Method for detecting the risk of a motor vehicle tipping over

Abstract

Method for detecting a risk of a motor vehicle tipping over, wherein the risk of tipping over is the risk of the motor vehicle tipping over sideways, in which - the time derivative of the lateral acceleration (Day) is determined and - depending on the time derivative of the lateral acceleration (Day), the presence of the risk of tipping over is detected, characterized in that - the temporal derivative of the lateral acceleration (Day) in a form weighted at least with the lateral acceleration (ay) is included in the detection of the risk of tipping over (101) and that the time derivative of the lateral acceleration (Day) is included in the detection of the risk of rollover in a form weighted at least additionally with the time derivative of the steering angle (DLw).

Description

State of the art

[0001] From DE 101 35 020 A1, a method and a device for detecting and eliminating a risk of tipping over are known. To eliminate the risk of tipping over, a control system activates actuators. To detect the risk of tipping over, a quantity describing the lateral dynamics of the vehicle is determined. This quantity describing the lateral dynamics is compared with at least one threshold value. If the quantity describing the lateral dynamics is greater than or equal to the threshold value, stabilization interventions are carried out by means of the actuators. The features of the preambles of the independent claims can be found in DE 101 35 020 A1.

[0002] The publication DE 10 2006 044 425 A1 discloses a method for stabilizing motor vehicles against tipping, describing how the risk of tipping can be reduced by braking individual wheels.

[0003] The publication DE 10 2006 048 414 B3 discloses a method for detecting a rollover situation, wherein a rollover situation is detected when a decision parameter formed from lateral acceleration and simultaneously a decision parameter formed from roll rate corresponds to a stored critical combination.

[0004] The publication DE 103 56 827 A1 discloses a tilt stabilization system taking into account the steering angle.

[0005] The document DE 198 44 912 A1 discloses a method for influencing the propulsion of a vehicle, wherein the propulsion of the vehicle can be influenced by evaluating the lateral acceleration profile in order to increase lateral stability by reducing drive slip. Disclosure of the invention

[0006] The invention relates to a method for detecting a risk of a motor vehicle tipping over, wherein the risk of tipping over is the risk of the motor vehicle tipping over sideways, in which - the time derivative of the lateral acceleration is determined and - depending on the time derivative of the lateral acceleration, the presence of the risk of tipping over is detected.

[0007] The core of the invention is characterized by the fact that - the temporal derivative of the lateral acceleration, at least in a form weighted by the lateral acceleration, is incorporated into the detection of the risk of tipping over.

[0008] This weights the increase in lateral acceleration (Day) depending on the current driving condition, since a high lateral acceleration gradient is naturally much more critical for the vehicle in the higher lateral acceleration range than at low lateral acceleration values. This avoids unnecessary control interventions in the range of low lateral accelerations.

[0009] According to the invention, the temporal derivative of the lateral acceleration is incorporated into the detection of the risk of tipping over in a form weighted at least additionally with the temporal derivative of the steering angle.

[0010] By using the time derivative of the steering angle, which can also be referred to as the steering angle gradient or change in steering angle per unit time, only increases in lateral acceleration resulting from an increase in the steering angle are considered in the weighting. This is advantageous so that small fluctuations in lateral acceleration, which are caused, for example, by bumps in the road, do not lead to incorrect control inputs, especially at high lateral acceleration.

[0011] An advantageous embodiment of the invention is characterized by the fact that - that at least on the basis of the lateral acceleration and the time derivative of the lateral acceleration, a lateral dynamics parameter describing the vehicle's lateral dynamics at the present or a later time is determined, and - that the risk of overturning is detected as present when the lateral dynamic parameter exceeds a threshold value.

[0012] An advantageous embodiment of the invention is characterized in that the lateral acceleration, its time derivative, is additionally included in the lateral dynamics parameter. Lateral acceleration is a parameter that is readily available in a standard vehicle dynamics control system. The gradients of the steering angle and the lateral acceleration can also be determined without significant additional effort, so that the invention can be integrated into a standard vehicle dynamics control system without incurring high additional costs.

[0013] An advantageous embodiment of the invention is characterized in that the lateral dynamic quantity is determined using the calculation method. ayeff=ay+k1*ay*DLw*Day+k2*DLw+opt The calculation is performed where ayeff denotes the lateral dynamic quantity, ay the lateral acceleration, Day the time derivative of the lateral acceleration, and DLw the time derivative of the steering angle. k1 and k2 are constant factors, and opt are one or more optional additional terms that differ from the terms ay, k1*ay*DLw*Day, and k2*DLw already included in the calculation formula.

[0014] An advantageous embodiment of the invention is characterized in that, in the event of a detected risk of tipping over, a stabilization intervention is carried out by driver-independent control of the braking system, the steering system or a chassis control system.

[0015] An advantageous embodiment of the invention is characterized in that, in the event of a detected risk of tipping over, the outer front wheel or both outer wheels are braked independently of the driver. These braking measures allow the lateral force of the most heavily loaded outer wheels to be reduced, thus permitting the wheels to slide in the outer direction of the curve, which leads to a reduction in lateral acceleration and a reduction in the risk of tipping over.

[0016] The drawing consists of Fig. 1.

[0017] In Fig. Figure 1 shows the basic sequence of the method according to the invention.

[0018] A rollover prevention system can be used within a vehicle dynamics control system to prevent vehicles from tipping over. Among other things, the vehicle's lateral acceleration can be used to estimate its rollover stability. If a certain maximum lateral acceleration threshold is exceeded, the outer front wheel or both front wheels are braked to generate a moment around the vehicle's vertical axis and to reduce the lateral forces exerted by these wheels. These effects reduce the vehicle's yaw rate, thus decreasing lateral acceleration and making it less prone to rollover.Since the rollover behavior depends not only on the current lateral acceleration but also on the driving situation, it is advantageous not to use only the measured lateral acceleration ay to assess rollover criticality, but rather a quantity ayeff, which incorporates various additional parameters besides the lateral acceleration. For example, to avoid reacting too late in the event of a rapidly increasing lateral acceleration, the quantity ay + k1 * Day is considered instead of the lateral acceleration ay and checked for exceeding a threshold value. Here, k1 is a factor to be applied, and Day is the change in lateral acceleration per unit time, or the time derivative of the lateral acceleration, i.e., Day = d(ay)fdt.

[0019] A further surcharge DLw is calculated from the gradient or the time derivative of the steering angle Lw, since after a dynamic steering operation against the direction critical for tipping over, a future increase in lateral acceleration is also to be expected.

[0020] This means that the following calculation rule can be used for ayeff, for example: ayeff=ay+k1*Day+k2*DLw. k2 is another factor to be applied.

[0021] A further improvement, which is the subject of the present invention, consists in modifying the additional term that depends on the gradient of the lateral acceleration Day.

[0022] The additional term k1*Day can lead to non-critical situations being considered as tipping-critical, and the controller then regulating unjustifiably, which can be perceived by the driver as a loss of comfort.

[0023] To modify this additional term, the lateral acceleration ay and the gradient of the steering angle, DLw, are now also taken into account. Thus, ayeff now reads: ayeff=ay+k1*ay*DLw*Day+k2*DLw.

[0024] This is intended to give the additional term k1*Day a greater weight if the lateral acceleration ay is very large and its increase resulted from an increase in the steering angle, i.e., DLw is also very large.

[0025] By multiplicatively incorporating the lateral acceleration ay, the increase in lateral acceleration Day is weighted according to the current driving condition, since a high lateral acceleration gradient is naturally much more critical for the vehicle at higher lateral acceleration values ​​than at lower lateral acceleration values. However, by using the steering angle gradient DLw, only an increase in lateral acceleration resulting from an increase in the steering angle Lw is considered. This is advantageous so that small fluctuations in lateral acceleration, caused, for example, by bumps in the road, do not lead to incorrect control responses, especially at high lateral acceleration. Furthermore, this means that a rapid increase in steering angle at high lateral acceleration is only classified as particularly critical if it also results in an increase in lateral acceleration.This is only the case if the front wheels are not yet saturated and can still transmit more lateral forces. If this is not the case, and the increase in steering angle does not result in an increase in lateral acceleration, then the situation is not critical and the rollover prevention system should not intervene.

[0026] The refinement of the summand, now called k1*ay*DLw*Day, according to the invention allows for a better resolution of the compromise between stability and comfort, as critical situations can be identified more effectively. This enables earlier and more decisive intervention in truly critical situations, without unjustifiably intervening in less critical situations due to a high lateral acceleration gradient.

[0027] It is also conceivable to use further addends in the calculation rule, i.e. ayeff=ay+k1*ay*DLw*Day+k2*DLw+..... or ayeff=ay+k1*ay*DLw*Day+k2*DLw+opt, where the term opt denotes further additional components.

[0028] The sequence of one embodiment of the method for detecting a risk of a motor vehicle tipping over is described in Fig. Figure 1 illustrates this. After the process starts in block 100, the value ayeff is determined in block 101. Subsequently, block 102 checks whether ayeff exceeds a threshold value SW. If not, the process branches back to the input of block 101. If, however, ayeff > SW, suitable stabilization interventions are carried out in block 103. The process according to the invention ends in block 104.

Claims

[1] Method for detecting a risk of a motor vehicle tipping over, wherein the risk of tipping over is the risk of the motor vehicle tipping over sideways, in which - the time derivative of the lateral acceleration (Day) is determined and - depending on the time derivative of the lateral acceleration (Day), the presence of the risk of overturning is detected, characterized by , that - the temporal derivative of the lateral acceleration (Day) in a form weighted at least with the lateral acceleration (ay) is included in the detection of the risk of tipping over (101) and that the time derivative of the lateral acceleration (Day) is included in the detection of the risk of rollover in a form weighted at least additionally with the time derivative of the steering angle (DLw). [2] Method according to claim 1, characterized by , - that at least on the basis of the lateral acceleration (ay) and the time derivative of the lateral acceleration (Day), a lateral dynamics parameter (ayeff) describing the vehicle's lateral dynamics at the present or a later time is determined, and - that the risk of overturning is detected when the lateral dynamic quantity (ayeff) exceeds a threshold value (SW) (102). [3] Method according to claim 2, characterized by , that the lateral acceleration (ay) is additionally included in the lateral dynamic quantity (ayeff). [4] Method according to claim 3, characterized by , that the lateral dynamic quantity (ayeff) is calculated using the formula ayeff=ay+k1*ay*DLw*Day+k2*DLw+opt is determined where ayeff denotes the lateral dynamics quantity, ay the lateral acceleration, Day the time derivative of the lateral acceleration, DLw the time derivative of the steering angle, k1 and k2 constant factors, opt are one or more optional additional terms. [5] Method according to claim 1, characterized by , that in the event of a detected risk of tipping over, a stabilization intervention is carried out by driver-independent control of the braking system, the steering system or a chassis control system (103). [6] Method according to claim 5, characterized by , that in the event of a detected risk of tipping over, the outer front wheel or both outer wheels are braked independently of the driver (103).

Images