Abstract:
The present invention relates to an actuator device for use in a motor vehicle, comprising an actuator, a control unit for controlling the actuator and a processing unit, which is or can be connected to an external main control device via a control connection in order to transfer actuator setting commands. Furthermore, the processing unit is subordinate to the main control device and is connected to the control unit in order to control the actuator according to the actuator setting commands. The control unit is or can be connected to the main control device via an activation connection and is equipped so as to enable the actuator to be controlled by the processing unit according to activation signals transmitted via the activation connection.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage of International Application No. PCT/EP2008/010540 filed Dec. 11, 2008, the disclosures of which are incorporated herein by reference, and which claimed priority to German Patent Application No. 10 2007 059 687.3 filed Dec. 12, 2007, the disclosures of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to an actuator device with a processing unit for use in a motor vehicle, which comprises a main control device. The processing unit is subordinate to the main control device. 
     “Intelligent” actuators are frequently used in modern motor vehicles. They usually incorporate a processing unit which is subordinate to a main control device, which in turn transmits control commands, for example actuator setting commands, to the processing unit. The processing unit receives the control commands from the main control device and is provided to control the actuator according to the commands transmitted from the main control device. This main control device operates as a master unit and the processing unit functions as the slave unit. Such a concept is described, for example, in the document WO 2006/061238, and corresponding US patent No. 2008/105502 A1, the US document being incorporated by reference herein, and enables power electronics for activating the actuator to be arranged so that it is spatially separate from the main control device. The communication between the main control device and the processing unit normally takes place via a data bus. In motor vehicles, such a bus is frequently a LIN bus, a CAN bus or a FlexRay bus. 
     Intelligent actuators of this type may be used in motor vehicles in particular for safety-related systems such as electronically controllable parking brake systems. Problems may occur, however, if incorrect signals are transmitted via the bus or if the actuator receives, for example via a short circuit, erroneous signals. If safety-related systems are affected by a fault of this kind, there could be serious consequences for the vehicle safety. For example, in the case of a parking brake, an incorrect signal may cause the parking brake to be released without control on a slope, or may lead to unexpected and undesired braking while the vehicle is travelling. Both situations may significantly prejudice the safety of the driver and passengers of a motor vehicle and that of other road users. 
     A safety concept that counteracts faults of this kind can usually only be implemented at great expense. The need therefore exists for a simple, cost-effective yet reliable system for increasing vehicle safety. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention proposes for this purpose an actuator device for use in motor vehicles, which comprises an actuator, a control unit to control the actuator, and a processing unit. The processing unit is or can be connected to an external main control device via a control connection and is subordinate to the main control device. In particular, provision may be made whereby the main control device and the processing unit have a master-slave relationship. The control connection is able to transmit actuator setting commands. The processing unit is furthermore connected to the control unit in order to control the actuator according to the actuator setting commands. In addition, provision is made whereby the control unit is or can be connected with the main control device via an activation connection. The control unit is equipped so as to enable the actuator to be controlled by the processing unit according to activation signals transmitted via the activation connection. The activation control may be run in parallel to the control connection. The activation connection between the control unit and the main control device enables an independent entity to be created via which it can be determined whether or not control of the actuator is to be permitted via the processing unit. A considerable improvement in safety for the actuator device may thus be achieved in a manner that is easy to set up. 
     The actuator device may have a monitoring unit via which the main control device is connected to the control unit by the activation connection. Such a monitoring unit connected in the activation connection between the control unit and the main control unit may carry out an additional check on signals transmitted via the activation connection. In particular, provision may be made whereby the monitoring unit is connected to the processing unit for signal transmission. This enables communication to be established between the monitoring unit and processing unit. It is advantageous if the monitoring unit is configured to detect faults occurring during the activation connection or the control connection and to forward an error message or deactivate the actuator device, or both. 
     In a further development the actuator device is connected to two separately operable control components of the main control device. In this case the control unit may be connected via the activation connection to a first control component and the processing unit may be connected via the control connection to a second control component. The connection to separately operable components of the main control device increases the system redundancy and the communication via the activation connection may be carried out separately and independently of the communication via the control connection. 
     An advantageous implementation makes provision whereby the control unit is or can be connected to the main control device directly via the activation connection. A direct connection of this type may also be provided alternatively to or in addition to indirect connections, for example via a monitoring unit where one is available. 
     The control connection for connecting the processing unit to the main control device may be a data bus. In particular, provision may be made for the data bus to be a LIN bus, a CAN bus or a FlexRay bus. Via a bus of this type, as is frequently used in vehicle technology, it is possible for signals to be transferred in a simple and well defined way. 
     It is possible for the main control device to be connected to the processing unit via the activation connection in parallel to and separately from the control connection. In this way an additional redundancy level may be provided for communication between the main control device and the processing unit. 
     According to one variant, the activation connection is able to transfer actuator setting commands or signals corresponding to actuator setting commands from the main control device. In this case provision may be made in particular whereby signals transferred via the activation connection are encoded (for example by modulation of the voltage level, pulse width modulation or frequency modulation). In this way, in addition to pure activation signals which generally allow or do not allow (i.e. block) control, it is possible for further commands to be transferred to the control unit and/or monitoring or processing unit. 
     Provision may furthermore be made whereby the processing unit and/or the monitoring unit is able to compare signals or actuator setting commands transferred from the main control device via the activation connection with actuator setting commands transferred from the main control device via the control connection. The signals used for the comparison may be transferred to the monitoring unit or to the processing unit via the activation connection. If signals transferred to the monitoring unit are to be compared, provision is made whereby a signal transmission may take place between the monitoring unit and the processing unit. 
     The processing unit may be adapted to control the actuator only when the signals or actuator setting commands compared to each other correspond. In addition to or alternatively to this, it is possible for the monitoring unit to carry out the comparison or to receive a signal corresponding to the comparison carried out by the processing unit. If appropriate, the monitoring unit—on the basis of the signal received or comparison carried out—may refrain from forwarding an activation signal or corresponding signal to the control unit or may send an express blocking command to the control unit. 
     According to a further development the processing unit, the monitoring unit and the control unit are all connected to the main control device via the activation connection. This results in an extremely high level of redundancy of signal transmission via the activation connection between the main control device and the units of the actuator device connected to it. 
     The activation line may also be adapted to provide power to units connected to it such as monitoring unit, processing unit and control unit. 
     The proposed actuator device is particularly suitable to be used with an actuator to activate a vehicle parking brake. However, a multitude of other applications are possible in which intelligent actuators as described here may be used, for example airbag systems, seat-belt pretensioners or similar. 
     The invention also comprises an actuator system, which comprises a main control device and at least one actuator device as described above. In particular, this may be a vehicle parking brake system comprising one or more actuator devices of a vehicle parking brake. 
     It is particularly useful if signals that are compared to each other must be present within a predefined time window so that they can actually be deemed to correspond to one another. It is also advantageous if the activation signals present on the control device permit control by the processing unit only within a predefined time window. Different time windows may be provided for various signal comparisons. The length of these time windows should be tailored precisely to the embodiment of the actuator device used and to the purpose for which it is used. 
     The invention further covers a method for controlling an actuator device for use in a motor vehicle. In this method provision is made whereby a subordinate processing unit receives actuator setting commands which are transmitted via a control connection from a superordinate main control device. A control unit receives activation signals which are transmitted from the main control device via an activation connection. The processing unit further transmits control commands to the control unit on the basis of the actuator setting commands, and the control unit controls an actuator on the basis of control commands received according to received activation signals. 
     The method may also make provision whereby actuator setting commands or signals corresponding to actuator setting commands are transmitted via the activation connection by the main control device to the processing unit. Actuator setting commands or signals corresponding to actuator setting commands may furthermore be transmitted, via the activation connection, by the main control device to a monitoring unit connected to the main control device via the activation connection. 
     Furthermore, provision may be made whereby the actuator setting commands or signals corresponding to actuator setting commands transmitted via the activation connection are compared with actuator setting commands transmitted via the control connection by the processing unit and/or the monitoring unit, wherein the control of the actuator is performed or permitted only if the compared actuator setting commands or signals correspond to each other. 
     Other advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of an embodiment of an actuator device. 
         FIG. 2  is a flow chart showing an embodiment of a method for controlling an actuator. 
         FIG. 3  shows a possible coding of signals transmitted via the activation connection. 
         FIG. 4  is a detailed schematic view of a further embodiment of an actuator device which may be used in a motor vehicle-parking brake. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Within this description a connection means a device for signal transmission or for transmission of electrical voltage or electrical power unless otherwise expressly mentioned. In particular, such a connection may comprise one or more electrical cables. Furthermore, when reference is made below to the transmission of signals or of actuator setting commands, this always means the transmission of one or more signals or actuator setting commands. 
       FIG. 1  is a schematic view of an actuator device  10 . The actuator device  10  has a monitoring unit  14 , a processing unit  16  and a control unit  18 . The control unit  18  is connected to an actuator  19  for the purpose of control. The actuator  19  may, for example, comprise a motor for releasing or activating a parking brake. 
     A connection  20  is provided between the monitoring unit  14  and the control unit  18 . The control unit  18  is further connected to the processing unit  16  via a connection  22 . The processing unit  16  and the monitoring unit  14  are able to communicate with each other via a connection  24 . A voltage source  30   a  is provided to supply the actuator  19  with operating voltage. A vehicle battery (not shown), for example, may be used as voltage source  30   a.    
     The actuator device  10  is provided for connection to a main control device  12 . The main control device  12  may, for example, be a microprocessor of an on-board computer of a vehicle. The main control device  12  is preferably subdivided into two separately operable components  12   a  and  12   b.    
     According to  FIG. 1  the component  12   b  of the main control device  12  is connected to the processing unit  16  via a data bus  26  constituting a control connection. This data bus  26  is designed, for example, as a standardized data bus for data transmission in vehicles, such as—for example—a CAN bus, a LIN bus or a FlexRay bus. The main control device  12  is superordinate to the processing unit  16 , and the main control device  12  and its components  12   b  and the processing unit  16  respectively form a master-slave pair. In a master-slave relationship of this kind, provision is made whereby the main control device  12  can control the access to the data bus  26 , and the processing unit  16  cannot have write access to the data bus  26  without, for example, access rights issued by the main control device  12 . 
     Furthermore, an activation line  28  is provided for connecting the components  12   a  of the main control device  12  to the actuator device  10 . As shown in  FIG. 1 , the activation line  28  has three branches  28   a ,  28   b  and  28   c . The component  12   b  of the main control device  12  is connected to the processing unit  16  via the branch  28   a , to the monitoring unit  14  via the branch  28   b  and to the control unit  18  via the branch  28   c . The activation line  28  is able to transmit analogue electrical signals with different signal levels. In particular, it is possible—by the signal level on the activation line  28 —to show signals that completely or partially correspond to specific or to all actuator setting commands. The connection  20 , as part of the activation connection  28 , connects the control unit  18  indirectly via the monitoring unit  14  to the main control device  12 . 
     A voltage source  30   b  is provided in order to supply electrical power to the main control device  12  and to its components  12   a ,  12   b . The voltage source  30   b  may be identical to the voltage source  30   a  or may be a different voltage source. 
     The connections  20 ,  22  and  28  are shown in  FIG. 1  such that the signals are transmitted in only one direction. However, it is of course possible for one, more than one or all of these connections to be configured so that signals may be transmitted in both directions. It is important, however, that a signal transmission is at least possible in the direction shown. For example, provision may be made whereby the control unit  18  may transmit data such as error signals to the monitoring unit  14  or to the processing unit  16 , or both. The monitoring unit  14  and/or the processing unit  16  may also be configured and connected so that error signals may be transmitted to further components such as the main control device  12 . 
     During operation provision is made whereby the component  12   b  of the main control device  12  transmit actuator setting commands to the processing unit  16  via the bus  26 . The processing unit  16  forwards these actuator setting commands as control commands to the control unit  18  via the connection  22 . In this way provision can be made whereby the processing unit  16  is able to convert or translate the actuator setting commands received from the main control device  12  or control component  12   b  into control commands that can be understood by the control unit  18  should this be necessary. It is also possible for control switches and power electronics elements to be used as the control unit  18 . The processing unit  16  may in turn transmit signals to the main control device  12  via the bus  26 . The monitoring unit  14  is able to participate in the control via the connection  20 . In particular, provision is made whereby the monitoring unit  14  is adapted so that, depending on the situation, an activation signal or a signal corresponding to an activation signal is forwarded to the control unit  18 , such a signal is not forwarded, or a blocking signal is sent to the control unit  18 . 
     Provision is made whereby control of the actuator  19  according to actuator setting commands is carried out only if a corresponding activation signal is transmitted via the activation line  28 . 
     In the actuator device  10  shown in  FIG. 1  an activation signal may be transmitted via the branches  28   a ,  28   b ,  28   c  of the activation line  28  to the processing unit  16 , the control unit  18  and the monitoring unit  14  respectively. This enables a check to be carried out in several places as to whether actuator setting commands transmitted via the data bus  26  have actually been correctly transmitted or even should have been transmitted at all. 
     One option for checking occurs directly at the processing unit  16 , which receives actuator setting commands via the data bus  26  and corresponding signals (either activation signals only, or signals corresponding to the actuator setting commands) via branch  28   a  of the activation line  28 . The processing unit  16  is able to determine whether the signals or actuator setting commands received via these two connections correspond to each other. In particular, provision may be made whereby the processing unit checks only whether an actuator setting command and a activation signal are present together. If signals that correspond to each other are present, the processing unit  16  transmits control commands to the control unit  18 . If, on the other hand, there is no correspondence between the signals, the processing unit  16  assumes that there is an error and refrains from forwarding the actuator setting commands. If an error is present the processing unit may transmit error reports, for example, to the main control device  12  or to a different unit or other component of the vehicle electronics. This takes place advantageously via the data bus  26 . 
     Furthermore, the monitoring unit  14  receives signals via branch  28   b  of the activation line  28 . The monitoring unit  14  may exchange data with the processing unit  16  via the connection  24 . This enables a check to be carried out as to whether the commands transmitted to the processing unit  16  correspond to the commands transmitted to the monitoring unit  14 . This means that either of the units  14 ,  16  may transmit data, via the connection  24 , to the other unit concerned, which then carries out the check. In particular, provision may be made whereby the monitoring unit  14  sends data to the processing unit  16 , which compares the signals received from the monitoring unit  14  with those that it has received itself. The comparison and/or checking for correspondence may take place on the basis of the activation signals received by the processing unit  16  or on the basis of the actuator setting commands, or both. 
     Provision may further be made whereby the monitoring unit  14  transmits signals to the control unit  18  via the line  20  on the basis of the result of comparison or check. If the compared signals correspond to one another, the monitoring unit  14  may forward the activation signals or signals corresponding to activation signals received by it to the control unit  18 . If there is no correspondence, the monitoring unit  14  refrains from forwarding the activation signals or transmits a blocking signal to the control unit  18 , whereupon the latter refrains from permitting the control of the actuator  19 . 
     Furthermore, activation signals are transmitted to the control unit  18  via branch  28   c  of the activation line  28 . The control unit  18  is adapted to control the actuator only according to the processing unit  16  if an activation signal is transmitted via the activation line  28   c  to the control unit  18 . 
       FIG. 2  is a basic schematic diagram showing a flow of a method for controlling an actuator of an actuator device. This may be an actuator device  10  as shown in  FIG. 1 . 
     In stage V 10  a processing unit receives actuator setting commands which a main control device transmits via a control connection. Provision may be made whereby the processing unit receives activation signals in stage V 15 , which are transmitted from the main control device via an activation connection. These stages V 10  and V 15  may take place simultaneously or with a slight time delay, in which case it is irrelevant which stage takes place first. The processing unit then checks, in stage V 17 , whether the activation signals and the actuator setting commands correspond, in particular whether the activation signals correspond to the transmitted actuator setting commands. If this is the case, the processing unit transmits control commands to a control unit in stage V 20  on the basis of the actuator setting commands received. Stages V 15  and V 17  are optional in this case. 
     In parallel to stages V 10  to V 20 , in stage A 10  the control unit receives activation signals which the main control device transmits via the activation line. 
     In stage A 20  the control unit checks whether activation signals received by it correspond to control commands transmitted to it. In particular, the control unit may check whether a received activation signal is present that permits any control, or whether it permits only a certain type of control and corresponds to the relevant control command of the type of control permitted by the activation signal. If the control unit ascertains that signals and control commands that correspond to each other are present, in stage A 30  control of the actuator is carried out by the control unit according to the control commands. A time lag between receipt of the respective signals and commands may be used as a benchmark for the correspondence of the signals and control commands. In particular, provision may be made whereby signals and commands correspond to each other only if they are present within a predefined time window. 
       FIG. 3  shows a possible coding of the signal level on the activation line, for example the activation line  28  shown in  FIG. 1 . It is assumed from this that the actuator may be opened and closed. Of course, end statuses other than open and closed—in particular non-binary end statuses—are possible for the actuator, for example such statuses that lead to a brake being applied and to a brake being released. In  FIG. 3 , voltage level ranges to which an activation function is assigned are shown cross-hatched, and those to which no particular activation function is assigned are left blank. Ranges within which no activation is possible are shown chequered. The breadth of the ranges in  FIG. 3  is selected merely for clarification purposes; the actual signal level ranges that are still assigned to a target value may be adapted to the requirements of a system. 
     The signal incorporates a possible voltage range from 0 to 12 V. At a signal level of 12V or above it is assumed that there is a short circuit in an activation line and the control unit is deactivated; controlling of the actuator according to a processing unit is not possible. 
     Control of the actuator is likewise not possible below a level of 5V (low signal status). The activation range is therefore between 5V and 12V in this example. As soon as the signal level rises above 5V (high signal level) but remains below 12V, control of the actuator is possible in principle. 
     In the signal level range within which control is possible, specific voltage values are assigned specific setting commands or setting command types in addition. For example, a signal level of 6V represents an activation signal for closing the actuator; if the activation line runs a level of 6V, the control unit permits control by the processing unit only in order to close the actuator. A signal level of 7V, on the other hand, represents an activation signal for opening the actuator. If such a level is present, the control unit controls the actuator only in order to open it; other control commands from the processing unit are not executed. It is possible, of course, for provision to be made in such a coding whereby a signal level that is within the control range but exceeds several voltage values, to which different control types are assigned, permits all these control types. In the example shown in  FIG. 3 , a voltage level between 7V and 12V would then permit both the closing and the opening of the actuator. Furthermore, provision may be made whereby a signal level is defined in which all available types of control are permitted. 
       FIG. 4  shows an actuator device  100  in greater detail. The actuator device  100  has a motor M which functions as an actuator. The motor M is connected in the conventional manner via an H-bridge circuit  105  to two power transistors  110  on the upper surface and two power transistors  120  on the lower surface respectively (the bridge circuit is not shown in detail). The power transistors  110  and  120  are designed as field-effect transistors and are provided for actuation of the motor M. The power transistors  110  are connected to a positive pole  135   a  of a voltage source via a cable  130  in order to supply electricity to the power transistors, and to a fuse  140  of the vehicle, usually the K30 fuse. A diode array  150 , which suppresses return power flow from the power transistors  110 ,  120  to the fuse  140 , is connected between the fuse  140  and the power transistors  110 . A current measuring device  170  is connected to the power transistors  120  via a cable  160 . Furthermore, the current measuring device  170  is earthed via a cable  180   a.    
     A cable  190  is connected for linking the current measuring device  170  to a processing unit  200 . In this embodiment the processing unit  200  is a Freescale S08 microcontroller, which is not shown in full detail in  FIG. 4 . Other suitable microcontrollers may also be used as the processing unit  200 ; the precise number and type of connections and elements present in the microcontroller will then be different from the unit shown here. 
     The processing unit  200  incorporates an analogue-digital converter (ADC)  210 , which is connected to the current measuring device  170  via the cable  190  for transmission of power measurement data. The analogue-digital converter  210  is furthermore connected to the bridge circuit  105  via two cables  220   a ,  220   b . The signals relating to the actuator setting can be routed to the ADC  210  via the cables  220   a ,  220   b.    
     An external temperature measuring device  235  is further connected to the ADC  210  via a cable  230 . The ADC  210  is also connected via a cable  240  to an internal temperature measuring device  245  for measuring the temperature of the processing unit  200 . A cable  250  connects the ADC  210  to a positive voltage pole  135   b , which provides a voltage setting. The ADC  210  is furthermore connected to an external main control device  400  (not shown in greater detail) via a branch  270   a  of an activation line  270 . The cables  280   a  and  280   b  represent a connection from the processing unit  200  to the main control device  400  via a CAN bus. A cable  180   b  provides an earth connection for the processing unit  200 . Furthermore, the processing unit  200  incorporates a voltage regulator  285  which, on the basis of signals routed to the ADC  210  via the cables  220   a ,  220   b ,  270   a ,  230 ,  235 ,  240 ,  190 , and on the basis of actuator setting commands transferred via the CAN bus  280   a  and  280   b , outputs control commands for the motor M via a cable  290 . 
     A monitoring unit  300  is connected to the processing unit  200  via cables  310 . In the embodiment shown here the monitoring unit is an ATMEL ATA6823 unit which is connected in the conventional way via cables  310  to the Freescale S08 microcontroller, i.e. the processing unit  200 . Here, likewise, it is of course possible for another suitable electronic component to be used as the monitoring unit  300 . The details of the monitoring unit  300  will vary accordingly. The exact nature of the connection between the monitoring unit  300  and the processing unit  200  will depend in particular upon the components that are used as the processing unit  200  and monitoring unit  300 . 
     In the constellation shown in  FIG. 4 , the cables  310  in the diagram comprise, from left to right, a cable for positive supply voltage (VCC), 3 status cables and 3 control cables, as well as a monitoring cable (WD) and a reset cable. The monitoring unit  300  is connected to positive voltage poles  135   c ,  135   d  by cables  320   a ,  320   b . An earth cable  180   c  connects the monitoring unit  300  to earth. A Schmitt trigger circuit  330  is connected to the main control device  400  via a branch  270   b  of the activation line  270 . The monitoring unit  300  is provided inter alia with a supply voltage via the branch  270   b . A diode  275  is provided in the branch  270   b  to prevent return power flow. The monitoring unit  300  is connected via two cables  340   a ,  340   b  with resistors  345   a ,  345   b  for control of the upper power transistors  110  of the bridge circuit  105 . In addition, the monitoring unit  300  is connected via cables  350   a ,  350   b  with resistors  355   a ,  355   b  to the lower power transistors  120  of the bridge circuit  105 . 
     The activation line  270  also has a further branch  270   c , in which a voltage divider  272  is installed. The branch  270   c  is connected to a control circuit  410 . The control circuit  410  comprises transistors  415 ,  420 ,  425  and  430 , which are connected to earth via cables  435   a ,  435   b ,  435   c  and  435   d  respectively. Furthermore, the control circuit  410  has a resistor  440  with a positive voltage pole  135   e . The control circuit  410  is additionally connected to the processing unit  200  via the cable  290  and to the lower power transistors  120  for control via the cables  450   a ,  450   b.    
     The branch  270   c  of the activation line  270  is connected to the control circuit  410  such that the transistor  415  is switched through only if a suitable activation signal is present on the activation line. The transistors  415 ,  420 ,  425 ,  430  are switched together so that the processing unit  200  can then activate the bridge circuit  105  and control the motor M via the cables  290  and  450   a  or  450   b.    
     In accordance with the provisions of the patent statutes, the principal and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.