DE10220575A1 - Detecting banked bend in vehicle moving in bend, involves detecting acceleration of vehicle structure perpendicular to road direction and especially towards road in connection with detected bend travel - Google Patents

Abstract

The method especially involves a vehicle dynamics control system monitoring the vehicle's behavior when traveling round a bend by evaluating various sensor signals. The system can influence vehicle behavior by system intervention. A conclusion can be drawn regarding traveling round a banked bend from acceleration of the vehicle structure perpendicular to the road direction and especially towards the road in connection with detected bend travel.

Description

The invention relates to a method for recognizing a steep wall curve or an inflated curve on one moved into such a curve in particular two-lane vehicle, in particular by a driving dynamics Control system that takes the vehicle's cornering behavior under Evaluation of various sensor signals monitored and, if necessary, by System interventions influenced. The technical environment becomes an example referred to DE 197 49 058 A1.

A driving dynamics control system can be a much safer one Driving behavior, for example, of a passenger car can be achieved than without such system. The known one is an example of such a system electronic stabilization program ESP or similar systems (e.g. DSC) called by other manufacturers, whereby these systems on several Access measured variables, so usually on the (initiated by the driver) Steering wheel rotation angle, on the vehicle longitudinal or driving speed, on the lateral acceleration and the yaw rate of the vehicle. There is normally a clear one between these variables Context. From the steering wheel angle and the vehicle speed you can namely by means of a simple vehicle model a target rotation rate and calculate a target lateral acceleration that with that of suitable Sensors in the vehicle determined the actual yaw rate and Lateral acceleration signals can be compared.

If, when the vehicle is cornering, the results of the Model calculation and the respective sensor signals do not match, so you can usually from an undesirable driving condition, for example. a breakout of the vehicle. By means of a suitable Intervention by the vehicle dynamics control system, for example in the brake system or the vehicle can then enter the steering system of the vehicle be stabilized.

However, the simple vehicle model only then delivers sufficiently precise Setpoints if the road in the currently driven curve is not around the Longitudinal axis of the road is inclined, d. H. if it is not is a so-called excessive curve. In fact, however Road curves are often designed at least slightly too high and can be in In extreme cases, quasi-so-called steep wall curves are formed, around which of Vehicles attain the maximum achievable driving speed in these curves increase. It should be expressly pointed out that in the present Text for better understanding mostly of steep wall curves, at which are known to look at the road in the radial direction The outside of the curve rises geodetically, but is spoken also only slightly excessive curves (as well - which in practice is relative is rare - even curves, the roadway to the outside of the curve falls geodetically) should fall under the term "steep wall curve".

If the vehicle is in a (typical) steep wall curve, then (e.g. in a vectorial representation) clearly visible that because of the then inclined vehicle position at least part of the from the vehicle Lateral acceleration resulting force due to gravitational acceleration is compensated. Without an undesirable driving condition then it comes that the calculated yaw rates and Lateral accelerations with the measured yaw rates and Lateral accelerations no longer match. To those from the Driving on steep wall curves resulting errors or their Effects in the form of interventions by a vehicle dynamics control system exclude, current driving dynamics control systems work with a relatively wide So-called dead zone, in which certain discrepancies are ignored.

In a steep wall curve, the quasi-remaining one changes vertically portion acting on gravitational acceleration (or gravitational force) Component vector from the lateral acceleration or lateral acceleration force from the vehicle body towards (also inclined) Road force or acceleration. The vehicle thus experiences when driving through a steep wall curve another from the Lateral acceleration (or lateral acceleration force) and gravitational acceleration (or Gravitational force) resulting acceleration or force in the direction of Roadway than when driving through a non-inflated curve below same lateral acceleration (or same lateral acceleration force) the Case is.

An attempt has therefore already been made to use an essentially common one Driving dynamics control system or with the used by this Sensors or sensors to be able to recognize the fact that a Vehicle moves in a steep curve. The one mentioned at the beginning DE 197 49 058 A1 shows an example of this. The available sensor signals are also determined and suitable from this using the sensor signals Plausibility checks carried out. In particular, the yaw rate serves as one such a benchmark. These plausibility queries must be over a certain period of time, which is not only complex, but in particular has the consequence that the so-called steep wall detection only with a time delay.

To be able to immediately recognize that a vehicle is on a steep curve drives in and thus to avoid the just-mentioned delay, is basically the installation of an additional sensor in the vehicle conceivable, which measures the rate of rotation around the longitudinal axis of the vehicle. however prevents (as is known) the inevitable without defined support points Integration of signal noise in vehicle-compatible sensors exact evaluation. To remedy this, it should be recognizable when the Road inclination in the transverse direction has the value "zero", which with simple means however is not possible. Otherwise, they are vehicle-compatible Rotation rate sensors are relatively expensive, while the usual, of driving dynamics control systems required and already existing sensors this desired signal cannot deliver.

Also, if applicable, data that can be transmitted to or from the vehicle Navigation system that is known to have a lot of information can contain about the course of the road, provide no information about the roadway bank or a steep wall curve and their Design. On the other hand, steep wall detection is desirable, there - as already explained - previous driving dynamics control systems due to the lack of a relatively insensitive default need to avoid unnecessary error messages.

A remedial measure for this problem is to be shown consequently object of the present invention.

The solution to this problem is characterized in that from a Acceleration of the vehicle body in a perpendicular to the road Direction (and especially towards the lane) in connection with a detected cornering on a steep wall curve or an excessive curve is closed. Advantageous training and Further training is the content of the subclaims.

According to the invention, the effect already described above is that when Driving on a steep wall curve due to the inclination of the road under influence the lateral acceleration of the vehicle body reinforces towards Accelerated roadway is used to this driving state (in a so-called steep wall curve or the entry into one). It should also be queried whether the vehicle is currently in a Curve is moved or whether a cornering is currently taking place, for example a steering wheel angle specified by the driver of the motor vehicle can be checked for plausibility. Without such a steering wheel angle change practically no entry into a bend, at least on public roads possible with large cant. Through this further query you can Changes in the buoyancy of the vehicle structure, for example at gusty headwinds can be eliminated. Others too Sources of error can be found in that, in addition to a finding that a Acceleration in the vertical direction or in a direction perpendicular to the road Direction occurs, a determination is still made about cornering, at least essentially be excluded.

It is advantageous with the method according to the invention possible from a (significant) vehicle body acceleration in Vertical direction or in a direction perpendicular to the road already at Entering this into a so-called steep wall curve to infer this state of affairs, so that this method reacts spontaneously or responds very quickly. Again on the theory or on the principle of the invention Coming back from the procedure, add up in road lane curves with large Cross slope (up to the steep face) the acceleration due to gravity and the Lateral acceleration vectorially to a resulting acceleration in Direction to the lane (or in rare cases also opposite, always however in a direction perpendicular to the road surface), which is greater than the acceleration due to gravity. In extreme cases, in the vehicle itself no lateral acceleration can be measured anymore, but one significant increase in vertical acceleration.

This change in gravitational acceleration, especially when entering a Steep wall curve can now, for example, with a vertically measuring Accelerometer are detected, d. H. that to register or measure a such acceleration of the vehicle body in the direction of the road (or also opposite) basically a suitable sensor, namely a to determine the vertical acceleration, in the vehicle or on Vehicle structure can be provided. A change in the sensed Vertical acceleration in curves is then a measure of the curve elevation (if a curve or cornering is recognized in a suitable manner).

Taking into account the fact that a sensor with vertical Direction of measurement due to the dependence on the cosine of the angle of inclination recognize the roadway in the transverse direction only relatively large inclination angles may, it may be advisable to use such an (additional) Acceleration sensor in the sense of finely evaluable signals at an angle of e.g. 45 ° offset from the (already existing) lateral acceleration sensor to block. An evaluation of the signals from both acceleration sensors then enables an evaluation with increased accuracy or determining the bank of the roadway or the vehicle.

A certain disadvantage of the embodiment of the so far described However, the inventive method is that at least one further acceleration sensor is needed, to the one above also relatively high accuracy or sensitivity requirements be put. Usually in motor vehicles with driving dynamics Control systems namely only sensors for lateral acceleration and possibly in future also for longitudinal acceleration with regard to a Incline detection available. On the other hand, electronically controllable ones are known Shock absorbers with variable damper characteristics, to their Control also requires at least one vertical accelerometer becomes. If such a damper system is installed in the vehicle, then - at least regarding the hardware - to implement the The method according to the invention practically requires no additional effort.

No independent vertical acceleration sensor to measure one Acceleration in the vertical direction is advantageously required if - as further proposed - an acceleration of the vehicle - Structure in the direction of the road from the signals at least one Level sensor, with the help of which the distance between the Vehicle body and a vehicle wheel or an associated Chassis part can be measured, is determined. such Level sensors are already standard on many motor vehicles installed and can be provided for a variety of purposes or it their signals can be evaluated for different purposes. For example, a level control system can respond to the signals from Access level sensors, as well as an adjustment device for the so-called. Xenon headlights, possibly an air suspension system or more. So are Level sensors for all vehicles with xenon light required by law prescribed to reliably increase the pitch angle of the vehicle body capture and a glare from the headlight range control To prevent oncoming traffic.

It is possible that such level information only for one Vehicle side of a two-lane vehicle are present. In contrast, at Vehicles equipped with air suspension systems, depending on the type the system a suspension travel signal for each wheel and thus a Altitude signal, if necessary an air spring internal pressure signal may also be present, see above that level sensors are then available for both sides of the vehicle can. Regardless of this, the particular advantage is basically one Processing the signals from level sensors to see that no independent acceleration sensor is required. Because it can just as well from the time-differentiated signals of at least one so-called Level sensor on the one to be monitored according to the invention Acceleration of the vehicle body towards (or away from) the carriageway getting closed.

The way is already suggested by evaluating the existing level signals without additional sensors, d. H. without one additional vertical acceleration sensor, albeit one may well be present, possibly only to carry out a Signal matching. One leads while driving in a steep curve occurring change in force towards the roadway or in general always in a direction perpendicular to the road surface changed suspension travel in the vehicle's suspension system, namely depending on the vehicle driving speed, on the excess of the Curve and the radius of the curve.

Biaxial or multi-axle motor vehicles can be Level control system must be equipped, which mostly the height of the Vehicle body opposite the wheel guide members on the vehicle rear axle changed. In this case, an evaluation of the rear axle spring travel can or the level signals on the vehicle rear axle in particular at a quickly responding level control system to wrong results lead, which is why it is further suggested that this or that Level signal (s) in the range of or on an axis without one Level control device, in particular on the front axle or wheel Wheels will be evaluated. The spring travel is advantageous (or level signals) on the front axle of the vehicle anyway less sensitive to changes in the load of the vehicle. at Vehicles that are not equipped with a level control system, is, however, an evaluation of the one or more of the vehicle rear axle provided level sensor or sensors possible.

An entry into a (strongly) inflated curve is basically parallel Recognize front wheel deflection, but there is also a delay of the vehicle in the longitudinal direction, for example Brake pressure or by a drag torque of the vehicle drive unit such behavior. To when using the invention Procedure possibly resulting from such pitching movements Excluding errors safely, it is further suggested that a by a pitching movement of the vehicle body Change in level by taking into account the level signals on all vehicles. Axes and / or by taking into account driving forces or Braking forces are not included in the steep wall detection. In other Expressed in words, a comparison of the level signals (or their differential quotients) a possible wrong conclusion for both axes Eliminate from a change in pitch angle. Such a However, a mistake can also be made by taking the driving Speed of the vehicle in connection with a consideration a braking process (and thus, for example, a brake pressure signal) and the acting moment of the vehicle drive unit avoided become. By monitoring such factors or influencing factors that as is known, particularly at higher driving speeds Nodding of the vehicle body, i.e. H. a tilting movement around the vehicle transverse axis can cause a detected change in altitude such pitching movement, so that then not on the Entry into a steep wall curve can be closed or closed becomes.

In addition, it is also possible to eliminate interference by means of a suitable one Filtering the vehicle altitude signals, especially with a relative long time constants (in the order of magnitude higher than 1 second) largely eliminated. Especially if only an altitude signal for there is a vehicle side of a two-lane vehicle (for safety's sake) the time constant of the filtering should be increased that possible effects from an asymmetrical bump be excluded.

While the vehicle is cornering, wheel stroke changes can occur occur without the total wheel contact force changing. This known effect is referred to as support, the vehicle structure towards the wheels without lifting the wheel load changes. In order to avoid misinterpretations resulting from this, also a so-called support factor in the detection of a Steep wall curve or in the determination of the corresponding Increase curve with, this support factor in turn from the Curve radius or the steering angle applied by the driver (or Steering wheel angle) and the current vehicle driving speed can be.

It has already been explained above how interference can occur Nodding movements of the vehicle body when using the invention Procedure can be eliminated, expressly pointing to it it should be noted that this is not only when the signals of one or more Level sensors are evaluated, so can be done, but also then when the (to be determined when driving on steep wall curves) Acceleration of the vehicle body essentially in the vertical direction or towards the road using a vertical accelerometer or Like. Is determined.

The same applies to a rolling movement of the vehicle body, i. H. on Swiveling around the longitudinal axis of the vehicle. This can be done either Consideration of the level signals on the two wheels of a vehicle. Axis and / or by estimating the roll angle from the measured lateral vehicle acceleration, and should then (analogous to a pitching movement due to a positive or negative vehicle Longitudinal acceleration) no entrance into the steep wall according to the invention Find detection. In other words, it is a roll angle either already known, namely when left and right preferably one level sensor each on the vehicle front axle is provided, or it can be the roll angle over the - in driving dynamics - Control system already existing - measured value of vehicle lateral acceleration can be estimated. Between the roll angle and the vehicle Lateral acceleration is essentially a direct one Connection via the spring characteristic, either in an electronic Control unit (for example, the driving dynamics control system) as known can be or via a so-called loading detection, if provided can be learned at least in rough levels.

There may also be differences in the possible vehicle mass are taken into account by the vehicle structure behavior or the Altitude signals in the event of a positive or negative acceleration in Vehicle longitudinal direction is / are observed. Defacto are deviations from the absolute height levels (between the vehicle body and the wheels or the roadway), caused by high wheel loads or different heavy loading of the vehicle, unavoidable, resulting in adulteration the measurement results in terms of the degree of cant can drive through steep wall curve. On the other hand, it is possible to get a current vehicle load sufficiently accurate from the driving behavior of the To determine the vehicle, for example by observing the altitude values in start-up operations, for which purpose the non-prepublished German Patent applications 101 48 091 and 101 48 096 can be referenced. If, for example, using the algorithm described therein, the current Loading of the vehicle or the current vehicle mass is sufficiently precise is known, this can also within the scope of the present inventive method are taken into account from the degree of Altitude change - then with knowledge of the vehicle mass - the degree of To be able to determine the elevation of the steep wall curve just traveled.

Basically, it can not only be determined that a Steep wall curve or excessive curve is traveled, but it can also be Cant, d. H. the slope of the road in the transverse direction of the road be determined with sufficient accuracy. A corresponding one can do this Evaluation algorithm can be designed appropriately, independently whether the so-called steep wall detection by means of at least one suitable Acceleration sensor or evaluating the signals of one or several height sand sensors.

As for the requirements for the signal quality of the level sensors concerns, these are to achieve a sufficiently precise statement about a curve elevation not higher than the previous one Field of application, namely for the headlight range control (in particular from Xenon headlights), because only relatively quick changes and not absolute altitudes should be recognized. Therefore, the tolerances for temperature errors and linearity errors of the level signals relative lie high. For the rest - as already mentioned above - a Comparison with a possibly already installed sensor to determine the Vertical acceleration (e.g. in connection with electronically controllable Damper systems) take place, for example, by an influence of long-wave Correct bumps on the vehicle weight.

Overall, there is information from the evaluation of the level signals derivable via an entrance into a steep wall curve and its elevation noticeable, with regard to realistic measurement results available sensor signals appropriately filtered, especially with suitable ones Frequency can be low-pass filtered. You get with that inventive method a sufficiently accurate information about a Lane crossing, preferably without additional sensors. With these additional information or with such additional A driving dynamics control system of a motor vehicle, for example. Passenger car, significantly refined compared to the current state be coordinated, as error messages for very excessive curves can be avoided. This information about driving on a Incidentally, steep wall curves can also be used for control interventions be used in the steering system of the vehicle, as well as in one Headlight range control or headlight-light cone positioning, although it should be noted that quite a lot of details may deviate from the above explanations, without the content leave the claims.

Claims (9)

1. A method for recognizing a steep wall curve or an excessive curve on a two-lane vehicle that is moved into such a curve, in particular by means of a driving dynamics control system, which monitors the cornering behavior of the vehicle by evaluating various sensor signals and, if appropriate, influenced by system interventions, characterized in that from an acceleration of the vehicle body in a direction perpendicular to the carriageway and in particular towards the carriageway in connection with a detected cornering, it is concluded that a steep wall curve or an excessive curve is being negotiated. 2. The method according to claim 1, characterized in that an acceleration of the vehicle Structure in the direction of the road from the signals at least one Level sensor, with the help of which the distance between the Vehicle body and a vehicle wheel or one with it connected chassis part can be measured, is determined. 3. The method according to claim 2 for a two-axle motor vehicle, especially a passenger car, characterized in that the level signal (s) in the Area of one or of an axis without one Level control device, in particular on the front axle or wheel Wheels will be evaluated. 4. The method according to any one of the preceding claims, characterized in that an acceleration of the vehicle Structure in the direction of the road from the signals of a suitable Sensor for determining the vertical acceleration is determined. 5. The method according to any one of the preceding claims, characterized in that a by a pitching movement of the Vehicle level change caused by Consideration of the level signals on all vehicle axles and / or by taking drive forces or braking forces into account Entry into the steep wall detection takes place. 6. The method according to any one of the preceding claims, characterized in that a rolling movement of the vehicle Construction by taking the level signals at the both wheels of a vehicle axle and / or by an estimate the roll angle from the measured lateral acceleration none Entry into the steep wall detection takes place. 7. The method according to any one of the preceding claims, characterized by differences in the possible Vehicle mass are taken into account by the vehicle body Behavior or the level signals in the event of a positive or negative acceleration in the longitudinal direction of the vehicle was observed will become. 8. The method according to any one of the preceding claims, characterized in that the level signals with a relatively long time constants (especially on the order of magnitude) greater than 1 sec.) are filtered. 9. The method according to any one of the preceding claims, characterized in that a so-called Taking into account the support when cornering with, in particular from the current steering angle and the vehicle driving speed is calculated.