Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
  • B60T8/17—Using electrical or electronic regulation means to control braking
  • B60T8/172—Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T2220/00—Monitoring, detecting driver behaviour; Signalling thereof; Counteracting thereof
  • B60T2220/02—Driver type; Driving style; Driver adaptive features

Definitions

• the invention relates to a method for controlling a braking device of a vehicle.
• the invention relates more particularly to a method for controlling a braking device of a vehicle with a view to assisting the driver during emergency braking, of the type comprising brakes acting on the wheels of the vehicle, a device brake control by the driver, a brake assist device which amplifies the intensity of the braking force as a function of the driver's action on the control device, according to a determined amplification law, means for control of the brakes in order to prevent the wheels from locking during braking, or anti-lock device, and means for modifying the law for amplifying the braking intensity, of the type comprising an electronic control unit for the braking device which uses data, provided by sensors, representative in particular:
• the anti-lock system therefore allows the driver, when he judges the emergency situation, to exert a very significant pressure on the brake pedal without having to worry about modulating this pressure and therefore having the sole concern of slowing down the fastest possible his vehicle.
• an emergency braking assistance system which makes it possible, by continuously monitoring the behavior of the vehicle and the driver, for example from sensors providing information on the vehicle speed, braking intensity requested by the driver, etc. to detect an emergency braking situation and to apply sufficient braking pressure for the vehicle to brake to its full potential.
• the emergency braking thus carried out consists in maintaining a braking force such that the wheels are always at the blocking limit.
• the emergency detection protocol uses the vehicle parameters and compares them to a map.
• This map delimits two zones: a normal braking zone where the degree of activation is 0 and an emergency braking zone where it takes the value 1.
• the system is activated as soon as the border between these two zones is crossed (passage from 0 to 1).
• the control law is therefore of the binary type.
• mapping cannot adapt to the behavior specific to each driver and it therefore corresponds to a compromise.
• the system does not allow braking to be modulated when the emergency braking strategy is deactivated.
• the invention provides a control method of the type described above, characterized in that, to activate the emergency braking strategy, the electronic control unit uses a control law which is a fuzzy relation of order 2 connecting each braking state to a degree of triggering of emergency braking, whose value varies linearly between 0 and 1 and which takes the following values:
• n a value between 0 and 1 when one is in the fuzzy zone of the relation; so as to activate the emergency braking strategy when the degree of activation takes, for a number n of calculation steps, n increasing values, or equal, non-zero, the nth value being equal to 1.
• the electronic control unit performs a short-term diagnosis to determine, according to the intensity of the accelerations requested by the driver and according to the intensity of the force exerted on the brake control device, a value which is representative of the type of behavior of the driver, and which is between a low value corresponding to a driver with hesitant braking and a high value corresponding to a driver with safe braking, and the electronic control unit modifies the fuzzy relationship of the law controlling the activation of the emergency braking strategy as a function of the diagnostic value, so that the higher the diagnostic value, the more difficult the fuzzy zone for triggering emergency braking to be reached, and the lower the diagnostic value, the easier it is to reach the fuzzy zone for triggering emergency braking;
• the control law comprises at least two fuzzy relationships, or reference relationships, corresponding respectively to an ideal law for a low diagnostic value and to an ideal law for a high diagnostic value, and the fuzzy relationship used by the law of command, for a diagnostic value determined, is calculated by linear interpolation of the
• control law includes an intermediate reference relation corresponding to an ideal law for an intermediate diagnostic value between the low value and the high value;
• the short-term diagnosis is carried out continuously while the vehicle is moving, at a fixed frequency; the electronic control unit calculates, from the short-term diagnostic value, a medium-term diagnostic value which follows the growth of the short-term diagnostic value, but which decreases more slowly than this, and the electronic control unit uses the medium term diagnostic value as a value representative of the behavior of the driver;
• the short-term diagnostic value is between the low value 0.3 and the high value 0.7;
• the electronic unit orders the deactivation of the emergency braking strategy when at least one of the following conditions is met:
• the vehicle speed is lower than a determined minimum speed
• the value of the intensity of the force applied to the brake control device is less than a given intermediate force during a number i of calculation steps, with a decreasing or zero evolution, the ith value being less than a force minimum given
• the value of the intensity of the force applied to the brake control device is less, for a number i of calculation steps, than a given percentage of the maximum value of the intensity of the force, measured during the active activation of the emergency braking strategy, with a decreasing or zero evolution;
• the electronic unit commands a progressive deactivation of the emergency braking strategy; the electronic unit observes a time-out period, after activation of the emergency braking strategy, during which it only orders the sudden deactivation of the emergency braking strategy if one of the following conditions is met:
• the value of the intensity of the force applied to the brake control device is less than a given median force during a number j of calculation steps, with a decreasing or zero evolution.
• a brake assist device comprising a brake booster which is interposed between the brake control device and the brake actuation device, of the type in which the brake booster comprises a cylinder fitted with a piston sliding axially which delimits two chambers and which acts on the brake actuation device, the braking device includes sensors which measure the piston stroke and its speed, these measurements respectively corresponding to the data representative of the braking intensity and to the data representative of the variation of the braking intensity over time.
• FIG. 1 is a schematic view which shows a vehicle equipped with a braking device for the implementation of the method according to the invention
• FIG. 2 is a schematic in axial section which shows a brake booster in the rest position
• FIG. 4 is a diagram which illustrates a law for controlling the activation of the emergency braking strategy according to the invention in the case of a “calm” driver;
• FIG. 5 is a diagram similar to the previous one which illustrates a law for controlling the activation of the emergency braking strategy according to the invention in the case of a “sporty” driver;
• FIG. 6 is a flowchart which illustrates the principle of deactivation of the emergency braking strategy according to the invention.
• FIG. 1 shows a vehicle 10 equipped with a braking device 12 for implementing the method according to the invention.
• the braking device 12 comprises brakes 14 which act on each of the wheels 16 of the vehicle 10 as a function of the pressure inside a hydraulic control circuit 18.
• the driver controls the brakes 14 by means of a control device 20, for example a brake pedal, which acts on a master cylinder 22 varying the pressure in the hydraulic circuit 18.
• a brake assist device 24 is interposed between the brake pedal 20 and the master cylinder 22.
• the assistance device 24 amplifies the intensity of the braking force as a function of the bearing force of the driver on the brake pedal 20, according to a determined amplification law.
• the braking assistance device 24 therefore makes it possible, for low driver effort on the brake pedal 20, to obtain significant hydraulic pressure in the circuit 18.
• FIGS. 2 and 3 There is shown diagrammatically in FIGS. 2 and 3 an example of a braking assistance device 24 comprising a pneumatic brake booster 26, of the mastervac type, operating by vacuum.
• the brake booster 26 which is interposed between the brake pedal 20 and the master cylinder 22, comprises a control cylinder 28 of large diameter, separated into two chambers 30, 32 by a motor piston 34 sliding axially.
• the piston 34 includes a tubular central body 38 which extends forward and backward and which is in axial support, by its transverse front end face 40, against the rear axial end of the push rod 42 of the master cylinder 22.
• the rear chamber 30 is capable of communicating with the outside, which is subjected to atmospheric pressure, through a rear central orifice 44 of the tubular body 38, and with the front chamber 32, which is subjected to a vacuum, by a central front orifice 46 of the tubular body 38.
• the front chamber 32 communicates with a vacuum source via a vacuum channel 48 provided with a non-return valve (not shown).
• the vacuum is provided for example by a vacuum pump or by the vacuum prevailing in the intake manifold of a gasoline engine in the deceleration phase.
• a rod 50 which is controlled in axial displacement by the brake pedal 20, slides axially in the tubular body 38 of the piston 34 and carries a control valve 52.
• the control valve 52 comprises a rear valve 54, which is capable of closing the rear opening, and a front valve 56 which is capable of closing the front opening 46, the two valves 54, 56 being integral with the one of the other.
• the two chambers 30, 32 communicate through the front orifice 46 and they are therefore subjected to the same pressure which is lower than atmospheric pressure, the rear valve 54 closing the rear orifice 44.
• the driver presses on the brake pedal 20 which axially displaces the control rod 50 forwards.
• the axial displacement of the control rod 50 acts on the control valve 52 and causes the opening of the rear valve 54 and the closing of the front valve 56.
• Air at atmospheric pressure therefore enters the rear chamber 30 through the rear orifice 54.
• the two chambers 30, 32 are then no longer subjected to the same pressure.
• the pressure difference between the two faces of the piston 34 causes it to move axially forwards.
• the pushing force exerted on the pushing rod 42 depends on the pressure difference between the two faces of the piston 34.
• control valve 52 which doses the pressure difference on the piston 34, in proportion to the force produced by the driver on the brake pedal 20.
• the vehicle also includes an electronic unit 58 for controlling the braking device 12.
• the electronic unit 58 makes it possible in particular to perform the anti-lock function of the wheels 16.
• the electronic unit 58 analyzes for example the speed of each wheel V r , during braking, by means of sensors 60, and it then controls the hydraulic braking pressure on each wheel 16, so as to prevent blocking. wheel 16.
• the electronic unit 58 is also capable of detecting an emergency braking situation, so as to activate an emergency braking strategy SFU, with a view to causing maximum deceleration of the vehicle 10.
• the electronic unit 58 controls the assistance device 24 by modifying the amplification law so as to increase the intensity of the braking force until the system is triggered. anti-lock, which makes it possible to obtain a maximum deceleration of the vehicle 10.
• the electronic unit 58 controls, for example, the servo-control valve 52 of the brake booster 26 so as to force the opening of the rear valve 54, independently of the force exerted by the driver on the rod. controls 50 with the brake pedal 20, which increases the pressure difference between the two chambers 30, 32, and therefore the intensity of the braking.
• the electronic unit 58 receives information from other sensors.
• An acceleration sensor 62 informs the electronic unit
• the Ace data representative of the intensity of the acceleration requested is linked to the motorization mode used.
• an acceleration sensor 62 is chosen which is inexpensive and which is simple to install in the vehicle 10.
• a sensor 62 is preferably chosen which measures the opening angle of the intake flap.
• the vehicle 10 also includes a speed sensor 64 which measures the speed V v of longitudinal movement of the vehicle 10.
• the speed sensor 64 is necessary for the electronic unit 58 in order to determine when it deactivates the braking strategy d SFU emergency.
• the brake 20 control device 14 includes a sensor (not shown) which informs the electronic unit 58 of the value of the force F exerted by the driver on the control rod 50 of the brake booster 26, this value F being representative of the braking intensity requested by the driver. Note that the stroke of the brake pedal 20 is generally not representative of the braking intensity requested by the driver.
• the brake pedal 20 and the control rod 50 of the brake booster 26 are permanently coupled, which means that if the electronic unit 58 controls a determined amplification of the braking force, the brake booster 26 will also exert an action on the brake pedal 20 which will sink as much.
• the stroke data of the pedal 20 therefore does not distinguish the voluntary action of the driver on the pedal 20 and the "involuntary" action of the brake booster 26 on the pedal 20.
• the force F exerted on the control rod 50 takes into account the force actually exerted by the driver on the pedal 20.
• the brake pedal 20 is decoupled from the brake booster 26, which could be the case in a control device 20 of the brakes 14 with electronic control for example, the data given by the brake pedal 20 could be representative of the will of the driver to brake.
• the braking assistance device 24 includes a sensor (not shown) which informs the electronic unit 58 of the stroke C p of the piston 34 of the brake booster 26.
• the stroke of the piston C p is a value representative of the braking intensity since it represents the axial displacement actually transmitted to the push rod 42 of the master cylinder 22.
• the electronic unit 58 determines the speed of axial displacement of the piston 34, or speed of the piston V p .
• the speed of the piston V p is representative of the variation of the braking intensity over time.
• the data couple consisting of the stroke of the piston C p and its speed V p at a given instant defines a braking state E f . It is noted that this type of sensor based on the stroke of the piston C p is preferable to a sensor of the stroke of the brake pedal 20 because it is less expensive.
• the piston 34 has a translational movement while the pedal 20 has a rotational movement, and because the stroke of the piston C p does not take account of the mechanical games in the pedal 20 , especially the play due to wear.
• the electronic control unit 58 uses a control law, to activate the emergency braking strategy SFU, which is a fuzzy relationship of order 2 connecting each braking state E f to a degree of activation D ⁇ of emergency braking.
• FIG. 4 shows an example of a control law for activating the SFU emergency braking strategy.
• the degree of activation D f of the emergency braking takes the value 0 when one is outside the fuzzy relation, as for point A.
• the zone outside the fuzzy relation is delimited by the lower curve Ci and it consists of the zone of FIG. 4 located on the curve Ci and below.
• the electronic unit 58 When the triggering degree D f is equal to 0, the electronic unit 58 does not activate the emergency braking strategy SFU.
• the degree of activation Df of the emergency braking takes the value 1 when one is in the core of the fuzzy relation, as for point C.
• the nucleus of the fuzzy relation is delimited by the upper curve C 2 and it consists of the zone of FIG. 4 located on the curve C 2 and above.
• the degree of activation D f of the emergency braking takes a value between 0 and 1 when one is in the fuzzy zone of the relation, as for point B.
• the fuzzy zone of the relation is the zone which is included between the curve C 2 and the curve Ci.
• the electronic unit 58 controls the activation of the emergency braking strategy SFU when the degree of activation D f takes, during a number n of calculation steps, n increasing values, or equal, non-zero, the nth value being equal to 1.
• the electronic unit 58 uses a calculation frequency of 300 Hertz and a number n of calculation steps equal to 3.
• the first D f i and the second degree of trigger D f2 are confirmation points.
• This confirmation strategy makes it possible to prevent the emergency braking strategy SFU from being triggered during spikes in speed of the unreliable piston 34.
• the confirmation strategy costs two calculation steps, ie approximately 6.7 milliseconds at the chosen working frequency of 300 Hertz.
• the electronic unit 58 performs, at a determined frequency, for example 1 0 Hertz, a short-term diagnosis D c t and a medium-term diagnosis D mt which determine the behavior of the driver when braking.
• a short-term diagnosis D c t the control unit stores and interprets the data Ace, F representative of the driver's desire to accelerate and the driver's desire to brake.
• the data representative of the will to accelerate are for example the Ace values of the angle of opening of the intake flap over a period of one minute.
• the data representative of the braking will are for example the values of the force F exerted on the control rod 50 of the brake booster 26 over a period of two minutes. From this data Ace, F, the electronic unit calculates a diagnostic value D ct which is the image of the behavior of the driver when braking.
• This diagnostic value D ct is for example between a low value of 0.3 for a driver with hesitant behavior, and a high value of 0.7 for a driver with excellent behavior.
• the estimation of the braking behavior style makes it possible to modify the fuzzy zone of the control law of the activation of the SFU emergency braking strategy.
• the diagnostic value will be low and the fuzzy region of the control law will be easy to reach.
• Such a control law is for example shown in FIG. 4.
• the diagnostic value D ct will be high and the blurred area of the control law will be more difficult to reach.
• the electronic unit 58 takes account of a possible modification of the driving style of the driver during driving because the short-term diagnosis D c t is carried out continuously.
• three fuzzy relations serve as a reference and each correspond to an ideal control law respectively for a low diagnostic value D c t (0.3), for an intermediate diagnostic value D c t (0.5), and for a high diagnostic value D c t (0.7).
• the fuzzy relationship used by the control law for a determined diagnostic value D c t, between 0.3 and 0.7, is calculated by linear interpolation of the fuzzy reference relationships.
• fuzzy reference relations are established on the basis of a set of tests, for example by behavior tests carried out on a determined number of drivers representative of the different styles of driving behavior, and for a specific vehicle.
• the electronic unit 58 does not directly use the short-term diagnostic value D c t but it uses a medium-term diagnostic value D m t which is calculated from several short-term diagnostic values
• the medium-term diagnostic value D mt is calculated as follows.
• the short-term diagnosis D ct at time t is greater than or equal to the medium-term diagnosis D m t at time t-1, then the medium-term diagnosis D m t at time t is equal to short-term diagnosis D c t at time t.
• the medium-term diagnosis D m t at time t is equal to the diagnosis at medium term D m t at time t-1 minus a decrement, for example
• the electronic unit 58 After the electronic unit 58 has activated the emergency braking strategy SFU, the latter must remain activated if the vehicle 10 is still in an emergency braking situation.
• the electronic unit 58 must not deactivate the SFU emergency braking strategy too early; say that the electronic unit 58 should not interpret the release of the force on the brake pedal 20 as the sign of the end of the emergency braking situation.
• the SFU emergency braking strategy must be deactivated as soon as the brake pedal 20 is released.
• the electronic unit 58 commands the deactivation of the emergency braking strategy SFU in the following manner.
• the flowchart which is shown in FIG. 6 illustrates the principle of deactivation of the SFU emergency braking strategy.
• the electronic unit 58 After activation of the emergency braking strategy SFU, the electronic unit 58 observes a time delay period T p , here fixed at 0.5 seconds.
• the electronic unit 58 commands the deactivation of the emergency braking strategy SFU in two cases.
• the electronic unit 58 commands the deactivation of the emergency braking strategy SFU if the value of the force intensity Fi on the control rod 50 of the brake booster 26 is less than a force F f j of determined low intensity, for example 30 Newtons, which corresponds substantially to a sudden release of the brake pedal 20.
• the electronic unit 58 commands the deactivation of the emergency braking strategy SFU if the value of the intensity of the force Fi applied to the control rod 50 of the brake booster 26 is less than a determined median force F me , for example 100 Newtons, during a number j of calculation steps, with a decreasing or zero evolution .
• the electronic unit 58 therefore commands the deactivation of the emergency braking strategy SFU if the intensity of the force Fi on the control rod 50 is less than 100 Newtons at a first step, then if the intensity of this effort decreases or stagnates at the next two steps, that is to say if the intensity of the effort F 2 at the second step is less than or equal to Fi and if the intensity of the effort F 3 at the third step is less than or equal to F 2 .
• a mode of sudden deactivation of the emergency braking strategy SFU is used, that is to say that the electronic unit 58 abruptly stops modifying the amplification law of the. braking assistance device 24 which then operates in a conventional manner, according to a determined amplification law which depends solely on the force of the driver on the control rod 50 of the brake booster 26.
• the electronic unit 58 can deactivate the emergency braking strategy SFU according to a sudden deactivation mode or according to a progressive deactivation mode.
• the electronic unit 58 commands the sudden deactivation of the emergency braking strategy SFU, since it is considered that the vehicle 10 is almost stopped and the braking is finished.
• the electronic unit 58 determines whether the value Fi of the intensity of the force applied to the control rod 50 of the brake booster 26 is less than a given intermediate force Fj nt , for example 130 Newtons, during a number i of calculation steps, with a decreasing or zero evolution, the ith value being less than a minimum force F m in given, for example 100 Newtons.
• a given intermediate force Fj nt for example 130 Newtons
• the ith value being less than a minimum force F m in given, for example 100 Newtons.
• three calculation steps are used at a frequency analogous to the frequency of the calculation steps for activating the SFU emergency braking strategy.
• the electronic unit 58 determines whether the value Fi of the intensity of the force applied to the control rod 50 of the brake booster 26 is less, for a number i of calculation steps, than a given percentage, for example 40 percent, of the maximum value F ma ⁇ of the intensity of the force on the control rod 50 since the end of the time delay T p , with a decreasing or zero evolution.
• three calculation steps are used at a frequency analogous to the frequency of the calculation steps for activating the SFU emergency braking strategy.
• the electronic unit 58 commands a progressive deactivation of the emergency braking strategy SFU.
• the electronic unit 58 controls a regular reduction in the vacuum in the front chamber 32 of the brake booster 26.
• the intensity of the brake assist force therefore gradually decreases, which allows the driver to better dose the end of its braking and not to have the brake pedal 20 which comes to tap against its foot.
• This deactivation allows the driver wishing to modulate his deceleration not to have to completely remove his foot from the brake pedal 20 to deactivate the SFU emergency braking strategy, then to press the pedal 20 again to brake less forcefully.
• the progressive deactivation of the emergency braking strategy SFU is generally followed by a sudden deactivation, the force exerted by the driver on the brake pedal 20 becoming very low.
• the electronic unit 58 is capable of storing initial values which allow it to disregard the measurements made by the various sensors when the vehicle 10 is stopped, in particular during stops due to traffic conditions.

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• Engineering & Computer Science (AREA)
• Transportation (AREA)
• Mechanical Engineering (AREA)
• Regulating Braking Force (AREA)
• Braking Systems And Boosters (AREA)

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• 2001
  • 2001-01-19 FR FR0100715A patent/FR2819768B1/fr not_active Expired - Fee Related
• 2002
  • 2002-01-18 WO PCT/FR2002/000205 patent/WO2002057123A1/fr active Application Filing
  • 2002-01-18 EP EP02708402A patent/EP1353829A1/fr not_active Withdrawn
  • 2002-01-18 JP JP2002557819A patent/JP2005506235A/ja active Pending

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