DE102016201205A1 - Driver assistance system for a motor vehicle for regulating the longitudinal dynamics - Google Patents

Abstract

The invention relates to a driver assistance system for a motor vehicle having a controller for regulating the longitudinal dynamics (vehicle speed and / or longitudinal acceleration) whose manipulated variable is the target acceleration and which has a disturbance observer in such a way that the sum wheel torque or a magnitude proportional to the measured sum wheel torque is the input variable of the disturbance observer detectable and comparable with the measured actual longitudinal acceleration (so-called "cooperative" Störgrößenbeobachter).

Description

The invention relates to a driver assistance system for a motor vehicle for regulating the longitudinal dynamics, in particular the vehicle speed.

Methods and apparatus for controlling the speed of a vehicle have been known for a long time. A typical example is a so-called ACC system (Adaptive Cruise Control). In such a driver assistance system, the speed of the vehicle is automatically regulated to a desired speed which can be predetermined by the driver. Furthermore, such a system includes a distance sensor system, with the preceding vehicles can be determined. If the distance to a preceding vehicle threatens to become too low, the speed of the own vehicle is reduced in such a way that a safe or predefined distance to the vehicle ahead is maintained.

In such longitudinal guidance systems, a target acceleration of the vehicle is basically predetermined on the basis of the difference between the setpoint and actual speeds, which is regulated by controlling the drive (engine and / or transmission) and / or by actuating the wheel brake of the vehicle. In the context of such a desired acceleration regulator, a disturbance observer is furthermore known, by means of which the control quality of the acceleration regulator is improved.

A Störgrößenbeobachter is for example in a in the DE 10 2005 036 924 A1 described driver assistance system included. This driver assistance system is based on a method for adaptive distance and / or vehicle speed control in a motor vehicle, in which the vehicle acceleration for comfort and safety reasons are not changed in leaps, but at the defined as temporal change of acceleration jerk in positive and negative Direction is limited by limits. The driver assistance system according to DE 10 2005 036 924 A1 has a controller for regulating the acceleration of the motor vehicle according to a desired acceleration, which has a coupling-in element for coupling in an additional acceleration predeterminable by the driver of the motor vehicle. By using a coupling element for coupling in a presettable by the driver of the motor auxiliary acceleration, the driver is enabled by a higher-level control to feed additional acceleration requirements in the speed control system, without having to switch off before. In this case, however, a separate coupling member is provided in addition to the accelerator pedal and the brake pedal.

It is the object of the invention to further improve a disturbance observer in the context of a longitudinal guidance control.

This object is solved by the features of patent claim 1. Advantageous developments of the invention are the subject matters of the dependent claims.

The invention relates to a driver assistance system for a motor vehicle with a controller for regulating the longitudinal dynamics (vehicle speed and / or longitudinal acceleration) whose manipulated variable is the target acceleration and which has a disturbance observer in such a way that the summation wheel, formed from the driver and / or by a vehicle dynamics control system (eg ABS, ASC, DSC, DXC) and / or drive torque and / or braking torque given by a driver assistance system, or a variable at least proportional to the sum wheel torque (such as, for example, the corresponding converted vehicle speed) can be detected as the input variable of the disturbance observer and with the measured actual longitudinal acceleration is comparable (so-called "cooperative" Störgrößenbeobachter).

Preferably, this cooperative disturbance observer is switchable depending on at least one predetermined condition in a so-called "non-cooperative" Störgrößenbeobachter, which is characterized in that instead of Summenradmoments the target acceleration as the input variable of disturbance observer detectable and is comparable to the measured actual longitudinal acceleration. In this case, a possible predetermined condition for the switching, if neither a driver intervention nor a vehicle dynamics control intervention takes place and thus results in the summation wheel only by the stated specification of the driver assistance system.

The invention is based on the following findings:
The cruise control or the ACC system usually allow the driver sets or changes the desired speed by means of a control element, for example by means of a steering column lever or buttons on the steering wheel and that the system then the predetermined speed, depending on a given time interval to the vehicle ahead by means of an accelerator controls.

These driver inputs in the form of driver braking torques or driving torque lead to a modified target specification in the control loop of the acceleration controller, as well as disturbances, for example, due to Changes in the driving resistance, occur. According to the invention, a disturbance observer is designed in such a way that, in order to improve the control quality (robust control against interference influences), the influences of the disturbance variables can be distinguished from the influences by the driver specifications.

In the following, the disturbance observer will be discussed in more detail in connection with the requirement for a robust control (in particular longitudinal trajectory control):
In order to apply the control structure in a wide operating range, a robust regulatory design is sought. The goal is to use as little model knowledge as possible. A robust design scheme copes with the model uncertainties. The disturbance observer plays an important role. It can be assumed in the invention, for example, from the known disturbance observers according to Ohnishi (1987), which is modified according to the invention.

The draft regulation is usually based on a model of the dynamic behavior of the route. This model reflects the true behavior more or less well. Especially with linear models, which have been linearized by one operating point, the behavior can deviate strongly, as long as the operating point is left. Furthermore, due to modeling uncertainties or parameter variations, significant deviations from the underlying nominal model may occur. The latter can occur due to varying operating conditions, such as the fluctuating mass of a vehicle due to different loading.

The task of the robust control is therefore to find a controller that meets certain minimum requirements for the control loop, no matter what value the varying parameters assume.

Mathematical models can not accurately map physical systems and are always an approximation. Often, very accurate modeling is not desirable because it increases the model order and makes a simple model better suited for design and analysis of the control. In control engineering, it is customary to insert uncertainties into models in order to be able to make statements about model deviations.

By contrast, dynamic uncertainties arise from unaccounted for or unrepresented dynamics and are frequency-dependent. Examples of these are not shown actuators. Mathematically, unstructured uncertainties can be described by multiplicative input or output uncertainties.

The basic question of the robust regulation is for which area the closed loop is stable.

Robust longitudinal trajectory control:

The main task of the longitudinal trajectory following regulation is the suppression of disturbances by driving resistances. Furthermore, the shortcomings of the feedforward control must be compensated. The manipulated variable is a nominal acceleration. This is divided by the actuator coordination on the two actuators drive and brake. The auxiliary quantity used is the sum wheel torque. The implementation of the disturbance observer of the slave controller is explained below:
According to the invention, it has been recognized that a non-cooperative and a cooperative embodiment of the Störgrößenbeobachter can be implemented. The latter offers the advantage that driver inputs via the accelerator pedal and / or the brake pedal are not suppressed as disturbances. In both implementations, the measured vehicle longitudinal acceleration is used as the input, since all significant disturbances can be detected by means of this signal.

Classic, non-cooperative implementation of the disturbance observer:

In the classical, non-cooperative implementation, the system input, in this case the target acceleration, is compared with the measured actual acceleration. Since the Längsaktuatorik has significant dead times, preferably the assumed (eg empirically determined) value of the dead time is taken into account in the forward branch of the Störgrößenbeobters.

This conversion imposes on the control loop the nominal behavior of the dynamics of the actuators and the wheel dynamics (running-in dynamics) and suppresses disturbances on the acceleration plane stationary exactly. In addition to the disturbances caused in particular by driving resistances, however, this conversion also compensates for driver inputs via the accelerator pedal and / or the brake pedal. For this reason, the cooperative implementation preferred according to the invention is explained below.

In the cooperative execution of the Störgrößenbeobachter is used as an intermediate size Summenradmoment from drive and / or braking torque as the input of disturbance observer. This is also compared with the measured longitudinal acceleration. This offers the following advantages compared to the non-cooperative implementation:
Actuator limits are thus taken into account directly in the disturbance observer (for example, the limited acceleration potential of the drive). Furthermore, driver inputs by accelerator or brake pedal or the intervention of subordinate vehicle dynamics controllers (such as ABS, DSC, ASR), which limit the drive torque in order to achieve maximum traction of the vehicle, are not perceived as failures. Rather, an attempt is made to suppress the actual interference present. Deviations caused by saturation or driver or vehicle dynamics control system interventions are detected in the cooperative disturbance observer. There will then be no attempt to "fight" them .. The disturbance observer does not work against these effects. In contrast to the usual implementation, no dead time has to be taken into account in the disturbance observer since this is already contained in the signal of the summation wheel torque. In this case, the assumed vehicle mass and the assumed dynamic rolling radius, the time constant and attenuation of the actuator and the time constant of the tire dynamics are taken into account. The time constant depends on the respective vehicle speed and the slip. The time constant of the actuator should be known as accurately as possible, since the cooperative implementation here no imprinting of the desired behavior is possible.

In summary, due to the configuration of the disturbance variable observer according to the invention, disturbances on the acceleration plane, which are caused in particular by driving resistances, are suppressed. In this case, however, the acceleration-relevant driver and / or vehicle dynamics control system interventions are preferably not suppressed by the cooperative embodiment of the disturbance variable observer. Furthermore, limitations and the robustness of the controller are considered.

In the drawings, embodiments of the present invention are shown. Show it

1a an overall controller structure for a longitudinal trajectory sequence control with the simplest inventive cooperative embodiment of a disturbance variable observer according to the invention, wherein

1b describes in more detail the essential variables considered in the controller structure,

2 an example of a modified cooperative disturbance observer for the sequential control and

3 an example of a non-cooperative disturbance observer for the sequential control.

• – Dynamische Vorsteuerung
• – Trajektorienfolgeregelung:
• • Folgeregler
• • Störgrößenbeobachter

1a shows a so-called two-degree-of-freedom structure as overall controller structure for a longitudinal trajectory sequence control, consisting of:

• - Dynamic feedforward control
• - Trajectory Succession Control:
• • slave controller
• • disturbance observer

Where a * is the planned target acceleration, v * the planned target speed and x * the planned target position of the trajectory planning. The disturbance observer 1 is basically designed cooperatively. In the so-called cooperative execution of Störgrößenbeobachter 1 As intermediate value, the measured _sum wheel torque M _sum is input to the disturbance observer 1 used. This _sum wheel torque M _sum (or a variable proportional to this sum wheel torque) is likewise compared with the measured longitudinal acceleration a.

In 1b are supplemented the essential sizes of in 1a described regulator structure described mathematically, where G _{a represent} a mathematical model of the drive and braking dynamics and G _r a mathematical model of wheel dynamics.

• – Vergleich des Summenradmoments M_sum (in Beschleunigung umgerechnet) mit der gemessenen Ist-Beschleunigung a.
• – Berücksichtigung von Totzeiten 2 im Vorwärtszweig.
• – Aufprägen eines Wunschverhaltens 3.

In 2 a modified cooperative embodiment of a Störgrößenbeobachter invention is shown in detail with the following criteria:

• - Comparison of the _sum wheel torque M _sum (converted into acceleration) with the measured actual acceleration a.
• - consideration of dead times 2 in the forward branch.
• - imprinting a desire behavior 3 ,

• – Vergleich von Sollbeschleunigung a_soll und gemessener Ist-Beschleunigung a.
• – Berücksichtigung von Totzeiten 2 im Vorwärtszweig.
• – Aufprägen eines Wunschverhaltens 3.

In 3 a non-cooperative embodiment of a Störgrößenbeobachter invention is shown in detail with the following criteria:

• - Comparison of target acceleration a _soll and measured actual acceleration a.
• - consideration of dead times 2 in the forward branch.
• - imprinting a desire behavior 3 ,

The non-cooperative design of the Störgrößenbeobachter is particularly advantageous if the Summenradmoments M _sum results only the requirement of the respective active driver assistance system and thus no driver default or vehicle dynamics control system interventions take place.

Therefore, in an advantageous embodiment of the invention, in particular in the form of corresponding program modules in the electronic driver assistance control unit, a first cooperative Störgrößenbeobachter 1a ( 2 ) and a second non-cooperative disturbance observer 1b ( 3 ), between these two Störgrößenbeobachtern 1a and 1b can be switched depending on defined conditions.

For example, the first disturbance observer 1a basically be activated and the disturbance observer 1b be automatically activated only when no driving dynamics control system or driver interventions take place.

Switching takes place depending on the currently desired advantages.

Advantage of cooperative design:

• - Driver specifications are not perceived as a fault, suitable for cooperative functions.
• - Limits and dead times are directly seen by the disturbance observer and thus not compensated.
• - Design and proof of stability of the controller considerably facilitated.

Disadvantage of cooperative design:

• - Imprinting the desired behavior only possible for the rear part of the route (wheel dynamics).

Advantage of non-cooperative design:

• - Imprint a dynamic desire behavior on the subordinate track (drive actuator and wheel dynamics).
• - Robustness, suitable for high control requirements.

Disadvantage of non-cooperative design:

• - Driver presets are compensated in the same way as faults.
• - Limitations and driving dynamics interventions are not seen in the observer - anti-windup necessary.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102005036924 A1 [0004]

Claims (3)

Driver assistance system for a motor vehicle having a controller for controlling the longitudinal dynamics, the manipulated variable of the desired acceleration (a _soll) and (a disturbance observer 1 ; 1a ) in such a way that a sum wheel torque (M _sum ) or at least one variable proportional to the _sum wheel torque can be detected by it as an input variable and is comparable to the measured actual longitudinal acceleration (a) ("cooperative" disturbance observer). Driver assistance system according to claim 1, characterized in that the cooperative disturbance observer ( 1 ; 1a ) dependent on at least one predetermined condition in a non-cooperative disturbance observer ( 1b ) is reversible and vice versa. Driver assistance system according to one of the preceding claims, characterized in that a predetermined condition for the switching of the cooperative Störgrößenbeobachter ( 1 ; 1a ) into a non-cooperative disturbance observer ( 1b ) is the absence of a vehicle dynamics control system or driver intervention.

Images