Abstract:
A control device may include an actuator for actuating a final control element on a cooling system of an internal combustion engine and a sensor for scanning a position of the final control element. A method for checking the control device may include the steps of triggering the actuator with a predetermined control signal, determining a progression of the control position scanned by the sensor, and determining the functional capability of the mechanical coupling of the actuator to the final control element on the basis of the predetermined control signal and the determined progression.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a U.S. National Stage Application of International Application No. PCT/EP2012/050557 filed Jan. 16, 2012, which designates the United States of America, and claims priority to DE Application No. 10 2011 003 430.7 filed Feb. 1, 2011, the contents of which are hereby incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    This disclosure relates to a method and to an apparatus for checking a control device. In this case, the control device comprises an actuator for operating an actuating element and a sensor for reading a position of the actuating element. 
       BACKGROUND 
       [0003]    Closed-loop control circuits are used in technical applications in order to move an actuating element to a predetermined position. By way of example, an electric motor can be used to change a rotation angle of a shaft, wherein a sensor is provided for reading the rotation angle of the shaft. As a function of a predetermined rotation angle and the rotation angle which is determined by the sensor, a control device provides a suitable signal to the electric motor in order to rotate the shaft in such a way that the read rotation angle corresponds to the predetermined rotation angle. The shaft can act on an actuating element, for example in order to influence a variable in another closed-loop control circuit. If the mechanical coupling between the shaft and the actuating element is now damaged, this cannot initially be established on the basis of the sensor signal since the sensor can still be moved to the predetermined rotation angle. 
       SUMMARY 
       [0004]    One embodiment provides a method for checking a control device, wherein the control device comprises an actuator for operating an actuating element in a cooling system of a internal combustion engine and a sensor for reading a position of the actuating element, comprising the following steps: actuating the actuator with a predetermined control signal; determining a profile of the actuating position which is read by the sensor; and determining the functioning of the mechanical coupling of the actuator to the actuating element on the basis of the predetermined control signal and the determined profile. 
         [0005]    In a further embodiment, a predetermined profile is associated with the predetermined control signal, and a defect in the mechanical coupling is determined if the determined profile deviates from the predetermined profile by more than a predetermined amount. 
         [0006]    In a further embodiment, a dynamic parameter of the mechanical coupling is determined on the basis of the determined profile, and a defect in the mechanical coupling is determined if the determined parameter deviates from a predetermined parameter by more than a predetermined amount. 
         [0007]    In a further embodiment, the parameter comprises mechanical damping. 
         [0008]    In a further embodiment, the parameter comprises mechanical inertia. 
         [0009]    In a further embodiment, the control device is part of a closed-loop control circuit for controlling a variable, and actuation is performed when the closed-loop control circuit is deactivated, so that the control device has no effect on the controlled variable. 
         [0010]    In a further embodiment, the closed-loop control circuit comprises a temperature control means for a cooling system for cooling an internal combustion engine in a motor vehicle, and actuation is performed when the internal combustion engine is turned off. 
         [0011]    In a further embodiment, the actuation is performed when the cooling system is also turned off. 
         [0012]    Another embodiment provides a computer program product having program code means for carrying out a method as claimed in one of the preceding claims, when the computer program product is run on a processing device or is stored in a computer-readable data storage medium. 
         [0013]    Another embodiment provides an apparatus for checking a control device, wherein the control device comprises an actuator for operating an actuating element in a cooling system of an internal combustion engine and a sensor for reading a position of the actuating element, wherein the apparatus comprises the following elements: a processing device for actuating the actuator with a predetermined control signal; a reading device for determining a profile of the actuating position which is read by the sensor, wherein the processing device is designed to determine the functioning of the mechanical coupling of the actuator to the actuating element on the basis of the predetermined control signal and the determined profile. 
         [0014]    In a further embodiment, the apparatus comprises a memory in which a predetermined profile of the actuating position which is associated with the control signal is stored, wherein the processing device is designed to detect a defect in the mechanical coupling if the determined profile deviates from the stored profile by more than a predetermined amount. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    Example embodiments are described in more detail below with reference to the drawings, in which: 
           [0016]      FIG. 1  shows a cooling system in an internal combustion engine of a motor vehicle; 
           [0017]      FIG. 2  shows a system model of the control device from  FIG. 1 ; 
           [0018]      FIG. 3  shows a graph of a pulse response of the control device from  FIG. 1 ; and 
           [0019]      FIG. 4  shows a flowchart of a method for checking the control device from  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    Some embodiments provide a method with which a defect in the mechanical coupling can be determined. Other embodiments provide a corresponding apparatus. 
         [0021]    A control device comprises an actuator for operating an actuating element in a cooling system of an internal combustion engine and a sensor for reading a position of the actuating element. A method according to the invention for checking the control device comprises the steps of actuating the actuator with a predetermined control signal, determining a profile of the actuating position which is read by the sensor, and determining the functioning of the mechanical coupling of the actuator to the actuating element on the basis of the predetermined control signal and the profile. 
         [0022]    In technical applications in which the sensor is not directly connected to the actuating element, the method can be used to determine a defective mechanical coupling of the actuator to the actuating element, even if the sensor is also mechanically coupled to the actuator. Integrated fault monitoring of the control device can be realized as a result. It is also possible, as a result, to mechanically couple the sensor directly to the actuator instead of to the actuating element, as a result of which a complicated mechanical coupling can be avoided and production costs can be reduced. 
         [0023]    The method can be carried out during normal operation of the control device by the profile of the read actuating position being put into context with a control signal which is generated on the basis of an open-loop or closed-loop control function of the control device. Furthermore, a dedicated control signal can be generated which can be meaningfully correlated with the read profile of the actuating position. 
         [0024]    In a first embodiment, a predetermined profile is associated with the predetermined control signal, and a defect in the mechanical coupling is determined if the determined profile deviates from the predetermined profile by more than a predetermined amount. The two profiles can be compared in a resource-saving and rapid manner, with the result that it is also possible to carry out the method using simple technical means. 
         [0025]    In another embodiment, a dynamic parameter of the mechanical coupling is determined on the basis of the determined profile, and a defect in the mechanical coupling is determined if the determined parameter deviates from a predetermined parameter by more than a predetermined amount. The amount of memory used for the predetermined parameters can be kept low by virtue of the parametric determination of the functioning of the mechanical coupling of the actuator to the actuating element. Furthermore, the dynamic parameter can be provided in order to improve, for example, an open-loop or closed-loop control function of the control device. 
         [0026]    The mechanical parameter can comprise mechanical damping and/or mechanical inertia. As a result, a defect in the mechanical coupling can be determined in a rapid and precise manner. In particular, a defect which is only just developing can be determined. 
         [0027]    The control device can be part of a closed-loop control circuit for controlling a variable, and actuation can be performed when the closed-loop control circuit is deactivated, with the result that the control device has no effect on the controlled variable. As a result, it is possible to check the mechanical coupling using any desired control signals. The method can be carried out before or after operation of the closed-loop control circuit, with the result that the functioning of the mechanical coupling can be monitored over the long term without repercussions, particularly in the case of intermittent operation of the closed-loop control circuit. 
         [0028]    The closed-loop control circuit can comprise a temperature control means of a cooling system for cooling an internal combustion engine in a motor vehicle, and actuation can be performed when the internal combustion engine is turned off. In a preferred embodiment, actuation is performed when the cooling system is also turned off. As a result, by way of example, after-cooling of the internal combustion engine or components which are connected to it can remain uninfluenced by the method being carried out. 
         [0029]    A computer program product having programming means for carrying out the described method can be run on a processing device or stored in a computer-readable data storage medium. 
         [0030]    An apparatus according to the invention for checking the above-described control device comprises a processing device for actuating the actuator with a predetermined control signal and a reading device for determining a profile of the actuating position which is read by the sensor. In this case, the processing device is designed to determine the functioning of the mechanical coupling of the actuator to the actuating element on the basis of the predetermined control signal and the determined profile. 
         [0031]    As a result, it is possible to design a control device such that the sensor is mechanically coupled to the actuator instead of to the actuating element, without having to run the risk of an unnoticed defective mechanical coupling of the actuating element to the actuator. 
         [0032]    In a preferred embodiment, the apparatus comprises a memory in which a predetermined profile of the actuating position which is associated with the control signal is stored, wherein the processing device is designed to detect a defect in the mechanical coupling if the determined profile deviates from the stored profile by more than a predetermined amount. 
         [0033]      FIG. 1  shows a cooling system  100  on an internal combustion engine  105  of a motor vehicle. The cooling system  100  is used by way of example in the text which follows to explain the invention, wherein the invention is not restricted to an actuating device on the shown cooling system  100 , but rather can be used, in principle, on any type of actuating element. 
         [0034]    In the cooling circuit  100 , heated coolant exits from the internal combustion engine  105  and is passed to a three-way valve  110 . Depending on the position of the three-way valve  110 , a first portion of the coolant is returned directly to the internal combustion engine  105 , while a second portion of the coolant is routed to a radiator  115  where the coolant is cooled before it is returned to the internal combustion engine  105 . The illustrated cooling system  100  can be realized in a large number of embodiments which are known by a person skilled in the art and is specified, by way of example, for an area surrounding a control device  120  which sets a position of the three-way valve  110 . 
         [0035]    The control device  120  comprises an actuator  125  which is connected to the three-way valve  110  by means of a first mechanical connection  130  and to a sensor  140  by means of a second mechanical connection  135 . The actuator  125  and the sensor  140  are each connected to a processing device  145 . The processing device  145  comprises a reading device for a signal which is provided by the sensor  140 . 
         [0036]    The processing device  145  preferably comprises a programmable microcomputer. The processing device  145  is also connected to a memory  150  and an interface  155 . 
         [0037]    The control device  120  receives a setpoint position, to which the three-way valve  110  is intended to be moved, via the interface  155 . As long as both the first mechanical connection  130  and the second mechanical connection  135  are intact, a sensor signal of the sensor  140  reflects the position of the three-way valve  110 . The processing device  145  calculates a difference between the setpoint position received via the interface  155  and the actual position which is read by means of the sensor  140  and outputs a corresponding control signal to the actuator  125  in order to bring the actual position closer to the setpoint position. 
         [0038]    Since a possibly hot and electrically conductive coolant flows through the three-way valve  110 , the sensor  140  is not coupled directly to the three-way valve  110  but rather to the actuator  125  by means of the second mechanical connection  135 . The second mechanical connection  135  can be designed in a highly operationally reliable manner on account of short connections and an installation space which is usually sufficient. By way of example, the three-way valve  110  and the sensor  140  can be arranged at different ends of a shaft which drives the actuator  125 . 
         [0039]    The first mechanical connection  130  between the actuator  125  and the three-way valve  110  may be exposed to a series of loads which can lead to damage or to wear of the first mechanical connection  130 . In this case, when the actuator  125  is actuated by the processing device  145  by means of a control signal, the sensor  140 , but not the three-way valve  110 , is adjusted. In order to determine a defect of this kind in the control device  120 , the processing device  145  detects a profile, which is read by means of the sensor  140 , of the actual position and compares this profile with a predetermined profile which is stored in the memory  140 . 
         [0040]    In one embodiment, a number of different predetermined profiles are stored in the memory  150 , said profiles being associated with different control signals of the processing device  145  to the actuator  125 . If the actuator  125  is not mechanically coupled to the three-way valve  110  owing to the defective first mechanical connection  130 , a difference is produced between the profile which is read by means of the sensor  140  and the predetermined profile which is stored in the memory  150 . If this difference exceeds a predetermined threshold, it is assumed that the first mechanical connection  130  is defective. 
         [0041]    In a variant, a dynamic parameter of the first mechanical connection  130  can be determined on the basis of the control signal which is output to the actuator  125  and the profile which is read by means of the sensor  140 . In this case, a corresponding predetermined dynamic parameter, which is again associated with the control signal in a preferred embodiment, is stored in the memory  150  instead of the profile. If the determined parameters and the parameters which are stored in the memory  150  differ by more than a predetermined amount, it is likewise assumed that the first mechanical connection  130  is defective. 
         [0042]    The defective first mechanical connection  130  can be determined both during operation of the control device  120  or of the cooling system  100  and also in a dedicated test run which is advantageously carried out outside normal operation of the cooling system  100 . In the test run, a control signal to the actuator  125  can be used, said control signal allowing particularly meaningful values to be compared. By way of example, the three-way valve  110  can be moved from one extreme position to another, a specific sequence of movements, preferably in alternating directions, can be used, or the three-way valve  110  can be adjusted to such an extent that it runs against a mechanical position limiting means. 
         [0043]      FIG. 2  shows a system model  200  of the control device  120  from  FIG. 1 . The system model  200  models the effect of the control signal which is provided by the actuator  125  from  FIG. 1  on the position which is read by means of the sensor  140 . 
         [0044]    The control signal  205  is reduced in a difference calculator  210  by a voltage which is generated by the electrical actuator  125  on account of its inherent induction. The resulting voltage is subjected to an electrical characteristic  215  which is formed substantially by an inductance and a resistance of the electrical actuator  125 . As a result, a constant current is set, this current being converted into a constant torque  220  which, for its part, is subjected to a dynamic behavior  225  of the mechanical components which are connected to the actuator  125 . The mechanical components comprise the first mechanical connection  130 , the three-way valve  110 , the second mechanical connection  135  and the sensor  140  in  FIG. 1 . If the first mechanical connection  130  is damaged, that is to say released, the mechanical influence of said first mechanical connection and the mechanical influence of the three-way valve  110  in the dynamic behavior  225  is absent. A moment of inertia J and damping B of the mentioned mechanical components are modeled in particular in the dynamic behavior  225 . 
         [0045]    An operating rate is set on account of the dynamic behavior  225 , the self-induction  230  which is sent to the difference calculator  210  being performed on the basis of said operating rate. Furthermore, the position of the actuator  125  which can be read by means of the sensor  140  is determined on the basis of the operating rate by means of integration  235  with respect to time. 
         [0046]    The presented technique is based on detecting a modified influence of the dynamic behavior  225  which is produced when the first mechanical connection  130  is only restricted or is no longer present at all. 
         [0047]      FIG. 3  shows a graph  300  of a pulse response of the control device  120  from  FIG. 1 . Time is plotted in the horizontal direction, an adjustment angle Φ of the three-way valve  110  is illustrated in an upper region of the illustration of  FIG. 3  and a voltage U of the control signal which is provided to the actuator  125  is illustrated in a lower region in a vertical direction. A profile  305  which describes a position Φ is illustrated in the upper region and a profile  310  which represents a control signal is illustrated in the lower region. For reasons of simplicity, a customary pulse-width modulation signal (PWM) is not used in this case, but rather a constant control voltage. In this case, it is assumed that the actuator  125  comprises an electric motor which controls the position of the three-way valve  110  over the rotation angle Φ. 
         [0048]    The control signal is activated at time t 1 . The profile  305  of the position Φ increases up to time t 2  at an increasing rate. The profile  305  of the position Φ increases at a constant rate until the control signal is switched off again at time t 3 . After time t 3 , the rate of the increase in the profile  305  is reduced, until there is no further change in the position Φ at time t 4 . 
         [0049]    The sections of the profile  305  of the position Φ between times t 1  and t 2  or between t 3  and t 4  provide information about the moment of inertia J and the damping B of the actuator  125  by the mechanical components which are driven by it. The greater, for example, the mass which is made to move by the actuator  125 , the greater the moment of inertia J and the greater the time periods between t 1  and t 2  or between t 3  and t 4 . The greater a mechanical frictional resistance of the actuator  125 , the greater the damping B and the smaller the time interval between t 3  and t 4 . 
         [0050]      FIG. 4  shows a flowchart of a method  400  for checking the control device  120  from  FIG. 1 . 
         [0051]    A temperature of the internal combustion engine  105  is detected in step  405 . In a subsequent step  410 , the detected temperature is compared with a predetermined value. In step  415 , a position which is provided to the control device  120  by means of the interface  155  is determined on the basis of this comparison. Steps  405  to  415  correspond to operation of a cooling system  100  in normal operation. 
         [0052]    As an alternative to steps  405  to  415 , stopping of the internal combustion engine  105  can also be determined in a step  420 , stopping of the cooling system  100  can be detected in a step  425 , and a position which is particularly suitable for the subsequent determination of the functioning of the first mechanical connection  130  can be provided in a subsequent step  430 , without operation of the internal combustion engine  105  being disturbed by the determination process. 
         [0053]    After the position has been provided in one of the described ways, the actuator  125  is actuated with a control signal, which has been determined on the basis of a difference of an existing position which is read by means of the sensor  140  and the position, in a subsequent step  435 . 
         [0054]    While the actuator  125  is actuated, a series of actuating positions is read by means of the sensor  140  in a step  440 . A profile is determined from the read actuating positions in a step  445 . 
         [0055]    In a first variant of the method  400 , the profile which is determined in step  445  is compared with a predetermined profile which is stored in the memory  150 . In a second variant of the method  400 , one or more dynamic parameters of the mechanical connection  130  between the actuator  125  and the three-way valve  110  are determined in a step  455 . The determined parameters are compared with predetermined parameters in a step  460 , said predetermined parameters being stored in the memory  150 . 
         [0056]    After the comparison of one of steps  450  or  460 , a check is made in a step  465  to determine whether the comparison results in a deviation which lies above a predetermined threshold value. If this is the case, it is concluded in a step  470  that the first mechanical connection  130  is defective. Otherwise, functioning of the first mechanical connection  130  is determined in a step  475 . In both cases, the method ends in a subsequent step  480 .