Control of regenerative braking in an electric or hybrid vehicle

Abstract

A method controls regenerative braking of a vehicle equipped with regenerative brakes and with a separate braking apparatus. The method is designed to generate a regenerative braking setpoint as a function of a braking request signal coming from a driver pedal of the vehicle, according to a first setpoint generation mode. The method includes receiving a flag signal coming from an active safety system of the vehicle, detecting value changes of the received flag signal, when the received flag signal changes value to take a value corresponding to activation of regulation by the active safety system, incrementing a counter value, and comparing the counter with a threshold. When the counter reaches the threshold, a control signal is formed to end the generation of the regenerative braking setpoint according to the first calculation mode and to impose generation of the regenerative braking setpoint according to a second calculation mode.

Claims

1. A method for controlling regenerative braking of a vehicle equipped with a first, regenerative, braking means, including an electrical actuator to apply the regenerative braking to the vehicle, and with a second braking means separate from the first braking means, which method is designed to generate a regenerative braking setpoint as a function of a braking request signal coming from a driver pedal of the vehicle, according to a first calculation mode, the method comprising: receiving, via a processor, a flag signal coming from an active safety system of the vehicle; detecting, via the processor, value changes of the received flag signal; when the received flag signal changes value to take a value corresponding to activation of regulation by the active safety system, incrementing, via the processor, a counter value; comparing, via the processor, the counter with a threshold; when the counter reaches said threshold, forming, via the processor, a control signal so as to end the generation of the regenerative braking setpoint according to the first calculation mode and to impose generation of the regenerative braking setpoint according to a second calculation mode; and applying the regenerative braking setpoint to the electrical actuator to control the regenerative braking of the vehicle.

2. The control method as claimed in claim 1, wherein when the regenerative braking setpoint is generated according to the second calculation mode, the regenerative braking setpoint is zero.

3. The control method as claimed in claim 1, further comprising: applying a time filtering to the received flag signal prior to the detecting the value changes.

4. The method as claimed in claim 1, further comprising: receiving a master cylinder pressure signal; comparing the master cylinder pressure signal with a pressure threshold; and preventing the incrementing of the counter value when the master cylinder pressure is greater than the pressure threshold.

5. A device for controlling regenerative braking of a vehicle equipped with a first, regenerative, braking means and with a second braking means separate from the first braking means, which device is designed to generate a regenerative braking setpoint as a function of a braking request signal coming from a driver pedal of the vehicle, according to a first calculation mode, the device comprising: reception means for receiving a flag signal coming from an active safety system of the vehicle, and a processor configured to detect value changes of the received flag signal, to increment a counter value when the received flag signal changes value to take a value corresponding to activation of regulation by the active safety system, to compare the counter with a threshold and, when the counter reaches said threshold, to form a control signal so as to end the generation of the regenerative braking setpoint according to the first calculation mode and to impose generation of this regenerative braking setpoint according to a second calculation mode.

6. The device according to claim 5, wherein the processor is a central processing unit.

7. A motor vehicle, comprising: a first, regenerative, braking system: a second braking system separate from the first braking system; and a control system for controlling regenerative braking of a vehicle equipped with a first, regenerative, braking means and with a second braking means separate from the first braking means, comprising a module to generate a regenerative braking setpoint as a function of a braking request signal coming from a driver pedal of the vehicle, according to a first calculation mode and according to a second calculation mode, and a control device including reception means for receiving a flag signal coming from an active safety system of the vehicle, and a processor configured to detect value changes of the received flag signal, to increment a counter value when the received flag signal changes value to take a value corresponding to activation of regulation by the active safety system, to compare the counter with a threshold and, when the counter reaches said threshold, to form a control signal so as to end the generation of the regenerative braking setpoint according to the first calculation mode and to impose generation of this regenerative braking setpoint according to a second calculation mode.

8. The motor vehicle as claimed in claim 7, wherein the generation module comprises a braking management module arranged in order to calculate the regenerative braking setpoint value by multiplying a braking value representative of the braking carried out by the second braking means by a coefficient which depends on the calculation mode imposed.

9. The motor vehicle as claimed in claim 7, further comprising: an electrical actuator to exert braking on rear wheels of the motor vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be understood more clearly with reference to the figures, which illustrate nonlimiting embodiments.

(2) FIG. 1 shows an example of a vehicle according to one embodiment of the invention.

(3) FIG. 2 shows an example of a device for controlling regenerative braking, according to one embodiment of the invention.

DETAILED DESCRIPTION

(4) Identical references may be used from one figure to the other in order to denote elements which are identical or similar in their form or in their function.

(5) Referring to FIG. 1, an electrical or hybrid vehicle comprises wheels 14, 15 and an electric motor 13 capable of driving the rear wheels 14 in motion or of braking these rear wheels 14 so as to recharge a battery (not represented).

(6) A module 12 for generating a regenerative braking setpoint, for example an electrical braking setpoint C.sub.el, makes it possible to generate this setpoint value C.sub.el according to a first calculation mode, as a function of a driver setpoint value C.sub.c coming from a driver request calculation module 11 or DRC.

(7) This calculation module 11 receives as input an information value regarding the status of the brakes, or BLS (“Brake Info Status”) and a master cylinder pressure value, these not being represented in FIG. 1. This module 11 thus generates a setpoint signal C.sub.c on the basis of values coming from sensors.

(8) The module 12 is arranged in order to apply a multiplier coefficient, for example equal to 0.1, to this setpoint value C.sub.c, and thus to obtain the electrical braking setpoint value C.sub.el.

(9) Expressed another way, when this electrical setpoint value C.sub.el is obtained according to the first calculation mode, this setpoint value is selected to be equal to 10% of the braking request signal C.sub.c coming from the driver pedal. It is therefore supplementary electrical braking which is added to the hydraulic braking carried out directly on the basis of the brake pedal, without decoupling.

(10) A braking control device 10 receives flag signals coming from various active safety systems (not represented), for example an ABS system, an AYC system and/or the like. When one of these flag signals is equal to 1, the device 10 generates an overall flag signal F which then takes the value 1, and, so long as this signal F is equal to 1, that is to say so long as one of the active safety systems has activated regulation, the electrical braking setpoint C.sub.el is zero.

(11) Furthermore, the device 10 is arranged in order to increment a counter each time a flag signal obtained from the various flag signals of the different active safety systems changes to 1. When the counter reaches a threshold, then a signal F coming from the device 10 takes a value corresponding to permanent prevention of the regenerative braking.

(12) FIG. 2 shows a more precise example of a control device according to one embodiment of the invention.

(13) In this embodiment, the device 10 comprises an OR gate 100 receiving as input various flag signals coming from different respective active safety systems, for example a flag flag_ABS coming from an ABS system, a flag flag_AYC coming from an AYC system, a flag flag_MSR coming from an MSR system, a flag flag_ASR coming from an ASR system, a flag flag_EBD coming from an EBD system.

(14) The signal flag_reg coming from this OR gate 100 is received at the input of an AND gate 101. This AND gate furthermore receives a signal which takes a value 1 when a master cylinder pressure value P is less than a master cylinder pressure threshold THR_P. Thus, the signal obtained from the AND gate 101 is equal to 1 only if the master cylinder pressure is less than a threshold, and if the signal flag_reg is equal to 1.

(15) This signal is received in a filtering module 102, in which filtering of the high states is carried out when their duration is too short. Expressed another way, if the signal coming from the AND gate 101 has a value equal to 1 for a time less than a given period of time, then the signal f_r coming from the filtering module 102 remains zero.

(16) The signal f_r coming from this module 102 is received by a counting module 103 arranged in order to be incremented at each leading edge of the incoming signal.

(17) In a preferred embodiment, only the leading edges of the signal f_r lead to incrementation of the signal Count.

(18) In an alternative embodiment, the signal Count is incremented at each leading edge of the signal f_r and each time the signal f_r has a high value for a predetermined period of time. Thus, account is in some way taken of the duration of the high signal periods of the signal f_r. The relative weight of the duration of the high signal periods and the leading edges depend on the value of this predetermined period of time and the respective increments. For example, the choice may be made of a period of time of one minute and increments of 1 in both cases: a high signal lasting 20 seconds will lead to an increment of 1, while a high signal of 70 seconds will lead to an increment of 1+1=2 of the counter. The predetermined period of time may, of course, have a shorter duration, for example one second.

(19) Returning to FIG. 2, the signal Count obtained in this way is then compared with a threshold THR. If the signal Count reaches or exceeds this threshold THR, then a bistable module 104 generating the signal S will make this signal S change from a value S.sub.1 to a value S.sub.2. The value S.sub.1 corresponds to a relatively high regenerative braking limit, while the value S.sub.2 corresponds to a relatively low regenerative braking limit, for example 0.

(20) Expressed another way, when the signal S changes from the value S.sub.1 to the value S.sub.2, the module referenced 12 in FIG. 1 changes from a first calculation mode for the setpoint C.sub.el, in particular by applying a coefficient to the driver setpoint value C.sub.c, to a second calculation mode in which this electrical braking setpoint value C.sub.el is zero.

(21) In this embodiment, the counter is reset to 0 only after the device is turned off, that is to say at the end of mission.

(22) Furthermore, the signal F in FIG. 1 which is a stability indicator may be the signal flag_reg coming from the module 100, or the signal coming from the module 101, or alternatively the signal f_r coming from the module 102.

(23) In this embodiment, the vehicle 1 is a front-wheel drive vehicle, the electrical braking being applied only to the rear driving wheels 14, and therefore with a braking potential more limited than braking on all the wheels. There is a greater risk of slipping on the rear wheels, which risks causing locking of the wheels when the grip conditions are relatively precarious.

(24) The method described above, based on counting the long-term activations likely to be associated with the condition of the road, of the active regulation systems, can thus make it possible to diagnose a condition of the road corresponding to precarious grip conditions and to prevent any electrical braking when this diagnosis is made.

(25) Such precarious grip conditions may for example be associated with the presence of ice, snow, or quite simply the fact that the road is wet.

(26) The installed regulation counter can thus supplement the stability indicator known from the prior art.

(27) The invention is not limited to prevention of electrical braking when the counter reaches a threshold. Provision could, for example, be made to allow the electrical braking but with a lower power than when the setpoint C.sub.el is generated according to the first calculation mode. For example, the methods employed in the module referenced 12 in FIG. 1 may be identical from one calculation mode to the other, except for the fact that the coefficient applied to the braking setpoint C.sub.c of the driver is less than the second calculation mode. For example, this coefficient may be 10% or 20% in the first calculation mode and only 1 or 2% in the second calculation mode. Expressed another way, the supplementary electrical braking applied is much less after an unsatisfactory state of grip has been diagnosed.