SE544349C2

SE544349C2 - Communication of combined speed and synchronization signals between vehicle control units

Info

Publication number: SE544349C2
Application number: SE1850549A
Authority: SE
Inventors: Björn Johansson; Joakim Sommansson
Original assignee: Scania Cv Ab
Priority date: 2018-05-09
Filing date: 2018-05-09
Publication date: 2022-04-19
Also published as: DE102019002683A1; SE1850549A1; BR102019008798A2

Abstract

The present disclosure relates to techniques in the context of vehicles, and in particular to methods for communicating speed and synchronization signals between control units in a vehicle. According to a first aspect, the disclosure relates to first control unit for use in a vehicle. The first control unit comprises control circuitry 11, an internal clock 16, an input 13 and one or more outputsl 4, 15. The input 13 is configured to receive, from a speed sensor, a speed signal comprising a pulse train corresponding to a speed of a rotating object in the vehicle. The one or more outputs 14, 15 are configured to enable transmission to a second control unit. The control circuitry 11 is configured to generate a combined synchronization and speed signal by embedding a first synchronization message in an incoming speed signal received on the input and to generate a second synchronization message, wherein the first synchronization message and the second synchronization message together indicate a timing of the internal clock. The control circuitry 11 is also configured to transmit the first synchronization message and the second synchronization message to the second control unit at the one or more outputs. The present disclosure also relates to a second control unit, to corresponding methods, to a power train and a vehicle comprising the control units and to a computer program.

Description

Communication of combined speed and synchronization signals between vehiclecontrol units Technical field The present disclosure relates to techniques in the context of vehicles, and inparticular to methods for communicating speed and synchronization signalsbetween control units in a vehicle. The present disclosure also relates tocorresponding control units, to a vehicle comprising the control units and to a computer program.

BackgroundAn Electrical Control Unit, ECU, is an embedded electronic device, basically a digital computer that controls one or more electrical systems (or electrical subsystems) of a vehicle based on e.g. information read from sensors placed atvarious parts and in different components of the vehicle. ln more advancedvehicles such as buses, lorries, trucks, work vehicles and advanced cars; anetwork such as a CAN network (Controller Area Network) is used to handle thecommunication between various ECUs in the vehicle. The ECUs that areconnected to the CAN may handle a large number of functions in the vehicle.These are, for example, functions related to change of gear, steering, enginecontrol, braking, climate-control systems, lighting, driver comfort, alarms and safety.

As of today, the electrical systems of a vehicle are in general not synchronized.Typically, each ECU has its own internal clock. Each electrical system typicallyalso has its own sensors. For example, the engine system might have one speedsensor and the gear system might have one speed sensor. Alternatively, sensordata e.g. a speed signal, is sent over a bus, such as the Controller Area Network,CAN, bus. However, the CAN bus is a priority-based bus and due to other trafficon the bus, it is not certain when messages will be sent. Hence, using only theCAN bus for communicating the speed signal, makes the speed signal non-deterministic and the update frequency will be low, which limits the usefulness of the speed signal.

Summarylt is an object of the disclosure to alleviate at least some of the drawbacks with existing solutions. lt is a still further object to provide improvements for ECU-toECU signaling in a vehicle, at least related to improving accuracy incommunicating speed and synchronization signals between control units in avehicle. Another object is to achieve this with limited addition of additional hardware.

According to a first aspect, the disclosure relates to first control unit for use in avehicle. The first control unit comprises control circuitry, an internal clock, an inputand one or more outputs. The input is configured to receive, from a speed sensor,a speed signal comprising a pulse train corresponding to a speed of a rotatingobject in the vehicle. The one or more outputs are configured to enabletransmission to a second control unit. The control circuitry is configured togenerate a combined synchronization and speed signal by embedding a firstsynchronization message in an incoming speed signal received on the input, togenerate a second synchronization message, wherein the first synchronizationmessage and the second synchronization message together indicate a timing ofthe internal clock, and to transmit the conibined synchronization and speed signal and the second synchronization message to thesecond control unit at the one or more outputs. Thereby, time synchronizationbetween the first and the second control unit is enabled with minor hardwaremodifications (one extra I/O). At the same time, it is possible to communicate aspeed signal from the first control unit to the second control unit. The speed signalmay be used e.g. to detect for example powertrain fluctuations, clutch slip etc.One of the functions on its own might not motive the extra l/O. However, usingone wire for both purposes makes a much better case. ln some embodiments, the one or more outputs comprises a single-wire output port, and the control circuitry is configured to transmit the combined 3 synchronization and speed signal at the single-wire output port. Thereby, both thesynchronization and speed signal can be communicated using only one additionaloutput (i.e. dedicated l/O). ln some embodiments, the control circuitry is configured to interpret the receivedspeed signal and the control circuit is configured to generate and/or transmit thefirst and the second synchronization messages in response to interpreting thereceived speed signal. Hence, errors that might occur at start-up will not bepresent in the combined synchronization and speed signal. ln some embodiments, the one or more outputs comprises a communication businterface and the control circuitry is configured to transmit the secondsynchronization message at the communication bus interface. The secondsynchronization message that is transmitted on a communication bus may simplifythe synchronization information needed to be transferred in the firstsynchronization message. The second synchronization message may alsoincrease the accuracy of the synchronization. ln some embodiments, the first synchronization message is a synchronizationpattern and the second synchronization message indicates a relation between thesynchronization pattern and the internal clock. Thereby, the timing of the internalclock may be estimated by a receiving second control unit. ln some embodiments, the control circuitry is configured to embed both the firstsynchronization message and the second synchronization message in thecombined synchronization and speed signal. Thereby, all information needed forthe communication of synchronization and speed information may be transmitted on one single wire. ln some embodiments, the first synchronization message is an incomingsynchronization pattern that indicates that an actual synchronization will occurwithin a pre-defined time and the second synchronization message is asynchronization pattern that indicates the timing of the internal clock. The incoming synchronization pattern will mitigate signal errors at the receiving side. 4 ln some embodiments, the first control unit is a master control unit and the secondcontrol unit is a slave control unit of the first control unit. ln some embodiments, the control circuitry comprises real-time processinghardware configured to generate the combined synchronization and speed signal.Thereby, the combined synchronization and speed signal may be generated withnegligible delay.

According to a second aspect, the disclosure relates to second control unit for usein a vehicle. The second control unit comprises an internal clock, an input, andcontrol circuitry. The input configured to receive, from a first control unit, acombined synchronization and speed signal comprising a pulse train with afrequency corresponding to a speed of a rotating object in the vehicle, and thecontrol circuitry is configured to detect a first synchronization message, embeddedin an incoming combined synchronization and speed signal received on the one ormore inputs, to receive a second synchronization message from the first controlunit, and to determine a timing of an internal clock of the first control unit, basedon the first synchronization message and the second synchronization message.Thereby, the second control unit may receive speed and synchronization information from the first control unit with minor hardware additions. ln some embodiments, the control circuitry is configured to adjust a timing of aninternal clock of the second control unit based on the determined timing. Thereby,the subsystems may operate in synchronization and unnecessary delays may be avoided. ln some embodiments, the one or more inputs comprises a single-wire input portconfigured to receive the combined synchronization and speed signal from thefirst control unit. ln some embodiments, the control circuitry is configured to detect a pre-determined pulse sequence in the incoming combined synchronization and speed signal. ln some embodiments, the control circuitry is configured to ignore pulsesequences having a frequency above a pre-defined threshold value. ln some embodiments, the one or more inputs comprises a communication businterface and the control circuitry is configured to receive the secondsynchronization message at the communication bus interface. ln someembodiments, the first synchronization message is a synchronization pattern, andthe second synchronization message indicates a relation between thesynchronization pattern and the internal clock of the first control unit. ln some embodiments, the control circuitry is configured to detect a secondsynchronization message being embedded in the incoming combinedsynchronization and speed signal. ln some embodiments, first synchronizationmessage is an incoming synchronization pattern that indicates that an actualsynchronization will occur within a pre-defined time and the secondsynchronization message is a synchronization pattern indicates the timing of theinternal clock of the first control unit.

According to a third aspect, the disclosure relates to a power train comprising thefirst control unit and the second control unit. Thereby, the speed of the enginemay for example be communicated to the gear system, whereby clutch slip maybe estimated. By keeping track of the clutch slip, the powertrain ECUs canestimate the transferred torque during a drive away start where the slip could berecalculated as to the transferred Torque. Detection of static torsional wind upcould be recalculated to current transferred Torque with the information of clutchtype and clutch wear. Furthermore, micro-slip may be used during driving toisolate oscillations from the engine. Then it may also be desirable to monitor the micro-slip.

According to a fourth aspect, the disclosure relates to a vehicle comprising thepower train of the third aspect.

According to a fifth aspect, the disclosure relates to a method, for use in a first control unit in a vehicle, for communicating synchronization and speed information 6 to a second control unit of the vehicle. The first control unit has an internal clock.The method comprises receiving, from a speed sensor, a speed signal comprisinga pulse train with a frequency corresponding to a speed of a rotating object in thevehicle and generating a combined synchronization and speed signal byembedding, a first synchronization message in the received speed signal. Themethod further comprises generating a second synchronization message, whereinthe first synchronization message and the second synchronization messagetogether indicate a timing of the internal clock and transmitting the combinedsynchronization and speed signal and the second synchronization message to the second control unit. ln some embodiments, the first synchronization message is a pre-determinedpulse sequence embedded in the combined synchronization and speed signal. ln some embodiments the method comprises interpreting the received speedsignal, and the generating and/or the transmitting is performed in response to the interpreting. ln some embodiments, the second synchronization message is also embedded inthe combined synchronization and speed signal. ln some embodiments, the first synchronization message is an incomingsynchronization pattern that indicates that an actual synchronization will occurwithin a pre-defined time and the second synchronization message is an actualsynchronization pattern that indicates the timing of the internal clock. ln some embodiments, the second synchronization message is a message transmitted on a communication bus of the vehicle. ln some embodiments, the first synchronization message is a synchronizationpattern, and the second synchronization message indicates a relation betweenthe internal clock and the synchronization pattern. ln some embodiments, the transmitting comprises transmitting the combinedsynchronization and speed signal between powertrain ECUs. 7 According to a sixth aspect, the disclosure relates to method, for use in a secondcontrol unit of a vehicle, for receiving synchronization and speed information froma first control unit of the vehicle. The method comprises receiving, from the firstcontrol unit, a combined synchronization and speed signal comprising a pulsetrain with a frequency corresponding to a speed of a rotating object in the vehicleand detecting a first synchronization message, embedded in the receivedcombined synchronization and speed signal. The method further comprisesreceiving a second synchronization message from the first control unit anddetermining a timing of an internal clock of the first control unit, based on the first synchronization message and the second synchronization message. ln some embodiments, the method comprises adjusting a timing of an internalclock of the second control unit based on the determined timing. ln some embodiments, the method comprises detecting comprises detecting apre-determined pulse sequence in the incoming combined synchronization andspeed signal. ln some embodiments, the detecting comprises ignoring pulsesequences having a frequency above a pre-defined threshold value. ln some embodiments, the receiving the second synchronization messagecomprises receiving the second synchronization message at a communicationbus. ln some embodiments, the first synchronization message is asynchronization pattern, and the second synchronization message indicates arelation between the synchronization pattern and a timing of the internal clock of the first control unit. ln some embodiments, receiving the second synchronization message comprisesdetecting a synchronization pattern being embedded in the combinedsynchronization and speed signal. ln some embodiments, the first synchronizationmessage is an incoming synchronization message and the secondsynchronization message is a synchronization pattern that indicates a timing ofthe internal clock of the first control unit. 8 According to a seventh aspect, the disclosure re|ates to computer programcomprising instructions which, when the program is executed by a computer,cause the computer to carry out the any of the methods described above andbelow.

According to an eighth aspect, the disclosure re|ates to computer-readablemedium comprising instructions which, when executed by a computer, cause the computer to carry out any of the methods described above and below.

Brief description of the drawinqs Fig. 1 i||ustrates a vehicle in which the proposed control units and methods can beused.

Fig. 2 i||ustrates a power train of the vehicle in Fig. 1.

Fig. 3 i||ustrates a tooth wheel sensor.

Fig. 4 i||ustrates communication between a first and a second control unitaccording to a first example embodiment.

Fig. 5 i||ustrates communication between a first and a second control unitaccording to a second example embodiment.

Fig. 6 i||ustrates the internal clock of the first control unit and the internal clock ofthe second control unit.

Fig. 7 i||ustrates synchronization of the internal clock of the second control unit.Fig. 8 i||ustrates a first control unit according to some embodiments.

Fig. 9 i||ustrates a second control unit according to some embodiments.

Fig. 10 i||ustrates a method performed in a first control unit according to someembodiments.

Fig. 11 i||ustrates a method performed in a second control unit according to someembodiments.

Detailed descriptionlt is generally desirable to synchronize the internal clocks of the sub systems of a vehicle to avoid unnecessary delays and have the control units of the subsystems working in sync. 9 Furthermore, it may be required to communicate speed information between subsystems in a vehicle with high accuracy. One reason for communicating speedinformation between control units in a vehicle is to be able to detect powertrainfluctuations such as clutch slip. Clutch slip may basically be detected bycomparing the rotation of the engine shaft with the rotation of the correspondingshaft on the gear box side. However, the engine and the gearbox typically belongto separate electrical sub systems in the vehicle. Hence, to determine the clutchslip accurately, the engine speed measure at the engine side needs to be communicated to the gearbox subsystem.

Generally, it is desirable to limit the number of extra wires between the controlunits. Hence, it might be difficult to motivate one additional wire for each of thesefunctions. Therefore, it is herein proposed to design an Electrical Control Unit,ECU, to transfer both speed and synchronization information on one single wire.This solution is useful in a system comprising at least two control units where onetypically acts as a master and the others are slaves. ln the proposed solution, themaster ECU has a speed signal input that is interpreted by the master ECU andsent out as a digital pulse train with a frequency corresponding to a speed of themeasured rotating object. Embedded in the signal is also a synchronizationmessage. This synchronization signal can be used to synchronize/compensatethe clock of the slave ECUs.

The proposed solution only requires one additional wire (or input/output, l/O) percontrol units, the rest of the implementation is handled by software. However,there are two reasons for this extra I/O between the ECUs. One is to provide asynchronization signal to match/compensate the internal clocks of the ECU”s toavoid unnecessary delays and have the ECUs working in synchronization. Theother one is to communicate accurate information about a rotating object. One ofthe functions on its own might not motivate the extra wire but using one wire for both purposes makes a better case.

Fig. 1 illustrates a vehicle 1 in which the proposed control units and methods can be used. The vehicle 1 of Fig. 1 comprises a power train 2. The vehicle 1 may e.g. lO be a work vehicle such as a truck, a bus or other heavy vehicle; or the vehicle 1 may be a regular car.

Fig. 2 illustrates a power train of the vehicle in Fig. 1 in more detail. The powertrain comprises a power source, here an engine 3, an engine shaft 4 a clutch 5, agearbox 6, a gear input shaft 7 and a drive shaft 8. The power generated by theengine 3 is conveyed from the engine shaft 4, via the clutch 5 and the gearbox 6to the drive shaft 8 that drives the wheels of the vehicle 1. The clutch 5 is e.g. afriction clutch comprising one or more discs with friction linings which are pressedagainst a steel plate, e.g. by powerful springs and a pressure plate, resulting indirect drive between the engine 3 and the gearbox 6 when the vehicle 1 isrunning. However, if there is not enough friction in the clutch 5, the power sourcespeed may rise without a corresponding increase in road speed. This is in generala faulty condition, which may be estimated by comparing the speed of the engineshaft 4 with the speed of the input shaft 7. Sometimes, micro-slip (i.e. very smallclutch slip) is introduced on purpose, for example when trying to mitigatedrivetrain oscillations. However, micro-slip should always be a chosen mode ofoperation, i.e., not something that happens by chance. When micro-slip is intentional, then the clutch 5 is not fully closed on purpose.

The engine 3 and the gearbox 6 are typically controlled by separate electrical subsystems, each sub system comprising one or more ECUs, herein referred to ascontrol units. For simplicity, it is in this example assumed that each subsystemcomprises only one ECU. More specifically, the engine 3 is controlled by a firstcontrol unit 10 and the gearbox 6 is controlled by a second control unit 20. The first and second control units 10, 20 will be further described with reference to Fig. 8 and Fig. 9.

The power train also comprises a speed sensor 30, configured to sense theengine speed. Fig. 3 illustrates an example embodiment where the speed sensor30 is a tooth wheel sensor. The tooth wheel sensor scans a tooth wheel 31,arranged on the engine shaft 4. The tooth wheel sensor may for example comprise two hall effect sensors, a rare earth magnet and appropriate evaluation ll electronics. The field of the magnet is modulated by the passing target teeth. Thismodulation is registered by the Hall sensors, converted by a comparator stage toa square wave signal S and amplified in a driver stage.

The signal S generated by the speed sensor 30 has a period that corresponds toa gear tooth of the tooth wheel 31 and in some embodiments also comprisesadditional position information about where in the cycle the tooth wheel 31 is, e.g.indicated by one or more long pulses 33 caused by one or more long teeth 32 onthe tooth wheel 31 positioned at pre-determined positions on the tooth wheel 31.Thus, based on the generated signal, the first control unit 10 can determine theengine speed as well as where in the cycle the engine is.

The proposed technique will now be described with reference to the first controlunit 10 and a second control unit 20 of Fig. 2. However, it must be appreciatedthat the solution may be used for any control units in a vehicle, when it is desiredto communicate speed and synchronization information. ln the proposed solution,an additional wire is added between the first control unit 10 and the secondcontrol unit 20, in order to be able to forward a speed signal between the controlunits 10, 20. lt is further proposed to embed synchronization information in thespeed signal, such that synchronization between the first control unit 10 and thesecond control unit 20 is also enabled. The synchronization information comprisesa first and a second synchronization message. There are different ways ofimplementing the synchronization messages. Two example implementations will now be described with reference to Figs. 4 and 5.

Fig. 4 illustrates communication between a l\/laster ECU, herein also referred to asthe first control unit 10, and a Slave ECU, herein also referred to as the secondcontrol unit 20, according to a first example embodiment. ln this example,transmission of two synchronization messages (a first and a secondsynchronization message) are periodically triggered by the l\/laster ECU, e.g. each1000ms. Thus, the Slave ECU can synchronize its internal clock with the internalclock of the l\/laster ECU by observing the synchronization messages and adjusting its internal clock accordingly. 12 The first synchronization message I\/|1 is an incoming synchronization pattern andthe second synchronization message l\/l2 is an actual synchronization pattern. Theincoming synchronization pattern indicates that an actual synchronization patternwill occur within a specified time limit. The incoming synchronization pattern is e.g.inserted in the pulse train by replacing a long pulse with a specified pattern, e.g.several short pulses. The purpose of the incoming synchronization pattern is toincrease robustness and make errors less likely. The actual synchronizationpattern is here inserted by replacing a short pulse (standard tooth) with two shortpulses. The actual synchronization pattern is triggered when the clock in thel\/laster ECU reaches a pre-defined value. The pre-defined value is e.g. O, whenthe l\/laster ECU clock is looping from O to 2048.

Fig. 5 illustrates an alternative implementation of a first synchronization messagecomprising a synchronization pattern periodically triggered by the l\/laster ECU,e.g. each 10th engine revolution. ln this example, the Slave ECU can synchronizeits clock with the l\/laster ECU clock by observing the synchronization pattern anda corresponding second synchronization message that is transmitted over theCAN. ln this example, the first synchronization message I\/|1 is a synchronization patternand the second synchronization message lVl2” is a CAN message. Thus, in thisembodiment only one synchronization pattern is transmitted. This patternindicates that a synchronization event has occurred. The synchronization patternis indicated in the pulse train by replacing a long pulse with a specified pattern,e.g. several short pulses. When the synchronization event is triggered, acorresponding CAN message is also sent from the l\/laster ECU to the Slave ECU.The CAN message contains information associated with the synchronizationpattern e.g. the number of engine revolutions and elapsed time since the last synchronization event.

By combining the time when the synchronization pattern was received with theinformation in the corresponding CAN message, the Slave ECU can estimate itsclock drift. 13 Fig. 6 illustrates the internal clock 16 of the first control unit 10 and the internal clock 26 of the second control unit 20 when being out of synchronization.

Fig. 7 illustrates synchronization of the internal clock of the second control unit. Byidentifying a time t (corresponding to a known pre-defined value e.g. 0) of theinternal clock 16 of the of the first control unit 10, the second control unit 20 canestimate its clock drift. The second control unit 20 may then gradually (i.e. with amaximum change rate) adjust its own internal clock 26 to be in synchronizationwith the internal clock 16 of the first control unit 10. By doing it gradually, intermittent errors will be mitigated.

An example implementation of the first control unit 10 of the vehicle 1 of Fig. 1 willnow be described with reference to Fig. 8. The first control unit 10 is configured tocommunicate synchronization and speed information to a second control unit 20of the vehicle 1. ln some embodiments, the first control unit 10 is a master controlunit and the second control unit 20 is a slave control unit of the first control unit10.

The first control unit 10 comprises control circuitry 11, a memory 12, an input 13,an output 14, a communication bus 15 and an internal clock 16. The first controlunit 10 typically also comprises a plurality of other components and I/O interfaces.However, for simplicity only the components and l/O interfaces needed to explainthe proposed technique will now be described.

The internal clock 16, clocks the functionality of the first control unit 10. Theinternal clock 16 can for example be used to timestamp measurement datareceived at the input 13.

The input 13 is single-wire input port. The input 13 is configured to receive, asignal from another component in the vehicle e.g. a sensor. lt is implicit that thefirst control unit 10 and the other component are connected to a common ground.For example, the input 13 is arranged to receive a speed signal comprising apulse train corresponding to a speed of a rotating object in the vehicle 1 from aspeed sensor 30. The rotating object is e.g. a tooth wheel 31 attached to a shaft in 14 the vehicle 1, e.g. to the engine shaft 4. However, the solution would work also formeasuring the revolution of other shafts and other rotating objects.

The output 14 is a signal-wire output port, that is configured to be connected to asecond control unit 20. When the first control unit 10 is installed in the vehicle 10,then the output 14 is typically electrically connected to a corresponding input 23(Fig. 9) of the second control unit 20 by a single wire. ln other words, the output14 is configured to enable transmission of a signal to a second control unit 20. Asexplained above, it is implicit that the first control unit 10 and the second control unit 20 have a common ground.

The communication bus interface 15 is a generic interface that is used to handlethe communication between various control units in the vehicle 1. Thecommunication bus comprises one or more wires, where control units in a vehiclecan communicate with each other using a standardized protocol. ln other words,the communication bus 15 serves both as an input and as an output. Thecommonly used Controller Area Network, CAN, bus is one example of a robustvehicle bus standard designed to allow microcontrollers and devices to communicate with each other. ln one example implementation in the vehicle 1, the first control unit 10 and thesecond control unit 20 communicate via the communication bus. Furthermore, theoutput 14 of the first control unit 10 is electrically connected (e.g. by an electricalwire) to the input 23 of the second control unit 20.

The control circuitry 11 typically comprises a micro-processor. The control circuitry11 is configured to cause the first control unit 10 to perform all aspects of themethod (Fig. 10) performed by a first control unit 10 described herein. This istypically done by running computer program code stored in the memory 12. The memory 12 is e.g. EPROIVI or a Flash memory.

When a speed signal is received at the input 13, then the control circuitry 11 readsand modifies the received speed signal. l\/lore specifically the control circuitry 11 isconfigured to generate a combined synchronization and speed signal by embedding a first synchronization message l\/l1 in an incoming speed signalreceived on the input 13. ln some embodiments, the first synchronizationmessage l\/l1 is positioned on a pre-defined position in the pulse train. Forexample, it is embedded in a long pulse of the speed signal. The control circuitry11 is also configured to generate a second synchronization message l\/l2. Thesecond synchronization message l\/l2 comprises additional synchronizationinformation. The second synchronization message l\/l2 is in some embodimentsalso embedded in the combined synchronization and speed signal. Alternatively, itis transmitted in another way e.g. on a communication bus. The firstsynchronization message l\/l1 and the second synchronization message l\/l2together indicate a timing of the internal clock. As described in connection withFig. 4 and Fig. 5, this may be implemented in different ways. ln some embodiments, the control circuitry 11 is configured to embed both the firstsynchronization message l\/l1 and the second synchronization message l\/l2 in thecombined synchronization and speed signal. ln some embodiments, the firstsynchronization message l\/l1 is an incoming synchronization pattern thatindicates that an actual synchronization will occur within a pre-defined time andthe second synchronization message l\/l2 is a synchronization pattern indicatesthe timing of the internal clock 16. For example, already briefly described inconnection to Fig. 4, the first synchronization message l\/l1 is an incomingsynchronization pattern preparing the second control unit 20 for a synchronizationpattern that will appear in the close future. The second synchronization messageis then the actual synchronization pattern, that indicate the timing of the internalclock 16 of the first control unit 10. The actual synchronization pattern occurs at aspecific point in time, e.g. when the internal clock 16 of the first control unit 10 isO. The incoming synchronization pattern is not dependent on the timing of theinternal clock 16 of the first control unit. Thus, the incoming synchronizationpattern is e.g. mapped to the long pulse (see. Fig. 3) closest before the actualsynchronization pattern. Thereby, the incoming synchronization pattern is easier for the second control unit to detect, as it will always appear on a “long” pulse. 16 The incoming pulse will make it easier for the second control unit 20 to find theactual synchronization, which may be a shorter pulse pattern. ln some other embodiments, the first synchronization message l\/l1 is asynchronization pattern and the second synchronization message l\/l2 indicates arelation between the synchronization pattern and the internal clock 16. Stateddifferently, as already briefly described in connection to Fig. 5 above, the firstsynchronization message l\/l1 is in some embodiments a synchronization patternthat indicates the timing of the internal clock 16. The second synchronizationmessage l\/l2 then comprises further information that is needed to interpret the firstsynchronization message l\/l1. Examples of such information are number of clocksequences (of the internal clock 16) that have elapsed between a specific timeand the synchronization message or number of clock sequences that haveelapsed since last synchronization message transmitted. Alternatively, theinformation defines the time of the internal clock of the first control unit, when thesynchronization pattern was transmitted. With this solution the synchronizationpattern does not need to be transmitted at a certain point in time (of the internalclock 16). Thus, the synchronization pattern may always be mapped to a “long” pulse, which will increase stability.

The control circuitry 11 is further configured to transmit the first synchronizationmessage l\/l1 and the second synchronization message l\/l2 to the second controlunit 20 at the one or more outputs 14, 15. lf both synchronization messages arepulse patterns embedded in the speed signal (Fig. 4), this step basicallycorresponds to transmitting the speed signal with the embedded (or inserted)pulse sequences on the output 14.

However, if the second synchronization message l\/l2 is a communicationmessage, then the communication bus interface 15, which then serves as anoutput, is also used. ln other words, in some embodiments, the control circuitry 11is configured to transmit the second synchronization message l\/l2 at the communication bus interface 15. 17 lt might be desirable to wait to start transmitting the synchronization messagesuntil the first control unit 10 has learned what the tooth wheel looks like andfinding the position on the wheel. ln other words, in some embodiment the controlcircuitry 11 is configured to interpret the received speed signal and the controlcircuit is configured to generate and/or transmit the first and the secondsynchronization messages in response to interpreting the received speed signal. ln some embodiments, the control circuitry 11 comprises real-time processinghardware configured to generate the combined synchronization and speed signal.ln other words, the proposed solution may require a time processing hardware inthe microprocessor to handle the signal treatment without causing large delays.

Fig. 9 illustrates a corresponding second control unit 20 for use in the vehicle 1 ofFig. 1, according to some embodiments. The second control unit 20 is configuredto receive synchronization and speed information from a first control unit 10 of thevehicle 1, e.g. the first control unit of Fig. 8. ln some embodiments, the secondcontrol unit 20 is a slave control unit of the first control unit 10 being a master control unit.

The second control unit 20 comprises control circuitry 21, memory 22, an input 23,a communication bus interface 25 and an internal clock 26a. The second controlunit 20 typically also comprises a plurality of other components and I/O interfaces.However, for simplicity only the components and l/O interfaces needed to explainthe proposed technique will now be described. ln one example implementation inthe vehicle 1, the first control unit 10 and the second control unit 20 communicatevia the CAN bus. Furthermore, the output 14 of the first control unit is electrically connected (e.g. by an electrical wire) to the input 23.

The internal clock 26 clocks the functionality of the second control unit 20. Theinternal clock 26 can for example be used to timestamp measurement data received on the input 23.

The input 23 is a single wire port configured to receive e.g. the signal transmittedon the output 14 (Fig. 9). ln other words, the input 23 is configured to receive, 18 from the first control unit 10, a combined synchronization and speed signalcomprising a pulse train with a frequency corresponding to a speed of a rotatingobject in the vehicle 1.

The communication bus interface 25 is a generic interface that is used to handlethe communication between various control units in the vehicle 1. Thecommunication bus comprises one or more wires, where control units in a vehiclecan communicate with each other using a standardized protocol. ln other words,the communication bus interface 25 acts both as an input and an output. One example of such an interface is the commonly used CAN bus.

The control circuitry 21 typically comprises a micro-processor. The control circuitry21, is configured to cause the control circuitry 21 to perform all aspects of themethod (Fig. 11) performed by a second control unit 20 described below. This istypically done by running computer program code stored in the memory 22. Thememory 22 is e.g. EPROIVI or a Flash memory.

The control circuitry 21 is configured to detect a first synchronization messagel\/l1, embedded in an incoming combined synchronization and speed signalreceived on the input 23. For example, the control circuitry 21 is configured todetect a pre-determined pulse sequence in the incoming combinedsynchronization and speed signal.

According to some embodiments, the control circuitry 21 is configured to ignorepulse sequences having a frequency above a pre-defined threshold value.Because the first synchronization message l\/l1 typically corresponds to apredetermined position at the tooth wheel the second control unit has knowledgeof when the synchronization event can appear and by in addition limiting themaximum allowed acceleration of the tooth wheel wrong decoding of the signalcan be avoided. l\/lore specifically, as the current speed of the rotating object isknown and the maximum acceleration on the rotating object is also known, onemay calculate expected time slots and the minimum time slot of the combinedsynchronization and speed signal. To enable robust detection, the embedded 19 synchronization pattern should be designed to have shorter time slots than theminimum time slots. lf the combined synchronization and speed signal compriseseven shorter time slots, then it is considered disturbances or noise. Thus, thesynchronization pattern can be monitored in an interval limited by the speed of therotating object and acceleration and the time slots of the synchronization patterndefined by the design. Hence, it is possible to filter out signals that are notpossible synchronization patterns.

The control circuitry 21 configured to receive a second synchronization messagel\/l2 from the first control unit 10. As explained above, the second synchronizationmessage l\/l2 is in some embodiments a pulse pattern embedded in the receivedspeed signal (Fig. 4).

As explained above, the second synchronization message l\/l2 is in someembodiments a pulse pattern embedded in the received speed signal (Fig. 4). lnother words, in some embodiments, the control circuitry 21 is configured toreceive the second synchronization message l\/l2 at the input 23. For example, thefirst synchronization message l\/l1 is an incoming synchronization pattern thatindicates that an actual synchronization will occur within a pre-defined time andthe second synchronization message l\/l2 is a synchronization pattern indicatesthe timing of the internal clock 16 of the first control unit 10.

Alternatively, the second synchronization message l\/l2 is another message e.g. amessage transmitted over the communication bus. Thus, in some embodiments,the control circuitry 21 is configured to receive the second synchronizationmessage l\/l2 at the communication bus interface 25, which then serves as aninput. For example, the first synchronization message l\/l1 is a synchronizationpattern and the second synchronization message l\/l2 indicates a relation between the synchronization pattern and the internal clock 16 of the first control unit 10.

The control circuitry 21 is then configured to determine a timing of an internalclock 16 of the first control unit 10, based on the first synchronization message l\/l1and the second synchronization message l\/l2.

According to some embodiments, the control circuitry 21 is configured to adjust atiming of the internal clock 26 of the second control unit 20 based on thedetermined timing. ln other words, the second control unit adapts its internal clockto match with the first control unit using these synchronization messages. This is typically done gradually whereby intermittent errors will be mitigated.

According to some embodiments, the control circuitry 21 is configured to detect asecond synchronization message l\/l2 being embedded in the incoming combinedsynchronization and speed signal.

The disclosure also relates to a corresponding method for communicatingsynchronization and speed information to a second control unit 20 of the vehicle 1(Fig. 1). The method will now be explained with reference to the flow chartillustrated in Fig. 11, and to the illustrations in the other figures. The method may(at least partly) be implemented as program code, P, stored in a memory 12 in thefirst control unit 10. The method may be performed at any time when the vehicle 1 is operated.

The method comprises receiving S1, from a speed sensor 30, a speed signalcomprising a pulse train with a frequency corresponding to a speed of a rotatingobject in the vehicle 1. For example, a signal representing the speed of a toothwheel on the engine shaft 4 (Fig. 2) is received on the input 13 (Fig. 8).

When receiving the signal, the first control unit analyses the signal then modifiesthe signal to also comprise synchronization information in form of a firstsynchronization message l\/l1. ln other words, the method further comprisesgenerating S3 a combined synchronization and speed signal by embedding a firstsynchronization message l\/l1 in the received speed signal.

The first control unit also creates other information required to interpret the firstsynchronization message l\/l1. Thus, the method further comprises generating S4a second synchronization message l\/l2, wherein the first synchronizationmessage l\/l1 and the second synchronization message l\/l2 together indicate atiming of the internal clock 16. 21 The synchronization messages are then sent to the second control unit, at leastpartly as a part of the combined synchronization and speed signal. ln other words,the method further comprises transmitting S5 the combined synchronization andspeed signal and the second synchronization message l\/l2 to the second control unit. ln some embodiments, the first synchronization message l\/l1 is a pre-determinedpulse sequence embedded in the combined synchronization and speed signal. ln some cases, the first control unit does not begin to transmit the synchronizationmessages until the control unit has learned how the tooth wheel looks like andfinding the position on the wheel. Thus, in some embodiments, the methodcomprises interpreting S2 the received speed signal. Then the generating S3, S4and/or the transmitting S5 is performed in response to the interpreting S2.

As already explained several times, both the synchronization messages may beembedded in the combined synchronization and speed signal. ln other words, insome embodiments, the second synchronization message l\/|2 is also embeddedin the combined synchronization and speed signal. ln some embodiments, the firstsynchronization message l\/l1 is an incoming synchronization pattern thatindicates that an actual synchronization will occur within a pre-defined time andthe second synchronization message l\/l2 is an actual synchronization pattern thatindicates the timing of the internal clock 16.

Alternatively, the second synchronization message may be transmitted in anotherway. For example, the second synchronization message lVl2” is a messagetransmitted on a communication bus of the vehicle 1. ln some embodiments, thefirst synchronization message l\/l1 is a synchronization pattern and the secondsynchronization message lVl2” indicates a relation between the internal clock and the synchronization pattern.

Fig. 12 illustrates a corresponding method, for use in a second control unit 20 of avehicle 1, for receiving synchronization and speed information from a first control unit 10 of the vehicle. The method may (at least partly) be implemented as 22 program code, P, stored in a memory 22 in the second control unit 20. The method may be performed at any time when the vehicle 1 is operated.

The method in the second control unit starts when a combined synchronizationand speed signal comprising a pulse train with a frequency corresponding to aspeed of a rotating object in the vehicle 1 is received on an input. ln other words,the method comprises receiving S11, from the first control unit 10, a combinedsynchronization and speed signal comprising a pulse train with a frequencycorresponding to a speed of a rotating object in the vehicle 1.

The second control unit then starts to scan for the first synchronization messagel\/l1. The second control unit is e.g. pre-programmed with information defining asynchronization pattern to scan for. The second control unit may also be pre-programmed with information defining where in the signal (e.g. on a long pulse)synchronization pattern will occur. ln other words, the method further comprisesdetecting S12 a first synchronization message l\/l1, embedded in the receivedcombined synchronization and speed signal. ln some embodiments, the detectingS12 comprises detecting a pre-determined pulse sequence in the incomingcombined synchronization and speed signal. ln some embodiments, the detectingS12 comprises ignoring pulse sequences having a frequency above a pre-definedthreshold value.

The method further comprises receiving S13 a second synchronization messagel\/l2 from the first control unit. ln some embodiments, receiving S13 the secondsynchronization message l\/l2 comprises detecting a synchronization pattern beingembedded in the combined synchronization and speed signal. ln someembodiments, the first synchronization message l\/l1 is an incomingsynchronization message and the second synchronization message l\/l2 is asynchronization pattern that indicates a timing of the internal clock 16 of the first control unit 10. ln some embodiments, receiving S13 the second synchronization message l\/l2 comprises receiving the second synchronization message lVl2” at a 23 communication bus. ln some embodiments, first synchronization message l\/l1 is asynchronization pattern and the second synchronization message l\/l2” indicates arelation between the synchronization pattern and a timing of the internal clock 16of the first control unit 10.

The second control unit can now determine the timing of the internal clock firstcontrol unit 10 and consequently also the drift of its own internal clock in relationthereto. ln other words, the method further comprises determining S14 a timing ofan internal clock 16 of the first control unit 10, based on the first synchronization message l\/l1 and the second synchronization message l\/l2. ln some embodiments, the method comprises adjusting S15 a timing of aninternal clock 26 of the second control unit 20 based on the determined timing.

The present disclosure is not limited to the above-described preferredembodiments. Various alternatives, modifications and equivalents may be used.Therefore, the above embodiments should not be taken as limiting the scope ofthe disclosure, which is defined by the appending claims.

Claims

1. A first control unit (10) for use in a vehicle (1), the first control unit (10)comprising: - an internal clock (16), - an input (13) configured to receive, from a speed sensor (30), a speedsignal comprising a pulse train corresponding to a speed of a rotatingobject in the vehicle (1), - one or more outputs (14, 15) configured to enable transmission to asecond control unit (20), - control circuitry (11) configured to: 0 generate a combined synchronization and speed signal byembedding a first synchronization message (l\/l1) in an incomingspeed signal received on the input (13), 0 generate a second synchronization message (l\/l2), wherein thefirst synchronization message (l\/l1) and the secondsynchronization message (l\/l2) together indicate a timing of theinternal clock (16), and 0 transmit the combined syrichronizatšon and speed signal first and the second synchronizationmessage (l\/l2) to the second control unit (20) at the one or moreoutputs (14, 15).

2. The first control unit (10) according to claim 1, wherein the one or moreoutputs (14, 15) comprises a single-wire output port (14), and wherein thecontrol circuitry (11) is configured to transmit the combined synchronizationand speed signal at the single-wire output port (14).

3. The first control unit (10) according to any of the preceding claims, wherein theone or more outputs (14, 15) comprises a communication bus interface (15)and wherein the control circuitry (11) is configured to transmit the second synchronization message (l\/l2) at the communication bus interface (15).

4. _ The first control unit (10) according to claimg 1 or 2, wherein the control circuitry (11) is configured to embed both the first synchronization message(l\/l1) and the second synchronization message (l\/l2) in the combinedsynchronization and speed signal.

5. _ The first control unit (10) according to claim 4, wherein the first synchronization message (l\/l1) is an incoming synchronization pattern that indicates that anactual synchronization will occur within a pre-defined time and wherein thesecond synchronization message (l\/l2) is a synchronization pattern indicatesthe timing of the internal clock (16).

6. _ The first control unit (10) according to any of the preceding claims, wherein the rotating object is a tooth wheel and wherein the speed sensor (30) is a tooth wheel sensor.

7. _ A second control unit (20) for use in a vehicle (1 ), the second control unit (20) comprising: - an internal clock (26), - one or more inputs (23, 25) configured to receive, from a first controlunit (10), a combined synchronization and speed signal comprising apulse train with a frequency corresponding to a speed of a rotatingobject in the vehicle (1), and - control circuitry (21) configured to: 0 detect a first synchronization message (l\/l1), embedded in anincoming combined synchronization and speed signal receivedon the one or more inputs (23, 25), 0 receive a second synchronization message (l\/l2) from the firstcontrol unit (10), and 5 3 0 determine a timing of an internal clock (16) of the first control unit(10), based on the first synchronization message (l\/l1) and thesecond synchronization message (l\/l2).

8. The second control unit (20) according to claim 7 wherein the control circuitry(21) is configured to adjust a timing of an internal clock (26) of the second control unit (20) based on the determined timing.

9. The second control unit (20) according to anyeëclaims 7 aaeifggß, wherein thecontrol circuitry (21) is configured to detect a pre-determined pulse sequence in the incoming combined synchronization and speed signal.

10.A power train (2) comprising the first control unit according to any one ofclaims 1 to 6 and the second control unit (20) according to any one of claims 7to 9.

11.A vehicle (1) comprising the power train (2) according to claim 10.

12.A method, for use in a first control unit (10) in a vehicle (1), for communicatingsynchronization and speed information to a second control unit (20) of thevehicle (1), wherein the first control unit (10) has an internal clock (16), themethod comprising: - receiving (S1), from a speed sensor (30), a speed signal comprising apulse train with a frequency corresponding to a speed of a rotatingobject in the vehicle (1), - generating (S3) a combined synchronization and speed signal byembedding, a first synchronization message (l\/l1) in the received speedsignal, - generating (S4) a second synchronization message (l\/l2), wherein thefirst synchronization message (l\/l1) and the second synchronizationmessage (l\/l2) together indicate a timing of the internal clock (16) and 4 transmitting (S5) the combined synchronization and speed signal andthe second synchronization message (l\/l2) to the second control unit(20).

13.A method, for use in a second control unit (20) of a vehicle (1 ), for receiving synchronization and speed information from a first control unit (10) of the vehicle, the method comprising: receiving (S1 1), from the first control unit (1 O), a combinedsynchronization and speed signal comprising a pulse train with afrequency corresponding to a speed of a rotating object in the vehicle(1), detecting (S12) a first synchronization message (l\/l1), embedded in thereceived combined synchronization and speed signal, receiving (S13) a second synchronization message (l\/l2) from the firstcontrol unit, determining (S14) a timing of an internal clock (16) of the first controlunit (1 O), based on the first synchronization message (l\/l1) and the second synchronization message (l\/l2).

14.A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to any one of the preceding claims 12 to 13.

15. A computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to any one of claims 12 to 13.