DE10225120A1 - Monitoring instability of vehicle with trailer, compares oscillation amplitude derived from transverse acceleration sensor or wheel speed sensor measurements with threshold - Google Patents

Abstract

The method involves measuring roll with a transverse acceleration sensor or wheel speed sensors, and evaluating to determine control parameters for a control system. Based on the measured values and the output of a counter, which represent the positive and negative amplitude and half period, the oscillation amplitude is compared with a threshold, and the result is evaluated to determine roll.

Description

The invention relates to a method for monitoring Motor vehicles with trailers on instabilities where those carried out by the vehicle and / or trailer Rolling movements with at least one lateral acceleration sensor or wheel speed sensors measured and for determining Control variables are evaluated for a control system.

The procedure aims to address the instabilities Detect vehicle combinations (motor vehicle with trailer) and correct before driving conditions occur by the driver can no longer be controlled. This unstable Conditions are the lurching and well-known in teams antiphase rocking of towing vehicle and trailer as well as itself looming rollover conditions with excessive lateral acceleration in the event of evasive action, lane changes or hasty Driver steering requirements.

Corresponding methods and devices are in various designs known (DE 199 53 413 A1, DE 199 13 342 A1, DE 197 42 707 A1, DE 198 10 642 A1, DE 199 64 048 A1).

The invention is therefore based on the object Safe condition of the vehicle with the trailer and to recognize early and the instabilities of the Adjust the vehicle team.

This object is achieved according to the invention in that, on the basis of measured variables (a_y _(tmax1) , tmax1, a_y _(tmin1) , tmin1, a_y _(tmax2) , tmax2, a_y _(tmin2) , tmin2, v_rr, v_rl, v_fr, v_fl), which were determined with the help of the lateral acceleration sensor or the wheel speed sensors and at least one counter and which represent the positive and negative amplitude and half the period (DT_h), including at least one band for half (DT_h) or the entire period (DT_f), the range of vibration (A1, A2, A3, ect.) Is compared with a threshold value (A_thr) and the comparison result is evaluated for the detection of roll movements.

It is advantageous that a roll movement occurs and a counter (Rec_Timer) is started if the following conditions are met:

The vibration range A (1, 2, 3 ect.)> A_thr

Half or the entire period (DT_h, DT_f) lies within the band. Under these conditions, namely that the conditions are met, the value of the counter (Rec_Timer) set to a start value 1. It is useful that the counter (Rec_Timer) depending on a elapsed time (T_rec) is reduced. A settlement to ensure instability over a period of time leading to a stabilization of the team is advantageous provided that the value of the counter (Rec_Timer) to the Start value is reset if within the time (T_rec) a roll motion is detected.

It is also advantageous that the limit (A_thr) after In accordance with the driving situation, preferably the Vehicle speed is estimated.

The reliability of the detection of roll movements is advantageously increased if the lateral acceleration component resulting from cornering is determined in a model and the value of the lateral acceleration (a_y _(tmax) , a_y _(min) , (a_y _(tmax2) , (a_y _(tmin2) ) ect.) is corrected with the lateral acceleration offset determined in the model.

The combination is advantageously stabilized by initiating brake interventions on at least one wheel, preferably the trailer, if the following conditions are met:

The vibration range A (1, 2, 3 ect.)> A_thr

Half or the entire period (DT_h, DT_f) lies within the band. It is also advantageous that the Brake intervention according to the maximum brake pressure or maximum braking force and actuator speed is determined. It is useful that the brake intervention in one Time window around the zero crossing of the curve-offset-adjusted lateral acceleration signal.

A method according to claim 10, characterized in that the time of intervention in a model according to the relationship

t_start = T_pinc - P_max_des / P_grad

is determined with P_grad = the mean pressure build-up gradient of the pressure build-up pump, P_max des = the brake pressure setpoint, t_pinc = the set point in time at which the P_max des is to be reached, where t_pinc = t_zero - t_stat ms, with t_stat = fixed amount of time, e.g. B. 100 ms and t_zero = next expected zero crossing of the curve-offset-adjusted lateral acceleration signal.

An embodiment of the invention is in the drawing shown and will be described in more detail below.

Show it

Fig. 1, the time course of the lateral acceleration of a lateral acceleration signal,

Fig. 2, the time course of the lateral acceleration of two transverse acceleration signals,

Fig. 3 shows the time course of the lateral acceleration, the rotation of the trailer and the brake intervention.

The process is divided into two problem areas:

First of all, a dangerous state must be reliably recognized. This can be used with various conventional or special Sensors happen either in the vehicle that the trailer pulls, be attached, or in the case of an existing one ESP systems already partially or completely in the vehicle are present, so that the recognition measures in today's ABS, TCS or ESP function of the towing vehicle integrated can be, or that in the trailer as additional sensors are introduced to using the critical conditions there to detect corresponding algorithms, which are stored in a dedicated provided electronics are implemented.

The second issue is in the case of a recognized instability this condition by appropriate Brake controls of the wheels of the vehicle and / or trailer or to be remedied by engine or steering intervention in the vehicle. If the interventions are carried out on the vehicle, this can happen again on the basis of a conventional or expanded one today ABS, TCS or ESP systems. In case of Brake interventions on the wheels of the trailer are suitable there Provide actuators that have an active braking force build-up allow.

From these different possibilities of Different systems result in situation detection and correction.

The first class of systems is right in the Driving dynamics controller of the driven vehicle integrated. Dependent of the available control system are the following Mechanisms possible:

ABS: detection based on wheel speed patterns, Intervention via active booster with the help of a short Braking synchronously on all wheels of the vehicle or wheel-specific by closing the inlet valves of the not active wheels to be braked by the control system.

TCS: detection as with ABS, intervention as with ABS in the case an existing active booster or with the help of hydraulic ABS / TCS pump on both front wheels in case a front-wheel drive vehicle or on both rear wheels or individually on each rear wheel in the case of rear-wheel drive vehicles.

ESP: detection of the critical driving condition by evaluating the wheel speeds, measured lateral accelerations, using the lateral accelerations converted by the yaw rate on the front and rear axles, and using the measured yaw rate itself and / or using the measured steering angle profiles;
Brake intervention as with TCS or with the help of the hydraulic ESP pump on all wheels of the vehicle or individually for each wheel (for example on the front and rear wheel of one side of the vehicle).
ESP: engine intervention, active steering

The sensors and are in the second system class the controller in the trailer, and the wheels of the Trailer braked together or individually. In the latter Case can only be one due to the reduction in effort only control device on one of the two wheels be provided so that the active brake interventions only ever done unilaterally. The one to be provided for the system Expansion of ABS, TCS or ESP ensures system interventions that do not perform the basic functions of ABS, TCS and ESP would, because in the case of a lighter vehicle roll even today's ESP doesn't mean an unstable state of oversteering or understeering. To the to suppress unstable condition but already in the beginning and to ensure safe driving behavior is a early intervention is absolutely necessary.

In a further embodiment of the system, a Data exchange between the electronic controllers from Towing vehicle and trailer, for example, on a general serial data line or a standardized Bus system (e.g. CAN bus). This has the advantage that signals which, for example, in the towing vehicle Standard control system, such as ESP, directly through sensors or indirectly via mathematical links, such as model calculations, Observer solutions and signal estimates are also recorded Regulator can be made available in the trailer. By this controller can then brake on one or both Wheels of the trailer can be controlled.

The detection of an impending unstable or critical driving condition of the trailer takes place via the evaluation of characteristic signal patterns according to FIG. 1.

Both conventional signals such as the Wheel speeds when using an ABS or the Lateral acceleration or yaw rate used in the case of an ESP become.

In an exemplary minimum Embodiment 1, a lateral acceleration sensor is shown in FIG. Provided which is preferably mounted far forward or too far back on the trailer.

The detection algorithm is based on that typical Vibration pattern of the signals (in this case the Lateral acceleration) and extreme lateral dynamics of the team can be detected.

In order to evaluate the vibration patterns, local maxima and minima of lateral acceleration to determine the Pendulum phase of the trailer used without a Speed of rotation or angle of rotation around a momentary pole etc. must be determined.

Fig. 1 shows the typical waveform 1 shows a lateral acceleration sensor which is mounted at the rear end of the trailer for a trailer aufschaukelndes.

With this exemplary configuration the Detection mechanism explained, which in principle applies to any Sensor configurations can be expanded.

A first detection of an impending oscillation is already possible after a half wave, that is to say after the time DT_h or at the time t_min1 ( 3 ) in FIG. 1. After a complete oscillation period, that is to say the time DT_f or at the time t_max2 ( 4 ) in FIG. 1, it can be assumed with greater certainty that the roll is present. In order to classify the situation as dangerous, the vibration must have a certain minimum vibration range, which can be made dependent on various driving conditions. An (estimated) vehicle speed is used as an essential parameter for this purpose if the recognition mechanism has access to it, that is to say, for example, it is housed in the control unit of an ABS or ESP.

The vibration ranges are determined in the following steps:

The value of the lateral acceleration a_y (signal 1 ) at time t_max1 ( 2 ) is stored as maximum value a_max_old (value 7), where a_y assumes a local maximum. At the same time, the time t_max1, which is represented, for example, by the counter reading of an internal circulation counter, is also stored, specifically as the start value t_max_old.

a_max_old = a_y (t_max1)
t_max_old = t_max1

The value of a_y and the time t_min1 ( 3 ) at which a_y has a local minimum (value 8) are then stored as reference values a_min_old and t_min_old:

a_min_old = a_y (t_min1)
t_min_old = t_min1

The oscillation width A1 (value 12) is determined by forming the difference between a_max_old (value 7) and a_min_old (value 8):

A1 = a_max_old - a_min_old = a_y (t_max1) - a_y (t_min1)

By forming the difference between the two stored times ( 3 and 2 ) or the counter readings that represent them, the time interval DT_h results, which represents half the period of an oscillation:

DT_h = t_min_old - t_max_old = t_min1 - t_max1

If the value of DT_h lies in a typical band of, for example, 300-600 ms, the vibration range A1 is checked. If this exceeds a threshold A_thr which is classified as critical and which is calculated depending on the driving situation, preferably depending on the driving speed, an information flag F (signal 16 ) is set to logic '1', which indicates the recognized state of a roll.

DT_h> 300 ms and DT_h <600 ms and
A1> A_thr (v_Fzg)
→ F = 1

At the same time, a down counter REC_TIMER (signal 17 ) is set to a start value (value 18) and reduced by 1 in each subsequent control cycle until it has reached the value 0.

REC_TIMER = start value
REC_TIMER = REC_TIMER - 1 in every further cycle

The start value is set so that the counter REC_TIMER Values greater than 0 in a well-defined time interval T_rec having. As long as the counter REC_TIMER has not yet expired, the time T_rec has not yet passed, it is also checked whether vibrations occur in a_y. With each newly recognized vibration, the counter becomes REC_TIMER set back to the starting value.

When the counter reaches 0, there is no oscillation tendency and the flag F is reset to 0.

REC_TIMER = 0

→ F = 0

If the flag F has the value 1, the runs Detection mechanism continues as follows:

If there is again a local maximum of a_y (in the example of FIG. 1 at time t_max2 or time 4 ), the value a_y (value 9) is stored as a further reference value a_max, the associated time t_max2 ( 4 ) is stored in the memory t_max ,

a_max = a_y (t_max2)
t_max = t_max2

By forming the difference between the two stored times t_max ( 4 ) and t_max_old ( 2 ) or the counter readings that represent them, the time interval DT_f results, which represents the full period of an oscillation:

DT_f = t_max - t_max_old

Furthermore, a new vibration range A2 (value 13) is formed by forming the difference between the new maximum value a_max ( 9 ) and the previously stored minimum value a_min_old ( 8 ) of the lateral acceleration:

A2 = a_max - a_min_old = a_y (t_max2) - a_y (t_min1)

Is the value of DT_f in a typical band of for example 600-1200 ms, the oscillation width becomes A2 checked. If this is a threshold classified as critical Exceeds A_thr, the counter REC_TIMER will open again set the start value.

As long as an oscillation occurs again and again in a predetermined band and with a minimum oscillation width, the counter REC_TIMER is incremented again. As a result, the flag F remains at the value 1 and indicates a critical situation. Only when the oscillation subsides the oscillation patterns are no longer recognized, the counter REC_TIMER expires to 0, and the recognition flag F for the oscillation can be reset to 0.

DT_h> 300 ms and DT_h (600 ms and
A1> A_thr (v_Fzg)
→ F = 1

From the relation of the stored vibration widths A1 ( 12 ) and A2 ( 13 ) as well as all possibly still further stored vibration widths A3, A4. , , ( 14 , 15 ), it can be read whether an intervention that has taken place in the meantime has been successful, i.e. has led to the decay of the oscillation range, or whether a further increase in the oscillation range or the amplitude values signals that the problem persists and, if necessary, the dosage of one current intervention must be increased or the entire intervention strategy must be changed. For example, one could switch from individual brake interventions on the wheels of the trailer to braking both wheels at the same time. Such a measure stretches the team and reduces the overall dynamics. However, the driver perceives this intervention as a certain brake jerk, which noticeably reduces the driving speed. Therefore, braking on both sides should only be carried out when there is an increased risk and if possible only briefly, so that the driver is not deprived of global control of the vehicle.

Fig. 2 illustrates the increased detection reliability when using two lateral acceleration sensors, which are far apart, in this case attached to the front and rear of the trailer. The signal 20 of the sensor attached to the rear end of the trailer is referred to below as a_y_r (rear) and the signal 21 of the front sensor as a_y_f (front).

Due to the opposite phase of the signals, superimposed offset values that result from cornering can be eliminated, for example by considering the halved difference between the two signals. This transverse acceleration component 23 is referred to here as the oscillation component:

a_y_osci = (a_y_r - a_y_f) / 2

At the same time, the superimposed lateral acceleration offset, which results from cornering, can be calculated by halving the sum of the two lateral acceleration signals. This portion 22 is referred to here as the stationary portion:

a_y_stat = (a_y_r + a_y_f) / 2

However, a curve offset can also be eliminated with a sensor or a superimposed cornering can be recognized on the basis of the measured offset by using successive maxima and minima of the one available lateral acceleration signal:

a_y_osci = (a_y_max - a_y_min) / 2

and

a_y_stat = (a_y_max + a_y_min) / 2

While one with two transverse acceleration sensors this Determine signals always up-to-date in every new control cycle can, the signals with only one Only update the lateral acceleration sensor when it is on again new maximum or minimum detected in the signal curve could be.

The detection of the roll can be done without additional Sensor effort also take place in a vehicle that for example, is only equipped with a pure ABS control unit. In this case you take the speeds of two wheels an axis that is not driven, if possible, and forms its axis Difference.

For a front-wheel drive vehicle, the rear wheel speeds result in:

v_diff = v_rl - v_rr

with v_rl = speed of the left rear wheel (rear left)
and v_rr = speed of the right rear wheel (rear right).

For a rear-wheel drive vehicle, the front wheel speeds result accordingly:

v_diff = v_fl - v_fr

with v_fl = speed of the left front wheel (front left)
and v_fr = speed of the right front wheel (front right).

The signal v_diff also shows a clear oscillation in the event of a vehicle rolling - similar to a lateral acceleration signal. However, the amplitudes to be expected at the differential speed are quite small. When driving straight ahead, the differential speed v_diff oscillates around the zero point. In the case of cornering, however, v_diff itself also contains an offset value v_diff_stat, which corresponds to the degree of cornering and results from the lateral acceleration a_y, the longitudinal speed v_x and the track width s_track of the vehicle:

v_diff_stat = a_y.s_track / v_x

In order to eliminate the offset v_diff_stat so that the oscillation component in the differential speed can be determined, the procedure can again be the same as in the case of a lateral acceleration sensor, i.e. maxima and minima are noted in the signal curve and their halved difference is used as a useful signal for the oscillation, while half the sum represents the curve offset value again. The lateral acceleration a_y is calculated from the latter using the above equation:

a_y = v_diff_stat.v_x / s_track

In this way, a signal is sent for each sensor configuration (or several signals) determines that an oscillation and so that represents a vehicle roll. In any case Maxima and minima of this signal noted, from their Differences in vibration widths and from their time intervals Period times according to the example above with a Transverse acceleration sensor formed. If the period times show that the vibrations are in a typical band and the Vibration widths exceed critical threshold values, a safety-critical state is considered recognized, so that a regulatory intervention by the implemented System is initiated.

By choosing the detection thresholds for the Vibration ranges can also be done very early before the driver of the team considered the situation uncomfortable feels. In this case, the system is sure to be common intervene so that such a sensitive threshold setting for example, should be selected for systems whose Intervention by the driver is not, or at least not, disturbing is perceived. So sensitive thresholds can for example in vehicles with electric brakes (Brake-bywire systems) are used by the driver experienced haptic feedback in the brake pedal.

After a roll of the vehicle through one of the above. Detection mechanisms have been detected must be appropriate Interventions, for example, by actively braking on Towing vehicle or on the trailer.

In the simplest case, after the Lurching a short brake on all wheels of the Towing vehicle. This intervention does not require any special Timing. It is triggered whenever a critical Lurch over a defined threshold of the vibration range has been recognized and remains either via a predefined Vehicle speed-dependent time is active or remains that way active for a long time until the roll is no longer detected or the amplitude of the oscillation in the considered reference signal falls below a lower threshold, which is lower than the control entry threshold (hysteresis).

In a second version, the tendencies towards rocking through targeted, precisely timed brake interventions suppressed one or both wheels of the trailer.

The invention provides for the intervention times (the Times at which the respective pressure build-up is started) depending on the required maximum pressure (or the required maximum braking force) and the actuator speed determine.

Fig. 3 shows again to the simple example where only one transverse acceleration sensor is used at the rear of the trailer (signal 30). It is assumed that the yaw rate psip of the trailer about its vertical axis (signal 31 ) assumes maximum values whenever the lateral acceleration signal corrected for the curve offset has zero crossings. At these times, the brake pressures P_l and P_r (signals 36 and 39 ) individually fed to the wheels should also assume maximum values in order to dampen the vibration process. Since the brake actuators have finite pressure or force build-up gradients, a small time range is set around each zero crossing of a_y, in each of which a brake pressure or a braking force is fed to a wheel of the trailer. In the example of FIG. 3, these are the hatched time ranges 32 , 33 , 34 , and 35 .

If a slow actuator is used, the pressure must be built up early so that the maximum wheel pressure is reached in time before the signal a_y has a zero crossing. In addition, the pressure build-up must start earlier, the greater the desired maximum pressure P_max des (value 37). This results in the following calculation for the starting point t_start (for example time 38 ) for the pressure build-up:

t_start = t_pinc - P_max des / P_grad

P_grad is the mean pressure build-up gradient (slope of the pressure build-up ramp 40 ) that can be applied by the actuator used and is considered to be the known and largely constant size of the actuator. P_max des (value 37) results as the setpoint from the control algorithm used.

t_pinc is the point in time at which the maximum wheel pressure is to be built up and is a fixed amount of time (for example approx. 100 ms) before the point in time t_zero of the next expected zero crossing of the lateral acceleration-adjusted lateral acceleration signal,

t_pinc = t_zero - 100 ms

Since the time of the next t_zero is initially unknown, an estimate must be made based on the previous oscillation period (see Fig. 3):

t_zero (estimated) = t_max_old + (t_min_old - t_max_old) / 2

or in the event that a maximum was last recognized in a_y:

t_zero (estimated) = t_min_old + (t_max_old - t_min_old) / 2

After the occurrence of several vibrations, a previously determined mean or filtered period is determined and used as the basis for estimating the occurrence time of the next vibration maximum:
This measure makes the prediction of t_zero more precise.

In a first embodiment of the invention, there is active braking on the wheels of the trailer. This can be done on a wheel true to phase, starting at temporal reference points of the lateral acceleration pattern, these reference points t_start (for example time 38 ) being calculated depending on the situation depending on the actuator dynamics and the necessary pressure level (in accordance with the example in FIG. 3).

In critical cases, braking on both sides of the Trailer wheels are made.

Claims (11)

1. A method for monitoring motor vehicles with trailers for instabilities, in which the rolling movements carried out by the vehicle and / or trailer are measured with at least one lateral acceleration sensor or wheel speed sensors and are evaluated to determine control variables for a control system, characterized in that on the basis of measurement variables (a_y _(tmax1 ), tmax1, ay _(tmin1) , tmin1, a_y _(tmax2) , tmax2, a_y _(tmin2) , tmin2, v_rr, v_rl, v_fr, v_fl), using the lateral acceleration sensor or the wheel speed sensors and at least one counter were determined and which reflect the positive and negative amplitude as well as half the period (DT_h), including at least one band for half (DT_h) or the entire period (DT_f), the vibration range (A1, A2, A3, ect.) with a Threshold value (A_thr) is compared and the comparison result for the detection of roll movements is evaluated. 2. The method according to claim 1, characterized in that a roll movement takes place and a counter (Rec_Timer) is started when the following conditions are met:
The vibration range A (1, 2, 3 ect.)> A_thr
Half or the entire period (DT_h, DT_f) lies within the band. 3. The method according to claim 2, characterized in that the value of the counter (Rec_Timer) to a start value is set. 4. The method according to claim 2, characterized in that the counter (Rec_Timer) depending on one elapsed time (T_rec) is reduced. 5. The method according to claim 4, characterized in that the value of the counter (Rec_Timer) to the start value is reset if a within the time (T_rec) Rolling motion is recognized. 6. The method according to claim 1 or 2, characterized characterized in that the limit value (A_thr) according to the Driving situation, preferably the vehicle speed, is appreciated. 7. The method according to claim 1, characterized in that the lateral acceleration component resulting from cornering is determined in a model and the value of the lateral acceleration ((a_y _(tmax) , a_y _(tmin) , ay _(tmax2) , a_y _(tmin2) ect. ) is corrected with the lateral acceleration offset determined in the model. 8. The method according to claim 1 or 2, characterized in that brake interventions are initiated on at least one wheel of the trailer if the following conditions are met:
The vibration range A (1, 2, 3 ect.)> A_thr
Half or the entire period (DT_h, DT_f) lies within the band. 9. The method according to claim 8, characterized in that the braking intervention according to the maximum braking pressure or the maximum braking force and Actuator speed is determined. 10. The method according to claim 8 or 9, characterized characterized in that the brake intervention in a time window around the Zero crossing of the curve offset adjusted Lateral acceleration signal takes place. 11. The method according to claim 10, characterized in that the time of intervention in a model according to the relationship

t_start = T_pinc - P_max of / P_grad is determined, with P grad = the mean pressure build-up gradient of the pressure build-up pump, P_max des = the brake pressure setpoint, t_pinc = the setpoint at which the P_max des is to be reached, with t_pinc = t_zero - t_stat ms, with t_ = fixed amount of time, e.g. B. 100 ms and t_zero = next expected zero crossing of the curve-offset-adjusted lateral acceleration signal.