Automatic control method and system for virtual restraint of a land vehicle in a track

Abstract

The present invention relates to a method (900; 1000) for automatically restraining a land vehicle. In an embodiment of the present invention, the method (900; 1000) provides that a control unit (30) performs the following steps: define (900) a set of points of a track on which the vehicle can freely move, the track including at least one edge defining a boundary of the track that the vehicle must not cross; determine (1001) the dynamics and position of the vehicle based on information provided by a plurality of sensors on the vehicle; calculate (1005) an intervention area of the track based on the current position and dynamics of the vehicle and its position from the at least one edge; the area to be avoided extends from at least one edge of the track towards the current position of the vehicle within the track; determine (1007) whether the vehicle is at least partially within the intervention area; and if so, control (1013) at least one actuator to modify the vehicle dynamics and perform an exit maneuver to move the vehicle out of the intervention area. In particular, calculating (1005) the intervention area comprises performing the following steps: A first collision area is calculated (10055) based on the current position and dynamics of the vehicle, its position from the at least one edge, and the driver's ability to change the vehicle dynamics by acting on at least one actuator. A second collision area is calculated (10057) based on the current position and dynamics of the vehicle, its position from the at least one edge, and the control unit's ability to change the vehicle dynamics by acting on at least one actuator. The first collision area and the second collision area correspond to areas of the track where a vehicle moving according to its current dynamics will inevitably reach and / or cross at least one edge when driven by the driver or the control unit, respectively. Finally, an intervention area is defined (10058) as the area resulting from the difference between the first collision area and the second collision area.

Description

[Technical Field]

[0001] The present invention relates to the automotive field, and more particularly to a method and associated automatic control system for virtual restraint of a vehicle on a race track. [Background technology]

[0002] Currently, electronic stability control (ESC) systems help vehicle drivers maintain the trajectory they have set, eliminating or at least significantly reducing the risk of accidents.

[0003] Furthermore, autonomous or semi-autonomous driving systems are known that overlap the driver's control by driving the vehicle on his behalf according to predetermined criteria, in particular to avoid collisions of the vehicle with obstacles on the track.

[0004] For example, US2015 / 0302751 proposes a driver assistance method that intervenes by controlling the vehicle's braking and steering when on-board sensors identify an obstacle. Similarly, US9,637,050 describes a driver assistance method that intervenes in steering and braking based on information exchanged between vehicles and / or the electronic infrastructure surrounding the vehicle's trajectory (i.e., V2V vehicle-to-vehicle communication and V2I vehicle-to-infrastructure communication).

[0005] US 10,882,518 discloses a driver assistance method that calculates a trajectory to avoid a collision between a vehicle and an obstacle, and makes the vehicle follow that trajectory through an automatic brake and steering control system. Furthermore, the method calculates a post-avoidance trajectory to determine whether there are any additional obstacles to avoid other than the initial obstacle.

[0006] Finally, JP6654641 proposes an automated driving system for a vehicle that is activated when a predetermined condition (e.g., risk of collision with an obstacle) is detected and that transfers control to the vehicle driver only if the driver's commands substantially match the commands generated by the automated driving system.

[0007] Furthermore, D. Hoehener et al., "Design of a Lane Departure Driver Assistance System Based on Safety Specifications," 2016, IEEE 55th Conference on Decision and Control (CDC), pp. 2468-2474, and US2017 / 183004, describe other automated or semi-automated driving systems that overlap driver control.

[0008] Known solutions ensure greater driving safety but are not suitable for use on vehicles that have essentially a performance / playful purpose, such as driving on a race track.

[0009] In fact, these methods and systems tend to excessively restrict the driver's control of the vehicle, thereby limiting the driver's ability to improve his driving skills and to develop a sporty and safe driving style, and more generally limiting the enjoyment of driving.

[0010] Therefore, there is a need in the art for a driver assistance method and system that allows a driver to drive a vehicle while ensuring driver and vehicle safety without interfering with the driver's driving style, e.g., a sporty driving style. DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0011] SUMMARY OF THE INVENTION An object of the present invention is to overcome the drawbacks of the prior art.

[0012] In particular, it is an object of the present invention to provide a method and system that can ensure the safety of the driver and the vehicle without interfering with the driver's driving style.

[0013] In particular, it is a further object of the present invention to provide a method and associated system for identifying vehicle dynamic conditions that may cause the vehicle to leave a permitted track, such as a race track, and for rapidly correcting the vehicle dynamic conditions to avoid the race track departure.

[0014] In fact, the applicant has discovered that known ESC systems cannot guarantee that the vehicle will stay on the race track if the driver sets an incorrect trajectory, for example by delaying the apex too much.

[0015] These and other objects of the present invention are achieved by a system incorporating the features of the appended claims, which form an integral part of this specification. [Means for solving the problem]

[0016] According to a first aspect, the present invention relates to an automatic restraint of a land vehicle, the vehicle being considered comprising a control unit, a plurality of sensors configured to measure quantities indicative of the dynamics of the vehicle, and at least one actuator configured to influence the dynamics of the vehicle, the plurality of sensors and the at least one actuator being connected to the control unit.

[0017] In an embodiment of the invention, the method provides that the control unit defines a set of points of a track along which the vehicle may freely move, the track including at least one edge defining a boundary of the track that the vehicle must not cross. Preferably, the control unit periodically determines the dynamics of the vehicle and the spatial position of the vehicle based on information provided by the plurality of sensors.

[0018] Starting from the position and dynamics of the vehicle and the position of at least one edge, the control unit calculates the intervention area.

[0019] The control unit then determines whether the vehicle is at least partially within the intervention area, and if so, controls at least one actuator to modify the vehicle dynamics and perform an exit maneuver to move the vehicle out of the intervention area.

[0020] The term "dynamics" as used herein refers to a set of information related to the movement of a vehicle in space as a function of time. Preferably, vehicle dynamics includes information such as, but not limited to, longitudinal velocity, lateral velocity, yaw rate, heading, yaw angle, steering angle, and individual wheel speeds. Alternatively, vehicle dynamics may also include information regarding roll and pitch rates and suspension extension. As will be apparent to those skilled in the art, the information included in vehicle dynamics allows for the calculation of multiple derived information, such as corresponding longitudinal, lateral, and yaw acceleration values associated with the vehicle.

[0021] In particular, to calculate the intervention area, the following steps are performed: A first collision area is calculated based on the vehicle's current position, dynamics, position from at least one edge, and the driver's ability to activate at least one actuator to change the vehicle dynamics, and a second collision area is calculated based on the vehicle's current position, dynamics, position from at least one edge, and the control unit's ability to activate at least one actuator to change the vehicle dynamics. The first collision area and the second collision area correspond to areas of the track where the vehicle moving according to the current dynamics will inevitably reach and / or cross at least one edge when driven by the driver or the control unit, respectively. Finally, an intervention area is defined as an area resulting from the difference between the first collision area and the second collision area.

[0022] This method ensures the driver sufficient driving freedom, but at the same time prevents the vehicle from straying from the designated track, thus preventing damage to the vehicle and / or driver that may result from such an event.

[0023] The method according to an embodiment of the present invention completely overturns the concept of vehicle stability control. In fact, the method does not provide any driver assistance and allows the driver to freely control vehicle commands without overlapping stability control systems. This allows the driver to try new driving styles and maximizes driving pleasure.

[0024] It offers the possibility to try new driving styles and guarantees maximum driving enjoyment.

[0025] However, at the same time, continuous monitoring of the vehicle is performed and if it is detected that the dynamic state of the vehicle has reached the intervention area, i.e. the boundary of the feasibility of a trajectory that keeps the vehicle within a specified track, for example a race track, a quick overlap with the driver's commands can modify the vehicle dynamics in order to keep the vehicle on the track.

[0026] In fact, the calculation of the two collision areas makes it possible to precisely identify the optimal intervention area that guarantees avoidance of a collision with the edge of the truck while minimizing driver intervention.

[0027] In other words, the intervention region calculated in this way guarantees sufficient spatial and temporal edges so that the control unit can intervene to correct the vehicle dynamics only when actually necessary.

[0028] As will be apparent to those skilled in the art, the method does not require exteroceptive sensors, such as cameras, radar, LiDAR, etc., for its implementation. In other words, the method according to an embodiment of the present invention can be implemented in a vehicle with "standard" on-board instrumentation in the automotive field. Furthermore, because it does not require the presence of exteroceptive sensors, the method according to an embodiment of the present invention can be implemented in a vehicle without the vehicle being overloaded or having reduced aerodynamics due to the presence of such sensors.

[0029] In one embodiment, the method includes determining the driver's ability to modify vehicle dynamics by selecting at least one value indicative of the ability to modify vehicle dynamics from a set of predetermined values.

[0030] Preferably, these values are based on an analysis of the driving performance of a sample of drivers in the truck of interest.

[0031] This solution allows for a simple and quick definition of the driver's ability to modify vehicle dynamics without the need for racetrack or synthetic test runs.

[0032] In another embodiment, the driver's ability to modify vehicle dynamics is determined by measuring at least one value indicative of the driver's ability to modify vehicle dynamics while the driver is driving the vehicle, for example, on a race track or through a simulation.

[0033] In this way, the actual ability of the driver to modify the vehicle dynamics can be accurately assessed and "tailor-made" driver assistance can be obtained.

[0034] In one embodiment, the value indicative of the ability to change vehicle dynamics includes at least one of a maximum steering rate, a maximum braking force, and an acceleration that the driver is capable of performing.

[0035] In one embodiment, the steps of calculating the first collision area and the second collision area each comprise calculating a subset of points at which any trajectory, which can be set by the driver or the control unit, respectively, reaches / crosses at least one edge based on vehicle dynamics due to a reachability problem.

[0036] This solution allows the impact area to be defined accurately and reliably.

[0037] In one embodiment, the method provides for calculating an intervention area for each edge of the track traveled by the vehicle.

[0038] In this way, vehicle dynamics can be quickly modified at any point during the vehicle's movement.

[0039] Alternatively, the at least one edge corresponds to an edge of a track that is intersected by the vehicle's direction of travel or that is less than a threshold distance from the vehicle position.

[0040] The computational load performed by the control unit can be limited by simply and quickly identifying relevant edges that are likely to require the execution of corrective interventions in the vehicle dynamics.

[0041] In one embodiment, the step of defining a set of points of the track over which the vehicle may freely move includes obtaining geographic data relating to a geographic area including the track, and identifying geographic coordinates of the track based on the obtained geographic data.

[0042] As a result, the geographic coordinates of a track are defined to correspond to the points of the track, and the remaining geographic coordinates are defined as points that do not belong to the track. Finally, at least one edge is defined as a subset of points of the track that are adjacent to each other and adjacent to at least one point that does not belong to the track.

[0043] This definition of the tracks that the vehicle can travel is particularly easy to perform and requires no stored storage space, so the tracks can be calculated by an electronic device with stored resources and quickly transferred via a wired or wireless connection.

[0044] In one embodiment, the set of points of the track may be supplemented with coordinates of at least one additional area adjacent to a portion of the set of points of the track, the additional area being suitable for passage of the vehicle.

[0045] This operation allows for the definition of tracks within which vehicle movement occurs based on the actual configuration of the geographic area containing the track, the type of vehicle, and / or the driving style of the driver.

[0046] In one embodiment, controlling the at least one actuator to modify the dynamics of the vehicle includes calculating an exit trajectory from the intervention region based on a current position and dynamics of the vehicle and a distance of the vehicle from the at least one edge, and performing the exit maneuver by controlling the at least one actuator to follow the exit trajectory.

[0047] Preferably, the exit trajectory is calculated as a solution of the following relationship:

number

[0048] The exit trajectory is calculated simply and quickly, allowing the vehicle dynamics to be modified in a timely manner to ensure that the track exit is avoided.

[0049] Another aspect of the invention relates to a vehicle including a control unit, a plurality of sensors configured to measure quantities indicative of vehicle dynamics, and at least one actuator configured to influence the vehicle dynamics, wherein the plurality of sensors and the at least one actuator are connected to the control unit.

[0050] Furthermore, the control unit is configured to perform the method according to any one of the above embodiments.

[0051] A vehicle equipped with the above features can achieve the same advantages as above. [Brief explanation of the drawings]

[0052] [Figure 1] FIG. 1 is a block diagram of a system according to one embodiment of the present invention. [Figure 2] FIG. 2 is a qualitative representation of a map of possible routes a vehicle may take, according to one embodiment of the present invention. [Figure 3] FIG. 3 is a flowchart of a mapping method according to one embodiment of the present invention. [Figure 4] FIG. 4 is a flowchart of a method for restraining a vehicle according to one embodiment of the present invention. [Figure 5] FIG. 5 is a logical block diagram of a software application executed by a control unit onboard a vehicle according to one embodiment of the present invention. [Figure 6] FIG. 6 is a flowchart of the procedure for calculating the intervention area included in the flowchart of FIG. 4 and implemented by a module of the software application of FIG. [Figure 7] Figure 7 is a qualitative representation of the intervention area calculated by the procedure in Figure 6. [Figure 8] FIG. 8 is a qualitative representation of the physical quantities used in the procedure for calculating the intervention region of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0053] Further features and advantages of the present invention will become more apparent from the description of the accompanying drawings.

[0054] The present invention will now be described with reference to several examples provided for purposes of illustration and not limitation and illustrated in the accompanying drawings, which illustrate various aspects and embodiments of the invention, and in which reference numerals designating structures, components, materials, and / or similar elements in different drawings are designated with like reference numerals where appropriate.

[0055] While the invention is susceptible to various modifications and alternative constructions, certain preferred embodiments have been shown in the drawings and are described in detail below. It is to be understood that in all cases there is no intention to limit the invention to the particular embodiments shown, but rather the invention is intended to cover all modifications, alternatives, and equivalent arrangements falling within the scope of the invention as defined by the claims.

[0056] The use of "for example," "e.g.," and "or" indicates open-ended, non-exclusive alternatives unless otherwise stated. The use of "including" means "including, but not limited to," unless otherwise stated.

[0057] Referring to the block diagram of FIG. 1, an automatic control system 1 (hereinafter simply "system") for virtual restraint of a vehicle on a race track according to an embodiment of the present invention is included in a vehicle V (a car in the considered example).

[0058] The system 1 comprises a group of actuators generally designated by the reference numeral 10, which are known per se and will not be described in detail here for the sake of brevity. In the non-limiting example considered here, the system 1 comprises: - group 11 of actuators for steering or active steering; - Brake pump (or master cylinder) pressure control group 12; It is equipped with:

[0059] Preferably, but not exclusively, the system 1 comprises: - group 13 of actuators of driving torque; a braking torque control unit 14 acting independently on each wheel of the vehicle V; Equipped with.

[0060] Furthermore, the system 1 comprises a number of sensors, generally designated by the reference numeral 20, in particular: a positioning sensor 21 of the vehicle V, for example a satellite positioning system GNSS (acronym for Global Navigation Satellite System) or a positioning system based on a camera or a localization algorithm; an inertial platform 22, preferably of the center-of-gravity type with six degrees of freedom, for example including three accelerometers and three gyrometers; at least one speed sensor 23 coupled to one of the wheels of the vehicle, preferably a speed sensor 23 for each wheel of the vehicle V; a steering angle sensor 24; Equipped with.

[0061] Finally, the system 1 comprises a processing unit, or control unit 30, configured to drive the group of actuators 10 and to acquire the measurements provided by the sensors 20. In the example considered, the control unit 30 comprises one or more computers 31, such as a processor, microprocessor, microcontroller, ASIC, FPGA, DSP, etc., a memory module 32 with one or more non-volatile and volatile memory elements, and auxiliary modules, such as a power supply module 33 and a communication module 34, configured to exchange data, for example, via a CAN / LIN bus and / or a wireless communication channel (e.g. Bluetooth, Wi-Fi, ZigBee, etc.).

[0062] In an embodiment of the present invention, the control unit 30 stores information about movable tracks (hereinafter simply referred to as tracks). In the example considered, the control unit 30 stores a detailed map M of a circuit or race track P on which the vehicle V can travel, as shown schematically in Figure 2. The map M defines the race track P by a set of points corresponding to geographic coordinates, which are preferably provided by the same position detection system as that used by the position sensor 21.

[0063] In an embodiment of the present invention, the map M essentially consists of two sets of points: a. A set of track points pT where the presence of a vehicle is permitted; and b. A set of non-track points pN where the presence of a vehicle is not allowed.

[0064] Generally, the set of track points pT corresponds to the surface of the racetrack P along which the vehicle V is expected to travel. Alternatively, the set of track points pT may include points pA belonging to additional surface portions, such as escape ways, secondary paths of the racetrack P, and / or areas adjacent to the racetrack P along which the vehicle V may travel without being damaged. Otherwise, non-track points pN constitute all remaining points of the map M.

[0065] In an embodiment of the present invention, a set of edge points pM is defined that is a subset of track points pT that are adjacent to at least one non-track point pN.

[0066] In one embodiment, the map M of the race track P is created by a mapping method 900 described below, a flow chart of which is shown in Figure 3. Preferably, the method 900 is performed by an electronic device 50 (shown in Figure 1) external to the vehicle V, such as a general-purpose computer with a software application 90 suitably configured to perform the method 900.

[0067] First, geographic data is acquired for the area including the race track P (step 901). The geographic data may include one or more of a set of geographic coordinates defined by one or more of GNSS, GIS (geographic information system) data, map data, aerial / satellite imagery, etc. Such geographic data may be acquired by one or more corresponding computer systems (not shown, e.g., a geographic map repository containing GPS coordinates).

[0068] Then, identify the track that defines the race track P (step 903). This operation can be performed manually or by a software application configured to analyze one or more satellite images of the area that includes the race track P to identify the track of the race track P.

[0069] The geographic coordinates corresponding to the identified race track P are added to the set of track points pT (step 905).

[0070] Alternatively, additional surfaces are identified manually or by a software application, and their points pA are added to the set of track points pT (step 907). For example, the software application may be configured to identify possible additional surfaces based on analysis of one or more satellite images of the area including the racetrack P, and the addition of points pA associated with these additional surfaces may then be manually confirmed by a human operator.

[0071] The remaining coordinates are added to the set of non-track points pN (step 911).

[0072] Thereafter, edge points pM are identified (step 913). Advantageously, the edge points are further divided into pairs of edge subsets pM1 and pM2 that contain coordinates that are adjacent to each other. In other words, each subset of edge points pM1 and pM2 consists of points that define one of the two edges of the racetrack P.

[0073] Finally, the map M, which includes the set of track points pT, the subset of edge points pM1 and pM2, and the set of non-track points pN, is available for transfer to the control units 30 of one or more vehicles V (step 915).

[0074] The map M is then transferred to the control unit 30 and the electronic device 50 is connected to the control unit 30 via a wired or wireless connection.

[0075] In an embodiment of the present invention, the control unit 30 executes a method 1000 for automatically restraining a vehicle V, with the aim of protecting the driver from dangerous situations and restricting the driver's freedom of control as little as possible.

[0076] The method 1000, the flow chart of which is shown in FIG. 4, preferably periodically, for example with a sampling period of about 5 to 10 milliseconds, comprises the following steps: - determining the dynamics of the vehicle V (step 1001), where the term "dynamics" means a set of information related to the movement of the vehicle in space as a function of time, including but not limited to longitudinal velocity, lateral velocity, yaw rate, yaw angle, steering angle, and individual wheel speeds (alternatively, roll velocity, pitch velocity, and suspension extension); - determining the position of the vehicle V within the race track P contained in the map M (step 1003), obtained by dead reckoning operations or positioning algorithms based on values provided by the positioning sensors 21 and / or the inertial platform 22, in the example considered, the position of the vehicle V corresponding to the position of the center of mass of the vehicle V; - calculating (step 1005) at least one intervention zone Zi included in the race track P, i.e. included in the set of track points pT, based on the position of the vehicle V (in particular with respect to the points of the edge subsets pM1 and pM2), the dynamics of the vehicle V and the type of control that the control unit 30 can perform on the vehicle V; - determining whether the vehicle V enters at least partially into the intervention zone Zi (decision step 1007), If the vehicle is not in an intervention area Zi (exit branch N of step 1007), the method does not carry out any intervention Zi (step 1009), leaving the control of the vehicle V entirely to the driver; On the other hand, if the vehicle has entered the intervention area Zi (exit branch Y of step 1007), the method 1000 calculates (step 1011) an exit trajectory from the correction area that keeps the vehicle V within the race track (i.e., contained in the area defined by the set of track points pT); - controlling the actuators 10 of the vehicle V to modify the dynamics of the vehicle V so as to perform an exit maneuver according to the calculated exit trajectory (1013); - After performing the exit operation, control of the vehicle V is returned to the driver (step 1015), provides for the execution of the

[0077] Preferably, the method 1000 is repeated upon completion of step 1007 or step 1011 for as long as the vehicle V is moving on the race track P.

[0078] In one embodiment of the present invention, the control unit 30 stores and executes a software product 100 that implements the method 1000 .

[0079] In the considered example, the software 100 executed by the control unit 30 implements three main logic modules, as shown in the block diagram of Figure 5: an unavoidable collision set calculation module, or module ICS101 (acronym for Inevitable Collision Set), a reference generation module, or module RG102 (acronym for Reference Generation), and a vehicle dynamics control module, or module VDC103 (acronym for Vehicle Dynamics Control).

[0080] As will be explained in more detail below, module ICS101 is configured to define one or more intervention areas Zi, preferably in real time (steps 1001 to 1005 of method 1000). Module RG102 is configured to calculate an exit trajectory from the intervention area Zi (steps 1007 to 1011 of method 1000). Finally, module VDC103 is configured to operate actuators 10 so that the vehicle V follows the exit trajectory calculated by module RG102 and returns control of the vehicle to the driver (steps 1013 and 1015 of method 1000).

[0081] In detail, the definition of the intervention zone Zi causes the module ICS101 to carry out the following substeps illustrated in the flowchart of FIG.

[0082] Beforehand, for example in a system initialization step, the module ICS101 obtains (for example stored in the memory module 32) the following data relating to the vehicle V (step 10051): a set of characteristics of the vehicle V, including, but not limited to, the type of tires fitted, the nominal friction of the vehicle V, the wheelbase of the vehicle V, and the mass of the vehicle V; - the control configuration, i.e. which actuators 10 can be autonomously controlled by the control unit 30, for example selecting among: a) Active braking only, b) Active braking and active steering; c) active steering and torque vectoring, i.e., the ability to impose a desired yaw moment (e.g., through a differential torque), or d) Active steering only, the ability of the control unit 30 to modify the dynamics of the vehicle V—for example, the response time required for the control unit 30 to control one or more of the actuators 10 (e.g., to brake and / or steer), the maximum steering speed (measured in rad / s), the maximum braking force or acceleration capacity (i.e., deceleration measured in m / s), the ability to impart additional yaw moment by torque vectoring or differential braking (measured in Nm), etc.; and -The ability of the driver to change the dynamics of the vehicle V in response to external demands (e.g. the presence of an obstacle or the setting of a curve) - for example the response time required for the driver to provide a command to the vehicle (e.g. to brake and / or steer), maximum steering speed (measured in rad / s), maximum braking force or acceleration capacity (i.e. deceleration measured in m / s), etc.

[0083] The characteristics of the vehicle V, its control configuration, and the ability to modify the dynamics of the control unit 30 are known data and are provided to the control unit 30 by the manufacturer / fitter of the vehicle V by the device 50, for example, in a manner similar to that described above with respect to the map M. Otherwise, the ability to modify the driver's dynamics is preferably selected from a set of adjustable values based on the driver's level of experience. In one embodiment, the values are based on an analysis of the driving performance of a number of sample drivers on the considered track, e.g., for each driver, the maximum steering speed and maximum deceleration (or acceleration) set by the driver-controlled actuators are calculated, and these two measurements are weighted as a value indicative of the driver's degree of experience in driving the vehicle and included in the set of said values.

[0084] Alternatively, the ability to modify the driver's dynamics is determined empirically during a preliminary calibration step of the system 1 by means of real or simulated driving tests.

[0085] The module ICS101 is configured to determine, preferably in parallel, an intervention area for each subset of edge points pM1 and pM2 (hereinafter also referred to simply as edges pM1 and pM2 for the sake of brevity) of the race track P based on the acquired data of the vehicle V and the measurements provided by the sensors 20. In the following, for the sake of brevity, the procedure for calculating the intervention area will be described only for one of the edges, the edge pM1, but the same procedure applies mutatis mutandis to the other edge pM2 of the race track P.

[0086] The module ICS101 calculates (step 10053) a first collision region ICS1 of the race track P relative to the edge pM1, i.e. a set of track points pT called the unavoidable collision set. In particular, once the vehicle V enters the first collision region ICS1, the driver cannot perform any maneuver using only the actuators under his control, taking into account the above boundaries, that would prevent the vehicle V from reaching the edge pM1 and exiting the race track P.

[0087] Furthermore, module ICS101 calculates (step 10055) a second region ICS2 of the race track P. In particular, once the vehicle V enters the first collision region ICS1, the control unit 30 cannot use all the actuators under its control to perform an operation that would prevent the vehicle V from leaving the race track P.

[0088] 7, the collision areas ICS1 and ICS2 extend from the edge pM1 of the race track P towards the inside of the race track P. In particular, the first collision area ICS1 has a larger surface than the second collision area ICS2, because the control unit 30 has a greater ability to modify the dynamics of the vehicle V than the driver has to modify the dynamics of the vehicle V.

[0089] In one embodiment, the points included in the collision areas ICS1 and ICS2 are calculated based on the dynamics of the vehicle V defined according to the following equation:

number

[0090] Here, as shown diagrammatically in Figure 8, β is the drift, i.e., the angle formed between the vehicle's velocity vector v and its longitudinal axis. Cr and Cf are the so-called "cornering stiffness," i.e., the relationship between the side slip of the rear and front wheels tr and tf and the lateral forces Fyr and Fyf acting on the wheels. v is the forward velocity coefficient of vehicle V. m is the mass of vehicle V. δ is the steering angle of wheels tr and tf. lf and lr are the distances between the center of mass cM of vehicle V and the front and rear axles of vehicle V, respectively. J is the vehicle's moment of inertia. r is the vehicle's yaw rate. MY is the additional yaw moment caused by differential braking. Furthermore, δ (Equation 6) is the steering velocity. v (Equation 7) is the acceleration command provided by the driver.

[0091] In particular, the points included in the collision regions ICS1 and ICS2 are calculated as points at which all possible control sequences that can be executed by the driver in the case of ICS1, and all possible control sequences that can be executed by the control unit 30 in the case of ICS2, starting from the current dynamics of the vehicle V, reach / cross the edge pM1, based on the reachability theory defined in: Kolmanovsky and E. G. Gilbert, "Theory and Computation of Disturbance-Invariant Sets for Discrete-Time Linear Systems", Mathematical Problems in Engineering, Vol. 4, No. 4, pp. 317-367, 1998; I. Mitchell, "Comparing Forward and Backward Reachability as a Safety Analysis Tool", Hybrid Systems Computation and Control, Springer, 2007, pp. 428-443; and T. Fraichard and H. Asama, "Inevitable Collision States - A Step Towards Safer Robots?", Advanced Robotics, Vol. 18, No. 10, pp. 1001-1024, 2004. These are incorporated herein by reference.

[0092] In the considered example, it is not possible to obtain a closed form for the state space trajectory (i.e., the variables that appear in differential form in equations 1-7) that starts from equations 1-7 and reaches or crosses edge pM1. Therefore, module ICS101 is configured to solve the following numerical system using equations 1-7:

number

[0093] where _xD835_xDC94_ xD835 _ xDFCE includes an initial point of the trajectory, e.g., included in the set of track points pT, that leads the vehicle V to a point on the edge pM1 or a point beyond the edge pM1 (e.g., the vehicle V reaches the set of non-track points pN), K is a set of collision states, U is a set of possible control actions that the driver can take for the first collision area ICS1 or that the control unit 30 can take for the second collision area ICS2, and u (Equation 8) is one of the control actions included in the set U.

[0094] , initial point _xD835_xDC94_ xD835 _ xDFCE Starting from , the set of maximally reachable points (or maximally reachable set) R where the vehicle V is located is defined as:

number

[0095] The set of reachable points that do not collide with edges, or the reachable set taking collisions into account, is defined as follows:

number

[0096] Here, τ denotes a time variable between 0 and t.

[0097] Therefore, the collision areas ICS1 and ICS2 are defined as follows:

number

[0098] Advantageously, the definition of the collision regions ICS1 and ICS2 is carried out by module ICS101 through a recursive formulation of the solution that discretizes time.

[0099] Below is pseudocode for the calculation of collision regions ICS1 and ICS2 performed by module ICS101 according to an embodiment of the present invention.

[0100] input: - State space (S) - corresponds to a set of track points pT, - Prohibited area (K) - corresponds to a set of non-track points pN, - time discretization step △t, a set U of possible corrective actions that the driver can take for the first crash area ICS1 or that the control unit 30 can take for the second crash area ICS2;

[0101] Pseudo-algorithm: Initialization:

number

number

[0102] In particular, in the step Xf ← Xs, states that can be avoided with the available control actions are excluded from the set Xf. This operation consists of Pontryagin differencing. In detail, considering the trajectory change function as a function of the possible control actions g(U)Δt, starting from a certain point, it is determined whether it is possible to identify a vector that avoids the set R(k,k) calculated in the previous iteration, and this point is excluded from the set R(k,k+1) calculated in the current iteration.

[0103] Furthermore, in the following steps:

number

[0104] The algorithm is repeated until the collision region does not grow between two successive iterations, i.e.

number

[0105] Finally, the total conflict area ICS can be defined as the union of the set R(k,k) containing the prohibited geographic area K and the intersection of the disallowed map area K and the state space S, i.e.,

number

[0106] The intervention area Zi is calculated as the subset of points of the set of track points pT that are included in the difference between the first collision area ICS1 and the second collision area ICS2 (step 10057).

[0107] In other words, the collision areas ICS1 and ICS2 resemble dynamic "extensions" of a physical boundary that must not be crossed, i.e., the edge of the race track P. The more the vehicle V "points" towards the physical boundary, i.e., in the forward direction, and more generally, the closer one dynamically brings the vehicle V to one of the edges of the race track P, the more this boundary must be widened, or similarly "approached" by the vehicle V, thereby generating a virtual puffer area that can modify the dynamic characteristics of the vehicle V to avoid it exiting the race track.

[0108] The intervention area Zi calculated in this way is transmitted to the module RG102 (step 10059).

[0109] When module RG102 determines that vehicle V (in particular the position of its center of mass) is within the intervention region Zi calculated by module ICS101 (step 1007), the position and dynamics of vehicle V are used as a starting point to generate an exit trajectory that allows keeping the edge of vehicle V within the racetrack P.

[0110] In particular, in the calculation of the exit trajectory (performed in step 1011 of method 1000), it is fundamental to ensure continuity of the control variables. In a preferred embodiment, module RG102 is configured to calculate the formulaic exit trajectory starting from a differential mode (or velocity form) problem.

[0111] In the example problem, the exit trajectory is calculated as the solution of the following equation:

number

[0112] where t denotes time, T denotes the distance between the vehicles, V denotes the edge of the race track P (usually corresponding to the nearest edge) on which the collision areas ICS1 and ICS2 extend, dmin denotes the threshold distance value allowed between the vehicles and the edge of the race track (for example, more than half the width of the vehicle V), x denotes the position of the vehicles in space, and u includes variables controllable by the control unit 30 as allowed by the control configuration in use.

[0113] The prediction period T is determined by the computational capabilities of the control unit 30, and it is generally found that the longer the prediction period T, the better the calculated trajectory. However, since relation (12) is solved with a "receding horizon" logic at each sampling instant, the prediction period T does not necessarily have to be the time required for the vehicle to reach an edge (e.g., an obstacle at a curve or the boundary of a racetrack). Research conducted by the applicant has found that prediction periods in the range of 1 to 3 seconds provide sufficiently accurate predictions.

[0114] The trajectory calculated by module RG102 is communicated to module VDC103, which modifies the dynamics of vehicle V to follow this trajectory (step 1013 of method 1000). In particular, module VDC103 operates essentially as a closed-loop control system whose task is to actuate actuators 10 to follow the trajectory calculated by module RG102.

[0115] Module VDC103 also implements returning control of vehicle V to the driver (performed in step 1015 of method 1000). In the considered example, module VDC103 is configured to return control to the driver only when the vehicle has left the initial crash region ICS1 (i.e., the region of maximum amplitude) and the commands (i.e., control variables) to actuators 10 that module VDC103 is calculating substantially correspond to the commands that the driver is imposing on vehicle V using the steering wheel, pedals, and / or other input elements. In particular, the driver's commands include one or more of the acceleration imposed on vehicle V (determined based on the accelerator pedal position using throttle-by-wire technology), braking torque (determined by measuring the brake pump pressure), and steering torque (a measure of the torque applied to the steering by the driver). In particular, if the values of the imposed acceleration and / or braking torque correspond to those imposed by module VDC103 and / or if the steering torque is lower than a predetermined threshold (indicating that the driver is holding the steering wheel without trying to counter the actions of module VDC103), the driver is considered ready to resume control of vehicle V and module VDC103 hands over control to the driver (i.e. stops sending commands to the actuators).

[0116] However, the above examples should not be construed in a limiting sense, as the invention so conceived is obviously susceptible to numerous modifications and variations.

[0117] For example, the map may include obstacles present on the race track in the set of non-track points. To this end, in one embodiment, the system is configured to detect and / or receive information regarding the state of the race track and / or the presence of obstacles / vehicles within the race track and update the map accordingly. For example, the map may be updated immediately when the state of the race track and / or the presence of obstacles / vehicles changes, or the map may be updated periodically. In this case, the system determines the collision area taking the obstacles into account and intervenes to correct the trajectory if the driver reaches a position where the obstacle cannot be avoided using only the actuators under his control.

[0118] In another embodiment, the creation of the map is performed directly by the vehicle's control unit and verified / modified by the operator or driver himself via the vehicle user interface. In other words, the vehicle can define the map, and in particular the permitted tracks along which the vehicle must travel, by uploading information previously processed by an external device (e.g. the map itself) or by directly processing geographic data, images and / or user input to obtain such a map.

[0119] As will be apparent to one skilled in the art, one or more steps of the above methods may be performed in parallel with one another or in a different order than that described above. Similarly, one or more optional steps may be added or removed from one or more of the above procedures.

[0120] Naturally, all the details may be replaced by other technically equivalent elements.

[0121] In conclusion, the materials used in the above-mentioned devices, apparatuses and terminals, as well as the shapes and accompanying dimensions, can be arbitrarily selected according to specific implementation needs without departing from the scope of protection of the following claims.

Claims

1. A method for automatically restraining a land vehicle, comprising a control unit (30), a plurality of sensors (20) configured to measure quantities indicative of vehicle dynamics, and at least one actuator (10) configured to influence the vehicle dynamics, said plurality of sensors (20) and said at least one actuator (10) being connected to the control unit (30), said method comprising: - defining a set of points of a track on which the vehicle may freely move, the track including at least one edge defining a boundary of the track that the vehicle must not cross (900); determining (1001) vehicle dynamics based on information provided by said plurality of sensors (20); determining (1003) a spatial position of the vehicle based on information provided by said plurality of sensors (20); - calculating (1005) an intervention area of the track based on the vehicle's position, dynamics and position from at least one edge, the intervention area being contained within the track; determining (1007) whether the vehicle is at least partially within the intervention area; If the determination is positive, a step (1013) of controlling said at least one actuator (10) to modify the dynamics of the vehicle and perform an exit maneuver to move the vehicle out of the intervention area; Run The step of calculating the intervention area (1005) comprises: Calculating (10053) a first collision area based on the current position of the vehicle, its dynamics, its position from at least one edge, and the driver's ability to change the vehicle dynamics by actuating said at least one actuator (10); Calculating (10055) a second collision area based on the current position of the vehicle, its dynamics, its position from at least one edge, and the ability of said control unit (3) to activate said at least one actuator (10) to modify the vehicle dynamics; - a step (10057) of defining an intervention area as an area resulting from the difference between the first collision area and the second collision area, the first collision area and the second collision area respectively corresponding to an area of the track where it is inevitable that the vehicle moving according to its current dynamics will reach at least one edge and / or cross at least one edge when driven by the driver or the control unit (30); A method (900; 1000) comprising:

2. 2. The method (900; 1000) of claim 1, further comprising a step (10051) of determining the ability of the driver to modify the vehicle dynamics by selecting at least one value indicative of the ability to modify the vehicle dynamics from a set of predetermined values or by measuring at least one value indicative of the ability of the driver to modify the vehicle dynamics while driving the vehicle, comprising:

3. 3. The method (900; 1000) of claim 2, wherein the value indicative of the ability to change the dynamics of the vehicle comprises at least one of the maximum steering speed, maximum braking force, and maximum acceleration that the driver can perform.

4. A method (900; 1000) according to any one of claims 1 to 3, wherein the steps (10053, 10055) of calculating the first collision area and the second collision area respectively comprise calculating a subset of points from which any trajectory, which can be set by the driver or the control unit (30), respectively, leads to reaching / crossing at least one margin, based on the vehicle dynamics due to the reachability problem.

5. 5. The method (900; 1000) according to any one of claims 1 to 4, wherein at least one edge corresponds to an edge of the track that intersects with the direction of travel of the vehicle or that is less than a threshold distance from the position of the vehicle.

6. The step of defining (900) a set of points of the track on which the vehicle is free to move comprises: Obtaining geographic data (901) relating to a geographic area containing a truck; Identifying (903) the geographic coordinates of the truck based on the acquired geographic data; Defining geographic coordinates as points of the track (905); A step (911) of defining the remaining geographic coordinates as points not belonging to the track; A method (900; 1000) according to any one of claims 1 to 5, comprising a step (913) of identifying at least one edge as a subset of points of the track that are adjacent to each other and adjacent to at least one point that does not belong to the track.

7. 7. The method (900; 1000) of claim 6, further comprising the step of adding to the set of points of the track coordinates of at least one additional area adjacent to an area of the set of points of the track, said additional area being suitable for the passage of a vehicle.

8. 8. The method (900; 1000) according to any one of claims 1 to 7, wherein the step (1013) of controlling the at least one actuator (10) to modify the dynamics of the vehicle comprises the step of calculating an exit trajectory from the intervention area based on the current position and dynamics of the vehicle and the distance of the vehicle from at least one edge, and performing an exit maneuver by controlling the at least one actuator (10) to follow the exit trajectory.

9. The exit orbit is calculated as the solution of: [0013] where t denotes time, T is the prediction period, f(x, u) denotes the vehicle dynamics, and d ｏｓｔ (x) denotes the distance between the vehicle and at least one margin, and d ｍｉｎ 9. The method (900; 1000) according to any one of claims 1 to 8, wherein x denotes an acceptable threshold distance value between the vehicle and at least one edge, x denotes the position of the vehicle in space, and u denotes at least one dynamic variable controllable by said at least one actuator.

10. A vehicle (V) comprising said control unit (30), said plurality of sensors (20) configured to measure quantities indicative of the dynamics of the vehicle, and said at least one actuator (10) configured to influence the dynamics of the vehicle, the plurality of sensors (20) and the at least one actuator (10) are connected to the control unit (30); A vehicle (V) wherein the control unit (30) is configured to perform a method (900; 1000) according to any one of claims 1 to 9.

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