METHOD OF CONTROL FOR REGENERATIVE BRAKING OF A ROAD VEHICLE WITH INDEPENDENT ELECTRIC MOTORS AND RELATED ROAD VEHICLE

Description

“ " METHOD AGAINST LL VEHICLE GENERATE OPERAKE MOTOR ROAD TT INDEPENDENT ROAD TIVO ROAD VEHICLE ” * % % IF TT HEAR LL TECHNICAL The present invention relates to a method of control for regenerative braking of a road vehicle with independent electric motors acting on at least two wheels, specifically on four wheels; the present invention concerns 1also a related road vehicle configured to carry out such method. THE FRONT RTE S onotimetodiperilrec upero , mediantelacosi dde tta regenerative braking, electric power in equipped vehicles of electric propulsion provided by batteries at high voltage. And in fact it is known that a part of the braking action, normally allocated to the effect of friction between a pad placed in contact with a disc by means of the action of a hydraulic force generated by the pilot (via pressure on a brake pedal) and assisted with various solutions techniques (brake boosters, hydraulic pumps), both supported by an electric braking applied by an electric motor placed in mechanical connection with the wheels (according to different known and not further detailed architectural schemes in the following). Generally, the energy recovered in this way from the the aforementioned electric motor mode is reintroduced inside of the high voltage battery, causing the effect of increase its state of charge (SOC) for future restitution in electric propulsion situations. According to the known solutions, 11 recovery of electricity is severely limited, especially in high-performance vehicles, so as not to exceed a default deceleration value (even if the vehicle was equipped with a propulsion system from absorption potential higher than the said wvalue default). Furthermore, 1the prior art solutions provide for a fixed distribution between front and rear axle, the which is not always optimal, limiting the energy recovery potential and therefore performance of the road vehicle. In addition, according to known type architectures, the energy recovery is sized to be fixed under standard braking conditions, the brakes are disabled under ABS braking conditions, providing, in these cases, to modulate the braking force exclusively through 11 l hydraulic / mechanical circuit that manages the brakes conventional. However, in high-performance vehicles 1''energy recoverable may be overabundant due to the important accelerations in play and can determine a a factor of absolute importance also in performance. And therefore the need for an improved system of electricity management, 1which becomes a important resource not only in terms of distribution of electric torque to the motors, but also in terms of electrical energy regeneration during braking. In fact, having a greater quantity of available energy, allows you to improve your performance on the track, for example and for example allowing the delivery of greater torque in acceleration for 11 completion of a race. DESCRIPTION OF THE INVENTION The object of the present invention is to provide a method regenerative braking control of a road vehicle with independent electric motors acting on at least two (in particular four) wheels and a related road vehicle, which are free from the drawbacks described above, both easy and economical to realize, and in particular allows you to maximize performance during 1la driving on a track without making the vehicle roadworthy unstable. According to the present invention, a method is provided regenerative braking control of a road vehicle with independent electric motors acting on at least two (in particular four) wheels and a related road vehicle, as claimed in the independent claims which follow, preferably, in any one of the following ways: claims directly or indirectly dependent from independent claims. The claims describe embodiments preferred embodiments of the present invention forming part integral to this description. BRIEF DESCRIPTION OF THE SIGNS The present invention will now be described with refer to the drawings nn and ss i, which are an example in the illustration non-limiting implementation, in which: — Figure 1 is a schematic and plan view of a road vehicle in accordance with the present invention and equipped with four separate and independent motors; — Figure 2 is a schematic diagram of a non restrictive form of implementation of the method in accordance with the present invention; — figures 3 and 4 show diagrams and phases of a braking of the vehicle in figure 1 in a straight line and in two different configurations, in figure 3 a light braking and in figure 4 an aggressive braking, in particular each of these figures shows a graph on the left relating to the trend of different accelerations with respect to at the speed, in the center a column diagram relating to the distribution of electric and / or hydraulic braking, and on the right a schematic illustration of the braking torque regenerative for each wheel in different phases of the same straight-line braking; — Figures 5 and 6 show diagrams and phases of a braking of the vehicle in figure 1 on a curve and in two different configurations, in figure 5 a light braking and in the figure 6 aggressive braking, especially each of these figures show on the left a graph relating to the trend of different accelerations with respect to the speed, alcentroundiagra mm aacolo nn a relative to lla distribution of electric and / or hydraulic braking, and right a 1schematic illustration of the braking torque regenerative for each wheel in different phases of the same braking on a curve. FORM TTU FAVORITE ACTION THE INVENTION In Figure 1, with the number 1 is indicated in its complete ss any road vehicle , in particular a car , for vv study ss 2 front wings axle 3 rear. Same numbers and reference letters in the figures identify the same elements or components check this function Within the scope of this description 11 term “second” component does not imply the presence of a “first” component. Such terms are 1in fact used as labels to improve clarity and are not to be understood in limiting mode. The items and features illustrated in the various preferred embodiments, including drawings, can be combined with each other without exiting from the scope of protection of the present application as described following. It is specified that following this description, expressions such as “above”, “below”, “ previously ” , “ posteriorly ” are also useful with reference to conditions of normal advancement of the vehicle 1 roadway along the normal direction D of advances chin. As illustrated in the non-limiting form of implementation of Figure 1, it is also possible to define: - a longitudinal ss and X , solidaritywithvehicle 1 and arranged , unused , outside the abnormal law direction D of advance of vehicle 1; - a transverse ss and Y , solidarityvehicle 1 and arranged , unused , or zz ontaleeorthogonal to the X axis ; and - a vertical ss and Z , solidarityvehicle 1 arranged , in use, vertical and orthogonal to the X, Y axes. The vehicle 1 road includes four wheels 4, 5 divided into pairs between 1anterior 2nd axis and 1st 3rd axle rear. In particular, of the four wheels 4, 5, at least two, specifically all four, are driven wheels. You in other words , the vehicle 1 includes 4 front wheels (engines), front axle 2 components, and two wheels 5 rear (also engines), front end 3 posterior. Specifically, vehicle 1 could be at front wheel drive , or vv eroconsole 4 front wheels drivetrains , rear wheel drive , or vve roconlewheel 5 rear wheel drive , or all wheel drive , including wheels , 5 engines , as 1 unlimited form of implementation of the attached figures. The vehicle <comprende inoltre un sistema 6 di propulsion, which in turn includes two or four electric 7 engines (according to wheel number 4, 5 engines and to the typology of direct or indirect actuation - through differential), <ciascuno dei quali è connesso ad una respective wheel 4, 5 by an appropriate drive system which allows the torque exerted by each wheel to be varied 4, 5 independently and adjustable according to logic default . The telescope , according to some form of action not limited, there are respective 7 electric motors per wheel , whilesecondfor another average non-limiting, there is an active differential (known and therefore not further detailed below) that allows you to deliver (and receive) diversify torque to wheel of oneself axle 3 or 4. In particular, according to a preferred but not limited cheese tt uation , each wheel 4 , 5 is operable rotation by a respective 7 electric motor to it connected. The 7 electric motors are mechanically coupled to the wheels 4, 5 and are configured to deliver or receive torque drive train with wheels 4, 5 and 6, depending on the function driving or generating force which respectively exert in acceleration and braking. Each wheel 4 or 5 is mechanically connected to a chassis of the road vehicle 1 by means of a suspension 10 (partially illustrated in Figure 1), which is equipped with an electronically controlled shock absorber 11, or equipped with an electric actuator that allows vary (i.e. increase or decrease) the damping of the electronically controlled shock absorber 11. As a example, the electric actuator of each shock absorber 11 electronically controlled may include one or more solenoid valves that modulate the size of holes oil passage inside the shock absorber 11 a electronic control, or it may include a fluid magneto-rheological which modifies its physical properties in function of an applied magnetic field. In addition, 11 vehicle 1 includes a circuitry 8 control electronics, which includes one or more units 9 against the calculation (“ECU”) which, among other things, rule 1l the behavior of the road vehicle both in straight, both when travelling around a curve intervening, as better described below, on the couple generated by 7 electric motors thanks to 4, 5 wheels deceleration motors. Physically, the circuitry 8 of control can be composed of a single device or from multiple devices that are separate and communicating through the CAN network of the road vehicle 1. Advantageously, the 8 electronic circuitry of control is configured to estimate, for each wheel 4, 5 drive, independently of the other wheels 4, 5 drive, a respective G-factor of grip on the ground travelled by the road vehicle 1. In particular, the grip factor G on the ground is calculated according to known methods and therefore not further detailed below. This G factor of adhesion could be estimated, whether detected according to known techniques, such as described in the application for Italian patent 102021000020948 filed by the same Applicant. Furthermore, the 8 electronic circuitry is configured to defineoridetect , perwheel 4 , 5 motor , regardless of the other wheel 4 , 5 engines , a respective load Fz vertical agent on it. You particularly, 11 load Fz is also defined or detected by means of noted techniques and ©therefore not further detailed below (ie measuring the load, ie the force, Fz with special sensors or estimating it through vehicle action mode 1 road ) , as an example described in Italian patent application filed by the Applicant herself. The electronic 8 circuitry is also configured for process , perwheel 4 , 5 drive , one MRT value of a maximum braking capacity (regenerative, i.e. maximum regenerative torque) as a function of at least the respective adhesion factor G and the respective vertical load Fz. In particular, the maximum braking capacity is determined according to known methods and therefore not further described in the following. Vehicle 1 also comprises a system 12 of DD data collection, which is connected to circuitry 8 control and is configured to detect a plurality of DD data on vehicle dynamics. In particular, 1 DD data detected by the 12 detection system include at least are at least the speed Vx (longitudinal) of vehicle 1, the which is preferably but not limited to detected via speed sensors arranged in correspondence of wheels 4, 5; the driver's DR requests, for example how much and how an accelerator pedal or brake or turn 11 steering wheel; and the accelerations Ax longitudinal and transverse Ay, for example detected by one or more inertial units of measurement (known in themselves and therefore not more detailed), of the road vehicle 1. The road vehicle 1 also includes a system 13 of braking, comprising at least one element 1 4 braking system that can be activated by the driver to request a braking, in particular a brake pedal. In detail, the braking system 14 is connected to circuitry 8 of control and is configured to be controlled by it. Advantageously, the control circuitry 8 is also configured to control the braking system 13, following a request to brake by the driver via braking element 14, to operate under braking electric generative, delivering a respective first torque and BT braking (electric), each motor 7 electric function of the plurality of dynamic DD data and their respective MRT values ​​of maximum braking capacity (for each wheel), so as to generate recovered electricity. In other words, for example, when the driver presses the pedal 15 brake, the control circuitry 8, in particular 1 ' unit 9 control ll or , controls braking each of the 7 engines electric with a respective eBT electric braking torque (or countermotive), thanks to which it is possible generate, using 7 electric motors as generators, energy and energy to recover, or to be recovered by converting the kinetic energy of the 4, 5-wheel drive in energy electric during braking. Finally, the electronic control circuitry 8 is configured to store the aforementioned electrical energy of recovery generated by the regenerative braking of each wheel 4, 5 in a 16 system (common between wheels 4, 5) of storage of vehicular electrical energy, in particular in a vehicular battery pack 17. In other words, 1'energy generated under braking thanks to the 7 electric motors converges in a main battery pack 17 of the road vehicle 1, for a subsequent use during acceleration, so as to increase performance, for example when exiting from a curve on a track. Advantageously but not limited to, the 13 system braking system also includes a hydraulic unit, and brakes mechanical, controlled by hydraulic unit 18. In detail, control circuitry 8 is configured to control the braking system 1 3 so as to operate, with the aid of the regenerative braking generated by the 7 electric motors, i.e. in addition to the respective first braking eBT pair, the hydraulic unit 18 to exert a second hBT torque braking on each wheel 4, 5. In accordance with a further aspect of this invention, a control method is provided for a regenerative braking of a road vehicle driven by a driver. In addition but not limited to, the vehicle road, especially the control circuitry 8, is configured / scheduled to perform the following method described. The method includes the stages of: - estimate , through circuit 8 opposite , in detail through at least one of the 9 control units or calculation , percussion wheel 4 , 5 engine , regardless from the other wheel 4 , 5 engines , 1 respective G di adherence to soil traveled by vehicle 1 roadway; - define or detect, via circuitry 8 of control, particularly through at least one of the units 9 against the calculator , wheelchair , 4 , 5 engine , regardless of the otherwheel 4 , 5 engines , the respective load Fz vertical agent on it; - process, via control circuitry 8, in particular through at least one of the 9 control units calculator , wheel 4 , 5 engine , MRT value of the maximum braking capacity in function of at least the respective adhesion factor G and respective load Fz vertical; - detect , via 11 system 1 2 processing DD data , a plurality of DD data on vehicle dynamics ; - command , through circuitry 8 opposite , in particular through at least one of the 9 control units calculus , system 1 3 braking , following request for braking by the driver (e.g. through brake pedal 1 5 ) , to operate unbraked generating electricity, delivering a respective first pair eBT braking, each 7 electric motor depending on the plurality of dynamic DD data and the respective MRT values ​​of maximum braking capacity, cosl to generate energy recovery electrical; - i mm ag add 1'' recovery electrical energy generated by the regenerative braking of each wheel 4, 5 in the accumulation 17 system. P referably handles them mitotically , during the phase remote control system 1 3 differential braking , at least marked 4 ' , 5 " right and one wheel 4 ' ' , 5 ' ' left of the same s s e front axle 2 or rear axle 3 are controlled in a independent between them, and distributing percentages between them and ss and braking in a differentiated way. In other words, the first pair eBT electric braking controlled to wheel 47, 57 right differs from the first braking eBT pair electric driven to the 4rr, 577 left wheel. Consistently, the electrical energy regenerated by the wheel 4', 5' right with respect to that generated by the wheel 4'', 5'7" left. Regardless of this difference, 1" electrical energy is preferably stored in the 16 storage system to be delivered to any of the 7 electric motors. Alcunipreferiticasin omnilimitations , during a curve 19 (as schematically illustrated in Figures 5 and 6 ) , which will be on the rightwheel 4 ' , 5 ' wheel 4 ' ' , 5 left of a same front axle 2 or rear 3 that is outside curve 19 (in the case of Figs 5 and 6 , between tt andosidione curve 1 9 left , wheel outer are the wheels 4', 5' right), delivers a first pair and greater braking BT with respect to the wheel (in the case of figures 5 and 6, being a curve 19 on the left, the sunroof wheel 4 ' ' , 5 " ' left ) of the same at axes 2 , 3 , the internode of the curve I nalt ernative or in addition, during 1the phase of control the braking system, the wheels 4 (or 4 'e 477) of the front axle 2 and wheels 5 (i.e. 5' and 5'') of the rear axle 3 are controlled in a manner independent of each other, distributing the braking in a way differentiated, for example in percentage, between 1st axle and 2nd axle front and rear axle 3. In other words, the first eBT electric braking torque controlled to 4 wheels anterior ri o ri differs from the first braking eBT pair electric driven to the 5 rear wheels. Consistently, differs the electrical energy generated by the wheels 4 front than that generated by the 5 wheels posterior. Regardless of this difference, the energy electricity is preferably stored in system 16 of accrual to be assignable to any of the engines 7 electrical. In the non-limiting forms of implementation of the figures 5 and 6 to the legate , circuit 8 against the commander differentiated mode is 1'arrangement of the first pair eBT electric brake between axle 2 front and 1axle 3 rear, four-wheel 4 ' , 5 ' right-wheel 4 ' 7 , 5'7 lefty. Beneficially but not limitingly, and as illustrated in the right sections of Figures 3 to 6, the respective eBT braking torque applied to at least one wheel 4 , 5 ( unparticularly in elections 4 , 5 , excluding the above for axle torque 2, 3) is dynamically varying in the time ( during 1 brake , or vv erroneouslythe driver requires braking via the pedal). In particular, the eBT electric braking copy and variable refresh rates above 3 Hz, in especially above 5 Hz; more specifically with refresh rates of 10 Hz or higher. Advantageously but not limitingly, therefore, 1la respective first eBT braking torque delivered by a wheel 5 (or rather 5 ", 5 "'), in particular both wheels 5, 5 ', 57, of the rear axle 3 remains constant O preferably increases as time passes during the braking, as the speed Vx (longitudinal) of the road vehicle 1 is reduced. Preferably but non-limitatively, the respective first eBT braking torque delivered by wheel 4 (i.e. 4', 4 '' ), in particular from both wheels 4 , 4 ' , 4 ' 7 " , of the front axle 2 remains constant or preferably decreases as time passes during braking, gradually that the speed Vx of road vehicle 1 is reduced. According to some preferred forms of implementation, limiting, as illustrated in the attached figures, the method It also includes a control phase of the system 14 braking in order to operate, to assist braking regenerative, in addition to the respective first pair eBT braking, 1'unit 18 hydraulic to exercise the second co pp iam BT frenantesuciascunaruo ta 4 , 5 , in particular at least partially simultaneously with the first pair braking. According to some non-limiting and non-binding forms of implementation illustrated, above a certain speed Vx longitudinal of a certain braking request from the driver, the first eBT braking torque is exerted in delay with respect to the second braking mBT pair, which springs into action first. In particular, the second mBT braking torque delivered from the hydraulic unit 18 is uniform for each wheel 4, 5 of front axle 2 or axle 3 respectively rear. In other words, wheels on the same axle 2, 3 are braked in the same way by their respective brakes mechanics. The limited number of preferable cases, 1 the second one mBT braking torque delivered by hydraulic unit 18 is different between the mBT pair of wheels 4 of the front axle 2 and the mBT pair of 4 wheels on rear axle 3. Advantageously but not limitingly, the circuitry 8 control is configured to perform the method described in this description. In accordance with what was previously said, therefore, the braking potential of each individual wheel 4, 5 is a function of the adhesion factor G, of the applied vertical load Fz on wheel 4, 5 (or on the respective tire) as well as of the possible presence of lateral commitment required by the tire itself (the possible acceleration Ay). It follows that under dynamic conditions of load transfer, such as braking on a straight line (where there is a load transfer towards the front axle 2) or braking on a curve (where you have a second chance again load transfer to front axle 1, but with lateral force demand on the tires of wheels 4, 5, to limit the braking capacity itself), the 8 control circuitry commands the 7 electric motors and the hydraulic unit 18 dynamically adjusting the quota separately, or rather the percentage, of hydraulic braking inspected electric braking, i.e. of the second mBT torque compared to the first eBT pair, based on the conditions punctual of each single wheel 4, 5. Therefore, according to the above forms of implementation described or a combination thereof, having available an estimator (of known type) of the overall capacity braking of each wheel 4, 5 is therefore possible (in the absence (ABS control) to better distribute the action braking (calibrating the eBT and mBT torques) and maximizing the energy recovery (if a fixed distribution in fact was excessive for a single wheel 4, 5, its reduction or cancellation should be made on the entire axle 2, 3 braking, losing the contribution possible of the other wheel of the same axle 2, 3). In the non-limiting form of implementation of the figure 2, and a portion of the schematically illustrated control circuitry 8, comprising two control units 9 control or calculation. Following the flow of information (indicated by arrows), the first control unit 9 receives input a BC signal relating to the conditions (model, size and status) of the battery pack 17 (and its limits) and an EMC signal, relating to the conditions (model, size and status) of the 7 electric motors (and their 1 limits). At the entrance signal light, unit 9 of control processes, for each wheel 4, 5 (i.e. four values) the maximum electric MRT braking capacity, which It is preferably expressed as maximum braking torque deliverable by 7 electric motors taking into account also the battery pack 17. The four maximum braking capacity MRT values are given as input to the second control unit 9 (which physically can also coincide with the first), together to the dynamic DD data of the road vehicle 1 and to a signal PFS related to the 1 limitations imposed by security functional of the road vehicle 1 (the so-called Automotive functional safety or FuSa, defined for example by ISO 26262). In addition to these signals, it is considered furthermore the G factor of adhesion calculated or estimated as described above and as is known. In light of these signals in input, the control unit 9 processes the distribution of the regenerative brakes on wheels 4, 5, or vve rola combination of the respective first eBT pairs and possibly second mBT pairs, if necessary, for more aggressive braking. In the non-limiting forms of implementation of the figures _20_ From 3 to 6 three different sections are illustrated a), b) and c). In section a) a graph is shown having as x-axis the longitudinal velocity Vx in km / h as the ordinate axis the longitudinal acceleration Ax. The following profiles are shown within this graph: AxXPFS (i.e. the maximum acceleration related to the PFS signal relating to the 1 F u S a limits, MBC (or rather the 1 'acceleration maximum linked to the BC signal relating to the 1 limits per package battery 1 7), AXEM (or 1 the maximum acceleration linked to the EM signal relating to electric motors 7), AxS (i.e. 1"maximum acceleration linked to the G signal relative to the adhesion factor), AxXR (i.e. the acceleration required from the driver DR via the brake pedal 14) and MRT (i.e. the maximum braking capacity described above). To these profiles, the areas are added at the end of the graph (therefore the integrals) underlying that define the first electric braking eBT torque and any (in the figures from 4 to 6) second pair mBT hydraulic braking. In section D b), it is instead illustrated, in a way that the imitative, using a column chart with the axis of the abscissas the longitudinal velocity Vx and as axis of the sort the percentage of torque distribution braking, the relative distribution of braking torques electric and hydraulic (the latter fixed and constant) between wheels 4, 5, depending on the vehicle dynamics. _21_ Finally, in section C) it is schematically illustrated the road vehicle 1 in two different intervals of subsequent time, respectively in an initial phase braking at 140 km / h and in a final phase of braking at 40 km / h. As indicated above, the implementation forms of the figures 3 to 6 illustrate examples of implementation limiting . Specifically , the percent ual distribution of braking torque follows default logic depending on the setup of the propulsion system. For example, in general, if there is only one electrical axis, the percentage distribution of the torque electric brake is adjustable independently between wheels 4 ', 5 ' right 4 ' "", 5 ' " ' ' left (anterior rear whether axle 6 or 7). This distribution d diversified of the braking torque can be eroded ta both via a single 7 electric motor connected to a active differential, in turn connected to the wheels, or through two electric motors , one each wheel 4 , 5 dinoste ss or axle. For example, in addition, in the case where there are both electrical 7 , percentage distribution electric braking torque is adjustable independently between wheel 4 ' , 5 ' right wheel 4 ' ' ' , 5 ' ' left (anterior posterior to either axle 6 or 7) of both axles 6, _22_ 7. This diversified braking torque distribution pud be powered either by a single electric 7 engine for each power axle connected to a differential active , low voltage attached to the wheels , or retramite four respective 7-electric motors, one for each wheel 4, 5. In this way, it is possible to adjust independently be the relative percentage distribution between wheels of one same ss or ss ale, both between the two different axles 6,7, so optimize / maximize the recovery of electrical energy in different situations (straight lines, curves, ascent, descent, sloped road or a combination of these). By way of example, they will now be described peculiarities of each non-limiting situation illustrated in figures 3 to 6. In figure 3, you can see how the acceleration AxR braking force required by the DR driver is not very marked. Therefore, in this case, braking is managed by the circuitry 8 controlled entirely by electric motors, 7 which are activated during braking, delivering the respective first braking eBT pair. As can be seen from this figure, despite the amount of braking eBT torque ele tt recharge cost (see section 1 )), the distribution is variable over time, during braking. You specifically, it has decreased with ibuto inhibitor he recodes the previous axis 2 , incrementing , preferably complimentary, that of the axle 3 rear. In this case, dealing with a situation of straight line, the contribution is diversified between an assault the other , varying a little , but both wheels belonging to the same axle. Specifically, it seems clear that the above variations are from consider themselves in relative terms with respect to their respective previous value of the braking torque percentage of the respect to wheel 4, 5 or axle 6, 7. In the non-limiting form of implementation of the figure 4, instead, we can notice how the acceleration AxXR braking requested by the DR driver is particularly marked, in particular up to touching the acceleration AxS limit of the G-factor of adhesion. In this case, unlike the previous, control circuitry 8 manages braking partially through the 7 electric motors, which are activated under braking, each delivering the respective first gear eBT braking torque, and partially via unit 18 hydraulics and the 19 mechanical brakes (which brake in a uniform between wheels 4, 5, or more than ffe renziatiinmodo fixed per axle). As can be seen from this figure, the quantity of electric braking torque eBT is this time variable in a first section and constant in a second section (see the section (a) ). Furthermore, as can be seen from sections (b) and (c) (thanks to the illustrative arrows) the distribution is also _24_ in this case variable over time, during braking. In in particular, the braking contribution remains constant electric front axle 2, the contribution of the hydraulic unit 18 and the brakes 19 mechanical, therefore of the mechanical mBT couple, increasing complementary to the electrical contribution of axle 3 rear, 11 which earns exactly how much is given away from hydraulic unit 18. In particular, it appears clear that, alsoin this case , variations above category , cyanoda consider themselves in relative terms with respect to their respective previous value of the braking torque percentage of the respectively shown in Tables 4 , 5 and Tables 6 , 7 . In this case , non limitingly, dealing with a situation of straight line, the contribution is diversified between an assault the other , varying a little , but both wheels belonging to the same axle. Differently it is 11 case of Figures 5 and 6, which show a variation of the distribution of the first eBT electric braking torque also between wheels 4', 4'7 and 57, 5'7" belonging to the same axis. In these cases, as in the former, control circuitry 8 handles 1la braking partially through the 7 electric motors, which are operated in braking by eliciting for each the respective first pair eBT braking, and partially via the hydraulic unit 18 and the mechanical brakes 19 (which brake _25_ 4 , 5 , differentiated values fixedly for assault). As is evident from the non-limiting form of actuation of Figure 5, the amount of eBT electric braking torque is variable in a first stroke and constant in a second between tt or ( switchtosection )) . Furthermore , as well as sections b) c) (thanks to the illustrative arrow) the distribution is also in this case time-varying, duringrestrain . In particular, 1 contribution-withholding electric of the 4', 5' outer wheels is greater than the contribution of the 4' 7, 5 '' wheels inside the curve. Furthermore , if initially there is also a mechanical contribution given by the second braking mBT couple, therefore by unit 18 hydraulics 18; during braking this contribution is reduced to the point of disappearing, while simultaneously increasing the electricity contribution, 11 which one earns exactly how much released by hydraulic unit 18. In particular, it is increased contribution provided by rear axle 3 and reduced the —contribution of the front axle 2. In particular, it appears clear that, even in this case, the variations indicated above, should be considered in terms relative to the respective previous value of the percentage of braking torque of the respective wheel 4.5 o a ss wing 6 , 7 . In this case , without limitation , between tt andosi of a curve situation, the contribution is diversified _26_ each ss wings 1 l ' the other , varying a little bit , and also between the two wheels belonging to the same axle, also varying over time. As is evident from the non-limiting form of actuation of Figure 6, the amount of eBT electric braking torque is variable in a short first stroke and constant in a second between tt or ( switchtosection )) . Furthermore , as well as sections b) c) (thanks to the illustrative arrow) the distribution is also in this case time-varying, duringrestrain . In particular, 1 contribution-withholding electrical of the 4', 5' outer wheels is greater than the contributed by the 4 ' 7 , 5 '' internal curve Furthermore , there is also a mechanical contribution given by the second couple braking mBT; therefore, from unit 18 plumbing 18; During the braking such contribution decreases slightly, increasing additionally 11 electrical contribution, which earns exactly how much is given by the 18 hydraulic unit. 1In particularly, the contribution provided by the assault is reduced 3 rear and increased 11 axle contribution anterior. In particular, it seems clear that, even in this case , leveraging category , or to be considered terms relative to their respective previous value of the percentage of the braking torque of the respective wheel 4.5 or assault 6, 7. In this case, not limitingly, between tt and oxidation situation urva , is diversified _27_ the contribution of each other is the contribution of the other , varying as well over time, and also between the two wheels belonging to the same to ss wing , varying also ' and ss at the same time Therefore, it is also possible to experimentally define different deployment strategies of the eBT pair and the mBT couple, as a function of what are the aforementioned factors price under consideration. Although the above invention makes a particular re referring to a well-precise implementation example, it it is not to be considered limited to this example of implementation, all those variations and modifications falling within its scope or exemplifications covered by the appended claims, such as a different distribution strategy of the torque, a lower number of drive wheels, etc. The method and 11 vehicles described above present numerous advantages. First, the variable distribution of action braking performed by electric motors on each individual wheel, depending on the dynamic situation, but at most improves the recovery of electrical energy during braking, also avoiding penalizing the control action in dynamic situation. Finally, the control method described above is simple and economical implementation in a road vehicle equipped with a motor for each drive wheel, as it does not require an addition of any physical component and is completely realizable via software in vehicles equipped with at least two electric motors. And It is important to note that the control method described above does not requires neither a high computing capacity nor a large amount of memory and therefore its implementation is possible in a unit of note control without the need for updates or upgrades. LIST OF REFERENCE NUMBERS OF THE FIGURES 1 road vehicle 2 front axle 3 rear axle 4 front wheels 4th right front wheel 4'' left front wheel 5 rear wheels 5 right rear wheel 57 left rear wheel 6 propulsion system 7 electric motors 8 control circuitry 9 control or calculation units 10 suspension 11 shock absorber 12 detection system 13 braking system 14 braking element 15 brake pedal 16 storage system 17 battery pack hydraulic unit 19 mechanical brakes A x longitudinal acceleration AX x EM maximum EMC acceleration AXPFES maximum acceleration PFS A xXR requested A x S stability transversal battery operating conditions dynamic data driver first electric braking pair condition of electric motors vertical load adhesion factor maximum acceleration BC second mechanical braking pair maximum braking capacity priority functions and safety limitation longitudinal speed axis ass and ass and

Claims

1) Control method for regenerative braking of a road vehicle (1) driven by a driver (DR); the road vehicle (1) comprising four wheels (4, 5), of which two or four wheels (4, 5) are driving wheels, arranged in pairs on a front axle (2) and / or a rear axle (3), each of which can be rotated by a respective electric motor (7) connected to it; the method comprises the phases of: - estimating, for each driving wheel (4, 5), independently of the other driving wheel(s) (4, 5), a respective factor (G) of adhesion to the ground travelled by the road vehicle (1); - defining or detecting, for each driving wheel (4, 5), independently of the other driving wheel(s) (4, 5), a respective vertical load (Fz) acting on it; - develop, for each driving wheel (4, 5), a value of a maximum braking capacity (MRT) as a function at least of the respective grip factor (G) and the respective vertical load (Fz);- detect a plurality of data on vehicle dynamics; - control a braking system (13), following a braking request from the driver (DR), to activate in generative electric braking, supplying a respective first braking torque (eBT), each driving wheel and therefore the respective electric motor (7), as a function of the plurality of dynamic data (DD) and the respective maximum braking capacity values ​​(MRT), so as to generate recuperative electric energy; - store the recuperative electric energy generated by the regenerative braking of each driving wheel (4, 5) in a vehicle electric energy storage system (16).; 2) Method according to claim 1, wherein during the phase of controlling the braking system (13), at least one right wheel (4, 5) and one left wheel (4, 5) driving the same front and / or rear axle (2) are controlled independently of each other, distributing the braking between them in a differentiated manner. 3) Method according to claim 2, wherein during a curve, the one between the right driving wheel (4, 5) and the left driving wheel (4, 5) of the same front and / or rear axle (2) which is on the outside of the curve, delivers a first braking torque (eBT) greater than the driving wheel (4, 5) of the same axle which is on the inside of the curve. 4) Method according to any of the preceding claims, wherein the drive wheels (4, 5) are four, and wherein during the phase of controlling the braking system (13), the wheels (4, 5) of the front axle (2) and the wheels (4, 5) of the rear axle (3) are controlled independently of each other, distributing the regenerative braking in a differentiated manner between the front axle (2) and the rear axle (3). 5) A method according to any of the preceding claims, wherein the respective braking torque delivered by a wheel (4, 5) is dynamically variable over time, in particular with update frequencies greater than 5 Hz; more particularly with update frequencies equal to or greater than 10 Hz. 6) A method according to claim 5, wherein the respective first braking torque (eBT) delivered by a wheel (4, 5), in particular by both wheels (4, 5), of the rear axle (3) remains constant or increases relative to its previous value as time passes during braking, as the speed of the road vehicle (1) decreases. 7) A method according to any of claims 5 or 6, wherein the respective first braking torque (eBT) delivered by a wheel (4, 5), in particular by both wheels (4, 5), of the front axle (2) remains constant or decreases relative to its previous value over time during braking, as the speed of the road vehicle (1) is reduced. 8) Method according to any of the preceding claims, and comprising the step of controlling the braking system (13) so as to actuate, in aid of regenerative braking, in addition to the respective first braking torque (eBT), a hydraulic unit (18) for exerting a second braking torque (mBT) on each wheel (4, 5). 9) Method according to claim 8, wherein the second braking torque (mBT) delivered by the hydraulic unit (18) is uniform for each wheel (4, 5) of the front axle (2) or the rear axle (3) respectively. 10) Method according to claim 8 or 9, wherein the second braking torque (mBT) delivered by the hydraulic unit (18) is different between the pair of wheels (4, 5) of the front axle and the pair of wheels (4, 5) of the rear axle. 11) A method according to any of claims 8 to 10, wherein the second braking torque (mBT) remains constant or decreases over time during braking, as the speed of the road vehicle (1) is reduced. 12) Electric road vehicle (1) comprising: - a front axle (2) and a rear axle (3); - four wheels (4, 5), of which two or four driving wheels (4, 5) arranged in pairs on a front axle (2) and / or a rear axle (3); - a propulsion system (6) comprising two or four electric motors (7), or alternatively one or two electric motors connected to active differentials each connected to two driving wheels (4, 5), each of the electric motors (7) being connected to a respective wheel (4, 5) or to two wheels in the case of the presence of active differentials; wherein each wheel (4, 5) can be rotated by the respective electric motor (7) connected to it; - an electronic control circuitry, which is configured to: o estimate, for each driving wheel (4, 5), independently of the other driving wheels (4, 5), a respective factor (G) of grip on the ground travelled by the road vehicle (1);o define or detect, for each driving wheel (4, 5), independently of the other driving wheels (4, 5), a respective vertical load (Fz) acting on it; o process, for each driving wheel (4, 5), a value of a maximum braking capacity (MRT) as a function of at least the respective grip factor (G) and the respective vertical load (Fz); - a data collection system (12), connected to the control circuitry (8) and configured to detect a plurality of data on vehicle dynamics; - a braking system (13), comprising in turn at least one braking element (14) that can be operated by the driver (DR) to request braking, in particular a pedal; the braking system (13) being connected to the control circuitry (8) and configured to be controlled by it;wherein the control circuitry (8) is further configured to control the braking system (13), following a braking request from the driver (DR) via the braking element (14), to operate in generative electric braking, delivering a respective first braking torque (eBT), each driving wheel and hence the respective electric motor (7), as a function of the plurality of dynamic data (DD) and the respective maximum braking capacity (MRT) values, so as to generate recuperative electric energy; and to store the recuperative electric energy generated by the regenerative braking of each wheel (4, 5) in a vehicular electric energy storage system (16).; 13) Road vehicle (1) according to claim 12, wherein the control circuitry (8) is configured to carry out the method according to any of claims 1 to 7. 14) Road vehicle (1) according to claim 12, wherein the braking system (13) also comprises a hydraulic unit (18), and mechanical brakes, controlled by the hydraulic unit (18); wherein the control circuitry (8) is configured to control the braking system (13) so as to actuate, in aid of regenerative braking, in addition to the respective first braking torque (eBT), the hydraulic unit (18) to exert a second braking torque (mBT) on each wheel (4, 5). 15) A road vehicle (1) according to claim 14, wherein the control circuitry (8) is configured to carry out the method according to any one of claims 8 to 11.