FR2939389A3 - Motor vehicle speed controlling method, involves performing closed loop control of speed and acceleration of vehicle by activating braking device, when speed is less than speed threshold and slope of ground is greater than slope threshold - Google Patents

Abstract

The method involves performing closed loop control of speed and acceleration of a motor vehicle by activating a braking device (5) of the motor vehicle, when the speed of the vehicle is less than a speed threshold and a slope of the ground is greater than a slope threshold. The speed control operation is deactivated by an action of a driver on a brake control unit and/or on an acceleration control unit. Independent claims are also included for the following: (1) a computer readable data medium comprising a software unit with instructions for implementing a motor vehicle speed control method (2) a system for controlling speed of a motor vehicle driven by gravitation in a slope.

Description

The invention relates to a system for regulating the speed of a motor vehicle comprising, for example, a braking device mechanically decoupled from the braking control. It relates in particular to a control method implemented by such a control system. It also relates to a data carrier comprising means for implementing such a control method. In addition to the many safety features such as Antilock Braking System (ABS) and Electronic Stability Program (ESP) Electronic Stability Program (ESP) ), or the Emergency Brake Assist (AFU), the car manufacturers offer so-called comfort services, such as hill start assistance, or the control of the deceleration of the vehicle according to its state.

These services are made possible by the development on vehicles of braking devices (known as by-wire devices), in which the brake pedal actuated by a driver and the means for actuating the brakes are completely decoupled mechanically.

The invention which is the subject of the present application makes it possible in particular to control the speed of a vehicle in a slope. It is applicable to vehicles equipped with decoupled braking or an electric motor (electric or hybrid vehicles). The purpose of this service is to ensure, by automatically actuating the brakes, a constant speed of the vehicle on a downward slope, that is to say a slope that causes the vehicle to move forward when the vehicle is in a gear ratio. forward or slope driving the vehicle backward when the vehicle is in a reverse gear. This can be very useful, for example, if the driver needs to make a parking maneuver (slot type) on a slope.

In the context of a vehicle equipped with an electric motor, the braking which carries out the speed control can be done by the electric motor. This allows you to recover energy to recharge a battery.

Application FR 2 862 930 discloses a method for regulating, on a slope, the acceleration of a vehicle equipped with a decoupled braking system. The method is based on an open-loop estimation of the braking force necessary to compensate for the acceleration due to the slope that is measured or estimated, the mass of the vehicle being also measured or estimated.

This solution has drawbacks: it is necessary to measure or estimate the slope of the ground and the mass of the vehicle to implement it. The settings of this control method are not direct and a saturation of the brake control must be implemented downstream of the control means.

The object of the invention is to provide a speed control method overcoming the disadvantages mentioned above and improving the control methods known from the prior art. In particular, the invention provides a simple control method free of certain measurements and estimates, presenting adjustment parameters that are simple to implement and whose system implementing it makes it possible to take into account a saturation of the control of braking.

The method makes it possible to regulate the speed of a motor vehicle driven by the gravitation in a slope. The speed regulation being ensured by MS \ REN 118FR.dpt the action of a braking device of the motor vehicle. The method is characterized in that the speed regulation is of the closed-loop type.

The regulation may comprise a closed internal loop for regulating the acceleration of the motor vehicle. The method may be deactivated by the action of a conductor on a brake control member and / or by the action of a conductor on an acceleration control member. The method may only be activated if the speed of the motor vehicle is below a speed threshold.

The method may be activated only if the slope of the ground on which the motor vehicle is located is greater than a slope threshold. According to the invention, a data medium readable by a computer comprises software means for implementing the steps of the regulation method defined above. According to the invention, a system for regulating the speed of a motor vehicle driven by the gravitation in a slope, comprising a braking device of the vehicle, is characterized in that it comprises hardware and / or software means of implementation of the control method 25 defined above. The system may include a closed-loop type speed controller. The cruise control may comprise a closed loop for acceleration control of the motor vehicle. According to the invention, a motor vehicle comprises a regulation system defined above.

The accompanying drawings represent, by way of example, an embodiment 5 of the control method according to the invention and an embodiment of a control system according to the invention.

Figure 1 is a diagram of an embodiment of a control system according to the invention. Figure 2 is a diagram of a computer controlling a braking device of a motor vehicle according to the control method object of the invention.

FIG. 3 is an exemplary embodiment of a first functional block of the computer.

FIG. 4 is an exemplary embodiment of a second functional block of the computer. Figure 5 is an exemplary embodiment of a third functional block of the computer.

Figure 6 is an exemplary embodiment of a fourth functional block of the computer.

Figures 7 and 8 are diagrams illustrating the principle of regulation according to the invention.

Fig. 9 is a Bode diagram of a corrected open loop and a closed loop according to the invention. FIG. 10 is a Bode diagram of the open loop corrected for different values of regulation parameters of regulation.

FIG. 11 is a temporal diagram of the evolutions of the signals of set speed and acceleration, of the actual vehicle speed signal and of the intensity of the braking action obtained on a vehicle equipped with a speed control system according to FIG. the invention under particular conditions.

The control system 9 shown in FIG. 1 comprises at least one braking device 5 such as an electromechanical brake caliper receiving brake force intensity instructions to be applied to a wheel. The caliper is electromechanical, however it can also be of another technology such as electrohydraulic technology. The control system also comprises a computer 3, whose function is to develop the intensity instructions of the braking action to be sent to the braking device 5 from signals received by the computer. The control system is preferably part of a mechanical decoupling braking system, that is to say that no mechanical action exerted on the brake control member is transmitted to the wheels to brake them. The invention is also applicable to vehicles equipped with an electric motor (electric or hybrid vehicles).

The braking action intensity settings may comprise a braking intensity value such as a braking torque value at the level of the wheel considered. Alternatively, the braking action intensity settings may include any other value corresponding to or capable of being reduced to a braking action intensity such as a pinch force value of a brake disk or an electric supply value. an electromechanical caliper. MS \ REN118FR.dpt On the basis of the signals transmitted to the computer 3, the latter develops, through hardware and / or software contained in the computer, a braking command signal. This signal comprises a set value of intensity of the braking action to be implemented by the stirrups or stirrups. Thus, the computer comprises hardware and / or software means for implementing the regulation method according to the invention and, therefore, hardware and / or software means for implementing a method of operating the regulation system according to the invention. the invention. These means may comprise the blocks and sub-blocks illustrated in FIGS. 2 to 6 and described below. The computer comprises calculation means for calculating a set value of intensity of the braking action to be implemented by the braking device and for calculating the evolution over time of this setpoint value. The software means may comprise computer programs.

As will be seen below, from the description of one embodiment of the regulation method according to the invention, the regulation method according to the invention implements closed loop type speed regulation. Advantageously, at any time the driver can deactivate the function and regain control of the vehicle either by operating the brake pedal or by operating the accelerator pedal. The structure of a computer implementing an embodiment of the regulation method according to the invention is described below with reference to FIG. 2. The embodiment of the regulation method according to the invention is described. through this description.

The control system and, in particular, the computer 3, receives the following information:

Vehicle: is the longitudinal speed value of the vehicle (for example obtained from speed sensors of the vehicle wheels); Slope Estimee: is the estimated value of the slope of the ground on which the vehicle is. The estimate is made by a specific algorithm. This estimate, if available, is used to manage the automatic activation of the regulation function but it is not used as such in the control system to establish control; Flag Ped Acc: is a logic signal that is high if the driver presses the accelerator pedal and is in the low state otherwise; Flag Ped Brake: is a logic signal that is high if the driver presses on the brake pedal and is in the low state otherwise.

The calculator has four main blocks.

A first block 11 manages the activation and deactivation of the regulation. It outputs a Flag Activation logic signal which is high when the regulation is active, and is in the low state otherwise. This signal drives the activation of regulation means.

One possible embodiment of the first block is described below with reference to FIG.

According to this embodiment, the following signals attack the first block: V Vehicle; Slope Estimee; Flag Ped Acc; Fia g Ped Brake. MS \ REN 118EN.dpt A Flag Activation output signal is obtained according to the following logic: the Flag Activation signal is high under the following cumulative conditions: the value of the signal V VEHICLE is less than a threshold Threshold Speed Activation, and the value of the Slope Estime signal is greater than a Threshold Slope Activation threshold, and the Flag Ped Acc logic signal is low, and the Flag Ped Brake logic signal is low. Flag Activation signal is low in other cases.

With Threshold Speed Activation: a setting parameter that represents the speed value below which control is activated, eg 20 km / h, Slope threshold Activation: a setting parameter that represents the slope value (down) at above which the regulation is activated, for example 10%.

The preceding logic is for example implemented thanks to an AND logic gate 21.

The speed regulation is therefore active when the slope (downward, that is to say driving the vehicle in the direction where tends to drive the engine with gear ratio considered) soil on which is located the vehicle is above the Threshold Slope Activation threshold, the speed is below the Threshold Speed Activation threshold and the driver does not press the accelerator pedal or the brake pedal. Note that if the driver depresses the accelerator pedal (the Flag Ped Acc signal is high) or the brake pedal (Flag Ped Brake signal is MS \ REN 118FR.dpt high ) then the Flag Activation signal goes low and the regulation is deactivated allowing the driver to accelerate or brake freely.

The activation conditions presented in this paragraph are not the only 5 possible ones. The Flag Activation signal can indeed be obtained in a different way from that described here without affecting the architecture of the invention and the internal structure of the other blocks.

A second block 12 makes it possible to estimate the acceleration of the vehicle, it therefore comprises means for estimating the acceleration of the vehicle.

A very simple possible realization of this second block is shown in FIG.

This block receives as input the speed signal V Vehicle and outputs an estimate of acc acc acceleration of the vehicle. This last signal is the derivative of the V signal Vehicle filtered by a low-pass filter for example a first-order filter having a Omega filtering cutoff pulse (omega_filtering being a setting parameter): Acc_Est (s) = 1+ s Omega_filtrage 20 • V_Vehicle (s) where s is the Laplace variable.

Such an embodiment comprises an integration means 31.

Other estimates of vehicle acceleration different from that proposed in this example are also possible. This does not impact the architecture of the invention and the internal structure of the other blocks.

A third block 13 makes it possible to define an acceleration setpoint 30 making it possible to slave the speed of the vehicle to the desired setpoint. It MS \ REN 118FR.dpt realizes, with a fourth block 14, a closed-loop regulator of the speed of the vehicle.

An embodiment of this third block is shown in FIG. 5. The third block receives the following signals and adjustment parameters: V Vehicle, V Setpoint which is a setting value defining the set speed at which the vehicle must be moved, 10 Margin which is a setting parameter of the control system, B Passing which is a setting parameter of the control system. Its value specifies the bandwidth (radish) of closed-loop speed control when the Margin parameter is equal to 1, and 15 Dec Max which is a setting parameter and which defines the minimum acceleration that is the maximum allowable deceleration for the vehicle. In other words, Dec Max is a saturation parameter of the deceleration of the vehicle when the regulation process is active. Dec Max has a negative value. This block produces, at its output, an acceleration signal Ace Setpoint which represents the setpoint for an internal loop for regulating the acceleration of the vehicle. The signal is for example defined by the following relation: Acc_Consigne = max [Dec_Max, Acc_Consigne_Av_Sat] where Ace Setpoint Av_Sat is defined by the following relation: Acc_Consigne_Av_Sat = 1.41 x Mage x B_Passante x (V_Consigne - V_Vehicule) 30 A fourth block 14 realizes a closed-loop servo of the acceleration of the vehicle to the setpoint generated by the third block. This MS \ REN118FR.dpt fourth block carries, with the third block, a closed-loop regulator of the speed of the vehicle.

An embodiment of this fourth block is shown in FIG. 6. The fourth block receives the following signals and adjustment parameters: Acc Setpoint: the acceleration setpoint signal established at the output of the third block; Acc East: the estimated acceleration signal set at the output of the second block; Flag Activation: the activation signal of the regulation set at the output of the first block; B Passive: The setting parameter previously defined.

This fourth block produces at output a braking control signal F BRK, that is to say braking intensity, which is the control variable of the regulator. This signal is defined by the relation:

F_BRK = my *, F_BRK Before_Sat]

This signal is thus obtained by saturating at 0 (from below) the signal F BRK Avant Sat obtained thus:

F_BRK_Avan t_Sat = -B_Passante x Mass Vehi cule x f [Acc_Consig ne (t) - Acc_Est (t)] dt (1) The value of the signal F BRK is therefore positive.

The integration of the error signal [Acc_Consigne (t) -Acc_Est (t)] is made only when a RESET logic signal established in FIG. 6 is in the state

MS \ REN118EN.dpt 20 25

12 down. When the logic signal RESET is high, the output of an integrator 43 is reset.

The RESET logic signal is obtained from the logic signal Flag_Activation and a logic signal Flag_Desactivation as follows:

The RESET logic signal is high if the Flag_Desactivation signal is high or the Flag_Activation logic signal is low. The RESET logic signal is in the low state in the other cases. This logic is implemented through an OR logic gate 41.

The logic signal Flag_Desactivation is obtained according to the following logic: The logic signal Flag_Desactivation is in the high state if the value of the signal F_BRK Before Sat is less than or equal to zero and if the quantity [Acc_Consigne (t) ùAcc_Est (t)] is greater than zero. The logic signal Flag_Desactivation is low in other cases. This logic is implemented thanks to an AND logic gate 42.

The signal Fiag Deactivation is therefore in the high state when the estimated acceleration of the vehicle Acc East is lower than the set acceleration Acc Setpoint and the control variable before saturation at zero (F BRK Before Sat) is negative or zero. Indeed, in this case, the regulation would involve a negative value of braking force (that is to say a driving force) which is of course not achievable by the action of a braking device. The transition to the high state of the logic signal Flag Disabling thus resets an integrator 43 when the control variable is saturated, thereby avoiding the phenomenon known as wind-up.

The F BRK signal obtained at the output constitutes a force request from MS \ REN118FR.dpt total braking of the vehicle making it possible to slave its speed to the setpoint value V Setpoint. It constitutes the control variable of the regulation. From equation (1), it is possible to write the transfer function Racc (s) of the regulator of the internal regulation loop in acceleration carried out by the fourth block 14: () F BRK - B_Passante x Mass_Vehicule Rami s - [ Acc_Consigne (t) - Acc_Est (t)] s It is considered that the braking intensity setpoint F BRK is applied with a much faster dynamic range than the closed-loop control. We can then make the following simplifying hypothesis:

It is considered that the brake current setpoint F_BRK is equal to the total braking action actually applied to the vehicle by the braking device. Under this hypothesis HYP 1, the transfer function G (s) of the system to be regulated is given by: G (s) = V_Vehicule - 1 1 F_BRK Mass Vehi cules s 20 with s the Laplace variable.

The control loop can then be represented as in FIG. 7.

It is also assumed that the estimation of vehicle acceleration is much faster than closed-loop control. This amounts to imposing that the value of the Omega Filtering parameter of the block 12 is much greater than the regulation cutoff pulse. We can then make the simplifying assumption that the estimated acceleration of the vehicle is equal to the actual acceleration of the vehicle Acc Veh. MS \ REN 118EN.dpt10 Under this hypothesis HYP 2, it is possible to simplify the control loop of the

Figure 7 as shown in Figure 8. In this figure, one can easily

note the presence of an internal regulation loop in acceleration. The transfer function of the internal closed loop is: B Passing s _ 1 1+ B_Passante 1+ ss B_Passante The transfer function of the external corrected open loop of Figure 10 8 is then given by: L (s) - B_Passante x Mage x 1.41 (s) - B_Passante x Margin x 1.41 1 s Fii, c - ss 1+ B_Passante Figure 9 shows the Bode diagrams of the corrected open loop 15 L (s) (solid line) and closed loop L (s) (in phantom) when the 1 + L (s) parameter Margin equals 1. Figure 10 shows the Bode diagrams of the corrected open loop L (s) for different values of the parameters B Passing and Margin . From these two figures (FIG. 9 and FIG. 10), the following remarks are made:

1. The setting parameter of the Passing System B corresponds to the control switch-off pulse when the Margin parameter is 1. 25 2. When the Margin parameter is 1, the phase margin is 45 ° and this for any value of parameter B Passing. MS \ REN118EN.dpt Font (s) = 3. For values of Margin less than 1, the regulation bandwidth is less than B _Passante and the phase margin is greater than 45 °. If the value of the parameter Margin decreases then the bandwidth of the regulation decreases and the phase margin increases. The development of the system can therefore be done intuitively through the two parameters B Passing and Margin.

It will be recalled that, in order for the initial hypotheses HYP 1 and HYP 2 to be reasonable, the regulation bandwidth must be chosen much slower than the dynamics of: 1. realizing the setpoint F BRK by the braking device; 2. estimation of the acceleration of the vehicle (this amounts to requiring that the value of the Omega_Filtering adjustment parameter of the block 12 is much greater than the regulation cut-off pulse).

Figures 10 and 11 show an example of result obtained on vehicle. The figure at the top shows the speed of the acceleration setpoint signals Acc Setpoint and the speed of the vehicle V Vehicle when a vehicle speed is chosen V Setpoint equal to 4 km / h.

The bottom figure shows the appearance of the control variable of the braking device F BRK as a function of time.

The proposed solution is characterized by: a closed-loop regulator that does not use any estimate of the slope or mass of the vehicle; direct use of intuitive setting parameters; achieving the saturation of the control at the level of the regulator. MS \ REN 118FR.dpt5

Claims (10)

Claims: 1 Method for regulating the speed of a motor vehicle driven by gravitation in a slope, the speed regulation being ensured by the action of a device (5) for braking the motor vehicle, characterized in that the Speed regulation is closed loop type. 2. Control method according to claim 1, characterized in that the regulation comprises a closed inner loop of acceleration control of the motor vehicle. 3. Control method according to claim 1 or 2, characterized in that it is deactivated by the action of a conductor on a brake control member and / or by the action of a conductor on a control member. acceleration control. 4. Control method according to one of the preceding claims, characterized in that it is activated only if the speed of the motor vehicle is less than a speed threshold. 5. Control method according to one of the preceding claims, characterized in that it is activated only if the slope of the soil on which the motor vehicle is located is greater than a slope threshold. 6. Support (3) data readable by a computer comprising software means for implementing the steps of the control method according to one of the preceding claims. 30 7. System (9) for regulating the speed of a motor vehicle driven by the gravitation in a slope, comprising a device for braking the vehicle, characterized in that it comprises means ( 3, 11, 12, 13, 14) and / or software for implementing the control method according to one of claims 1 to 5. 8. System according to claim 7, characterized in that it comprises a closed-loop type speed governor. 9. System according to claim 8, characterized in that the cruise control comprises a closed loop of acceleration control of the motor vehicle. 10. Motor vehicle comprising a control system according to one of claims 7 to 9. MS \ REN 118FR.dpt