System and method allowing for determining relative positions of slave units along a stub bus

The present application relates to a system and a method for determining relative positions slave units along a stub bus with at least a power line and a ground line. Each slave unit is operable in different power modes, which are differentiated by effective resistances between the power and ground lines. A reference voltage potential drop is determined for each slave unit while the slave units are operating in a first power mode. A positioning voltage potential drop is determined for one or more slave units while a selected slave unit is operating in a second power mode. Relative positions of the slave units are determined based on the relative voltage potential drops obtained from the reference and positioning voltage potential drops.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority under 35 U.S.C. § 119 of European Patent application No. 17177251.0, filed on Jun. 21, 2017, the contents of which are incorporated by reference herein.

FIELD OF THE INVENTION

The present disclosure relates generally to the field of bus systems comprising a control unit, a bus connected to the control unit, and a plurality of addressable participants connected to the bus. More in particular, the invention relates to a method for addressing the control unit participating in the communication on the bus system and to such a bus system.

BACKGROUND

For minimizing the wiring complexities, it is common practice to transmit control signals for electronic control unit via a bus, to which, besides a central unit, the electric control units are connected as individually addressable participants. In vehicle applications, such wired based bus systems may be for instance used for the actuator and/or sensor based control units of a vehicle air conditioner, a window lift, front seats or ultrasonic distance measuring sensors just to mention a limited number of exemplary use cases. To enable the central unit to selectively communicate to one or to a plurality of control units participating on a bus system, addresses are assigned to said control units. Typically, several control units with the same functionality. Such functional identical control units are only individualized by the unique addresses on the bus systems, to which the functional identical control units are connected.

In the state of the art, various procedures and processes are known to assign addresses to control units on a bus system. Such addresses may be assigned to the control units participating on a bus in that they are stored by programming, assigned via daisy chain, plug or PIN coding, or by sequential connection of the control units and allocation of the addresses after connection of a control unit.

SUMMARY

The present invention provides a method for determining relative positions of a plurality of slave units and a system allowing to determine relative positions of a plurality of slave units as described in the accompanying claims. Specific embodiments of the invention are set forth in the dependent claims. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described below in detail with reference to drawings. Note that the same reference numerals are used to represent identical or equivalent elements in figures, and the description thereof will not be repeated. The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the invention. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the invention and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims.

In modern vehicles, various bus systems may be used. For example, these are CAN (Controller Area Network), Flexray and the LIN (Local Interconnect Network), also referred to LIN bus. The LIN is a communication system, which was developed for the communication of intelligent sensors and actors in vehicles at low cost, is based on a single wire bus and may be classified as a field bus. A typical application scenario is the networking within a vehicle door, of a seat, of air conditioning flaps or the various light sources of an interior lighting system. LIN is typically applied where the higher bandwidth and the higher versatility of CAN is not required. The LIN specification includes the LIN protocol, a unified format for the description of the overall LIN and the interface between a LIN and the respective application.

Referring now toFIG. 1, block diagrams of variants of a communication network with stub bus according to examples of the present application are schematically illustrated.

In one example, the illustrated communication network is a Local Interconnect Network (LIN). A LIN is composed of a master unit100, which may be also referred to as central control unit, one or more slave units200.1to200.n, which may be also referred to as nodes or node units, and a bus. The master unit100is for instance a central controller in a vehicle, such as for controlling the lighting and/or the air conditioning in the vehicle, such as a HVAC (Heating, Ventilation and Air conditioning) controller or a BCM (Body Control Module) of a vehicle. The slave units for example include a controller and an LED (light emitting diode), a controller and an air conditioning flap, a controller and an actuator or a controller and a sensor.

The master unit100is connected to a multi-wire bus, e.g. a two-wire bus. The bus50is a stub bus. The slave units200.1to200.nare connected along the bus50. The arrangement/position of the slave units200.1to200.nalong the bus50will be described in the following from the perspective of the master unit100, starting from which the slave units200.1to200.nare connected to the bus in consecutive arrangement in downstream direction. For the sake of understanding, the relative arrangement/position of the slave unit200.iwill be described as being upstream to the slave unit200.i+1 and the relative arrangement/position of the slave unit200.i+1 will be described as being downstream to the slave unit200.i. The “first” slave unit along the bus50is the slave unit200.1and the “last” slave unit along the bus50is the slave unit200.n, wherein n is a positive integer. An arbitrary slave unit from among the slave units200.1to200.nis referred to as slave unit200.i, wherein 1≤i≤n.

The bus50comprises at least a power supply line30and a ground line40, to which the slave units200.1to200.nare connected.

A data communication channel20is established between the master unit100and the slave units200.1to200.n. In regular operation, the master unit100(acting as a bus master) has knowledge about and control over the scheduling of the communication between the master unit100and slave units200.1to200.n. A slave unit110(the reference number110refers to any one of the reference numbers200.1to200.n) may transmit data upon when the master unit100has requested it to do that. The master unit100may request the data transmission by sending a header, which is marked with an address specific of the requested slave unit200.ion the bus. In response, the addressed node200.isupplies the data to be transmitted to the bus. Each node200.1to200.nhas a network specific address, via which it is addressed by the master unit100.

The network specific addresses are assigned in the auto-addressing procedure, which, for instance, is carried out once in case at least one slave unit without network specific address is connected to the bus for the first time. In particular, the auto-addressing procedure is carried out after the assembly of the communication network and/or at initial operation of the units arranged to form the communication network. Further, the auto-addressing procedure may be carried out on a regular basis, e.g. each time a unit of the communication network is put into operation.

For performing the auto-addressing procedure, each of the slave units200.1to200.nare addressable by the master unit100using a unit specific identifying address, or unit identifier UID, herein referred to as UID1, UID2, . . . UIDn assigned to the respective one of the slave units200.1to200.n. The unit identifier UID is for instance embedded within a slave unit at the manufacturing stage for use during auto-addressing procedure. The embedded unit identifier UID is unique to allow for distinguishing between functional identical slave units. It is immediately understood that such embedded unit identifiers UIDs are not applicable for regular operation but for performing communication between the master unit100and the slave units200.1to200.nduring performing the auto-addressing procedure.

The master unit100is arranged to discover the unit identifiers UIDs of the slave units200.1to200.nconnected to the bus50. Such discovery process is known in the art. In an example, the master unit100performs a binary search for the unit identifiers UIDs of the connected slave units200.1to200.n. In another example, the master unit100may request to slave unit200.1to200.nto transmit their unit identifiers UIDs. The unit identifiers UIDs of the slave units200.1to200.nare provided e.g. in form of a list105, at the master unit100.

The auto-addressing procedure according to an embodiment of the present application is based on determining the individual cable resistances of the bus line sections between the master unit100and the slave units200.1to200.n. An individual cable resistance is indicative of the length of the bus lines30,40between the master unit100and a respective one of the slave units200.1to200.n. The relative arrangement/positions of the slave units200.1to200.nalong the bus50can be determined from a comparison of the individual cable resistances determined for each of the slave units200.1to200.n.

As schematically illustrated inFIG. 1, an equivalent resistor Rccan be used for describing the cable resistances between two adjacent units100,200.1to200.n. Those skilled in the art are aware that a cable resistance is a function of the length. From the following description, the skilled person will appreciate that the simplifying assumption of a constant cable resistance between two adjacent units100,200.1to200.ndoes not limit the teaching of the present application thereto but is made merely for the sake of intelligibility and understanding. In particular, the auto-addressing procedure disclosed in the present application is based on a basic concept for reliably determining the cable resistances between the master unit100and the slave units200.1to200.n, based on which the relative positioning of the slave units200.1to200.nalong the bus50can be deduced.

In the example shown inFIG. 1a, the illustrated communication network uses power line communication for communicating data between the master unit100and the slave units200.1to200.n. The data signal is for instance carried on the power supply line30connecting the master unit100and the slave units200.1to200.n. In the example shown inFIG. 1b, the illustrated communication network uses one or more dedicated data line(s) between the master unit100and the slave units200.1to200.nfor communicating data signal between them. For instance, the data signals communicated between the connected units100,200.1and200.nmay be carried on a single wire or on a two-wire twisted pair for differential signaling. It should be noted that the auto-addressing procedure according to embodiments described in the following is applicable with both illustrated communication networks but not limited thereto.

The auto-addressing procedure according to an embodiment of the present application will be further described with regard toFIG. 2, which schematically illustrates a flow diagram of a method for determining the relative arrangement/position of slave units along a stub bus of a communication network. The auto-addressing procedure is controlled by the master unit, which is arranged at one end of the stub bus, to which an arbitrary number of slave units is connected. The auto-addressing procedure will be further described with reference toFIG. 3a, which schematically illustrates a block diagram of a master unit100, and with reference toFIG. 3b, which schematically illustrates a block diagram of any slave unit200.1to200.n.

The master unit100according to an example of the present application as exemplified inFIG. 3acomprises a voltage adjustable power source130and a transceiver150for communication network using power line communication on a two wire stub bus for data communication between the master unit100and slave units200.1to200.nconnected to the stub bus. The master unit100further comprises a control section110, which is connected to the transceiver for instructing the slave units200.1to200.nand receiving measurement data from the slave units200.1to200.n, a measurement data analyzer section120and at least a list of slave units105and106for maintaining information about the slave units200.1to200.n.

Each slave unit200.1to200.naccording to an example of the present application as exemplified inFIG. 3ais instructable by the master unit100to operate in a low-power mode and a high-power mode. A slave unit being instructed to operate in the low-power mode, draws a low-power current from the power supply line, which is smaller than a high-power current, which is drawn by the slave unit being instructed to operate in the high-power mode. The low-power mode is schematically illustrated by a switchable resistor RL210and the high-power mode is schematically illustrated by a switchable resistor RH220. The switchable resistors RL210and RH220illustrate the effective resistances of the slave units200.1to200.nacross which the voltage potential drops are measured in the respective (low and high) power modes. The resistor RL210should be understood to have a higher effective resistance than the resistor RH220.

Each slave unit200.1to200.nfurther comprises a transceiver250for receiving instructions from the master unit100and transmitting measurement related data to the master unit100. Each slave unit200.1to200.nis further provided with a voltage potential drop measurement unit240, which is arranged to detect a voltage potential drop between a power supply line connector and a ground line connector. The voltage potential drop measurement unit240is further connected to the transceiver120for reporting the measurement related data to the master unit100.

Referring back toFIG. 2, a list of slave units connected to the bus is provided/maintained at a master unit100, in an operation S100. The list of slave units comprises all slave units connected to the bus. Initially, the arrangement/positions of slave units along the bus is/are unknown. A slave unit, which arrangement/position along the bus is unknown, will be referred to as undetected or “unpositioned”.

In operations S110and S115, the slave units are instructed by the master unit100to enter the low-power mode and the slave units are further instructed by the master unit100to each measure a reference voltage potential drop between the power supply line connector and the ground line connector during operating in low-power mode.

In an operation S120, a slave unit is randomly selected from the list of undetected slave units.

In operations S130and S135, the selected slave unit is instructed by the master unit100to enter the high-power mode and the slave units are further instructed by the master unit100to each measure a positioning voltage potential drop between the power supply line connector and the ground line connector during the selected slave unit operating in high-power mode and the remaining slave units operating in low-power mode.

In an operation S140, a relative voltage potential drop is determined by each slave unit on the basis of the measured reference and positioning voltage potential drop.

In an operation S150, the master unit requests the slave units to report the determined relative voltage potential drops, in response to which each slave unit transmits the determined relative voltage potential drops together with its unique identifier (UID), which enables the master unit to associate each determined relative voltage potential drop with a specific slave unit having assigned a respective UID. The determined relative voltage potential drops reported by the slave units are collected at the master unit in an operation S160. Based on the collected relative voltage potential drops, the master unit determines relative positions of at least a set of the slave units based on the relative levels of the collected relative voltage potential drops in an operation S170.

In an operation S180, the list of undetected slave units is updated with respect to the set of slave units, of which the relative positions along the stub bus have been determined on the basis of the relative levels of the collected relative voltage potential drops. For instance, slave units with now known position/arrangement along the stub bus are removed from the list or indicated to be ignored for the further process of the auto-addressing procedure.

In an operation S190, the master unit determines whether or not remaining slave units with unknown position/arrangement are still present. If there are remaining undetected slave units, the auto-addressing procedure returns to the operation S110. Otherwise, if the position/arrangement of all slave units connected to the stub bus is determined, the auto-addressing procedure is completed.

The reference voltage potential drop measurement performed at the slave units200.1to200.nwill be more fully described with reference toFIG. 4, which schematically illustrates a block diagram of a communication network with slave units operating in low-power mode according to an example of the present application.

As described above, the master unit instructs all slave units connected to the stub bus to enter the low-power mode, in which reference voltage potential drops are determined by each of the slave units200.1to200.n.

The reference voltage potential drop V1ref, which is measured by the slave unit200.1can be determined as follows:
VS≈Rc·n·IL+V1ref+Rc·n·IL
=2·Rc·n·IL+V1ref
wherein Vsis the voltage supplied by the voltage controlled adjustable source130, Rcis the resistance of a line section of the power supply line or the ground line between two neighboring units (e.g. between the master unit100and the first slave unit200.1or between neighboring slave unit200.iand200.i+1), ILis the current flowing through the slave unit200.1, and n is the number of slave units200.1to200.n.

Without loss of generality, it is assumed that the bus line resistance Rcis substantially the same for all line sections. Without loss of generality, it is further assumed that the effective resistance RL220of the slave units200.1to200.nin low-power mode is high, which results in a low current being substantially the same for all slave units200.1to200.nalong the stub bus.

The reference voltage potential drop V2ref, which is measured by the slave unit200.2, can be determined as follows:
VS≈Rc·n·IL+Rc·(n−1)·IL+V2ref+Rc·(n−1)·IL+Rc·n·IL
=2·Rc·(n+n−1)·IL+V2ref

The reference voltage potential drop V3ref, which is measured by the slave unit200.3, can be determined as follows:
VS≈Rc·n·IL+Rc·(n−1)·IL+Rc·(n−2)·IL+V3ref+Rc·(n−2)·IL+Rc·(n+1)·IL+Rc·n·IL
=2·Rc·(n+n−1+n−2)·IL+V3ref

In general, the reference voltage potential drop Viref, which is measured by the slave unit200.i, where 1≤i≤n and i is a position index starting at the first slave unit200.1arranged downstream the master unit200and ending with the last slave unit200.nhaving the maximum distance from the master unit200, can be determined as follows:

The positioning voltage potential drop measurement performed at the slave units200.1to200.nwill be more fully described with reference toFIG. 6, which schematically illustrates a block diagram of a communication network with a slave unit operating in high-power mode and the remaining slave units operating in low-power mode according to an example of the present application.

As described above, the master unit instructs selected slave unit connected to the stub bus to enter the high-power mode and the remaining slave units connected to the stub bus to enter low-power mode and the master unit instructs each of the slave units200.1to200.noperating in the respectively instructed power mode to determine positioning voltage potential drops.

The selected slave unit is an arbitrarily selected slave unit out of the list of undetected slave units. For the sake of explanation, the slave unit200.2is assumed to be selected. Respective switching states of the slave units are schematically illustrated inFIGS. 5aand 5b.FIG. 5aschematically illustrates a block diagram of a slave unit operating in the low-power mode according to an example of the present application.FIG. 5bschematically illustrates a block diagram of a slave unit operating in the high-power mode according to an example of the present application.

The reference voltage potential drop V1pos, which is measured by the slave unit200.1, can be determined as follows:
VS≈Rc·(n−1)·IL+Rc·IH+V1pos+Rc·(n−1)·IL+Rc·IH
=2·Rc·(n−1)·IL+2·Rc·IH+V1pos
wherein Vsis the voltage supplied by the voltage adjustable power source130, Rcis the resistance of a line section of the power supply line or the ground line between two neighboring units, and ILis the current flowing through the slave units200.1and200.3to200.n, which are operating in low-power mode, IHis the current flowing through the slave unit200.2, which is operating in high-power mode, and n is the number of slave units200.1to200.n.

Without loss of generality, it is assumed that the bus line resistance Rcis substantially the same for all line sections. Without loss of generality, it is further assumed that the effective resistance RL220of the slave units200.1and200.3to200.nin low-power mode is high in comparison to the effective resistance RH201of the slave unit200.2, which results in a low current being substantially the same for slave units200.1and200.3to200.noperating in low-power mode.

The reference voltage potential drop V2pos, which is measured by the slave unit200.2, can be determined as follows:
VS≈Rc·(n−1)·IL+Rc·IH+Rc·(n−2)·IL+Rc·IH+V2pos+Rc·(n−2)·IL+Rc·IH+Rc·(n−1)·IL+Rc·IH
=2·Rc·(n−1+n−2)·IL+4·Rc·IH+V2pos

In general, the slave unit200.kmay be selected, where 1≤k≤n, and n is the total number of slave units200.1to200.nand the slave unit200.p. The reference voltage potential drop Vppos, which is measured by the slave unit200.p, where 1≤p≤k, can be determined as follows:

The reference voltage potential drop V3pos, which is measured by the slave unit200.3, can be determined as follows (wherein the selected slave is the slave200.2, where k=2):
VS≈Rc·(n−1)·IL+Rc·IH+Rc·(n−2)·IL+Rc·IH+Rc·(n−2)·IL+V3+Rc·(n−2)·IL+Rc·(n−2)·IL+Rc·IH+Rc·(n−1)·IL+Rc·IH
=2·Rc·(n−1+n−2+n−2)·IL+4·Rc·IH+V3pos

In general, the slave unit200.kmay be selected, where 1≤k≤n and n is the total number of slave units200.1to200.n. The reference voltage potential drop Vqpos, which is measured by the slave unit200.q, where k+1≤q≤n, can be determined as follows:

The determining of the relative voltage potential drop by each of the slave units200.1to200.nwill be more fully understood with reference toFIG. 7, which schematically illustrates a block diagram of a communication network with a selected slave unit operating in high-power mode and the remaining slave units operating in low-power mode according to an example of the present application and a diagram schematically illustrating the course of determined positioning voltage potential drops in accordance with the exemplified power modes, in which the slave units operate.

The relative voltage potential drop ΔV is determined based on the reference voltage potential drop and the positioning voltage potential drop each of which measured by each of the slave units200.1to200.n.

The reference voltage potential drop Viref, which is measured by the slave unit200.i, where 1≤i≤n, can be expressed as follows:

In general, the slave unit200.kmay be selected, where 1≤k≤n.

The positioning voltage potential drop Vipos, which is measured by the slave unit200.i, where k is the selected slave unit200.k,1≤k≤n and n is the number of slave units200.1to200.n, can be determined as follows:

The above relation is exemplarily shown in the diagram ofFIG. 7, which schematically illustrates the course of the positioning voltage potential drop Viposwith respect to the slave unit200.2being the selected slave unit. In particular, it may be assumed that IL<<IH.

The relative voltage potential drop ΔViis obtained by determining a difference of the measured voltage potential drops as follows:

This means that

Δ⁢⁢Vi={2·i·Rc·(IH-IL)1≤i≤k2·k·Rc·(IH-IL)k+1≤i≤n
and

Δ⁢⁢Vi≈{2·i·Rc·IH1≤i≤k2·k·Rc·IHk+1≤i≤n
when assuming that IH>>IL.

Δ⁢⁢Vi∼{i·Rc1≤i≤kk·Rck+1≤i≤n
wherein k is a constant for each measurement cycle. Therefore, the relative positions/arrangement of the slave units200.1to200.k(1≤i≤k) can be determined by analyzing the levels of the relative voltage potential drop ΔVi, which is substantially proportional to the position index i.

As the skilled person may understand from the above description, the resistance of the power supply line and/or the ground line may be substantially low. As shown above with respect to the above example, the relative positions/arrangement of the slave units200.i(1≤i≤n) can be determined by analyzing the levels of the relative voltage potential drop ΔVi, which is in turn substantially proportional to the resistance Rc, which denotes the resistance of a line section of the power supply line or the ground line between two neighboring units (e.g. between the master unit100and the first slave unit200.1or between neighboring slave unit200.iand200.i+1).

This means that the higher the resistance Rcthe more distinct are the levels of the relative voltage potential drop ΔViobtained from the measured voltage potential drops. The integration of a shunt resistance to increase the resistance of the power supply line or the ground line enables increasing the level distances.

Referring toFIG. 8now, each slave unit200.iaccording to an example of the present application comprises a shunt resistance Rs, which is for instance arranged in series with the power line. The shunt resistance Rsis arranged downstream to the effective resistances, across which the voltage potential drops are measured. Accordingly, the slave unit200.ihas an input terminal and an output terminal for connecting to the power line. The shunt resistance Rsis connected between the input terminal and the output terminal. Alternatively or additionally, a shunt resistance Rsmay be arranged in series with the ground line (not shown). The statements above with respect to the shunt resistance Rsconnected in series with the power line apply analogously to a shunt resistance Rsconnected in series with the ground line.

Referring now toFIG. 9a, the reference voltage potential drop Viref, which is measured by the slave unit200.i, where 1≤i≤n and i is a position index starting at the first slave unit200.1arranged downstream the master unit200and ending with the last slave unit200.nhaving the maximal distance from the master unit200, can be determined as follows:

Referring now toFIG. 9b, the reference voltage potential drop Vppos, which is measured by the slave unit200.p, where 1≤p≤k, can be determined as follows:

The reference voltage potential drop Vqpos, which is measured by the slave unit200.q, where k+1≤q≤n, can be determined as follows

where slave unit200.kis selected to operate in high-power mode, where 1≤k≤n and n is the total number of slave units200.1to200.n.

The relative voltage potential drop ΔViis obtained by determining a difference of the measured voltage potential drops as follows:

Δ⁢⁢Vi∼{i·(Rc+12⁢Rs)1≤i≤kk·(Rc+12⁢Rs)k+1≤i≤n
where 1≤i≤k, and

This means that

Δ⁢⁢Vi=Viref-Vipos=2·k·(Rc+12⁢Rs)·(IH-IL)
and

Δ⁢⁢Vi={2·i·(Rc+12⁢Rs)·(IH-IL)1≤i≤k2·k·(Rc+12⁢Rs)·(IH-IL)k+1≤i≤n
when assuming that IH>>IL.

Δ⁢⁢Vi≈{2·i·(Rc+12⁢Rs)·IH1≤i≤k2·k·(Rc+12⁢Rs)·IHk+1≤i≤n
wherein k is a constant for each measurement cycle.

The shunt resistance increases the distance between the levels of the relative voltage potential drop ΔVi.

It should be noted that the above exemplified auto-addressing procedures may be performed using the voltage adjustable power source130supplying a direct current or an alternating current having in particular a predefined frequency. In the latter case, the voltage measurement is performed at the slave units200.1to200.nwith respect to the predefined frequency of the alternating current supplied by the voltage adjustable power source130. More particularly, the voltage potential drop measurements in high-power mode may be performed using alternating current. The use of an alternating current supplied by the voltage adjustable power source130may be more robust regarding noise and disturbance signals and may further reduce the requirements for measuring accuracy of the circuitry for measuring the voltage potential drops including in particular the voltage potential drop measurement unit240. The above teaching enables the skilled person to implement the above exemplified auto-addressing procedures using direct current or alternating current supplied by the current adjustable power source135.

The auto-addressing procedure according to another embodiment of the present application will be further described with regard toFIG. 10, which schematically illustrates a flow diagram of a further method for determining the relative arrangement/position of slave units along a stub bus of a communication network. The auto-addressing procedure is controlled by the master unit, which is arranged at one end of the stub bus, to which an arbitrary number of slave units is connected. The auto-addressing procedure will be further described with reference toFIG. 11a, which schematically illustrates a block diagram of a master unit100according to an example of the present application, and with reference toFIGS. 11bto 11d, which schematically illustrates a block diagram of any slave unit200.1to200.naccording to an example of the present application.

The master unit100according to an example of the present application as exemplified inFIG. 11acomprises a current adjustable power source135and a transceiver150for communication network on a two wire stub bus for data communication between the master unit100and slave units200.1to200.nconnected to the stub bus. The master unit100further comprises a voltage potential drop measurement unit140, a control section110, which is connected to the transceiver for instructing the slave units200.1to200.n, a measurement data analyzer section120and at least a list of slave units105for maintaining information about the slave units200.1to200.n.

Each slave unit200.1to200.naccording to an example of the present application as exemplified inFIGS. 11bto 11dis instructable by the master unit100to operate in a low-power mode, a first high-power mode and a second high-power mode. A slave unit being instructed to operate in the low-power mode, draws a low-power current from the power supply line, which is smaller than high-power currents, which are drawn by the slave unit being instructed to operate in one of the high-power modes. The switchable effective resistances of the slave units200.1to200.ndiffers in the different power modes. The voltage potential drops are measured across the different effective resistances switchable in accordance with the respective (low, first high and second high) power modes.

In an example, the low-power mode is schematically illustrated by a switchable resistor RL210as schematically shown inFIG. 11b. The first high-power mode is schematically illustrated by a switchable interconnection220of two resistor RHin a parallel circuit as schematically shown inFIG. 11c. The second high-power mode is schematically illustrated by a switchable interconnection230of the two resistor RHin an in-series circuit as schematically shown inFIG. 11d. The resistor RL210should be understood to have a higher effective resistance than the resistor RH220. The first and the second high-power modes have a fixed effective resistance ratio of 4. Each slave unit200.1to200.nfurther comprises a transceiver250for receiving instructions from the master unit100.

Referring back toFIG. 10, a list of slave units connected to the bus is provided/maintained at a master unit100, in an operation S300. The list of slave units comprises all slave units connected to the bus. Initially, the arrangement/positions of slave units along the bus is/are unknown. A slave unit, which arrangement/position along the bus is unknown, will be referred to as undetected or “unpositioned”.

In an operation S305, an undetected slave unit is selected from the list of slave units.

In an operation S310, the all slave units except the selected one are instructed by the master unit100to enter the low-power mode and the selected slave unit is instructed by the master unit100to enter the first high-power mode.

In an operation S315, a predefined current Isis driven by the current adjustable power source135on the power line of the bus. The current adjustable power source135may be controlled by the master unit100to drive the predefined current Is.

In an operation S320, a reference voltage potential drop is determined by the voltage potential drop measurement unit140across the power line and the ground line of the bus during all slave units except the selected one operating in the low-power mode and the selected slave unit operating in the first high-power mode. The voltage potential drop measurement unit140reports the measured reference voltage potential drop to the measurement data analyzer section120.

In an operation S330, the selected slave unit is instructed by the master unit100to enter the first high-power mode.

In an operation S335, the predefined current Isis driven by the current adjustable power source135on the power line of the bus.

In an operation S340, a positioning voltage potential drop is determined by the voltage potential drop measurement unit140across the power line and the ground line of the bus during all slave units except the selected one operating in the low-power mode and the selected slave unit operating in the first high-power mode. The voltage potential drop measurement unit140reports the measured positioning voltage potential drop to the measurement data analyzer section120.

In an operation S350, a cable resistance is determined by the measurement data analyzer section120based on a relative voltage potential, which is in turn determined from the measured drop the reference voltage potential drop and the measured positioning voltage potential drop.

In an operation S360, the list of slave units is updated with respect to the selected slave unit. For instance, the selected slave unit is removed from the list of slave units or the selected slave unit is indicated as being detected in the list of slave units such that the selected slave unit will be ignored in the further process of the auto-addressing procedure.

In an operation S365, the master unit100determines whether or not remaining slave units with unknown position/arrangement are still present. If there are remaining undetected slave units, the auto-addressing procedure return to the operation S305and iterates the auto-addressing procedure with selecting a next slave unit from the list of slave units. Otherwise, if all slave units have been selected in previous iterations, the auto-addressing procedure continues with an operation S370, in which the relative arrangement/positions of the slave units connected to the bus are determined from the cable resistances determined for each slave unit.

The reference voltage potential drop measurement performed at an exemplarily selected slave unit200.2will be more fully described with reference toFIG. 12a, which schematically illustrates a block diagram of a communication network with slave units operating in low-power mode except a selected one operating in a first high-power mode according to an example of the present application.

As described above, the master unit100instructs all slave units expect a selected one to enter the low-power mode and instructs the selected slave unit to enter the first high-power mode. For the sake of example, the slave unit200.2is the selected one.

The reference voltage potential drop V2ref, which is measured at the master node100across the power line and the ground line of the bus, can be determined as follows:
V2ref≈2·Rc·IS+RH1·IS+2·Rc·IS

When assuming that current flowing though the slave units operating in the low-power mode can be substantially neglected in view of the current flowing through the selected slave unit operating in the first high-power mode and wherein Isis the current supplied by the current adjustable power source135, Rcis the resistance of a line section of the power supply line or the ground line between two neighboring units (e.g. between the master unit100and the first slave unit200.1or between neighboring slave unit200.iand200.i+1) and RH1is the effective resistance in the first high-power mode.

More generally, the reference voltage potential drop Viref, which is measured at the master node100across the power line and the ground line of the bus in response to all slave units operating in low-power mode except a slave unit200.ioperating in the first high-power mode, can be determined as follows:
V1ref≈i·Rc·IS+RH1·IS+i·Rc·IS
=(2·i·Rc+RH1)·IS
=(2·i·Rc+fH·RB)·IS

wherein the effective RH1=fH·RB, fHis a scaling factor with respect to an effective base resistance RB.

Referring back toFIGS. 9bto 9cillustratively showing block diagrams of an exemplary slave unit200.i, the scaling factor fHmay be fH=4.

The positioning voltage potential drop measurement performed at an exemplarily selected slave unit200.2will be more fully described with reference toFIG. 12b, which schematically illustrates a block diagram of a communication network with slave units operating in low-power mode except a selected one operating in a second high-power mode according to an example of the present application.

As described above, the master unit100instructs all slave units expect a selected one to enter the low-power mode and instructs the selected slave unit to enter the second high-power mode. For the sake of example, the slave unit200.2is the selected one.

The positioning voltage potential drop V2pos, which is measured at the master node100across the power line and the ground line of the bus, can be determined as follows:
V2pos≈2·Rc·IS+RH2·IS+2·Rc·IS

When assuming that current flowing though the slave units operating in the low-power mode can be substantially neglected in view of the current flowing through the selected slave unit operating in the first high-power mode and wherein Isis the current supplied by the current adjustable power source135, Rcis the resistance of a line section of the power supply line or the ground line between two neighboring units (e.g. between the master unit100and the first slave unit200.1or between neighboring slave unit200.iand200.i+1) and RH2is the effective resistance in the second high-power mode.

More generally, the positioning voltage potential drop Vipos, which is measured at the master node100across the power line and the ground line of the bus in response to all slave units operating in low-power mode except a slave unit200.ioperating in the first high-power mode, can be determined as follows:
Vipos≈i·Rc·IS+RH2·IS+i Rc·IS
=(2·i·Rc+RH2)·IS
=(2·i·Rc+RB)·IS

wherein the effective base resistance RBis equal to the effective resistance RH2of the slave unit200.ioperating in the second high-power mode, RB=RH2.

The relative voltage potential drop ΔVidetermined based on a difference of the measured voltage potential drops allows to conclude the cable resistance between master unit100(and the current adjustable power source135thereof) and the respective slave unit200.iat which the measurements have been performed. The relative voltage potential drop ΔVidenotes as follows:
ΔVi=fH·Vipos−Viref
=fH·(2·i·Rc+RB)·IS−(2·i·Rc+fH·RB)·IS
=2·i·(fH−1)·Rc·IS

where the effective resistance of the slave node200.iin the first high-power mode is RH1=fHRB, the effective resistance of the slave node200.iin the second high-power mode is RH2=RB, fHis the scaling factor, and RBis the effective base resistance.

Therefore, the relative positions/arrangement of the slave units200.i(1≤i≤n) can be determined by analyzing the levels of the relative voltage potential drop ΔVi, which is substantially proportional to the position index i.

As the skilled person may understand from the above description, the resistance of the power supply line and/or the ground line may be substantially low. As shown above with respect to the above examples, the relative positions/arrangement of the slave units200.i(1≤i≤n) can be determined by analyzing the levels of the relative voltage potential drop ΔVi, which is in turn substantially proportional to the resistance Rc, which denotes the resistance of a line section of the power supply line or the ground line between two neighboring units (e.g. between the master unit100and the first slave unit200.1or between neighboring slave unit200.iand200.i+1). This means that the higher the resistance Rcthe more distinct are the levels of the relative voltage potential drop ΔViobtained from the measured voltage potential drops. As further shown above, the relative voltage potential drop ΔViis proportional to the scaling factor fHminus one:
ΔVi˜i·(fH−1), 1≤i≤n

Increasing the scaling factor fH, which denotes the ratio of the effective resistances in the first and second high-power modes, enables increasing the distance between the levels of the relative voltage potential drop ΔVi. Further, the integration of a shunt resistance allows likewise for increasing the level distances.

Referring toFIG. 13now, each slave unit200.iaccording to an example of the present application comprises a shunt resistance Rs, which is for instance arranged in series with the power line. The shunt resistance Rsis arranged downstream to the effective resistances, across which the voltage potential drops are measured. Accordingly, the slave unit200.ihas an input terminal and an output terminal for connecting to the power line. The shunt resistance Rsis connected between the input terminal and the output terminal. Alternatively or additionally, a shunt resistance Rsmay be arranged in series with the ground line (not shown). The statements above with respect to the shunt resistance Rsconnected in series with the power line apply analogously to a shunt resistance Rsconnected in series with the ground line.

Referring toFIG. 14anow, the reference voltage potential drop Viref, which is measured at the master node100across the power line and the ground line of the bus in response to all slave units operating in low-power mode except a slave unit200.ioperating in the first high-power mode, can be determined as follows:
Viref≈i·(Rc+RS)·IS+RH1·IS+i·Rc·IS
=(2·i·Rc+i·RS+RH1)·IS
=(2·i·Rc+i·RS+fH·RB)·IS

wherein the effective RH1=fH·RB, fHis a scaling factor with respect to an effective base resistance RB.

Referring toFIG. 14bnow, the positioning voltage potential drop Vipos, which is measured at the master node100across the power line and the ground line of the bus in response to all slave units operating in low-power mode except a slave unit200.ioperating in the second high-power mode, can be determined as follows:
Vipos≈i·Rc·(Rc+RS)·IS+RH2·IS+i·Rc·IS
=(2·i·Rc+i·RS+RH2)·IS
=(2·i·Rc+i·RS+RB)·IS

wherein the effective base resistance RBis equal to the effective resistance RH2of the slave unit200.ioperating in the second high-power mode, RB=RH2.

The relative voltage potential drop ΔVidenotes as follows:

The shunt resistance increases the distance between the levels of the relative voltage potential drop ΔVi.

It should be noted that the above exemplified auto-addressing procedures may be performed using the current adjustable power source135supplying a direct current or an alternating current having in particular a predefined frequency. In the latter case, the voltage measurement is performed at the master unit100with respect to the predefined frequency of the alternating current supplied by the current adjustable power source135. More particularly, the voltage potential drop measurements in high-power mode may be performed using alternating current. The use of an alternating current supplied by the current adjustable power source135may be more robust regarding noise and disturbance signals and may further reduce the requirements for measuring accuracy of the circuitry for measuring the voltage potential drops including in particular the voltage potential drop measurement unit140. The above teaching enables the skilled person to implement the above exemplified auto-addressing procedures using direct current or alternating current supplied by the current adjustable power source135.

The above embodiments illustrate the basic concept of the present invention to determine the positioning of slave units connected along a stub bus based on a bus line resistance, which in turn is determined based on relative voltage potential drops determined in different power modes. The relative voltage potential drops enable a reliable determining of the small voltage drops due to low bus line resistance.

According to an aspect of the present application, a method and a system allowing for determining relative positions of a plurality of slave units connected to a stub bus with a master unit is provided. The stub bus comprises at least a power line and a ground line. Each slave unit is operable in different power modes, which are differentiated by effective resistances between the power line and the ground line. For each slave unit, a reference voltage potential drop (Viref) is determined across the power line and the ground line while the slave units are operating in a first power mode. For each slave unit, a positioning voltage potential drop (Vipos) is determined across the power line and the ground line with regard to the one or more slave units while a selected slave unit of the plurality of slave units is operating in a second power mode. The relative positions of the plurality of slave units is determined based on relative voltage potential drops (ΔVi) obtained from the reference voltage potential drops (Viref) and the positioning voltage potential drops (Vipos) of the respective slave units. According to an example, the operations conducted to determine the relative positions of a plurality of slave units is under control of the master unit, which is connected to one end of the stub bus.

In an example, the operations conducted to determine the relative positions of a plurality of slave units are under control of the master unit, which is connected to one end of the stub bus.

According to another aspect of the present application, each slave unit comprises a voltage potential drop measurement unit arranged to measure a voltage potential drop across the power line and the ground line. the master unit is configured to instruct each slave unit to measure the reference voltage potential drop (Viref) while each the slave unit is operating in a low-power mode. The master unit is further configured to instruct each slave unit to measure the positioning voltage potential drop while each slave unit is operating in a low-power mode except a selected slave unit operating in a high-power mode. The master unit is arranged to collect the relative voltage potential drops (ΔVi) for each slave unit. Each relative voltage potential drop (ΔVi) is based on the reference voltage potential drop (Viref) and positioning voltage potential drop (Vipos) measured by the respective slave unit. The master unit is configured to detect the relative positions of one or more slave units based on the collected relative voltage potential drops.

In an example, the master unit is arranged to receive the relative voltage potential drops (ΔVi) from the slave units. Each of the slave unit is arranged to determine the relative voltage potential drop (ΔVi) based on the measured reference voltage potential drop (Viref) and the measured positioning voltage potential drop (Vipos). In an example, each slave unit is arranged to determine the relative voltage potential drop (ΔVi) by determining a difference between the measured positioning voltage potential drop (Vipos) and the measured reference voltage potential drop (Viref). In an example, the master unit is arranged to maintain a list of the plurality of slave units connected to the stub bus. The list indicates with respect to each slave unit whether or not the relative position along the stub bus is detected. Detecting the relative positions of one or more slave units based on the collected relative voltage potential drops (ΔVi) is repeated as long as the relative position of at least one slave unit is undetected. The collected relative voltage potential drops (ΔVi) is obtained by instructing each slave unit to measure the reference voltage potential drop (Viref) and the positioning voltage potential drop (Vipos) with a newly selected slave unit out of the slave units being undetected. In an example, the master unit comprises a voltage adjustable power source arranged to apply a predefined voltage (Vs) across the power line and ground line. The master unit is arranged to drive the predefined voltage (Vs) on the power line during measuring the reference voltage potential drops (Viref) and the positioning voltage potential drops (Vipos). In an example, the predefined voltage (Vs) is a predefined direct current voltage (Vs) or the predefined voltage (Vs) is a predefined alternating voltage (Vs) having a predefined frequency.

According to a further aspect of the present application, the master unit comprises a voltage potential drop measurement unit provided to measure a voltage potential drop across the power line and ground line. The master unit is configured to measure the reference voltage potential drop (Viref) while each the slave unit operating in a low-power mode except a selected slave unit operating in a first high-power mode. The master unit is configured to measure the positioning voltage potential drop (Vipos) while each slave unit is operating in a low-power mode except the selected slave unit operating in a second high-power mode. The master unit is configured to determine a relative voltage potential drop (ΔVk) for the selected slave unit. The master unit is configured to detect the relative positions of the plurality of slave units based on the relative voltage potential drops (ΔVi) determined for each slave unit (200.i).

In an example, the master unit is arranged to maintain a list of the plurality of slave units connected to the stub bus. The list indicates whether or not a slave unit out of the plurality of slave units has been already selected once. The master unit is arranged to select a slave unit, which has not been already selected once, out of the plurality of slave units. The determining of the relative voltage potential drop (ΔVk) is repeated for the selected slave unit. The master unit is arranged to collect the relative voltage potential drops (ΔVk) of the selected slave unit. The relative positions of the plurality of slave units is detected by the master unit once the relative voltage potential drops (ΔVi) have been determined for each slave unit. In an example, the master unit comprises a current adjustable power source arranged to apply a predefined current (Is) across the power line and ground line. The master unit is arranged to drive the predefined current (Is) on the power line during measuring the reference voltage potential drop (Viref) and the positioning voltage potential drop (Vipos). In an example, the predefined current (Is) is a direct current or the predefined current (Is) is an alternating current having a predefined frequency.

According to a yet another aspect of the present application, a system comprising a plurality of slave units connected to a stub bus with a master unit is provided. The system is enabled to determine relative positions of plurality of slave units along the stub bus. The stub bus comprises at least a power line and a ground line. Each slave unit configured to operate in different power modes, which are differentiated by effective resistances between the power line and the ground line. the system configured to determine for each slave unit a reference voltage potential drop (Viref) across the power line and the ground line while the slave units are operating in a first power mode; to determine for each slave unit a positioning voltage potential drop (Vipos) across the power line and the ground line with regard to the one or more slave units while a selected slave units of the plurality of slave units is operating in a second power mode; and to determine relative positions of the plurality of slave units based on relative voltage potential drops (ΔVi) obtained from the reference voltage potential drops (Viref) and the positioning voltage potential drops (Vipos).

In an example, each slave unit comprises a voltage potential drop measurement unit arranged to measure a voltage potential drop across the power line and the ground line. The master unit is arranged to instruct each slave unit to measure the reference voltage potential drop (Viref) while each the slave unit operating in a low-power mode. The master unit is arranged instruct each slave unit to measure the positioning voltage potential drop (Vipos) while each slave unit operating in a low-power mode expect a selected slave unit operating in a high-power mode. The master unit is arranged to collect relative voltage potential drops (ΔVi) for each slave unit. Each relative voltage potential drop (ΔVi) is based on the reference voltage potential drop (Viref) and positioning voltage potential drop (Vipos) measured by the respective slave unit. The master unit is arranged to detect the relative positions of one or more slave units based on the collected relative voltage potential drops (ΔVi). In an example, each the master unit is arranged to receive the relative voltage potential drops (ΔVi) from the slave units. Each of the slave units is arranged to determine the relative voltage potential drop (ΔVi) based on the measured reference voltage potential drop (Viref) and the measured positioning voltage potential drop (Vipos).

In an example, the master unit comprises a voltage potential drop measurement unit arranged to measure a voltage potential drop across the power line and ground line. The master unit is arranged to measure the reference voltage potential drop (Viref) while each the slave unit operating in a low-power mode except a selected slave unit operating in a first high-power mode. The master unit is arranged to measure the positioning voltage potential drop (Vipos) while each slave unit is operating in a low-power mode except the selected slave unit operating in a second high-power mode. The master unit is arranged to determine a relative voltage potential drop (ΔVk) for the selected slave unit. The master unit is arranged to detect the relative positions of the plurality of slave units based on the relative voltage potential drops (ΔVi) determined for each slave unit. In an example, the master unit is arranged to maintain a list of the plurality of slave units connected to the stub bus. The list indicates whether or not a slave unit out of the plurality of slave units has been already selected once. The master unit is arranged to select a slave unit, which has not been already selected once, out of the plurality of slave units. The master unit is arranged to repeat the determining of the relative voltage potential drop (ΔVk) for the selected slave unit. The master unit is arranged to collect the relative voltage potential drops (ΔVk) of the selected slave unit. The relative positions of the plurality of slave units is detected by the master unit once the relative voltage potential drops (ΔVi) have been determined for each slave unit.