DRIVER WARNING IN ELECTRIC POWER STEERING SYSTEMS

Abstract

Steering system (40), which includes: a first motor control system (612) configured to send a first command to a first motor (614) in a steering wheel actuator (510); a second motor control system (622) designed to send a second command to a second motor (624) in a road wheel actuator (520); a controller (16) designed to to set a fault indicator by monitoring one or more components of the steering system (40); and to generate a warning injection signal in response to the fact that the fault indicator flag is set; wherein the steering wheel actuator (510) is configured to generate initial driver feedback by modifying the initial command using the warning injection signal and sending the modified initial command to the initial motor (614); and wherein the road wheel actuator (520) is designed to generate a second driver feedback by modifying the second command using the warning injection signal and sending the modified second command to the second motor (624), wherein the warning injection signal comprises a first injection signal and a second injection signal and wherein the controller (16) is further configured to: to generate the first injection signal based on a fault detected in the steering wheel actuator (510); to generate the second injection signal based on a fault detected in the road wheel actuator (520); and to evaluate the first injection signal and the second injection signal in order to generate the warning injection signal.

Description

BACKGROUND

[0001] The present application relates generally to electric power steering systems (EPS systems) and specifically to the provision of driver warnings using EPS.

[0002] German patent application DE 100 25 492 A1 discloses a device for providing feedback on the current vehicle status of a vehicle, wherein the device uses signals from a vehicle dynamics control unit and signals from driving system components to generate a feedback signal which in turn is used to provide optical, acoustic and / or haptic driver feedback. Similar devices are known from German patent applications DE 196 32 929 C1 and DE 103 02 268 A1.

[0003] Safety requirements in a modern EPS necessitate advanced fault monitoring, encompassing both predictive and diagnostic capabilities, to ensure the safe operation of both the EPS's hardware and software components. Due to improved diagnostics, there is an increasing need to provide warnings as the EPS approaches a fault condition or once a fault has occurred. With the incorporation of fault-tolerant control into a modern EPS, typical methods of notifying the driver have emerged. These include reducing the assistance provided by the EPS, making it feel sluggish to the driver, and essentially prompting the driver to proactively bring the EPS in for repair. SUMMARY

[0004] One of the aims of the invention is to increase user-friendliness and road safety.

[0005] The problem is solved according to the invention by the subject matter of the independent claims. Advantageous embodiments are defined in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The subject matter considered to be the invention is specifically described and detailed in the claims at the end of the description. The features and advantages of the invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings, which: Fig. 1 represents an EPS system in accordance with one or more embodiments; Fig. 2 a block diagram of the EPS system with an exemplary driver warning module in accordance with one or more embodiments; Fig. 3 represents a block diagram of part of an exemplary driver warning system in accordance with one or more embodiments; Fig. 4. A flowchart illustrating an exemplary procedure for providing driver warning feedback in accordance with one or more embodiments is shown; Fig. 5 is an exemplary embodiment of a steer-by-wire steering system (SbW steering system) in accordance with one or more embodiments; Fig. 6 represents a block diagram and an operating sequence in a steer-by-wire system which includes a driver warning system in accordance with one or more embodiments; Fig. 7 a block diagram with separate fault monitoring systems for the steering wheel actuator and the road wheel actuator in accordance with one or more embodiments; and Fig. Figure 8 shows a flowchart for a method for generating driver feedback / warning in a steer-by-wire system in accordance with one or more embodiments. DETAILED DESCRIPTION

[0007] The terms module and submodule, as used here, refer to one or more processing circuits, such as an application-specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and / or other suitable components that provide the described functionality. As can be seen, the submodules described below can be combined and / or further subdivided.

[0008] Referring now to the figures, in which the technical solutions are described with reference to specific embodiments, without limiting them, it is Fig. 1 An exemplary embodiment of an electric power steering system (EPS system) 40 suitable for implementing the disclosed embodiments. The steering mechanism 36 is a rack and pinion system and includes a (not shown) toothed rack in a housing 50 and a (also not shown) pinion gear arranged under a gear housing 52. When the operator input, hereafter referred to as the steering wheel 26 (e.g., a handwheel and the like), is turned, the upper steering shaft 29 rotates, and the lower steering shaft 51, which is connected to the upper steering shaft 29 by a universal joint 34, rotates the pinion gear.The rotation of the pinion gear moves the rack, which moves the tie rods 38 (only one is shown), which in turn move the steering knuckles 39 (only one is shown), which rotate one or more steerable / turnable wheels 44 (only one is shown).

[0009] The electric power steering assistance is provided by the control device, generally designated by reference numeral 24, which includes the controller 16 of an electric machine 46. This machine can be a permanent magnet synchronous motor, a permanent magnet DC motor, a switched reluctance motor, or any other type of motor, and is hereinafter referred to as the motor 46. The controller 16 is supplied with power from the vehicle power supply 10 via a line 12. The controller 16 receives a vehicle speed signal 14 from a vehicle speed sensor 17, representing the vehicle speed. A steering angle is measured by a position sensor 32, which can be an optically coded sensor, a variable resistance sensor, or another suitable type of position sensor, and the controller 16 is supplied with a position signal 20.Motor speed can be measured with a tachometer or other device and transmitted to the controller 16 as a motor speed signal 21. This signal is represented as ω. m The designated motor speed can be measured, calculated, or a combination of both. For example, the motor speed ω m The change in motor position θ, measured by a position sensor 32 over a predetermined time interval, can be calculated. For example, the motor speed ω can be calculated. m as the derivative of the motor position θ from the equation ω m The motor speed can be determined as Δθ / Δt, where Δt is the sampling time and Δθ is the change in position during the sampling interval. Alternatively, the motor speed can be derived from the motor position as the rate of change of position over time. It should be noted that there are numerous well-known methods for performing a derivative function.

[0010] When the steering wheel 26 is turned, a torque sensor 28 detects the torque applied to the steering wheel 26 by the vehicle operator. The torque sensor 28 may include a torsion bar (not shown) and a variable resistance sensor (also not shown) that outputs a variable torque signal 18 to the controller 16 in proportion to the amount of rotation of the torsion bar. Although this is one type of torque sensor, any other suitable torque sensing device using known signal processing techniques will also suffice. In response to the various inputs, the controller sends a command 22 to the electric motor 46, which provides torque assistance to the steering system via a worm gear 47 and a worm wheel 48, thus providing torque assistance for the vehicle steering.

[0011] It should be noted that although the disclosed embodiments are described by reference to a motor control system for electric steering applications, it should be emphasized that these references are for illustrative purposes only and that the disclosed embodiments can be applied to any motor control application that uses an electric motor, e.g., steering, valve control, and the like. Furthermore, the references and descriptions contained herein can apply to many types of parameter sensors, including, without limitation, torque, position, speed, and the like. It should also be noted that, for the sake of brevity and simplicity, references contained herein to electrical machines, which include but are not limited to motors, will be referred to hereafter simply as "motors."

[0012] In the depicted control system 24, the controller 16 uses the torque, position, speed, and similar data to calculate one or more commands for delivering the required output power. The controller 16 communicates with the various systems and sensors of the motor control system. The controller 16 receives signals from each of the system sensors, quantifies the received information, and, in response, provides one or more output command signals, in this case, for example, for the motor 46. The controller 16 is designed to generate the necessary voltages from an inverter (not shown), which can optionally be integrated into the controller 16 and is referred to here as the controller 16, so that when applied to the motor 46, the desired torque or position is generated.Since these voltages are related to the position and speed of the motor 46 and the desired torque, the position and / or speed of the rotor and the torque applied by an operator are determined. A position encoder is connected to the steering shaft 51 to detect the angular position θ. The encoder can detect the rotational position based on optical detection, variations in a magnetic field, or other methods. Typical position sensors include potentiometers, resolvers, synchros, encoders, and the like, as well as combinations comprising at least one of the above. The position encoder outputs a position signal 20 indicating the angular position of the steering shaft 51 and thus that of the motor 46.

[0013] The desired torque can be determined by one or more torque sensors 28, which transmit torque signals 18 indicating an applied torque. One or more exemplary embodiments comprise such a torque sensor 28 and the torque signals 18 from it and can respond to a compliant torsion bar, a torsion rod, a spring, or a similar (not shown) device configured to provide a response indicating the applied torque.

[0014] In one or more examples, one or more temperature sensors 23 are arranged on the electric machine 46. Preferably, the temperature sensor 23 is configured to directly measure the temperature of the sensing section of the motor 46. The temperature sensor 23 transmits a temperature signal 25 to the controller 16 to enable the processing and compensation described herein. Typical temperature sensors include thermocouples, thermistors, thermostats, and the like, as well as combinations comprising at least one of the aforementioned sensors, which, when suitably positioned, provide a calibratable signal proportional to the specific temperature.

[0015] In addition to other signals, the position signal 20, the speed signal 21, and one or more torque signals 18 are applied to the controller 16. The controller 16 processes all input signals to generate values ​​corresponding to each signal, resulting in a rotor position value, a motor speed value, and a torque value available for processing in the algorithms described here. Measurement signals such as those mentioned above are also frequently linearized, compensated, and filtered, as desired, to improve their characteristics or eliminate undesired characteristics of the acquired signal. For example, the signals can be linearized to improve processing speed or to address a large dynamic range of the signal. Furthermore, frequency- or time-based compensation and filtering can be applied to eliminate noise or to avoid undesired spectral characteristics.

[0016] To perform the prescribed functions and the desired processing and calculations (e.g., the identification of motor parameters, control algorithms, and the like), the controller 16 can, without restriction, include one or more processors, computers, DSPs, main memory, mass storage, registers, timers, interrupts, communication interfaces, and interfaces for input / output signals, as well as combinations thereof comprising at least one of the above. For example, the controller 16 can include input signal processing and filtering to enable accurate sampling and conversion or the acquisition of such signals from communication interfaces. Additional features of the controller 16 and specific processes within it will be discussed in detail later.

[0017] In one or more examples, the technical solutions described here allow the electric drive component of the EPS system, and more specifically the motor control loop (including the current (torque) control system, the electric motor, and various sensors), to be used to provide a warning to the driver when a fault is either about to occur (prediction) or has already occurred (diagnosis) and the EPS 40 is still operating. The warning can be provided to the driver through feedback in various ways, including tactile feedback, audible feedback, and the like, or a combination thereof.Since fail-safe states can potentially persist over time (for example, if the driver has decided to maintain operation, even with reduced support, for periods exceeding predetermined thresholds), which can occur within a single ignition cycle or over multiple cycles, the technical solutions described here further enable the implementation of a time-varying warning mechanism, which is also described, where the level of warning feedback changes over time. The warning system, in accordance with the technical solutions described here, can be implemented identically regardless of the configuration of the engine control system (i.e., feedback control or feedforward control).The technical solutions described here address the technical challenge of providing active feedback to a driver using an EPS (Electrodynamic Performance System) to display a diagnosis and / or a predictive status. These solutions thus improve a typical EPS by providing a notification system with active feedback.

[0018] Fig. Figure 2 shows a block diagram of the EPS according to one or more embodiments. The controller 16 of the EPS 40 includes a steering control module 210, which generates an engine torque command based on one or more control signals, including, for example, steering wheel torque and engine speed. The steering control can use any algorithm to determine the torque command. In one or more examples, the controller 16 further includes a power limiting module 220, which modifies the engine torque command based on predetermined limits, which may be configurable. In one or more examples, the predetermined limits are calculated by the controller 16 in real time; alternatively, the predetermined limits are preconfigured values. The modified torque command is provided as an input torque command to an engine control system 230.

[0019] Upon receiving the input torque command, the motor control system 230 generates the corresponding voltage commands to be sent to the inverter 260, so that the inverter 260 applies a voltage to the motor 46 to generate the desired torque (Te). The generated torque is applied to the mechanical system 36 to, for example, maneuver the wheel 44. In one or more examples, the generated torque includes the assist torque, which amplifies the steering torque applied by the driver during the driver input 26.

[0020] Furthermore, the controller 16 includes a fault monitoring system 240, which monitors one or more components of the EPS 40, including its hardware and software components. For example, the fault monitoring system 240 monitors the mechanical components, for instance, using one or more sensors, and compares the sensor readings with estimated values ​​calculated using an electromechanical model of the EPS 40. If the measured values ​​exceed the estimated values ​​by predetermined thresholds, the fault monitoring system 240 assumes that a fault condition has occurred (diagnosis) or is about to occur (prediction).

[0021] In one or more examples, the fault monitoring system 240 generates markers that indicate either an impending fault, referred to below as a predictive marker P, or the occurrence of a fault, referred to as a diagnostic marker D. The markers can be binary values, such as software markers. Furthermore, in one or more examples, the fault monitoring system 240 monitors multiple components in the EPS 40, and therefore P and D can be matrix values ​​indicating the status of the multiple components. The technical solutions described here enable the provision of a warning / feedback to the driver regardless of which specific component causes the setting of one or more fault markers and / or regardless of how the fault monitoring system 240 detects the fault condition.

[0022] In response to one of the P and D markers being set by the fault monitoring system, the controller 16 typically either causes the EPS 40 to be shut down, which may include disconnecting the power supply, switching off the gate driver (and thus the inverter), and disabling various functions within the EPS 40 (such as software components), or it causes the system behavior of the EPS 40 to be modified by changing specific functions or tuning. For example, if the system behavior needs to be changed, say for a current sensor fault, the fault monitoring system 240 initiates a torque command modification and switches the motor control system 230 from a control mode to a feedforward mode.

[0023] The technical solutions described here, in addition to modifying system behavior, enable signal injections and command modifications to provide driver warning feedback. In one or more examples, the injected signal is superimposed on the base signals calculated by one or more components of the controller 16. The base signals and commands are the control signals and commands, such as the torque command, the current command, and the voltage command, generated by one or more components of the controller 16. In one or more examples, the base commands can be replaced by the warning injection signals.

[0024] For example, the controller contains, as in Fig. Figure 2 shows a driver warning system 250 that receives the markers D and P from the fault monitoring system 240 and generates the signal injections and / or command modifications.

[0025] Fig. Figure 3 shows a block diagram of an exemplary driver warning system in accordance with one or more embodiments. As shown, the driver warning system 250 includes, among other components, a fault monitoring and evaluation module (FMA module) 310, an injection signal calculation module 330, and a fault duration monitoring module 340.

[0026] The FMA module 310 assesses the type of markers set by the fault monitoring system 240 and determines the warning signal(s) to be generated for the driver. By determining the warning signal(s), the FMA module 310 determines the type of warning feedback generated for the driver. The driver warning feedback can be tactile, audible, or a combination of both. Furthermore, the driver warning feedback can be determined based on a specific signature of a fault detected by the fault monitoring system 240. For example, the signature could be a status of the diagnostic and predictive marker(s) of the fault monitoring system 240. Alternatively or additionally, the fault monitoring system 240 sends the signature as a separate signal to the FMA module 310, for example, upon request from the FMA module 310.

[0027] Based on the type of warning feedback to be generated, the injection signal calculation module 330 calculates the injection signal and sends it to the appropriate module / location in the controller 16. The injection signal calculation module 330 receives other control signals, such as position, engine speed, vehicle speed, and the like, which are used to determine the various warning injection signals. For example, the injection signal calculation module 330 calculates pulsed injection signals to modify the torque command, current command, and / or voltage command. The pulsed signals can be fixed-frequency signals or functions of position and / or speed, e.g., a sinusoidal signal with a frequency equal to an integer multiple of the engine speed.As another example, the sinusoidal signal can have a frequency that is an integer multiple of the position signal, i.e., a harmonic of the motor's fundamental frequency.

[0028] For example, the injection signal calculation module 330 generates a warning torque signal (T) for torque command signal injection. wi *), which has a fixed or varying (command-based) frequency. In one or more examples, the injection signal calculation module 330 generates the warning torque signal as a function of one or more control signals in the EPS 40, such as engine speed, vehicle speed, acceleration, bridge voltage, etc.

[0029] Furthermore, the injection signal calculation module 330 generates a warning current signal (I) for current command signal injection. wi *), which is a directly pulsating component that is injected into electrical commands.

[0030] Furthermore, the injection signal calculation module 330 generates a warning voltage signal (V) for voltage command signal injection. wi *), which has a fixed or varying (command-based) frequency. In one or more examples, the injection signal calculation module 330 generates the warning voltage signal with a fluctuating frequency, which is a time-varying frequency around a predetermined switching frequency of the motor 46 control loop. Alternatively or additionally, in one or more examples, the injection signal calculation module 330 generates the warning voltage signal with a fixed control loop frequency.

[0031] Furthermore, the injection signal calculation module 330 generates multiple warning injection signals for several commands in one or more examples, for instance, a combination of different signals, such as simultaneous torque and voltage injection signals. The various injection signals can be constant-value signals or periodically varying signals generated using fixed or varying (command-based) frequencies. In one or more examples, the combination of injection signals is fed into the control loop in a coordinated manner to generate the driver warning feedback.

[0032] Furthermore, the injection signal calculation module 330 generates injection signals in one or more examples that simulate sensor errors, which cause a modification of the system behavior. For example, the sensor error injection signals contain gain or offset errors in current, position, voltage, and / or temperature signals, or in any other sensor signals used in the EPS 40, such as those used by the steering control 210, the engine control 230, or any other component of the controller 16. In the case of a resolver position sensor (sine-cosine sensor), a quadrature error between the sine and cosine signals can also be simulated.In other words, the injection signal calculation module 330 manipulates one or more sensor signals received by the controller 16 (or any other component) by calculating a constant-value or pulsating signal for injection into the sensor signal(s) to create a sensor fault condition. In one or more examples, the fault signal injection is performed as harmonic injection into the sensor signals.

[0033] The sensor signals can be modified in this way by injecting a faulty pulsation into them in cases where the motor control loop rejects the warning injection signals for the current, torque, and / or voltage commands as interference. For example, voltage signals are interference signals for the current control loop of the motor controller, and if a high-bandwidth current feedback control loop is used, these signals can be (partially) rejected by the control loop. This is especially true for lower-frequency voltage signals.

[0034] In one or more examples, the injected signals simulate fault conditions in one or more hardware components (such as inverters or gate drivers). In response to the introduction of the simulated faults and their subsequent detection by the fault monitoring system 240, a driver warning message is generated. For example, a fault condition simulation might involve setting one of the voltage outputs of the voltage command generation module to zero to simulate a short circuit of the lower FET from one of the phase legs of the inverter, and so on. Other fault simulations are possible in other examples.

[0035] The warning signals injected into the basic commands cause the driver warning feedback to be tactile, audible, or a combination of both. The pulsing frequency used for the warning signal injection determines whether the warning feedback is tactile, audible, or a combination thereof. For example, due to the implementation of a low-bandwidth control loop and the bandwidth limitations of the control loop for torque and current commands, the torque or current commands are used to generate tactile feedback. Alternatively or additionally, voltage injection is used for audible feedback, as relatively higher frequencies can be injected directly into voltage commands compared to torque and current commands.Furthermore, the injection mechanism, such as signal transmission paths in the EPS 40, can also partially lead to the use of a type of signal injection to generate tactile and / or acoustic warning feedback.

[0036] Again with reference to Fig. 3. The Fault Duration Module 320 determines the duration of the fault. For example, using a store / restore feature of non-volatile memory, the Fault Duration Module 320 tracks whether the fault persists over multiple ignition cycles, the number of kilometers the fault has persisted, the time the EPS 40 has been operated with the persistent fault, and other such attributes associated with the persistent fault. The Fault Duration Module 320 can also track the number of times driver feedback regarding the persistent fault has been provided. Based on the tracked information, the Fault Duration Module 320 modifies the injection signal amplitudes accordingly. Alternatively or additionally, the Fault Duration Module 320 modifies the injection signal to provide injection signals in bursts, i.e., intermittent injection.

[0037] Fig. Figure 4 illustrates a flowchart for an exemplary procedure for providing driver warning feedback in accordance with one or more embodiments. The procedure includes detecting a fault condition at the EPS 40, as shown in block 405. The fault monitoring system 240 detects the fault condition, which may be a diagnostic or a predictive condition. Accordingly, the fault monitoring system 240 sets a diagnostic and / or a predictive marker. The driver warning system 250 monitors the fault condition markers and generates driver warning feedback in response.

[0038] Generating the driver warning feedback involves the FMA module 310 determining the type of warning feedback to be generated, as shown in block 410. For example, the FMA module 310 can determine that the warning feedback is tactile, audible, or a combination thereof. The type of warning feedback can be determined based on the type of marker that is set. Alternatively or additionally, the type can be determined based on the type of fault condition.

[0039] Based on the driver warning feedback to be generated, the injection calculation module 330 calculates a warning injection signal, as shown in block 420. In one or more examples, the warning injection signal is a periodic signal. Calculating the warning injection signal involves determining the signal's amplitude and frequency. For example, a warning injection signal used to generate an audible driver warning signal differs from a warning injection signal used to generate a torque driver warning signal. In one or more examples, the injection signal calculation module 320 calculates the amplitude, phase, and frequency based on one or more control signals from the EPS 40, such as engine speed, steering wheel speed, engine position, vehicle speed, or any other control signal.In one or more examples, the warning injection signal may not have a periodic frequency and instead be a constant signal with a frequency of zero.

[0040] Furthermore, the procedure includes determining whether the duration of the fault condition exceeds a predetermined threshold, as shown in Block 430. The predetermined threshold can be a configurable value, which can be calculated in real time in one or more examples, for instance, based on additional fault conditions / changes in EPS 40. If the predetermined threshold is not exceeded, the calculated warning injection signal is not modified and is sent to the engine control loop to generate tactile / audible driver warning feedback, as shown in Block 450.

[0041] If the duration is exceeded, the fault duration monitoring module 320 adjusts the warning injection signal, as shown in block 440. For example, if the fault condition persists over several ignition cycles, the intensity of the driver warning feedback is adjusted accordingly, for example, increased. The intensity is adjusted by modifying the amplitude, phase, and / or frequency of the warning injection signal. For example, depending on the severity of the fault condition, which may be predefined and accessible via a lookup table, the frequency at which the driver warning feedback is provided is changed. Alternatively or additionally, the amplitude is changed based on the severity. Alternatively or additionally, the phase is changed based on the severity. In one or more examples, all three parameters—amplitude, frequency, and phase—or a combination thereof, are modified.

[0042] The modified warning injection signal is then delivered to the engine control loop to generate tactile / audible driver warning feedback, as shown in Block 450. The delivery location of the warning injection signal depends on the type of command being modified. For example, if a torque command is modified, the warning injection signal is injected into a mixing module, such as an adder, which receives the torque command and superimposes the warning injection signal onto the base torque command. The modified torque command is then delivered to the engine control system to produce modified torque using Motor 46. Alternatively, or additionally, if the current command is modified, the warning injection signal is superimposed onto the current command by a mixing module, and the modified current command is then used to produce the torque.Alternatively or additionally, the voltage command is modified by superimposing the warning injection signal, and the modified voltage command is used by the motor control system to generate the corresponding torque through motor 46. Furthermore, instead of superimposing or mixing, the original control signals, comprising torque, current, and voltage, can be entirely replaced by the warning signal values.

[0043] The torque generation by the motor provides tactile and / or acoustic feedback to the rider, as the modified commands change the provided support torque and / or the noise generated by the motor 46.

[0044] The technical solutions described here enable the driver to be alerted using the engine control loop in an EPS system in the event of fault conditions detected by diagnostic and predictive monitoring. These solutions allow the use of control signals that utilize one or more EPS components to generate assist torque, thereby generating the driver warning feedback. Furthermore, these solutions enable the generation of both audible and tactile driver warning feedback. Finally, they allow the type and intensity of the feedback to be varied over time.The technical solutions described here improve typical driver feedback systems that use passive feedback to the user by enabling active feedback to be provided to the driver using the EPS's electric actuator.

[0045] Fig. Figure 5 is an exemplary embodiment of a steer-by-wire (SbW) steering system in accordance with one or more embodiments. It should be noted that the SbW system 40 shown and described can be used in an autonomous or semi-autonomous vehicle or in a more conventional vehicle.

[0046] The SbW system 40 includes a steering wheel actuator (HWA) 510 and a road wheel actuator (RWA) 520.

[0047] The HWA 510 includes one or more mechanical components 512, such as the steering wheel 26 (handwheel), the steering column, and a motor / inverter attached to the steering column either by a gear mechanism or a direct drive system. The HWA 510 also includes a microcontroller 514 that controls the operation of the mechanical components 512. The microcontroller 514 receives and / or generates torque via the one or more mechanical components 512.

[0048] The RWA contains one or more mechanical components 522, such as a steering rod and / or a gear, which is coupled to a motor / inverter by a (gearbox) assembly with a ball nut / ball screw, and the rack is connected to the road wheels 44 / tires of the vehicle by tie rods. The RWA 520 also contains a microcontroller 524, which controls the operation of the mechanical components 522. The microcontroller 524 receives and / or generates torque via the one or more mechanical components 522.

[0049] The 512 and 524 microcontrollers are coupled by electrical connections that allow signals to be sent and received. A controller, as described here, can comprise a combination of the 512 HWA controller and the 522 RWA controller, or any of the specialized microcontrollers.

[0050] In one or more examples, the controllers 512 and 522 communicate with each other via a CAN interface (or other similar digital communication protocols). Steering of the vehicle 5100, equipped with the SbW system 40, is performed using the mechanical components 522 of the RWA 520. The RWA 520 receives an electronic communication signal indicating the rotation of the steering wheel 26 by the driver. The driver steers the steering wheel 26 to control the direction of the vehicle 5100. The angle from the HWA 510 is sent to the RWA 520, which performs position control to regulate the rack travel for steering the road wheel 44. However, due to the lack of a mechanical connection between the steering wheel 26 and the road wheels 44, the driver lacks torque feedback and therefore does not receive any road feel (unlike in the case of an EPS, as described above).

[0051] In one or more examples, the HWA 510, coupled to the steering column and steering wheel 26, simulates the driver's feeling for the road. The HWA 510 can apply tactile feedback in the form of torque to the steering wheel 26. The HWA 510 receives a rack force signal from the RWA 520 to generate a suitable torque sensation for the driver. Alternatively, the steering wheel angle and vehicle speed can also be used to generate a desired torque sensation for the driver.

[0052] The technical solutions described here enable the use of the electric drive component of the SbW System 40, and specifically the motor control loop, to provide a warning to the driver if a fault is either about to occur (prediction) or has already occurred (diagnosis) and the System 40 is still in operation. The warning can be provided to the driver through various feedback methods, including tactile feedback, audible feedback, or a combination of both.

[0053] Since fail-safe states may persist for long periods of time (for example, if the driver has decided to continue operation with reduced support for extended periods, which may be within a single ignition cycle or over several cycles), a time-varying warning mechanism is also described, in which the amount of warning feedback is changed over time.

[0054] Safety requirements in modern SbW systems necessitate advanced fault monitoring, encompassing both prediction and diagnostics, to ensure the safe operation of both hardware and software. With improved diagnostics comes an increased need to provide warnings as the system approaches a fault condition or once a fault has occurred. Typical methods for alerting the driver, used in SbW systems as a technology transfer from electric power steering (EPS) systems, include increasing driver torque feedback using the steering wheel actuator (HWA), causing the system to feel heavy and warning the driver to some extent to bring the steering system in for repair.

[0055] The technical solutions described herein further improve the provision of driver feedback by utilizing the HWA 510 to provide both tactile and audible feedback to the driver. However, since two actuators are present in the SbW system 40—namely, the HWA 510 and the RWA 520—the technical solutions described here allow for the implementation of additional systems to provide driver warnings with increased flexibility when faults are either imminent (prediction) or have already occurred (diagnosis) and the SbW system 40 is still operational.

[0056] In accordance with one or more embodiments, the technical solutions described herein enable the use of the HWA 510, specifically the motor control system within the HWA 510, to provide acoustic feedback, tactile feedback, or both through its direct connection to the driver. The technical solutions described herein further enable the use of the RWA 520 to provide acoustic feedback using the electric motor drive, as well as tactile feedback to the driver through vibration of the vehicle chassis.Since fail-safe states can potentially persist for extended periods (for example, if the driver has decided to maintain operation with reduced assistance for long durations), which may occur within a single ignition cycle or over multiple cycles, a time-varying warning mechanism is also described, in which the magnitude of the warning feedback changes over time. It should be noted that a warning system in accordance with one or more embodiments of the technical solutions described herein can be implemented in an identical manner, regardless of the configuration of the engine control system (i.e., control feedback / regulation or feedforward control).

[0057] Fig. Figure 6 shows a block diagram and an operating sequence in an SbW system 40, which includes the driver warning system 250 in accordance with one or more embodiments. The HWA 510 includes an inverter 613, which provides a voltage (V Hm ) is applied to a motor 614 to generate the corresponding steering wheel actuator motor torque (T He ) to generate, which is the electromagnetic motor torque of the steering wheel actuator motor 614. The steering wheel actuator motor torque is applied to the mechanical system / components 615 of the SbW system 40, such as the steering wheel 26, one or more gears, and the like, to move the steering wheel 26 to a position (Θ H to position. In Fig. 6 is (TH*) The steering wheel torque is received from the driver as an input, while the remaining values ​​with suffix “H” represent steering wheel actuator / engine torque values.

[0058] The inverter 613 applies the voltage based on a voltage command (V Hb ) from a motor control system 612. The motor control system 612 generates the input voltage command based on an input torque command (T). Hb ), which is generated by a torque command generator 611 for the steering wheel actuator motor. The torque command generator 611 for the steering wheel actuator motor generates the input torque command based on a reference torque provided by a reference torque generator 610, which in turn is based, among other parameters, on a rack force measured at the RWA 520 by a rack force observer 630.

[0059] In one or more examples, the input voltage command (V) Hb ) modified by the driver warning system 250, in which a first injection signal (V Hw ) is injected to deliver a modified input voltage command (VHm*) to generate a signal that is received by the inverter 613. The modification can involve mixing the input voltage command and the first injection signal using an adder or any other mixing technique. In this case, the first injection signal is a voltage injection signal.

[0060] Alternatively or additionally, the input torque command (T) Hb ) modified by the driver warning system 250 by changing the first injection signal (T Hw ) is injected to deliver a modified input torque command (THm*) to generate a signal that is received by the engine control system 612. The modification can involve mixing the input torque command and the first injection signal using an adder or any other mixing technique. In this case, the first injection signal is a torque injection signal.

[0061] Furthermore, a position command generator 620 generates based on the position (Θ H ) of the steering wheel 26 an input position command (ΘH*) for a road wheel position controller 621. The road wheel position controller 621 generates an input torque command. (TRb*) for provision to a motor control system 622 of the RWA 520. The motor control system 622 in turn generates a corresponding input voltage command. (VRb*) which an inverter 623 inputs to an input voltage (V Rm ) for a motor 624 of the RWA 520. The motor 624 generates a torque (T Re ), which is applied to one or more mechanical system components 625 of the vehicle 650, of which the SbW system 40 is a part. The components 625 include the road wheel 44, which can be positioned accordingly (Θ RThe position / displacement of components 625 is monitored by the rack force observer 630 to determine the reference torque (T̃). R ) to generate the signal used by the HWA 510 to generate the steering wheel torque and steering wheel position as described here.

[0062] In one or more examples, the input voltage command (VRb*) modified by the driver warning system 250 by a second injection signal (V Rw ) is injected to create a modified input voltage (VRm*) to generate a signal that is received by the inverter 623. The modification can involve mixing the input voltage command and the second injection signal using an adder or any other mixing technique. In this case, the second injection signal is a voltage injection signal.

[0063] Alternatively or additionally, the input torque command (TRb*) modified by the driver warning system 250 by the second injection signal (T Rw ) is injected to deliver a modified input torque command (TRm*) to generate a signal that is received by the 622 engine control system. The modification may involve mixing the input torque command and the second injection signal using an adder or any other mixing technique. In this case, the second injection signal is a torque injection signal.

[0064] The driver warning system 250 generates the injection signal(s) based on the output of the fault monitoring system 240. As described here, the fault monitoring system 240 generates a diagnostic marker (D) and a predictive marker (P) (see Fig. 3).

[0065] It should be noted that in both the HWA 510 and the RWA 520, the injection signal from the driver warning system 250 can be a current injection signal used to modify a current command generated by the respective engine control systems 612 / 622 to operate the respective engines 614 / 624.

[0066] The injection signals generated by the driver warning system 250 provide a driver warning by modifying the input commands to the electric drive systems (motor control systems) 612 / 622 of the HWA 510 and the RWA 520. The injected signals are superimposed on the base signals calculated by the various functions. As mentioned above, the driver warning feedback can be tactile, audible, or a combination of both.

[0067] In general, the pulsating command signal injections for torque, current, and voltage can be performed by the driver warning system 250. Torque command injection can be of a fixed or variable frequency (command-based) and can be a function of other signals, including speed, acceleration, bridge voltage, etc. Furthermore, direct injection of pulsating components into current commands can be performed instead of converting torque commands to current. Voltage command injection can be of a fixed or variable frequency (command-based). Additionally, voltage signals can be injected with a fluttering frequency (time-varying frequency around a nominal switching frequency) of the control loop. Alternatively, a low fixed frequency of the control loop can also be used to generate audible sounds.In one or more examples, a combination of torque, current, and voltage commands can be injected in a coordinated manner to produce simultaneous acoustic and tactile feedback.

[0068] Alternatively or additionally, a sensor fault injection is performed to provide a driver warning, which involves injecting gain, offset, or harmonic errors into the current, position, voltage, or temperature sensors. For example, sensor fault injection is used in cases where command injections can be rejected as disturbances by the control loops (in the HWA 510 / RWA 520).

[0069] In one or more examples, the injection signals include torque or current commands for tactile feedback due to their low-bandwidth control loop implementation (control loop bandwidth limitations) and limited response of the mechanical system. Additionally, voltage injection commands are used to provide audible feedback, as higher frequencies can be directly injected into the voltage command (compared to current / torque commands).

[0070] It should be noted that while the injection signals or commands are described as torque, current, or voltage, the actual physical signals that produce the tactile and acoustic signature (or variation) are the torsional torque on the rotor shaft and the radial force applied to the stator, both generated by the electromagnetic fields in the electric motor. For example, when a very high-frequency voltage is injected, this results in a varying radial force on the stator, causing it to vibrate and thus creating a pressure variation in the surrounding air. This ultimately results in an acoustic noise that can propagate through various transmission paths within the SbW system and the vehicle.This radial vibration can also result in tactile feedback due to the physical movement of the stator (in the radial direction). Finally, the torsional torque on the rotor shaft primarily generates tactile feedback, but depending on the frequency of the change, it can sometimes also lead to acoustic noise.

[0071] The technical solutions described here therefore enable the use of the RWA 520 to provide a warning to the driver, even though the RWA 520 is not directly connected to the driver, for example by vibration of the vehicle 650 directly (because the RWA 520 is directly connected to the vehicle 650).

[0072] As in Fig. As shown in Figure 6, the first and second injection signals for the HWA 510 and the RWA 520, respectively, are generated based on a common fault monitoring system 240, which provides the D and P markers for the driver warning system 250. Alternatively, the SbW system 40 uses separate fault monitoring systems for the HWA 510 and the RWA 520.

[0073] Fig. Figure 7 shows a block diagram with separate fault monitoring systems for the HWA 510 and the RWA 520 according to one or more embodiments. An HWA fault monitoring system 710 monitors the operation of the HWA 510 and detects the occurrence of a fault during operation. The HWA fault monitoring system 710 generates a corresponding set of output markers D. H and P H The driver warning system 250 includes a corresponding HWA driver warning system 715, which uses the marker D H and P Hreceives data to determine the driver feedback to be generated based on the marker values.

[0074] A separate smoke and heat exhaust ventilation (SHEV) fault monitoring system 720 essentially monitors the operation of the SHEV 520 simultaneously with the main ventilation (HWA) fault monitoring system 710 and detects the occurrence of a fault during operation. The SHEV fault monitoring system 720 generates a corresponding set of output markers D. R and P R The driver warning system 250 includes a corresponding RWA driver warning system 725, which displays the marker D R and P R receives data to determine the driver feedback to be generated based on the marker values.

[0075] The Driver Warning System 250 also includes a Driver Warning Coordination Module (DWCM) 750, which receives as input the output generated by the HWA Driver Warning System 715 and the RWA Driver Warning System 725. Based on these inputs, the DWCM 750 generates one or more injection signals. For example, the DWCM 750 determines whether driver feedback should be generated only via the HWA 510, only via the RWA 520, or using a combination of both. Furthermore, the DWCM 750 determines which injection signals should be generated for both the HWA 510 and the RWA 520. For example, as previously described, the injection signals can be one of, or a combination of, voltage signals, current signals, and torque signals.

[0076] In one or more examples, tactile warning feedback may be generated solely by the HWA 510, while the audible warning may be generated jointly by both the HWA 510 and the RWA 520. Such a division of warning generation is coordinated by the DWCM 750. The DWCM 750 evaluates and determines how the two actuators share and apply the warning signals (e.g., by monitoring the operating states of both modules). It should be noted that the DWCM 750 can reside either within the HWA 510 subsystem or the RWA 520 subsystem, or it can be a separate system.

[0077] Fig. Figure 8 presents a flowchart of a method for generating driver feedback / warning in a SbW system according to one or more embodiments. In Figure 805, the method includes detecting a fault in the HWA 510 by the steering wheel fault monitoring system 710. In Figure 807, the method further includes detecting a fault in the RWA 520 by the steering wheel fault monitoring system 710. The HWA fault detection and the RWA fault detection can occur simultaneously in one or more examples. The fault detection is performed as described here (see Figure 805 as an example). Fig. 4) In one or more examples, fault detection leads to the setting of one or more fault indicator markers, such as diagnostic markers and prognostic markers.

[0078] The procedure further includes determining, at 810, one or more types of driver feedback to be generated in response to the detected fault(s) in the HWA 510 and / or the RWA 520. The feedback type may include, for example, tactile feedback and / or acoustic feedback, and the like. The type of feedback to be provided may be determined using one or more of the techniques described herein.

[0079] If feedback is to be provided via the HWA 510, the procedure at 820 and 822 includes generating an initial injection signal. For example, the driver warning system 250 generates the initial injection signal to modify an amplitude, frequency, or any other attribute of an input command for a motor circuit in the HWA 510, as described here. The initial injection signal can be a torque signal, a current signal, a voltage signal, or a combination thereof. Depending on the type of initial injection signal, at 824 the initial injection signal is delivered to the motor circuit of the HWA 510 to modify the corresponding input command. Modifying the input command(s) causes the motor 614 of the HWA 510 to generate tactile / audible feedback for the driver.

[0080] Furthermore, if feedback is to be provided via the RWA 520, the procedure at 830 and 832 includes generating a second injection signal. The driver warning system 250 generates the second injection signal to modify an amplitude, frequency, or any other attribute of an input command for a motor circuit, for example, within the RWA 520, as described here. The second injection signal can be a torque signal, a current signal, a voltage signal, or a combination thereof. At 834, depending on the type of the second injection signal, the second injection signal is supplied to the motor circuit of the RWA 520 to modify the corresponding input command. Modifying the input command(s) causes the motor 624 of the RWA 520 to generate tactile / audible feedback for the driver.

[0081] In one or more examples, supplying the first and second injection signals at 850 involves coordinating the two injection signals generated by the steering wheel actuator driver warning system 715 and the road wheel actuator driver warning system 725, respectively, to determine driver feedback. For example, the coordination may involve deciding between the injection signals if they are of the same type and choosing the higher value of the two. For instance, consider that the steering wheel actuator driver warning system 715 generates a first warning injection signal and the road wheel actuator driver warning system 725 generates a second warning injection signal, both containing a voltage modification command. The two modification commands are assumed to have values ​​of V1 and V2, respectively, and that both are to be injected into the HWA 510 (or the RWA 520).In one or more examples, the coordination may involve selecting the injection signal with the larger value of V1 and V2 for injection into the HWA 510 (or the RWA 520). The coordination may also involve selecting the injection signal in any other way, for example, choosing the smaller value, calculating an average, a weighted average of the two signals, or any other technique, or a combination thereof.

[0082] The technical solutions described here therefore enable several mechanisms for alerting the driver using the engine control loop in the HWA and RWA subsystems of an SbW system in the event of fault conditions determined by the diagnostic and prognostic monitoring module.

[0083] In accordance with one or more embodiments, a steering system includes a first motor control system that sends a first command to a first motor in a steering wheel actuator. The steering system further includes a second motor control system that sends a second command to a second motor in a road wheel actuator. The steering system further includes a fault monitoring system that sets a fault indicator by monitoring one or more components of the steering system. The steering system further includes a driver warning system that generates a warning injection signal in response to the fault indicator being set. The steering wheel actuator generates initial driver feedback by modifying the first command using the warning injection signal and sending the modified first command to the first motor.Furthermore, the road wheel actuator generates a second driver feedback by modifying the second command using the warning injection signal and sending the modified second command to the second motor.

[0084] In one or more examples, the second command being modified is a voltage command. In one or more examples, the first command being modified is a torque command. The steering system where the second command being modified is a current command. The steering system where the second command being modified is the result of a sensor signal simulation by the fault monitoring system.

[0085] In one or more examples, the warning injection signal comprises a first injection signal and a second injection signal, and the driver warning system includes a steering wheel driver warning system that generates the first injection signal based on a fault detected in the steering wheel actuator, and a road cyclist warning system that generates the second injection signal based on a fault detected in the road wheel actuator. In one or more examples, the driver warning system further includes a driver warning coordination module that evaluates the first injection signal and the second injection signal to generate the warning injection signal.

[0086] In one or more examples, both the steering wheel driver warning system and the road cyclist warning system include a fault duration module that monitors the duration the fault indicator is set, determining the warning injection signal based on this duration. In one or more examples, both the steering wheel driver warning system and the road cyclist warning system include a fault monitoring and evaluation module that determines the type of driver feedback based on the fault indicator flag. In one or more examples, both the steering wheel driver warning system and the road cyclist warning system include an injection signal calculation module that calculates the warning injection signal based on the type of driver feedback to be provided, the calculation involving determining the frequency, phase, and amplitude of the warning injection signal.

[0087] In one or more examples, the fault monitoring system includes a steering wheel driver warning system that detects a fault in the operation of the steering wheel actuator; and a road wheel fault monitoring system that detects a fault in the operation of the steering wheel actuator. The warning injection signal contains a variety of injection signals: a first injection signal for the first command to the steering wheel actuator and a second injection signal for the second command to the road wheel actuator.

[0088] In accordance with one or more embodiments, a method for providing driver warning feedback using a steer-by-wire system comprises receiving a warning flag indicating a fault in one or more components of the steering system. The method further comprises generating a warning injection signal based on the fact that the fault warning flag is set. The method further comprises generating initial driver feedback by a steering wheel actuator by modifying an initial input command with the warning injection signal and sending the modified initial input command to a first motor of the steering wheel actuator.The procedure further includes generating a second driver feedback signal by a road wheel actuator by modifying a second input command with the warning injection signal, and sending the modified second input command to a second motor of the road wheel actuator.

[0089] In accordance with one or more embodiments, a driver warning feedback system includes a steering wheel fault monitoring system configured to monitor a first fault indicator flag that indicates a fault in the operation of one or more components of a steering wheel actuator. The driver warning feedback system further includes a steering wheel actuator driver warning system configured to generate first driver feedback about the steering wheel actuator based on the first fault indicator flag being set. The driver warning feedback system further includes a road wheel fault monitoring system configured to monitor a second fault indicator flag that indicates a fault in the operation of one or more components of a road wheel actuator.The driver warning feedback system further includes a road wheel actuator driver warning system configured to generate a second driver feedback signal via the road wheel actuator based on the second fault indicator being set. The driver warning feedback system further includes a driver warning coordination module configured to calculate a warning injection signal based on the first and second driver feedback signals and to send the warning injection signal to modify a command sent to a motor to generate a driver warning.

[0090] It should be noted that while the technical solutions described herein are designed to generate feedback to a driver using a warning system within the context of a vehicle, such as a steering system, the technical solutions described herein can also be used as a warning system that generates an audible sound using one or more motors. The warning system includes the actuators and fault monitoring system as described herein, the actuators comprising respective sets of components and motors used to generate an audible sound as a warning notification. Consequently, the warning system generates audible sounds without the use of a loudspeaker or any other such typical device for generating an acoustic warning / feedback.

[0091] The technical solutions presented here can be a system, a process, and / or a computer program product at any possible level of technical integration. The computer program product can include one or more computer-readable storage media containing computer-readable program instructions to cause a processor to execute aspects of the technical solutions presented here.

[0092] Aspects of the present technical solutions are described here with reference to flowchart illustrations and / or block diagrams of processes, devices (systems), and computer program products in accordance with embodiments of the technical solutions. It is understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, may be implemented by computer-readable program instructions.

[0093] The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, procedures, and computer program products in accordance with various embodiments of the presented technical solutions. In this respect, each block in the flowchart or block diagrams can represent a module, segment, or part of instructions, comprising one or more executable instructions for implementing the described logical functions. In some alternative implementations, the functions described in the blocks may occur in a different order than shown in the figures. For example, two consecutively shown blocks may actually be executed essentially simultaneously, or the blocks may sometimes be executed in reverse order, depending on the functionality involved.It is also mentioned that each block of the block diagrams and / or flowchart illustration and combinations of blocks in the block diagrams and / or flowchart illustration can be implemented by specialized hardware-based systems that perform the described functions or actions, or execute combinations of special hardware and computer instructions.

[0094] Furthermore, it should be noted that all modules, units, components, servers, computers, terminals, or devices described herein as examples, which execute instructions, contain computer-readable media or can otherwise access them, such as mass storage media, computer mass storage media, or data mass storage devices (removable and / or non-removable) such as magnetic disks, optical disks, or tapes. Computer storage media can include volatile and non-volatile, removable and non-removable media implemented by any method or technology for storing information, such as computer-readable instructions, data structures, program modules, or other data. These computer storage media can be part of the device, accessible to it, or connectable to it.All applications or modules described herein can be implemented using computer-readable / executable instructions stored on these computer-readable media or otherwise maintained.

Claims

[1] Steering system (40) comprising: a first motor control system (612) configured to send a first command to a first motor (614) in a steering wheel actuator (510); a second motor control system (622) designed to send a second command to a second motor (624) in a road wheel actuator (520); a controller (16) designed to to set a fault indicator by monitoring one or more components of the steering system (40); and to generate a warning injection signal in response to the fact that the fault indicator flag is set; wherein the steering wheel actuator (510) is configured to generate initial driver feedback by modifying the initial command using the warning injection signal and sending the modified initial command to the initial motor (614); and wherein the road wheel actuator (520) is designed to generate a second driver feedback by modifying the second command using the warning injection signal and sending the modified second command to the second motor (624), wherein the warning injection signal comprises a first injection signal and a second injection signal and wherein the controller (16) is further configured to: to generate the first injection signal based on a fault detected in the steering wheel actuator (510); to generate the second injection signal based on a fault detected in the road wheel actuator (520); and to evaluate the first injection signal and the second injection signal in order to generate the warning injection signal. [2] Steering system (40) according to claim 1, wherein the modified second command is a voltage command. [3] Steering system (40) according to claim 2, wherein the modified first command is a torque command. [4] Steering system (40) according to claim 2, wherein the modified first command is a current command. [5] Steering system (40) according to claim 1, wherein the second command is modified by the controller (16) in response to a sensor signal simulation. [6] Steering system (40) according to claim 1, wherein the controller (16) is further configured to monitor the duration of the setting of the fault indication, the warning injection signal being determined on the basis of the duration. [7] Steering system (40) according to claim 6, wherein the controller (16) is further configured to determine a type of driver feedback based on the fault indicator, wherein the type of driver feedback includes tactile feedback and / or acoustic feedback. [8] Steering system (40) according to claim 7, wherein the controller (16) is further configured to calculate the warning injection signal based on the type of driver feedback to be provided, the calculation comprising determining at least a frequency and an amplitude of the warning injection signal. [9] Steering system (40) according to claim 1, wherein the controller (16) is further configured to detect a fault in the operation of the steering wheel actuator (510) and to detect a fault in the operation of the road wheel actuator (520). [10] Method for providing driver warning feedback using a steer-by-wire system, the method comprising: Receiving (805, 807) a warning flag indicating a fault in one or more components of the steering system (40); Generating (822, 832) a warning injection signal based on the fact that the fault indicator flag is set; Generating (850) a first driver feedback by a steering wheel actuator (510) by modifying a first input command with the warning injection signal, and sending the modified first input command to a first motor (614) of the steering wheel actuator (510); Generating (834) a second driver feedback by a road wheel actuator (510) by modifying a second input command with the warning injection signal, and sending the modified second input command to a second motor (624) of the road wheel actuator, wherein the warning injection signal comprises a first injection signal and a second injection signal, the first injection signal being generated by a steering wheel driver warning system (715) based on a fault detected in the steering wheel actuator (510), and the second injection signal being generated by a road wheel driver warning system (725) based on a fault detected in the road wheel actuator (520); and Evaluating the first injection signal and the second injection signal to generate the warning injection signal. [11] Method according to claim 10, wherein the warning injection signal is determined on the basis of a duration for which the fault indicator is set.

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