Abstract:
An actuator system includes a piston-cylinder arrangement including a piston that is movable with respect to a cylinder. A first flow path is in fluid communication with the piston-cylinder arrangement and a second flow path is in fluid communication with the piston-cylinder arrangement. A control system is operable to fluidly connect the first flow path to a source of high-pressure fluid and to connect the second flow path to a drain to move the piston in a first direction. A pressure sensor is fluidly connected to the first flow path and is operable to measure sufficient pressure data during the movement of the piston to generate a pressure versus time curve. The control system is operable to compare the generated pressure versus time curve to a known standard pressure versus time curve stored in the control system to determine the condition of the piston-cylinder arrangement.

Description:
RELATED APPLICATION DATA 
     This application claims priority to U.S. Provisional Application No. 61/636,431 filed Apr. 20, 2012, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND  
     The present invention relates to system and method for predicting the condition of a cylinder. More specifically, the invention relates to a system and method that uses pressure or another parameter to determine the condition of a pneumatic or hydraulic cylinder. 
     Pneumatic and hydraulic cylinders are used throughout industry to operate equipment in manufacturing lines and to provide a motive force for various components. Over time, the operation of these cylinders can degrade. However, often, the degradation in performance is not detected until an ultimate failure of the cylinder occurs. If a user is unprepared for the failure, it can result in substantial down time or costs. 
     SUMMARY 
     In one embodiment, the invention provides a system that uses one or more pressure sensors to monitor the condition of a cylinder. The system includes a microprocessor/controller that compares measured pressure data to a known baseline for a particular cylinder performing a known function to determine if the operation is acceptable. The system can be standalone or part of a distributed control system. In some constructions, the system can include position sensors that detect the actual position of a piston within the cylinder. 
     In another construction, the invention provides an actuator system that includes a piston-cylinder arrangement including a piston that is movable with respect to a cylinder. A first flow path is in fluid communication with the piston-cylinder arrangement and a second flow path is in fluid communication with the piston-cylinder arrangement. A control system is operable to fluidly connect the first flow path to a source of high-pressure fluid and to connect the second flow path to a drain to move the piston in a first direction. A pressure sensor is fluidly connected to the first flow path and is operable to measure sufficient pressure data during the movement of the piston to generate a pressure versus time curve. The control system is operable to compare the generated pressure versus time curve to a known standard pressure versus time curve stored in the control system to determine the condition of the piston-cylinder arrangement. 
     In another construction, the invention provides an actuator system that includes a cylinder defining an internal space and including a first fluid port disposed adjacent a first end of the space and a second fluid port adjacent the second end of the space. A piston is disposed within the internal space and is operable to divide the space into a first side and a second side, the first side in fluid communication with the first fluid port and the second side in fluid communication with the second fluid port. A working member is coupled to the piston and is operable to perform work in response to movement of the piston and a control system is operable to selectively fluidly connect the first fluid port to one of a pressure source and a drain and to connect the second fluid port to the other of the drain and the pressure source to selectively move the piston away from the first port and toward the first port. A pressure sensor is in fluid communication with the first side and is operable to measure pressure data during movement of the piston. The control system is operable to compare the measured pressure data to a known standard to determine the condition of the system. 
     In yet another construction, the invention provides a method of predicting a failure in an actuator system. The method includes porting a high-pressure fluid to a first side of a piston-cylinder arrangement, draining a low-pressure fluid from a second side of the piston-cylinder arrangement to allow the piston to move with respect to the cylinder toward the second side, and taking a plurality of pressure measurements of the fluid adjacent the first side during the movement of the piston. The method also includes comparing the plurality of pressure measurements to a known set of pressure values and determining if a failure is likely based on the comparison of the plurality of pressure measurements to the known set of pressure values. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of one possible arrangement of a system embodying the invention; 
         FIG. 2  is a plot illustrating measured pressure values versus time for a new actuator in the horizontal position with no load and no damping; 
         FIG. 3  is a plot illustrating measured pressure values versus time for a actuator in the same arrangement as that of  FIG. 2 , wherein the actuator is known to be damaged; 
         FIG. 4  is a plot illustrating measured pressure values versus time for a new actuator in the horizontal position with no load but with damping; 
         FIG. 5  is a plot illustrating measured pressure values versus time for a actuator in the same arrangement as that of  FIG. 4 , wherein the actuator is known to be damaged; 
         FIG. 6  is a plot illustrating measured pressure values versus time for a new actuator that has a larger diameter than the actuator of  FIGS. 2-5  arranged in the horizontal position with no load but with damping; 
         FIG. 7  is a plot illustrating measured pressure values versus time for a actuator in the same arrangement as that of  FIG. 6 , wherein the actuator is known to be damaged; 
         FIG. 8  is a plot illustrating measured pressure values versus time for a new actuator in the vertical position with a load and with damping; 
         FIG. 9  is a plot illustrating measured pressure values versus time for a actuator in the same arrangement as that of  FIG. 8 , wherein the actuator is known to be damaged; 
         FIG. 10  is a schematic illustration of the arrangement of  FIG. 1  and further including a position measurement system; 
         FIG. 11  is a schematic illustration of a multi-actuator system including a distributed control system; 
         FIG. 12  is a screen image of a monitoring system for use in monitoring the performance and condition of one or more actuators; 
         FIG. 13  is another screen image of the monitoring system of  FIG. 12  for use in monitoring the performance and condition of one or more actuators; 
         FIG. 14  is an image of baseline test results for a known actuator; 
         FIG. 15  is an image of test results for the known actuator of  FIG. 14  with a defective shaft or rod seal; 
         FIG. 16  is an image of test results for the known actuator of  FIG. 14  with a defective rod-side piston seal; and 
         FIG. 17  is an image of test results for the known actuator of  FIG. 14  with a defective rear head (opposite the rod) piston seal. 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
       FIG. 1  illustrates a system  10  that is suitable for use in predicting or evaluating the condition of an actuator  15  (e.g., pneumatic, hydraulic, etc.) or valve. The system  10  includes a cylinder  17 , a first pressure sensor  20 , a second pressure sensor  25 , and a microprocessor  30 . The illustrated actuator  15  is a typical double acting actuator  15  having a port  35  at either end of a cylinder  17 , a piston  40  disposed between the ports  35  and a rod  45  extending from the piston  40  and out one end of the cylinder  17 . The piston  40  divides the cylinder  17  into a first chamber  50  and a second chamber  55 . Each of the chambers  50 ,  55  provides a variable volume that allows for movement of the piston  40 . As one of ordinary skill in the art will realize, the system  10  described herein can be applied to different types of actuators (e.g., rodless) and can be used with actuators powered with different working fluids (e.g., hydraulic fluid, oils, water, fuel, air, other gases, other liquids, etc.). In addition, while the illustrated actuator is not biased in any direction, this system could be applied to spring return actuators as well. In fact, the actual design of the actuator or valve is largely irrelevant as the invention can be adapted to many designs. 
     The working fluid is admitted into one port  35  and allowed to drain or escape from the other port  35  to move the piston  40  and rod  45  away from the port  35  in which fluid is being admitted. Because a large pressure differential exists during movement of the piston  40 , a seal  60  is provided between the piston  40  and the cylinder  17 . After some amount of use, this seal  60  can wear or otherwise degrade creating one point where failure may occur. A second seal  65  is provided at the end of the cylinder  17  through which the rod  45  extends. This second seal  65  reduces the amount of working fluid that escapes at the rod opening. Through use, this seal  65  can wear or otherwise degrade creating a second point of possible failure. 
     Typically, one or more valves  70  are used to direct the working fluid to and from the ports  35  as required to produce the desired movement. In a preferred arrangement, a three-way valve  70  allows the first port  35  to be open to a pressure supply  75  and the second port  35  to be opened to a drain  80  in a first position. In a second position, the ports  35  are reversed so that the first port  35  is open to the drain  80  and the second port  35  is open to the pressure supply  75 . The first position and the second position produce movement of the piston  40  and rod  45  in opposite directions. The valve  70  also provides a third operating position in which both ports  35  are closed, thereby trapping the working fluid on both sides of the piston  40 . The third position allows the piston  40  and rod  45  to be positioned and held at some point intermediate of the two extremes. In addition, variable flow rate valves or other flow control devices can be employed to control the rate of fluid flow into or out of the ports  35  to control the speed, acceleration, and exact position of the piston  40  and rod  45  as it moves. 
     With continued reference to  FIG. 1 , the first pressure sensor  20  is positioned to measure a pressure within the first chamber  50  and the second sensor  25  is positioned to measure a pressure within the second chamber  55 . In the illustrated construction, the first sensor  20  is positioned within a first sensor port  85  that is spaced apart from the fluid port  35  already provided in the first chamber  50  of the cylinder  17 . Similarly, the second sensor  25  is positioned within a second sensor port  90  that is spaced apart from the fluid port  35  already provided in the second chamber  55  of the cylinder  17 . In other constructions, the pressure sensor  25  might be connected in line with the fluid lines that connect to the cylinder  17  and the valve  70  or may be connected to a tap line that extends from the feed line or the cylinder chambers  50 ,  55  as may be desired. 
     The pressure sensors  20 ,  25  preferably have a range of sensed pressures that exceeds 150 psi with an accuracy of about 0.01 psi with more or less accurate sensors also being possible. Of course, sensors operating at 250 psi or higher are also possible. Additionally, the sensor  20 ,  25  is preferably sized to provide a response time that allows for data acquisition at a rate of about 1000 data points per second. Of course other pressure sensors could be employed if desired. For example, in one construction, sound pressure sensors, audio sensors, or other vibration sensors are employed to measure the desired operating characteristics of the actuator  15 . 
     In preferred constructions, the pressure sensors  20 ,  25  are removably connected to the actuator  15  so that they may be reused with subsequent actuators  15 . Alternatively, the pressure sensors  20 ,  25  can be manufactured as part of the actuator  15  and replaced with the actuator  15 . 
     The pressure sensors  20 ,  25  convert the measured pressures within their respective chambers into a pressure signal that is transmitted to the microprocessor/controller  30 . In preferred constructions, the microprocessor/controller  30  is dedicated to capture data, stream data and/or analyze for faults or control values. Also, a data logger function can be provided to capture the number of operating cycles, minimum and maximum temperatures, maximum pressures, etc. Each microprocessor/controller  30  can include a unique ID. In the construction illustrated in  FIG. 1 , a wired connection is illustrated. However, wireless connections such as infra-red, radio frequency and the like are also possible. The microprocessor/control  30  receives the pressure signals and compares the signals to known signals for actuators  15  to make decisions regarding the performance and condition of the actuator  15  to which it is connected. The microprocessor/controller  30  may include indicators such as lights or audio devices that can be actuated when a particular condition is detected. For example, a red light could be provided and illuminated when excessive wear or damage to the actuator  15  is detected. The microprocessor/controller  30  may have additional inputs (e.g., ambient temperature, pressure, control signals, etc.) and is provided with multiple output options (e.g., Ethernet, RS-485/422, RS-232, USB, RF, IR, LED blink code, etc.). As noted the microprocessor/controller  30  can perform the necessary comparisons and make decisions regarding the operation, maintenance, or condition of the actuator  15  or can transfer the raw data or decision information to a central computer that then displays the information for one or more actuators  15  to a user. Additionally, the microprocessor/controller can perform data logging functions and store data relating to virtually any measured parameter such as but not limited to the number of cycles, maximum and minimum pressures or temperatures, number of faults, etc. 
     In operation, the present system  10  can be applied to virtually any actuator  15  performing any operation. However, as one of ordinary skill in the art will realize, the performance of any given actuator  15  will vary with the load applied, the positioning of the actuator  15  and the load, the size of the actuator  15 , the distance from the pressure source  75 , and any number of other variables. As such, the preferred approach is to measure the performance of a known actuator  15  in the particular application and use that measured data as a baseline. The baseline represents an acceptable motion profile and is compared to the measured profiles by the microprocessor/controller  30 . This comparison is then used to determine fault condition and reporting. 
       FIG. 2  illustrates an example of one such baseline measurement that is exemplary and includes pressure measured and plotted versus time. As can be seen, the pressure varied between about 10 psi and 95 psi with other pressure ranges being possible. In addition, the entire stroke of the piston  40  in a first direction takes about 100 ms with faster or slower strokes being possible. In addition, the stroke in one direction can be faster than the stroke in the opposite direction due to the reduced piston area caused by the rod  45 . 
     With continued reference to  FIG. 2 , there are two curves  95 ,  100  where each curve  95 ,  100  represents data from one of the pressure sensors  20 ,  25 . The first pressure sensor  20  is measuring a pressure of slightly more than 10 psi and is therefore connected to the drain  80 . The second pressure sensor  25  is measuring slightly above 90 psi and is connected to the high pressure source  75 . Thus, the piston  40  is displaced to an extreme end nearest the first pressure sensor  20 . At a first time, the control valve  70  is moved to the second position such that the first chamber  50  and therefore the first pressure sensor  20  are exposed to the high pressure fluid  75  and the second chamber  55  and therefore the second pressure sensor  25  are opened to the drain  80 . The pressure within the second chamber  55  immediately begins to drop, following a substantially exponential curve. Simultaneously, the pressure within the first chamber  50  rises substantially linearly to a first pressure level. Upon reaching the first pressure level, the force produced by the high pressure fluid on the piston  40  overcomes the piston&#39;s mechanical inertia and any sticking friction and the piston  40  begins to move toward the second pressure sensor  25 . The movement of the piston  40  increases the volume in the first chamber  50 , thereby causing a drop in pressure to a level below the first pressure. Simultaneously, the volume within the second chamber  55  is reduced and the pressure drops toward a lower level at an accelerated rate. Once the piston  40  reaches its end of travel, the pressure within the first chamber  50  increases to a level about equal to the pressure of the high pressure source  75  and the pressure within the second chamber  55  drops to a level about equal to the drain pressure  80 . 
     As illustrated in  FIG. 2 , movement in the opposite direction produces similar curves with slightly different pressure values and durations. The variations in the pressures and the durations are mainly due to the non-symmetric configuration of the chambers  50 ,  55 . For example, the first pressure required to overcome inertia and sticking friction is lower in the one direction of  FIG. 2  because the piston area is slightly larger due to the omission of the rod  45  on the second chamber side of the piston  40 . The total force on the piston  40  is about the same in both directions. Of course, if a load is applied, this relationship and the values will change based at least in part on that load. 
       FIG. 3  illustrates the same type of actuator  15  performing the same operation as the actuator  15  of  FIG. 2 . However, the actuator  15  of  FIG. 3  is known to be defective. A comparison of the curves  110 ,  115  of  FIG. 3  that correspond with the curves  95 ,  100  of  FIG. 2  illustrates several differences. For example, the magnitude  120  of the first pressure required to initiate movement of the piston  40  is noticeably higher in  FIG. 3  than it is in  FIG. 2 . In addition, once piston movement begins, the pressure within the first chamber  50  drops more significantly than it does with the actuator  15  of  FIG. 2 . Thus, the pressure variation within the first chamber  50  during piston motion is larger with the damaged actuator  15  of  FIG. 3  when compared to the good actuator  15  of  FIG. 2 . 
     The curve representing the data measured by the opposite pressure sensor is also different between  FIG. 2  and  FIG. 3 . For example, the high pressure value  125  that is maintained prior to moving the valve  70  is lower in  FIG. 3  than it is in  FIG. 2 . In addition, when opened to the drain, the pressure within the second chamber  55  drops faster in the cylinder of  FIG. 3  when compared to the cylinder of  FIG. 2 . 
     The differences between the two curves  110 ,  115  can also be illustrative of possible problems with the cylinder. For example, the difference between the maximum pressure within the second chamber  55  prior to switching the valve  70  and the first pressure required to initiate movement  120  of the piston  40  is significantly different between  FIG. 2  and  FIG. 3 . Additionally, the pressure difference between the two chambers  50 ,  55  during motion of the piston  40  and at the end of the piston&#39;s stroke is much smaller for the actuator  15  of  FIG. 3  when compared to the actuator  15  of  FIG. 2 . 
     As noted, the loading and positioning of the actuator  15 , along with many other factors, greatly affect the pressure data collected by the pressure sensors  20 ,  25 .  FIGS. 4 and 5  illustrate actuators  15  similar to the actuators  15  of  FIGS. 2 and 3  respectively but with the addition of damping to slow the movement of the piston  40 . Again, there are differences in the curves that are identifiable and that could be used to assess the condition of the actuators  15 ; however the curves are very different from those of  FIGS. 2 and 3 . 
       FIGS. 6 and 7  illustrate the same actuator  15  during horizontal operation with no load and no damping. The actuator  15  is a larger diameter than the actuator  15  used to produce  FIGS. 2-5 .  FIG. 6  is data from a new actuator  15  with  FIG. 7  illustrating data from an actuator  15  that is known to be damaged 
       FIGS. 8 and 9  illustrate a vertically mounted actuator  15  with a load and with damping.  FIG. 8  is data from a new actuator  15  with  FIG. 9  illustrating data from an actuator that is known to be damaged. 
     In addition to measuring the pressure in the first chamber  50  and the second chamber  55 , the system  10  is also capable of measuring the total time duration of the stroke and counting the total cycles or strokes of the piston  40 . Both of these values can be used for maintenance cycle purposes or to evaluate the condition of the actuator  15 . For example, the microprocessor/controller  30  could actuate a colored light to indicate that a predetermined number of cycles has occurred and routine maintenance should be performed or the actuator  15  should be replaced. The system  10  can also measure and monitor the maximum operating pressures and signal an alarm if one or more of the operating pressures are exceeded. 
     Other parameters could be monitored using the first sensor  20  and the second sensor  25  or additional sensors could be provided to monitor other parameters. For example, a temperature sensor could be coupled to the actuator  15  to monitor working fluid temperature, cylinder metal temperature, or any other temperature desired. The temperature data could be used to compensate for the effects of temperature on the operating pressure. 
     In addition to the monitoring functions described above, the system  10  can also be used to more directly control the operation of the actuator  15 . For example, the microprocessor/controller  30  could provide control signals to the valve  70  or valves controlling the flow of fluid to the actuator  15  to control the speed at which the piston  40  moves or the total force generate by the piston  40 . In addition, the present system  10  is capable of detecting the end of travel and stopping the piston  40  at that point or prior to that point if desired. 
     Another construction of a system  150  includes a position measurement system  155  that is capable of determining the actual position of the piston  40  within the cylinder  17 . The cylinder  17  illustrated schematically in  FIG. 10  is identical to that of  FIG. 1  but includes the position measurement system  155 . The position measurement system  155  includes a plurality of magnetic sensors  160  spaced along the length of the cylinder  17 . Each sensor  160  is capable of accurately measuring the angle  165  between it and another magnet  170  such as a magnet  170  placed within or coupled to the piston  40 . A signal indicative of the angle  165  is sent from each sensor  160  to the microprocessor/controller  30 . The microprocessor/controller  30  uses the various angles to triangulate and calculate the precise position of the piston  40 . This positional data can then be used to control the valves  70  to accurately control the position of the piston  40  at any time. This position information can also be used independently or in addition to other sensors for control and/or monitoring purposes. 
     The systems  10 ,  150  described herein can be used alone to monitor and control the operation of a single actuator  15 . The system can signal when the condition of the actuator  15  changes significantly, can signal when maintenance is required and could signal when a replacement actuator  15  or seal is required. In addition, the system could be used to control the operation of the individual actuator  15 . 
     In another arrangement, the various microprocessor/controllers  30  communicate with a central computer  170  as illustrated in  FIG. 11 . The central computer  170  is part of a distributed control system (DCS) that can monitor and control the individual actuators  15  from one location as may be required. 
       FIGS. 14-17  illustrate actual test results for a known actuators in good condition and the same actuator with three different known defects.  FIGS. 14-17  illustrate one possible way in which the present system can be employed. Other types of actuators may have different failure modes and may therefore require slightly different analysis. In addition, the absolute pressures, times, and cycles discloses herein are exemplary and could vary depending on many factors including the application or actuator being used. However,  FIGS. 14-17  are exemplary of one possible use for the system. 
       FIG. 14  illustrates a baseline measurement of a known actuator that is known to be in a good or acceptable condition. The actuator includes a shaft or rod seal a rod-side piston seal and a head piston seal positioned on the opposite side of the piston as the rod side seal. Any one of these seals can fail during use of the actuator and the present system is able to detect that failure before the actuator becomes unusable. As can be seen, the system generates waveforms (or curves) based on pressure measurements taken from both sides of the piston. As illustrated, three specific data points  301 ,  302 , and  303  are identified. These three data points will be discussed with regard to the  FIGS. 15-17  as these points move in response to particular failures. In addition, it should be noted that the maximum pressure of each side of the cylinder are substantially equal. This is typical of a good cylinder but is a function of any pressure or flow regulator that may be positioned upstream of the fluid ports. Additionally, the low pressure of each wave form is about equal to atmospheric pressure as is typical in a good actuator. 
       FIG. 15  illustrates similar waveforms for an identical actuator of that of  FIG. 14  but with a known defect. Specifically, the rod seal is known to be damaged. As can be seen, the two waveforms no longer intersect at the first data point  301 . Rather, there is now a 2 psi difference between the two points  301   a  and  301   b  and they have shifted upward from the original 57 psi value. In addition, the second point  302  has shifted downward from 62 psi to 53 psi and the third point  303  has shifted downward from 55 psi to 48 psi. In addition, the maximum pressures of the two waveforms are different as a result of the defect. Any or all of these differences can be used to determine, not only that the actuator is operating abnormally but that the cause of the abnormal operation is likely a defective rod seal. 
       FIG. 16  illustrates similar waveforms for an identical actuator of that of  FIG. 14  but with a known defect. Specifically, the rod side piston seal is known to be damaged. As can be seen, the two waveforms now include many differences. For example, the first point  301  has shifted upward about 3 psi. In addition, the second point  302  has shifted downward from 62 psi to 55 psi and the third point  303  has shifted downward from 55 psi to 49 psi. These changes are similar to those discussed with regard to the waveforms of  FIG. 15 . However, the maximum pressure of the two waveforms now has a difference of about 3.5 psi. This is a larger difference than that seen as a result of the damaged rod seal. Furthermore, unlike with the damaged rod seal, the waveforms of  FIG. 16  also show a pressure difference between the minimum pressures. Specifically, a difference of 1.5 psi is clearly visible. This difference was not present as a result of the defective rod seal. Thus, these differences can be used to determine, not only that the actuator is operating abnormally but that the cause of the abnormal operation is likely a defective rod side piston seal. 
       FIG. 17  illustrates similar waveforms for an identical actuator of that of  FIG. 14  but with a known defect. Specifically, the head side piston seal is known to be damaged. As can be seen, the two waveforms now include many differences when compared to the waveforms of FIG.  14  as well as the waveforms of  FIGS. 15 and 16 . For example, the first point  301  has not shifted when compared to the waveforms of  FIG. 14 . This is different than what is seen in  FIGS. 15 and 16 . Similarly, the second point  302  and the third point  303  have remained largely unchanged when compared to the waveforms of  FIG. 14 . Thus, looking only at these three points, one would conclude that the actuator of  FIG. 17  is in a good condition. However, the maximum pressure of the two waveforms now has a difference of greater than 3 psi. This difference is similar in magnitude to that of  FIG. 16  but the direction is reversed (i.e., the opposite sensor is higher). 
     Furthermore, like the waveforms of  FIG. 16 , the waveforms of  FIG. 17  show a pressure difference between the minimum pressures. Specifically, a difference of about 2 psi is clearly visible. Like the maximum pressure difference, this difference was present in the waveforms of  FIG. 16 , but again the direction is reversed (i.e., the opposite sensor is low). Thus, these differences can be used to determine, not only that the actuator is operating abnormally but that the cause of the abnormal operation is likely a defective head side piston seal. 
     It should be noted that the actuators used to generate the waveforms of  FIGS. 14-17  were unloaded. As such, there was very little variation in the cycle times (the X-axis) as a result of the defects. However, in loaded cylinders, the defects discussed above also cause measurable variations in the cycle times. These variations can be measured and reported and can also be used to assess the status of the actuator. In addition to using time variations to determine if potential problems have occurred, some constructions utilize the area under the curve to assess if problems are occurring. More specifically, the area between the curves can be used in situations where the actuator is operated at varying pressures or at varying rates. In these situations, it has been found that the total area under the curve remains substantially uniform. Thus, an increase in this area is indicative of unwanted leakage or other performance failures. In other applications, variations in the area between the curves may be indicative of a particular failure mode alone or in combination with other measured parameters. 
     Furthermore, the start and the end of a cycle can be easily detected and reported for use in both controlling a process as well as accessing the condition of the actuator. In addition, if a cycle time is determined to be faster than necessary, or slower than necessary, the pressure can be adjusted to achieve the desired cycle time, thereby enhancing the quality of the process and possibly reducing the amount of air or compressed fluid used by the actuator. 
       FIGS. 12 and 13  illustrate images of one possible monitoring system for use with the systems discussed herein.  FIG. 12  illustrates status page for the monitoring system. While the status page includes the status of one actuator, multiple actuators could be grouped together and illustrated as desired. The illustrated image includes three performance indicators with the first indicator providing a red, yellow or green status based on the waveform analysis discussed above. The second indicator provides an indication that the end of the stroke has been reached. The third indicator counts actuator cycles and provides an indication of actuator life based on the number of cycles. The life could be the actual useful life of the actuator or could be set to mirror recommended maintenance intervals for a particular sensor. 
     The second area of the status page provides numerical data for various operating parameters of the actuator. Other parameters could be measured and displayed as desired. The third area of the status page provides an efficiency analysis. In this example, the efficiency is based on cycle time. The data displayed is a comparison of the actual cycle time versus the desired cycle time with a space provided to provide recommended corrective action based on the result. In this example, the actuator is moving faster than desired. Thus, the pressure of the fluid could be lowered to slow the actuator and potentially reduce the cost of operation. 
       FIG. 13  illustrated one possible configuration page that provides data specific to the actuator being reviewed. In this example, the bore size, the stroke length, and the total cycle count can be added, stored, and displayed. In addition, the steps required to generate the baseline waveforms ( FIG. 14 ) can be initiated from this page. Finally, alarm set points for any measured parameters can be set with each having a high alarm, a low alarm, and a selector to activate or deactivate the alarm. Finally, a Firmware update status is provided to alert the user when a firmware update is required. 
     It should be noted that the invention is described as being used with an actuator (sometimes referred to as a cylinder, a pneumatic cylinder, or a hydraulic cylinder). However, in other applications, the invention is applied to a valve or any other flow device. A flow device would be any device that controls the flow of a fluid or operates in response to a flow of fluid being directed thereto. As such, the invention should not be limited to actuators alone. 
     Thus, the invention provides a system  10 ,  150  for measuring and controlling the operation of an actuator  15 . The system  10 ,  150  includes pressure sensors  20 ,  25  that are capable of collecting data and a microprocessor/controller  30  capable of analyzing the data to determine the condition of the actuator  15 .