Abstract:
A mobile testing apparatus, method, and computer product that performs high speed testing of mobile pressure devices using high speed totalization, where testing of multiple devices may be done concurrently. Test results are communicated to a central console using a variety of communication methods, including wireless, and the testing apparatus and method is robust and reliable despite the occurrence of transient communication failures, because the test apparatus and method may operate independently of central control.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of the earlier filing date of U.S. provisional patent application Ser. No. 60/307,386, filed Jul. 25, 2001, the entire contents of which are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to cavity pressure testing and particularly to HVAC testing of pressurized cavities in an assembly line environment. 
   2. Discussion of the Background 
   HVAC testing is widely employed in the manufacture of automotive vehicles which contain numerous vacuum and pressurized cavities throughout the structure of the vehicles, for example, air conditioning systems and engine systems. The efficient production of high-quality vehicles requires that the vacuum or pressurized systems be tested on the assembly line while the vehicles are being assembled. Because both accuracy and speed are required in this environment, manufacturers generally rely on automated test systems. 
   Among the systems employed by manufacturers for HVAC testing are pressure decay systems, differential pressure decay systems flow meter systems (mass flow rate systems), and totalization of flow (mass flow totalization) systems. 
   A disadvantage of pressure decay systems is that the cavities or pressure lines to be tested must be first evacuated in order to perform the test, and further, the systems must be tested in the absence of pressurized flow. Pressure decay systems are limited to small cavities and are affected by temperature, pressure, and humidity. Differential pressure decay systems are limited to large cavities and are also affected by temperature, pressure, and humidity. Pressure decay systems report only estimated flow rate. 
   A disadvantage of the flow meter systems is that the test cycle time tends to be too long to be practical in a modem vehicle assembly line environment, where the target time for testing is approximately 45 seconds. Flow meter systems typically have cycle times of approximately 90 seconds. Mass flow rate systems are affected by humidity, cavity temperature, excessive cycle duration, and are limited to measuring large cavities. 
   Totalization of flow test systems overcome many of the disadvantages of the above systems. In background art systems which use the totalization of flow principle, a central processor controls test heads which are moved up and down the assembly line and attached to various test points on the vehicles being assembled. Background art test systems utilize test heads that are connected to the central processor via cable connections. A disadvantage, as recognized by the present inventors, of using test heads connected with cables is that moving the test heads from vehicle-to-vehicle is constrained by the length of the cable, and further, the number of test heads that may be attached to a vehicle may be limited because of the difficulty of placing the test heads which are encumbered by the attached cables. 
   The repeatability of test results of a system investigating a specified cavity is dependent on a number of factors including but not limited to atmospheric pressure, atmospheric temperature, atmospheric humidity, cavity material temperature, and cavity material thermal transfer rate. Using empirical formulas, exact results are achieved when all of these parameters are monitored and included in the methods for determining cavity integrity. However, the level of cost associated with this type of system is inappropriate for typical testing conditions. 
   SUMMARY OF THE INVENTION 
   The present invention has been made in view of, and addresses, the above-mentioned and other problems. 
   The present invention advantageously provides a novel totalization of flow test system which features mobile test heads which communicate with a central processing system by way of wireless links. The present inventors have recognized that, in order for test systems which work in real-time to function reliably using relatively unreliable wireless links, the test heads themselves must be intelligent enough to carry on test procedures independently of the central processor. To accomplish this end, the present invention utilizes software algorithms and advanced processing capabilities which reside on the test head and which allow for the reliable testing of HVAC cavities independently from the central control system, and for the reliable transfer of commands and test results between the central control processor and the mobile test heads. 
   To resolve the issue of repeatability, typical testing conditions were observed and the present invention was designed with an “all things being equal” type of approach. Making assumptions as to the stability of temperature, pressure and temperature and utilizing temperature and pressure compensated mass flow meters, the present invention ensures repeatable results with nominal error. 
   In the present invention, during data acquisition, real-time microprocessor based operations monitor and perform calculations to determine cavity integrity. The present invention performs this integrity check as quickly as possible. In attempting to optimize the integrity algorithms and data sampling accuracy, a trade off is necessary for single microprocessor based systems. To resolve this issue, the present invention uses multiple microprocessors. The primary microprocessor receives information from the secondary processors reporting cavity volume. This approach segregates processing and effectively implements a true multitasking environment. Using this approach, the present invention is also very robust in terms of maintaining data integrity throughout a testing process. The secondary microprocessors maintain the information locally until the primary processor has acquired and acknowledge data transfer. This is particularly important for systems that require mobility of the testing device and where interruptions in network traffic may occur. The present invention operates effectively when only 5% of successful network transmissions are present. 
   The present invention evaluates a specified cavity for integrity. Acceptable integrity determination is performed via microprocessor-based evaluation of user definable parameters sets (“recipes”) against realtime performance characteristics of the tested cavity. 
   The present invention is engineered to function in harsh environments and is capable of sustaining and maintaining performance under highly industrial environments including, but not limited to, manufacturing plants, lab environments, foundries, etc. 
   The present invention operates using microprocessor technology in a distributed topology. The testing devices incorporate networking protocols to achieve data migration and reside remote to the primary console. The remote systems perform mass flow totalizing during specified mode conditions. Parameters for integrity validation are transferred to the primary console via network protocols. 
   Standardized database interfaces are used to manage testing parameters. These parameters are interfaced to the primary console. These parameters include, but are not limited to, the following: assembly identification, testing method, mode count, and the necessary testing parameters to thoroughly evaluate the tested cavity. The present invention cycles through selected modes to perform specific tests to determine the integrity of the cavity. If a compromise in integrity is detected, the present invention generates a report with an appropriate diagnostic message to assist the operators in determining problematic areas. 
   Two advantageous features of the present invention are: 
   1) The ability to perform high speed totalizing of the mass flow signals. Background art devices have been evaluated as inadequate and inaccurate due to their inability to accurately capture the primary inrush of the flow signals. The mass flow totalizing performed by the remote microprocessors achieves the speed and accuracy necessary to provide a robust system for industrial applications; 
   2) The ability to evaluate the volume of a cavity. Background art devices simply determine if the cavity has an unacceptable or excessive orifice where molecular migration can occur. The present invention not only determines molecular migration, but also offers advanced diagnostics as to where the failure in integrity may be located. 
   The area of isolating environmental fluctuations from adversely affecting the test result have been significantly improved upon. Also, the area of reported results has been improved to provide more information and a higher level of diagnostics. 
   Features of the present invention include: (a) Utilization of a Voltage to Frequency Converter to change Mass Flow signal into a frequency signal allowing resolutions of 0.01 cc; b) Utilization of a microprocessor-based frequency totalizing module local to the testing station; c) Utilization of a programmable Pressure/Vacuum regulator to perform soft start to prevent over metering of the mass flow transmitter; and d) Utilization of software algorithms to determine common areas of failures. 
   According to an exemplary embodiment of the present invention, the central test system receives product information and recipe information from an application layer. The central test system derives acceptance parameters which are transferred from mobile test heads located at test points of vehicles being processed through an assembly line. The transfer of commands and parameters is done over wireless links employing the Ethernet protocol. A processor in the test head executes software algorithms which perform the totalization of a flow test procedure for a target cavity and transmits the results via the wireless links to the central control system. 
   The potential applications for use of this invention include, but are not limited to, the following: Engine Block Testing; Checking to Hold Pressure Gas Tank Testing; Checking to Hold Pressure; HVAC Plenum Testing; Checking Vacuum System; Headlight Lens Testing; Checking Watertight components; and testing any cavity that is intended to be sealed or nearly sealed with acceptable permeations. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
       FIG. 1  is a block diagram illustrating an example of components and data flows of the present invention; 
       FIG. 2  is an example of a test management console and multiple mobile test heads interconnected with wireless links according to the present invention; 
       FIG. 3  is an example of process flow between the application layer and the test management console according to the present invention; 
       FIG. 4  is an block diagram illustrating an example process flow at the mobile test head according to the present invention; 
       FIGS. 5–7  are an example of flow charts illustrating an example test head testing sequence according to the present invention; 
       FIG. 8  is an example illustrating an example test head assembly according to the present invention; 
       FIG. 9  is a blocked diagram illustrating an example test head assembly according to the present invention; and 
       FIGS. 10–17  are flowcharts illustrating an exemplary process flow according to the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views,  FIG. 1  is a block diagram illustrating an example of the Test System  106  according to the present invention. The Test System  106  receives production information  102  and recipe information  104  from outside applications. Test System  106  conducts measurements  216  on cavity  114  which contains a volume of air at a known pressure or volume. The volume of air is compared against acceptance parameters  108  and the tested cavity is accepted or rejected. The result of the test is sent to outside applications  110  or to local enunciation devices  112 . 
     FIG. 2  is a block diagram illustrating an example of Test Management Console  202  communicating via wireless links with to up to 9 mobile test heads  204 , where each mobile test head  204  may conduct an independent test simultaneously with tests performed by other mobile test heads. Each of the test heads  204  communicate with the Test Management Console  202  via a wireless Ethernet, allowing the test heads to be mobile (speeds up to 30 m.p.h.) and to be positioned to up to 60 miles from the Test Management Console  202 . The Mobile Test Heads  204  have the capability of performing leak detection on the same cavity while the cavity undergoes multiple test mode changes. Totalizing of evacuating error is performed for each mode change for recipe comparison. 
     FIG. 3  is a block diagram illustrating an example software sequence of the present invention. The Test Management Console  306  maintains a Production Test Queue (PTQ)  306  local to the system. The Production Test Queue will queue information pushed down from the middle tier of the application layer  302 . This information contains all of the necessary Parameters and Descriptions  322  for test performance and test result reporting. The Test Management Console  306  monitors the Production Test Queue  304  and responds to new information. When there is an item in the Production Test Queue  304 , the top item waits for a new connection to a test head  310 . Once the connection  332  is made over a wireless link  330 , the testing information  334  is transferred to the respective Test Head  310 . The Production Test Queue  304  top item is transferred to a local In Process Queue (IPQ)  308 . A testing sequence is performed and a test result is written to the In Process Queue record  308 . The In Process Queue is managed by waiting for a test result on the top item in the queue. When a test result is received, the In Process Queue sends a notification  320  to the Middle Tier Application  302  that Results  324  are available for extraction. 
     FIG. 4  is a block of diagram illustrating an example hardware configuration of an exemplary mobile test head according to the present invention. Media (i.e. air, helium, oxygen, etc.)  408  will be evacuated from or pumped into a cavity  420  as required for the particular application. The method of media management is supplied from an outside source. The media monitoring circuit includes the following: Electronic Vacuum or Pressure Regulator (EVPR)  404 ; on/off Solenoid Controlled Valve (SCV)  410 ; thermal type Mass Flow Meter (MFM)  402 ; High-Speed Voltage to Frequency Module (HSVFM)  416 ; a High-Speed Totalizing Module (HSTM)  414 ; and a Software Control Module (SCM)  406 , including a micro controller, volatile and non-volatile memory containing software programmed with the test head testing sequence and communication algorithms. 
   The media is regulated via the EVPR  404 . EVPR  404  has a level set point that is determined by the software control module (SCM)  406 . Flow through the system is controlled via the SCV  410 . Flowing media is directed through the MFM  402 . The flow rate signal is generated and sent to the HSVFM  416 . The HSVFM  416  processes the flow meter signal every 50 milliseconds. The frequency signal is sent to the HSTM  414 , which is capable of sampling at 10 KHz. Information from the HSTM, and all control Input and Output, is sent via wireless Ethernet to the TMC  440 . 
     FIGS. 5–7  are flow charts illustrating an example test head testing sequence according to the present invention.
         1. The Start Test signal is generated via pushbutton or a User Input (UI). S 502     2. Upon discovery of the connection, the TMC will send the appropriate Recipe data to the respective Test Head Memory Space. S 504     3. The EVPR set point is set to a minimum value to prevent overloading of the MFM. S 524     4. The HSTM is reset to zero (0). S 506     5. The HSTM is set to begin Totalizing media. S 506     6. The SCV is turned on enabling media flow. S 508     7. The EVPR set point is ramped up to the Testing Level at a ramp rate that prevents overloading of the MFM. S 510     8. While Totalizing, compare the live Totalizing data to the Recipe Data [Max Value] and either continue or end the Test if it is exceeded (report a Failure). S 512 , S 514 , S 516 , and S 518     9. Wait for the stabilization of the Totalizing signal, indicating the cavity has stabilized. S 602 , S 604     10. Compare the Totalized value to the Recipe Data [Min Value] and end the Test if it is less than the Min Value. S 606 , S 608 , and S 610     11. If the Totalizer value is not less than the threshold, Store the Total Volume Evacuated in the respective mode result. S 612     12. Record the results. S 614     13. If passed, check for untested modes S 702 , S 706  if not passed, end test S 704     14. If more modes are necessary go to step 4. S 708     15. Send Test results to outside applications or local annunciation devices and end process. S 710 , S 712         
   Turning now to  FIG. 8 ,  FIG. 8  depicts an exemplary embodiment of a test head according to the present invention. Coupler  840  is connected to mass flow meter  804  and thence to solenoid  806 . Fluid is transferred from solenoid  806  to electronic vacuum regulator  808 . As shown in  FIG. 8 , the exemplary test head further includes vacuum pump  812 . The test head depicted in  FIG. 8  further includes antenna  802  and Ethernet modem  810  as well as Ethernet TCP/IP field bus coupler  816  which are used for communications. The exemplary embodiment of the test head further includes high speed counter module  818 , two channel analog input module  820 , two channel analog output module  822 , four channel digital output module  826 , and frequency output transmitter  828 . 
   Turning now to  FIG. 9 ,  FIG. 9  depicts an exemplary embodiment of a test head as depicted in  FIG. 8 , but showing greater detail.  FIG. 9  depicts the following components on the test head: double remote pilot solenoid valve  902 , single solenoids  904  and  906 , electrical connectors  912  and  910 , and telpneumatic pressure switch  908 . 
   Referring now to  FIGS. 10–17 ,  FIGS. 10–17  depict another exemplary process flow according to the present invention. Throughout  FIGS. 10–17 , process states are associated with reference numbers corresponding to exemplary computer program code disclosed in the appendix to the present application. 
   Referring now to  FIG. 10 , the exemplary process flow begins at state  1002  and proceeds to state  1004  where a determination is made as to whether a test head exists that is capable of executing the exemplary process flow. If a test head does not exist, process flow proceeds to state  1006  where the machine state is set equal to zero, indicating a system malfunction. If a test head does exist, then process flow proceeds to state  1008  where the machine state is set to 1, corresponding to the “reset” state (resetting the test head). A corresponding message is output in state  1010 . In state  1014 , a determination is made as to whether the “reset” state has been cleared, and the process state remains in state  1014  until the “reset” state has been cleared via return path  1012 . When the “reset” state has been cleared, processing proceeds to state  1016 , corresponding to a “head reset” state, and then to state  1018 , where the machine state is set to 11 and the minimum vacuum measurement is made. Processing then proceeds to state  1020  where a determination is made if the test should be aborted or if the test has failed because a minimum vacuum value has not been reached. If the test fails, processing proceeds via control path  1024  to state  1050  where a further determination is made if the test has been aborted or if the test has failed. If the test has been aborted, processing proceeds to state  1032  where the parameter “test head fault” is set equal to 500. 
   Referring now to  FIG. 11 , if the test has not aborted or failed, processing proceeds from state  1020  via control path  1022  and  1102  to state  1106  in which a time out timer is started. Processing proceeds to state  1108  which is the “minimum vacuum time out” state. Processing proceeds via control path  1110  if an initialization fault for the minimum vacuum is detected, and in state  1112 , the parameter test head fault is set to the value 601. Processing will remain in state  1116  until a minimum vacuum value is attained. When a minimum vacuum value has been attained, processing proceeds to state  1120  and then to state  1120  where the time out timer started in state  1106  is stopped. Processing proceeds to state  1124  in which the machine state is set to “100,” indicating that the test head is ready for test. Processing proceeds to state  1126  where a determination is made if an entering product is available. If a determination is made that a entering product is not available, processing proceeds via control path  1140  to state  1130  in which a disconnect is forced. If an entering product is available, processing proceeds to state  1128  in which the disconnect function is disabled. Processing proceeds to state  1132  where a determination is made if the test should continue. 
   Referring now to  FIG. 12 , if the test is to continue, processing proceeds via states  1136  and  1202  to state  1204  in which the machine state is set to 105, indicating that a connection has been made. In state  1208 , a determination is made as to whether any other entity is presently using the connection, and processing remains in state  1208  until no other entity is using the connection. Processing then proceeds to state  1210 , which is the “connecting” state. Processing proceeds to state  1214  where a determination is made if the connection is complete, and processing remains in this state until a complete connection is made. When a connection has been completed, processing proceeds to state  1216  where the machine state is set to 110, corresponding to the “initializing test” state. 
   Processing proceeds to state  1120  where a determination is made as to whether a test signal is being properly received, and processing proceeds to state  1226  if the test signal has been lost. In state  1228 , a determination is made as to whether any test modes remain that require further processing. If no test modes remain that require further processing, processing proceeds via control path  1230  to state  1232 , corresponding to the “test finished” state. If test modes remain, processing proceeds to state  1234  where the active mode is incremented. In state  1236  the present active mode is converted into a string, and processing proceeds to state  1238  where the machine state is set to the value of 120 plus the value of the testing mode. 
   Turning now to  FIG. 13 , processing proceeds via control path  1302  to state  1304  where a time out timer is started. If a totalizer time out occurs in state  1306 , processing via control path  1308  to state  1312  in which the test head fault parameter is set to the value of 602, indicating that the totalizer time out counter has failed to reset. Processing proceeds from state  1306  to state  1316  where a determination is made if the totalizer has been cleared, and processing remains in state  1316  until the totalizer has cleared. When the totalizer has cleared, processing proceeds to state  1318  and then to state  1320  in which the time out timer is stopped. Processing proceeds to state  1322  in which the mode change is reset. Processing proceeds to state  1324  in which the vacuum valve is activated, and then to state  1326  in which the message “waiting for flow” is generated. 
   Referring now to  FIG. 14 , processing proceeds to state  1406  and remains in state  1406  until fluid flow is detected. When fluid flow is detected, processing proceeds to state  1408  where a cycle timer is started, and then proceeds to state  1410 . From dwell state  1410  processing proceeds to state  1414  in which a determination is made as to whether the vacuum register set point is less than the recipe set point. If the vacuum register set point is determined to be less than the recipe set point, processing proceeds via control path  1416  to state  1418  in which the vacuum register set point is incremented, and control passes via control path  1420  and  1412  to state  1414 . If it is determined in state  1414  that the vacuum register set point is not less than the recipe set point, then control passes to state  1422  in which a time out timer is started. In state  1424 , if it is determined that the time out timer does not function, control passes to state  1436  in which the “test head fault” parameter is set to 603 indicating a “vacuum failure time out” fault. Control passes from state  1424  to state  1428  if the time out timer is successfully started, and remains in state  1428  until it has been determined that the vacuum is at the set point. When the vacuum reaches the set point, processing proceeds to state  1430  and to state  1438  where the time out timer is stopped. Processing proceeds to state  1440  in which the set up flow stabilization timer is started. 
   Turning now to  FIG. 15 , processing proceeds to state  1506  in which test head registers are updated. Processing proceeds to state  1508  in which a determination is made as to whether the test measurement has exceeded the high pass value. If the test measurement has exceeded the high pass value, processing proceeds via control path  1510  to state  1518  corresponding to a test head fault state “exceeded high pass fault.” Processing proceeds from state  1518  to state  1528  which is the “stop mode” state. If it is determined in state  1508  that the test measurement has not exceeded the high pass value, processing proceeds to state  1512  in which a determination is made if the test measurement has stabilized. If it is determined that the test measurement has not stabilized, control passes via control path  1514  to state  1516  in which the early done timer is stopped and cleared. Processing proceeds from state  1516  to state  1524  in which the current measurement value is stored as the old measurement value, and processing proceeds via control path  1526  and  1504  to state  1506 . If in state  1512  it is determined that the test measurement value has stabilized, processing proceeds to state  1520  where a determination is made as to whether the stabilized time duration period has been completed. If the stabilized time duration period has not been completed, processing proceeds via control path  1520  to state  1524 . If in state  1520  it is determined that the stabilized time duration period has been completed, processing proceeds to state  1528  corresponding to the “stop mode” state. Processing proceeds to state  1530  in which a determination is made as to whether the test measurement is less than the low pass value. If it is determined in state  1530  that the test measurement does not exceed the low pass value, processing proceeds to state  1534  corresponding to the test head fault “blocked low pass fault” state. Processing proceeds from state  1534  to state  1536 . If it is determined in state  1530  that the test measurement exceeds or equals the low pass value, processing proceeds to state  1536  in which the mode total for the test measurement is stored. Control then passes via control path  1538  and  1218  to state  1228 . 
   Referring now to  FIG. 16 , processing proceeds via fail control path  1602  to state  1612  in which the “failed” light is set, and processing proceeds to state  1616 . Processing proceeds via control path  1604  to state  1606  and then to state  1608 . In processing state  1610 , the “past” result code and light are set. Processing proceeds to state  1616  and then to state  1618  and state  1620 . In state  1620 , the test vacuum is turned off. Processing proceeds to state  1622  in which the “collar disconnect” signal is turned on. Processing proceeds to state  1624  in which a determination is made if a test cycle is in progress. If it is determined that a test cycle is not in progress, processing proceeds to state  1626  in which the vacuum system is shut down. 
   Referring now to  FIG. 17 , if it is determined in state  1624  that a test cycle is in progress, processing proceeds via control path  1712  to state  1714 . If it is determined in state  1624  that a test cycle is not in progress, processing proceeds via state  1626  and control path  1704  to state  1700 . In state  1700 , a determination is made if a reset is active and processing remains in state  1700  until a reset becomes active. When it is determined that a reset is active, control passes to state  1708 , corresponding to the “soft reset” state and processing proceeds to state  1712 . Processing remains in state  1712  until a determination is made that the reset is inactive. Processing then proceeds via control path  1732  and  1000  to state  1004 . 
   Processing remains in state  1714  until it is determined that the “start” signal has been lost. Processing then proceeds to state  1718 . Processing remains in state  1718  until it is determined that no other test head is reporting results. Processing then proceeds to state  1722  in which the new result is set, and processing proceeds to state  1726 . Processing remains in state  1726  until it is determined that the result is complete. Processing then proceeds to state  1728  in which the “collar disconnect” signal is turned off. Processing then proceeds to state  1730  in which the “in-cycle” signal is turned off. Processing then proceeds via control path  1732  and control path  1000  to state  1004 . 
   The present invention thus also includes a computer-based product which may be hosted on a storage medium and include instructions which can be used to program a general purpose microprocessor or computer to perform processes in accordance with the present invention. This storage medium can include, but is not limited to, any type of disk including floppy disks, optical disks, CD-ROMs, magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, flash memory, magnetic or optical cards, or any type of media suitable for storing electronic instructions. 
   Numerous additional modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise then as specifically described herein.