Abstract:
Current supplied to a group of components is selectively sensed so that the current supplied when a particular component is the only active component can be compared to a reference current indicative of proper component operation. If there is a discrepancy, an alert can be generated. Can be applied on a larger scale to allow isolation of a subsystem, then a group within the subsystem, then a component with the group, etc.

Description:
BACKGROUND AND SUMMARY  
         [0001]    Electrical components are designed to operate at particular levels of voltage, current draw, and other monitorable characteristics. For example, servo systems are designed to run at a set velocity, which is monitored via an encoder mounted on the servo. If the servo operates above or below the set point, the servo controls can detect the aberrant behavior of the servo by, for example, sensing a corresponding deviation in encoder frequency and attempt to correct for the encoder frequency error. If the error is easily corrected by the system, the correction takes place and the servo continues to function. However, if the error in encoder frequency (velocity) begins to exceed certain limits, the control system will determine that it can no longer operate within specification. When this occurs, the controller typically disables the servo motor drive and issues an alert, such as, for example, a numerical code, to the main control system. This alert tells the main controller that the servo is no longer operating and that a fault has been declared.  
           [0002]    The above sequence is a typical shutdown technique and reveals to the main control system that a servo hardware fault has occurred. No other information is passed on for evaluation to the tech rep or the customer. The problem that caused the error could well have been the motor hardware or could have been the load that is driven by the servo motor. If the problem is a marginal situation in either the load or the motor, determining the root cause could be difficult since faults might be intermittent. Also, there is no information stored in the system that could give a historical account of encoder frequency excursions that did not cause a shutdown. A history of encoder frequency values that shows poor behavior would be useful to service personnel, and there is thus a need for such a history. Tech reps or design engineers could use such a history to determine that, over a specified operating period, the frequency of the servo motor&#39;s deviations and the amplitude by which the motor had deviated from its set point.  
           [0003]    An onboard microprocessor can selectively monitor a component, such as a motor or a solenoid, by selectively sensing current used by the component. While supplying sensors for each component of a system is not practical with current technology, embodiments sense the current supplied to a group of components when only one of the components is operating. The sensed current can be compared to a reference current indicative of proper component operation, and the result of the comparison can be recorded. If there is a discrepancy, then the component is likely defective and should be serviced. Recording the result can include storing the result in a computer memory, displaying an alert when there is a discrepancy between the reference current and the current supplied to the group of components, and/or recording the circuit to which current was supplied during sensing. Additionally, embodiments can allow access to the recorded result via a computer network, an on-board display, and/or a computer connected to a direct-connect port, such as a serial port. Using recursion, embodiments can be used to detect groups of components or subsystems that are having trouble, groups of components or subsystems within those groups or subsystems, etc., until a particular aberrant component is identified.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]    [0004]FIG. 1 shows a schematic of a machine in which embodiments can be employed.  
         [0005]    [0005]FIG. 2 shows a schematic of systems of a machine in which embodiments might be employed.  
         [0006]    [0006]FIG. 3 shows a schematic of a portion of a machine to which embodiments can be applied and the components such a machine can include.  
         [0007]    [0007]FIG. 4 shows a schematic chart illustrating a method that can be executed in embodiments of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0008]    While this specification describes a technique that can identify an aberrant component, this is simply exemplary and one of ordinary skill in the art should realize that the technique can be applied to aberrant systems and groups of components without departing from the scope of the invention and recursively with whatever resolution might be appropriate for a particular application.  
         [0009]    Embodiments can be employed in a printing machine  1 , such as that shown in FIG. 1. Such printing machines typically include at least one main controller  10 , as the controllers seen schematically, for example, in FIG. 2, that can, among other things, control a servo motor  20 , as does the paper path controller  10 , that can include a servo encoder  21 . Such a main controller  10  typically includes at least one microprocessor  30 , which will often include on-board random access memory (RAM)  31  or the like and/or can have access to expanded RAM  32  or the like. The microprocessor  30  can also be part of a microcontroller  40  that itself can include onboard RAM  41  or the like and/or can have access to expanded RAM  42  or the like.  
         [0010]    The onboard microprocessor  30 , in embodiments, selectively monitors a group of components  20  that includes a component  21 , such as a motor, by sensing a characteristic of the component, such as current drawn by the group  20 . For example, to determine whether the component  21  were operating properly, the microprocessor  30  would sense current drawn by the group  20  when the component  21  was the only component operating. The onboard microprocessor  30  would compare the current drawn by the group  20  to a reference current value indicative of proper operation and store the results in a memory, such as a RAM  31 ,  32 , of the microprocessor. The data can remain in the memory for later retrieval or can be uploaded to another location, such as a main controller  10  or to non-volatile memory, such as a hard drive. The uploads can be continuous or at intervals. The system can be configured so that only those values outside of normal limits would be stored for analysis.  
         [0011]    Advantageously, embodiments can recursively employ this technique to monitor systems, subsystems, and subgroupings within subsystems on down to individual components, depending on the particular configuration of the machine  1  in which embodiments are employed and the particular resolution desired. As illustrated in  
         [0012]    In embodiments in which more components are monitored, more RAM  31 ,  32 ,  41 ,  42  can be necessary and more processing time can be required. Thus, in such embodiments, the microprocessor  30  should be relatively fast and have RAM  31 ,  32  available internally or externally for the storage. For example, the microprocessor  30  could be an Intel P89C51RB2 with 256 bytes RAM and 256 bytes Flash on board, or the microprocessor  30  could be of another type with external RAM chips for the micro&#39;s use. Additionally, a microcontroller  40  with 1 kB of internal RAM could be used in the six cycle clock mode. Running in this mode essentially doubles the internal speed of the controller&#39;s  40  processing capabilities. Therefore, for example, a P89C51RD2 (with 1 KB internal RAM  41 ) by Intel could be used that would run at twice the normal speed. This would be more than enough to handle the required processing. Additionally, for example, standard, off-the-shelf external RAM integrated circuits  42  could be used to augment data storage. Any amount of external RAM  42  would then be placed on the board that would meet the required storage needs.  
         [0013]    More real time would be needed to hand data from the target micro  30 ,  40  to the main controller  10 . Also, traffic on the serial bus system  11  would increase in order to get the data across. The main control unit  10  would be responsible for decisions about the health of the system according to its analysis, which would require additional real time from the main unit  10 .  
         [0014]    The system main controller  10  can thus obtain a history of aberrant component events, such as aberrant motor encoder events, or could even obtain histories of multiple components, subsystems, and systems in the machine. The main controller  10  could then make decisions about machine operation that could be communicated to, for example, service personnel. When a predetermined threshold of events is reached, for example, the machine diagnostics could alert service that a failure is eminent. Further, service could access this data, locally or remotely, and determine if further repairs are needed. The information obtained from the system could be used to determine the cause of an intermittent problem.  
         [0015]    A schematic illustration of a method executed in embodiments is shown in FIG. 4. The method can start, block  101 , and select and isolate a first component or group of components, block  102 . The selection and isolation can start with a default component or group of components to test, such as might be stored in a RAM  31  or ROM of the controller  10 . Once the component or from to be tested has been selected, current is sensed, block  103 . A reference current is retrieved for the component or group being tested, block  104 , which reference current can, for example, be stored in RAM  31  or ROM of the controller, or on a hard disk in communication with the controller. The sensed current and reference current are compared, block  105 , and if the sensed current is acceptable, a satisfactory result can be recorded, block  106 , the next component or group is identified, block  107 , and the method can return to block  102 . If the sensed current is not acceptable, then a fault is recorded, block  108 , an alert can be initiated, block  109 , and/or a record can be transmitted via a connected network, block  110 . If the fault was in a group, block  111 , then the next level of detail within that group can be resolved for testing, block  113 , the next component or group is identified, block  107 , and testing can continue from block  102 . If the fault was in a component, then, if any remain, the next component or group of components can be identified, block  112 , and testing can continue from block  102 . If there are no more components or groups to be tested, then testing can stop, block  114 .  
         [0016]    While embodiments have been described in the context of monitoring a motor encoder  21 , those of ordinary skill in the art should recognize that other components could be monitored using the method and apparatus described above. For example, this technique can be used on other applications such as sensor readings, power supply voltage readings, timing functions, and the recording of pulse width modulation (PWM) values. Data can be kept on almost any application that could help machine diagnostics. It could be accomplished at the firmware level as with the motor encoder and the data could be analyzed there or at the main control. Sensor pullin/pullout times and electromechanical clutch pullin/pullout times can be treated in the same manner. Power supply voltages can be monitored and any deviations be placed into their own histograms. Any device using PWM control would fit the algorithms of this technique. The histograms of all of these items, including paper path timing, could be stored on the microcontroller or microprocessor and read by the main control board or a remote computer at some convenient time. Further, the method can be applied recursively to test an entire machine&#39;s systems and subsystems.  
         [0017]    Other modifications of the present invention may occur to those skilled in the art subsequent to a review of the present application, and these modifications, including equivalents thereof, are intended to be included within the scope of the present invention.