carry out the functions described herein. Accordingly, details as to the specific programming code have been left out for the sake of brevity. Also, while process control is generally controlled by the microcontroller 12 in software, in accordance with the preferred embodiment of the invention, such functionality could also be carried out via dedicated hardware and/or combinations of hardware and software, without departing from the scope of the invention.

For example, the microcontroller 12 is configured to execute code stored in memory 66 and/or in a separate memory (not shown), as discussed above. The memory 66 includes a control algorithm 68 for control of the processes described herein. In one embodiment, the control algorithm 68 is a proportional-integral-derivative (PID) control algorithm.

In general operation, the control algorithm 68 takes a measured value from a process or other apparatus (e.g., sensor inputs 14, 16, 32, 34, 36) and compares it with a reference set point value. The control algorithm then generates a signal to be output from the process control unit 10. One such suitable signal is a difference signal (also referred to as an "error" signal). The error signal may then be used to adjust an input to the process in order to bring the measured value to the desired set point. A PID algorithm is a preferred control algorithm because the PID algorithm can adjust process outputs based on the history and rate of change of the error signal, which gives more accurate and stable control than conventional control algorithms. In addition, the PID algorithm does not generally utilize complex mathematics, which generally takes resources away from the microcontroller 12.

The control algorithm 68 contains a proportional adjustment (e.g., error is multiplied by a constant), an integral adjustment, to account for past error (e.g., the error is integrated and multiplied by a constant I) and a derivative adjustment, to anticipate future error, (e.g., the first derivative (the slope of the error) over time is calculated and multiplied by another constant D). The error is generally found by subtracting the measured quantities from the set point value. During operation, it is desirable that PID algorithm calculations occur at approximately a 500 Hz rate.

Once the signal is generated (e.g., the error is determined and an output signal is generated), the microcontroller 12 is configured to adjust the respective control parameter to produce the desired output. For example, a set point value is received for sensor 14. The set point value may be received from a digital and/or analog source (e.g., port 34, port 38, etc.). A digital representation of the set point value is provided to the microcontroller for use in the control algorithm 68. Sensor 14 receives a signal from an associated pressure transducer and provided to the control algorithm 68 of the microcontroller 12. The sensor measurement and the set point value are processed in the algorithm to determine an associated error value. From the error value, a control signal is output from the microcontroller to the pressure control drive 18. A corresponding PWM signal is provided to the valve 22 to adjust the valve based upon the calculated error signal.

An aspect of the present invention allows for the process controller 10 to provide closed loop feedback for three control parameters for both internal sensors (e.g., pressure sensors) and external sensors (e.g., pressure). For example, referring to Figure 2 an exemplary system 100 is shown. The system 100 includes a process A 102 that provides a control set value to the process controller 10. The process A 102 can be any suitable type of process. Exemplary processes include, for example, temperature, position and detection processes. From the process A 102, a control signal is input to the sensor 16. The sensor 16 senses a physical characteristic associated with the valve (e.g., pressure) at and/or near the valve 24. The microcontroller 12, through the control algorithm 68, controls the output of the process control unit 10 to control valve 24 based on the control signal and the calculated error signal. Figure 2 also illustrates the processor controller 10 triggering and/or generating a control signal to control process B 104. As shown, process B is coupled to the processor controller unit 10 through one the of the I/O ports (e.g., port 50, port 54, port 56, port 58 and port 60). Process B may be any process. For example, process B may be starting and/or controlling a motor, controlling a switch, a relay and/or a heating element.

Referring to Figure 3, another exemplary system 110 is shown. The system 110 includes a process A 102 that provides a control set value to the process controller 10. The process A 102 can be any suitable type of process. Exemplary processes include the processes discussed above. From the process A 102, a control signal is input to the sensor 16. The sensor 16 senses the pressure at the valve 24. The microcontroller 12, through the control algorithm 68, controls the output of valve 24 based on the control signal and the calculated error signal. Figure 3 also illustrates the processor controller 10 receiving an input signal from Input C 112. Input C 112 may be generated from any type of device. Exemplary devices that may provide input in such a manner are sensors that detect variables such as position, temperature, flow, conductivity, fluid level. Input C may be coupled to the processor controller 10 through one the of the I/O ports (e.g., port 50, port 54, port 56, port 58 and port 60). The microcontroller 12, through the control algorithm, may utilize input C for any desired purpose. For example, making control decisions, providing information to otherdevices, etc.

One of ordinary skill in the art will readily appreciate that the systems illustrated in Figures 2 and 3 are exemplary in nature and in no way intended to limit the scope of the present invention. Figures 2 and 3 illustrate a broad concept that the process controller unit 10 may provide closed loop monitoring of external signals, as well as internal signals. In addition, the process controller unit 10 is configured to generate control information based upon the occurrence of an event detected by the microcontroller 12 to control and/or cause an external device to perform a function. Referring to Figure 4, a method 150 in accordance with one aspect of the present invention is illustrated. Method 150 illustrates an exemplary method for controlling fluid flow and/or pressure. At step 152, a control set point value, which corresponds to a desired pressure at an output port of the process controller unit 10 (e.g., at an external device, such as a valve), is received from a first external device. The control set point value may be analog or digital. At step 154, the pressure is measured at the output coupled to the external device (e.g., valve). A pressure transducer converts the measured pressure to a signal that may be provided to the microcontroller. At step 156, a microcontroller, through the use of a control algorithm, processes the sensed pressure and the received control set point value to generate a signal (e.g., an error measurement). At step 158, the valve is adjusted based upon the signal.

Referring to Figure 5, a method 170 in accordance with one aspect of the present invention is illustrated. Method 170 illustrates an exemplary method for controlling fluid flow and/or pressure. At step 172, a control set point value, which corresponds to a desired pressure at an output port of the unit 10 coupled to a valve, is received. At step 174, the pressure at the output port is measured using a sensor (e.g., a pressure signal). At step 176, a microcontroller, through the use of an algorithm, processes the sensed pressure and the received control set point value and generates a signal (e.g., an error measurement). At step 178, the output port is adjusted based upon the signal. At step 180, an external device logically coupled to the microcontroller is controlled based on a control signal generated from the microcontroller.

Computer program elements of the invention may be embodied in hardware and/or in software (including firmware, resident software, microcode, etc.). The invention may take the form of a computer program product, which can be embodied by a computer-usable or computer- readable storage medium having computer-usable or computer-readable program instructions, "code" or a "computer program" embodied in the medium for use by or in connection with the instruction execution system. In the context of this document, a computer-usable or computer-readable medium may be any medium that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer-usable or computer-readable medium may be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium such as the Internet. Note that the computer-usable or computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted, or otherwise processed in a suitable manner. The computer program product and any software and hardware described herein form the various means for carrying out the functions of the invention in the example embodiments.

Although the invention has been shown and described with respect to a certain preferred embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a "means") used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.

Claims

Claims What is claimed is:

1. A digital electronic pressure controller unit (10) for controlling output pressure for an output port (18) comprising: a first input port (30) for receiving a control set point value from a first external device for use in controlling a physical characteristic associated with a valve (22) ; a first output port (18) for coupling to the valve (22) to control operation of the valve (22); a sensor (14) for sensing a characteristic associated with the valve (22) and generating a sensed signal; a microcontroller (12) for processing the sensed signal and the received control set point value with an algorithm (68) stored in the microcontroller (12), wherein the microcontroller (12) generates a signal at the first output port (18) for use in controlling the associated valve (22).

2. The digital electronic pressure controller unit (10) of claim 1 further including a second output port (20, 50, 54, 56, 58, 60, 62) for directly coupling the microcontroller (12) to a second external device for generating a control signal to control the second external device.

3. The digital electronic pressure controller unit (10) of claim 1 further including a second output port (20, 50, 54, 56, 58, 60, 62) for logically coupling the microcontroller (12) to a second external device for generating a control signal to control the second external device.

4. The digital electronic pressure controller unit (10) of any one of claims 1-3, wherein an analog to digital converter (26) is coupled to the microcontroller (12) for converting the control set point value from an analog signal to a digital signal.

5. The digital electronic pressure controller unit (10) of any one of claims 1-4, wherein the sensor (14) is a pressure sensor.

6. The digital electronic pressure controller unit (10) of any one of claims 1-5, wherein the physical characteristic associated with the valve (22) is pressure.

7. The digital electronic pressure controller unit (10) of any one of claims 1-6, wherein the sensor (14), the first input port (30), the first and second output ports (18, 20, 50, 54, 56, 58, 60, 62), the pressure sensor (14) and the microcontroller (12) are housed in a housing.

8. The digital electronic pressure controller unit (10) of any one of claims 1-7, wherein the signal generated by the microcontroller (12) is an error measurement signal that corresponds to the difference between the control set point value and the sensed signal.

9. A method for controlling fluid flow, the method comprising: receiving a control set point value from a first external device for use in controlling a characteristic associated with a valve (22); sensing a signal having a characteristic associated with the valve (22); processing the sensed signal and the received control set point value with an algorithm (68) stored in a microcontroller (12) and generating a signal; and adjusting an output port (18) coupled to the associated valve (22) based upon the generated signal.

10. The method of claim 9 further including the microcontroller (12) generating a control signal for controlling a second external device directly coupled to a second output port (20, 50, 54, 56, 58, 60, 62) of the microcontroller.

11. The method of any one of claims 9-10, further including the microcontroller (12) generating a control signal for controlling a second external device logically coupled to a second output port (20, 50, 54, 56, 58, 60, 62) the microcontroller.

12. The method of any one of claims 19-11, wherein the second external device is at least one selected from the group consisting of: a motor, a switch, a relay or a heating element.

13. The method of any one of claims 9-12, wherein the step of sensing a characteristic associated with the valve is preformed by a pressure sensor.

14. The method of any one of claims 9-13, wherein the control set point value is converted from an analog signal to a digital signal for processing by the microcontroller (12).

15. The method of claim 9, wherein the signal generated by the microcontroller (12) is an error signal that corresponds to the difference between the control set point value and the sensed signal.

16. A method for controlling fluid flow, the method comprising: receiving a control set point value for use in controlling a physical characteristic of a valve (22); sensing a characteristic associated with the valve with a sensor (14); processing at least one signal associated with the sensed characteristic and the received control set point value with an algorithm (68) stored in a microcontroller (12) and generating a signal; adjusting the valve (22) based upon the generated signal; and controlling an associated external device logically coupled to the microcontroller (12) based on a control signal generated from the microcontroller (12).

17. The method of claim 16, wherein the step of sensing a characteristic associated with the valve (22) is preformed by a pressure sensor (14).

18. The method of any of claims 16-17, wherein the control set point value is converted from an analog signal to a digital signal for processing by the microcontroller (12).

19. The method of any of claims 16-18, wherein the signal generated by the microcontroller (12) is an error signal that corresponds to the difference between the control set point value and the sensed signal.

20. A method for controlling fluid flow, the method comprising: receiving a control set point value from a host controller at a remote process controller (10), wherein the control set point value for use in controlling a physical characteristic associated with a valve (22); sensing a characteristic associated with the valve (22) with a sensor

(14) housed within the remote process controller (10); processing at least one value associated with the sensed characteristic and the received control set point value at the host controller and generating a signal; and receiving a control signal from the host controller at the remote process controller (10) for adjusting the valve (22) based upon the generated signal received from the host controller; and controlling an external device logically coupled to the remote process controller (10) based on a control signal generated from the host controller.