DE102007022595A1 - Driving dynamics controller with reduced sensors - Google Patents

Abstract

The invention relates to a method for carrying out a vehicle dynamics control in motor vehicles. According to the invention, the controller (9) calculates a variable describing the yaw behavior of the vehicle, such as a slip angle gradient, without regard to the steering angle. As a result, the overall system can be realized in a particularly simple and cost-effective manner.

Description

State of the art

The The invention relates to a method for carrying out a vehicle dynamics control in motor vehicles according to the preamble of claim 1, as well as a control unit with a vehicle dynamics controller according to the generic term of patent claim 11.

Known Vehicle dynamics controllers serve to protect the driver in critical driving situations such as For example, when or understeer the vehicle, assist and stabilize the vehicle. Known from the prior art systems such. Eg ESP or DSC, usually regulate the yaw rate and / or the slip angle of the vehicle. If the control deviation is too high, the control usually takes effect automatic, wheel-specific brake interventions in the driving mode one. Other systems use an active steering system or an engine control unit as an actuator, to influence the driving behavior. A fundamental objective of the scheme is it going to create a yaw moment about the vertical axis of the vehicle, which counteracts the current yaw moment of the vehicle and the Vehicle thus stabilized.

conventional Regulators usually include a yaw rate sensor, a lateral acceleration sensor, a steering angle sensor and wheel speed sensors from whose signals a setpoint is calculated becomes. If the controlled variable - mostly the yaw rate or the slip angle of the vehicle - too far deviates from the nominal value, the system intervenes in the driving operation. A disadvantage of the known regulator is that relatively many Sensors are needed to calculate the setpoint.

Around The number of sensors was reduced by the Applicant already proposed a driving dynamics controller, the without yaw rate sensor gets along. The vehicle yaw rate becomes in this case from the wheel speeds estimated. However, this system has the limitation that during a slip control, as they are z. B. occurs in the context of an ABS process, the yaw rate only very inaccurately estimated can be, since the wheels partially block and not roll freely.

Disclosure of the invention

It is thus the object of the present invention, a vehicle dynamics control system to create with reduced sensors, especially during a Brake slip control works well enough.

Is solved this task according to the invention by those specified in the patent claim 1 and in claim 11 Characteristics. Further embodiments of the invention are the subject of dependent claims.

One An essential aspect of the invention is a driving dynamics controller to create, which is a target for greed behavior of the vehicle, in particular the Schwimmwinkelgradienten or a Yaw rate, without consideration the steering angle (or a proportional angle). Consequently can save the steering angle sensor and the overall system accordingly be simplified.

According to one first embodiment According to the invention, the float angle gradient forms the controlled variable of the control. The current float angle gradient is preferred in this case from the current, measured yaw rate, the lateral acceleration and the vehicle speed calculated. The yaw rate and the lateral acceleration are measured by means of appropriate sensors. The vehicle speed is estimated from the measured wheel speeds.

The float angle gradient dβ / dt can z. B. be calculated according to the following relationship:

Here a _{y is} the lateral acceleration, v _{x is} the vehicle longitudinal speed and ψ. the gradient of the yaw rate.

For example, the controller may become active if the float angle gradient dβ / dt exceeds a predetermined value. In order to make the control more robust, in addition the actual slip angle of the vehicle can be estimated. For this purpose, the slip angle gradient dβ / dt is preferably integrated, where: β k + 1 = (β k + β. · h) · k, (2)

there the parameter k is a factor <1 (Forgetting factor), the parameter h the sampling rate of the system and the index k is the time step value.

In In this case, the vehicle dynamics control preferably engages in the driving mode when the slip angle gradient β. exceeds a predetermined threshold and also has the same sign as the estimated slip angle β.

According to a second embodiment of the invention, the current yaw rate forms the controlled variable of the vehicle controller. In this case, from various other measures, without consideration Steering angle, z. B. a threshold ψ. _max for the yaw rate ψ. calculated. When the maximum threshold ψ. _{max is} exceeded, there is a stabilization intervention by the controller.

wobei k ein Aufweitungsfaktor, μ_est der geschätzte Fahrbahnreibwert und v_x die aus den Raddrehzahlen berechnete Fahrzeuggeschwindigkeit ist. Zusätzlich zur gemessenen Gierrate ψ . kann im Rahmen der Regelung, insbesondere zur Bestimmung der Stärke und des Zeitpunkts eines Stabilisierungseingriffs, auch noch der Gradient der Gierrate berücksichtigt werden.The maximum threshold ψ. _max can be calculated, for example, as follows: First, the current road friction coefficient μ _{est is} estimated from the signals of a lateral acceleration sensor, yaw rate sensor, the wheel speed sensors and a brake pressure sensor, as well as from the drive torque provided by the engine control unit. This estimate is well known in the art. The threshold ψ. _max is then z. B. calculated from the following equation:

where k is an expansion factor, μ _{est is} the estimated road friction coefficient, and v _{x is} the vehicle speed calculated from the wheel speeds. In addition to the measured yaw rate ψ. In the context of the regulation, in particular for determining the strength and the time of a stabilization intervention, the gradient of the yaw rate can also be taken into account.

Of the Driving dynamics controller according to the invention is in a control unit preferably integrated as software.

Brief description of the drawings

The Invention will be exemplified below with reference to the accompanying drawings explained in more detail. It demonstrate:

1 a schematic block diagram of a vehicle dynamics control system;

2a a vehicle with stable cornering; and

2 B a heavily oversteering vehicle.

Embodiments of the invention

1 shows a schematic diagram of a vehicle dynamics control system, which is essentially a control unit 1 with an integrated controller 9 having. The overall system further comprises a sensor system with the aid of which the actual behavior of the vehicle can be determined. The block indicates 2 a yaw rate sensor, block 3 a lateral acceleration sensor, block 4 the wheel speed sensors and block 5 a brake pressure sensor.

In the case of a critical driving situation in which the vehicle oversteer, for example, the controller 9 using different actuators in one block 10 are combined, intervene in the driving operation. In the context of the invention are preferably the wheel brakes 6 actuated. Optionally, but also an intervention in an electric steering 7 and / or the engine control.

Below are two embodiments of the regulator 9 described in more detail, which can be realized alternatively. According to a first embodiment of the invention, the controller regulates 9 the slip angle gradient β. of the vehicle. The current float angle gradient β. is calculated by the above-mentioned equation (1) from the current yaw rate ψ., Transverse acceleration a _y and the vehicle speed v _x . In addition, the actual slip angle β is estimated according to the above equation (2).

If the slip angle gradient β. exceeds a predetermined threshold and has the same sign as that according to the equation (2) calculated slip angles β, a stabilization intervention takes place. It is preferably to individual Radbremsen a set slip specified by a slip control is set. Alternatively, a desired braking torque is applied to individual wheel brakes preset, which is set by a brake controller.

According to a second embodiment of the invention, the vehicle dynamics controller controls 9 the yaw rate ψ. of the vehicle. In this case, an estimated road friction coefficient μ _est and the vehicle speed v _{x become} a maximum value ψ. _max calculated according to the above equation (3).

When the measured yaw rate ψ. the maximum value ψ. _max , a stabilization intervention is triggered. In order to minimize false triggering, the gradient of the yaw rate is taken into account at the same time.

2a shows a vehicle with stable cornering. It can be seen that the slip angle β is relatively small. The driving dynamics controller 9 does not trigger in this case.

In 2 B is shown a vehicle that is heavily oversteered. The slip angle β is correspondingly larger than in 2a , In this case, the vehicle dynamics control triggers 9 and causes a supportive yaw moment about the vertical axis of the vehicle, which counteracts the current yaw moment of the vehicle. The vehicle is thus quickly stabilized again.

Claims (11)

Method for carrying out a driving dyna in motor vehicles, characterized in that the controller calculates a desired value for the yaw behavior of the vehicle, such as a slip angle gradient (dβ / dt) or a yaw rate (ψ _max ), without consideration of the steering angle (δ). A method according to claim 1, characterized in that the current yaw rate (ψ), the lateral acceleration (a _y ) and the vehicle speed (v _x ) determined and from a Schwimmwinkelgradient (dβ / dt) is calculated, which forms the control variable of the control. A method according to claim 1 or 2, characterized in that the yaw rate (ψ) by means of a yaw rate sensor ( 2 ) and the lateral acceleration (a _y ) by means of a lateral acceleration sensor ( 3 ), and the vehicle speed (v _x ) is estimated from the wheel speeds (n). Method according to claim 2, characterized in that the float angle gradient (dβ / dt) is calculated according to the following relationship:

Method according to one of the preceding claims, characterized marked that in addition the actual Swing angle (β) is appreciated. A method according to claim 5, characterized in that the actual slip angle is estimated according to the following relationship: β k + 1 = (β k + β · h) · k. Method according to one of the preceding claims, characterized characterized in that a control intervention takes place when the Schwimmwinkelgradient (dβ / dt) is greater as a predetermined threshold and the estimated slip angle (β) are the same Sign has, as the swim angle gradient (dβ / dt). A method according to claim 1, characterized in that the actual coefficient of friction (μ _est) and the vehicle speed (v _x) are estimated and from this a threshold value (ψ _max.) For the yaw rate (ψ.) Is calculated of the vehicle. Method according to Claim 8, characterized in that the threshold value (ψ _max ) is calculated according to the following relationship:

Method according to claim 8 or 9, characterized that for determining the time and / or strength of the Regulating the yaw rate gradient (ψ) is taken into account. Controller, comprising means for performing one of the above claimed methods.