Suppression of a motor vehicle network bus message to reduce battery discharge

Abstract

An electronic control module in a vehicle is powered by a battery during a key-off state. The electronic control module has a bus interface for transmitting messages to and receiving messages from a multiplex bus. These messages include a periodic sequence of network management messages (NM messages) transmitted during normal operation. A control circuit within the module is configured to detect a key-off state of the vehicle, in which the use of power from the battery within the vehicle is limited, to detect the battery's state of charge (SOC), and to compare the detected SOC to a critical battery threshold.The control circuit is further configured to determine an elapsed time that begins when the OFF state is detected and the SOC is no longer above the critical battery threshold, and if the elapsed time is greater than a time threshold, the sequence of NM messages is prevented.

Description

AREA OF TECHNOLOGY

[0001] The present invention relates generally to bus communication between electronic motor vehicle control units and in particular to the control of bus messages during times when electronic control units should enter a sleep mode in order to save battery power reserves while a vehicle is switched off. GENERAL STATE OF THE ART

[0002] A typical automotive electrical system relies on a storage battery to start an internal combustion engine (and / or close the high-voltage contactors for a hybrid vehicle) and to power electrical auxiliary consumers when the engine is not running. Many modern electronic vehicle systems operate continuously, even when the vehicle is parked and unattended, with the battery as the only available power source. Some electronic modules that require power at all times include those that perform functional operations while parked (e.g., anti-theft systems and remote access systems), and those that require only a reduced amount of power to maintain memory contents or to monitor / measure various conditions or electrical communication signals (e.g., in sleep mode).Other modules can continue to operate for a predetermined time after the driver has switched off the vehicle, however, after the predetermined time the power supply may be discontinued (e.g. interior lighting).

[0003] Since a vehicle can remain parked for extended periods, it is important to limit battery discharge so that sufficient charge remains to power the vehicle (e.g., to start an internal combustion engine in a gas-powered vehicle or to close the main contactors in an electric or hybrid vehicle) when the user returns. The vehicle manufacturer typically specifies limits on the current drawn by various modules under each of the possible conditions. In particular, a key-off load (KOL) strategy may be specified, which sets quiescent current limits for the modules.Different KOL modes with varying limits for different modules can be applied based on (i) the duration the vehicle ignition switch has been in the OFF position with no user activity, and / or (ii) the battery's state of charge. The sum of all quiescent currents should be sufficiently low to extend the vehicle's ability to start for a sufficiently long period. Nevertheless, the possibility remains that the battery will become depleted and, after a certain period, will be unable to start the combustion engine / activate the hybrid system.

[0004] Whenever a battery discharges and the vehicle cannot be started, even though the time the vehicle was idling was shorter than the duration a properly functioning battery can handle, it is common practice to replace the battery under the assumption that it is faulty. However, a discharged battery can occasionally be caused by software malfunctions that prevent the battery from discharging to its resting level. For example, if one or more of the electronic modules are activated at times when they should be in sleep mode, this could lead to premature battery discharge. These software malfunctions may not represent a permanent failure and can be difficult to detect, as the software may be fully restored after the next ignition cycle.Therefore, the battery may be replaced unnecessarily.

[0005] Serial multiplex communication between electronic modules located within a vehicle has become widely adopted. One commonly used communication protocol is the Controller Area Network (CAN), which efficiently supports distributed real-time control with a high degree of reliability. Interconnected modules include engine control units, infotainment modules, navigation components, sensor units (e.g., cameras, radar, ultrasonic devices), anti-lock braking systems, electric power steering systems, and other systems. A CAN bus connecting these modules can have a bit rate of up to 1 Mbit / s. By using multiplex systems, the size of the wiring harness can be reduced while improving communication speed and flexibility.

[0006] A twisted pair of wires can be used to form a multiplex bus (e.g., CAN bus) that connects bus transceivers in the respective nodes (i.e., control units or modules). Each module draws its power from a power line (extending, for example, from a power distribution box) carrying a DC supply voltage (e.g., 12 VDC). Each module is capable of entering one or more low-power modes, such as an inactivity mode and a sleep mode (completely powered off). Each specific module incorporates its own unique programming based on the functions it needs to perform and the conditions under which the module must be active or can enter a low-power mode.Before actually entering a sleep mode, it is typical practice for a module to enter an inactivity mode in which at least some functions (including transmitting and receiving bus messages) are maintained. For example, the open AUTOSAR system architecture specifies that modules in an active mode periodically transmit network management messages (NM messages) during times when other modules on the same bus need to remain active and available. When a particular module detects conditions under which it should be able to enter a sleep state, it enters the inactivity mode and monitors for NM messages indicating that it needs to postpone its full sleep mode. Only after there have been no NM messages for a predetermined period does the module enter a downregulated state (e.g.,a sleep mode or a completely powered-off state).

[0007] Whenever a software malfunction or other fault prevents a module from properly entering its downregulated state, it can continue to transmit NM messages, preventing other modules that receive these NM messages from exiting their idle mode. Thus, a fault in one module has a cascading effect, where power discharge remains high during a period when all or most of the modules should be in sleep mode. BRIEF SUMMARY OF THE INVENTION

[0008] In one aspect of the invention, an electronic control module for a vehicle is provided, wherein the vehicle includes a battery for powering the electronic control module. The electronic control module has a bus interface for transmitting messages to and receiving messages from a multiplex bus, wherein the messages include a periodic sequence of network management messages (NM messages) transmitted during normal operation. A control circuit is configured to detect an OFF state of the vehicle, in which the use of power from the battery within the vehicle is limited, to detect a state of charge (SOC) of the battery, and to compare the detected SOC with a critical battery threshold.The control circuit is further configured to determine an elapsed time that begins when the OFF state is detected and the SOC is no longer above the critical battery threshold, and if the elapsed time is greater than a time threshold, the sequence of NM messages is suppressed (i.e. interrupted or blocked). BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic representation showing electronic modules coupled via a CAN bus. Fig. Figure 2 is a block diagram showing an embodiment of an electrical architecture for distributing electrical power and multiplexed communication signals, in which KOL power management is implemented. Fig. Figure 3 is a flowchart showing a procedure used by a module to monitor NM messages and, if necessary, enter a sleep mode. Fig. Figure 4 is a state diagram showing an embodiment of a process for selectively interrupting the transmission of NM messages. Fig. Figure 5 is a block diagram showing a control arrangement for selectively stopping NM messages according to an embodiment of the invention. Fig. Figure 6 is a flowchart showing a preferred embodiment of the invention. Fig. Figure 7 is a graphical progression showing a variable time threshold selected according to a battery charge level. Fig. Figure 8 is a table showing incremental extensions of the variable time threshold according to the number of separate subnetworks with which a module can communicate. DETAILED DESCRIPTION OF PREFERRED EXECUTION FORMS

[0009] Fig. Figure 1 shows a multiplex network, wherein an electronic control unit or electronic module 10 is connected via a connector 11 to a CAN multiplex bus 12, which includes twisted pairs of wires designated CAN-H and CAN-L. A DC power line 13 supplies electrical DC power to the module 10 and to modules 14 and 15, each of which includes the same multiplex functionality as shown for module 10.

[0010] Module 10 receives and utilizes DC power via a wired connection 16. A bus transceiver 17 operates in conjunction with a CAN controller 18. The bus transceiver 17 has output terminals 20 and 21 for transmitting or receiving complementary signals according to a CAN protocol. Output terminals 20 and 21 are connected to an interface circuit 22 and an isolator circuit 23. The isolator circuit 23 is normally in a non-isolating state, allowing the flow of CAN bus messages between the bus 12 and the bus transceiver 17. Fig. Figure 1 shows an exemplary embodiment for preventing the transmission of NM messages under predetermined conditions. For example, when the controller 18 detects these predetermined conditions, it can provide a signal to the interface circuit 22, which then reconfigures the isolator 51 to block outgoing messages from the transceiver 17. In some alternative embodiments, the controller 18 can instead include software instructions that prevent any such NM messages from being initiated under the predetermined conditions.

[0011] Fig. Figure 2 shows an example of a power distribution within an electrical system 25, which includes a storage battery 26 connected to a battery monitoring system (BMS) 27. The BMS 27 can be a conventional component that, among other things, measures the battery current flowing from the battery 26 to the electrical consumers. A body control module (BCM) 30 and a BMS 27 are both contained in a bus network and communicate via a bus network 31, such as a CAN bus. Bus communication lines (not shown) for bus network 31 wind between the BMS 27, the BCM 30, modules 30, 33-35, 37 and 44 and a powertrain control module (PCM) 40. Bus network 31 is connected to a gateway 32, which is further connected to additional bus networks 45 and 46, which can operate using the same or different protocols.In different cases, the gateway 32 reformats messages and forwards them between networks, allowing modules in different bus networks to exchange communication signals, as is known in the field. A power bus 28 distributes an output from the battery 26 to various modules, including the BCM 30 and many other modules, including modules 33-35, which are interconnected by the bus network 31. Module 37 and the PCM 40 are controlled by the BCM 30 to use the battery power as a separate subnetwork 36. Control messages from the BCM 30 can also include commands that control power output to subordinate components of a control module (e.g., sensors 41 and actuators 42, which receive their power from the PCM 40).

[0012] In another example of power management, the PCM 30 is connected to a relay 43, which receives power from the power bus 28 and selectively transmits power to a module 44. Relay 45 could, for example, be an ignition relay. Module 44 is further connected to the bus network 31. Relay 43 can be controlled by a direct signal connection to the BCM 30 or alternatively via a multiplex message. However, instead of having a sleep mode, module 46 is either fully powered or not powered at all, depending on the ON / OFF state of relay 45. On the other hand, most of the modules (including modules 33-35 and modules 37 and 40 in subnetwork 36) are always powered by the power bus 28, but each enters a corresponding reduced-power mode, such as a sleep state, if necessary.

[0013] During times when a vehicle's ignition switch is ON or in an ACCESSORY state, electronic control units coupled to a multiplex bus are typically active (i.e., in a power-on mode). For network management purposes and to coordinate shutdowns into respective sleep modes for different modules according to a KOL strategy, it may be necessary for each module to periodically send network management (NM) messages to all other nodes on the bus while it is active. For example, a module might transmit a periodic sequence of NM messages at a predetermined frequency (e.g., a heartbeat) of several hertz. Typically, modules are programmed to detect when circumstances indicate that they should attempt to enter a reduced-power mode (e.g., a sleep mode).Once this is detected, the modules can enter an inactivity mode in which the module waits for NM messages sent by other modules on the bus (no messages are transmitted by a module in inactivity mode). Fig. Figure 3 shows a procedure that runs in a module which entered an inactivity mode at step 50. At step 51, an NM timeout timer is started (or restarted), which is used to determine the elapsed time since the last NM message was received. At step 52, a check is performed to determine if an NM message is detected. If an NM message is detected, the NM timeout timer is restarted at step 51. If no NM message is detected, a value from the timeout timer is compared to a predetermined time threshold (e.g., 90 seconds). If it is below the threshold, the process returns to step 52 to monitor for an NM message. Once the elapsed time exceeds the threshold, the module enters a sleep mode at step 54.By delaying sleep mode in all modules on a bus, each module actively communicating on the bus has the ability to complete its message sequence before all modules in an entire group on a bus enter sleep mode.

[0014] Thus, a module only enters its sleep mode (in which it stops monitoring for bus messages) if no NM messages have been received for a threshold period. Whenever a specific module cannot properly enter its inactivity mode, it would continue to transmit its NM messages, and these messages would prevent other modules in their inactivity mode from entering their sleep modes. Under these circumstances, battery power is consumed at a rate higher than intended by the KOL strategy.

[0015] The invention helps to ensure that a module experiencing a fault that would otherwise prevent it from ceasing its continuous transmission of NM messages nevertheless stops the NM messages and allows other modules to enter their sleep modes. To prevent it from becoming the module that erroneously prevents other modules from entering their sleep mode, a monitoring procedure is integrated into the operation of each module. The procedure may preferably consist of programming instructions in each module configured to prevent the module from transmitting NM messages under certain trigger conditions. These trigger conditions may include one of several of the following: (1) the battery charge level is below a predetermined percentage, (2) the ignition state is OFF, and (3) a duration for which NM messages have been transmitted exceeds a time threshold.In particular, a trigger condition may include the battery SOC falling below a predetermined percentage (e.g., 40%) or decreasing at a certain rate after falling below a somewhat higher threshold (e.g., a 2% decrease in SOC within one hour once the SOC has fallen below 55%). Preferably, all conditions 1-3 may need to be true for NM messages to be stopped. In some embodiments, a fourth trigger condition is used, requiring the absence of any overriding battery power conservation concerns.Conditions that exempt a module from the need to suspend its NM messages may include periods when the specific module is part of any feature that should be allowed to discharge the battery to zero charge, such as illuminating external signaling lights (warning lights), operating a wireless transceiver, or a vehicle security function (e.g., a door locking process). Once a module has determined that NM messages should be suspended, the suspension of NM message transmission preferably lasts until the next normal activation of the network bus.

[0016] Fig. Figure 4 shows a state diagram illustrating the operation of a control module according to one embodiment of the invention. The module is initially in state 56, in which the transmission of NM messages is unlimited. When a set of trigger conditions (referred to as condition set no. 1) occurs, the module transitions to state 57, in which a timer is operated to detect whether the transmission of NM messages continues for longer than a time threshold (e.g., approximately 5 seconds). Condition set no. 1 may consist of the vehicle being OFF (i.e., inactive and / or unoccupied) and the battery state of charge (SOC) being less than a critical threshold. As long as condition set no. 1 remains true and the transmission of NM messages remains active, state 57 is maintained. When condition set no. 1 is no longer true, the module transitions back to state 56.When the timer expires in state 57, a transition to state 58 occurs. In state 58, communication is interrupted, thus halting NM messages. The module controller waits in state 58 until an external activation action or process is detected, at which point a transition back to state 56 occurs. Similarly, if any aspect of condition set no. 1 is not true (e.g., the vehicle ignition switch is turned on), a transition back to state 56 occurs.

[0017] Fig. Figure 5 shows a logic circuit for determining when to stop NM message transmissions. A vehicle state logic block 60 determines a vehicle state using the ignition switch status (ON or OFF), the gear selector position (in park or out of park), the vehicle speed (stationary or not moving), or the door status (open or closed). When all these factors agree that the vehicle is in an inactive state, a high logic level signal is sent from block 60 to an input of an AND gate 61. A battery level logic block 62 compares a state of charge (SOC) value from a battery monitoring device to a predetermined battery percentage, which represents a critical battery level. A high logic level signal is sent from the battery level logic block 62 to another input of the AND gate 61 when the battery SOC is at or below the critical level.A message activity logic block 63 compares the duration for which NM messages have been cyclically transmitted after both the critical battery level and the vehicle state have been detected as OFF. If the duration is longer than the time threshold, a high-level logic signal indicating an extended duration of NM message activity is sent from logic block 63 to another input of AND gate 61. An exception logic block 64 can use a lookup table or other electronic resources (e.g., available via the multiplex bus) to determine whether any exception conditions exist. If none exist, a high-level logic signal is sent to another input of AND gate 61.When all four inputs to the AND gate 61 are at a high logic level, a high logic level output is provided by the AND gate 61, which can be used to assume a state within the control module that prevents the sending of NM messages on the multiplex bus until either the full bus system is activated or a change occurs in the vehicle that causes one of the original conditions to no longer be true.

[0018] Fig. Figure 6 shows a method of the invention in which a specific module connected to a multiplex bus determines whether or not to send regular NM messages while it is active. In step 70, a check is performed to determine whether the vehicle state is OFF. An OFF state can be based on the position of an ignition switch being OFF (which can also be verified by determining that the vehicle is motionless and has a speed of zero or that the gear selector lever is in a park position). Once step 70 detects that the vehicle state is OFF, a check is performed in step 71 to determine whether the battery charge level has reached a critical level (e.g., below a predetermined percentage). If no critical battery level is detected and the vehicle remains in an OFF state, the battery level is checked again in step 71.Once the battery state of charge (SOC) falls below the critical level, a check is performed in step 72 to determine if the module is in a normal operating (active) state with regular, cyclic transmission of NM messages. As long as NM messages are not being transmitted cyclically, the module does not prevent other modules from entering sleep mode, and no action is required. If cyclic NM message transmission is present, a timer is started in step 73. The timer's timeout threshold can be approximately 5 seconds or another period (e.g., in the range of approximately 2 to 10 seconds) chosen to ensure that any ongoing communication function required by the module has time to complete before a message interruption begins.

[0019] Step 74 performs a check to determine if the cyclic transmission of NM messages is continuing. If so, step 75 performs a check to determine if the timer has expired. If a timer expiration is detected in step 75, step 76 performs a check to determine if an override exception exists. If an exception is detected (e.g., the specific module is involved in performing a high-priority feature that should continue to be allowed regardless of the battery SOC), communication is not stopped in step 77. Otherwise, cyclic NM message transmission is stopped in step 78.Preferably, NM messages continue to be suppressed until the next occurrence of a bus activation event or until one of the trigger conditions changes, such as the ignition switch moving to an ON state.

[0020] As mentioned above, the time threshold for pausing the cyclic transmission of NM messages can be approximately 5 seconds. In some embodiments, the time threshold can be a dynamic parameter that changes in response to different levels of the battery state of charge (SOC). Fig. Figure 7 illustrates a relationship between a threshold time and a battery state of charge (SOC), where, as the battery state of charge decreases, the threshold time becomes shorter to allow other modules in a multiplex circuit to transition from inactivity to sleep mode sooner. Similarly, the battery's age or state of health (SoH) can be used to further adjust the time threshold. For example, a shorter time threshold can be assumed as the battery ages.

[0021] On the other hand, a longer time threshold can be useful when multiple multiplex buses communicate via gateways, as message forwarding between nodes on different bus segments can take a considerable amount of time. As in Fig.As shown in Figure 8, an incremental extension corresponding to the number of buses that may be present within a specific vehicle's multiplex network can be included in the time threshold. The proof time increment can be proportional to the number of bus segments. For example, if there are two interconnected buses, the time threshold can be increased by 1 second, and if there are four buses, the time increment can consist of a 4-second extension.

[0022] According to the present invention, a method for operating an electronic control module for a vehicle, wherein the vehicle includes a battery for powering the electronic control module, comprises the following steps: transmitting messages to and receiving messages from a multiplex bus, wherein the messages include a periodic sequence of network management messages (NM messages) transmitted during a normal operating mode; detecting an OFF state of the vehicle in which the use of power from the battery within the vehicle is limited; detecting a state of charge (SOC) of the battery; comparing the detected SOC with a critical battery threshold; determining an elapsed time that begins when the OFF state is detected and the SOC is no longer above the critical battery threshold;and preventing the periodic sequence of NM messages when the elapsed time is greater than a time threshold.

[0023] In one aspect of the invention, the suppression of the periodic sequence of NM messages is prevented when an exception condition exists that allows battery power to be consumed below the critical battery threshold.

[0024] In one aspect of the invention, the time threshold lies in a range of 2 seconds to 10 seconds.

[0025] In one aspect of the invention, the time threshold is dynamically determined in response to the detected SOC.

[0026] In one aspect of the invention, the time threshold includes an extension time increment when the multiplex bus is connected to another bus segment through at least one gateway.

Claims

[1] Electronic control module for a vehicle, wherein the vehicle includes a battery for supplying power to the electronic control module, the electronic control module comprising: a bus interface for transmitting messages to and receiving messages from a multiplex bus, wherein the messages include a periodic sequence of network management messages (NM messages) transmitted during a normal operating mode; and a control circuit that is coupled to the bus interface and configured as follows: Detecting an OFF state of the vehicle, in which the use of power from the battery within the vehicle is limited; Detecting the battery's state of charge (SOC); and Comparing the detected SOC with a critical battery threshold; the control circuit is further configured as follows: Determining an elapsed time that begins when the OFF state is detected and the SOC is no longer above the critical battery threshold; and Preventing the periodic sequence of NM messages when the elapsed time is greater than a time threshold. [2] Electronic control module according to claim 1, wherein the sequence of NM messages remains blocked until the control circuit detects an external reactivation action. [3] Electronic control module according to claim 1, wherein the control circuit is further configured to prevent the suppression of the periodic sequence of NM messages when an exception condition exists that allows battery power to be consumed below the critical battery threshold. [4] Electronic control module according to claim 1, wherein the time threshold is in a range of 2 seconds to 10 seconds. [5] Electronic control module according to claim 1, wherein the time threshold is dynamically determined in response to the detected SOC. [6] Electronic control module according to claim 5, wherein the time threshold is determined according to a relationship, wherein a reduction in the detected SOC corresponds to a shorter time threshold. [7] Electronic control module according to claim 1, wherein the time threshold includes an extension time increment when the multiplex bus is connected to another bus segment via at least one gateway. [8] Electronic control module according to claim 7, wherein the extension time increment is proportional to a number of bus segments connected to the multiplex bus. [9] Electronic control module according to claim 1, wherein the OFF state is detected in response to an OFF position of an ignition switch of the vehicle. [10] Transport vehicle comprising: a battery; a multiplex bus; and an electronic control module powered by the battery, the electronic control module comprising the following: a bus interface for transmitting messages to and from the multiplex bus, wherein the messages include a periodic sequence of network management messages (NM messages) transmitted during a normal operating mode of the electronic control module; and a control circuit coupled to the bus interface and configured to (A) detect an OFF state of the vehicle in which the use of power from the battery within the vehicle is limited, (B) detect a state of charge (SOC) of the battery, (C) compare the detected SOC with a critical battery threshold, (D) determine an elapsed time that begins when the OFF state is detected and the SOC is no longer above the critical battery threshold, and (E) suppress the periodic sequence of NM messages when the elapsed time is greater than a time threshold. [11] Transport vehicle according to claim 10, wherein the periodic sequence of NM messages remains suppressed until the control circuit detects an external reactivation action. [12] Transport vehicle according to claim 10, wherein the control circuit is further configured to prevent the suppression of the periodic sequence of NM messages when an exception condition exists that allows battery power to be consumed below the critical battery threshold. [13] Transport vehicle according to claim 10, wherein the time threshold is in a range of 2 seconds to 10 seconds. [14] Transport vehicle according to claim 10, wherein the time threshold is dynamically determined in response to the detected SOC. [15] Transport vehicle according to claim 10, wherein the time threshold includes an extension time increment when the multiplex bus is connected to another bus segment via at least one gateway.

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