Abstract:
The invention relates to a method for controlling a sensor system ( 10 ) for a vehicle ( 100 ), comprising at least one or two sensors ( 11, 12 ) which have respective detection regions ( 11   b,    12   b ) and metrologically detect changes in these detection regions ( 11   b,    12   b ) and emit them as measured signals ( 11   a,    12   a ), a control unit ( 15 ), especially in the form of a microprocessing unit which is connected to the sensors ( 11, 12 ), the control unit ( 15 ) evaluating the measured signals ( 11   a,    12   a ) and generating at least one control signal ( 16 ) based thereon, at least one memory ( 18 ) in which at least the last control signal ( 16 ) is stored, and an interface ( 19 ) via which the control unit ( 15 ) forwards at least the last control signal to an external control module ( 21 ). At least one measured signal ( 11   a,    12   a ) of a sensor ( 11,   12 ) is detected by the control unit ( 15 ) in a number of measurement steps ( 11.1 - 4, 12.1 - 4 ) and the control unit ( 15 ) transmits at least the last control signal ( 16 ) to the external control module ( 21 ) via the interface ( 19 ) between the individual measurement steps ( 11.1 - 4, 12.1 - 4 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a method for the control of a sensor system for a motor vehicle. Such a sensor system has at least two sensors which each comprise detection areas, detect changes in these detection areas using measuring, and relay measurement signals. In addition, the sensor system contains a control device, particularly in the form of a microprocessor which is connected to the sensors, wherein the control device evaluates each measurement signal and generates at least one control signal therefrom. In addition, the sensor system has at least one storage device in which at least the most recent control signal is saved. An interface is also included in the sensor system, wherein the control device uses the same to relay the most recent control signal to an external control module. 
       BRIEF DESCRIPTION OF RELATED ART 
       [0002]    Sensor systems of this type in a vehicle, particularly a motor vehicle, are frequently connected to an external control module in a communication system. These communication systems generally have a serial data transfer. In this case, a so-called local interconnect network (LIN bus) or a control area network (CAN bus) can be included in the vehicle. One problem with these communication systems is that they query the individual communication subscribers (in this case: sensor systems) on their status at chronologically arbitrary points, but only allow the subscribers a short period of time to answer with the answer signal. If the subscriber does not answer in time, an error message can be generated as a result, the same displaying to the external control module that the subscriber in question is producing errors or is defective. In any case, individual subscribers, such as the sensor system named above, for example, require sufficient time to be able to carry out a precise measurement. If the external control module requests an answer signal during this time, however, a time delay results which leads to an error or a failure because the sensor systems of this type cannot interrupt the measurement in progress. 
       BRIEF SUMMARY 
       [0003]    As such, the problem addressed by the present invention is that of providing a method for the control of a sensor system, as well as a corresponding sensor system, with high operational reliability. Queries of an external control module should be answered in a short time in order to prevent potential error messages. 
         [0004]    In the method according to the invention, at least one measurement signal of a sensor is detected by the control device in multiple measurement steps, and the control device transmits at least the most recent control signal between the individual measurement steps to the external control module via the interface. As a result, a measurement signal of a sensor is not detected by the control device in complete form, because the time is not sufficient for this to happen. Particularly, if the external control module should request an answer signal during the process by means of a request signal, then the control device is not able to answer this request signal of the external control module by means of an answer signal. The control device can particularly only detect a measurement signal of a sensor at the same time. As such, the control device is not able to simultaneously query multiple actuators, particularly in the form of the sensors or the interface or the like, and/or to detect the corresponding signal. By means of the division of the complete measurement signal of a sensor according to the invention into multiple smaller measurement steps, the duration of the individual measurement step is reduced, such that the control device is free for a new action after a measurement step is carried out. As such, it is ensured that the control device can also react sufficiently quickly to a request signal of the external control module, and [the control device] relays a corresponding answer signal via the interface to the external control module. This answer signal can comprise at least the most recent stored control signal which is saved in the storage device. As a result, it is possible to reliably prevent error messages and answers not replied to the external control module by means of the division of the time-consuming measurement signal detection. In this way, it is possible to significantly increase the operational reliability of the sensor system. The method according to the invention is also possible with one sensor system with only one sensor, and therefore is not limited to two or more sensors. Of course, the measurement signal of the single sensor must likewise be divided into multiple measurement steps. 
         [0005]    During the period of time between the ending of a previous measurement step and the start of the following measurement step, the control device can regularly query the interface for a request signal. If this request signal is not present, the control device detects the following measurement step in order to receive a complete measurement signal from at least one sensor. 
         [0006]    Likewise, each measurement signal of the sensors can be divided into single measurement steps which are detected by the control device. This division is particularly necessary in cases when the detection of the measurement signal is particularly time-consuming. However, if a sensor of the sensor system is able to provide a complete measurement signal to the control device in a short time, then such a division is not necessarily required. As such, in the present method, a decision can be made for each individual sensor as to the extent to which its measurement signal can and/or must be divided into individual measurement steps. 
         [0007]    Moreover, individual measurement steps of each sensor can always be detected in a pre-defined sequence by the control device, such that the control device queries the sensors in sequence. As such, it is possible to simply adapt the sensor system to the widely varying sensors and applications in the vehicular field. However, in order to keep the storage requirement of the sensor system as low as possible, it is reasonable to first query the individual measurement steps for one measurement signal (of one sensor) in the sequence, until this signal is complete. The result of the measurement signal can then be temporarily saved in a storage device. Next, the control device can begin with the detection of the next measurement signal from a further sensor if there is no request signal from an external control module by that point. 
         [0008]    In order to make it possible to undertake a precise detection of the complete measurement signal of a sensor, a measurement step (of the sensor) can be ended at a defined point in the measurement signal, and particularly the evaluation and/or detection of the measurement signal can be continued at this defined point with the following measurement step (of the sensor). As such, by means of the predefined interruption of the detection of the measurement signal at a defined point, it is possible to reliably prevent measurement errors during the detection of the measurement signal. In addition, the complete measurement signal of a sensor can therefore be divided into nearly any number of measurement steps, because the division only depends on where the defined points for interrupting the measurement signal are provided. 
         [0009]    In order to ensure in all cases that the external control module always obtains an answer signal promptly, the time span for a measurement step can be smaller than a prespecified answer time span from the external control module. In this case, the control device can also check, after one and/or after each measurement step, whether a request signal of the external control module for an answer signal is present at the interface. Because the answer time span is always larger than the time span for the individual measurement step, the measurement step is therefore always ended prior to the closing of the answer time span. As such, the control device has sufficient time to query the interface for a requested answer signal and/or request signal. 
         [0010]    In order to simplify the process flow in the method according to the invention to the greatest extent possible, it can be contemplated that the time spans of the measurement steps for all sensors are designed to be the same length. The time span of the measurement steps can be between 2 and 20 times smaller than the entire span of time required for the detection of a complete measurement signal, for example. However, in order that there are not too many measurement steps for one measurement signal, the time span should not be, for example, smaller than a fifth of the prespecified answer time span for the external control module. Otherwise, it will be difficult to detect the complete measurement signal in a reasonable time span, because the control device is too highly occupied to jump back and forth between the individual actuators. As a result of this jumping back and forth, a certain amount of time is lost and this adds up significantly with so much switching. This can have disadvantageous effects. 
         [0011]    In the method according to the invention, the control device can also always only query and/or detect one actuator at any one time, particularly in the form of the sensors or of the interface. If one would like to query multiple sensors at the same time, then more microprocessors must be provided for the control device, and the price of the sensor system climbs significantly, and the process flow is then designed as over-proportionately complicated. It is also difficult to re-program the control device with its microprocessors because not only must the vehicle specifics and/or the specifications of the external control module be taken into account, but the circuit structure of the sensor system must be as well. So that an exchange of data does not only take place unilaterally from the sensor system to the external control module via the interface, a bidirectional data exchange, particularly a serial data transmission, can occur via the interface with the external control module. Of course, a parallel data transmission can also be contemplated; however, more data lines are required for this purpose between the sensor system and the external control module. In the event that it is desirable to keep the wiring complexity in the vehicle as low as possible, it is reasonable to choose a serial data transmission. 
         [0012]    In the method according to the invention, the interface of the control device can also relay the control signal as an answer signal to a communication system, particularly a serial communication system, particularly a so-called local interconnect network (LIN bus) or a controller area network (CAN bus). Both of these bus systems (LIN and CAN bus systems) have established themselves as a de facto standard in motor vehicle electronics. They are characterized by their simple and stable construction which enables a reliable transmission of data between the individual communication subscribers. 
         [0013]    The present invention also relates to a sensor system for a vehicle. In this sensor system, the method according to the invention is executed in the control device. In this case, the control device can optionally have exactly one microprocessor. By means of the use of only one microprocessor, the sensor system can be deployed in a cost-effective but also highly flexible manner. 
         [0014]    In the present sensor system, the sensors can be designed as touchless sensors which are particularly designed as capacitive sensors. With these capacitive sensors particularly, a rapid signal detection is not possible, or is only slightly possible, because the available capacitance of each capacitive sensor must be detected by measurement and relayed further as a measurement signal to the control device. It can likewise be contemplated that more than two sensors are used. These can include all capacitive sensors, wherein other sensor types can be contemplated, including piezo sensors, ultrasound sensors, switch elements, or the like, for example. In the context of the present invention, it does not matter whether the first sensor is attached to the vehicle below the second sensor, or not. As such, in the present embodiment, the first sensor can be interchanged with the second sensor. 
         [0015]    The touchless sensors can be capacitive sensors or ultrasound sensors. Other proximity sensors can also likewise be used. Capacitive sensors can also be advantageously used, because these can be arranged behind a panel securely and in a protected manner, and need not be in direct contact with the environment of the vehicle. 
         [0016]    By means of the present sensor system, it is possible to realize a virtual switch, for example for the actuation of a moving part, particularly in the form of a trunk hatch, a side door or sliding door in a motor vehicle. 
         [0017]    Features and details which are described in association with the method according to the invention naturally apply in the context of the sensor system according to the invention, and vice versa. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    Further measures and features which improve the invention are described in greater detail below within the description of preferred embodiments of the invention, with reference to the figures, wherein: 
           [0019]      FIG. 1  shows an embodiment of the sensor system according to the invention for the touchless actuation of a trunk hatch on a vehicle, 
           [0020]      FIG. 2  shows a concrete embodiment for the actuation of the sensor system by a leg or a foot of a person, 
           [0021]      FIG. 3  shows a schematic top view of the arrangement of two sensors of the sensor system inside a rear bumper of a vehicle 
           [0022]      FIG. 4  shows a schematic illustration of the sensor system according to the invention, along with the connection to the external control module, 
           [0023]      FIG. 5  shows a schematic illustration of the division of a complete measurement signal of the first sensor into multiple measurement steps, in a chronological diagram, 
           [0024]      FIG. 6  shows a chronological process diagram for the individual measurement signals of the sensors, without a request signal of the external control module, 
           [0025]      FIG. 7  shows a comparable process diagram to that in  FIG. 7 , but with a request signal of the external control module, 
           [0026]      FIG. 8  shows a comparable process diagram to that in  FIG. 6 , wherein the individual measurement steps of the sensors are detected in sequence, without a request signal of the external control module being present, and 
           [0027]      FIG. 9  shows a comparable process diagram to that in  FIG. 8 , having a request signal between the detection of the first measurement signal. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]      FIG. 1  shows an embodiment of the sensor system  10  according to the invention, for example for the touchless actuation of a trunk hatch  101  as the moving part  101  of a vehicle  100 , the same constituting a motor vehicle. The moving part  101  is held in the closed position and secured by an electromechanical lock  103 . The sensor system  10  has a first sensor  11  for the detection of an object  80  in a first detection area  11   b,  and a second sensor  12  for the detection of an object  80  in a second detection area  12   b.  The sensors  11  and  12  are designed as capacitive sensors  11  and  12 , and are only indicated schematically in the view. The detection area  11   b  covers the horizontal area behind the rear bumper  102  of the vehicle  100 . In contrast, the detection area  12   b  covers the lower area beneath the rear bumper  102 . As such, a first detection area  11   b  and a second detection area  12   b  are created which are geometrically separate from each other, for example, and do not include a common area on the external side of the rear bumper  16 . Of course, in principle, the detection areas  11   b,    12   b  can also particularly overlap. The detection areas  11   b  and  12   b  are indicated in the figures by rays, but these only indicate areas in which a change in the dielectric constant between the capacitive sensors  11  and  12  and describe the environment of the rear bumper  102 . This change in the dielectric constant results in a change in the storable charge on the electrodes of the capacitive sensors  11  and  12 , which can be detected by the sensor system  10 . As such, the presence of an object  80 , particularly the presence of body parts  80 . 1 ,  80 . 2  of a person, can be provided by the capacitive sensors  11  and  12  with minimal current consumption. 
         [0029]    The directional means  11 . 6  and  12 . 6  extend behind the capacitive sensors  11  and  12 , and are designed in the form of metallic shields  11 . 6 ,  12 . 6 . These enclose the capacitive sensors  11 ,  12  as a curved or half-shell shape. The respective detection area  11   b  and  12   b  is prespecified by means of the shields  11 . 6  and  12 . 6 , which thereby enable an improved separation of the detection areas  11   b  and  12   b  from each other. The metallic shields  11 . 6  and  12 . 6  have the same electrical potential as the corresponding capacitive sensors  11  and  12 . As such, these are “active shields” in this case. Additional ground electrodes and/or ground shields can be included behind these “active shields”, and the detection areas  11   b,    12   b  of the capacitive sensors  11  and  12  can be directed in the opposite direction from the ground shields by means of the same—meaning away from the ground shields. The ground electrodes are typically connected directly to the vehicle ground via a ground contact. 
         [0030]    Of course, a side door or sliding door  101  can also be actuated by the sensor system  10 , instead of a trunk hatch  101 , wherein the sensor system [ 10 ] can serve as a virtual switch. In this case, both capacitive sensors  11 ,  12  are arranged in the region of the door frame, for example, and are oriented comparably to the bumper  102  in the trunk area  106  as above. Both of the capacitive sensors  11  and  12  can optionally also be arranged in the lower area of the side door, preferably below a stone guard. An approach of the object  80  toward the side door  101  can be detected by the first capacitive sensor  11  or by a proximity sensor for an access control system, which is generally arranged in the door handle. 
         [0031]    A side view of a cutaway section of the rear bumper  102  and/or of the lower region of the side door  101  is shown in  FIG. 2 , wherein the capacitive sensors  11 ,  12  are inserted in the same with their respective shields  11 . 6 ,  12 . 6 . According to the illustration, a leg  80 . 1  of a person is partially shown, and projects into the first detection area  11   b,  the same running horizontally. In contrast, the foot  80 . 2  connected to the leg  80 . 1  projects into the detection area  12   b  which extends vertically beneath the rear bumper  102  and/or beneath the door frame area. The person  80  has approached the vehicle  100  in the region of the rear bumper  102  and/or the side door. As a result, the first capacitive sensor  11  can detect the proximity of the person  80  by means of the penetration of the leg  80 . 1  into the first detection area  11   b.  If the person signals the intention to actuate the moving part  101 , by means of a back-and-forth movement of the foot  80 . 2  in the second detection area  12   b,  then a prespecified movement pattern  60  is created for the person. By means of the coupled detection of both the leg  80 . 1  and the foot  80 . 2 , the actuation of the trunk hatch  101  and/or the side door  101  is initiated. The corresponding detection area  11   b,    12   b  can be illuminated by means of an illumination and/or display means, the same not illustrated. The state of the moving part  101  on the sidewalk or the street next to the vehicle can also be displayed by a lettering. Upon the actuation, the electromechanical lock  103  is displaced in such a manner that it releases the moving part  101 , whereby it can be changed over from a locked position into an open position. The opening and/or closing process can itself be performed mechanically by the adjusting mechanism  104  indicated in  FIG. 1 , the same likewise being activated by the actuation of the virtual switch and/or being detected by the sensor system  10 . 
         [0032]      FIG. 3  shows a top view of the arrangement of the sensors  11  and  12  inside the rear bumper  102  of the vehicle  100 . The rear bumper  102  extends over the entire area of the vehicle hatch  105  of the vehicle  100 , wherein the bumper  102  is shown in its entire width. According to the illustration, it can be seen that the sensors  11  and  12  can extend approximately over the entire width of the bumper  102 . As a result, a person  80  can approach any position along the entire region of the hatch  105  of the vehicle  100 , and execute the movement of the leg  80 . 1  as well as the foot  80 . 2  described in  FIG. 2 . 
         [0033]    The illustration shows the arrangement of the first capacitive sensor  11  in the horizontal region of the bumper  102 , whereas the second capacitive sensor  12  is indicated, along with the shield  12 . 6  which encloses the same, in the lower region of the bumper  102 . The capacitive sensors  12  can be inserted or laid in the form of films or conductors into the bumper  102  along the width thereof. The capacitive sensors  11  and  12  are arranged along with their respective shields  11 . 6   12 . 6  inside the bumper  102 . 
         [0034]    The sensor system  10  for the vehicle  100  is schematically illustrated in  FIG. 4 . In this case, both sensors  11 ,  12  are generally not arranged in the housing  10 . 1  for the sensor system  10  because they generally monitor the outer area of the vehicle  100 . As such, each detection area  11   b,    12   b  is oriented toward the outer area of the vehicle  100 . In this case, the detection areas  11   b,    12   b  can partially overlap or can be separate from each other. The control device  15  is connected to the sensor circuitry  13 ,  14  for the sensors  11 ,  12  inside the housing  10 . 1  of the sensor system. Both of the sensors  11 ,  12  can be connected to the control device  15  and/or the sensor circuitry  13 ,  14  by conductors or via a wireless connection. The sensor system  10  itself is supplied with electrical energy via the voltage supply  20  from the vehicle  100 . In order to enable data communication between the sensor system  10  according to the invention and the external control module  21 , the communication system  23  is included and is particularly designed as a LIN or CAN data bus. At this point it is hereby noted that further sensor systems  10  or external control modules  21  can of course be connected to the communication system  23 . The answer signal  17 , which comprises at least the most recent control signal  16 , is relayed via the communication system  23 . This last control signal  16  is saved in the storage device  18  provided for this purpose, and is passed on to the communication system  23  via the interface  19 . In addition, the method according to the invention is saved in the sensor system  10  in order to improve operational reliability. 
         [0035]    A chronological process diagram for the detection of the first measurement signal  11   a  by the sensor  11  is illustrated in an exemplary manner in  FIG. 5 . In this case, the first measurement signal  11   a  is dissected into a total of four individual measurement steps  11 . 1 - 4  which are carried out directly or indirectly (with short intermediate periods) chronologically one after the other. In this case, the complete measurement signal  11   a  is interrupted at predefined points  22  in order to end the measurement step  11 . 2 , for example. The subsequent measurement step  11 . 3  then starts at the pre-specified point  22  at which the measurement of the measurement signal  11   a  is continued, until the next predefined point  22  follows. The measurement step  11 . 3  is ended by this next point  22 . The complete measurement signal detection ends in the last measurement step  11 . 4 , such that the complete measurement signal  11   a  is present at the control device  15 .  FIG. 5  only serves to explain how a measurement signal  11   a  is divided into individual measurement steps  11 . 1 - 4 . Of course, fewer or more measurement steps can also be carried out in this case. The time span  11 . 5  of a measurement step  11 . 1  must be reasonably chosen as smaller than a time span  17 . 1  of the answer signal  17  for the external control module  21 . This is clarified in greater detail in  FIGS. 7 and 9 . 
         [0036]    A chronological process diagram for the two sensors  11 ,  12 , as well as a possible answer signal  17 , are illustrated in  FIG. 6 . In any case, no request signal is present from the external control module  21 , such that the control device  15  in fact does not need to transmit an answer signal  17 . As can also be seen in  FIG. 6 , both measurement signals  11   a,    12   a  are divided into multiple measurement steps  11 . 1 - 4 ,  12 . 1 - 4 . After the first measurement step  11 . 1  has been detected by the control device  15 , the next measurement step  12 . 1  of the following sensor  12  is detected. As such, the measurement steps of the individual sensors  11 ,  12  are queried in alternation by the control device  15 . During the intermediate time period between the ending of the measurement step  11 . 1  and the start of the measurement step  12 . 1 , the control device  15  queries the interface  19  for a request signal. If this request signal is not present, then the control device  15  detects the following measurement step. 
         [0037]    In contrast to  FIG. 6 , an alternating query process of the measurement steps by the sensors  11 ,  12  is illustrated in  FIG. 7 ; in any case, a request signal, for example, is present in this case at time point t 0  during the first measurement step  11 . 1 . Following the end of this measurement step  11 . 1 , the control device  15  then queries the interface  19  for a request signal in the intermediate time period. Because the request signal is present, the control device  15  immediately transmits the answer signal  17  via the interface  19  to the external module  21 . The external module  21  allows the sensor system  10  the time span  17 . 1  for the answer signal  17 . This time span  17 . 1  starts with the transmission of the request signal to the sensor system  10 . As is clearly recognizable in  FIG. 7 , the further measurement steps  11 . 2 - 4 ,  12 . 1 - 4  are delayed by the sensors  11 ,  12  until the answer signal  17  has been sent to the external control module  21 . 
         [0038]    A variant of the process flow in  FIG. 6  is illustrated in  FIG. 8 . In this case, the individual measurement steps  11 . 1 - 4 ,  12 . 1 - 4  are not queried in alternation by sensor  11  to sensor  12 ; rather, the measurement signal  11   a  is detected in sequence by means of the measurement steps  11 . 1 - 4 . Only once the measurement signal  11   a  is present in its entirety does the control device  15  begin to detect the measurement signal  12   a  of the further sensor  12  by means of the individual measurement steps  12 . 1 - 4 . In FIG.  8 —just as in FIG.  6 —there is no request signal present from the external control module  21 . 
         [0039]    In contrast to  FIG. 8 , the external control module  21  transmits a request signal during the first measurement step  11 . 1  to the sensor system  10 , particularly to the interface  19 . As in  FIG. 7  as well, the control device  15  detects this request signal from the interface  19 , the same having been transmitted by the external control module  21  at time point t 0 , but only actually detects the same after the ending of the first measurement step  11 . 1  by the control device  15 . The control device [ 15 ] then transmits the answer signal  17  to the external control module  21  via the interface, and particularly within the allowed time span  17 . 1 . Because the time span  17 . 1  is larger than the individual time spans  11 . 5 ,  12 . 5  of the measurement steps  11 . 1 - 4 ,  12 . 1 - 4 , as in  FIG. 9  as well, it is ensured that the external control module  21  receives an answer signal  17  sufficiently quickly in every case. In this case, it should be clearly noted once again that the answer signal  17  has at least the most recent saved control signal  16  which was present at the control device  15 . As can further be seen in  FIG. 9 , the further measurement steps  11 . 2 - 4  of the first sensor  11 , as well as the following measurement steps  12 . 1 - 4  from the second sensor  12  are delayed as a result of the first transmitted answer signal  17 . Subsequently, the method according to the invention can be restarted, wherein a new control signal  16  is generated from the most recent complete measurement signal  11   a,    12   a,  and the new control signal [ 16 ] can be saved in the storage device  18 . 
         [0040]    Finally, it is hereby noted once again that multiple sensors can also be incorporated in the sensor system  10  by means of the method according to the invention. The individual time spans  11 . 5 ,  12 . 5  of the measurement steps can also vary, wherein it is nevertheless reasonable for these to not exceed the time span of the answer signal  17 .