Abstract:
The invention relates to a four wheel drive hybrid vehicle provided with at least one power train on each wheel set, a first power train ( 1 ) including at least one heat engine, a second power train ( 2 ) including at least one electric machine, the vehicle also being provided with a friction braking system on each drive wheel and sensor ( 7 ). The control system includes: a means ( 9 ) for distributing a braking request between the friction braking system and at least one electric machine from a power train, said electric machine being capable of producing a resisting torque; a torque instruction modulation means ( 10 ) for modulating torque instructions to braking systems and power trains based on signals coming from the sensors; and a power train control means ( 8 ); the distribution means ( 9 ), the torque instruction modulation means ( 10 ), and the power train control means ( 8 ) being capable of dynamically interacting so as to output torque commands to the power trains and to the friction braking systems with a view to promoting the stability of the vehicle.

Description:
BACKGROUND 
     The present invention relates to the field of motor vehicle control systems and, more particularly, to control systems for powertrains and braking devices for hybrid motor vehicles. 
     Vehicles incorporating electrical machines to propel them are increasingly prized for their quietness and the fuel savings they have to offer. 
     However, co-ordinating these electrical machines with one another or with other propulsion systems entails advanced control electronics. Moreover, as the braking functions can be provided partly by operating these electrical machines as generators, it is important also to control the braking aspect. 
     BRIEF SUMMARY 
     Hence, there is a need for a control system capable of managing the integration of the electrical machines into the propulsion and braking functions of a motor vehicle. 
     The subject of the present invention is a system and a method for controlling the electrical machines of a four-wheel drive vehicle. 
     Another subject of the invention is a system and a method for controlling the electrical machines of a four-wheel drive vehicle used as a braking system. 
     One aspect of the invention defines a system for controlling a motor vehicle of the four-wheel drive hybrid propulsion type equipped with at least one powertrain on each wheelset, a first powertrain comprising at least one combustion engine, a second powertrain comprising at least one electrical machine, the vehicle also being equipped with a friction braking system on each of the driven wheels and with sensors. 
     The control system comprises a distributing means for distributing a braking request between the friction braking system and at least one electrical machine of a powertrain, said electrical machine being capable of delivering a resistive torque,
         a modulating means for modulating the torque setpoints intended for the braking systems and for the powertrains as a function of the signals from the sensors,   a control means for controlling the powertrains,   the brake force distributing means, the torque setpoint modulating means and the powertrain control means being capable of dynamically interacting in order to issue torque commands to the powertrains and to the friction braking systems in order to promote the stability of the vehicle.       

     The control system may be applied to a vehicle equipped with driver assist means. The means of determining the stability may comprise a braking co-ordinating device capable of taking into consideration in a concerted and prioritized manner the signals from the driver assist means. 
     The powertrain control means may further comprise an engine torque co-ordinating device capable of taking into consideration in a concerted and prioritized manner the signals from the driver assist means, from the sensors and from the means of determining the stability of the vehicle. 
     The first powertrain may be connected to the front wheelset and the second powertrain may be connected to the rear wheelset, the torque setpoint modulating means then being capable of limiting the recuperative braking of the rear wheelset in order to promote the grip of said rear wheelset. 
     The means of determining the stability of the vehicle may comprise a control means able to exert an influence on the friction braking system which does not generate force torque but which does reduce the response time for a later demand. 
     Another aspect of the invention defines a method for controlling a motor vehicle of the four-wheel drive hybrid propulsion type equipped with at least one powertrain on each wheelset, a first powertrain comprising at least one combustion engine, a second powertrain comprising at least one electrical machine. The control method comprises steps during which:
         the driver braking request is distributed between the friction braking and the recuperative braking of the electrical machines of the powertrains according to the estimated speed of the vehicle, to the depression of the brake pedal and to the angle through which the steered wheels are turned,   ranges of recuperative braking torque supplied by the electrical machines of a powertrain are determined for the front wheelset, for the rear wheelset, and under static and dynamic conditions;   braking torques for each friction braking device are determined as a function of the stability of the vehicle,   recuperative braking torques for the front wheelset under static conditions, for the rear wheelset under static conditions, for the front wheelset under dynamic conditions and for the front wheelset under dynamic conditions are determined within the ranges of recuperative braking torque previously determined, the braking torques being determined as a function of the friction braking torques of each friction braking device.       

     Furthermore, the control method may be applied to a vehicle equipped with driver assist means. The taking into consideration of the braking torque setpoints from the driver assist means may then be prioritized in order to determine braking setpoints that will promote the stability of the vehicle. 
     The recuperative braking on the rear wheelset may be limited in order to promote the stability of the vehicle. 
     A minimum friction braking torque setpoint may also be determined in order to increase the speed of response of the braking devices in case of a braking request involving significant use of the friction braking. 
     A range of torques supplied by the powertrains may be determined as a function of the torque requests on the part of the driver and of the driver assist means. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects, features and advantages will become apparent from reading the following description given solely by way of nonlimiting example and made with reference to the accompanying drawings in which: 
         FIG. 1  illustrates the main elements involved in a vehicle equipped with a control system; and 
         FIG. 2  illustrates the main elements involved in a control system; and 
         FIG. 3  illustrates the main elements involved in an engine torque coordinating device; and 
         FIGS. 4 and 5  illustrate the main elements involved in a braking coordinating device. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a motor vehicle termed VEH comprising the main parts of a control system. The vehicle VEH comprises a front powertrain  1  connected to a front wheelset  3   a ;  3   b  via an axle  21  and a rear powertrain  2  connected to a rear wheelset  4   a ;  4   b  by an axle  22 . The wheel  3   a  is equipped with a braking device  5   a , the wheel  3   b  with a device  5   b , the wheel  4   a  with a device  6   a  and the wheel  4   b  with a device  6   b.    
     An electronic control unit identified by the reference UCE controls the braking devices  5   a ,  5   b ,  6   a  and  6   b  via the connections  12 ,  13 ,  14  and  15 . The electronic control unit UCE also controls the front  1  and rear  2  powertrains via the links  19  and  20  respectively. 
     The electronic control unit UCE is connected to sensors by connections  7   a ,  7   b ,  7   c ,  7   d ,  7   e  and  7   f . The electronic control unit UCE comprises a means  8  of controlling the powertrains, a means  9  of distributing a braking request, a means  10  of modulating the torque setpoints and a system  11  for controlling the braking devices. The powertrain control means  8  is connected at output by the connection  19  to the front powertrain  1 , by the connection  20  to the rear powertrain  2 . The braking device control system  11  is connected by the connection  12  and by the connections  13 ,  14  and  15  to the braking devices  5   a ,  5   b ,  6   a  and  6   b.    
     The means  9  for distributing a braking request and the means  10  for modulating the torque setpoints intended for the braking systems and for the powertrains are interconnected by the connections  18   a ,  18   b  and  18   c . The brake request distribution means  9  is connected to the powertrain control means  8  by the connections  17   a ,  17   b ,  17   c ,  17   d ,  17   e ,  17   f ,  17   g ,  17   h  and  17   i . The means  10  for modulating the torque setpoints intended for the braking systems and for the powertrains is connected to the powertrain control means  8  by the connections  16   a ,  16   b  and  16   c . The means  10  for modulating the torque setpoints intended for the braking systems and for the powertrains is connected to the braking device control system  11  by the connection  23 . 
       FIG. 2  shows the various means involved in the control system, notably the powertrain control means  8 , a brake request distribution means  9  and a torque setpoint modulating means  10 . 
     The means  9  for distributing a braking request comprises the following components:
         a brake pedal interpretation means  30  is connected via the connection  18   a  to a computing means  39  that computes the reference speed contained in the modulating means  10 . The interpretation means  30  is also connected at input to the sensor  7  by the branch  7   b  of the connection  7   a , and to the powertrain control means  8  by the connection  17   b.          

     The interpretation means  30  is connected at output to a compensation means  31   a  by the connection  57  and to a computing means  32   a  for computing the acceleration of the vehicle by the connection  59 . 
     The means  32   a  for computing the acceleration of the vehicle is connected by the branch  56  of the connection  18   a  to the computing means  39  that computes the reference speed contained in the modulating means  10 . The computing means  32   a  for computing the acceleration is also connected at input, by the connection  17   d , to the means  24  of interpreting the acceleration pedal of the powertrain control means  8 . The computing means  32   a  that computes the acceleration is connected at output to the compensation means  31   b  by the connection  60 . 
     The compensation means  31   b  is connected to the means  35  of determining the distribution of the recuperative braking between the front and rear wheelsets by the connection  61 , and to the friction braking compensating means  37  by the branch  62  of the connection  61 . 
     The compensation means  31   a  is connected by one of its inputs to the sensors  7  via the branch  7   c . The compensation means  31   a  is connected at output to the means  34  of determining the maximum recuperative braking by the branch  58   a  of the connection  58 , and to the means  38  for determining the prebraking setpoint by the connection  58 . 
     The means  34  for determining the maximum recuperative braking is connected by one of its outputs to the powertrain setpoint optimizing means  27  of the powertrain control means  8  by the connection  17   e . The means  34  of determining the maximum recuperative braking is also connected at output by the branch  63  of the connection  17   e  to the means  35  of determining the distribution of the recuperative braking between the front and the rear wheelsets. 
     The means  36  for interpreting the situation is connected at input by the connection  7   d  to the sensors  7 . The interpretation means  36  is connected at output by the connection  64  to the means  35  of determining the distribution of the recuperative braking between the front and rear wheelsets. The interpretation means  36  is also connected at output by the connection  18   b  to the means  39  of computing the reference speed contained in the modulating means  10 . 
     The means  38  for determining the prebraking setpoint is connected at output to the friction braking compensating means  37  by the connection  66 . 
     The means  35  for determining the distribution of the recuperative braking between the front and rear wheelsets is connected by its outputs to the friction braking compensating means  37  by the connection  65 , to the means  27  of optimizing the powertrain setpoints of the control means  8  by the connection  17   f  and to the engine torque coordinating device  29  by the connection  17   h.    
     The means  37  for compensating for the friction braking is connected by one of its inputs to the means  28  of dynamic compensation of the powertrain setpoints contained in the powertrain control means  8  by the connection  17   i . The compensation means  37  is connected at output by the connection  18   c  to the switch  48  of the modulating means  10 . 
     The means  10  for modulating the torque setpoints intended for the braking systems and for the powertrains comprises the following main components:
         the computing means  39  for computing the reference speed is connected at input to the sensors  7  by the connection  7   e  and to the situation interpreting means  36  by the connection  18   b . The computing means  39  is connected at output to the interpretation means  30  by the connection  18   a , to the situation determining means by the connection  81 , to an electronic stability control device  41  (usually known by its electronic stability program abbreviation ESP) by the connection  67   a , to an ABS device  42  by the connection  67   b , to a traction control device  44  by the connection  67   c , to a device preventing recuperative braking on the rear wheelset  45  by the connection  67   d  and to a device supporting the reference speed  46  by the connection  67   e.          

     The situation determining means  40  is connected at input to the sensors  7  by the connection  7   f . The situation determining means  40  is connected at output to the switch  48  by the connection  82 , to the electronic stability control device  41  by the connection  68   a , to the ABS device  42  by the connection  68   b , to an HBD (Hybrid Brake-force Distribution) device by the connection  68   c , to the traction control device  44  by the connection  68   d , to the device preventing recuperative braking on the rear wheelset  45  by the connection  68   e  and to the reference speed maintaining device  46  by the connection  68   f.    
     The device  47  for coordinating the braking is connected by its inputs to the ESP device  41  by the connections  74  and  104 , to the ABS device  42  by the connections  75  and  103 , to the HBD device  43  by the connection  76 , to the traction control device  44  by the connections  77   a ,  77   b  and  105 , to the device preventing recuperative braking on the rear wheelset  45  by the connection  78  and to the reference speed maintaining device  46  by the connection  79 . 
     The device for coordinating the braking  47  is connected by its outputs to the switch  48  by the connection  80  and to the device  29  for coordinating engine torque by the connections  16   a  and  16   c.    
     The switch  48  is connected at output to the braking device control system  11  via the connection  23 . 
     The means  8  for controlling the powertrains comprises the following main components:
         the means  24  for interpreting the accelerator pedal is connected by one of its inputs to the sensors  7  by the connection  7   a . The interpretation means  24  is connected by one of its outputs to the means  32   b  for computing the acceleration of the vehicle by the connection  50 .       

     The vehicle acceleration computing means  32   b  is connected at input to the brake pedal interpreting means  30  by the branch  17   c  of the connection  59 . The vehicle acceleration computing means  32   b  is connected at output to the compensation means  31   c  by the connection  51 . 
     The compensation means  31   c  is connected at output to the means  27  of optimizing the powertrain setpoints by the connection  52 , and to the means  28  for dynamically compensating the powertrain setpoints by the branch  53  of the connection  52 . 
     The powertrain setpoint optimizing means  27  is connected by at least one of its inputs to the means  34  of determining the maximum recuperative braking by the connection  17   e . The optimizing means  27  is connected at output by the connection  54  to the powertrain setpoint dynamic compensating means  28 . 
     The powertrain setpoint dynamic compensating means  28  is connected by at least one of its inputs by the branch  53  of the connection  52  to the compensating means  31   c . The powertrain setpoint dynamic compensating means  28  is connected by at least one of its outputs to the engine torque coordinating device  29  by the connection  55  and to the friction braking compensating means  37  by the connection  17   i.    
     The engine torque coordinating device  29  is connected by at least one of its inputs to the means  35  of determining the distribution of recuperative braking between the front and rear wheelsets by the connection  17   h  and is connected by the connection  16   c  to the braking coordination device  47 . The engine torque coordinating device  29  is connected at output to the front  1  and rear  2  powertrains by the connections  19  and  20 . 
     The sensors  7  supply information regarding the position of the brake pedal XBP_sens or the position of the master cylinder P_MC_sens to the interpreting means  30 . The interpreting means  30  also receives an estimate of the longitudinal speed of the vehicle VVH_x_est by the connection  18   a  and the minimum deceleration generated by the mechanical resistance of the powertrains for zero acceleration GPT_min, also known as the foot-off deceleration. 
     The interpreting means  30  then determines the deceleration due to the depressing of the brake pedal GBP_sp and the derivative with respect to time of the deceleration due to the depressing of the brake pedal dGBP_sp. The variables GBP_sp and dGBP_sp are emitted by the connection  57  and the variable GBP_sp is emitted by the connection  59 . 
     The means  32   a  for computing the acceleration of the vehicle receives the estimate of the longitudinal speed of the vehicle VVH_x_est by the branch  56  and receives the acceleration generated by the powertrains GPT_sp. The vehicle acceleration computing means  32   a  then determines the vehicle acceleration setpoint GWH_sp according to the driver request. 
     The compensating means  31   b  then receives the vehicle acceleration setpoint GWH_sp and determines the total vehicle torque setpoint TWH_sp by applying the following relationship:
 
TWH_sp= M·R· GWH_sp
         where M is the estimated mass of the vehicle and   R is the estimated radius of the wheel.       

     At the same time, the compensating means  31   a  receives as input the variables GBP_sp and dGBP_sp. The compensating means  31   a  then determines the torque associated with the depressing of the brake pedal TBP_sp and the derivative of the torque associated with the depressing of the brake pedal dTBP_sp.
 
TBP_sp= M·R· GBP_sp
 
dTBP_sp= M·R· dGBP_sp
 
     The means  34  for determining the maximum recuperative braking receives as input the torque associated with the depressing of the brake pedal TBP_sp and the derivative of the torque associated with the depressing of the brake pedal dTBP_sp. The means  34  of determining the maximum recuperative braking then determines the minimum braking torque excluding friction braking TNBP_min. 
     The means  36  of interpreting the situation receives, from the sensors  7 , the angle through which the wheels are turned ASW_sens. Further, the situation interpreting means  36  receives logic signals reflecting the fact that recuperative braking on the rear wheelset has been prevented Flag_int_recup and the fact that optimized four-wheel drive mode has been activated Flag — 4wd_opt, each of these two signals originating from the torque setpoint modulating means  10 . 
     The means  36  for interpreting the situation then determines the traction grip potential threshold Mu_trac, the recuperative braking grip potential threshold Mu_recup, the traction grip potential dynamic threshold Mu_trac_dyn, and the recuperative braking grip potential dynamic threshold Mu_recup_dyn. 
     The determining means  35  receives the vehicle total torque setpoint TWH_sp, the minimum braking torque excluding friction braking TNBP_min, the traction grip potential threshold Mu_trac, the recuperative braking grip potential threshold Mu_recup, the traction grip potential dynamic threshold Mu_trac_dyn, and the recuperative braking grip potential dynamic threshold Mu_recup_dyn. 
     The determining means  35  then determines the minimum torque on the rear axle in near-static conditions TPT_r_min, the maximum torque on the rear axle under near-static conditions TPT_r_max, the minimum torque on the rear axle under transient conditions TPT_r_min_trans and the maximum torque on the rear axle under transient conditions TPT_r_max_trans. 
     At the same time, the determining means  38  receives the torque associated with the depressing of the brake pedal TBP_sp and the derivative of the torque associated with the depressing of the brake pedal dTBP_sp and determines the braking torque directly applied to the brakes ΔFBP_sp. 
     The friction braking compensating means  37  receives the vehicle total torque setpoint TWH_sp, the minimum torque on the rear axle under near-static conditions TPT_r_min, the maximum torque on the rear axle under near-static conditions TPT_r_max, the torque setpoint of the rear powertrain TPT_r_osp, the torque setpoint of the front powertrain TPT_f_osp and the braking torque directly applied to the brakes ΔFBP_sp. 
     The friction braking compensating means  37  then determines the braking torque of the rear left wheel TFB_rl_osp compensated as a function of the resistive torque of the rear powertrain TPT_r_osp, the braking torque of the rear right wheel TFB_rr_osp compensated as a function of the resistive torque of the rear powertrain TPT_r_osp, the braking torque of the front left wheel TFB_fl_osp as a function of the resistive torque of the front powertrain TPT_f_osp and the braking torque of the front right wheel TFB_fr_osp compensated as a function of the front powertrain TPT_f_osp. 
     In the powertrain control means  8 , the accelerator pedal interpreting means  24  receives information relating to the depressing of the accelerator pedal and to the gear ratio from the sensors  7 . The interpreting means  24  further receives the estimate of the longitudinal speed of the vehicle VVH_x_est. The interpreting means  24  at output determines the acceleration generated by the powertrains GPT_sp. 
     The vehicle acceleration computing means  32   b  receives the acceleration generated by the powertrains GPT_sp and determines the vehicle acceleration setpoint GWH_sp. 
     It should be noted that the operation of the means  32   a  and  32   b  may be merged into a single means distributed across the means  8  and  9 . 
     The compensating means  31   c  receives the vehicle acceleration setpoint GWH_sp and determines the vehicle total torque setpoint TWH_sp by applying the following relationship:
 
TWH_sp= M·R· GWH_sp
         where M is the estimated-mass of the vehicle and   R is the estimated radius of the wheel.       

     Here again, it should be noted that the means  31   a ,  31   b , and  31   c  can be merged, their functions then being distributed across the means  8  and  9 . 
     The powertrain setpoint optimizing means  27  receives at input, in addition to the value TWH_sp, the minimum braking torque excluding friction braking TNBP_min and the minimum torque on the rear axle under near-static conditions TPT_r_min, the maximum torque on the rear axle under near-static conditions TPT_r_max, the minimum torque on the rear axle under transient conditions TPT_r_min_trans and the maximum torque on the rear axle under transient conditions TPT_r_max_trans. 
     The powertrain setpoint dynamic compensating means  28  emits at output the values of torque of the front powertrain TPT_f_osp, of torque of the rear powertrain TPT_r_osp and the gear ratio RCL_f_osp. 
     The engine torque coordinating device  29  receives from the braking coordinating device  47  the values of minimum torque on the rear axle under static conditions TPT_r_min_stat, of maximum torque on the rear axle under static conditions TPT_r_max_stat, of minimum torque on the rear axle under dynamic conditions TPT_r_min_dyn, of maximum torque on the rear axle under dynamic conditions TPT_r_max_dyn, of minimum torque on the front axle under static conditions TPT_f_min_stat, of maximum torque on the front axle under static conditions TPT_f_max_stat, of minimum torque on the front axle under dynamic conditions TPT_f_min_dyn, of maximum torque on the front axle under dynamic conditions TPT_f_max_dyn, and of gear ratio RCL_f_tgt. The engine torque coordinating device  29  also receives the values of torque of the front powertrain TPT_f_osp, of torque of the rear powertrain TPT_r_osp from the dynamic compensating means  28 . The coordinating device  29  comprises the components described in  FIG. 3 . 
     The coordinating device  29  comprises a computing means and a computing means  85 . The computing means  84  receives on its inputs the values of minimum torque on the rear axle under static conditions TPT_r_min_stat, of minimum torque on the rear axle under dynamic conditions TPT_r_min_dyn, of minimum torque on the front axle under static conditions TPT_f_min_stat and of minimum torque on the front axle under dynamic conditions TPT_f_min_dyn. The computing means also receives the values of torque of the front powertrain TPT_f_osp, of torque of the rear powertrain TPT_r_osp from the dynamic compensating means  28 . The computing means  84  determines the maximum value of torque that can be applied to the front and rear powertrains. These two values are transmitted to the computing means  85  by the connection  110 . 
     The computing means  85  receives on its inputs the values of maximum torque on the rear axle under static conditions TPT_r_max_stat, of maximum torque on the rear axle under dynamic conditions TPT_r_max_dyn, of maximum torque on the front axle under static conditions TPT_f_max_stat and of maximum torque on the front axle under dynamic conditions TPT_f_max_dyn. 
     The computing means  85  then determines the minimum values from among the values received, these values being emitted at output by way of target torque values TPT_f_tgt and TPT_r_tgt for the front and rear powertrains respectively. 
     The means  10  for modulating the torque setpoints intended for the braking systems and for the powertrains receives, via the reference speed computing means  39 , the traction grip potential threshold Mu_trac, the recuperative braking grip potential threshold Mu_recup, the traction grip potential dynamic threshold Mu_trac_dyn, and the recuperative braking grip potential dynamic threshold Mu_recup_dyn. It also receives, from the sensors  7 , wheel speed values. At output, it determines an estimate of the longitudinal speed of the vehicle VVH_x_est, and emits two logic signals preventing recuperative braking from being used on the rear wheelset Flag_int_recup and for activating the optimized four-wheel drive mode Flag — 4wd_opt. The computing means  39  is also connected by the connections  67   a ,  67   b ,  67   c ,  67   d  and  67   e  to the ESP device  41 , the ABS device  42 , the traction control device  44 , the device for preventing recuperative braking on the rear wheelset  45  and the device for maintaining the reference speed  46 . 
     A means  40  for determining the situation determines the situation of the vehicle from the data received from the reference speed computing means  39  and from the wheel speed received from the sensors  7 . It is connected by the connections  68   a ,  68   b ,  68   c ,  68   d ,  68   e  and  68   f  to the ESP device  41 , the ABS device  42 , the HBD device  43 , the traction control device  44 , the device for preventing recuperative braking on the rear wheelset  45  and the reference speed maintaining device  46 . The determining means  40  is also connected to the switch  48  by the connection  82 . 
     The driver assist and vehicle safety devices such as the ESP device  41 , the ABS device  42 , the HBD device  43 , the traction control device  44 , the device preventing recuperative braking on the rear wheelset  45  and the device for maintaining the reference speed  46  are known per se and will not be described here. 
     The device  47  for coordinating the braking comprises two parallel structures. A first structure is used to determine the engine torques intended for the engine torque coordinating device  29  and a second structure is used to determine the resistive torques intended for the switch  48  and for the braking systems  5   a ,  5   b ,  6   a  and  6   b.    
     The first structure is described in  FIG. 4 . The ESP  41 , ABS  42 , HBD  43  and traction control  44  devices are connected to a computing means  86  by the connections  76 ,  77   b ,  78  and  79 . The computing means  86  is also connected to a memory  88  by the connection  111 . 
     The devices  45  for preventing recuperative braking on the rear wheelset and for maintaining the reference speed  46  are connected to a computing means  87  by the respective links  74  and  77   b . The computing means  87  is also connected to a memory  89  by the connection  112 . 
     The computing means  86  receives the torque couples setpoints from the ESP  41 , the ABS  42 , the HBD  43  and the traction control  44  devices. The computing means  86  also receives, from the memory  88 , a threshold value corresponding to the minimum value expected at output of the computing means  86 . The values of minimum torque on the rear axle under static conditions TPT_r_min_stat, of minimum torque on the rear axle under dynamic conditions TPT_r_min_dyn, of minimum torque on the front axle under static conditions TPT_f_min_stat and of minimum torque on the front axle under dynamic conditions TPT_f_min_dyn are emitted at output of the computing means  86  via the connection  16   c.    
     At the same time, the computing means  87  receives the torque couples setpoints from the device  45  for preventing recuperative braking on the rear wheelset and the device  46  for maintaining the reference speed. The computing means  87  also receives a threshold value corresponding to the minimum value expected at output of the computing means  87 . The values of maximum torque on the rear axle under static conditions TPT_r_max_stat, of maximum torque on the rear axle under dynamic conditions TPT_r_max_dyn, of maximum torque on the front axle under static conditions TPT_f_max_stat and of maximum torque on the front axle under dynamic conditions TPT_f_max_dyn are emitted at output of the computing means  86  via the connection  16   a.    
     The second structure of the device  47  for coordinating the braking is described in  FIG. 5 . The braking coordinating device  47  comprises computing means  90 ,  92 ,  93  and  94  and a memory  91 . 
     The computing means  90  is connected to the ABS device  42  by the connection  103  and to an electronic brake-force distributor  95  by the connection  102 . 
     The computing means  92  is connected to the ESP device by the connection  104 , to the traction control device  44  by the connection  105  and to a memory  91  by the connection  106 . 
     The computing means  93  is connected to the computing means  92  by the connection  107  and to the sensors  7  via the connection  98 . 
     The computing means  94  is connected by the connection  109  to the computing means  90  and by the connection  108  to the computing means  93 . 
     The computing means  90 ,  92 ,  93  and  94  receive, on each of their inputs, a value containing four braking torque setpoints each one intended for one of the friction braking devices. 
     The computing means  90  determines the maximum value from among the signals received on these inputs. To do that, each of the four setpoints received at input is compared against the setpoint of comparable rank on the other input or inputs. For example, the rank i setpoint of the value j is compared against the rank i setpoint of the value k. The minimum setpoint for a rank i is considered from among all the setpoints. This method of comparison is valid for the computing means  92 ,  93  and  94 . 
     The means  92  and  93  each determine the minimum value from among the values received on their inputs. 
     Finally, the computing means  94  determines the maximum value from among the signals received on its inputs. This value contains the rear right wheel safe braking torque TFB_rr_tgt, the rear left wheel safe braking torque TFB_rl_tgt, the front left wheel safe braking torque TFB_fl_tgt and the front right wheel safe braking torque TFB_fr_tgt. This value is then emitted by the connection  80 . 
     The switch  48  thus receives on its inputs, via the connection  80 , the rear right wheel safe braking torque TFB_rr_tgt, the rear left wheel safe braking torque TFB_rl_tgt, the front left wheel safe braking torque TFB_fl_tgt and the front right wheel safe braking torque TFB_fr_tgt and, via the connection  18   c , the rear right wheel braking torque TFB_rr_osp, the rear left wheel braking torque TFB_rl_osp, the front left wheel braking torque TFB_fl_osp and the front right wheel braking torque TFB_fr_osp. Further, the switch  48  via the connection  82  receives control signals originating from the means  40 . 
     Thus, according to the situation detected by the means  40 , the switch emits at output either the set of safe braking torques determined by the computing means  47  or the set of braking torques determined by the friction braking compensating means  37 . 
     These braking setpoints are emitted via the connection  23  to the braking device control system  11  which in turn forwards the appropriate braking setpoints to each of the friction braking devices  5   a ,  5   b ,  6   a  and  6   b  via the connections  12 ,  13 ,  14  and  15 . 
     The control system and method described here allow the full extent of the drive and of the braking of a hybrid vehicle to be taken into consideration. A bipolar approach split between a device that determines torque and braking setpoints according to driver requests and a device that interprets the various signals from the sensors and driver assist and safety devices of the vehicle allows said driver requests to be modulated in such a way as to keep the vehicle under driving conditions that are compatible with vehicle safety.