Patent Publication Number: US-2021188098-A1

Title: System for an electrically driven vehicle, vehicle having same and method for same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Phase Application under 35 U.S.C. § 371 of International Application No. PCT/EP2019/062128, filed on May 13, 2019, and claims benefit to German Patent Application No. DE 10 2018 111 682.9, filed on May 15, 2018. The International Application was published in German on November 21, 2019, as WO 2019/219558 A1 under PCT Article 21(2). 
    
    
     FIELD 
     The invention relates to the domain of vehicles that are electrically or hybrid driven. In particular, such vehicles include utility vehicles such as trucks, passenger cars or trailer vehicles. 
     BACKGROUND 
     Electrically powered vehicles, especially in the commercial vehicle sector, with an internal combustion engine as the drive have long been known. Such vehicles have often been further developed into hybrid vehicles or the internal combustion engine has been substantially replaced by an electric drive during further development. This means that often no completely new development has been carried out for the provision of electrically driven vehicles, so that existing functions which are primarily not related to the drive itself can continue to be used. 
     In the case of known vehicles, in particular utility vehicles which are electric, it is therefore provided that the electric drive is used in essence in order to enable or support a positive acceleration of the vehicle. Such vehicles usually have a vehicle control unit. The vehicle control unit is connected to an electric motor control unit via a bus connection and passes an acceleration request via this, which is specified, for example, by a gas pedal position by a driver, to the electric motor control unit. This then switches on the electric drive to provide torque by the electric motors or to support the torque provision according to the specifications of the vehicle control unit. 
     In addition, an electronically controlled brake system (EBS) of the vehicle is controlled by the vehicle control unit. For this purpose, the brake system, which can also be referred to as a brake control unit, will be sent a signal with a negative acceleration request, i.e. a requested braking, and this signal will be implemented by the friction brakes which are controlled by the brake control unit. A signal with a negative acceleration request is generated, for example, in the vehicle control unit, when braking is requested by a driver via a brake pedal position. 
     In addition, it is known that in the case of an existing electric drive for supporting braking the vehicle control unit also signals the braking request to the electric motor control unit in order to support braking by an electromagnetic braking operation of the electric drive. This allows electrical energy to be generated with recovered kinetic energy during the braking maneuver which is carried out with the electric drive. 
     According to the prior art, rapid acceleration changes or torque changes, which are necessary for example in the case of slip control or stability control, are carried out by the electronically controlled brake system itself and only the friction brakes are used here. In particular, wheel-specific intervention possibilities, which are advantageously possible in the case of slip control or stability control by wheel-specifically driven electric motors, as well as energy recovery in the case of slip control or stability control by an electromagnetic brake drive of electric motors, do not therefore take place. However, this would be desirable to enable energy efficiency and to improve slip control or stability control. 
     SUMMARY 
     In an embodiment, the present invention provides a system for an electrically driven vehicle. The system includes at least one motor controller configured to control at least one electric motor, with which at least one drive wheel of the vehicle can be driven. The system further includes at least one brake controller configured to control friction brakes, with each of which one of multiple drive wheels and/or non-driven wheels can be braked. The brake controller and the electric motor controller each have a data interface that is a bus interface. The brake controller and the electric motor controller are set up to send and/or receive data with a predefined maximum data transmission rate via the first data interface. The brake controller and the electric motor each have a second data interface, wherein each second data interface is designed to send and/or receive data with a higher data transmission rate than the maximum data transmission rate of the first data interface. The brake controller and the electric motor controller are set up to exchange data via the second data interfaces with a higher data transmission rate than with the first data interfaces. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be described in even greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. All features described and/or illustrated herein can be used alone or combined in different combinations in embodiments of the invention. The features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following: 
         FIG. 1  shows an exemplary embodiment of a system; 
         FIG. 2  shows an exemplary embodiment of a vehicle; and 
         FIG. 3  shows an exemplary embodiment of a method. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure provides for a way to also use an electric drive in the highly dynamic situation of positive and negative torque for slip control and stability control, in order in particular also to be able to use the high torque dynamics of electric drives for improved slip control and stability control. 
     For this purpose, the present disclosure relates to a system for an electrically driven vehicle. The system includes at least one motor control unit and at least one brake control unit. The motor control unit is used to drive at least one electric motor with which at least one drive wheel of the vehicle can be driven. Accordingly, in the case of multiple motors, each electric motor has a motor control unit, or a motor control unit is provided for multiple electric motors. 
     The brake control unit is used for the control of friction brakes, with each of which one of multiple drive wheels and additionally or alternately one of multiple non-driven wheels can be braked. The brake control unit and the electric motor control unit each have a first data interface. The first data interface is a bus interface. Particularly preferably, the bus interface is a CAN bus interface. The brake control unit and the electric motor control unit are also set up to exchange data via the first data interface. The first data interface has a predefined maximum data transmission rate. The predefined maximum data transmission rate, which can also be called the data transfer rate, data rate or transmission speed, refers to an amount of digital data which can be transmitted over a transmission channel, i.e. over a bus connection, by means of the data interface over a period of time. The maximum data transmission rate can also be called the channel capacity. In particular, in the present case, the predefined maximum data transmission rate results from the use of the data interface as a bus interface with a standardized protocol, such as preferably a CAN protocol. 
     In addition, the brake control unit and the electric motor control unit each have a second data interface. The second date interfaces are each designed to send and/or receive data with a higher data transmission rate than the maximum data transmission rate of the first data interface. Thus, the brake control unit and the electric motor control unit are set up to exchange data via the second data interface, wherein this can be carried out with a higher data transmission rate than the predefined maximum data transmission rate at which a data exchange can be carried out by means of the first data interface. 
     This makes it possible to control the electric motor control unit and the brake control unit by a vehicle control unit with a bus system via the first data interface, for example to transmit a positive or negative acceleration request of a driver to one or both of the control units, so that these can be used accordingly for accelerating or braking the vehicle. In particular, the brake control unit and the electric motor control unit can also exchange data via the first data interface. For example, a braking request of a driver, which has been passed to the brake control unit from the vehicle control unit via the first data interface, can therefore be supported by the brake control unit requesting braking support via the first data interface to the electric motor control unit by a braking operation of the electric motor or the electric motors, which can be controlled by the electric motor control unit. 
     In addition, however, the system has a motor control unit and a brake control unit, each with a second data interface, which allows a comparatively higher data transmission rate than the first date interface and thus a data exchange between the control units with a higher data transmission rate than with the first date interface. Highly dynamic torque change requests of an electrically driven motor can thus be generated centrally by the brake control unit and transferred directly to the electric motor control unit. This makes it possible to include the electric motors in the event of highly dynamic torque changes. Another advantage is that two data connections can also be used to exchange redundant data between the electric motor control unit and the motor control unit, thus increasing reliability. 
     According to a first embodiment, the motor control unit is set up to control multiple electric motors of an electrically driven vehicle, with each of which one of multiple drive wheels of the vehicle can be driven. Alternatively, multiple motor control units are provided, each of which drives an electric motor. Wheel-specific drives of a vehicle, which are individually controlled by the motor control unit, can thus be used via the second data interface and thus a second data connection between the motor control unit and the brake control unit in order to be able to use the electric motors wheel-specifically to support different driving situations. A significant improvement is therefore possible, in particular of a wheel-specific drive in the event of torque requests triggered by the brake control unit in exceptional driving situations, so that driving safety is improved. 
     According to a further embodiment, the motor control unit is set up, preferably continuously or at intervals, to determine a maximum currently available positive and/or negative torque value of the electric motor or each of the electric motors, which can be controlled by the motor control unit, and to transfer this via the second data interface to the brake control unit. Thus, a brake control unit, which is usually given a wheel-specific current target torque, for example from a vehicle control unit, also has available further information about maximum currently available positive or negative torque values of the electric motor or each of the electric motors. Thus, the brake control unit may, in the case of control of the electric motors by means of the motor control units, take into account maximum values for the control of the motor control unit when generating the control signals for the motor control unit on the one hand, and on the other hand for the generation of control signals for the control of the friction brakes. Maximum available positive or negative torque value of each of the electric motors, i.e. maximum realizable torque values in a specific driving situation, depend on the revolution rate, i.e. the vehicle speed, the state of charge of a battery driving the electric motors and the component temperatures of an electric drive comprising the electric motors. These state variables are calculated in the electric motor control unit taking into account known electric motor machine parameters for the control of the electric motors and other measured values. Such measurement values are, for example, the motor position, the phase current of at least two phases and/or the phase voltage. 
     According to a further embodiment, the brake control unit has at least one safety system which is set up, in particular in the case of activation of the safety system, to generate target torques for at least one of the wheels of the vehicle or respective target torques for all wheels of the vehicle. 
     In addition, the brake control unit is set up to derive differential torques from the target torques for the electric motor or each of the electric motors. Accordingly, the brake control unit, especially on activation of the safety system, generates control signals not only for friction brakes of the vehicle, but also for the electric motors. These are called differential torques. Preferably, these differential torques are to be understood as differential torques between a current torque of an electric motor and a requested higher or lower torque of the motor. In particular, when a safety function is performed by the safety system of the brake control unit, torque changes of the electric motors are generated directly in the brake control unit by the brake control unit and can be used thanks to fast transmission via the second data interface from the motor control unit to change the control of the electric motors. Increased safety in critical driving situations where a safety system is activated is provided by the highly dynamic switching on of electric motors. In addition, an increase in efficiency is also possible, since in particular electrical energy can be generated by generator braking of the electric motors, even in the case of functions carried out with a safety system,. 
     According to a further embodiment, the safety system of the brake control unit comprises a drive slip control and/or an anti-lock system and/or an electronic stability program. The drive slip control (ASR) can also be called automatic slip control or traction control. The drive slip control ensures that the wheels do not spin when starting up or on poor ground. Thus if slip of the drive wheels is threatened, the drive torque is preferably regulated by targeted withdrawal of the drive torque and optionally additional, preferably wheel-specific braking. The anti-lock system (ABS) is sometimes referred to as an automatic locking preventer (ABV). When braking, the anti-lock system counteracts possible locking of the wheels, in particular by reducing the braking pressure of the friction brakes, so that better steering or lane fidelity is carried out. In addition, the wheel slip can be regulated, so that a braking distance can be shortened on a wet road, for example. The ABS controls the wheel slip in such a way that the maximum force can be exchanged between the wheel and the road. This will reduce the braking distance. The driving dynamics control, also known as Electronic Stability Control (ESC) or often electronic stability program (ESP), is used to counteract vehicle swerving by means of targeted braking. 
     Preferably, according to this embodiment, all of the safety systems mentioned are integrated in the brake control unit and, thanks to the second data interface, these safety systems can generate torque changes on the drive wheels by controlling the electric motors by generating the differential torques for the electric motors in addition to the generation of a braking force with the friction brakes. 
     Improved safety and improved control accuracy and control speeds are thus possible. 
     According to a further embodiment, the brake control unit is set up to limit a differential torque for the electric motor depending on the maximum value of the currently available positive and/or negative torque. In the case of multiple electric motors, the brake control unit is set up to limit the differential torques for each of the electric motors depending on the respective maximum values of the currently available positive and/or negative torques of the respective motor. 
     Accordingly, the maximum values of the available torque previously supplied to the brake control unit are used to limit the differential torques generated in the brake control unit, so that it can be taken into account directly in the brake control unit to what extent the electric motors can have an influence on an acceleration change, in particular in the case of an intervention by the safety system. Accordingly, the friction brakes can then also be controlled in addition. Thus, it is ensured that the brake control unit never expects or takes into account a greater torque change from the electric motor or the electric motors in the event of an intervention than can actually be provided by the respective electric motor or electric motors. 
     According to a further embodiment, the brake control unit is set up to generate differential torques with a negative torque value or a positive torque value. Thus, the brake control unit is enabled, in particular in the case of a safety function carried out by a safety system, not only to brake the existing torque exerted on the wheels, but also to accelerate it. This can, in particular, lead to improved vehicle driving safety when operating an electronic stability program. In particular, in the case of the use of multiple electric motors, not only is wheel-specific braking possible, but also wheel-specific acceleration to support driving safety. 
     According to a further embodiment, the brake control unit is set up to generate braking torques for the control of the friction brakes of the respective drive wheels in the case of a limited differential torque for the electric motor or each of the electric motors. A braking torque for a drive wheel preferably comprises a difference between the target torque for the drive wheel and the limited differential torque for the electric motor of the drive wheel. In particular, if a drive wheel is to be braked, a differential torque for the electric motor of the wheel is first determined based on the target torque calculated by the brake control unit and the maximum possible torque of the motor. If the specified value is equal to the maximum value, it can be seen that a maximum braking torque of the motor is used, but moreover a greater braking torque is required. A corresponding braking torque is then generated by forming the difference for the friction brakes and the corresponding friction brake is thus controlled with this difference value by the brake control unit. 
     For braking, it is first prioritized to brake the drive wheels as strongly as possible by the motor and the friction brakes are only then used to support the braking. Thus, sufficient braking is always possible with the electric motors using maximum energy recovery. 
     According to a further embodiment, the brake control unit is set up to transmit the differential torques via the second data interface to the electric motor control unit. The electric motor control unit is set up to overlay the differential torques received via the second data interface with current target torque values, which are preferably received via the first data interface from a vehicle control unit. The electric motor control unit is therefore designed in such a way as to take into account not only target torque values specified by a vehicle control unit when controlling one or more of the electric motors, but also the differential torques generated in the brake control unit. 
     According to a further embodiment, the electric motor control unit has an overlay element, which is preferably an addition element, for overlaying the difference torques for the electric motor or each of the electric motors on the or the respective current target torque value for the respective electric motor, in particular by addition. A simple realization of an overlay is possible in particular by addition. 
     According to a further embodiment, the system is set up to activate the safety system when detecting a slip value of at least one wheel which is above a predefined threshold value, and to generate measures to reduce the slip value by generating target torques for at least one or more of the drive wheels and/or non-driven wheels. There is no interaction with the vehicle control unit or other control units in this case. 
     A fast data exchange is therefore only necessary between the brake control unit and the motor control unit, so that the addition of a second data interface for further control units, in particular for the vehicle control system, is not necessary. In addition, the vehicle control unit does not need to be used when triggering safety measures, so that it is not necessary to change the functionality of the vehicle control unit in order to integrate the existing system into a vehicle. 
     In addition, the present disclosure provides a vehicle which is in particular a utility vehicle, such as a truck. The vehicle comprises a system according to any one of the aforementioned embodiments. 
     According to a particular embodiment of the vehicle, the vehicle comprises a vehicle control unit comprising a first data interface, which is a bus interface. Preferably, the bus interface is a CAN bus interface. In addition, the vehicle control unit is set up to send target torque values to the electric motor control unit via the first data interface of the vehicle control unit to the first data interface of the electric motor control unit. Furthermore, the vehicle control unit is set up to send target torque values to the brake control unit via the first data interface of the vehicle control unit to the first data interface of the brake control unit. 
     According to a further embodiment of the vehicle, it comprises multiple driven wheels, each with an electric motor, each of which can be individually operated with an individual torque by one or a respective electric motor control unit. 
     In addition, the present disclosure provides a method for operating a vehicle according to any one of the aforementioned embodiments or a system according to any one of the aforementioned embodiments. 
       FIG. 1  shows a system  10  according to an exemplary embodiment. The system  10  comprises one brake control unit  12  and two motor control units  14 . The brake control unit  12  as well as the motor control units  14  each have a first data interface  16   a,    16   b,    16   c.  The first data interface  16   a,    16   b,    16   c  is a bus interface  17 , in particular a CAN bus interface  19 , and can therefore also be referred to as a CAN-bus-interface. The motor control units  14  are each used for driving an electric motor  18 . A drive wheel of a vehicle can be driven by each electric motor  18 . In the present case, according to this exemplary embodiment, two motor control units are shown, each controlling an electric motor  18 , wherein according to another exemplary embodiment, which is not shown here, also a single motor control unit  14  is provided to control multiple electric motors  18 . In addition, a vehicle control unit  20  is shown, which also has a first data interface  16   d.  The vehicle control unit  20  is set up to transfer target torque values  24  for the electric motors  18  to the motor control units  14  via a bus connection  22  and the first data interfaces  16   a,    16   b,    16   d.  The bus connection has a predefined maximum data transmission rate  23 . 
     In addition, the vehicle control unit  20  is set up to transmit a negative acceleration request  26 , i.e. a braking request, to the brake control unit  12 . In the case of a negative acceleration request  26  specified by the vehicle control unit  20 , the brake control unit produces  12  braking torques  28  for friction brakes  30  of the vehicle. This is done with a first function block  32  of the brake control unit  12 . A second function block, which is referred to here as a safety system  34 , of the brake control device  12  receives this negative acceleration request  26  also, wherein additionally a slip or a slip signal  36  of one or more of the wheels of the vehicle is fed to this function block  34 . The slip signal  36  is calculated or determined in the brake control unit  12  itself according to an alternative exemplary embodiment. The brake control unit  12  or, as shown here another function block, receives slip values  31  for each of the wheels. This is done by measuring or calculating the vehicle speed and the wheel revolution rate. The slip values  31  are compared with at least one predefined threshold value  33 . For example, the slip signal  36  is generated when the threshold value  33  is exceeded by a slip value  31 . 
     The brake control unit  12  also has a second data interface  38   a,  which is connected to second data interfaces  38   b,    38   c  of the motor control units  14  via a data line  39 . The data line  39  to which the second data interfaces  38   a - 38   c  are connected has a data transmission rate  35 , which is higher than the maximum data transmission rate  23  of the bus connection  22 , to which the first data interfaces  16   a - 16   c  are connected. By means of the second data interface  38   a,  the brake control unit receives  12 , continuously or at intervals from the respective motor control unit  14  via a sensor interface  40 , provided maximum available positive or negative torque values  41  of the electric motors  18  which are correspondingly connected to the motor control units  14 . 
     In the event of a slip signal  36  occurring, the safety system  34  is activated in the brake control unit  12  and target torques  42  are generated for each wheel of the vehicle. These target torques  42  are converted into differential torques  44 , taking into account the maximum currently available positive or negative torque values  41 , which are each fed via the second data interfaces  38   a  to the corresponding data interfaces  38   b,    38   c  of the motor control units  14 . The differential torques  44  can include positive torque values  27  or negative torque values  29 . The differential torque values  44  are accordingly overlaid on the target torque values  24 , which are present in the respective motor control unit  14 , and thereby a specified torque value  46  is determined. This is done by an overlay element  47 , which is an addition element  47  here. A signal  48  is generated in a converter  49  from the specified torque value  46  for controlling a pulse-width modulator  50 , which thereby generates a pulse width modulation  52 , in order to provide an alternating voltage for the electric motors  18  with inverters  54 . In addition, differences  53 , i.e. difference values, are formed from each of the target torques  42  and the respective differential torque value  44  for an electric motor  18  to generate braking torques  28  for the friction brakes  30 . 
     The safety system  34  can thus intervene directly in the control of the electric motors  18 . Preferably, the safety system  34  comprises a drive slip control  43 , an anti-lock system  45  and an electronic stability program  51 . 
       FIG. 2  shows an exemplary embodiment of a vehicle  60 , which has four wheels  62 . The vehicle  60  is a utility vehicle  61 . Two of the wheels  62  are drive wheels  64  and two of the wheels  62  are non-driven wheels  66 . The drive wheels  64  each have an electric motor  18 . Each of the wheels  62  also has a friction brake  58 . In addition, the vehicle  60  comprises a system  10  and a vehicle control unit  20 . 
       FIG. 3  shows the steps of a method according to an exemplary embodiment. In one step  70 , a brake control unit  12  calculates a slip signal  36 , which indicates the slip  36  of one or more wheels  62  of the vehicle  60 . In step  72 , a safety system  34  of the brake control unit  12  is activated and in step  74  target torques  42  for each of the wheels  62  are determined. In step  76  differential torques  44  for the electric motors  18  of the drive wheels  64  are generated from the target torques  42 , wherein here in step  78  the differential torques  44  are transmitted via a second data interface  38   a  of the brake control unit  12  to the electric motor control unit  14 . In step  80 , the differential torques  44  are overlaid on target torque values  24  of the corresponding electric motors  18  and in step  82  the electric motors  18  are each controlled with the overlaid target torque values  24 . 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. It will be understood that changes and modifications may be made by those of ordinary skill within the scope of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below. 
     The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and/or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C. 
     LIST OF REFERENCE CHARACTERS 
     
         
           10  system 
           12  brake control unit 
           14  motor control units 
           16   a - 16   b  first data interface of the motor control unit 
           16   c  first data interface of the brake control unit 
           16   d  first data interface of the vehicle control unit 
           17  bus interface 
           18  electric motor 
           19  CAN-bus interface 
           20  vehicle control unit 
           22  bus connection 
           23  data transmission rate 
           24  target torque values 
           26  negative acceleration request 
           27  positive torque value 
           28  braking torques 
           29  negative torque value 
           30  friction brakes 
           31  slip value 
           32  first function block 
           33  threshold value 
           34  safety system 
           35  data transmission rate 
           36  slip signal 
           38   a  second data interface of the brake control unit 
           38   b - 38   c  second data interfaces of the motor control unit 
           39  data line 
           40  sensor interface 
           41  maximum currently available positive or negative torque value 
           42  target torque 
           43  drive slip control 
           44  differential torque 
           45  anti-lock system 
           46  specified torque value 
           47  overlay element 
           48  signal 
           49  converter 
           50  modulator 
           51  electronic stability program 
           52  pulse width modulation 
           53  differences 
           54  inverter 
           58  friction brake 
           60  vehicle 
           61  utility vehicle 
           62  wheels 
           64  drive wheels 
           66  non-driven wheels 
           70 - 82  steps of the method