Abstract:
Described is a system with a plurality of subsystems, wherein at least one of the plurality of subsystems comprises one or more monitoring points relevant and representative for certain parameters of the respective subsystem, each one of the one or more monitoring points is connected with a respective diagnosis module for substantially permanently monitoring the respective monitoring point, and an evaluation unit is connected with each respective diagnosis module for receiving information therefrom about each respective monitoring point, and for evaluating the received information in order to draw conclusions about parameters and properties within the system. The system is preferably used in an automated test equipment system.

Description:
BACKGROUND OF THE INVENTION 
     The present invention generally relates to the discovering of failures in complex systems for data processing purposes. 
     Discovering of failures in complex systems, i.e. systems with a plurality of subsystems, generally exhibits difficulties since there might be a plurality of difficult failures in the various subsystems, and the failures might also reveal in different forms. Failures which can obviously be seen, such as when a system is completely inoperable, can easily be detected by the user of the system. However, in case that internal parameters within the system or the subsystems change and thus influence the entire system, this might not be detected from outside, e.g., by the user. These failures might only turn out by their effects and can solely be detected by trained users, special instructed persons, or by sp cific inspection routines. 
     Some failures occurring in one subsystem only have an impact on the subsystem itself e.g. in a way that only the subsystem might become inoperable. However, other failures occurring in one subsystem might also influence other s bsystems and thus the entire system. 
     Examples for systems which are in particular sensitive for failures are automated test equipment (ATE) systems, such as IC testers, or sorting and packaging machines with optical recognition of products, or the like. Defects or failures in one subsystem can influence the entire ATE system in a way that the testing results can be erroneous and might not represent the actual state of a device under test (DUT). This can lead to a reduced yield of the DUTs to be tested and components which are well functioning might be selected as defective, and vice versa. 
     Failures in complex systems are usually detected in the art by specific diagnosis routines monitoring the functional ability (functionability) of the system. The diagnsis routines are normally started in defined service or maintenance intervals, or before use of the system. The execution of such a diagnosis routine is to be started by the user or might be automatically and periodically started by the system. The effective using time of the system is reduced by the time required for executing the diagnosis routines. In case the system is used for production or testing purposes, the time required for executing the diagnosis routines might increase the product costs of the devices to be produced or tested by the system. Furthermore, failures occurring during the operation of the system might not be recognized and can lead to a series of faulty products. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to improve the detection of failures occurring in complex systems. 
     According to the invention, a complex system is monitored substantially permanently at p edefined monitoring points by means of one or more diagnosis modules respectively within one or more subsystems of the system. The diagnosis modules provide their measuring results to an evaluation unit for evaluating define d parameters and properties of the subsystem and thus of the system. 
     The term ‘substantially permanently monitoring’ as used herein means that the monitoring is exe uted substantially in parallel to and independent of other running programs events, tasks, or the like within the system. However, the monitoring and evaluating according to the invention might also be run with a lower or higher priority that other running programs or tasks within the system in order to improve possible runtime constraints within the system. In case that the entire system or respective subsystems are operated in a standby mode, the monitoring is preferably carried on, whereas in case that the entire system or respective subsystems are switched of or in a disconnected mode, the monitoring within the entire system or the respective subsystems is preferably not maintained and also switched of or disconnected. For that reason, the monitoring is preferably driven by an own separate power supply. 
     A system according to the invention comprises a plurality of subsystems, whereby at least on of the plurality of subsystems comprises one or more monitoring points reevant and representative for certain parameters of the respective subsystem and each one of the one or more monitoring points is connected with a respective diagnosis module for substantially permanently monitoring the respe ve monitoring point An evaluation unit is connected with each respective diagnosis module for receiving information therefrom about each respective monitoring point and for evaluating the received information in order to draw back onto parameters and properties within the system. 
     A method according to the invention for discovering failures in the system according to the invention comprises steps of substantially permanently monitoring the respective monitoring point, receiving information from each respective diagnosis module about each respective monitoring point, and evaluating the received information in order to draw back onto parameters and properties within the system. 
     The invention is preferably used in an automated test equipment system. 
     The predefined monitoring points have to be selected as relevant and representative for the functionality of a respective subsystem and thus of the functionality of the entire system. The diagnosis modules are preferably coupled by a communication channel connecting the respective diagnosis modules with the evaluation unit. 
     The evaluation unit is preferably controlled by a software program which is executed substantially permanently and in parallel to other running programs or tasks within the system. 
     The invention allows to permanently monitor and observe parameters of the system without unduly influencing the usage of the system. In case of a failure occurring or when observed parameters of the system tend to drift, the user of the system can be informed by the evaluation unit during the normal operation of the system. 
     The invention further allows to postpone or suspend an intended inspection cycle of the system in case that no drifting of parameters or that no failures are observed by the evaluation unit. This leads to increased inspection intervals of the system and thus to an increased effective using time of the system and decreased expenditure for maintaining and inspecting the system. 
     The reliability of the system and of working results from the systems can thus be significantly improved. 
     Particularly in ATE systems, the invention allows to reliably carry out the respective testing. The monitoring points have to be carefully selected in order to draw conclusions about the tests to be performed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and many of the attendant advantages of the present invention will be readily appreciated and become better understood by reference to the following detailed description when considering in connection with the accompanied drawing, in which: 
     FIG. 1 shows an implementation of the invention in an ATE system. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows an implementation of the invention in an ATE system  10 . The system  10  comprises a plurality of subsystems  20 A,  20 B,  20 C, etc. In an IC tester application, the subsystems  20 A,  20 B,  20 C, etc. might be for example a cooler, a power control circuit, a clock generation circuit, etc. 
     Each one of the subsystems  20 A,  20 B,  20 C, etc. might comprise one or more monitoring points relevant and representative for certain parameters of the respective subsystem. In the example of FIG. 1, subsystem  20 A comprises a first monitoring point Al and a second monitoring point A 2 . Subsystem  20 B comprises no monitoring points, whereas subsystem  20 C comprises one monitoring point C 1 . It is to be understood that the number of monitoring points within one subsystem depends as well on the function and complexity of this respective subsystem as on the function of the subsystem within the entire system  10 . 
     Each one of the monitoring points A 1 , A 2 , C 1 , etc. is connected with a respective diagnosis module  25 A 1 ,  25 A 2 ,  25 C 1 , etc. for substantially permanently monitoring the respective monitoring point. Each respective diagnosis module generally works independently of other diagnosis modules. If the system  10  breaks down, the diagnosis modules  25 A 1 ,  25 A 2 ,  25 C 11  etc. are preferably maintained functional. The respective diagnosis module  25 A 1 ,  25 A 2 ,  25 C 1 , etc. are also able to communicate and to share data amongst each other. 
     In case the system  10  represents an IC tester and the subsystems might be a cooler, power control circuit, clock generation circuits, etc., the respective monitoring points might represent water temperature and pressure, primary and secondary voltages, clock frequencies and bus terminations, etc. 
     Turning again to FIG. 1, the diagnosis module  25 A 1 ,  25 A 2 ,  25 C 1 , etc. (and thus the monitoring points A 1 , A 2 , C 1 , etc.) are connected via a communication channel  30  with an evaluation unit  40 . The evaluation unit  40  might be part of the system  10  or separated therefrom as an independent unit. The evaluation unit  40  is preferably controlled by a software program which permanently monitors the monitoring points A 1 , A 2 , C 1 , etc. by requesting andlor automatically receiving data therefrom. 
     In a preferred embodiment, each one of the respective diagnosis modules  25 A 1 ,  25 A 2 ,  25 C 1 , etc. periodically signals in predetermined time intervals via the communication channel  30  whether the diagnosis module is still operable or not. The evaluation unit  40  and each other functional unit connected with the communication channel  30  receive the ‘alive signals’ from the respective diagnosis modules  25 A 1 ,  25 A 2 ,  25 C 1 , etc. and can draw conclusions therefrom. In case of a complete or partial in-operability of one diagnosis module, the evaluation unit  40  will signal this event to the user of the system  10 . 
     In a preferred embodiment, the diagnosis module  25 A 1 ,  25 A 2 ,  25 C 1 , etc. comprise respective micro-controllers (uC) which control the hardware implementation of the monitoring points A 1 , A 2 , C 1 , etc. The respective microcontrollers are also responsible for the communication and sharing of data between the diagnosis modules  25 A 1 ,  25 A 2 ,  25 C 1 , etc. of the subsystems  20 A,  20 B,  20 C, etc. The microcontrollers of each diagnosis module might also check if the other diagnosis modules in the system  10  are still functional by using a given communication protocol. 
     In case that the system  10  represents an IC tester and the subsystems might be a cooler, power control circuit, clock generation circuits, etc., and the respective monitoring points might represent water temperature and pressure, primary and secondary voltages, clock frequencies and bus terminations, etc., the respective diagnosis module  25 A 1 ,  25 A 2 ,  25 C 1 , etc. might for example measure the water temperature and pressure in respective water circuit loops, measure voltages and currents needed by the different hardware subsystems, and measure clock signals which are distributed in the whole system. 
     The communication channel  30  can be implemented as an industrial standard bus such as a controller area network (CAN). This allows a low cost, reliable and simple implementation of the communication channel  30 . Since most PCs or workstation computers are generally not equipped with a CAN interface, the communication with and between the respective diagnosis module  25 A 1 ,  25 A 2 ,  25 C 1 , etc. can be controlled by a specific communication controller  50  which might be part of the evaluation unit  40  or the system  10 . The communication controller  50  might transmit the respective data via a standard RS 232 interface. 
     The respective components for monitoring the system  10 , such as the monitoring points A 1 , A 2 , C 1 , etc., the diagnosis modules  25 A 1 ,  25 A 2 ,  25 C 1 , etc., and the evaluation unit  40 , are substantially independent of other functional units within the system  10  and thus only influence the system  10  to a minimum degree. 
     In a preferred embodiment, the evaluation unit  40  comprises a (not shown) signaling unit for emitting a signal on a line  60  in case that the evaluation unit  40  observes that a failure is occurring or when an observed parameter of the system  10  tends to drift. 
     A detailed example of a preferred embodiment is given the following, wherein the system  10  represents an IC-tester and the subsystem  20 A is embodied as a power controlling circuit. The monitoring point A 1  might be an external analog to digital converter (ADC) which is controlled by a micro controller (uC) within the diagnosis module  25 A 1  for measuring the primary voltage of the system  10 . The monitoring point A 2  is a test point for measuring a termination voltage of a communication bus within the system  10 . The monitoring point A 2  is directly connected with the internal ADC of the uC located in the diagnosis module  25 A 2 . 
     The subsystem  20 C is embodied as a cooler and the diagnosis module  25 C 1  (temperature sensor) monitors a water temperature at the monitoring point C 1 . The signal delivered from the monitoring point C 1  is fed to the uC implemented in the diagnosis module  25 C 1 . All micro controllers located within the diagnosis modules  25 A 1 ,  25 A 2  and  25 C 1  are connected with the communication controller  50  using a CAN network. The communication controller  50  is connected to the evaluation unit  40  (Unix workstation or PC) using an RS232 interface. 
     If the termination voltage measured at the monitoring point A 2  by the diagnosis module  25 A 2  changes and violates an upper or lower voltage limit, the failure is reported to the other diagnosis modules  25 A 1 ,  25 C 1  and to the communication controller  50  which transmits the failure condition to the evaluation unit  40 . The diagnosis modules  25 A 1  and  25 C 1  get the values (primary voltage, water temperature) from their monitoring points A 1  and C 1  and then latch this information. All data will then be requested by the evaluation unit  40  for reconstruction and evaluating the failure condition. The failure is then reported to the user of the IC-tester by emitting a signal on line  60 .