Abstract:
The general principle underlying the invention is a braking system that is provided with an arithmetic unit with at least two independent channels for determining the reference speeds approximated to the actual vehicle speed. The at least two determined reference speeds are used only for regulating a part of the brakes installed in the vehicle.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION  
         [0001]    The present invention relates to a braking system for vehicles equipped with an ABS system or an antiskid protection system.  
           [0002]    An antilock system for a motorcycle is known from German Patent Document 39 31 313 A1, in the case of which a total of only two rotational wheel speed sensors are provided, one sensor being assigned to the front wheel and the other being assigned to the rear wheel. For determining the wheel slip, a reference quantity is determined which is approximated to the course of the vehicle speed and in which case two channels are provided. The two reference speeds are determined on the basis of the assigned wheel speed and a multiplier dependent on the driving condition.  
           [0003]    U.S. Pat. No. 5,791,744 A describes an electropneumatic braking system for rail vehicles, in which a ”universal unit” is assigned to each car and controls the brakes of the respective car. Such a universal unit consists of an electronic portion, a pneumatic portion and an electropneumatic portion. The electronic portion has, among other things, an interface for rotational wheel speed sensors.  
           [0004]    German Patent Document DE 198 26 131 A1 describes an electric braking system for a motor vehicle in which two electronic arithmetic channels are provided. In the case of this braking system, among other values, slip values are computed individually for the each wheel. The rotational wheel speed of the respective wheel and a centrally computed estimated value for the vehicle speed are entered into the computation of the slip, the vehicle speed being computed in a single-channel manner, that is, not redandantly.  
           [0005]    Modern road and rail vehicles are normally equipped with an antilock system which, in the case of road vehicles, is called an “ABS system” and, in the case of rail vehicles, is called an “antiskid protection system”. ABS systems and antiskid protection systems control the brake pressures at individual wheels or axles of the vehicle such that a locking of the wheels or wheel sets is prevented and the length of the braking is minimized. For such a brake pressure control, the slip values which exist at the individual wheels or axles are required and are determined from the respective wheel speeds and the actual vehicle speed. For this purpose, rotational wheel speed sensors are normally provided. In which case, an approximate value for the actual vehicle speed, that is, a “refernce speed”, is determined from the individual rotational wheel speeds. When the measured rotational wheel speed signals are faulty, for example, as a result of electromagnetic interference fields and/or system-caused measuring errors, which result in “peaks” in the speed course or acceleration course of the measuring signals, errors may then also occur when computing the reference speed.  
           [0006]    A “false” reference speed may result in errors in controlling the braking force of the entire vehicle. This is problematic particularly in the case of those vehicles which only have an independent system for the braking force control.  
           [0007]    The reason is that ABS systems or antiskid protection systems normally have a single-channel construction; that is, the rotational wheel speeds are detected in a single-channel manner. If one rotational wheel speed sensor fails, the assigned wheels can no longer be controlled corresponding to the existing rotational wheel speed.  
           [0008]    To prevent faulty rotational wheel speed signals from falsifying the refernce speed value, conventional algorithms for computing the reference speed have a “detection” of faulty signals, but a reliable detection of all posible faults required very high expenditures. In addition, faults may have an effect on the calculation of the reference speed already during the fault disclosure time such that the braking force is affected.  
           [0009]    It is an object of the invention to provide a braking system which is optimized with respect to the determination of the actual vehicle speed required for an ABS or antiskid protection control. This object is achieved by the present invention.  
           [0010]    The basic principle of the invention consists of a braking system with an arithmetic unit which has at least two separate “channels”, in which, independently of one another, a “reference speed” is determined which is approximated to the actual vehicle speed. The at least two reference speeds are in each case used only for controlling a portion of the brakes in the vehicle.  
           [0011]    The separate computation of the reference speeds can take place in a brake control unit or in an arithmetic unit. Only a part of the rotational wheel speed sensors in the vehicle, as well as a portion of the brakes in the vehicle, are assigned to each of the channels. On each channel, rotational wheel speed signals of different sensors are used for computing one reference speed respectively. Consequently, in the case of two channels, maximally half the brakes in the vehicle are controlled on the basis of one of the two reference speeds. Even when only one arithmetic unit, that is, one brake control unit, is provided, an error occurring in the detection of the rotational wheel speed may have an effect on maximally half of the brakes. An individual fault in the speed detection can therefore not influence the entire braking force of the vehicle.  
           [0012]    In the “redundant” detection of the rotational wheel speed, at least two rotational wheel speed signals of a wheel or of a wheel group are always included in the control. The wheel or the wheel group can therefore also still be controlled when one of the two rotational wheel speed signals fails or has interference. This significantly improves the driving safety.  
           [0013]    According to a further development of the invention, for a vehicle or in the case of several vehicle units coupled to one another, including at least one front axle and one rear axle, at least one front axle signal and one rear axle signal is analyzed on each channel. Thus, at least one rotational wheel speed sensor of a front axle and one rotational wheel speed sensor of a rear axle is connected to each channel. The first channel can therefore be used, for example, for the braking force control of the front axle or front axle group, and the second channel can be used for the braking pressure control of the rear axle or the rear axle group.  
           [0014]    According to a further development of the invention, a control unit is provided for the plausibility check of the rotational wheel speed signals supplied by the rotational wheel speed sensors. The rotational wheel speed signals are checked particularly with respect to “signal peaks” which are based on interference. In the control unit, an analyzing algorithm is implemented which recognizes “faulty” rotational wheel speed signals and optionally excludes them for calculating the reference speed. All detected rotational wheel speed signals can be analyzed in a common arithmetic unit, can be compared with one another and can be checked with respect to plausibility. This permits the detection of “implausible” or “disturbed” rotational wheel speed signals and therefore increases the safety of the entire braking system.  
           [0015]    The invention can be implemented at very reasonable cost because only one arithmetic unit or only one brake control unit is required. It can be used in the case of passenger cars, trucks, bikes as well as in the case of rail vehicles or trains.  
           [0016]    These an other aspects of the present invention will become apparent from the following detailed description of the invention, when considered in conjunction with accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is a schematic view of a first embodiment for explaining the basic principle of the invention.  
         [0018]    [0018]FIG. 2 is a schematic view of an embodiment of a use in the case of a motor bike.  
         [0019]    [0019]FIG. 3 is a schematic view of an embodiment similar to that of FIG. 1.  
         [0020]    [0020]FIG. 4 is a schematic view of an embodiment of a four-axle vehicle with kinematically uncoupled axles.  
         [0021]    [0021]FIG. 5 is a schematic view of a first embodiment of a six-axle vehicle system.  
         [0022]    [0022]FIG. 6 is a schematic view of a second embodiment of a six-axle vehicle system.  
         [0023]    [0023]FIG. 7 is a schematic view of a third embodiment of a six-axle vehicle system.  
         [0024]    [0024]FIG. 8 is a schematic view of a fourth embodiment of a six-axle vehicle system.  
         [0025]    [0025]FIG. 9 is a schematic view of an embodiment of an eight-axle vehicle system.  
         [0026]    [0026]FIG. 10 is a schematic view of an embodiment of a traction vehicle with kinematically coupled axles.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]    [0027]FIG. 1 illustrates a vehicle  1  with a first wheel group  2  and a second wheel group  3 . The two wheel groups  2 ,  3  may, for example, be bogies of a rail vehicle and each has a first axle  4 ,  5  and a second axle  6 ,  7  respectively. One rotational wheel speed sensor  8 - 11  respectively is assigned to the axles  4 - 7 .  
         [0028]    The rotational wheel speed sensors  8 - 11  are connected with a brake control unit  12  which is shown here only schematically. In the brake control unit  12 , a plausibility check  13  is implemented which is to detect faulty or “disturbed” rotational wheel speed signals and optionally separate them.  
         [0029]    The brake control unit  12  also has two channels for the separate or independent calculation of one reference speed respectively approximated to the actual vehicle speed. Brakes (not shown) provided in the vehicle are assigned to a first or to a second group. Here, the first group is formed by the brakes of the first wheel group  2 , and the second group is formed by the brakes of the second wheel group  3 . The brakes of the first wheel group  2  are controlled by a first channel of the brake control unit  12 , and the brakes of the second wheel group  3  are controlled by a second channel of the brake control unit  12 .  
         [0030]    On the first channel, the rotational wheel speed signals are analyzed which are supplied by the rotational wheel speed sensors  8 ,  9 . If the plausibility check  13  indicates that the signal supplied by the rotational wheel speed sensors  8 ,  9  are plausible, both signals are entered into the reference speed calculation  14  of the first channel.  
         [0031]    In the reference speed calculation  14 , for example, both signals supplied by the rotational wheel speed sensors  8 ,  9  can be linked with one another to form a first reference speed V ref1 . However, during a braking operation, it may also make sense to consider the greater of the speeds measured by the rotational wheel speed sensors  8 ,  9  as the V ref1 . If the vehicle  1  is a traction vehicle and is just being accelerated, it may, in contrast, make sense to accept the lower of the two speeds measured by the rotational wheel speed sensors  8 ,  9  as the reference speed V ref1 .  
         [0032]    The reference speed V ref1  determined by calculation  14  on the basis of rotational wheel speed signals of the first wheel group  2  and of the second wheel group  3  is used for the braking force control  15  of the first wheel group  2 . The rotational wheel speed signals supplied by the rotational wheel speed sensors  8 ,  10  of the first wheel group  2  are entered into the “braking force control”  15 . Furthermore, the results of the plausibility check  13  are taken into account during the braking force control  15 . If the signals supplied by the rotational wheel speed sensors  8 ,  10  are considered plausible, they can both be taking into account. Otherwise, a possibly faulty signal does not have to be considered.  
         [0033]    The second channel is provided for the braking force control of the second wheel group  3 . On channel  2 , a reference speed calculation  16  is carried out using the signals supplied by the rotational wheel speed sensors  10 ,  11 , analogous to channel  1 . The results of the plausibility check  13  are also taken into account. On the basis of the determined reference speed V ref2  by calculation  16 , control signals are generated for a braking force control  17 . During the braking force control  17 , the signals supplied by the rotational wheel speed sensors  9 ,  11  as well as the results of the plausibility check  13  are analyzed.  
         [0034]    An important advantage of the invention consists of the fact that a fault or an interference on one of the two channels can affect maximally half of the brakes in the vehicle  1 . If, for example, one of the two channels fails completely, the brakes of the other channel continue to be controllable. As an alternative to the embodiment illustrated here, more than two channels may also be provided, which further improves the fail-safe characteristic.  
         [0035]    [0035]FIG. 2 shows an embodiment in relation to a motor bike  17  having a rear wheel  18  and a front wheel  19 . At the rear wheel  18 , the two rotational wheel speed sensors  8 ,  10  are provided and, at the front wheel  19 , the two rotational wheel speed sensors  9 ,  11  are provided to measure the speed of the front wheel or of the rear wheel. The rotational wheel speed sensors  8 - 11  are connected to the brake control unit  12  which is constructed analogous to FIG. 1. Analogous to FIG. 1, here also, two separate channels are provided, in which case a rotational wheel speed sensor  8 ,  9  and  10 ,  11  respectively is assigned to each channel. In the embodiment illustrated here, the rear wheel brake (not shown) is controlled by channel  1  and the front wheel brake is controlled by channel  2 . The rotational wheel speed sensors  8 ,  10  and  9 ,  11  respectively may be integrated in a “double pulse generator” which is more cost-effective than two individual sensors. rotational wheel speed signals supplied by the rotational wheel speed sensors  8 ,  10  of the first wheel group  2  are entered into the &#34;braking force control&#34;  15 . Furthermore, the results of the plausibility chech  13  are taken into account during the braking force control  15 . If the signals supplied by the rotaitonal wheel speed sensors  8 ,  10  are considered plausible, they can both be taken into account. Otherwise, a possibly faulty signal does not have to be considered.  
         [0036]    The second channel is provided for the braking force control of the second wheel group  3 . On channel  2 , a reference speed calculation  16  is carried out using the signals supplied by the rotational wheel speed sensors  10 ,  11  analogous to channel  1 . The results of the plausibility check  13  are also taken into account. On the basis of the detemined reference speed V ref2  by caluculation  16 , control signals are generated for a braking force control  17 . During the braking force control  17 , the signals supplied by the rotational wheel speed sensors  9 ,  11  as well as the results of the plausubility check  13  are analyzed.  
         [0037]    An important advantage of the invention consists of the fact that a fault or an interference on one of the two channels can effect maximally half of the brakes in the vehicle  1 . If, for example, one of the two channels fails completely, the brakes of the other channel continue to be controllable. As an alternative to the embodiment illustrated here, more than two channels may also be provided, which further improves the fail-safe characteristic.  
         [0038]    [0038]FIG. 2 shows an embodiment in relation to a motor bike  17  having a rear wheel  18  anf a from wheel  19 . At the rear wheel  18 , the two rotational wheel speed sensors  8 ,  10  are provided and, at the front wheel  19 , the two rotational wheel speed sensors  9 ,  11  are provided to measure the speed of the from wheel or of the rear wheel. The rotational wheel speed sensors  8 - 11  are connected to the brake control unit  12  which is constucted analogous to FIG. 1. Analogous to FIG. 1, here also, two separate channels are provided, in which case a rotational wheel speed sensor  8 ,  9  and  10 ,  11  respectively is assigned to each channel. In the embodiment illustrated here, the rear wheel brake (not shown) is controlled by channel  1  and the from wheel brake is controlled by channel  2 . The rotational wheel speed sensors  8 ,  10  and  9 ,  11  respectively may be intergrated in a &#34;double pulse generator&#34; which is more cost-effective than two individual sensors.  
         [0039]    [0039]FIG. 3 shows an embodiment similar to that of FIG. 1, in which the axles  4 ,  6  of the first wheel group  2  and the axles  5 ,  7  of the second wheel group  3  are each kinematically coupled, for example, by way of a connecting rod or a gearing. The rotational wheel speed sensors  8 - 11  are in each case assigned to the axles  4 ,  6  and  5 ,  7  respectively. Analogus to the embodiment of FIG. 1, the rotational wheel speed sensors  8 ,  9  are assigned to a first channel  20  which is provided for controlling a first—here only schematically shown—group of brakes  21 . Analogously thereto, the rotational wheel speed sensors  10 ,  11  are assigned to a second channel  22  which is provided for controlling a second brake group  23 . Although the two channels  20 ,  22  are shown as separate “units”, they may, as illustrated in FIGS. 1 and 2, be formed by a common arithmetic unit.  
         [0040]    [0040]FIG. 4 shows another embodiment of a four-axle vehicle. In contrast to the embodiment of FIG. 3, here, the axles  4  and  6  of the first wheel group or the axles  5  and  7  of the second wheel group are kinematically uncoupled from one another. One rotational wheel speed sensor  8 ,  9  respectively is provided on the axles  4  and  7 . Two rotational wheel speed sensors  10 ,  11  and  24 ,  25  respectively are provided on the axles  5  and  6 . The rotational wheel speed sensors  8 ,  11 ,  24  are assigned to the first channel  20 , and the rotational wheel speed sensors  9 ,  10 ,  25  are assigned to the second channel  22 , channel  20  taking over the brake control, for example, at the axles  4  and  6 , and channel  22  taking over the brake control at the axles  5  and  7 .  
         [0041]    [0041]FIG. 5 shows a embodiment for a six-axle vehicle which consists of two mutually coupled vehicle units  26 ,  27 . A first wheel group  2  is assigned to vehicle unit  26 , and a second wheel group  3  is assigned to vehicle unit  27 . Furthermore, a “center” wheel group  28  is provided which is assigned to both vehicle units  26 ,  27 . Wheel groups  2 ,  3 ,  28  are, for example, bogies of a rail vehicle to which one brake group  29 - 31  respectively is assigned. The brake groups  29 ,  30  each having one brake unit  32 ,  33 , and the brake group  31  having two brake units  34 ,  35 . Here, the term “brake unit” indicates an individual brake or a group of brakes which are controlled by means of a common brake pressure.  
         [0042]    The brake units  32 ,  34  are controlled by the first channel  20 , and the brake units  33 ,  35  are controlled by the second channel  22 . Here, one rotational wheel speed sensor  38 ,  39  respectively of the axles  4 ,  6  as well as one rotational wheel speed sensor  40  of an axle  36  of the center wheel group  28  are assigned to the first channel  20 . Rotational wheel speed sensors  41 ,  42  of the axles  5 ,  7  as well as a rotational wheel speed sensor  43  of an axle  37  of the center wheel group  28  are assigned to the second channel  22 .  
         [0043]    In the case of the embodiment illustrated in FIG. 5, the six axles  4 - 7 ,  36 ,  37  are not coupled kinematically. The brakes of the axles  36 ,  37  may be acted upon by different pressures. The brake control of the brake unit  34  takes place by way of the first channel, and the brake control of the brake unit  35  takes place by way of the second channel  22 . The brake unit  32  is also controlled by the first channel  20 , and the brake unit  33  is controlled by the second channel  22 .  
         [0044]    [0044]FIG. 6 shows an embodiment of a six-axle vehicle, in which the individual axles of the wheel groups  2 ,  3 ,  28  are kinematically coupled, for example, by a transmission or a connecting rod. Two rotational wheel speed sensors  38 - 44  respectively are provided here on the axle  6  of wheel group  2 , the axle  37  of wheel group  28  and on the axle  5  of wheel group  3 . Furthermore, one additional rotational wheel speed sensor  45 - 47  respectively may be provided on the axles  4 ,  7 ,  36 , which sensors  45 - 47  are indicated here by a broken line.  
         [0045]    In contrast to the above-explained embodiments, three channels  48 - 50  are provided here in FIG. 6. The rotational wheel speed sensors  39 ,  43  and  46  are assigned to the first channel  48 ; the rotational wheel speed sensors  38 ,  42  and  47  are assigned to the second channel  49 ; and the rotational wheel speed sensors  40 ,  44  and  45  are assigned to the third channel  50 . Since the individual axles of the wheel group  2 ,  3 ,  28  are kinematically coupled, only three brake units  30 - 37  exist here. Brake unit  32  is controlled by the first channel  48 ; brake unit  34  is controlled by the second channel  49 ; and brake unit  33  is controlled by the third channel  50 . In contrast to the embodiment of FIG. 5, here the individual brakes of the wheel groups  2 ,  3 ,  38  are each controlled by means of the same brake pressure.  
         [0046]    [0046]FIG. 7 shows another embodiment for a six-axle vehicle, in which the axles of the wheel groups  2 ,  3  and  28  are kinematically coupled. In contrast to FIG. 6, only two channels  20 ,  22  are provided here. Channel  20  controls the brake units  32  and  34  of wheel groups  2  and  28  respectively; and channel  22  controls the brake units  33  and  35  respectively of the wheel groups  3  and  28  respectively. The rotational wheel speed sensors  38 ,  39  of axles  6  and  36  respectively are assigned to the first channel  20 . In addition, a rotational wheel speed sensor  40  of the axle  7  may be assigned to channel  20 . Two rotational wheel speed sensors of vehicle unit  26  and one rotational wheel speed sensor of vehicle unit  27  are then assigned to channel  20 .  
         [0047]    Analogously thereto, the rotational wheel speed sensor  41  of axle  37 , the rotational wheel speed sensor  42  of axle  5 , and optionally the rotational wheel speedsensor  43  of axle  4  are assigned to the second channel  22 . The channel  22  therefore analyzes two rotational wheel speed signals of vehicle unit  27  and one rotational wheel speed signal of vehicle unit  26 .  
         [0048]    [0048]FIG. 8 shows another embodiment for a six-axle vehicle. In this embodiment, the two axles  4 ,  6  of wheel group  2  and the axles  5 ,  7  of wheel group  3  are each kinematically coupled with one another. In contrast, the axles  36 ,  37  of the center wheel group  28  are not coupled kinematically. Correspondingly, the assigned brake units  34 ,  35  of the axles  36 ,  37  can be controlled by different brake pressures. The brake unit  34  is controlled together with the brake unit  32  of the wheel group  2  by means of the first channel  20 ; and the brake units  33 ,  35  are controlled by the second channel  22 . Here, a rotational wheel speed sensor  38  of the wheel group  2  and the rotational wheel speed sensor  39  of the axle  36  are assigned to channel  20 . Optionally, the rotational wheel speed sensor  43  of the axle  37  may be assigned to channel  20 . Analogously thereto, a rotational wheel speed sensor  40  of the wheel group  3 , a rotational wheel speed sensor  41  of the axle  37 , and optionally, a rotational wheel speed sensor  42  of the axle  36  are assigned to the second channel  22 .  
         [0049]    In the embodiment illustrated in FIG. 8, two kinematically uncoupled axles and four axles which are in each case kinematically coupled in pairs are therefore provided, in which case the brakes of the center wheel group  28  can be acted upon by different brake pressures.  
         [0050]    [0050]FIG. 9 shows an eight-axle vehicle which consists of three vehicle units  51 - 53  and has four wheel groups  54 - 57 . Each of the wheel groups consists of two axles which are each kinematically coupled with one another. Furthermore, at least one rotational wheel speed sensor  38 - 41  respectively is assigned to each wheel group  54 - 57 . At wheel groups  55 ,  56 , optionally a second rotational wheel speed sensor  42 ,  43  may in each case be provided. Here, the rotational wheel speed sensors  38 ,  39 ,  43  are assigned to the first channel  20 , and the rotational wheel speed sensors  40 ,  41  and  42  are assigned to the second channel  22 . The brakes of the wheel groups  54 - 57  form one brake unit  58 - 61  respectively. The brake units  58 ,  59  are controlled by the first channel  20 , and the brake units  60 ,  61  are controlled by the second channel  22 .  
         [0051]    [0051]FIG. 10 shows an embodiment of a traction vehicle  62  which has four axles  4 - 7  which are kinematically coupled by way of a connecting rod  63 . A rotational wheel speed sensor  8  of a first channel  20  is assigned to the two axles  4 ,  5 , and a rotational wheel speed sensor  9  of a second channel  22  is assigned to the axles  6 ,  7 . Channel  20  controls the brakes of axles  4 ,  5 , and channel  22  correspondingly controls the brakes of axles  6 ,  7 .  
         [0052]    Although the present invention has been described and illustrated in detail, it is to be clearly understood that this is done by way of illustration and example only and is not to be taken by way of limitation. The scope of the present invention is to be limited only by the terms of the appended claims.