Abstract:
A method and a circuit configuration for simulating fault states in a control unit, as well as a computer program and a computer-program product, are provided. In this context, a multiplexer and a fault-generating circuit are used, the multiplexer being realized using a relay technology, and the fault-generating circuit being implemented using a semiconductor technology.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method and a circuit configuration for simulating fault states in a control unit, particularly a control unit in a motor vehicle. 
     2. Description of Related Art 
     In vehicle control units, a considerable portion of the software is assigned to diagnostic functionalities. These diagnostics are intended to recognize faulty conditions in the vehicle, such as a line interruption, and to generate a corresponding entry for a fault memory. 
     Methods and circuit configurations for checking the functionality of electronic or electrical circuits are described in the related art. For example, published German patent document DE 197 21 366 describes an electrical circuit configuration, which is used for checking a series connection made up of a switch and a load. It includes a first circuit which is capable of detecting a first state, the first state representing a short-circuit of a connection point to a supply voltage, and a second circuit, connected in parallel to the first circuit, which is connected to the connection point and is used for detecting a second or a third state. The second state represents a short-circuit of the connection point to ground, and the third state represents an interruption of the connection point to the supply voltage. 
     The published German patent document DE 43 17 175 describes a self-testing device for memory arrays, decoders or the like, for use in an online operation. In that case, means are provided for checking a plurality of word lines and/or column lines, the word lines and/or column lines being connected to a check matrix, and a fault detector being connected to the check matrix and generating a fault signal if more than one line is activated at the same time. 
     A method for detecting faults in a motor vehicle is described in published German patent document DE 199 59 526. In that method, operating parameters and information for characterizing the operating parameters in a motor vehicle are acquired over a specific period of time. For the predictive detection of faults, it is suggested to create an operating-parameters pattern, to write an operating-parameters pattern in suitable form and to compare the operating parameters acquired instantaneously during the operation of the motor vehicle to the fault-characteristic operating-parameters pattern. 
     The circuit configuration introduced in the present invention is an electrical circuit which simulates typical faults that may occur in the vehicle. At present, various circuit configurations and methods are available for simulating faults in motor vehicles, these products offering the possibility of setting up various types of faults. Typical types of faults are listed in the following table. 
     
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 No. 
                 Type of fault: 
                 Circuit for generating the fault: 
               
               
                   
               
             
             
               
                 1 
                 Line interruption 
                 Opening the connection between a 
               
               
                   
                   
                 control-unit pin and a component 
               
               
                   
                   
                 in the peripherals 
               
               
                 2 
                 Short-circuit at 
                 Connection of the control-unit 
               
               
                   
                 plus/minus potential pin  
                 to the plus/minus potential 
               
               
                   
                 of the battery voltage 
                 of the battery voltage (or 
               
               
                   
                 (or another voltage) 
                 another voltage) 
               
               
                 3 
                 Contact corrosion at 
                 Switching-in of a resistor 
               
               
                   
                 the control-unit pin 
                 between a control-unit pin and a 
               
               
                   
                   
                 peripheral component 
               
               
                 4 
                 Short-circuit of two 
                 Connecting of two control-unit 
               
               
                   
                 control-unit pins 
                 pins 
               
               
                 5 
                 Crosstalk between two 
                 Connecting of two control-unit 
               
               
                   
                 control-unit pins 
                 pins via a resistor 
               
               
                 6 
                 Power losses due to 
                 Connection of a control-unit pin 
               
               
                   
                 leakage currents at 
                 to plus/minus potential of the 
               
               
                   
                 the control-unit pin 
                 battery voltage (or another 
               
               
                   
                   
                 voltage) with the aid of a resistor 
               
               
                   
               
             
          
         
       
     
     Typically, the faults are applied sequentially to the control-unit terminals or pins. In so doing, it is customary to use multiplexers. The expenditure for components can thereby be reduced considerably, since it is not necessary to establish a fault-simulation circuit for each channel. 
     It is known to create circuits using only Metal-Oxide-semiconductor Field-Effect Transistor (MOSFET) technology or only relay technology. Various disadvantages of these two procedures according to the related art can be concluded from the following Table 2. 
     
       
         
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                 MOSFET 
                   
               
               
                 No. 
                 Description 
                 technology 
                 Relay technology 
               
               
                   
               
             
             
               
                 1 
                 Switching  
                 ++ Rapid 
                 −− Slow switching 
               
               
                   
                 speed 
                 switching due to  
                 due to delayed 
               
               
                   
                   
                 semiconductor 
                 pick up/release 
               
               
                   
                   
                 technology 
                 of the relay 
               
               
                   
                   
                   
                 contact and due 
               
               
                   
                   
                   
                 to bouncing 
               
               
                 2 
                 Wear 
                 ++ No wear, 
                 −− Wear due to 
               
               
                   
                   
                 since no 
                 mechanics, and by 
               
               
                   
                   
                 mechanically 
                 erosion of the 
               
               
                   
                   
                 moving parts are  
                 contacts 
               
               
                   
                   
                 used. 
                   
               
               
                 3 
                 Costs (switch 
                 −− High costs, 
                 ++ Low costs, 
               
               
                   
                 technology is  
                 since two 
                 since no 
               
               
                   
                 the main driver  
                 MOSFETs per 
                 expensive 
               
               
                   
                 of costs) 
                 switching 
                 circuitry is 
               
               
                   
                   
                 contact and 
                 needed and relays 
               
               
                   
                   
                 electrical 
                 are inexpensive 
               
               
                   
                   
                 isolation 
                 to acquire in the 
               
               
                   
                   
                 between drive 
                 marketplace. 
               
               
                   
                   
                 and useful 
                   
               
               
                   
                   
                 signal are 
                   
               
               
                   
                   
                 necessary. 
                   
               
               
                 4 
                 Problem case— 
                 −− Since only a 
                 ++ By complete 
               
               
                   
                 line interruption 
                 high-resistance 
                 separation of the 
               
               
                   
                   
                 state and no 
                 connection 
               
               
                   
                   
                 interruption 
                 between the 
               
               
                   
                   
                 between the 
                 control-unit pin 
               
               
                   
                   
                 control-unit pin  
                 and peripherals, 
               
               
                   
                   
                 and peripherals 
                 the type of fault 
               
               
                   
                   
                 can be produced,  
                 is always clearly 
               
               
                   
                   
                 in many cases, 
                 recognized in the 
               
               
                   
                   
                 the diagnosis in  
                 control unit. 
               
               
                   
                   
                 the control unit 
                   
               
               
                   
                   
                 is incorrect. 
               
               
                   
               
               
                 ++ Advantage 
               
               
                 −− Disadvantage 
               
             
          
         
       
     
     A BRIEF SUMMARY OF THE INVENTION 
     The method of the present invention for simulating fault states in a control unit provides that terminals of the control unit to be checked are connected via a multiplexer to a fault-generating circuit, the multiplexer being realized using a relay technology, and the fault-generating circuit being implemented using a semiconductor technology. 
     The circuit configuration of the present invention is used for simulating fault states in a control unit and includes a multiplexer and a fault-generating circuit, the multiplexer being realized using a relay technology, and the fault-generating circuit being implemented using a semiconductor technology. 
     The goal of the circuit configuration according to the present invention for simulating faults is to optimize costs and to improve the switching properties by the combination of semiconductor and relay technology. In this context, the circuit configuration includes two parts:
     1. multiplexer circuit   2. fault-generating circuit   

     A transistor logic, preferably using MOSFETs, may be used as semiconductor technology. 
     The computer program of the present invention includes program code means for implementing a method according to the invention. 
     The computer-program product of the present invention includes precisely these program code means, which are stored on a machine-readable data carrier. 
     It is understood that the aforementioned features and the features yet to be explained below may be used not only in the combination indicated in each instance, but also in other combinations or by themselves, without departing from the scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  shows an example embodiment of the circuit configuration according to the present invention in schematic representation. 
         FIG. 2  shows a multiplexer and a fault-generating circuit. 
         FIG. 3  shows a drive circuit for the circuit configuration according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is represented schematically in the drawing in light of exemplary embodiments, and is described in detail below with reference to the drawing. 
       FIG. 1  shows an example embodiment of the circuit configuration according to the present invention in schematic representation, which is denoted altogether by reference numeral  10 . To be seen are a multiplexer  12 , a fault-generating circuit  14  and a microcontroller  16  which takes on the control of the sequences of the fault simulation and therefore the control of the interactions between multiplexer  12  and fault-generating circuit  14 . 
     Multiplexer  12  has a number of inputs  18  for the terminals, pin  1  through pin X, of the control unit to be checked, and a number of outputs  20  for driving the terminals of actuators and sensors. 
     Fault-generating circuit  14  has two voltage inputs (voltages U 1  and U 2 ), denoted by reference numerals  22  and  24 , for the voltages necessary for the fault simulation, like, for example, a battery voltage. 
     Multiplexer  12  and fault-generating circuit  14  communicate via two bidirectional signal lines  26  and  28 , which are also denoted as rail 1  (reference numeral  26 ) and rail 2  (reference numeral  28 ). 
     Multiplexer  12 , i.e., the multiplexer circuit, is realized using relay technology, and fault-generating circuit  14  is implemented using MOSFET technology. A fault is generated by pre-configuring it in the first step, and activating it in the second step at the desired instant. Since this switch to active may always be realized by MOSFETs, it is possible to control the time behavior exactly. 
     The disadvantages indicated in the products available at present can be avoided by this procedure. 
     Disadvantage No. 1—Switching Speed: 
     Since the fault is always switched to active by MOSFETs, the time behavior is defined and the switching speed is correspondingly high (order of magnitude 20 μs). 
     Disadvantage No. 2—Wear: 
     Typically, all connected control-unit pins are fault-simulated in sequence. For each fault, fault-generating circuit  14  must switch to a fault state and back again to the initial state. When using the multiplexer relays, a channel is needed only a few times per simulation run-through; the switching cycles per relay are correspondingly small. In comparison to multiplexer circuit  12 , fault-generating circuit  14  must switch much more frequently. Since fault-generating circuit  14  is realized using MOSFET technology and multiplexer circuit  12  is realized using relay technology, the wear is minimized. 
     Disadvantage No. 3—Costs: 
     Multiplexer  12  is implemented using cost-effective relay technology. Only 12 MOSFETs (in each instance in groups of two) are needed for fault-generating circuit  14 . For example, if a product having 64 channels is offered, 192 relays and 12 MOSFETs are needed. Costs are thereby minimized. 
     Disadvantage No. 4 Problem Case—Power Interruption: 
     The power interruption is implemented redundantly in MOSFET and relay technology. Therefore, one or the other technology may be used from case to case. 
       FIG. 2  shows a circuit configuration  40  having a multiplexer  42  and a fault-generating circuit  44  for simulating faults. 
     Multiplexer  42  includes four input channels  46  for the control-unit terminals, pin  1  (reference numeral  48 ), pin  2  (reference numeral  50 ), pin  3  (reference numeral  52 ) and pin  4  (reference numeral  54 ). The connections to the fault-generating circuit are provided by rail 1  (reference numeral  56 ) and rail 2  (reference numeral  58 ). These fault rails  56  and  58  represent the connection between the output of multiplexer  42  and the input of fault-generating circuit  44 . 
     Multiplexer relays K 11  (reference numeral  60 ), K 21  (reference numeral  62 ), K 31  (reference numeral  64 ) and K 41  (reference numeral  66 ) are provided for rail 1   56 . In the energized state, these relays switch the control-unit signal through to rail 1   56 . 
     Multiplexer relays K 12  (reference numeral  70 ), K 22  (reference numeral  72 ), K 32  (reference numeral  74 ) and K 42  (reference numeral  76 ) are used as interrupter relays. In the energized state, these relays interrupt the signal flow between the control-unit pin and the sensor/actuator. 
     Multiplexer relays K 13  (reference numeral  80 ), K 23  (reference numeral  82 ), K 33  (reference numeral  84 ) and K 43  (reference numeral  86 ) are provided for rail 2 . In the energized state, these relays switch the control-unit signal through to rail 2   58 . 
     Fault-generating circuit  44  includes six MOSFETs: M 1  (reference numeral  90 ), M 2  (reference numeral  92 ), M 3  (reference numeral  94 ), M 4  (reference numeral  96 ), M 5  (reference numeral  98 ) and M 6  (reference numeral  100 ). They realize e fault-generating circuit  44 . 
     Also provided is a resistor cascade R cascade  denoted by reference numeral  102 . This resistor cascade  102  is used for faults which require simulation of resistance. 
     In addition, a first voltage input  104  is provided for a voltage U 1 , and a second voltage input  106  is provided for a voltage U 2 . These voltages are needed to simulate faults which require an external voltage. 
     In this case, typically the voltage of the vehicle battery or of a voltage stabilizer is connected. However, any other voltage source as desired may also be used. Sensors and actuators are connected to outputs  108 . 
     Circuit configuration  40  shown is suitable for realizing or simulating all types of faults which correspond to the related art (see Table 1). Since these faults are switched using MOSFETs, the time behavior is suitable for the real-time fault simulation. 
     The individual faults are explained with reference to the circuit diagram in  FIG. 2 . In this context, there is a distinction made between fault configuration and fault activation. The fault configuration is needed to prepare the fault case, but the control unit detects no change in the signal behavior. The fault activation then alters the signal behavior at the control-unit pin; the control unit is now able to recognize a fault. 
     To keep the description general, in the case of the relays of the multiplexer, the first numeral of the relay name is replaced by an “X”, the X standing for the channel number which, in principle, may be as large as desired. In the case of the fault activation, it is necessary to pay attention to the indicated sequence, so that the signal flow takes place in the manner desired. 
     No Fault Active: 
     This is the default state, when no fault is active. All relays of multiplexer circuit  42  are in the currentless state; all MOSFETS are in the non-conductive state. The signal flow between the control-unit pin and the sensor/actuator is produced via relays K 12 , K 22  . . . . 
     Fault Type 1: Line Interruption 
     A. Line Interruption Via Relay 
     Fault Configuration 
     No configuration is necessary for this case. 
     Fault Activation 
     Break-contact relay KX 2  is energized and therefore interrupts the signal flow between the control-unit pin and the sensor/actuator. 
     B. Line Interruption Via MOSFET 
     Fault Configuration 
     
         
         
           
             Relays KX 1  and KX 3  are energized, and therefore produce a connection to rail 1   56  and rail 2   58 . 
             MOSFETs M 5   98 , M 2   92 , M 6   100  become conductive, and therefore connect rail 1   56  to rail 2   58 . The result is that the signal flow between the control-unit pin and the sensor/actuator is produced both via relay KX 2  and via rail lines  56  and  58 . 
             Relay KX 2  is energized, causing the break-contact element of the relay to open. The signal flow between the control-unit pin and the sensor/actuator is now produced only via rail lines  56  and  58 .
 
Fault Activation
 
           
         
       
    
     MOSFET M 2   92  is opened. The signal flow between the control-unit pin and the sensor/actuator is now interrupted. 
     Fault Type 2: Short-Circuit at Plus/Minus Potential of the Battery Voltage (or Another Voltage) 
     Fault Configuration 
     
         
         1. Case—Fault simulation via U 1   104   
       
    
     Relay KX 1  is energized and MOSFET M 5   98  becomes conductive.
     2. Case—Fault simulation via U 2   106     

     Relay KX 3  is energized and MOSFET M 6   100  becomes conductive. 
     Fault Activation 
     
         
         1. Case—Fault simulation via U 1   104   
       
    
     MOSFET M 1   90  becomes conductive.
     2. Case—Fault simulation via U 2   106     

     MOSFET M 4   96  becomes conductive. 
     Fault Type 3: Contact Corrosion at the Control-Unit Pin 
     Fault Configuration 
     
         
         
           
             Relays KX 1  and KX 3  are energized, and therefore produce a connection to rail 1   56  and rail 2   58 . 
             MOSFETs M 5   98 , M 2   92 , M 6   100  become conductive and thus connect rail 1   56  to rail 2   58 . The result is that the signal flow between the control-unit pin and the sensor/actuator is produced both via relay KX 2  and via rail lines  56  and  58 . 
             Relay KX 2  is energized, causing the break-contact element of the relay to open. The signal flow between the control-unit pin and the sensor/actuator is now produced only via the rail lines. 
             The desired resistance value is set at resistor cascade  102 .
 
Fault Activation
 
           
         
       
    
     MOSFET M 2   92  becomes non-conductive, and MOSFET M 3   94  becomes conductive at the same time. 
     Fault Type 4: Short-Circuit of Two Control-Unit Pins 
     Fault Configuration 
     
         
         
           
             The first control-unit pin is transferred to rail 1   56  by the energizing of KX 1 . 
             The second control-unit pin is transferred to rail 2   58  by the energizing of KX 3 . 
             MOSFETs M 6   100  and M 5   98  become conductive.
 
Fault Activation
 
           
         
       
    
     MOSFET M 2   92  becomes conductive. 
     Fault Type 5: Crosstalk Between Two Control-Unit Pins 
     Fault Configuration 
     
         
         
           
             The first control-unit pin is transferred to rail 1   56  by the energizing of KX 1 . 
             The second control-unit pin is transferred to rail 2   58  by the energizing of KX 3 . 
             MOSFETs M 6   100  and M 5   98  become conductive. 
             Resistor cascade  102  is set to the desired value.
 
Fault Activation
 
           
         
       
    
     MOSFET M 3   94  becomes conductive. 
     Fault Type 6: Power Losses Due to Leakage Currents at the Control-Unit Pin 
     Fault Configuration 
     
         
         
           
             Relays KX 1  and KX 3  are energized, and therefore produce a connection to rail 1   56  and rail 2   58 . 
             MOSFETs M 5   98 , M 2   92 , M 6   100  become conductive and therefore connect rail 1   56  to rail 2   58 . The result is that the signal flow between the control-unit pin and the sensor/actuator is produced both via relay KX 2  and via rail lines  56  and  58 . 
             Relay KX 2  is energized, causing the break-contact element of the relay to open. The signal flow between the control-unit pin and the sensor/actuator is now produced only via the rail lines. 
             The desired resistance value is set at resistor cascade  102 .
 
Fault Activation
 
           
         
       
    
     The leakage currents are able to flow either via U 1  or via U 2 .
     1. Case: Leakage current flows via U 1   104     

     M 5   98  and M 2   92  become non-conductive. 
     M 3   94  and M 1   90  become conductive.
     2. Case: Leakage current flows via U 2   106     

     M 6   100  and M 2   92  become non-conductive. 
     M 3   94  and M 4   96  become conductive. 
       FIG. 3  shows a drive circuit  120  for driving the circuit configuration according to the present invention. It includes one microcontroller  122 , three shift registers  124 , two relay drivers  126 , one multiplexer relay  128 , one relay resistor cascade  130 , one MOSFET  132 , one Ethernet device  134  and one CAN bus transmitter  136 . The internal communication takes place via an activation line  138  and a serial bus  140 . The drive circuit is to be operated at a CAN bus  142  or an Ethernet  144 . 
     The communication between a fault-simulation device and a higher-level master computer takes place via CAN  142  or Ethernet  144 . Using the firmware in microcontroller  122  of the fault-simulation device, the system is able to realize all faults indicated above. Typically, microcontroller  122  communicates with shift registers  124  via a serial protocol. 
     These registers  124  convert a serial bit stream into signals, which are present in parallel at the output pins of the register. To ensure that the signals are applied simultaneously to all pins of shift registers  124 , an edge must be triggered on activation line  138  by microcontroller  122 . The parallel signals at registers  124  are amplified by relay drivers  126 , and relay  128  is therefore switched.