Patent Document

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a system for cycle testing, and more particularly to a failure sensing and control system for cycle testing. 
     2. Description of the Related Art 
     Cycle testing is a quality control process. It ensures that the functionality and durability of manufactured products meet certain industry standards. For example, a cycle test can be used to test a particular door of a car to determine whether the door can be opened and closed for at least 50,000 times without failure. Some parts can fail during a cycle test. Conventional cycle test systems do not have any built-in mechanism to detect failure and terminate the cycle test. Because a cycle test is not timely terminated, the failing part will be overstressed and broken. Hence, the failed part cannot be adequately analyzed as to the cause of failure. 
     There is a need for a sensing and control system that can monitor and terminate the cycle test when a part is starting to fail. 
     SUMMARY OF THE INVENTION 
     A sensing and control system that monitors and automatically terminates a cycle test when the part being tested is about to fail. The sensing and control system is implemented to be highly portable and flexible, making it convenient to use in conjunction with a variety of cycle test stations. A simple and user-friendly interface allows operation with minimum human intervention. The sensing and control system uses a sensor and a controller. The sensor generates a signal every time the part being cycle tested completes a motion cycle. The controller utilizes the signal to determine the duration of the motion cycle. If the sensed duration of the motion cycle exceeds the predefined cycle duration by a tolerance margin, this is taken as an indication that the part being cycle tested is about to fail. In response, the controller stops the cycle test before the part being tested is damaged. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The exact nature of this invention, as well as the objects and advantages thereof, will become readily apparent from consideration of the following specification in conjunction with the accompanying drawings in which like reference numerals designate like parts throughout the figures thereof and wherein: 
         FIG. 1  is a block diagram illustrating a sensing and control system according to an embodiment of the present invention; 
         FIG. 2  is a block diagram of a controller according to an embodiment of the present invention; 
         FIG. 3  is a schematic of a sensing and control system according to an embodiment of the present invention; 
         FIG. 4  is a waveform diagram of signals in the sensing and control system of  FIG. 3  according to an embodiment of the present invention; 
         FIG. 5  is a waveform diagram of signals in the sensing and control system of  FIG. 3  according to an embodiment of the present invention; and 
         FIG. 6  is a flow chart of a method practiced by an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a cycle test setup  100 , having a sensing and control system  110  connected to a power supply  120 , a cycle test station  130 , and a processor  150  connected to the sensing and control system  110 . The cycle test station  130  is typically used for testing the functionality and durability of a part  140  by continuously moving the part  140  back and forth. For example, the part  140  may be a door of an automobile, wherein the hinges of the door are being tested by moving the part  140  back and forth for a predetermined number of cycles. 
     The cycle test station  130  moves a part  140  from a first position  142  to a second position  144  and from the second position  144  back to the first position  142 . If the part  140  is a door, the first position  142  could be a closed position. The second position  144  could be an open position. The part  140  being cycle tested completes one motion cycle  146  each time it moves from the first position  142  (closed door) to the second position  144  (open door), passing by a sensing position, which may be located anywhere between the first position  142  and the second position  144 . 
     The sensing and control system  110  includes a controller  111  and a sensor  112 . The sensor  112  senses movement of the part  140  and generates a sensing signal each time the part  140  moves past the sensor  112 . Each sensing signal indicates that the part  140  has completed one motion cycle. The sensor  112  receives power from a power supply  120  through the controller  111 . The sensor  112  may be any sensor capable of sensing motion of a moving part  140 . For example, the sensor  112  may be a motion sensor, an optical sensor, a proximity sensor, a pressure sensor, or a contact sensor. In order to fine tune the sensing process, multiple sensors  112  may be used for sensing increments of a motion cycle  146 . For example, the sensing and control system  110  may include first and second sensors. The first sensor would be placed to sense a first half of the motion cycle  146 . The second sensor would be placed to sense a second half of the motion cycle  146 . 
     The controller  111  receives power from the power supply  120  by a first power cable  122 . The controller  111  provides power to the cycle test station  130  by a second power cable  132 . The sensor  112  provides its sensing signals in real time to the controller  111  by a connection  113 . The connection  113  may be a hard wire or wireless connection. 
     The controller  111  analyzes each sensing signal received from the sensor  112 . Depending on the objective of the cycle test, a test failure may be declared when the part  140  fails to complete one motion cycle  146  within a predetermined time period. Or, a test failure may be declared when the part  140  takes longer than a predetermined duration to complete one motion cycle  146 , or a plurality of motion cycles  146 . The absence of a sensing signal during a motion cycle may signify that the part  146  has stopped moving or is stuck at a particular position and thus unable to complete the motion cycle  146 . The controller  111  generally determines a test failure has occurred when it does not receive a sensing signal within a predetermined time period after the previous sensing signal. 
     The predetermined time period may be based on an average duration of a typical motion cycle for a particular part  140 . A tolerance margin to accommodate inter-cycle variation may be added. For example, the average duration of a typical motion cycle may be about 30 seconds with an inter-cycle variation of about 5 seconds. The predetermined time period may be set to about 35 seconds. The controller  111  will determine a test failure a sensing signal is not received within 35 seconds after the last received sensing signal. 
     Upon determining a test failure, the controller  111  will stop the cycle test by cutting the power being supplied to the cycle test station  130 . Alternatively, the controller  111  may generate a termination signal. The cycle test station  130  will stop moving the part  140  upon receiving the termination signal. 
     The controller  111  preferably has several user interfaces, including a control dial  116 , a motion cycle duration display screen  114 , a motion cycle counter display screen  118 , and a set of cycle test indicators  115 . The control dial  116  allows a user to start, stop, preset and reset the controller  111 . The motion cycle duration display screen  114  displays the time elapsed during one motion cycle. The motion cycle counter display screen  118  displays the number of sensing signals generated, which is representative of the number of motion cycles  146  the part  140  has completed. The set of cycle test indicators  115  can be a plurality of light emitting diodes (LEDs). Particularly, each of the indicators  115  is used for indicating one of the events related to the cycle test. The events may include cycle test preset, cycle test reset, cycle test in progress, and test failure detected. 
     During a cycle test, the controller  111  sends test results to a processor  150  by a communication link  152 . The controller  111  may notify the processor  150  once a test failure occurs. The processor  150  will respond accordingly. Depending on the system architecture, the communication link  152  may be hardwired or wireless. The processor  150  may be any computing device capable of receiving data, processing the received data, and storing and outputting the processed data. The processor  150  typically has a display  154  and a memory  160 . The processor  150  may be coupled to a printer  170 . 
     The test results sent to the processor  150  may include a pass indicator, indicating that the part  140  has completed the cycle test, or a fail indicator, indicating that the part  140  has failed the cycle test. Besides a pass/fail indicator, the test results may include the total number of motion cycles the part  140  has completed and the average duration of the completed motion cycles. The processor  150  is enabled to process and analyze the test results and generate a printed test report  172 , documenting the analyzed test result. Moreover, the processor  150  can store the current test result to the memory  160  and/or retrieve past test results from the memory  160 . Accordingly, the processor  150  can perform statistical analysis for a particular type of part. 
       FIG. 2  shows the controller  111 . The controller  111  includes a timer  310  and a power switch  320  connected to and controlled by the timer  310 . The power switch  320  controls the connection between the power supply  120  and the cycle test station  130 . 
     During test setup, a user may input a predefined cycle duration value to the timer  310  via line  312  by using the control dial  116 . The predefined cycle duration value may be obtained by averaging the duration of several motion cycles of the part  140  to be tested. The predefined cycle duration value preferably incorporates a tolerance margin for inter-motion-cycle variation. For example, the tolerance margin may range from about 0.1 second to about 10 seconds. Or, the tolerance margin may range from about 0.5 second to about 5 seconds. Or, the tolerance margin may be about 3 seconds. 
     After the timer  310  is preset with a predefined cycle duration value, the cycle test may begin. The timer  310  is configured to respond to the sensing signals on line  217  from the sensor  112 . The timer  310  includes a counter or an accumulator, which will count to determine the duration of a sensed motion cycle. The timer  310  will reset each time it receives a sensing signal. After being reset by the sensing signal  214 , the timer  310  will begin counting the duration of the sensed motion cycle. 
     The timer  310  compares the predefined motion cycle duration value with the duration of each sensed motion cycle being sensed. If the part  140  does not complete a motion cycle during the predefined duration, the sensing signal will not be generated, and the timer  310  will not be reset within the predefined motion cycle duration. Consequently, the duration of the sensed motion cycle will be greater than the predefined motion cycle duration value. When the duration of the sensed motion cycle exceeds the predefined motion cycle duration value by the tolerance margin, a test failure is indicated. In response, the timer  310  then generates a termination signal sent via the line  314  to the power switch  320 . 
     The power switch  320  receives input power over the cable  122  and delivers the power over the cable  132  to the cycle test station  130 . Delivery of power to the cycle test station  130  is controlled by the termination signal  314  from the timer  310 . The cycle test station  130  stops cycling the part  140  when the power switch  320  terminates power to the cycle test station  130 . 
       FIG. 3  is a schematic of preferred circuitry  400  for the sensing and control system  110 . The preferred circuitry  400  includes a power regulator  420 , configured to convert AC power received from the power supply  120  to an internal DC voltage. For example, the power regulator  420  may deliver a 12 V internal DC voltage. The positive potential of the internal DC voltage is carried by the positive supply node  422 , which delivers the DC voltage to a sensor  460  and a timer  440 . 
     The sensor  460  may be a motion sensor, an optical sensor, a proximity sensor, a pressure sensor, or a contact sensor. Preferably, the sensor  460  is a mini-beam sensor. The sensor  460  generates a sensing signal each time it senses a part completing a motion cycle. The sensing signal is carried by the sense node  462  to an amplifying stage  470 . The amplifying stage  470  will generate a reset signal in response to receiving a sensing signal. The reset signal is delivered to the timer  440  by a reset node  476 . The amplifying stage  470  may be implemented by a variety of circuits. For example, the amplifying stage  470  may include a transistor  473  for amplifying the sensing signal, a bias resistor  471  for biasing the input voltage of the transistor  475 , a high pass capacitor  472  and a resistor  473  for filtering low frequency input voltage, and a pull up resistor  474  for biasing the output of the transistor  475 . 
     Upon receiving a reset signal, the timer  440  will be reset so that the sensed motion cycle has zero duration. After being reset, the timer  440  will again begin counting the duration of the sensed motion cycle, until the timer  440  receives the next reset signal. In between successive reset signals, the timer  440  compares the duration of the sensed motion cycle with the predetermined motion cycle value. When the duration of the sensed motion cycle exceeds the predetermined motion cycle value by a tolerance margin, the timer  440  will indicate a test failure by toggling a termination signal at an output node  444 . The termination signal has a low voltage value before a test failure is indicated. The termination signal has a high voltage after a test failure is indicated. 
     A relay device  430  is preferably used as the power switch  320  ( FIG. 3 ). The relay device  430  will be turned on when the voltage of the termination signal is substantially lower than the internal DC voltage of the sensing and control system  400 . The relay device  430  will be turned off when the termination signal has a voltage that substantially equals the internal DC voltage. 
     When the relay device  430  is turned on, it closes a switch between the cycle test station  130  and the power supply  120 . However, when the relay device  430  is turned off, it opens the switch between the cycle test station  130  and the power supply  120 . Depending on the design needs, the relay device  430  may be a solid state relay, a solid state contactor relay, a reed relay, a polarized relay, a contactor relay, or a dry contact switch relay. 
     The preferred circuitry  400  includes a set of switches. A power switch  412  is coupled between the power source  120  and the power regulator  420 , and it is used for turning the sensing and control system  400  on and off. A pair of bypass switches  414  and  415  is used for bypassing the termination signal, such that the relay device  430  can stay powered on during the initial setup process. A pause switch  416  is selectively connected to a run node  441  or a stop node  442  of the timer  440 . The pause switch  416  is used for pausing and resuming the timer  440 . A reset switch  418  is coupled to the reset node  476  for manually resetting the timer  440 . The control dial  116  ( FIG. 1 ) is used for toggling the set of switches. Alternatively, each of the switches may be accessed and controlled individually. 
     The sensing and control system  400  may include a counter  480  and a set of LED indicators. The counter  480  is coupled to a reset node  476 . The counter  480  counts the number of reset signals being generated. The counter  480  can be used for counting the number of motion cycles completed by the part under test. A power indicator LED  451  indicates that the sensing and control system  400  is turned on. A bypass indicator LED  452  indicates that the sensing and control system  400  is in setup. An output power indicator LED  454  indicates that the relay device  430  is delivering power from the power source  120  to the cycle test station  130 . A motion cycle pending indicator LED  456  indicates that the part  140  under test is in the middle of a motion cycle. A motion cycle completion indicator LED  458  indicates that the part  140  under test has just completed one motion cycle. 
     As shown in  FIG. 4 , the sensing and control system  400  generates a sensing signal  510 , a sensed motion cycle duration signal  520 , and a termination signal  530  during the cycle test. The sensing signal  510  is preferably a pulse signal  514 , which is generated shortly after the sensor senses the part under test completing one motion cycle. The duration between successive pulse signals  514  in a normal test cycle is used for calculating the predetermined motion cycle duration  512 . 
     The sensed motion cycle duration signal  520  is reset at the rising edge of each pulse signal  514 . The sensed motion cycle duration signal  520  is the time elapsed value since reception of the last pulse signal  514 . When the sensed motion cycle duration signal  520  has a value that is less than the predefined motion cycle duration value  512 , the termination signal  530  will not be toggled. The cycle test continues, and the sensed motion cycle duration signal  520  is reset when the part under test completes the first  541 , second  542 , third  543 , fourth  544 , and fifth  545  motion cycles, each of which may take about 9 seconds. 
     When the part is stuck, for example, and thus fails to finish the sixth motion cycle, no pulse signal  514  will be generated. As a result, the sensed motion cycle duration signal  520  will not be reset for at least an extended period  518 . Thus, the value of the sensed motion cycle duration signal  520  reaches a maximum threshold level  528 , which signifies that the sensed motion cycle has exceeded the predefined motion cycle duration  512  by a tolerance margin  529 . At that point, a test failure  546  is indicated, and a termination signal  534  is toggled from a low state  532  to a high state  534 . In response, the power transmission to the cycle test station is terminated by the relay device. 
       FIG. 5  illustrates another scenario for toggling the termination signal  530 . The part under test may be stuck at the sensing position right after the completion of the fourth motion cycle  544 . The pulse signal  516  will stay high and the next pulse signal will not be generated for at least an extended period  518 . The sensed motion cycle duration signal  520  will not be reset again for at least the extended period  518 . As a result, the sensed motion cycle duration signal  520  will reach the maximum threshold level  528 . Indication of a test failure  546  will then follow, toggling the termination signal  530 . 
       FIG. 6  is a flow chart of a method  700  practiced by a preferred embodiment of the present invention. In step  702 , a part is cycle tested by a cycle test station. In step  704 , a pulse signal is generated each time the part under test completes a motion cycle. In step  706 , the duration of each motion cycle is determined based on the pulse signal generated. The duration of the motion cycle is reset at the rising edge of each pulse signal, and it is increased according to the time elapsed since the last pulse signal. 
     In step  708 , a test failure is detected if the duration of the sensed motion cycle duration signal  520  exceeds a predetermined motion cycle duration by a tolerance margin. That is, due to the absence of the pulse signal, the motion cycle duration is not reset for an extended period of time. When the extended period of time is greater than the sum of the predefined motion cycle duration and the tolerance margin, a test failure is determined. The predefined cycle duration is calculated by averaging the duration of several motion cycles. In step  710 , power transmission to the cycle test station is terminated upon a test failure being determined. 
     Obviously many 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 invention may be practiced otherwise than as specifically described.

Technology Category: 3