Method for developing a control law for a steering assistance system of a motor vehicle

Abstract

A method for developing a control law for an assistance system of an automatic driving assistance (ADAS) system in a motor vehicle, capable of operating in an automated driving mode. This method, implemented by at least one control unit of the assistance system, consists of implementing a specific assistance mode (ADAS mode) acting on lateral control functions of the vehicle within its lane, complementary to the Normal and Sport modes already present in the vehicle. This ADAS mode is dedicated to the automated driving mode and controlled by a servo controller whose parameters allow it to take into account, within a predetermined range of torque values, at least one torque applied by the driver to the steering wheel, thus providing occasional support to the assistance system in real-life situations requiring driver intervention on the steering wheel, without interrupting the automated driving mode. (Figure 2)

Description

Title of the invention: Method for developing a control law for a steering assistance system of a motor vehicle

[0001] The present invention relates generally to motor vehicles equipped with a steering wheel equipped with an electric assistance system, also designated by the acronym "EDA" for Electric Power Steering, and relates more particularly to a method of developing a control law for a steering wheel assistance system of a motor vehicle, in a context of automated driving of the vehicle in which the driver can interact with the steering wheel while the car is driving in automated driving mode.

[0002] The method according to the invention implements a control-law type software strategy for the internal development of the AED assistance system, based on functions of an AD AS (Anglo-Saxon acronym for "Advanced Driver Assistance Systems") system of the vehicle, linked to the lateral control of the vehicle in its lane of travel and uncorrelated with manual driving.

[0003] This control law allows for simultaneous, separate development specific to the needs of collaborative automated driving, without impacting other areas of development of an AED.

[0004] In general, an autonomous vehicle, or a vehicle with an autonomous or automated driving mode, will be designated as a vehicle which has AD AS functions enabling the automation of certain driving functions usually assigned to the driver.

[0005] The autonomy level of a vehicle considered in this description typically covers level 2 (the five autonomy levels 0 to 5 are defined by the J3016 standard of the “SAE International”).

[0006] Today, the control laws of an assistance system of an AED in automated driving mode are determined on an already existing basis of manual driving.

[0007] Therefore, the flying and bodily sensation of a driver or passenger seated in a vehicle that is driving in automated driving mode is only a behavior resulting from the actuators and regulators that ensure automated driving, in particular the calculated maintenance of the vehicle in its lane of travel, using the levels of assistance made available by the AED.

[0008] It should be noted that the main AD AS functions, implemented to keep the vehicle in its lane of travel, from the AED, are:

[0009] - LKA, an Anglo-Saxon acronym for "Lane Keeping Assist": assistance in maintaining lane in French, and which makes the vehicle bounce back on the lines delimiting the traffic lane, if the vehicle tries to cross them inadvertently;

[0010] - LPA, an Anglo-Saxon acronym for "Lane Position Assist: maintaining the vehicle in fixed position determined in its lane of travel in automated driving mode under active driver supervision;

[0011] - LxA: the LPA and LKA functions are activated simultaneously;

[0012] - Cohabitation: mode activated when the vehicle is simultaneously controlled by the LxA via a rack position request and by the driver via the steering wheel, without deactivating LxA.

[0013] - Positioning: In LPA, the default position of the vehicle is in the center of the lane. A Following an activated LPA driving instruction, the driver can define another position of the vehicle in its lane (close to the right, close to the left etc...), a position which will become the new positioning reference for the next few kilometers.

[0014] It is currently very difficult to develop a control law controlling an assistance system of an AED, adapted for a vehicle driving in an automated driving mode and allowing, depending on the situation, a softer or more incisive, progressive or robotic behavior / feeling.

[0015] This development, necessary to optimize the steering comfort of the AED, and therefore the driving comfort of the vehicle, is very present and rooted in the world of chassis development in non-autonomous driving, but it is very little developed or even non-existent in automated driving.

[0016] In terms of manual driving, this development allows for differentiation between brands on the same platform. The AD AS system then takes into account the driving experience thus developed for each brand.

[0017] Thus, the driving experience in automated driving mode is "modeled" on that developed in manual driving mode, essentially replicating the assistance levels of manual driving. This can pose problems in the event of separate developments in the two driving modes, manual and automated, and ultimately disrupt vehicle type approvals.

[0018] Furthermore, development times generally take into account this "follower" type operation for the development of AD AS in connection with the DAE.

[0019] Thus, the disadvantages associated with this type of development are numerous and are listed below in a non-exhaustive manner:

[0020] - Too long a development time;

[0021] - Does not allow power steering development teams to operate while driving automated / manual operation to work in parallel with each other;

[0022] - It is impossible to fine-tune the cohabitation driving in the phases automated driving (level of effort, responsiveness of the system, damping, non-linearity, impact of speed);

[0023] - No differentiation in AD AS service possible from a Brand point of view;

[0024] - Excessive intermingling of automated driving with manual driving which is constantly evolving throughout development, while the milestones and delivery dates are the same for both driving modes;

[0025] - Stress caused to the teams;

[0026] - Final vehicle behavior sometimes deviates from the manufacturer's expectations automobile;

[0027] - Few adjustment levers for the AED to correct or adapt a non- suitable for automated driving induced by an evolution of the chassis (tire, wheel, shock absorber, ...) and for a search for cost reduction;

[0028] - Automated driving behavior differs between Normal mode and mode Sport.

[0029] The objective of the present invention is to provide a solution to these various drawbacks by proposing a development logic allowing modification of numerous parameters, internal to the DAE assistance system, acting on the steering approval in the automated driving phase.

[0030] The invention also makes it possible to manage the transitional phases of entry and exit from the automated driving mode, and to differentiate between automated driving, steering wheel held or released, all without impacting manual driving and ensuring good operational safety.

[0031] To this end, the invention has as its first object a method for developing a control law for a steering wheel assistance system of a motor vehicle capable of driving in an automated driving mode;said process, implemented by the assistance system, consists of implementing a specific assistance mode, designated as ADAS mode, acting on lateral control functions of the vehicle in its lane of travel, complementary to the Normal and Sport modes already present in the vehicle, said ADAS mode being dedicated to the automated driving mode of the vehicle and controlled by a servo regulator of the assistance system whose parameter setting allows taking into account, within a range of determined torque values, at least one torque applied by the driver on the steering wheel allowing to temporarily support the assistance system in life situations requiring intervention by the driver on the steering wheel, without interrupting the automated driving mode.

[0032] According to one feature, the method consists of considering the torque applied by the driver to the steering wheel, in ADAS mode, as a parameter input of the assistance system, and to manage the release of the steering wheel by the driver and the resumption of control by the assistance system, so as to control the steering wheel to bring the vehicle back to the center of its lane of traffic taking into account the speed of the vehicle and the natural movements of the vehicle, without exiting the automated driving mode.

[0033] According to another feature, the method consists of managing a sudden steering maneuver during an avoidance maneuver, by applying a determined level of effort greater than that required in Normal or Sport mode in order to increase safety.

[0034] According to another feature, the method uses a state machine for switching from one mode to another; said state machine being implemented by the servo controller of the assistance system.

[0035] According to another feature, the method consists of setting up a transition of modes, between Normal or Sport modes to AD AS mode and vice versa, with a determined weight assigned to each of the modes and, adjusting the transition time from one mode to the other, between an instantaneous transition time and a determined maximum transition time.

[0036] According to another feature, the method consists of controlling the advance or delay of the assistance system to maintain the vehicle's trajectory in phase with an optimal trajectory determined only in the automated driving mode.

[0037] According to another characteristic, the servo controller is a proportional gain PID controller.

[0038] According to another feature, the lateral control implements one of the following functions of a driving assistance system, called AD AS system: a lane keeping assistance function, called LKA, and a lane positioning assistance function, called LPA or a combination of the two functions LKA and LPA, called LxA.

[0039] The present invention has as its second object a motor vehicle comprising an automated driving mode and an electrically assisted steering wheel; said vehicle comprising an assistance system developed by the process as described above.

[0040] The main advantages of the present invention are:

[0041] - to enable optimization of development times in power steering electric (DAE);

[0042] - to allow parallel technical work between several teams, sometimes on different geographical sites;

[0043] - to allow the development of a "Management Approval" in driving automated;

[0044] - to technically separate the AD AS functionalities (LKA, LPA), and the mode of manual transmission.

[0045] Other advantages and features of the present invention will become clearer from the following description, given solely by way of non-limiting example and with reference to the drawings in which:

[0046] [Fig.1] illustrates timing diagrams of switching driving modes in a development process according to the invention;

[0047] [Fig.2] illustrates an example of a state machine for switching from one driving mode to another, in the form of chronograms, implemented by the method according to the invention;

[0048] [Fig.3] illustrates a first life situation relating to the avoidance of a fixed obstacle, without cohabitation;

[0049] [Fig.4] illustrates the first living situation with cohabitation made possible by an AD AS mode implemented by the process according to the invention;

[0050] [Fig.5] illustrates a second living situation relating to a motorway exit, with and without cohabitation;

[0051] [Fig.6] illustrates the main components of a vehicle involved in the automated driving mode and ultimately acting on the AED whose assistance system is regulated by the method according to the invention;

[0052] [Fig.7] illustrates the effects of adjusting the phasing of the DAE with the trajectory of the vehicle by the method according to the invention;

[0053] [Fig.8] illustrates the effects of damping on a steering wheel turn, provided by the AD AS mode implemented by the method according to the invention; and

[0054] [Fig.9] illustrates a third life situation taking into account the effects of damping on a steering wheel turn, brought about by the AD AS mode implemented by the process according to the invention.

[0055] The present invention introduces an "AD AS" mode into the power steering assistance system, in addition to the existing "Sport" and "Normal" modes already present in a vehicle. This AD AS mode is exclusively reserved for automated driving mode. It can only be activated in automated driving mode.

[0056] When the vehicle is operating in automated driving mode, access to the parameter setting (assistance level) of the AED assistance system is via the AD AS mode. The AD AS mode has the same number of parameters as the usual assistance modes of an AED, but linked to the automated driving. All modes can be set independently of each other.

[0057] The present invention provides a solution compatible with the ADAS functions already present in vehicles, related to the lateral control of the vehicle in its lane, also referred to as "lateral ADAS". It complements the existing system. assistance from the AED already developed for manual driving, when the AD AS functions are activated, unlike other solutions in which automated driving completely replaces manual driving.

[0058] The solution according to the invention allows the driver to better understand the assistance of the AED in automated driving mode, by offering a type of steering closer to that already present in manual driving, which facilitates taking back control of the vehicle before and after the driving phases in automated driving mode.

[0059] The "lateral AD AS" devices considered in the present invention allow:

[0060] - A 100% autonomous level 2 driving system;

[0061] - A "positioning" in the lane;

[0062] - coexistence with the automated driving system;

[0063] - overtaking autonomously with driver supervision;

[0064] - To prevent the unintentional crossing of a white line;

[0065] - Resumption of control during lane change if a vehicle is in a blind spot.

[0066] CALIBRATION DIVERSITY: AUTOMATED DRIVING STEERING APPROVAL

[0067] The invention exhibits a complete decorrelation between the calibration for fine-tuning the AED assistance system in manual driving mode and that for fine-tuning in automated driving mode. Both settings offer exactly the same functionalities for fine-tuning an AED.

[0068] All parameters characterizing steering comfort, resulting from the implementation of the control law driving the steering wheel torque control system (DAE), are available in AD AS mode:

[0069] - Proportional and derivative gains (as a function of vehicle speed, acceleration) lateral, torque at the steering wheel...) of the PID (Proportional, Integral, Derivative) regulator: functions allowing to improve the performance of the servo control;

[0070] - Controlled damping function (depending on vehicle speed, acceleration) lateral, torque at the steering wheel, steering wheel rotation speed...);

[0071] - Active recall function (depending on vehicle speed, lateral acceleration, torque at the steering wheel, steering wheel rotation speed, steering wheel angle...);

[0072] - Hysteresis control;

[0073] - Level and gradient of steering effort; (as a function of lateral acceleration, of the vehicle speed);

[0074] - Identification of chassis characteristics; (phasing, delay);

[0075] - Friction compensation (as a function of lateral acceleration, speed vehicle, steering wheel angle);

[0076] - etc.

[0077] Each of these parameters responds to specific and different constraints depending on whether one is in manual or automated driving mode.

[0078] The invention, by its decorrelation with manual and automated driving modes, makes it possible to offer for coexistence in autonomous mode a development more in line with the needs of autonomous driving and the style / character of the Brands.

[0079] Historically, automated driving has had the drawback of rejecting driver input, treating it as a distraction. As long as the vehicle is driving itself and the driver keeps their hands on the steering wheel, the driver will feel the automated driving system (ADS) "working." If the ADS is too "expressive," the driver will not feel confident.

[0080] Access to these parameters, considered as input parameters of the assistance system, makes it possible to make automated driving smoother, to give it a more human character, in short, to smooth out the regulations brought about by the functions of the AD AS system.

[0081] The vehicle is therefore more pleasant and easier to drive in automated driving, and gives the driver more confidence.

[0082] SWITCHING FROM ONE MODE TO ANOTHER

[0083] After introducing two separate focus calibrations for the two driving modes: manual and automated, it is necessary to be able to manage the switch from one to the other.

[0084] To this end, the present invention uses a transition parameter which allows the switch from Normal (or Sport) mode in manual driving mode, to AD AS mode in automated driving mode.

[0085] This transition parameter acts as a determined weighting parameter (weight) applied to the parameters characterizing the driving “comforts” of each of the driving modes: manual or automated.

[0086] Thus, as schematically illustrated by the three mode chronograms of [Fig.1], this weight, expressed as a percentage, goes from 100% to 0% for the mode being left: manual driving mode to autonomous driving mode (top chronogram) or autonomous driving mode to manual driving mode (middle chronogram) and from 0% to 100% for the AD AS mode when the AD AS mode is activated, which is only activated in the automated driving mode, whether in Normal mode or in Sport mode.

[0087] In this last situation (bottom chronogram), it is necessary that at the halfway point of activation, the weights are, for example, at 50% in Normal mode (or Sport mode) and at 50% in AD AS mode.

[0088] The transition time At from one mode to another (AD mode AS Normal (or Sport) mode) is adjustable from 0 ms to X ms (0 ms corresponding to an instantaneous transition from one mode to the other). A longer At transition time allows very different Normal (or Sport) and AD AS modes to coexist, whereas an instantaneous transition is felt by the driver as a variation in effort level or the appearance of a "notch".

[0089] The automated driving mode considered in the present invention takes into account the driver's manual interventions on the steering wheel, designated as "driver inputs." The assistance system supplements the driver inputs (interpreted as disruptive elements) in the automated driving mode assistance system.

[0090] The purpose of the AD AS mode according to the invention is to transform "a user who disrupts the system" into a user experience that allows the driver to support the automated driving mode.

[0091] Fig. 2 illustrates a mode-switching state machine, in the form of four time-corresponding chronograms, in an example of a scenario for using a control law implemented by the method according to the invention for the development of the DAE assistance system.

[0092] We can distinguish, from top to bottom of [Fig.2]:

[0093] - a first timing diagram relating to the types of driving: autonomous or manual, selected by the driver;

[0094] - a second timing diagram relating to driving modes: Normal mode or mode Sport, selected by the driver;

[0095] - a third chronogram relating to the states of the DAE, distinguishing a first a state corresponding to the assistance mode implemented by the AD AS mode, a second state corresponding to a first specific assistance mode called "mode 1", and a third state corresponding to a second specific assistance mode called "mode 2"; and

[0096] - a fourth chronogram relating to the regulation provided by the function in distinguishing a first "available" state between second and third states corresponding respectively to active and deactivated states of the LKA function.

[0097] The phases of the LKA function (fourth chronogram) are based on the Normal mode or the Sport mode depending on the mode selected by the driver.

[0098] The AD AS mode (third chronogram) does not interfere with the LKA function (fourth chronogram).

[0099] When LKA regulation is requested, if the vehicle is about to cross a lane, the regulation must use the default mode in which the vehicle is located: Normal or Sport. Thus, LKA regulation in Normal mode will rely on the Normal mode.

[0100] In another scenario in which it is decided to activate LKA regulation during an automated driving mode (Autonomous mode), LKA regulation would rely Then, in ADAS mode. If the regulation intervenes in Sport mode, the LKA regulation would rely on Sport mode. This is to avoid unnecessarily disrupting the AED assistance system.

[0101] Since the LKA regulation's action times are generally very short and fragmented (the "Active" state of the fourth timing diagram), introducing a mode change (Normal or Sport) in this situation would be detrimental as it could lead to variations in steering effort, torque dips, or even "sweeping." Switching between modes too briefly can also lead to instabilities if the modes are too different (typical) from each other.

[0102] PID MODE ADAS

[0103] The power steering system comprises, in a known manner, an electric assist motor coupled to the steering column, which is itself coupled to the steering wheel. The steering column is further coupled to the vehicle's steering wheels via a rack and pinion system.

[0104] The electric motor is controlled by a PID controller, already introduced above, whose action can be integral, derivative, or proportional to the measured deviation between the controlled variable and the setpoint. Such a PID controller is introduced into a feedback loop (control loop controller). It is parameterized by means of gains or coefficients to weight the corrective actions, which are respectively proportional to said deviation, to its integral, or to its derivative. The action described as "proportional" contributes directly to the responsiveness and stability of the feedback system. This is the action used in the present invention.

[0105] In manual driving mode, without ADAS system activation, the PID servo regulator development uses the torque entered by the driver at the steering wheel as a setpoint which is then used by the AED assistance system for tracking in phase with the vehicle's demand and reaction.

[0106] In automated driving mode, the instruction is different:

[0107] - If the steering wheel is completely released or is only lightly held: this is the position of the rack, calculated to allow the correct trajectory which serves as the instruction;

[0108] - If the steering wheel is firmly held or manipulated by the driver (this is referred to as situation by the term "cohabitation"): it is then the torque entered by the driver on the steering wheel with constant feedback with the calculated rack position allowing the correct trajectory, which serves as the instruction.

[0109] The invention uses a specific PID servo controller that takes into account the torque applied by the driver to the steering wheel as a setpoint in the ADAS mode, introduced above, to allow for the development of a desired and not resultant coexistence of the actions of the PID controller or the setting of the PID controller of the manual driving. The setting of this specific PID controller meets a very different need than the manual driving modes, Normal or Sport.

[0110] Thus, while in manual driving mode the steering input tends towards a "quick" proportional gain for a responsive car, the proportional gain in automated driving mode will be "smoother," slower. Since the levels of effort are different, a "quick" gain in automated driving mode will more quickly tend to bring the vehicle out of automated driving mode.

[0111] It is then necessary to smooth the actions of the driver on the steering wheel, and to give the AED assistance system enough priority so that it can continue to keep the vehicle in its lane despite the coexistence.

[0112] The adjustment, fine-tuning action on this specific PID regulator, without going to the extreme case of a car that cannot be positioned correctly in its lane and that cuts off, deactivates, the AD AS system as soon as the driver interacts with the steering wheel, also allows the "character" of the vehicle to be refined according to its positioning, typing, in the range.

[0113] Thus, a more prestigious and grand touring car can be very "calm" and positioned in its lane with "serene" steering movements which have the effect of limiting yaw / roll for the well-being of the passengers.

[0114] On the contrary, a more "lively" city car and in urban driving, can have more responsiveness and position itself more quickly.

[0115] The same steering wheel action on two differently designed vehicles will therefore not have the same impact. It is up to the brands to define the behavior most in line with the image the manufacturer wishes to convey.

[0116] SUPPORTING AUTOMATED DRIVING

[0117] In order for AD AS functions (level 2 and above) to remain regulatory and comfortable, car manufacturers interpret and define a set of functional limits for the computers of the AD AS system.

[0118] These functional limits impact lateral acceleration, flywheel rotation speed, and flywheel torque level in cohabitation.

[0119] The values ​​of these limits are standardized and identical for all vehicle silhouettes. These limits guarantee the driver's control of the vehicle at all times.

[0120] However, these limitations are double-edged because in certain life situations they can interfere with target guidance to avoid an obstacle.

[0121] For safety reasons, it is unthinkable to raise these thresholds for a real-life situation, at the risk of generating numerous faults under other conditions. An "exuberant" ADAS system does not inspire confidence in the driver, who will not use it.

[0122] The present invention makes it possible to evolve cleverly within these safety limits of the AD AS functions by allowing the driver to occasionally come to support the actions of the assistance system.

[0123] In these so-called tricky driving situations (sharp turns, areas with disappearing lines, chicanes, etc.), the assistance system alone is often unable to navigate the area while remaining within the imposed limits. However, in most cases, a little help (in steering torque or speed) from the driver allows the assistance system to succeed.

[0124] The idea is to remain at all times (assistance system alone or assistance system + cohabitation) within a "functional corridor". Exiting this "functional corridor" results in a clean shutdown of the AD / AS system.

[0125] Figures 3 and 4 respectively illustrate a first life situation in which a VHL vehicle travelling on the right in a VDC two-way traffic lane, at a speed limited to 50km / h, encounters a fixed obstacle zone ZOF of the chicane type, or central reservation, requiring a bypass on the right of the obstacle ZOF, with a brief change of direction first to the right followed almost immediately, due to the speed of the VHL vehicle and the short length of the obstacle ZOF, by a brief change of direction to the left to bring the VHL vehicle back to the centre of its traffic lane WH (steering wheel in the centre).

[0126] Figure 3 illustrates the TRJ trajectory of the VHL vehicle in the case where there is no "cohabitation" introduced by the AD AS mode and without regulation by the PID controller specific to the AD AS mode, introduced above. In such a situation, the VHL vehicle, driving in automated driving mode with the imposed assistance limits, is unable to cross the ZOF zone while remaining within the imposed limits.

[0127] This results in the VHL vehicle exiting autonomous driving mode and the driver taking back RPM control in manual driving mode, a little at the last moment with a somewhat turbulent TRJ trajectory correction to bring the VHL vehicle back to the center of its WH traffic lane (steering wheel in the center).

[0128] The straight segment in dashed line ending with a star indicates the exit zone of the TRJ trajectory of the VHL vehicle in case of failure of the autonomous driving system, without reaction from the driver.

[0129] Figure 4 illustrates the same living situation but in which the VHL vehicle has AD AS mode assistance with cohabitation.

[0130] Thus, when the VHL vehicle, in autonomous driving mode, reaches the ZOF zone, the driver intervenes on the VHL vehicle's TRJ trajectory, in cohabitation mode, throughout the entire bypass maneuver: a small turn of the steering wheel to the right (CVD) followed by a small turn of the steering wheel to the left (CVG). The VHL vehicle, after integrating the driver's intervention, resumes its TRJ trajectory, still in mode autonomous driving towards the center of the WH traffic lane without exiting autonomous driving mode. The bypass maneuver is thus carried out smoothly and without changing driving modes.

[0131] Fig. 5 illustrates a second life situation in which the VHL vehicle takes a motorway exit, at 50 km / h which defines a sharp left turn.

[0132] At this speed of 50 km / h, the assistance system applies a maximum imposed turning radius CRB (dependent on lateral acceleration) corresponding to the radius of a virtual circle CVR represented by dotted lines.

[0133] As illustrated, this maximum functional setpoint imposed by CRB does not allow the end of the VSA turn to be taken. The assistance system is not permitted to increase its setpoint by increasing the steering angle (functional limit).

[0134] However, this second life situation is a nominal situation, far from the safety limits in maximum acceleration or maximum steering torque, which would lead to a clean cut-off of the AD AS system and therefore of the automated driving mode.

[0135] Without the "cohabitation" enabled by the AD AS mode and its specific PID controller as introduced above, the CSP takeover would have disengaged the automated driving mode (the AD AS system), or, without takeover, the AD AS system would have guided the VHL vehicle towards the outside of the VSA curve, the critical zone ZCR, symbolized in the figure by a star on the CVR circle. The driver would then have been forced to manually bring the VHL vehicle back into its lane and then reactivate the AD AS system.

[0136] Thanks to the cohabitation in AD AS mode, in the critical zone ZCR, the driver can in this situation apply the additional torque CSP to the steering wheel just necessary to pass the VSA turn, without deactivation of the AD AS system and bring the vehicle VHL back to the center of its lane WH in the takeover zone ZRM symbolized on the figure by a thicker line segment of the curve.

[0137] The AD AS system resuming vehicle guidance on the "normal" trajectory TRJ always in automated driving mode.

[0138] As with any mechatronic system, the development of automated driving involves managing the delays of the various components involved in regulation (controllers, actuators, etc.) that enable automated driving. Throughout the software development process of an automated driving system, these delays evolve, shortening or lengthening. These delays impact the development of the automated driving system, either accelerating the car or causing it to lag behind its guidance, which in turn affects the assistance system.

[0139] Fig. 6 schematically illustrates the main components used in a vehicle to enable an automated driving mode.

[0140] In the development of an automated driving system, each component has its importance and its role. Each component has or cooperates with one or more computers that control or pilot one or more actuators and / or allow the management of information collected by sensors linked to the component.

[0141] The VHL vehicle typically includes at least one CAM camera of the multifunction front camera type, which is the main road perception device capable of detecting and identifying an obstacle upstream of the VHL vehicle in its lane of travel.

[0142] The VHL vehicle further comprises a RAD radar, coupled to the CAM camera, which is capable of measuring the distance separating the VHL vehicle from the obstacle as a function of the speed of the VHL vehicle, a CTJ computer capable of calculating the optimal trajectory of the VHL vehicle to avoid the obstacle, an intelligent BSI control unit, coupled to the CTJ trajectory computer, capable of managing the information delivered by the CAM camera and the RAD radar, and other components and sensors of the VHL vehicle including the CHS chassis (chassis controller) and an AED and its assistance system, not shown, controlled by the trajectory computer which belongs to the AD AS system, not shown.

[0143] Finally, the VHL vehicle includes a Human Machine Interface, HMI, capable of informing the driver about the consideration of the obstacle in automated driving mode and of a necessary resumption of control of the VHL vehicle according to the life situations.

[0144] All these components communicate with each other via an internal vehicle communication network, not shown, of the CAN type (an Anglo-Saxon acronym for "Controller Area Network"). Information travels from one component to another at different speeds. The assistance system operates in a closed loop and continuously recalibrates itself.

[0145] In this set of components, the DAE is the last component of the VHL vehicle guidance chain applying the final steering angle to the wheels of the VHL vehicle (steering angle) to take the trajectories calculated in automated driving mode.

[0146] The responsiveness of the DAE therefore results from a sum of processes implemented by the various computers and actuators, upstream components of the DAE, with their delays, or advances (time lags).

[0147] The slightest modification of a process and / or a control unit: frame modifications, BSI control unit updates, chassis modifications, etc., when development is well advanced and most of the control units exhibit Fixed software can impact the behavior of the AD AS system and therefore the automated driving mode and the AED assistance system.

[0148] Thus, a vehicle whose trajectory has been optimally calculated can very easily deviate from this trajectory if the time shifts of the upstream processes are not taken into account at the level of the DAE.

[0149] The present invention implements a compensation function for controlling the advance or retard (phase) of the power steering system to counteract this defect. The compensation function speeds up or slows down the operation of the power steering system depending on driving conditions (vehicle speed, lateral acceleration). This makes it possible to "boost" a "sluggish" car at 70 km / h and slow down a "too lively" car at 130 km / h, and ultimately to synchronize the response of the power steering system with the vehicle's trajectory (vehicle "in phase").

[0150] Fig. 7 illustrates the effects of this compensation on the AED of a VHL vehicle.

[0151] From left to right in the figure, one can distinguish:

[0152] - the vehicle's TCO trajectory, not shown, which was calculated in a optimal on a WH traffic lane of the vehicle;

[0153] - the TRJ trajectory of the delayed VHL vehicle, in bold, relative to the Calculated trajectory TCO;

[0154] - the TRJ trajectory of the VHL vehicle in advance, in bold line, relative to the Calculated trajectory TCO and;

[0155] - the VHL vehicle in phase with respect to the calculated trajectory TCO: the trajectories TCO and TRJ are superimposed.

[0156] According to the invention, phase control only occurs in automated driving mode, because adjusting the advance and retard of an electronically controlled dynamo (ECD) during manual driving would be very detrimental. The driver would become completely disoriented; their actions would no longer be in sync with the vehicle's behavior. In contrast, in automated driving mode, which is electronically controlled, the retard or advance is constantly taken into account, and the vehicle's behavior remains transparent.

[0157] STEERING WHEEL CONTROL IN THE CENTER

[0158] According to the guideline of the present invention, the automated driving mode allows the driver to coexist with the assistance system of the AED, in other words to intervene to support the assistance system.

[0159] When the vehicle is operating in automated driving mode, the tuning consists of determining a range of predetermined torque levels which allows the driver, depending on the level of effort applied to the steering wheel, to:

[0160] - Let the vehicle roll on its own;

[0161] - Moving the vehicle within its lane without taking a new position, for example to help the vehicle pass through tricky areas (figures 3 to 5);

[0162] - Reposition the vehicle in its lane of travel (far right, far left) etc...).

[0163] And all this without ever disabling the automated driving mode.

[0164] It must therefore be borne in mind that at every moment, in the three situations mentioned above, the driver is required to abruptly release the steering wheel, and thus to stop the cohabitation, without deactivation of the automated driving mode.

[0165] The vehicle thus "disturbed" by the human must be able to continue on its way without inconveniencing its occupants.

[0166] Cases regularly reported in changes of driving mode include an elastic and bouncy steering wheel which, when the driver lets go of the steering wheel, causes a spring effect on the car which can eventually cause nausea.

[0167] It is therefore necessary to adjust this transition zone known as the "dead zone" between releasing the steering wheel and "taking back control" of the power steering assistance system.

[0168] The present invention advantageously exploits the "active" steering wheel return function in the AD AS mode of the method according to the invention.

[0169] In Normal mode, this function usually tends to steer the steering wheel to bring the vehicle back to the center of its lane (steering wheel in the center), in various life situations.

[0170] This control is achieved via a 7-second feedback command, the intensity of which varies depending on the vehicle's speed and the vehicle's position when the steering wheel is released. The function also takes into account the level of torque applied by the driver to the steering wheel.

[0171] The "active" return is historically composed of two phases. A first phase allows the steering wheel to return to the center at a speed of 7s and a second phase allows the steering wheel to be braked at a speed of 7s during its "gravity" return to the center.

[0172] Depending on the life situation encountered, the two phases can be used in conjunction. In Normal mode, the braked return is very poorly perceived by the driver (steering wheel that "sticks", slow, unnatural which forces the driver to "search" for the steering wheel).

[0173] In Normal mode, the desired outcome is a steering wheel that always returns to center as quickly as possible. The role of the power steering is to return the steering wheel at low speeds, where the chassis and tire design are no longer sufficient to return the steering wheel to center by gravity (naturally).

[0174] The operator responsible for setting up the AED will always seek the best compromise between "comfort" and "efficiency". Optimal settings, difficult to achieve, is the one ensuring a "natural" return of the steering wheel which leads the driver to believe that it is a "gravity" return of the running gear.

[0175] Thanks to the AD AS mode according to the invention, this optimal setting can be achieved.

[0176] With ADAS mode, the "active" steering assist isn't really necessary because the specific PID controller is constantly steering the vehicle. The "gravity" steering assist (suspension + tires) at 130 km / h on the motorway is very "aggressive." So "aggressive" that, once the steering wheel is released, the dynamic response is much faster than the ADAS system can compensate for any delays, which it then has to take over.

[0177] Releasing the steering wheel at this speed after entering a small steering angle will generate a very unpleasant rolling and roll-back motion. In this situation, the return to center must be braked.

[0178] The ADAS mode advantageously allows activation of this function without impacting normal driving. It is then necessary to "phase" this braking with the natural movements of the vehicle, with the target being: steering wheel centered (zero steering angle) = calm car.

[0179] DRIVING SAFETY: STEERING WHEEL TURN DURING AN AVOIDANCE

[0180] Today, the state of the art of automobile driving is clear: No mass-produced private vehicle is currently capable of legally driving itself without any action or control from a human driver present in the vehicle.

[0181] This means that at any moment, the driver must be able to regain control of the vehicle. If the vehicle is in automated driving mode, it must be ensured that the driver's resumption of control is as natural and safe as in normal driving.

[0182] Since automated driving mode is generally activated to give the driver a break, a light level of steering effort is often required to interact with the steering wheel when the vehicle is driving itself. This light effort can have a significant impact if the driver reacts sharply to the situation, even though the system already provides strong steering assistance. The assistance then multiplies the driver's force, thus exaggerating the initially intended trajectory.

[0183] Over-revving the vehicle can then lead to an accident.

[0184] In manual driving mode, to compensate for very light assistance in extreme life situations, there are "damping" functions within the logic of the power steering assistance system which take into account other external factors (steering wheel speed, torque applied by the driver, lateral acceleration of the vehicle, etc.) to apply more " "Heavy," safe, which "calms" the vehicle. But be careful not to add too much damping, as this would detract from driving pleasure.

[0185] The present invention, thanks to the AD AS mode, incorporates much greater damping than in driving in Normal or Sport modes, without impacting the manual driving mode.

[0186] The advantage of AD AS mode in this situation:

[0187] The [Fig.8], illustrates in the form of three chronograms corresponding to time, and from top to bottom, a first chronogram illustrating the level of effort on a steering wheel turn in Normal mode, a second chronogram illustrating a level of effort on a steering wheel turn in AD AS mode for the same steering wheel turn (torque) determined illustrated in a third chronogram.

[0188] On the first and second chronograms, the effort level scale, on the ordinate, is graduated on four levels: a minimum level "Light", a maximum level "Heavy" and two equidistant intermediate levels, respectively a "low intermediate" level and a "high intermediate" level.

[0189] The amount of energy to be dissipated is proportional to the initial level of assistance. Since the effort level in Normal mode is naturally "heavier" than in AD AS mode, the compromise in effort level between "safety / control" in this situation cannot be the same as in AD AS mode.

[0190] Applying the AD AS mode damping settings to Normal mode would result in a steering wheel that is too "heavy," making it impossible for the driver to turn. Conversely, applying the Normal mode settings to AD AS mode would be ineffective in damping steering dynamics.

[0191] By comparing the first and second timing diagrams, we observe that for the same steering input (third timing diagram), the effort level in ADAS mode changes from a "Light" to a "Heavy" level (the change from minimum to maximum effort is very rapid). Whereas, in comparison with Normal mode (first timing diagram), the effort level changes from a "low intermediate" to a "high intermediate" level, between the "Light" and "Heavy" levels (minimum and maximum). The effort level in ADAS mode is therefore higher than that required in Normal or Sport mode, thus increasing safety.

[0192] The present invention, thanks to the AD AS mode, thus provides a good compromise in terms of damping without impacting the manual driving mode.

[0193] Figure 9 illustrates chronologically, from left to right, the six phases I to VI of a third-person "extreme" life situation, in the event of an evasive maneuver on a motorway, with the associated chronogram of the effort levels applied by the assistance system. the AED, and the diagram of the modes: "LxA Mode", "LxA Mode Protection", and "Manual Driving", associated.

[0194] Phase I: In this example, the VHL vehicle has been traveling in its WH lane for some time in an automated driving mode (the level of steering effort shown in the corresponding time diagram is very low ("Light ADAS") so as not to unnecessarily tire the driver during steering wheel interactions). A VPL truck is traveling in its WP lane, immediately to the right of the VHL vehicle's WH lane, upstream of the VHL vehicle.

[0195] Second phase II: The VPL truck that it is overtaking must avoid a moving obstacle such as OBM game. The level of effort on the steering wheel remains unchanged (“Light AD AS”); the VPL truck has not yet begun the avoidance maneuver.

[0196] Transition from Phase II to Phase III: The VPL truck begins to exit its WP lane on the left and starts to encroach on the WH lane of the VHL vehicle. The driver of the VHL vehicle then abruptly regains control of the VHL vehicle. The effort level in the automated driving mode changes from "Light AD AS" to a higher effort level of "Consistent AD AS," still in LxA mode.

[0197] Transition from the third phase III to the fourth phase IV: the abrupt steering input tends to over-energize the avoidance maneuver (risk of hitting a safety barrier to the left of the WH lane of vehicle VHL). The assistance system detects the increase in steering speed and, as a safety measure ("Protection Mode LxA"), applies an almost instantaneous reduction in assistance ("Very Heavy AD AS"), which, compared to the same assistance in Manual driving mode, is greater in terms of effort level, typically between a "Constant AD AS" and "Very Heavy AD AS" effort level.

[0198] Fourth IV and fifth phase V: The driver finds himself in a situation where the "Protection Mode LxA" is still activated but at the limit of deactivating the AD AS mode, with a "very heavy AD AS" at the steering wheel allowing the driver to put a lot of effort on the steering wheel and keep control over the trajectory of the VHL vehicle.

[0199] Transition from fifth V to sixth phase VI: The avoidance ends, and in this "extreme" situation the autonomous driving mode has deactivated (exit from the "functional corridor") and the driver is now in manual driving mode.

Claims

Demands

1. Method for developing a control law for a steering wheel assistance system of a motor vehicle capable of operating in an automated driving mode;said process, implemented by the assistance system, consisting of implementing a specific assistance mode, designated as AD AS mode, acting on lateral control functions of the vehicle in its lane of travel, complementary to the Normal and Sport modes already present in the vehicle, said AD AS mode being dedicated to the automated driving mode of the vehicle and controlled by a servo regulator of the assistance system whose parameterization allows to take into account, within a range of determined torque values, at least one torque applied by the driver on the steering wheel allowing to occasionally support the assistance system in life situations requiring intervention by the driver on the steering wheel, without interrupting the automated driving mode.;

2. A method according to the preceding claim, consisting of considering the torque applied by the driver on the steering wheel, in AD AS mode, as an input parameter of the assistance system, and of managing the release of the steering wheel by the driver and the resumption of control by the assistance system, so as to steer the steering wheel to bring the vehicle back to the center of its lane taking into account the speed of the vehicle and the natural movements of the vehicle, without exiting the automated driving mode.

3. Method according to the preceding claim, consisting of managing a sudden steering maneuver during an avoidance maneuver, by applying a determined level of effort greater than that required in Normal or Sport mode, thereby increasing safety.

4. A method according to any one of the preceding claims, using a state machine for switching from one mode to another; said state machine being implemented by the servo controller of the assistance system.

5. A method according to any one of the preceding claims, consisting of setting a mode transition between Normal or Sport modes and ADAS mode and vice versa, with a weight determined time assigned to each of the modes and, to adjust the transition time from one mode to another, between an instantaneous transition time and a determined maximum transition time.

6. A method according to any one of the preceding claims, consisting of piloting the advance or retard of the assistance system to maintain the trajectory (TRJ) of the vehicle (VHL) in phase with an optimal trajectory (TCO) determined only in the automated driving mode.

7. A method according to any one of the preceding claims wherein the control regulator is a proportional gain PID regulator.

8. A method according to any one of the preceding claims wherein the lateral control implements one of the following functions of a driver assistance system, called AD AS system: a lane keeping assistance function, called LKA, and a lane positioning assistance function, called LPA or a combination of the two functions LKA and LPA, called LxA.

9. Motor vehicle (HV) comprising an automated driving mode and an electrically assisted steering wheel (EAS); said vehicle (HV) comprising an assistance system developed by the method according to any one of the preceding claims.

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