Vehicle multiplexing bus system using backup power line communication

Abstract

The invention provides a vehicle multiplexing bus system using backup power line communication. Multiplexed communications in a vehicle are provided by a multiplexed bus, such as a CAN bus, using complementary signals. Bus redundancy for providing a backup communication channel in the event of a failure on a primary multiplexed bus is achieved using power line communication (e.g., transmitting data through a DC power line that has been available). The need for additional circuitry is minimized by preserving the same message protocol (e.g., framing) because only signal conversion, filtering, and switching functions are required to transfer messages via the power line.

Description

Technical Field

[0001] The present invention relates generally to multiplexing communications between electronic modules in a transportation vehicle and, more particularly, to providing a backup communication channel in the event of a failure in a primary communication bus. Background Art

[0002] Serial multiplexed communications between electronic modules arranged within a vehicle have been widely adopted. For example, the Controller Area Network (CAN) is a commonly used communication protocol that effectively supports distributed real-time control with a high level of reliability. Interconnected modules have included engine control units, infotainment modules, navigation components, sensor units (e.g., cameras, radar, ultrasonic), anti-lock braking systems, electric power steering systems, and other systems that use the CAN bus with a bit rate of up to 1 Mbit / s. The use of a multiplexed system can reduce the size of the wiring harness while increasing communication speed and flexibility.

[0003] When a multiplexed bus is intended to communicate certain critical data, enhancements may be needed that help ensure that important messages can be sent and received even in the presence of anomalies. Known enhancements have included bus redundancy using added physical components and / or software, with associated financial expenditures. Summary of the invention

[0004] In one aspect of the present invention, an electronic component or module in a vehicle includes a bus transceiver having a pair of transceiver output terminals adapted to be coupled to a multi-line multiplexed bus, wherein the multiplexed bus transmits multiplexed messages as complementary signals in the vehicle. A DC power input terminal is adapted to be coupled to a power line, the power line supplying DC power to a plurality of electronic modules in the vehicle. A subtractor generates a single-ended differential signal according to a voltage difference between the pair of transceiver output terminals. A balanced signal generator has a single input adapted to receive an AC component of a voltage at the power input terminal. The balanced signal generator has a pair of balanced outputs, the pair of balanced outputs providing a differential signal to the transceiver output terminal according to a remote differential signal transmitted to the power line by one of the plurality of electronic modules. A first switch selectively couples the single-ended differential signal from the subtractor to the power input terminal when in a conductive state. A second switch selectively couples the single input of the balanced signal generator to the power input terminal when in a conductive state. The controller is configured to 1) detect a fault associated with the multiplexed bus, 2) switch the first switch and the second switch into the conductive state when the fault is detected, and 3) otherwise switch the first switch and the second switch out of the conductive state. Thus, when the fault is detected, the multiplexed message is transmitted on the power line in an unchanged message frame. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 is a schematic diagram showing a known multiplexed communication bus system employing a redundant bus.

[0006] 2 is a schematic diagram illustrating a known multiplexed communication bus system employing a backup communication link to a primary bus.

[0007] FIG. 3 is a schematic diagram showing a known power line communication system.

[0008] Figure 4 is a schematic block diagram illustrating one embodiment of the present invention.

[0009] Figure 5 is a schematic block diagram illustrating one embodiment of an electronic module configured to perform one embodiment of the present invention.

[0010] Figure 6 is a flow chart illustrating one embodiment of a method according to the present invention. DETAILED DESCRIPTION

[0011] A typical CAN network has multiple nodes in a stub-based / daisy-chain-based topology. A twisted pair of wires forms the CAN bus, which interconnects the bus transceivers in the nodes. At the same time, each node gets its power from a power line (e.g., extending from a distribution box) carrying a DC supply voltage (e.g., 12VDC).

[0012] The present invention employs primary communication via a multiplexed bus, such as a CAN bus or other multi-line bus that uses complementary (i.e., differential) signals to send messages. Bus redundancy is achieved using power line communication (e.g., sending data over an already available DC power line) to provide a backup communication channel in the event of a failure on the primary multiplexed bus. The need for additional circuitry is minimized by retaining the same message protocol (e.g., framing), as the present invention only requires signal conversion, filtering, and switching functions to transfer messages via the power line.

[0013] Referring to FIG1 , a plurality of electronic modules 10, 11, and 12 are interconnected by separate multiplexed buses 13 and 14, either of which can be utilized to transmit multiplexed messages between the respective modules. In order to provide full redundancy, the first bus 13 and the second bus 14 can utilize independent and different bus hardware. For example, the module 10 includes separate bus transceivers 15 and 16 for communicating via the first bus 13 and the second bus 14, respectively. Therefore, if a problem occurs using one of the buses, the multiplexed communication can be immediately transferred via the remaining bus.

[0014] FIG. 2 shows another known practice in which a plurality of modules 20, 21 and 22 communicate via a multiplexed bus 23 primarily using bus transceivers 24, 25 and 26. Partial redundancy is also achieved by interconnecting modules 20 and 21 via an alternative bus 27. A signal diverter 28 is connected to module 20, and a signal diverter 29 is connected to module 21. Signal diverters 28 and 29 normally allow multiplexed messages to flow between bus 23 and modules 20 and 21, respectively. However, if diverters 28 and 29 detect a failure associated with bus 23, they route the message via bus 27 instead. While the arrangements of FIGS. 1 and 2 achieve redundancy and increase the likelihood that critical data messages are received at their intended destination, a significant amount of additional circuitry and programming is required.

[0015] FIG3 shows a power line communication system of a known type in which a battery 30 and a regulator 31 distribute power via a power line 32. A pair of modules 33 and 34 receive a supply voltage via the power line 32 while also transmitting serial messages between them using a pair of transmitters T and a pair of receivers R. The power line communication system of FIG3 may have the disadvantages of reduced robustness and reduced reliability (compared to FIGS. 1 and 2 ) because the communication signals are single-ended (i.e., complementary or differential signals cannot be employed) and because the communication speed may be reduced.

[0016] Figure 4 One embodiment of the invention is shown in which an electronic component or module 35 is connected to a CAN multiplexed bus 37 comprising a twisted wire pair of lines labeled CAN-H and CAN-L via a connector 36. A DC power line 38 supplies DC power to module 35 and to modules 40 and 41, each of which includes the same multiplexing functionality as shown for module 35.

[0017] Module 35 receives and utilizes DC power via wired connection 42. Wired connection 43 between power line 38 and module 35 is used to carry multiplexed messages in the event of a fault (or potential fault) detected in the lines of bus 37, which may affect the transmission of CAN messages between modules 35, 40 and 41. In module 34, bus transceiver 44 works with CAN controller 45 in a conventional manner. Bus transceiver 44 has output terminals 46 and 47 for transmitting or receiving complementary signals in accordance with the CAN protocol. Output terminals 46 and 47 are connected to interface circuit 50 and to isolator circuit 51. Isolator circuit 51 is usually in a non-isolated state, which allows CAN bus messages to flow between bus 37 and bus transceiver 44. Bus transceiver 44 and bus controller 45 may include conventional functions for identifying the presence of a fault or anomaly (such as an open circuit or a short circuit) on bus 37. When the controller 45 detects the presence of a fault, it provides a signal to the interface circuit 50, which automatically reconfigures itself to a state in which 1) the interface circuit transmits CAN messages between the bus transceiver 44 and the power line 38, and 2) the interface circuit sends a signal to the isolator 51 on the general purpose input / output (GPIO) line 57 to block signals to or from the multiplexed bus 37. Modules 40 and 41 can simultaneously perform the same functions of detecting multiplexed bus faults and diverting multiplexed communications to the power line 38.

[0018] Figure 5Module 35 is shown in greater detail. Input terminals 53 conduct 12 volt DC power from power line 38 through smoothing filter 54 to voltage regulator module (VRM) 55. The regulated DC output (eg, +5 VDC) is supplied to internal components including microprocessor / controller 45.

[0019] CAN messages to be transmitted to another module are provided to the transceiver 44 by the controller 45 via the transmission line Tx. CAN messages from other modules are received by the transceiver 44 and arrive at the controller 45 via the receiving line Rx for decoding. The output terminals 46 and 47 of the transceiver 44 are connected to the coupling network 56 to provide appropriate bus terminations, which may generally include filtering for electrostatic discharge and electromagnetic interference (e.g., using filtering capacitors). A pair of contacts 60 and 61 between the coupling network 56 and the bus isolation circuit 51 transmit CAN communication signals according to the selected protocol (e.g., CAN-FD). When the bus isolation circuit 51 is in a conductive state, CAN communication generally occurs through the multiplexed bus 37. In the case where the controller 45 or the transceiver 44 detects a fault associated with the multiplexed bus 37 (e.g., an open circuit to one of the lines, a short circuit between the bus lines, or a short circuit between one of the lines and the ground or supply voltage), the bus isolation circuit 51 switches to an isolated (non-conductive) state so that the transceiver 44 is isolated from the bus 37. In isolated conditions, the interface circuit 50 is operated to transmit messages to or from the power line 38 after converting the signal to a single-ended signal suitable for transmission on a single conductor referred to as ground.

[0020] To send a CAN message, the contacts 60 and 61 that make the complementary signals suitable for normal CAN transmission are coupled to the non-inverting input 63 and the inverting input 64 of the subtractor operational amplifier 62. The output 65 of the subtractor operational amplifier 62 provides a single-ended differential signal according to the voltage difference between the transceiver output terminals 46 and 47. The output 65 is connected to one terminal of a FET 66, which acts as a switch to selectively couple the single-ended differential signal from the subtractor operational amplifier 62 to the power input terminal 53 through an AC coupling capacitor 67 when in a conductive state. The FET 66 has a gate terminal 68, which is coupled to the controller 45 via a GPIO line 70. The controller 45 provides a gate drive signal through line 70 so that the FET 66 is normally in a non-conductive state. When the controller 45 detects a fault associated with the multiplexed bus 37, it inverts the gate drive signal to switch the FET 66 to a conductive state. Thus, the expected CAN message is coupled to the power line 38 and can be received by other modules. Since the CAN message is only converted to a single-ended differential signal, it is transmitted on the power line with an unchanged message frame. Therefore, no additional circuitry or software is introduced with regard to forming the message. Likewise, the single-ended differential signal can be converted back to a complementary signal at the receiving node, so that the message can be decoded using an existing CAN transceiver.

[0021] To receive a CAN message, an AC voltage from the power line 38 is received at the power input terminal 53 and coupled to a second FET 71 via a capacitor 67 and a FET 66. The FET 71 has a gate terminal 72 that is connected to a GPIO line 73 to receive a gate drive signal that places the FET 71 in a conductive state during a fault condition. When the FET 71 is conducting, the AC signal from the power input terminal 53 is coupled to an input 75 of a balanced signal generator 74. The generator 74 includes an operational amplifier configured as a single input balanced output device that takes the input voltage and splits it into two outputs 76 and 77 that drive the contacts 60 and 61 to reproduce a normal CAN message received from a remote electronic module via the power line 38.

[0022] Although controller 45 is shown as having GPIO lines 57, 70, and 74, a preferred embodiment of the present invention may utilize a single GPIO line that 1) generates a first output level when no fault is detected, wherein the first output level turns off FETs 66 and 71 and turns on isolator 51, and 2) generates a second output level during a fault, wherein the second output level turns on FETs 66 and 71 and turns off isolator 51. During the inactive state when no fault is detected, FET 66 prevents the converted CAN signal from coupling to power line 38, and FET 71 prevents any output signal from subtractor op amp 62 from being processed by balanced signal generator 74. During the active state when a fault is detected and FET 71 is turned on, the CAN message converted by op amp 62 can be received back to transceiver 44, as is typical in a CAN network. If necessary, a delay can be introduced to avoid signal interference. The delay may be implemented within operational amplifier 74 or in the conduction of FET 71 compared to FET 66 (eg, by selecting a different FET device or by adding an RC delay circuit at the gate terminal).

[0023] Figure 6 A preferred method of the present invention is shown in FIG. In step 80, during a normal condition where no fault is detected on the multiplexed bus, the control signal from the controller on the general purpose input output has a low value or a logic 0 value, so that the FET switch is turned off and the bus isolator is inactive (i.e., conductive). Therefore, in step 81, CAN communication occurs over the twisted pair multiplexed bus. In step 82, a check is performed to determine whether any fault problem is detected on the CAN-H or CAN-L line. If not, the control signal maintains a low value in step 80. Otherwise, it is determined in step 83 that the transceiver in the electronic module should be isolated from the CAN bus. In step 84, the control signal is switched to a high level (e.g., logic 1) in step 84 to ensure that the FET switch is closed and the bus isolator is disconnected (i.e., not conductive). In this fault state, in step 85, the CAN message is converted to a differential signal and coupled to the power line. In step 86, the received signal from the power line is converted to a differential pair. Therefore, despite the presence of a fault on the CAN bus, CAN messages still flow into and out of the electronic module. In step 87, a check is performed to determine if a fault continues to exist on one or both of the CAN lines. If so, the fault active state continues in steps 85 and 86. Otherwise, a return is made to step 80 such that the FET and bus isolator return to their inactive states, thereby allowing normal CAN communications.

[0024] According to one embodiment, the respective first switch comprises a first field effect transistor (FET), wherein the respective second switch comprises a second FET, and wherein the respective first FET and the respective second FET have respective gate terminals coupled to receive respective gate drive signals from the respective controller.

[0025] According to one embodiment, the respective controller comprises a microprocessor, and wherein the respective gate drive signal comprises a general purpose input / output of the respective microprocessor.

[0026] According to one embodiment, each electronic component further comprises a respective bus isolator responsive to a general purpose input / output of the respective controller for decoupling the respective bus transceiver from the multiplexed bus upon detection of a fault.

Claims

1. An electronic component in a vehicle, comprising: a bus transceiver having a pair of transceiver output terminals adapted to couple to a multi-line multiplexed bus, wherein the multiplexed bus transmits multiplexed messages as complementary signals in the vehicle; a DC power input terminal adapted to be coupled to a power line that supplies DC power to a plurality of electronic modules in the vehicle; a subtractor that generates a single-ended differential signal based on a voltage difference between the pair of transceiver output terminals; a balanced signal generator having a single input adapted to receive an AC component of a voltage at the power input terminal, wherein the balanced signal generator has a pair of balanced outputs adapted to provide a differential signal to the transceiver output terminal in accordance with a remote differential signal transmitted to the power line by one of the plurality of electronic modules; a first switch adapted to selectably couple the single-ended differential signal from the subtractor to the power input terminal when in a conductive state; a second switch adapted to selectably couple the single input of the balanced signal generator to the power input terminal when in a conductive state; as well as a controller configured to 1) detect a fault associated with the multiplexed bus, 2) switch the first switch and the second switch into the conductive state upon detection of the fault, and 3) otherwise switch the first switch and the second switch out of the conductive state; Thus, when the fault is detected, the multiplexed message is transmitted on the power supply line in an unchanged message frame.

2. The electronic component according to claim 1, further comprising: A bus isolator is responsive to the controller and adapted to decouple the bus transceiver from the multiplexed bus upon detection of the fault.

3. The electronic component according to claim 1, further comprising: An AC coupling capacitor is adapted to be connected between the first switch and the power line.

4. The electronic component of claim 1 , wherein the second switch is connected between the first switch and the balanced signal generator, whereby the single input of the balanced signal generator is coupled to the power input terminal when both the first switch and the second switch are in the conductive state.

5. The electronic component of claim 1, wherein the subtractor comprises a first operational amplifier having an inverting input and a non-inverting input, the inverting input and the non-inverting input each being coupled to a corresponding one of the transceiver output terminals.

6. The electronic component of claim 1, wherein the balanced signal generator comprises a second operational amplifier, wherein the balanced outputs are both biased to a predetermined voltage.

7. The electronic component of claim 1, wherein the first switch comprises a first field effect transistor (FET), wherein the second switch comprises a second FET, and wherein the first FET and the second FET have respective gate terminals coupled to receive a gate drive signal from the controller.

8. The electronic component of claim 7, wherein the controller comprises a microprocessor, and wherein the gate drive signal comprises a general purpose input / output of the microprocessor.

9. The electronic component according to claim 8, further comprising: A bus isolator is responsive to the general purpose input / output of the controller for decoupling the bus transceiver from the multiplexed bus when the fault is detected.

10. A vehicle comprising: a multi-line multiplexed bus wired within the vehicle for transmitting multiplexed messages as complementary signals; a power cord that supplies DC power in the vehicle; as well as A plurality of electronic components, each of the plurality of electronic components comprising: a bus transceiver having a pair of transceiver output terminals coupled to the multi-lane multiplexed bus; a DC power input terminal coupled to the power line; a subtractor that generates a single-ended differential signal based on a voltage difference between the pair of transceiver output terminals; a balanced signal generator having a single input adapted to receive an AC component of a voltage at the power input terminal, wherein the balanced signal generator has a pair of balanced outputs adapted to provide a differential signal to the transceiver output terminal in accordance with a remote differential signal transmitted to the power line by another electronic component of the plurality of electronic components; a first switch adapted to selectably couple the single-ended differential signal from the subtractor to the power input terminal when in a conductive state; a second switch adapted to selectably couple the single input of the balanced signal generator to the power input terminal when in a conductive state; and a controller configured to 1) detect a fault associated with the multiplexed bus, 2) switch the first switch and the second switch into the conductive state upon detection of the fault, and 3) otherwise switch the first switch and the second switch out of the conductive state; Thus, when the fault is detected, the multiplexed message is transmitted on the power supply line in an unchanged message frame.

11. The vehicle of claim 10, wherein each electronic component further comprises: A bus isolator is responsive to the respective controller and adapted to decouple the respective bus transceiver from the multiplexed bus upon detection of the fault.

12. The vehicle of claim 10, wherein each electronic component further comprises: An AC coupling capacitor is adapted to be connected between the corresponding first switch and the power line.

13. The vehicle of claim 10, wherein the respective second switch is connected between the respective first switch and the respective balanced signal generator, whereby the single input of the respective balanced signal generator is coupled to the respective power input terminal when both the first switch and the second switch are in the conductive state.

14. The vehicle of claim 10, wherein the respective subtractor comprises a respective first operational amplifier having an inverting input and a non-inverting input, the inverting input and the non-inverting input each being coupled to a respective one of the respective transceiver output terminals.

15. The vehicle of claim 10, wherein the respective balanced signal generators include respective second operational amplifiers, wherein the respective balanced outputs are each biased to a predetermined voltage.

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