Automated in situ testing of railroad telemetry radios

Railroad telemetry radios are tested by an automated method for in situ testing, so that only those units requiring adjustment and maintenance are removed. A multi-function test set is programmed to automate testing of the radios used in a telemetry system in conjunction with other test software embedded in the host telemetry devices. The radios contain both a transmitter and a receiver. Both are individually tested to verify proper performance. Receiver sensitivity testing of the radio is tested by bit error rate (BER) measurement with test software and a dedicated BER modulator. A known low amplitude message comprised of a short pseudorandom pattern continuously repeated by the test set BER modulator is demodulated by the radio receiver. The test software processes the received data and counts the number of errorless messages received over a specific period of time. The receiver sensitivity is known to be acceptable if the number of correct messages received is higher than a predetermined minimum value. The transmitter performance is tested by measuring radio frequency (RF) carrier frequency, modulation frequency, deviation and RF output power. The test set is programmed to automatically measure these parameters, determine whether they meet minimum requirements, prompt the technician as to pass/fail status, and optionally display measured test data for use in radio repair, if required, or for statistical purposes.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention generally relates to testing of railroad telemetry
 radios used in intra-train communications and, more particularly, to an
 automated on-locomotive testing of Locomotive Control Unit (LCU) radios
 and End of Train (EOT) radios. The LCU and the EOT are complementary
 devices which communicate with each other as part of a complete
 information and control system required by the Federal Railroad
 Administration (FRA) to be used on freight trains with few exceptions.
 2. Background Description
 End of Train (EOT) signaling and monitoring equipment, now widely used in
 place of cabooses, and a Locomotive Control Unit (LCU) installed in the
 locomotive are used as part of an intra-train digital telemetry
 communications system. The EOT is typically mounted on the last car of the
 train and monitors brake pipe air pressure, train movement, battery
 condition, etc., and transmits this information as digital data over the
 radio frequency (RF) telemetry link to the LCU. The information monitored
 by the EOT and transmitted to the LCU is displayed to the crew in the
 locomotive. The EOT also receives RF transmissions from the LCU to control
 an air valve in the train's brake pipe to initiate emergency, and in some
 cases, service braking.
 Since the proper operation of EOTs and LCUs in intra-train communications
 is critical, the systems are tested before each use by the railroads.
 Thus, after a train has been "made-up" in the rail yard and the LCU and
 EOT installed, a functional test is performed to verify the overall
 operation of both devices. This is done as part of the normal linking and
 arming sequence and verifies the functional operability of the system,
 i.e., LCU and EOT as a linked pair.
 Note that this test does not check the performance limits of the LCU and
 EOT radios. To check radio performance, the LCU and EOT must normally be
 brought to a radio shop where the proper equipment is available, and
 requires opening the LCU and EOT enclosures to gain access to the radios.
 However, as described and explained herein, the subject invention permits
 full radio performance testing to be performed at a convenient regular
 interval, in situ, such as when locomotives are "shopped".
 SUMMARY OF THE INVENTION
 It is therefore an object of the present invention to provide an in situ
 test of railroad telemetry radios;
 It is another object of the invention to provide an on-locomotive test
 capability for the LCU radio installed on the locomotive.
 It is a further object of the invention to provide an in situ test
 capability for the EOT radio separate from a central radio shop.
 According to the invention, there is provided a multi-function test set to
 automate testing of the LCU without the need to remove the LCU or to open
 its cover. The radio module inside of the LCU contains both a transmitter
 and a receiver. Both are individually tested to verify proper performance.
 Receiver sensitivity testing of the LCU radio is tested by a bit error
 rate (BER) measurement with LCU test software and a dedicated BER
 modulator modulating the test set. The BER modulator and test set generate
 a known low amplitude message comprised of a short, continuously repeated
 pseudorandom pattern which is demodulated by the radio receiver. The test
 software processes the received data and counts the number of errorless
 messages received over a specific period of time. The receiver sensitivity
 is known to be acceptable if the number of correct messages received is
 higher than a predetermined minimum value. The transmitter performance is
 tested by measuring radio frequency (RF) carrier frequency, modulation
 frequency, deviation and RF output power. The test set is programmed to
 automatically measure these parameters, determine whether they meet
 minimum requirements, and prompt the technician as to pass/fail status.
 The automated test set and procedure of this invention have significant
 advantages. Only those LCUs requiring adjustment and maintenance are
 removed, resulting in less downtime for locomotives. The procedures used
 for testing LCU radios are easily adapted to in situ testing of EOT radios
 in those situations where railroads use a central radio shop for repair
 and calibration, and EOTs would otherwise have to be sent to this central
 location for radio testing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
 As currently deployed on many railroads, there are two basic types of LCUs
 installed on locomotives. Both have a local microprocessor for performing
 the required functions of the LCU. However, one type has a built-in user
 interface (control switches and displays) which can be used in conjunction
 with the test software to directly carry out radio testing. The test
 methodology and test procedures for this type of LCU will be described
 first. The other type of LCU has no user interface since it normally
 interfaces to a locomotive computer through a communications port. By
 accessing this communications port with a personal computer (PC) (through
 an input/output (I/O) box), the radio testing can be controlled by
 software installed on the PC. The test methodology and test procedures for
 this second type will be described second.
 Referring now to the drawings, and more particularly to FIG. 1, there is
 shown a multi-function test set 10 which is programmed to automate
 testing. A suitable test set is the Hewlett-Packard HP8920A RF
 communications test set. A BER modulator 11 is connected to the modulation
 input of the test set by cable 12. The antenna is disconnected from the
 LCU 13, and a calibrated attenuator and connecting cable 14 is connected
 between the antenna connector of the LCU and the RF input/output of the
 test set.
 The receiver BER test is performed first. The operator sets a predetermined
 identification (ID) code in the LCU using thumb wheels (not shown) and
 presses a key on the test set to select the test function. Then the
 operator enters the calibrated attenuator test cable 14 insertion loss
 using data keys on the test set panel. When the test set 10 displays the
 message "READY FOR RECEIVER BER TEST", the test is started by the operator
 simultaneously pressing and holding the "COMMUNICATIONS TEST/ARM" and
 "LOCOMOTIVE DISTANCE COUNTER" buttons on the LCU panel. During the test, a
 known low amplitude message comprised of a short pseudorandom pattern
 generated by the BER modulator 11 and transmitted via the test set 10, the
 calibrated attenuator and connecting cable 14 to the LCU 13 is demodulated
 by the radio receiver. Special software in the LCU 13 processes the
 received data and counts the number of errorless messages received over a
 specific time period. The receiver sensitivity is known to be acceptable
 if the number of correct messages received is higher than a predetermined
 minimum value. At the end of the BER test, the LCU 13 will display either
 "BER PASS" or "BER FAIL". If the LCU fails the BER test, the LCU is
 removed from service for maintenance and repair.
 To conduct the tests on the transmitter module of the LCU 13, the BER
 modulator 11 is first turned off. The "COMMUNICATIONS TEST/ARM" button on
 the LCU panel is pressed to begin a transmission from the LCU transmitter
 module to the test set 10. This transmission from the LCU 13 is at a first
 predetermined power level and at a predetermined frequency. To measure
 this signal, a designated key on the test set 10 is pressed. The test set
 10 then measures the RF power, transmit frequency, deviation and
 modulation frequency of the signal, these measurements being compensated
 for the attenuator and connecting cable 14 insertion loss. The measured
 parameter values are stored, and the measured parameter values are then
 compared to previously set parameter limits. The test set 10 then displays
 either "TRANSMITTER TEST PASSED" or "TRANSMITTER TEST FAILED". If the test
 failed as a result of any of the measured parameter values not being
 within the limits, the LCU is removed from service.
 Note that after a radio is tested, whether it fails or passes, a display
 and, optionally if the test set is so equipped, a printout of the test
 results can be obtained by pressing a key on the test set. Thus, if the
 radio failed, these test results can help the radio shop to identify the
 failure area and speed the repair process. Further, even if the radio
 passed, access to the test results data will also be useful for collecting
 radio performance statistics.
 However, if the test passed, the user will see the "RADIOTST" message
 displayed in the display window of the LCU as a prompt. The user then
 presses the "COMMUNICATIONS TEST/ARM" button again to begin a second
 transmission from the LCU 13 to the test set 10, this time at a lower
 predetermined power level and a predetermined frequency. After the
 designated key on the test set 10 is again pressed, the test set again
 measures the RF power, transmit frequency, deviation and modulation
 frequency of the signal, these measurements being compensated for the
 attenuator and calibrated test cable 14 insertion loss. The measured
 parameter values are stored, and the measured parameter values are then
 compared to previously set parameter limits. The test set 10 will display
 "ALL TESTS PASSED" or "TEST FAILED". Again, a display of the test results
 data can be obtained from the test set to either aid in repair of the LCU
 or for data collection and analysis.
 With reference now to FIG. 2, in the case of the second type of LCU 13',
 the multi-function test set 10, BER modulator 11, attenuator and
 calibrated test cable 14 are connected as before. In this case, a lap top
 personal computer (PC) 16 is connected to the computer input of the LCU
 via an input/output (I/O) box 17. The PC 16 may have the test programs
 stored on its hard disk or, alternatively, a floppy disk may be provided
 which contains the test programs.
 The receiver BER test is performed first as before, but the test is
 initiated by user input through the PC 16. For example, for a PC running
 under the Windows 95 operating system (OS), the operator uses the cursor
 control device (e.g., mouse, touch pad, track ball, etc.) to select and
 execute the test program. Then, in response to the program prompts, the
 operator then enters the calibrated attenuator and connecting cable 14
 insertion loss using data keys on the test set 10. When the test set
 displays the message "READY FOR RECEIVER BER TEST", the operator presses a
 designated key on the PC keyboard to begin the receiver BER test. During
 the test, a known low amplitude message comprised of a short pseudorandom
 pattern generated by the BER modulator and transmitted via the test set
 10, the calibrated attenuator and connecting cable 14 to the LCU 13' is
 demodulated by the radio receiver. The software in the PC 16 processes the
 received data and counts the number of errorless messages received over a
 specific time period. The receiver sensitivity is known to be acceptable
 if the number of correct messages received is higher than a predetermined
 minimum value. At the end of the BER test, the PC 16 will display either
 "BER PASS" or "BER FAIL". If the LCU fails the BER test, the LCU is
 removed from service for maintenance and repair.
 To conduct the tests on the transmitter module of the LCU, the BER
 modulator 11 is first turned off. The PC monitor displays "READY TO
 TRANSMIT" as a prompt to the operator, and in response to this prompt, the
 operator presses the designated key on the PC keyboard and the designated
 key on the test set. The transmission from the LCU 13' is at a first
 predetermined power level and at a predetermined frequency. The test set
 measures the RF power, transmit frequency, deviation and modulation
 frequency of the signal, these measurements being compensated for the
 attenuator cable insertion loss. The measured parameter values are stored,
 and the measured parameter values are compared to previously set parameter
 limits. The test set 10 then displays either "TRANSMITTER TEST PASSED" or
 "TRANSMITTER TEST FAILED". If the test failed as a result of any of the
 measured parameter values not being within the limits, the LCU is removed
 from service. However, if the test passed, the user waits for the "READY
 TO TRANSMIT" prompt message to be displayed on the PC screen and then
 again presses the designed key on the PC keyboard and the designated key
 of the test set to begin a second transmission from the LCU 13 to the test
 set 10, this time at a lower predetermined power level and a predetermined
 frequency. The test set 10 again measures the RF power, transmit
 frequency, deviation and modulation frequency of the signal, these
 measurements being compensated for the attenuator cable insertion loss.
 The measured parameter values are stored, and the measured parameter
 values are compared to previously set parameter limits. The test set 10
 will display "ALL TESTS PASSED" or "TEST FAILED". If the test failed, the
 LCU is taken out of service for maintenance or repair. Again, test results
 data can be obtained from the test set, as described previously.
 FIGS. 3A and 3B and FIGS. 4A and 4B are, respectively, flow diagrams
 illustrating the logic of the separate test programs for the RF test set
 and the LCU. These diagrams include a sequential list of required operator
 actions listed with arrows pointing to the specific location in each flow
 diagram to which the action is related. Note that the LCU radio test
 software routines may either be embedded in an LCU of the first type, as
 specifically shown in FIGS. 4A and 4B, or these routines may be
 implemented on the PC which is used in the testing of an LCU of the second
 type.
 In either case and with reference to FIG. 3A, with the LCU powered on, the
 radio test process begins in function block 301 on power-up of the test
 set with a prompt message displayed on the screen of the test set to press
 a designated key (k1) to start actual testing. In decision block 302, the
 test for the k1 key press is made which, when affirmative, leads to
 function block 303 prompting the operator to enter the test cable
 insertion loss. Then, decision block 304 tests for entry of the cable loss
 which, when affirmative, prints a "PLEASE WAIT" message to the screen in
 function block 305, while the test set in function block 306 configures
 itself to compensate for the entered insertion loss. When configured, the
 test set displays the "READY FOR RECEIVER BER TEST" in function block 307,
 and then waits in decision block 308 for the k1 key press. When k1 is
 pressed, the affirmative exit leads to the display of the next prompt in
 function block 309 "PERFORMING 8W TRANSMITTER TEST" during which the test
 set makes the measurements identified in function block 310 and stores the
 measured data in memory. In function block 311, the measured parameters
 are then compared to predetermined limits.
 Referring now to FIG. 3B, if all parameters are within their limits, as
 checked in decision block 312, the affirmative exit leads to function
 block 313, which displays the screen message "8W TRANSMITTER TEST PASSED".
 However, if any parameters are beyond their limits, the negative exit from
 decision block 312 leads to function block 320, which displays the message
 "TEST FAILED", and then to function block 321 which displays exit menu
 choices described below. The program flow then proceeds to decision block
 314, which requests a k1 key press which, when affirmative, prints a
 screen message "PERFORMING 2W TRANSMITTER TEST" in function block 315,
 during which the test set makes the measurements identified in function
 block 316 and stores the measured data in memory. In function block 317,
 the measured parameters are then compared to predetermined limits. if all
 parameters are within their limits, as checked in decision block 318, the
 affirmative exit leads to function block 319, which displays the screen
 message "ALL TESTS PASSED". However, if any parameters are beyond their
 limits, the negative exit from decision block 318 leads to function block
 320, which displays the screen massage "TEST FAILED". The program flow
 then proceeds to function block 321, which displays an exit selection menu
 prompting the operator for one of three key presses k1, k2 or k3. The
 three possible key presses are examined sequentially in decision blocks
 322, 323 and 324. A k1 key press provides the affirmative answer leading
 to restarting the entire test; a k2 key press exists the program; or a k3
 key press branches affirmatively to function block 325, which displays a
 prompt message again allowing a k1 or k2 key press to restart the test and
 also displays the measured parameters on the screen in function block 326.
 Continuing with reference now to FIG. 4A, the software flow for the radio
 test process resident within the LCU will now be described. The process
 starts from the normal mode of LCU operation with a test in decision block
 327 to determine if the "COUNTER" or "COM TEST" buttons have been pressed
 and held for a predetermined time interval. If not, the LCU remains in
 normal operating mode. However, if the test in decision block 327 is
 affirmative, the program flow proceeds to decision block 328, which tests
 that the correct identification (ID) code has been entered into the LCU ID
 code switches. If yes, the message "BER TEST" is displayed in function
 block 329 and the BER test is started in function block 330. The results
 of the BER test are examined in decision block 331 with a fail result
 sounding the beeper three times in function block 332 and displaying the
 screen message "BER FAIL" in function block 333. The time out decision
 block 334 holds the display illuminated until a predetermined time out
 period elapses, at which time the display is extinguished in function
 block 335 and the LCU test program ends. If, however, the BER test passes,
 then decision block 331 is exited affirmatively which sounds the beeper
 one time in function block 336 and displays the screen message "BER PASS"
 in function block 337. At this point, the operator turns off the BER
 modulator resulting in the pseudorandom RF signal at the LCU radio input
 being removed. Thus, decision block 338 is no longer satisfied, and
 program flow proceeds to function block 339, which displays "RADIOTST",
 and then waits for a "COM TEST" button press in decision block 340. When
 the "COM TEST" button is pressed, decision block 340 is exited
 affirmatively resulting in the display of the "TRANSMIT" screen message in
 function block 341.
 Referring now to FIG. 4B, a high power RF transmission is generated from
 the LCU radio in function block 342. This RF transmission continues until
 the timeout period set by decision block 343 is satisfied, resulting in
 the affirmative exit to function block 344 which terminates the high power
 RF transmission, and displays the "RADIOTST" screen message in function
 block 345. Next, the software flow idles at decision block 346 waiting for
 the operator to press the "COM TEST" button again. When this button is
 pressed, the affirmative exit results in the display of the "TRANSMIT"
 scree message in function block 347, and the generation of the low power
 RF transmission from the LCU radio in function block 348. This RF
 transmission continues until the time out period set by decision block 349
 is satisfied, resulting in the affirmative exit to function block 350,
 which terminates the low power RF transmission and displays the "RADIOTST"
 screen message in block 351. The "RADIOTST" screen message remains
 displayed for the duration of a time out period set by decision bloc 352.
 When this time elapses, the affirmative exit from decision block 352 leads
 to function block 353 which extinguishes the display, and the program
 ends.
 While the invention has been described in terms of preferred embodiments as
 particularly applied to LCU radios, those skilled in the art will
 recognize that the invention can be practiced with modification within the
 spirit and scope of the appended claims. The invention is not necessarily
 limited to testing LCU radios and, as has been noted herein, may be used
 to some advantage in field testing EOT radios where the convenience of a
 local in situ test is logistically advantageous.