Patent Publication Number: US-6991302-B2

Title: Brake system with distributed electronic control units

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to an electronically controlled braking system which is intended for use with wheeled vehicles, and more particularly to a such a braking system which incorporates distributed electronic control units. 
   BACKGROUND OF THE INVENTION 
   Traditional braking systems for motor vehicles include conventional hydraulic or pneumatic brakes associated with two or more wheels of the vehicle. Such conventional brakes are actuated by pressurized fluid or compressed air. When actuated, the brakes exert a force on a disk or drum which spins in conjunction with the wheel of the vehicle in order to create frictional forces which resist rotation of the wheel. Traditionally, control signals have been transmitted to each of the brake system&#39;s actuators mechanically, or by a hydraulic or pneumatic control circuit. However, it has more recently been proposed to employ a centralized control unit to generate electronic control signals and to use such electronic control signals to control actuation of a vehicle&#39;s brakes. This type of electronic control scheme has become even more prevalent in view of modern brake systems which now often include not only conventional hydraulic or pneumatic brake actuator functionality, but also supplemental electronic functions such as antilock protection (ABS) and/or electronic braking force distribution (EBV) between the front and rear axles. 
   In some brake systems employing electronic control, it is known to employ distributed electronic control units to receive electronic control signals from the central control unit and to control the actuation of brake components in response thereto. Such distributed electronic control units may be associated with each individual brake component and/or may be associated with two or more brake components (for example, one distributed electronic control unit may be associated with both brake actuators on a single axle). In either case, the central control unit generates and transmits electronic control signals to each of the distributed electronic control units via one or more control networks, and the distributed electronic control units, in response to such electronic control signals, cause the brake component(s) with which they are associated to actuate. Such a system, however, suffers from a number of disadvantages. One disadvantage of such a system is that all brake components must be responsive to a single control signal, as there is no way for control signals intended for controlling only one brake component or group of brake components to be differentiated from those control signals intended for controlling another brake component or group of brake components. 
   This disadvantage is obviated by certain brake systems which employ a scheme for the recognition of the physical position of each individual brake component or each group of brake components. Known schemes of this type generally involve the manual programming or setting of a unique identifier in the memory of each distributed electronic control unit, which identifier is indicative of the physical position of the brake component or group of brake components with which the distributed electronic control unit is associated. In these systems, each of the control signals generated by the central control unit includes an indication of the identifier of the distributed control unit for which that control signal is intended. When each distributed electronic control unit receives the control signals, it determines, based upon the identifier contained in each control signal, whether that particular control signal is intended for it, and if so, responds accordingly. If that particular control signal is not intended for it, the control signal is ignored. 
   For example, the distributed electronic control unit associated with a brake component on the right front wheel of a vehicle may be programmed with an identifier indicative of such a position. Thus, when control signals are received from the central control unit, the distributed electronic control unit associated with a brake component on the right front wheel of the vehicle responds to the control signal only if that control signal includes the appropriate identifier (if not, the control signal is ignored). Distributed electronic control units associated with groups of brake components (e.g., the brake components on a vehicle axle) may be similarly programmed and controlled. 
   While the above-described control scheme allows each individual brake component or each group of brake components to be independently controlled by the central control unit, it does still suffer from a number of disadvantages. More specifically, the manual programming or setting of the unique identifier in the memory of each distributed electronic control unit may create compatibility problems, which may lead the brake system to operate inefficiently or even fail completely. This is true because each time a distributed electronic control unit is replaced and/or its location in the system is changed, the distributed electronic control unit must be manually programmed or reprogrammed. For example, if a brake component including a distributed electronic control unit failed and was replaced, the new brake component must be programmed with the identifier appropriate for its location. If the service technician overlooks such programming or programs the distributed electronic control unit incorrectly, that brake component may not respond at all, or may respond at inappropriate times. 
   A similar problem may occur if the locations of two or more brake components are switched. For example, if the left front and right front brake components are switched during servicing and not reprogrammed, the control signals generated by the central control unit intended to control the left front brake component would actually be controlling the right front brake component, while the control signals intended to control the right front brake component would actually be controlling the left front brake component. This could cause a hazardous condition during vehicle operation. Moreover, even if programming and/or reprogramming is carried out correctly, the process may be time-consuming and would likely require additional knowledge on the part of service technicians who service the brake system. 
   What is desired, therefore, is an electronically controlled braking system intended for use with wheeled vehicles which incorporates distributed electronic control units, which allows for the control of each individual brake component or each group of brake components associated with each distributed electronic control unit independently of those associated with other distributed electronic control units, which allows for control signals intended for controlling only one brake component or group of brake components to be differentiated from those control signals intended for controlling another brake component or group of brake components, which does not require that the distributed electronic control unit be manually programmed or reprogrammed each time a distributed electronic control unit is replaced and/or its location in the system is changed, and which employs an identification scheme, the implementation of which is not time-consuming and/or does not require additional knowledge on the part of service technicians who service the brake system. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an object of the present invention to provide an electronically controlled braking system intended for use with wheeled vehicles which incorporates distributed electronic control units. 
   Another object of the present invention is to provide an electronically controlled braking system having the above characteristics and which allows for the control of each individual brake component or each group of brake components associated with each distributed electronic control unit independently of those associated with other distributed electronic control units. 
   A further object of the present invention is to provide an electronically controlled braking system having the above characteristics and which allows for control signals intended for controlling only one brake component or group of brake components to be differentiated from those control signals intended for controlling another brake component or group of brake components. 
   Still another object of the present invention is to provide an electronically controlled braking system having the above characteristics and which does not require that the distributed electronic control unit be manually programmed or reprogrammed each time a distributed electronic control unit is replaced and/or its location in the system is changed. 
   Yet a further object of the present invention is to provide an electronically controlled braking system having the above characteristics and which employs an identification scheme, the implementation of which is not time-consuming and/or does not require additional knowledge on the part of service technicians who service the brake system. 
   These and other objects of the present invention are achieved in one embodiment by provision of an electronically controlled braking system including at least one central control unit operable to assign identifiers during an identifier assignment routine, a first distributed electronic control unit, a second distributed electronic control unit and a control network electrically connecting the at least one control unit, the first distributed electronic control unit and the second distributed electronic control unit. The identifiers include a first identifier and a second identifier, with one of the first identifier or the second identifier being assigned to the first distributed electronic control unit and the other of the first identifier or the second identifier being assigned to the second distributed electronic control unit at least in part based upon the timing of a signal reaching, via the control network, the first distributed electronic control unit and the second distributed electronic control unit. 
   In some embodiments, the control network electrically connects the at least one control unit with the first distributed electronic control unit, and the second distributed electronic control unit with the first distributed electronic control unit, and after the signal is received by the first distributed electronic control unit, the first distributed electronic control unit introduces a time delay before relaying the signal to the second distributed electronic control unit. 
   In some embodiments, the at least one central control unit further generates control signals during operation, each control signal including at least one identifier. The control signals are received by the first distributed electronic control unit and the second distributed electronic control unit, and each control signal is acted upon by the first distributed electronic control unit only if that control signal includes the identifier assigned to the first distributed electronic control unit and each control signal is acted upon by the second distributed electronic control unit only if that control signal includes the identifier assigned to the second distributed electronic control unit. 
   In some embodiments, each of the identifiers is indicative of the position of a brake component on a vehicle. In some embodiments, the identifier assignment routine is performed when a vehicle is first started. In certain embodiments, the identifier assignment routine is performed periodically or from time to time. In some embodiments, the identifier assignment routine is performed when the central control unit senses that a distributed electronic control unit has been added to or removed from the control network. In some embodiments, the first distributed electronic control unit and the second distributed electronic control unit are associated with brake components which are actuated by a force selected from the group consisting of an electrical force, a hydraulic force, a pneumatic force and combinations of these. 
   In another embodiment of the present invention, an electronically controlled braking system includes at least one central control unit operable to assign identifiers during an identifier assignment routine, a first pair of distributed electronic control units, a second pair of distributed electronic control units, and a control network electrically connecting the at least one control unit, the first pair of distributed electronic control units, and the second pair of distributed electronic control units. The identifiers include a first identifier, a second identifier, a third identifier and a fourth identifier, with one of the first identifier, the second identifier, the third identifier or the fourth identifier being assigned to each of the distributed electronic control units at least in part based upon the timing of a signal reaching, via the control network, each of the distributed electronic control units. 
   In some embodiments, the control network electrically connects the at least one control unit with the first pair of distributed electronic control units, and the second pair of distributed electronic control units with the first pair of distributed electronic control units, and after the signal is received by the first pair of distributed electronic control units, the first pair of distributed electronic control units introduces a time delay before relaying the signal to the second pair of distributed electronic control units. 
   In some embodiments, the signal is received by the first pair of distributed electronic control units, the first identifier is assigned to one of the first pair of distributed electronic control units and the second identifier is assigned to the other one of the first pair of distributed electronic control units, and after the time delay, the signal is received by the second pair of distributed electronic control units, and the third identifier is assigned to one of the second pair of distributed electronic control units and the fourth identifier is assigned to the other one of the second pair of distributed electronic control units. In some embodiments, the first pair of distributed electronic control units is associated with brake components disposed on a first axle of a vehicle and the second pair of distributed electronic control units is associated with brake components disposed on a second axle of the vehicle. 
   In some embodiments, the at least one central control unit further generates control signals during operation, each control signal including at least one identifier. The control signals are received by each of the distributed electronic control units and each control signal is acted upon by each distributed electronic control unit only if that control signal includes the identifier assigned to that distributed electronic control unit. 
   In some embodiments, each of the identifiers is indicative of the position of a brake component on a vehicle. In some embodiments, the identifier assignment routine is performed when a vehicle is first started. In certain embodiments, the identifier assignment routine is performed periodically or from time to time. In some embodiments, the identifier assignment routine is performed when the central control unit senses that a distributed electronic control unit has been added to or removed from the control network. In some embodiments, the first pair of distributed electronic control units and the second pair of distributed electronic control units are associated with brake components which are actuated by a force selected from the group consisting of an electrical force, a hydraulic force, a pneumatic force and combinations of these. 
   In another embodiment of the present invention, a method of operating an electronically controlled braking system includes the steps of transmitting a signal to a first distributed electronic control unit and a second distributed electronic control unit, and assigning one of a first identifier or a second identifier to the first distributed electronic control unit and assigning the other of the first identifier or the second identifier to the second distributed electronic control unit at least in part based upon the timing of the signal reaching the first distributed electronic control unit and the second distributed electronic control unit. 
   In some embodiments, the signal is transmitted to the second distributed electronic unit through the first distributed electronic control unit, and the method further includes the step of introducing a time delay in the first distributed electronic control unit before relaying the signal to the second distributed electronic control unit. 
   In some embodiments, the method further includes the steps of generating control signals during operation, each control signal including at least one identifier, receiving the control signals with the first distributed electronic control unit and the second distributed electronic control unit, acting upon the control signals with the first distributed electronic control unit only if that control signal includes the identifier assigned to the first distributed electronic control unit, and acting upon the control signals with the second distributed electronic control unit only if that control signal includes the identifier assigned to the second distributed electronic control unit. 
   In some embodiments, each of the identifiers is indicative of the position of a brake component on a vehicle. In some embodiments, the transmitting and assigning steps are performed when a vehicle is first started. In certain embodiments, the transmitting and assigning steps are performed periodically or from time to time. In some embodiments, the transmitting and assigning steps are performed when a distributed electronic control unit has been added to or removed from the braking system. 
   In a further embodiment of the present invention, a method of operating an electronically controlled braking system includes the steps of transmitting a signal to a first pair of distributed electronic control units and a second pair of distributed electronic control units, and assigning one of a first identifier, a second identifier, a third identifier or a fourth identifier to each of the distributed electronic control units at least in part based upon the timing of the signal reaching each of the distributed electronic control units. 
   In some embodiments, the signal is transmitted to the second pair of distributed electronic units through at least one of the first pair of distributed electronic control units, and the method further includes the step of introducing a time delay with the at least one of the first pair of distributed electronic control units through which the signal is transmitted before relaying the signal to the second pair of distributed electronic control units. 
   In some embodiments, the assigning step includes the steps of receiving the signal with the first pair of distributed electronic control units, assigning the first identifier to one of the first pair of distributed electronic control units, assigning the second identifier to the other one of the first pair of distributed electronic control units, receiving, after the time delay, the signal with the second pair of distributed electronic control units, assigning the third identifier to one of the second pair of distributed electronic control units, and assigning the fourth identifier to the other one of the second pair of distributed electronic control units. 
   In some embodiments, the first pair of distributed electronic control units is associated with brake components disposed on a first axle of a vehicle and the second pair of distributed electronic control units is associated with brake components disposed on a second axle of the vehicle. 
   In some embodiments, the method further includes the steps of generating control signals during operation, each control signal including at least one identifier, receiving the control signals with the distributed electronic control units, and acting upon each control signal only with the distributed electronic control unit or units which have been assigned an identifier which matches the at least one identifier included in the control signal. 
   In some embodiments, each of the identifiers is indicative of the position of a brake component on a vehicle. In some embodiments, the transmitting and assigning steps are performed when a vehicle is first started. In certain embodiments, the transmitting and assigning steps are performed periodically or from time to time. In certain embodiments, the transmitting and assigning steps are performed when a distributed electronic control unit has been added to or removed from the braking system. 
   The invention and its particular features and advantages will become more apparent from the following detailed description considered with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic view of an electronically controlled braking system in accordance with an embodiment of the present invention; 
       FIG. 2  is a schematic view of an electronically controlled braking system in accordance with another embodiment of the present invention; and 
       FIG. 3  is a graphical representation illustrating the signal transmission aspect of the electronically controlled braking systems of  FIGS. 1 and 2 . 
   

   DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION 
   Referring to  FIGS. 1 and 2 , an electronically controlled braking system  10 ,  10 ′ in accordance with the present invention is shown. Braking system  10 ,  10 ′ includes at least one central control unit  12  which generates control signals. Braking system  10 ,  10 ′ also includes a plurality of brake components  14 ,  16 ,  18 ,  20 ,  22 ,  24 . While six brake components  14 ,  16 ,  18 ,  20 ,  22 ,  24  are shown in  FIG. 1 , it should be understood that braking system  10 ,  10 ′ may include a greater or lesser number of brake components. It is desirable, although not strictly necessary, that an even number of brake components are provided, and that the brake components are treated as pairs. For example, the brake components associated with the pair of wheels on each axle may be treated as a pair. In  FIG. 1 , first brake component  14  is paired with second brake component  16 , third brake component  18  is paired with fourth brake component  20 , and fifth brake component  22  is paired with sixth brake component  24 . 
   Each of brake components  14 ,  16 ,  18 ,  20 ,  22 ,  24  is responsive to the control signals generated by control unit(s)  12 . More particularly, each of brake components  14 ,  16 ,  18 ,  20 ,  22 ,  24  includes a brake actuator  26  incorporating a distributed electronic control unit  28  which distributed electronic control unit  28  causes brake actuator  26  to operate in response to the control signals. As such electronically controllable brake components are known in the art, a detailed discussion of the operation thereof is not presented herein. Each of brake components  14 ,  16 ,  18 ,  20 ,  22 ,  24  may be actuated by electrical force, hydraulic force, pneumatic force, combinations of these, and/or by any other appropriate force. Braking system  10 ,  10 ′ also includes at least one control network  30  for transmitting control signals from control unit(s)  12  to each of brake components  14 ,  16 ,  18 ,  20 ,  22 ,  24 . 
   The distributed electronic control unit  28  of each brake component  14 ,  16 ,  18 ,  20 ,  22 ,  24  has stored thereon a unique identifier indicative of that brake component&#39;s position on the vehicle, and each of the control signals generated by control unit(s)  12  and transmitted over control network  30  includes an identifier indicative of the brake component or components which that particular control signal is intended to control. The distributed electronic control unit  28  of each brake component  14 ,  16 ,  18 ,  20 ,  22 ,  24  is only responsive to control signals which include the unique identifier associated therewith. For example, first brake component  14  may be assigned identifier ID 1 , second brake component  16  may be assigned identifier ID 2 , third brake component  18  may be assigned identifier ID 3 , fourth brake component  20  may be assigned identifier ID 4 , fifth brake component  22  may be assigned identifier ID 5 , and sixth brake component  24  may be assigned identifier ID 6 . Each of these identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  is stored on the distributed electronic control unit  28  of each respective brake component  14 ,  16 ,  18 ,  20 ,  22 ,  24 . In this example, although the distributed electronic control unit  28  of first brake component  14  would receive all control signals generated and transmitted by central control unit(s)  12 , it would be responsive only to control signals which include the identifier ID 1 . All control signals not including the identifier ID 1  would be ignored. Of course, a control signal may include more than one identifier, in which case the distributed electronic control unit  28  of more than one brake component would be responsive thereto. 
   Identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  are assigned to and stored on the distributed electronic control unit  28  of each respective brake component  14 ,  16 ,  18 ,  20 ,  22 ,  24  automatically by control unit(s)  12 . More specifically, at commencement of an identifier assignment routine, identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  are transmitted by central control unit(s)  12  over control network  30  to each of brake components  14 ,  16 ,  18 ,  20 ,  22 ,  24 . The determination of which identifier ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  is to be assigned to (i.e., stored on) which brake component  14 ,  16 ,  18 ,  20 ,  22 ,  24  is at least partially dependent upon the time it takes identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  to reach the distributed electronic control unit  28  associated with each brake components  14 ,  16 ,  18 ,  20 ,  22 ,  24 , such signal travel time being reflective of the position of each brake component  14 ,  16 ,  18 ,  20 ,  22 ,  24  on the vehicle. 
   In the embodiments of system  10 ,  10 ′ shown in  FIGS. 1 and 2 , the identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  are assigned in pairs on a per axle basis, with a time delay TD 1 , TD 2  being introduced at each axle. Of course, it may not be necessary for a time delay to be introduced at the last axle (i.e., the one furthest from central control unit(s)  12  along control network  30 ), since there are no further identifiers to be assigned after this last axle. It may also be possible that brake components  14 ,  16 ,  18 ,  20 ,  22 ,  24  not be treated as pairs (i.e., on a per axle basis), and that they each be connected through control network  30  in series. In this instance, it may be desirable to introduce time delays at each brake component (with the possible exception of the last brake component), rather than at each axle. 
   Thus, in the embodiments of system  10 ,  10 ′ shown in  FIGS. 1 and 2 , central control unit(s)  12  transmits identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  via control network  30  at the commencement of an identifier assignment routine. The first two identifiers ID 1 , ID 2  are assigned to (i.e., stored on) the distributed electronic control units  28  of first and second brake components  14 ,  16 , and a first time delay TD 1  is introduced. After the time delay TD 1 , the third and fourth identifiers ID 3 , ID 4  are assigned to the distributed electronic control units  28  of third and fourth brake components  18 ,  20 , and a second time delay TD 2  is introduced, after which fifth and sixth identifiers ID 5 , ID 6  are assigned to the distributed electronic control units  28  of fifth and sixth brake components  22 ,  24 . The particular manner in which each pair identifiers are assigned to each pair of brake components on each axle may vary, with a different exemplary embodiment being shown in each of  FIGS. 1 and 2 . 
   Referring particularly to  FIG. 1 , the control network  30  of system  10  essentially divides off to each brake component forming each pair of brake components before reaching the distributed electronic control units  28  thereof. For example, it can be seen that control network  30 , before reaching the distributed electronic control units  28  of first and second brake components  14 ,  16 , splits off such that identifiers ID 1 , ID 2  are received separately by the distributed electronic control units  28  of and second brake components  14 ,  16 . It can also be seen that the distance the identifiers ID 1 , ID 2  must travel to reach the distributed electronic control unit  28  of second brake components  16  is greater than the distance the identifiers ID 1 , ID 2  must travel to reach the distributed electronic control unit  28  of first brake components  14 . As such, identifiers ID 1 , ID 2  reach the distributed electronic control unit  28  of first brake components  14  slightly sooner than they reach the distributed electronic control unit  28  of second brake components  16 . 
   As such, it is known that the identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  will reach the distributed electronic control unit  28  of first brake components  14  before any others, and ID 1  is assigned and stored on the distributed electronic control unit  28  of first brake component  14 . It is also known that the identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  will reach the distributed electronic control unit  28  of second brake components  16  second, and ID 2  is assigned and stored on the distributed electronic control unit  28  of second brake component  16 . First time delay TD 1  is introduced at the first axle (more particularly by the distributed electronic control unit  28  of first brake component  14 ), before the identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  are passed on to third, fourth, fifth and sixth brake components  18 ,  20 ,  22 ,  14 . Identifiers ID 3 , ID 4  are assigned to third and fourth brake components  18 ,  20  in a similar manner as identifiers ID 1 , ID 2  were assigned to first and second brake components  14 , 16 , second time delay TD 2  is introduced at the second axle (more particularly by the distributed electronic control unit  28  of third brake component  18 ), and identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  are passed on to fifth and sixth brake components  22 ,  14 , to which identifiers ID 5  and ID 6  are assigned. 
   The importance of introducing first and second time delays TD 1 , TD 2  will now be discussed. Because identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  are assigned based upon the order in which they are received by the distributed electronic control unit  28  of each brake component  14 ,  16 ,  18 ,  20 ,  22 ,  24 , it is important to ensure that the identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  are received by brake components  14 ,  16 ,  18 ,  20 ,  22 ,  24  in the proper temporal sequence (i.e., received first by first brake component  14 , received second by second brake component  16 , received third by third brake component  18 , etc.). If no time delays were introduced, it may be possible for this temporal sequence to become confused. For example, if second brake component  16  and third brake component  18  were located a similar distance from central control unit(s)  12 , and first time delay TD 1  were not introduced, identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  may reach second brake component  16  and third brake component  18  at substantially the same time. In this case, system  10  may not be able to properly determine which brake component should be assigned identifier ID 2  and which should be assigned identifier ID 3 . The introduction of first and second time delays TD 1 , TD 2  prevents this from occurring. Of course, the duration of first and second time delays TD 1 , TD 2  should be selected to ensure that the identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  will always reach the brake components  14 ,  16 ,  18 ,  20 ,  22 ,  24  in the proper order under normal operating conditions. 
   Referring particularly now to  FIG. 2 , the control network  30 ′ of system  10 ′, rather than dividing off to each brake component forming each pair of brake components before reaching the distributed electronic control units  28  thereof as is the case with system  10  of  FIG. 1 , is directly connected only to the distributed electronic control unit  28  of one of each pair of brake components. For example, in system  10 ′ it can be seen that control network  30 ′, is directly connected the distributed electronic control unit  28  of first brake component  14 , but not to the distributed electronic control unit  28  of second brake component  16 . 
   This embodiment functions in substantially the same way as system  10  shown in  FIG. 1 , with the exception that the distributed electronic control units  28  of first brake component  14 , third brake component  18  and fifth brake component  22  receive identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  and pass them on to second brake component  16 , fourth brake component  20  and sixth brake component  24  respectively, rather than the identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  being transmitted directly thereto. The timing aspects of system  10 ′, including the introduction of time delays TD 1 , TD 2 , are substantially the same as in system  10 . 
   The operation of systems  10 ,  10 ′ is shown graphically in  FIG. 3 . More specifically, the graph illustrates when identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  reach each of brake components  14 ,  16 ,  18 ,  20 ,  22 ,  24 , and further illustrates where first and second time delays TD 1 , TD 2  are introduced. In the graph, first brake component  14  is represented by the line labeled BC 1 , second brake component  16  is represented by the line labeled BC 2 , and so on. Thus, by knowing the particular timing when each of the six identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  reaches each of the six brake components  14 ,  16 ,  18 ,  20 ,  22 ,  24 , identifier assignments can be easily made. 
   Rather than central control unit  12  unilaterally assigning identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  to each of brake components  14 ,  16 ,  18 ,  20 ,  22 ,  24 , identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  may be assigned based upon bi-lateral communications between central control unit  12  and the distributed electronic control unit  28  of each brake component  14 ,  16 ,  18 ,  20 ,  22 ,  24 . In one preferred embodiment, an electronic startup signal is transmitted by central control unit  12  at vehicle startup, periodically or from time to time thereafter and/or upon the occurrence of certain events (as described more fully above and below). This startup signal activates (e.g. “wakes up”) the distributed electronic control unit  28  of each brake component  14 ,  16 ,  18 ,  20 ,  22 ,  24 . 
   When the distributed electronic control units  28  of first and second brake components  14 ,  16  (i.e., the brake components on the first axle) receive the startup signal they will “listen” to the communication on the control network  30  (at this stage listening only for the central control unit  12  asking for the distributed electronic control units  28  of the brake components  14 ,  16 ,  18 ,  20 ,  22 ,  24  to reply), and if no other brake components are detected on the control network  30  they will know that they are to be assigned ID 1  and ID 2  respectively in the system and the will then reply the central control unit  12  indicating such. 
   After a defined time delay TD 1  the startup signal will be sent on to the distributed electronic control units  28  of the third and fourth brake components  18 ,  20  (i.e., the brake components on the second axle). When third and fourth brake components  18 ,  20  “listen” to the communication on control network  30 , they will determine that there are brakes named ID 1  and ID 2  replying to the central control unit  12  on the control network  30 . As such, they will then assign themselves ID 3  and ID 4  respectively and reply to the central control unit  12  indicating such. 
   After a defined time delay TD 2  the startup signal will be sent on to the distributed electronic control units  28  of the fifth and sixth brake components  22 ,  24  (i.e., the brake components on the third axle). When fifth and sixth brake components  22 ,  24  “listen” to the communication on control network  30 , they will determine that there are brakes named ID 1 , ID 2 , ID 3  and ID 4  replying to the central control unit  12  on the control network  30 . As such, they will then assign themselves ID 5  and ID 6  respectively and reply to the central control unit  12  indicating such. This process is repeated for any further brake components attached to control network  30 . 
   As discussed above, identifiers ID 1 , ID 2 , ID 3 , ID 4 , ID 5 , ID 6  are assigned at commencement of an identifier assignment routine. This preferably occurs when the vehicle&#39;s ignition system is activated at vehicle start up. However, the identifier assignment routine may additionally be commenced periodically or from time to time thereafter, or upon the occurrence of a particular event. For example, the identifier assignment routine may be commenced when it is sensed that a brake component is added to or removed from the vehicle, such as during servicing, or it may be commenced when a trailer having brake components is added to or removed from the control network  30 . 
   In addition to controlling standard braking operations, control unit(s)  12  may control various additional braking functions, such as antilock brake systems (ABS) and electronic braking force distribution (EBV) systems, as well as other vehicle systems, such as vehicle suspension and dynamic stability systems. In such cases, these additional vehicle systems may have identifiers associated therewith as described above. Moreover, the startup signal discussed above can be replaced by a simple “single wire network” and be additionally used for a gradual parking brake application. The advantage of this is that the system then has an independent (i.e., isolated from the control network  30 ) way of applying a parking brake condition, which results in a safer system architecture. 
   The present invention, therefore, provides an electronically controlled braking system intended for use with wheeled vehicles which incorporates distributed electronic control units, which allows for the control of each individual brake component or each group of brake components associated with each distributed electronic control unit independently of those associated with other distributed electronic control units, which allows for control signals intended for controlling only one brake component or group of brake components to be differentiated from those control signals intended for controlling another brake component or group of brake components, which does not require that the distributed electronic control unit be manually programmed or reprogrammed each time a distributed electronic control unit is replaced and/or its location in the system is changed, and which employs an identification scheme, the implementation of which is not time-consuming and/or does not require additional knowledge on the part of service technicians who service the brake system. 
   Although the invention has been described with reference to a particular arrangement of parts, features and the like, these are not intended to exhaust all possible arrangements or features, and indeed many other modifications and variations will be ascertainable to those of skill in the art.