Abstract:
A method for the control of an assembly by a control unit, in particular in a motor vehicle, wherein the assembly includes at least one component, at least one actuator associated with the component, and an additional control unit having a first non-volatile memory section that is connected to the control unit. The control unit includes a second non-volatile memory section. Classification information associated with the assembly and stored in the first non-volatile memory section is read out and transmitted to the control unit. The transmitted classification information is stored in the second non-volatile memory section. Subsequently, the classification information stored in the second, non-volatile memory section is read out and transmitted to the additional control unit. The disclosure furthermore relates to an assembly group that comprises the assembly and the control unit, with the control unit and the additional control unit of the assembly being connected to one another by a data transmission path.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit and priority of German Patent Application No. 10 2007 062 675.6, filed Dec. 24, 2007. The entire disclosure of the above application is incorporated herein by reference. 
     FIELD 
     The present disclosure relates to a method for the control of an assembly by a control unit, in particular in a motor vehicle. The assembly includes at least one component, at least one actuator associated with the component, and an additional control unit having a first non-volatile memory section that is connected to the control unit, with the control unit including a second non-volatile memory section. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     An assembly of this kind may be a transfer case, for example, that allows a direct distribution of a driving torque between two wheels of an axle of the motor vehicle and/or—with an all-wheel drive vehicle—a direct distribution of the driving torque between a front axle and a rear axle of the motor vehicle. 
     Such assemblies have to be controlled with high accuracy to be able to carry out the distribution of the driving torque with the required precision. However, hardly avoidable tolerances occur in their manufacture that result in deviations in the response behavior of the assemblies. These deviations are determined individually for the purpose of a calibration, with a respective tolerance class being associated with the assemblies in accordance with a predetermined classification scheme. The respectively determined tolerance class of a specific assembly may be taken into account by the associated control unit of the vehicle to control the assembly with the desired precision. 
     There is a problem in connection with a classification of controllable assemblies—whether in automotive engineering or in other fields—in that the respective assembly and the control unit associated therewith are sometimes installed independently of one another. A teach-in process therefore usually takes place after the installation of the assembly and the control unit in which the respective then current classification of the assembly used is communicated to the control unit and is stored in it. If a replacement or repair of the assembly and/or of the control unit takes place later, for example in case of service, the teach-in process has to be carried out again so that the correct control of the assembly by the control unit is in turn ensured. 
     It has already been proposed to encode the classification of an assembly with the help of an additional coding plug. DE 103 33 651 A1, for example, describes a coding plug that can be connected directly or indirectly to a control unit and which has a fixed electric circuit. A defined electrical state may be generated by the fixed circuit in the control unit and the state is detected and compared with stored data. The electrical state is then associated with a tolerance class of the assembly that may in turn be used for the adaptation of maps/characteristics for the control of the assembly. 
     It is, however, disadvantageous with this solution that an additional failure risk of the controllable assembly arises due to the coding plug made as an additional component. Furthermore, the reading out, decoding and comparing of the classification information stored in the circuit of the coding plug may only be realized in a relatively complex and/or expensive manner. In addition, the coding plug likewise has to be replaced on a change of the tolerance class of the assembly. Ultimately, it thus cannot be precluded that a coding plug is connected to the controllable assembly that contains an incorrect classification so that the classification read out of the coding plug by the control unit does not reflect the correct tolerance class of the assembly. The control of the assembly is thereby even made worse under certain circumstances—in comparison with a control solution without any consideration of the tolerance class. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     It is an object of the present disclosure to provide a method for the control of an assembly that ensures in a simple and reliable manner that the assembly is controlled by the control unit while taking account of the respective then current classification information. 
     It is furthermore an object of the present disclosure to provide an assembly group that includes a controllable assembly and a control unit that may be operated in a corresponding manner reliably and while taking account of the respective then current classification information. 
     As already initially mentioned, the present disclosure relates to a method for the control of an assembly by a control unit, wherein the assembly includes at least one component, at least one actuator associated with the component, and an additional control unit having a first non-volatile memory section and which is connected to the control unit, with the control unit including a second non-volatile memory section. 
     In accordance with the disclosure, classification information associated with the assembly and stored in the first non-volatile memory section is read out and transmitted to the control unit. The transmitted classification information is stored in the second non-volatile memory section. Subsequently, the classification information stored in the second non-volatile memory section is read out and transmitted to the additional control unit. 
     In other words, a bidirectional exchange of classification information takes place between the additional control unit and the control unit, with it not being significant which of the two units actively initiates or carries out the transmission of the classification information. It is, for example, possible that a respective one of the control units is responsible for one of the transmission directions or that one of the control units controls both transmission directions. 
     It is, however, important that the classification information stored in the first non-volatile memory section is stored after the reading out and the transmission to the control unit in the second non-volatile memory section there. This classification information is read out again and is transmitted back to the additional control unit. Generally, the method may also start with the reading out of the memory content of the second non-volatile memory section and with the transmission of the classification information to the additional control unit. 
     The data exchange between the control unit and the additional control unit ensures that classification information associated with the actually installed assembly is always exchanged. For example, on a change of the classification information stored in the first non-volatile memory section, the classification information is transmitted to the control unit by the method in accordance with the disclosure and is stored there in its second non-volatile memory section. The classification information transmitted back to the additional control unit may be used, for example, for comparison purposes, test purposes, or other purposes. After the transmission of the classification information in the control unit, the new classification is in every case present there and may be used, for example, for optimization of the assembly control. 
     The classification information transmitted to the additional control unit is preferably stored in the first non-volatile memory section if the first non-volatile memory section does not contain any classification information. This may be the case, for example, if the additional control unit was replaced or if the memory content of the first non-volatile memory section was deleted. The additional control unit then receives the classification information stored in the second non-volatile memory section of the control unit, whereby the data loop is again completed. 
     In a further embodiment of the present disclosure, the classification information transmitted to the additional control unit is not stored in the first non-volatile memory section if the first non-volatile memory section already contains classification information. This, for example, prevents the overwriting of previously stored and assembly-specific classification information. The non-stored classification information may be ignored or may be further processed for comparison purposes. 
     In a preferred embodiment of the present invention, the classification information is used by the control unit for the adaptation of at least one map or of at least one characteristic to improve the control of the assembly. The relationship stored in the control unit between a control signal and the thereby generated response of the assembly may, for example, be modified in dependence on the classification information to obtain a corrected relationship that allows a more precise control of the assembly. 
     Provision may furthermore be made that the classification information is composed of at least two pieces of partial information, with one of the pieces of partial information being associated with the component as a component classification and the other piece of partial information being associated with the actuator as an actuator classification. This allows an even more individual taking into account of the individual components of the assembly on its control. Changes in the tolerance class of the component and/or of the actuator—for instance, on a repair or a replacement of the component and/or of the actuator—may thereby, for example, be taken into account separately from one another. Further components of the assembly may likewise be taken into account by corresponding pieces of partial information. Generally, pieces of partial information may also be provided that do not contain any tolerance class information, such as serial numbers or the like. 
     In accordance with a further embodiment of the method in accordance with the disclosure, the pieces of partial information of the classification information stored in the second non-volatile memory section are overwritten by the corresponding pieces of partial information transmitted to the control unit, whereby it is prevented that different pieces of information that may differ from one another are collected in the second non-volatile memory section. The then currently valid pieces of partial information are therefore always present in the control unit due to the overwriting. It must be noted in this connection that in each case only the corresponding pieces of partial information are overwritten by new pieces of partial information, (i.e., a stored value of the then current component classification should, for example, not be overwritten by a value of the actuator classification, but rather the component classification value stored in the second non-volatile memory section should be overwritten by the component classification value transmitted by the additional control unit). A comparison of the stored component classification value with the transmitted component classification value before the storing is not necessary in this respect. A check only has to be made whether the transmitted component classification value is “empty” or is flagged as “empty”, for example by the value “0”. If the transmitted classification information contains, for example, only a first piece of partial information (i.e., a second piece of partial information is “empty” or is flagged as an “empty” piece of partial information) only the transmitted first piece of partial information is used for the overwriting of the first piece of partial information stored in the second non-volatile memory section. A second piece of partial information stored there is not overwritten or changed. 
     It is preferred that the actuator and the additional control unit associated with it are replaced by a replacement actuator and by a replacement additional control unit associated with it in case of service, with its first non-volatile memory section only including the actuator classification. In other words, the first non-volatile memory sections does not contain any component classification if the component was not replaced in the course of the servicing. In accordance with the method in accordance with the disclosure, the valid component classification is still stored in the control unit and, after the replacement of the actuator and of the additional control unit, it is again transmitted to the latter and is stored there to complete the data loop. 
     It is preferred if, in the case described above, the actuator classification includes information characterizing a typical actuator or information individually determined for the replacement actuator. The first variant is particularly cost-effective since it only provides for the storage of an actuator classification of a typical or “average” actuator. Costs are saved due to the waiving of an individual characterization of the replacement actuator and the storage of the corresponding actuator classification, while an at least “averagely” good control of the actuator still remains possible. The second variant in contrast allows a more precise control of the assembly; however, it is associated with an increased effort and/or cost. 
     It is generally possible that, on a replacement of the component and/or of the actuator without a replacement of the additional control unit, the component classification and/or the actuator classification are each replaced by information that characterizes a typical component or a typical actuator or that was determined individually for the component or for the replacement actuator. The procedure of the first variant includes, for example, a resetting of the additional control unit to default values of the component classification and of the actuator classification since the obsolete classifications associated with the previously used components could result in worse control results in interaction with the new components. The second variant in contrast allows a more precise control of the assembly; however, it is associated with an increased effort and/or cost. 
     In accordance with a further embodiment of the method in accordance with the disclosure, the pieces of partial information transmitted to the additional control unit are not stored in the first non-volatile memory section if the first non-volatile memory section already contains values for the corresponding piece of partial information. In other words, a check is made whether the parts of the first non-volatile memory section associated with the individual pieces of partial information are “empty” or are flagged as “empty”—for example by the value “0”—before a storage of the corresponding piece of partial information takes place. It should be prevented in this way that information stored in the additional control unit is overwritten. Provision may furthermore be made that the pieces of partial information transmitted to the additional control unit is stored in the first non-volatile memory section if the first non-volatile memory section does not contain any values for the corresponding pieces of partial information. In this variant of the method, in particular the total classification information is stored if only the additional control device was replaced and does not have an empty first non-volatile memory section, or a first non-volatile memory section flagged as “empty”, but the actuator and the component were not replaced. In this case, the memory content of the first non-volatile memory section is updated again by the data transmitted by the control unit. 
     It has proved to be advantageous if the classification information associated with the assembly and/or the pieces of partial information associated with the individual components of the assembly is/are determined ex works (i.e., where the individual components are manufactured) and is/are stored in the first non-volatile memory section. 
     The transmission of the classification information to the control unit can take place at predetermined times or after reception of a request signal. This can, for example, be done regularly or after an initialization at the start of an ignition procedure of the vehicle. Furthermore, the transmission of the classification information to the additional control unit may also take place at predetermined times or after reception of a request signal, in particular after reception of data from the additional control unit or at regular intervals. 
     The classification information preferably includes information on the tolerance class of the component and/or of the actuator, in particular to adapt at least one map/one characteristic to control the assembly. 
     A more complex and/or expensive embodiment, but one that allows a particularly precise control of the assembly, provides that the classification information includes a map/a characteristic of the assembly, of the component and/or of the actuator. For example, a torque characteristic is transmitted which covers the total torque range of a torque transmission clutch. 
     As already initially mentioned, the present disclosure also relates to an assembly group that has a controllable assembly and a control unit, in particular for a motor vehicle, with the controllable assembly including at least one component, at least one actuator associated with the component and an additional control unit having a first non-volatile memory section, with the control unit including a second non-volatile memory section and with the control unit and the additional control unit being connected to one another by a data transmission path. 
     In accordance with the disclosure, the first non-volatile memory section is made for the storage of classification information associated with the assembly, whereas the data transmission path is designed such that the classification information may be transmitted from the additional control unit to the control unit and vice versa. The control unit is made for the transmission of the classification information to the additional control unit. A two-way transmission of the classification information between the additional control unit and the control unit is thereby made possible in order, for instance, also always to have current classification information present after a case of servicing. 
     The additional control unit preferably includes a test unit that is made to check the memory content of the first non-volatile memory section and to store the classification information, or parts thereof, transmitted to the additional control unit in the first non-volatile memory section if no classification information or if incomplete classification information is stored in the first non-volatile memory section—for instance, classification information not including all pieces of partial information. In other words, it is determined by the test unit whether the memory content of the first non-volatile memory section is “empty” or is flagged as “empty”—in part or in total. In this respect, it is not the stored value of the information which is important, but rather whether this information is present at all, with it having to be pointed out in this connection that specific values—such as “0”—can only serve as a flag to indicate that the corresponding information is not present. If no partial information or no corresponding pieces of partial information is/are present, this is stored in the first non-volatile memory section. The test unit thus ensures that always current information is stored in the additional control unit. 
     In addition, the control unit may include a memory unit which is made to overwrite the classification information, or parts thereof, stored in the second non-volatile memory section by the classification information, or corresponding parts thereof, transmitted by the additional control unit. The information present in the control unit is updated by the overwriting. This procedure moreover saves memory space. 
     In accordance with an embodiment of the assembly group in accordance with the information, some of the pieces of classification information may be transmitted over the data transmission path and/or may be stored in and/or read out of the first and second non-volatile memory sections independently of one another. 
     The component is preferably a torque transmission clutch. The assembly may be a transfer case. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is a schematic representation of a part of a motor vehicle with a controllable assembly made in accordance with the disclosure; and 
         FIG. 2  is a schematic design of a controllable assembly made in accordance with the disclosure with a control unit connected thereto. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     A powertrain  10  of a motor vehicle having a drive  12  is shown schematically in  FIG. 1 . The drive  12  includes an engine  14  and a transmission  16  that is connected to a transfer case  20  via a drive shaft  18 . The transfer case  20  serves to distribute the driving torque of the engine  14  as required via output shafts  36  to a front axle  22  and/or to a rear axle  24  of the vehicle. Depending on the driving situation, the driving torque may, for example, only be transferred by the transfer case  20  to one of the axles  22 ,  24  or to both axles  22 ,  24  in variable proportions. The axles  22 ,  24  each include a differential unit  26  that is provided for the compensation of speed differences between wheels  28 . 
     To be able to influence the different driving situations of the vehicle, the vehicle has a control unit  30  that receives information on the state and on the movements of the vehicle and its environment via a plurality of sensors (not shown). This data is logged and evaluated by the control unit  30 . The evaluation of the data allows the generation of control signals that are in turn transmitted to the components of the vehicle to control the vehicle in the desired manner. For example, control lines  50  are shown in  FIG. 1  which connect the control unit  30  to the engine  14 , to the transmission  16 , and to the transfer case  20 . A data bus, in particular a CAN bus, may also be provided instead of separate control lines  50 . The control signals are in particular present in a digital format. 
       FIG. 2  is a very simplified schematic representation of the transfer case  20  and of the control unit  30  connected thereto. 
     The transfer case  20  includes a transfer case unit  34  that allows a torque of the drive shaft  18  to be distributed selectively to the output shafts  36  that are connected to the respective differential unit  26  of the front axle  22  or of the rear axle  24 , respectively (see  FIG. 1 ). The selective distribution of the torque of the drive shaft  18  depends on the state of a friction clutch  38  of the transfer case unit  34 . For example, the driving torque is only transmitted to the rear axle  24  with an open friction clutch  38 . To transmit some of the driving torque to the front axle  22  as well, the friction clutch  38  is brought into engagement at least partially. In other words, the portion of the driving torque transmitted to the front axle  22  is a function of the degree of actuation of the friction clutch  38 . The precise actuation of the clutch  38  is thus of great significance to allow a precisely defined distribution of the driving torque to the axles  22 ,  24 . 
     It must be taken into account in this connection that each friction clutch  38  has production-induced properties. This likewise applies to a clutch actuator  40  that can selectively bring the friction clutch  38  into engagement (i.e., the friction clutch  38  and the clutch actuator  40  respond to a given control signal in a characteristic manner which differs from other friction clutches  38  or clutch actuators  40  basically of the same construction). These practically unavoidable differences originate, for example, in manufacture-induced production tolerances and/or in slight variations of the properties of the material used. 
     To ensure the desired distribution of the driving torque with the required precision, it is necessary to take the characteristics of each transfer case  20  into account individually and to adapt the control signals supplied to it accordingly. 
     This is effected in that the individual components of the transfer case  20  are measured individually or in total at the end of production (i.e., the response of the components or of the total transfer case  20  to specific control signals is observed and a special characteristic is determined). This is in particular characterized by the torque transmission characteristics of the friction clutch  38  and the behavior of the clutch actuator  40 . The specific characteristics are associated with one of a plurality of tolerance classes. The control signals for the transfer case  20  may be adapted with reference to the specific tolerance class—for instance by adaptation of maps/characteristics—to achieve a distribution of the driving torque which is as exact as possible. 
     The control signals of the control unit  30  are supplied to the clutch actuator  40  via an additional control unit  42  and via a control line  50 ′. The additional control unit  42  has an additional control unit memory  44  in which the tolerance class described above is stored. The control signals transmitted by the control unit  30  may be adapted in the additional control unit  42  while taking the tolerance class into account to be able to provide adapted control signals to the clutch actuator  40 . It is expedient, however, to make the additional control unit  42  as simple as possible and to carry out the correction of the control signals in the control unit  30 . For this purpose, the control unit  30  must be supplied with the corresponding tolerance class information. This is done by the additional control unit  42  reading out the tolerance class information from the additional control unit memory  44  and transmitting it to the control unit  30 . This information may be stored in a control unit memory  46  by a control unit  54 . 
     The information stored in the control unit memory  46  is used for the adaptation of characteristics  48  that are used for the generation of control signals for the transfer case  20 . The tolerance class information stored in the control unit memory  46  is subsequently again transmitted to the additional control unit  42  via the control line  50 , whereupon the memory content of the additional control unit memory  44  is checked by a test section  52 . If the additional control unit memory  44  already has a stored value, the value transmitted by the control unit  30  is ignored. If the additional control unit memory  44  is, however, empty or is flagged as “empty”, the transmitted information is written into the additional control unit memory  44 . The process subsequently starts again with the reading out and the transmission of the information stored in the additional control unit memory  44  to the control unit  30 . An exchange of information between the additional control unit  42  and the control unit  30  thus takes place at predetermined times, at regular intervals or in response to request signals. The exchange of data is in particular of importance after an initialization at the start of an ignition procedure of the vehicle. 
     If a tolerance class determined ex works (i.e., where the individual components are manufactured) was stored in the additional control unit memory  44 , the correct value is stored in the control unit memory  46  of the control unit  30  after a first transmission of this information. The value of the tolerance class transmitted back to the additional control unit  42 , therefore, agrees with the originally stored value. As described above, this tolerance class information is ignored since the additional control unit memory  44  already contains corresponding information. 
     If, however, the additional control unit  42  was removed and replaced by a new additional control unit  42 , the additional control unit memory  44  is empty or is flagged as “empty”. On a take-up of communication between the new additional control unit  42  and the control unit  30 , no information is transmitted from the additional control unit  42  to the control unit  30 . However, the correct tolerance class information of the friction clutch  38  and of the clutch actuator  40  is still contained in the control unit memory  46 . This information is transmitted in the course of the data loop described above to the additional control unit  42  where the test section  52  determines that the additional control unit memory  44  is empty. The value of the tolerance class information is thereupon stored in the additional control unit memory  44  and is thus again available to the data loop. 
     One of the advantages of the invention thus consists of the fact that, if the control unit  30  is replaced or is reset for another reason and the information in the control unit memory  46  is lost, the tolerance class information is still present in the additional control unit  42  and it can be utilized. In the converse case, the tolerance class information can be utilized in the control unit  30 . The concept in accordance with the disclosure with the storage of the tolerance class information both in the additional control unit  42  and in the control unit  30  is thus based on the principle of redundancy in order to always allow a precise control of the transfer case  20 . 
     The additional control unit  42  and the clutch actuator  40  frequently form one module and are replaced together in case of service. In this case, it is advantageous if the tolerance class information is composed of information with respect to the friction clutch  38  and information with respect to the clutch actuator  40 . A newly inserted module only comprises a piece of partial information with respect to the clutch actuator  40  in the case of replacement, whereas the part of the additional control unit memory  44  provided for the tolerance class information of the friction clutch  38  is empty or is flagged as “empty”. On a repeat initialization after the replacement of the module, only the tolerance class information of the clutch actuator  40  is overwritten in the control unit memory  46 . The tolerance class information of the friction clutch  38  is maintained and is transmitted to the additional control unit  42  where the test section  52  finds that no tolerance class information of the friction clutch  38  is present in the additional control unit memory  44 . This information is then written to the additional control unit memory  44 , whereby complete tolerance class information is again present there. 
     If the module of clutch actuator  40  and additional control unit  42  is replaced, a replacement module is frequently used that may not be equipped with an individually determined tolerance class value of the clutch actuator  40  since an individual determination of the tolerance class for each spare part is too costly. In this case, a tolerance class value of the clutch actuator  40  is stored in the additional control unit memory  44  that characterizes a typical or “average” clutch actuator  40 . 
     It is easy to see that the tolerance class information may include more than two pieces of partial information if a plurality of components cooperate to produce an adjustment movement or an actuation. 
     With particularly demanding applications, however, the additional effort and/or cost described above may be justified. Provision may also be made that it is not tolerance class information that is exchanged between the units  30  and  42 , but rather the characteristics of the respective components themselves. 
     The disclosure has been described by way of example with reference to a transfer case  20  of a motor vehicle that is characterized by tolerance class information; however, the principles of the disclosure may also be used in other systems of a motor vehicle. A series of applications also result outside automotive engineering in which the taking into account of individual features and characteristics of specific assemblies—or individual components thereof—is important. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the invention, and all such modifications are intended to be included within the scope of the invention.