DE102005053863A1 - Stabilizing process for vehicle involves actuator being controlled so that travel dynamic value for instantaneous time point takes on that of conversion value - Google Patents

Abstract

The stabilizing process involves reporting a travel dynamic value corresponding with the wish of the driver (1) as the driver's desired travel dynamic value (2). From these values (2) over a period of time, a conversion dynamic value is reported, representing a practical time run of the travel dynamic value itself. The actuator (7) is controlled so that the travel dynamic value for an instantaneous time point takes on that of the conversion value for an instantaneous time point.

Description

Known ABS control methods are based on slip control. there becomes a setpoint for the Wheel slip generated by a PID controller shall be. The actual slip swings in many cases its setpoint and it is alternately brake pressure on and removed.

From the DE 40 34 814 A1 An antilock control system is known which has phases of control to a desired slip value and phases of brake pressure control in the event of instabilities of the wheel. The nominal slip is determined from a determined maximum friction coefficient and the applied brake pressure from the slip value when the maximum friction coefficient occurs.

Advantages of invention

• – eine den Fahrerwunsch bzgl. einer Fahrdynamikgröße repräsentierende Fahrerwunschfahrdynamikgröße ermittelt wird,
• – aus der Fahrerwunschfahrdynamikgröße der zeitliche Verlauf einer Umsetzfahrdynamikgröße, welche einen realisierbaren zeitlichen Verlauf derselben Fahrdynamikgröße repräsentiert, ermittelt wird und
• – bei dem ein Aktor so angesteuert wird, dass die Fahrdynamikgröße zum momentanen Zeitpunkt den Wert der Umsetzfahrdynamikgröße zum momentanen Zeitpunkt, insbesondere im Rahmen gegebener Toleranzen, annimmt.

The invention relates to a method for stabilizing a vehicle during a braking process or an acceleration process, in which

• A driver request dynamic variable representing the driver's request with respect to a vehicle dynamics variable is determined,
• From the driver's request driving dynamics variable the time course of a Umsetzfahrdynamikgröße, which represents a realizable time course of the same driving dynamics size, is determined and
• - In which an actuator is controlled so that the vehicle dynamics size at the moment the value of Umsetzfahrdynamikgröße at the current time, in particular in the context of given tolerances, assumes.

Thereby, that only feasible temporal courses of the driving dynamics size considered be, results in a reliable Stabilization of the vehicle and a reduction in valve actuation in the brake circuit.

A advantageous embodiment of the invention is characterized in that that it is the vehicle dynamics amount to the vehicle longitudinal deceleration during a Braking process is. The vehicle longitudinal deceleration is a crucial one Size, if it's about the shortening the braking path goes.

A advantageous embodiment of the invention is characterized in that that the future Time course of Umsetzfahrdynamikgröße determined and continuously is updated. As a result, a constant adaptation of the Umsetzfahrdynamikgröße to the current circumstances such as the road friction coefficient or the driver's request.

A advantageous embodiment of the invention is characterized in that that the actuator is a wheel brake.

A advantageous embodiment of the invention is characterized in that that tire parameters estimated in the ascertained chronological course of the conversion dynamic quantity and / or estimated Vehicle parameters and / or the vehicle condition, received. Thereby finds an adaptation of the invention to the respective vehicle or the respective tire or the dynamic vehicle state.

A advantageous embodiment of the invention is characterized in that that from the time course of Umsetzfahrdynamikgröße a Input tax quantity determined is, which enters into the control of the actuator. By the pilot control the dynamic behavior is improved compared to a pure regulation, because not only to deviations from the setpoint is reacted, but already suitably controlled. This is especially true in the Braking phase, due to the high vehicle speed the biggest optimization potential lies.

A advantageous embodiment of the invention is characterized in that that from the time course of Umsetzfahrdynamikgröße additionally at least determined a different from the pilot control variable target size is, which also enters into the control of the actuator. These Size can by a suitable return to Correction of input tax quantity used become.

A advantageous embodiment of the invention is characterized in that that the input tax quantity is a Target braking torque is.

A advantageous embodiment of the invention is characterized in that that the target size is a Setpoint speed is. Wheel speeds are by in the vehicle anyway existing wheel speed sensors easy and inexpensive to capture.

A advantageous embodiment of the invention is characterized in that that from the difference between the target size and the corresponding momentary present actual value of the same physical quantity, in particular by means of stable Recycling e.g. of a PID controller determines a correction value for the pilot control variable becomes.

A advantageous embodiment of the invention is characterized in that the actuator is controlled in such a way that with respect to the braking process the sum of the pre-control value and the correction value in the actuator or is realized by the actuator.

A advantageous embodiment of the invention is characterized in that that the input tax quantity from the Time course of Umsetzfahrdynamikgröße by means of an inverse system is determined.

A advantageous embodiment of the invention is characterized in that that in determining the input tax quantity, the determined current Vehicle longitudinal speed received.

A advantageous embodiment of the invention is characterized in that that in the determination of the pilot quantity additionally estimated tire parameters and / or estimated Vehicle parameters and / or estimated Enter vehicle sizes.

A advantageous embodiment of the invention is characterized in that that the driver's request dynamic quantity from the pedal travel and / or the prevailing at the output of the master cylinder form is determined. Thus, the invention is also for use in the context of brake-by-wire systems particularly suitable.

A advantageous embodiment of the invention is characterized in that that it is the time course of Umsetzfahrdynamikgröße to a continuous and at least once continuously differentiable function is. The necessary number of continuous derivatives depends on the dynamic system properties from.

A advantageous embodiment of the invention is characterized in that that the vehicle dynamics quantity is the vehicle longitudinal acceleration is.

A advantageous embodiment of the invention is characterized in that that the actuator is a wheel drive.

The the latter two embodiments allow the use of the Invention in the context of a traction control system.

Further the invention comprises a device for carrying out a the procedure given above.

The advantageous embodiments of the method according to the invention are expressed as advantageous embodiments of the device according to the invention and vice versa.

drawing

The drawing consists of the 1 to 3 ,

1 shows the structure of an embodiment of the device according to the invention or the method according to the invention.

2 shows the course of Sollraddrehzahlen at different speeds initiated braking.

3 shows the course of Sollradbremsmoments at different speeds initiated Bremsvorgän gene.

embodiments

• – Optimierung des Bremswegs bzw. der Traktion,
• – Verringerung der Ventilbetätigungen und damit der Pedalrückwirkung und der Geräuschentwicklung durch die Vermeidung von Radschwingungen sowie
• – Stabilität gegenüber Reibwertsprüngen.

The invention relates to a model-based wheel control in the case of driving and braking, in particular of an ABS system, taking into account the dynamic behavior of the actuators and the tires with the following objectives:

• - Optimization of the braking distance or the traction,
• - Reduction of valve actuation and thus the pedal reaction and noise by avoiding wheel vibrations and
• - Stability to Reibwertsprüngen.

These Goals become by the establishment of a regulation as a Trajektorienfolgeregelung achieved, which consists of an output feedback and a setpoint value assignment composed in the form of trajectories. The stability of the wheels, in particular The prevention of blocking or spinning, is thereby of considered in advance in the setpoint specification.

• – eine Sollwertbildung einschließlich Trakjektorienplanung,
• – dem inversen System,
• – stabilisierenden Rückführungen und
• – optional einer Reifen- und/oder Fahrzeugparameterschätzung

zusammen.The invention thus provides a model-based method for stability control, for example the control of the longitudinal acceleration of a motor vehicle during braking taking into account the transverse stability (ie no break-out) of the vehicle and the stability of the individual wheels (ie no blocking). This method is based in particular on the basis of an inverse dynamic description of the controlled system, which is composed of vehicle, brake actuator, drive, wheel and tire. The control scheme is in particular made

• - a setpoint calculation including trajectory planning,
• - the inverse system,
• - stabilizing returns and
• Optionally a tire and / or vehicle parameter estimate

together.

• – auf das dynamische Verhalten der Regelstrecke Rücksicht genommen, indem hinreichend oft stetig differenzierbare und damit realisierbare Sollzeitverläufe für die Fahrzeugverzögerung als Solltrajektorien vorgegeben werden und Totzeiten von Aktoren kompensiert werden und
• – es wird ein Blockieren der Räder ausgeschlossen und die maximale Längskraft abgesetzt.

In the setpoint formation and the trajectory planning for the vehicle deceleration and their time derivatives is

• - taken into account the dynamic behavior of the controlled system by sufficiently steadily differentiable and thus realizable setpoint time curves for the vehicle deceleration are specified as desired trajectories and dead times are compensated by actuators and
• - It is excluded blocking the wheels and deposed the maximum longitudinal force.

With the repatriation of the Wheel speeds and consideration the current vehicle speed when calculating the feedforward control via a Inverse system takes place in this way, a fast compensation of friction value changes.

With Help of the inverse system becomes from the desired delays, the associated time derivations and the current vehicle speed, a desired braking torque, the is connected as feedforward, calculated. In the conversion the target delay in four desired longitudinal forces for the individual Wheels can the transverse stability of the vehicle (i.e. Breaking out of the vehicle) and the normal force distribution (i.e., possible pitching movements and rolling movements or rolling movements). Furthermore become nominal curves for conditions (e.g. for the Wheel speeds) or states dependent Sizes calculated, with the help of a return to Stabilization of Trajektorienfolge be used.

The repatriations measured or determined quantities, for example via a PID controllers are used to stabilize the trajectory sequence against disturbances and compensation of model errors or model inaccuracies. Suitable as feedback variables For example, the wheel speeds.

optional can still make an estimate important tire and vehicle parameters are carried out, which increases the robustness and accuracy of the scheme is further increased.

• – durch die Berücksichtigung der Zeitkonstanten und Totzeiten (d.h. dem dynamischen Verhalten) der Regelstrecke werden unnötige Ventilbetätigungen minimiert und damit die Pedalrückwirkung und die Geräuschentwicklung reduziert.
• – Reibwertsprünge werden direkt, d.h. ohne zusätzliche Algorithmen, kompensiert.
• – es findet eine Verringerung des Bremswegs insbesondere in der Anbremsphase statt.
• – Verbesserung des Robustheitsverhaltens.
• – Vereinfachung der Applikation (physikalische Parameter).
• – das Verfahren eignet sich direkt für die Realisierung in einem brake-by-wire-System.
• – das Regelschema kann beispielsweise auch für den Antriebsfall im Rahmen einer ASR-Regelung adaptiert werden.

This results in the following advantages:

• - By taking into account the time constants and dead times (ie the dynamic behavior) of the controlled system unnecessary valve actuations are minimized and thus reduces the pedal feedback and noise.
• - Friction jumps are directly, ie compensated without additional algorithms.
• - There is a reduction of the braking distance, especially in the braking phase instead.
• - Improvement of the robustness behavior.
• - Simplification of the application (physical parameters).
• - The method is suitable directly for implementation in a brake-by-wire system.
• - The control scheme can for example be adapted for the drive case in the context of ASR control.

The basic principle of the invention is in 1 shown. This characterizes Block 1 the driver and in block 2 there is a setpoint. This is in block 2 For example, in the context of an ABS control from variables such as the brake pedal travel or the brake pedal position or the present at the output of the master cylinder form determines the driver's request representing the desired deceleration of the vehicle. The determination of the desired deceleration can take place, for example, via a characteristic map.

• – der Sollzeitverlauf (Solltrajektorie) für die Fahrzeugverzögerung hinreichend oft stetig nach der Zeit ableitbar und insbesondere auch realisierbar ist,
• – die maximale Längskraft abgesetzt wird und
• – auftretende Totzeiten kompensiert werden.

Subsequently takes place in block 3 a trajectory planning takes place. There, the predetermined by the driver target deceleration is re-planned and possibly limited, so that

• The setpoint time course (desired trajectory) for the vehicle deceleration is sufficiently derivable and, in particular, also realizable over time,
• - The maximum longitudinal force is discontinued and
• - occurring dead times are compensated.

This trajectory planning is predictive and provides a driving dynamics implementable longitudinal acceleration course. In the trajectory planning can also block 6 derived tire and / or vehicle parameters, such as tire stiffness, tire radii or vehicle mass.

• – die Sollradbremsmomente, die als Vorsteuerung aufgeschaltet werden und
• – die Sollraddrehzahlen für den PID-Regler 5

bestimmt. Die Fahrzeuglängsgeschwindigkeit kann gemessen, aus den Raddrehzahlen ermittelt oder geschätzt werden.The in block 3 determined feasible target trajectory for the vehicle deceleration and their time derivatives go as an input signal in block 4 one. In block 4 With the aid of an inverse system, the target trajectory and its time derivatives as well as the current vehicle longitudinal speed are calculated

• - The Sollradbremsmomente, which are switched on as pilot control and
• - the desired wheel speeds for the PID controller 5

certainly. The vehicle longitudinal speed can be measured, determined from the wheel speeds or estimated.

The Distribution of the delay request on the wheels, i.e. the Sollradbremsmomente, taking into account the driving stability, i. the yawing motion of the vehicle and / or the normal force distribution (i.e. the Radaufstandskräfte), respectively.

there can be optional on metrics, such as e.g. the yaw rate and transverse or longitudinal accelerations, and up Estimates, how e.g. the road friction coefficient, resorted to become.

• – Fahrzeug,
• – Rad,
• – Reifen bzw. Kontaktkräften und
• – den Bremsaktoren und ggf. dem Antrieb

dar. Die Systembeschreibung erfolgt dabei auf der Grundlage der physikalischen Regelstreckeneigenschaften mit Hilfe physikalischer Parameter.That in block 4 used inverse system represents a differential algebraic description of the dynamic behavior of

• - vehicle,
• - wheel,
• - Tires or contact forces and
• - The brake actuators and possibly the drive

The system description is based on the physical control path properties using physical parameters.

High deceleration rates can cause wheels to be driven for a short time after braking in order to ensure wheel stability, ie no jamming. This is a consequence of considering the dynamic tire behavior by the inverse system. In these cases, in addition to the braking torque and a drive torque must be realized. This is in the 2 recognizable by the occurrence of negative braking torques. A negative braking torque corresponds to a drive torque.

The in block 4 determined Sollradbremsmomente become an addition block 50 fed in the block 4 determined Sollraddrehzahlen become an addition block 40 fed.

In block 40 will be the difference between in block 4 determined Sollraddrehzahlen and the actual wheel speeds determined. This difference becomes a PID controller 5 fed. By 5 there is a linear PID feedback and a stabilization of the Trajektorienfolge for the wheel speed. The output of the PID controller 5 will be in block 50 is added to the precontrol calculated using the inverse system. This gives Radbremsmomente which are to be realized by brake actuators, possibly with the help of a subordinate control, sufficiently accurate. In the event that the Sollraddrehzahlen the actual wheel speeds correspond, supplies the subtraction block 40 the output signal 0 and it finds in block 50 also no correction of Sollradbremsmomente instead.

In block 5 This is done so that the determination of correction values for in block 4 determined Sollradbremsmomente. For example, disturbances in the coefficient of friction of the road surface are noticeable in a change in the wheel speeds. Thus, the Sollraddrehzahlen no longer correspond to the actual wheel speeds, in block 40 results in a non-zero output value and the PID controller 5 thus provides a correction moment, which in block 50 is added to the Sollradbremsmoment.

In block 6 a parameter estimation takes place. There, to improve the robustness behavior and the accuracy of the control optional estimates of the most important vehicle and tire parameters such as vehicle mass, tire radius, tire stiffness, coefficient of friction, etc. are provided. These parameters then go into trajectory planning 3 and the system inversion block 4 one. Instead of the parameter estimation, in block 6 also suitable default parameters can be stored.

block 7 describes the controlled system, consisting of brake actuator, possibly drive, vehicle, wheel, tire (consideration of the contact forces) and the sensors used.

The inverse system description in block 4 will be explained below with reference to an embodiment. This is based on a ¼-vehicle model, ie a limited to a wheel vehicle model based. This model comprises a wheel together with an inertia moment associated therewith, a mass for the vehicle body and a contact model describing the contact between the tire and the roadway

through of a concentrated LuGre tire model is a dynamic one Contact force calculation.

Dabei bedeuten:

m

= Fahrzeugmasse,

v

= Fahrzeuggeschwindigkeit,

F_n

= Normalkraft,

σ₀

= Reifensteifigkeit,

J

= Reifenträgheitsmoment

ω

= Raddrehzahl,

z

= mittlere Bürstenverformung des Reifens,

M_b

= Bremsmoment,

r

= Reifenradius,

κ

= Reifenparameter,

t

= Zeit.

For this vehicle model and the tire model, the following equations apply: mv. (t) = -F n σ 0 z (t) (1) Jω. (T) = rF n σ 0 z (t) - M b (t) (2)

Where:

m

= Vehicle mass,

v

= Vehicle speed,

F _n

= Normal force,

σ ₀

= Tire stiffness,

J

= Tire moment of inertia

ω

= Wheel speed,

z

= average brush deformation of the tire,

M _b

= Braking torque,

r

= Tire radius,

κ

= Tire parameters,

t

= Time.

at The tire model used is a brush model. This is the road contact with the help of elastic brushes described. Accurate modeling requires distributed viewing the brushes over the Tire contact area. However, the distributed model can be a concentrated one Derive model in which the brushes by integration or Averaging over the laces are combined into a resulting brush.

The in (3) occurring nonlinear function g depends on the road friction coefficient from. It is possible and makes sense to use an estimate for the road friction coefficient in the system inversion.

From equation (1), by dissolving to z and forming the time derivative:

By substituting the equations (4) and (5) in (3), the following is obtained for the wheel speed and acceleration: ω (t) = f (v (t), v. (t), v. (t)) (6) ω. (t) = f (v (t), v. (t), v. (t), v ... (t)) (7)

The braking torque is finally obtained from equation (2) with (4) and (7): M b (t) = -r * m * v. (t) -f (v (t), v. (t), v. (t), v ... (t)) (8) M b (t) = f (v (t), v. (t), v. (t), v ... (t)) (9)

Equation (9) describes the inverse system for a vehicle described by a 1/4 vehicle model. With the aid of equation (9), by using the desired trajectory for the vehicle deceleration and its time derivatives, the precontrol for the braking torque is obtained. The desired wheel speed is obtained with equation (6), where the vehicle speed is from the output of block 7 to block 4 is returned and for the higher derivatives, the setpoints are used.

• – in 2 das Sollradbremsmoment Mb_d und
• – in 3 die Solldrehzahl Omega_d

aufgetragen.In the 2 and 3 the time courses of different quantities are plotted over the time t. In each case the time t is plotted in the abscissa direction and in the ordinate direction

• - in 2 the Sollradbremsmoment Mb _d and
• - in 3 the setpoint speed Omega _d

applied.

there each becomes a transition from an instant Vehicle, i. Target vehicle deceleration = 0, considered at a constant maximum value. The respective ones Rise times are 20 ms, 30 ms, 40 ms and 50 ms and are in the unit milliseconds entered as parameters of the respective gradients.

It It can be seen that at steep climbs (e.g., within 20 ms, see curves) strong vibrations of the Sollraddrehzahl and the Sollradbremsmoments calculated and desired are while at flat climbs (for example 50 ms, see curves) the driver's request almost can be followed.

Claims (19)

Method for stabilizing a vehicle during a braking process or acceleration process, in which - a driver's desired dynamic size that represents the driver's request with respect to a driving dynamics variable is determined ( 2 ), the temporal course of a Umsetzfahrdynamikgröße, which represents a realizable time course of the same driving dynamics size, is determined from the driver's request dynamic quantity ( 3 ) and in which an actuator is controlled such that the vehicle dynamics quantity at the moment ( 2 ) the value of the Umfahrfahrdynamikgröße at the moment ( 3 ). A method according to claim 1, characterized in that it is in the driving dynamics size ( 2 ) is the vehicle longitudinal deceleration. A method according to claim 1, characterized in that the future time course of the Umsetzfahrdynamikgröße ( 3 ) is determined and continuously updated. Method according to Claim 1, characterized in that the actuator ( 7 ) is about a wheel brake. A method according to claim 1, characterized in that in the determined time course of the Umsetzfahrdynamikgröße ( 3 ) estimated tire parameters and / or estimated vehicle parameters ( 6 ) and / or the dynamic vehicle state. A method according to claim 1, characterized in that from the time course of the Umsetzfahrdynamikgröße ( 3 ) a pre-tax amount ( 4 ) is determined, which enters into the control of the actuator. A method according to claim 6, characterized in that from the time course of the Umsetzfahrdynamikgröße ( 3 ) additionally at least one of the pilot control variable different target size ( 4 ) is determined, which also enters into the control of the actuator. Method according to Claim 6, characterized that the input tax quantity is a Target braking torque is. Method according to claim 7, characterized in that that the target size is a Setpoint speed is. A method according to claim 7, characterized in that from the difference between the desired size and the corresponding currently present actual value of the same physical quantity ( 40 ) in particular by means of a PID controller ( 5 ) a correction value for the pilot control variable is determined. Method according to claim 10, characterized in that the actuator ( 7 ) is controlled such that with respect to the braking process, the sum of the pre-control value and the correction value ( 50 ) is realized in the actuator or by the actuator. A method according to claim 6, characterized in that the pilot control variable from the time course of the Umsetzfahrdynamikgröße by means of an inverse system ( 4 ) is determined. Method according to Claim 6, characterized that in determining the input tax quantity, the determined current Vehicle longitudinal speed (v) received. A method according to claim 13, characterized in that in the determination of the pilot control quantity additionally estimated tire parameters or estimated vehicle parameters ( 6 ). A method according to claim 1, characterized in that the driver's desired driving dynamics variable from the pedal travel and / or prevailing at the output of the master cylinder form is determined ( 2 ). A method according to claim 1, characterized in that it is in the time course of the Umsetzfahrdynamikgröße ( 3 ) is a continuous and at least once continuously differentiable function. Method according to claim 1, characterized in that that the vehicle dynamics quantity is the vehicle longitudinal acceleration is. Method according to claim 17, characterized in that that the actuator is a wheel drive. Apparatus for carrying out the method according to claim 1.