DE19638511A1 - Speed and spacing control system for road vehicles - Google Patents

Abstract

The driving control enables the driver to set a spacing he is comfortable with relative to the vehicle ahead. The control system adjusts this set spacing in relation to the vehicle speed as well as in relation to information of the road ahead. The latter is obtained from a navigation system. The control measures the actual spacing and compares it with the nominal values, as derived from the vehicle parameters. The control slows the vehicle if the spacing decreases to a safety limit. The control system also monitors the relative angles of the leading vehicle to the control vehicle. This enables the control to determine if the leading vehicle is in the same track as the control vehicle, and allows safe overtaking.

Description

The invention relates to a method and a device for longitudinal regulation of a vehicle according to 5. the preamble of claim 1.

The longitudinal control systems of the generic type are longitudinal guidance systems which are designed, for example, as so-called cruise controls. Cruise control the vehicle driving internal combustion engine so that a set speed as a predetermined parameter is observed. Other longitudinal guidance systems use as a controlled variable in addition to the Vehicle speed also the distance to the vehicle in front: as soon as one a vehicle in front is detected, a target distance is calculated, and this target distance is instead of the selected speed as soon as the distance to the vehicle in front Vehicle becomes smaller than the target distance.

Compared to the present state, it is the object of the invention, a method and a device to create longitudinal control of a vehicle, which with regard to driving safety longitudinal control system is improved.

This object is achieved with the features of claim 1. According to the proposed The method provides for the course of the road in a first step in a longitudinal control system in front of your own vehicle using a navigation system and in a second step adapt the default value of the parameter to the determined frictional engagement state. Such Adjustment can be made in a longitudinal control system for the distance to a vehicle in front the way that the position of the vehicle in front with respect to the distance and the angle to your own vehicle, compared this position with the course of the road and the Distance to the vehicle in front is limited to a minimum value if the comparison shows that the vehicle in front is on the same lane as your own vehicle located. This makes it possible in a particularly simple manner for a distance-oriented one Longitudinal control system to identify the vehicle actually driving ahead in its own lane and ensure compliance with the minimum distance to this vehicle.

Another possible adjustment for a longitudinal control system consists in the adjustment of the set Speed as a given parameter in such a way that the Radius of curvature of the road is determined and subsequently from this in connection with a maximum permissible lateral acceleration is a maximum permissible speed for your own vehicle is calculated. The set speed can then optionally be at this maximum Speed can be limited. This ensures that one for a straight lane set target speed is not maintained even on a curved route if this  Speed would bring the vehicle into an unstable driving state. Can advantageously in addition to determining the maximum lateral acceleration, the power flow condition of the road detected and used to determine the maximum lateral acceleration.

While the method according to the invention preferably for integration into a program-controlled Control device of the vehicle is suitable, the invention can of course also under Maintaining the aforementioned advantages and effects can be represented as a discrete circuit.

The invention is based on the knowledge that jumps in the course of the road, d. H. Curves, too lead safety-critical driving situations that are not with on-board means of a motor vehicle are predictable. To get additional information on the course of the lane is therefore on Information used as it is provided by navigation systems. This Navigation systems contain digitized road map information, for the present The following information is particularly important to the invention:

• - Road course or curve radius of the road
• - curve direction
• - Left-hand or right-hand traffic

Within the scope of the invention, the following additional information, if available, can include additional information Benefit:

• - Number and width of the lanes
• - Street type (e.g. country road, federal road etc.)
• - speed limits
• - inclines or descents
• - Inclinations or exaggerations

It has been shown that the foresight in a window from about 200 m to 300 m in front of the vehicle must take place in order to be able to react to the information. In particular with regard to the It is also sensible to obtain precise data on the course of the curve, up to the course of the road 600 m in front of the vehicle, so that the curve at the edge of the Observation window can be secured by knowledge of the subsequent course of the road can. As an alternative or in addition, the course of the lane can also be up to approx. 300 m behind the vehicle determined and compared with the vehicle movements, so as to the actual position of the Vehicle and thus the actual current lane course with greater accuracy to be able to determine.  

The invention is described in more detail below on the basis of the exemplary embodiment shown in the figures explained.

Show it

Fig. 1 consecutively propelled in a diagram of two vehicles to illustrate the effect of the invention,

Fig. 2 is a flowchart of the method according to the invention and

Fig. 3 is a block diagram of the device according to the invention.

The driving situation on which the invention is based will be briefly explained with the aid of the diagram according to FIG. 1. A road 1 has two lanes 2 , 3 in one direction of travel. On the right-hand lane 3 there is a first vehicle 4 that is driving in front of a second vehicle 5 . The second vehicle 5 is your own vehicle. Also in front of the second vehicle 5 is a third vehicle 6 on the left lane 2 . The vehicles each have different speeds v₁ to v₃ and different accelerations a₁ to a₃, of which the speed v₂ and the acceleration a₂ of the second vehicle 5 are entered only as an example in FIG. 1. In the front area of the second vehicle 5 , a distance sensor 7 is arranged, which has a distance d 1 to the third vehicle 6 , a distance d 2 to the first vehicle 4 and an angle w 1 between a longitudinal axis L of the second vehicle 5 and the third vehicle 6 and an angle w 2 determined between the longitudinal axis L and the first vehicle 4 .

The second vehicle 5 is provided with a distance controller 8 , which adjusts a parameter for longitudinal control, ie for guiding the vehicle in the longitudinal direction, to a preset value. The distance controller 8 uses the power control, here the control of the throttle valve, of an internal combustion engine driving the vehicle 5 as a manipulated variable for influencing this parameter. When driving freely, ie as long as no vehicle 4 driving ahead is detected, the parameter for longitudinal control is the speed v 2 of vehicle 5 . The default value to this, v as the setpoint speed by the driver or by other means _to be adjusted. As soon as a preceding vehicle 4 is recognized, the parameter for longitudinal control is the distance d from the preceding vehicle 4 . The distance controller 8 calculates from the speed v₂ of the own vehicle 5 and the differential speed dv = v₂ - v₁ the car and the first vehicle 4 is a set distance d _should and passes from the control of the speed V₂ for the regulation of the distance d₂, as soon as the distance d₂ the target distance d should be reached or less.

Fig. 2 shows a flow diagram of an exemplary embodiment of the inventive method, for example as part of a program-controlled distance controller 8 or any other longitudinal control unit. This part of the program begins with a step 20, in which the position of one's own vehicle 5 is determined with the aid of a navigation system. The navigation system should preferably determine its own position by determining the absolute position, as is the case with the GPS navigation system. In step 21, the course of the road is determined in a region of approximately 200 m in front of one's own vehicle 5 using a stored road map. In step 22 it is checked whether the distance controller or the speed controller is currently activated. When the distance controller is activated, the program continues with step 23, in which the distances d 1 and d 2 as well as angles w 1 and w 2 to the preceding vehicles 4 , 6 are determined with the aid of the distance measuring device 7 . In step 24, the positions d₁ and d₂ and the angles w₁, w₂ determine the position of the first or third vehicle 4 or 6 in front of the vehicle 5 relative to them, and subsequently in step 25 using the stored road map, on which Lane is the first vehicle 4 or the third vehicle 6 . In step 26, a comparison is made for which vehicle 4 , 6 the determined lane is identical to the own lane (in the exemplary embodiment, the right lane 3 ). In step 27, the distance d₂ to the first vehicle 4 , which is located on the same lane 3 as the driver's own vehicle 5, is set as the variable d _{to be} adjusted for the distance controller 8 , provided that the target distance d target is smaller than the current distance d₂ .

If, on the other hand, the query in step 22 has shown that it is not the distance controller but the speed controller that is active, the program proceeds to step 28 after the query 22 . In step 28, the radius of curvature of one's own lane 3 is determined from the previously determined road course. If more than one curvature is present in the detected course of the road, the smallest radius of curvature r is selected. In step 29, the state of adhesion u between the road 3 and the own vehicle 5 is detected. A possible procedure for detecting this force-locking state u and a more precise definition of the same are described in DE 42 18 034 A1 "Method for determining a force-locking potential of a vehicle", to which reference is expressly made here. This is followed by a step 30, in which a limit value v _max for the speed of one's own vehicle 5 is determined depending on the state of adhesion u and the radius of curvature r. This limit value v _max corresponds to the speed v at which the narrowest of the curves lying in the course of the road can be traversed without exceeding a permissible maximum value a _max for a transverse acceleration a 2 of one's own vehicle 5 . Finally, in step 31, the setpoint speed v target given to the distance controller 8 _is limited to the previously determined limit value v _max .

To simplify matters, it can be provided not to provide step 29, but instead to use an empirically determined value for the adhesion state u in step 30 to calculate the limit value v _max . However, this is associated with the restriction that, for safety reasons, this value for the frictional engagement state u must be set in the lower range of the values normally occurring and it is left to the driver in the event of a rapid deterioration in the frictional engagement conditions, such as e.g. B. by rain or snow, turn off the distance controller 8 on your own responsibility.

It is equally possible to execute the sequences of the steps 23 to 27 and 28 parallel to 31 and to specify that size to the longitudinal control in which the adjusted default value _to d, v _soll is strongest below.

If necessary, the longitudinal control system described can of course also be shown in the form of a circuit, as shown below with reference to the block diagram shown in FIG. 3.

The distance controller 8 receives the vehicle speed signal v₂ from a speed sensor 41. A signal for the vehicle deceleration a₂ is obtained therefrom by a differentiator 42 . A distance sensor 43 supplies signals d _i for the distance to the vehicles 4 , 6 in front and signals w _i for the angle between the longitudinal axis L of the vehicle 5 and the vehicles 4 , 6 in front. Since there are several vehicles 4 , 6 in front, the signals d _i , w _{i are determined} for each of these vehicles 4, 6 . However, the setting of the default value in particular for the target speed is possibly also _{intended to} target distance d for those carried out by the driver by means of an adjusting device 44, such as a steering column switch. Specifically, the target distance d _should also can be determined within the distance controller 8 automatically, so that the driver-set speed _to only the setting of v must be done. On the output side, the distance controller 8 actuates a throttle valve 45 for controlling the power of an internal combustion engine (not shown in more detail) of one's own vehicle 5 by means of a signal DK.

As a further external signal transmitter, a sensor 46 is provided for detecting the adhesion state u of the vehicle, which preferably works according to the principle shown in DE 42 18 034 A1. Finally, a navigation system 47 is provided, which determines the geographic position of one's own vehicle 5 . In the present case, the navigation system 47 works on the basis of the global positioning system (GPS), which receives signals from satellites 48 and evaluates them to determine the location.

At a distance regulator 8, a digitized road map 49 as well as the actual series regulator 50 are provided, wherein the series regulator 50 according to the invention, a matching device 51 _to d for adjusting the default value shall have for the series regulator 50th The road map 49 provides information about the course of the street 1 in front of the position of one's own vehicle 5 , in particular also with regard to the curvature r of the street and the course of lanes 2, 3 within the street 1 .

In Figs. 4 and 5 show two embodiments of the adjusting means 51 are shown below. In the first exemplary embodiment shown in FIG. 4, the adaptation device 51 has a determination unit 52 , a comparator 53 , a computing device 54 and a limiting device 55 . The determination unit 52 determines the position of the own vehicle 5 and the position of the preceding vehicles 4 , 6 from the data supplied by the road map 49 and with the aid of the signals distance d _i and angle w _i supplied by the distance transmitter 43 . In comparator 53 , this information is linked to the information obtained from road map 49 in such a way that it is checked whether one of the vehicles 4 , 6 in front is in the same lane 3 as one's own vehicle 5 . The comparator 53 now passes the distance information d 1 regarding the vehicle which is in the same lane 3 (here the vehicle 4 ) to the limiting device 55 . The limiting device 55 also receives a lower limit value for the distance to the vehicle in front d _min from the computing device 54 , which calculates the minimum value d _min on the basis of the current driving speed v 2 of the own vehicle 5 . This calculation is based on a safety distance, which is to be maintained with an average non-slip road and the given speed v₂ of the own vehicle to the vehicle 4 in front, in order to bring the vehicle 5 to a stop in good time even in the event of an emergency braking of the vehicle 4 in front. The limiting device 55 acts in such a way that the default value d _soll for the series regulator 50 is limited to the lower limit value for the distance to the vehicle in front d _min . The setting of the default value d _{should be} made in the longitudinal controller 50 for the distance to the vehicle in front.

The second embodiment of the comparison device 51 , as shown in FIG. 5, is supplemented by a further computing device 56 , which has a maximum value for the longitudinal acceleration of the vehicle a _max and a maximum value for the lateral acceleration of the vehicle aq _max depending on the prevailing force-locking condition u determined. Furthermore, an evaluation device 57 supplies the value of the smallest curve radius r _min for the course of the roadway 3 , which lies in the area of the road course monitored in front of one's own vehicle 5 in the direction of travel. From this, the computing device 54 calculates the limit values d _min and v _max for the default value of the series regulator 50 , which is then passed on to the limiting device 55 . A minimum distance d _min to the vehicle 4 in front is calculated as the first limit value, this calculation, in contrast to the first exemplary embodiment, taking into account an average non-slip road but the current adhesion state u. Furthermore, a maximum speed v _max is calculated on the basis of the current state of adhesion u and the smallest curve radius r _min .

Claims (8)

1. Method for longitudinal control of a vehicle with the steps

• Setting a default value of a parameter for longitudinal control, in particular a distance (d _target ) to a vehicle in front or a speed (v _target ) of one's own vehicle,
• - correcting the difference (dv) between an actual value of the parameter and the default value of the parameter,
  characterized by the following steps:
• - recording the course of the road at least in front of one's own vehicle with the aid of a navigation system,
• - Adapting the default value (v _soll , d _soll ) to the course of the road.

2. The method according to claim 1, characterized by the following steps for adapting the default value to the course of the road:

• Determining the position of the preceding vehicle at least with regard to the distance (d) and the angle to the own vehicle,
• - comparison of the position of the vehicle in front with the course of the road,
• - Setting the distance (d _soll ) to a vehicle in front by the longitudinal control, if the comparison shows that the vehicle in front is on the same lane as the own vehicle.

3. The method according to claim 1 or 2, characterized by the following steps for adapting the default value to the course of the road:

• - determining a radius of curvature (r) of the road from the course of the road,
• Calculating a limit value for the speed (v _max ) of the own vehicle from a predetermined limit value for the lateral acceleration (a _{max of} the own vehicle and the radius of curvature,
• - comparison of the speed (v) of one's own vehicle with the limit value (v _max ),
• - Limiting the speed (v) of your own vehicle (v _soll ) as a default value for longitudinal control to the limit value (v _max ).

4. The method according to claim 3, characterized by the following steps for determining the limit value for the lateral acceleration (a _max ) of the own vehicle:

• - detecting the state of adhesion (u) of the vehicle,
• - Calculate the limit value for the lateral acceleration (a _max ) of the own vehicle based on the present state of adhesion (u).

5. Device for longitudinal control of a vehicle, with an adjusting device ( 44 ) for a default value of a parameter for longitudinal control, in particular a distance to a vehicle in front (d _soll ) or a speed of the vehicle (v _soll ), and a longitudinal controller ( 50 ) for Correcting the difference between an actual value of the parameter and the default value of the parameter, characterized in that means ( 49 ) for detecting the course of the road at least in front of one's own vehicle with the aid of a navigation system ( 47 ) and a device ( 51 ) for adjusting the default value also depend are provided by the course of the road. 6. The device according to claim 5, characterized in that the device ( 51 ) for adapting the default value to the course of the road, a determination unit ( 32 ) for determining the position of the preceding vehicle at least with respect to the distance (d) and the angle to the own vehicle, a Comparison device for comparing the position of the preceding vehicle with the course of the road and a limiting device ( 35 ) for limiting the distance (d _soll ) to a preceding vehicle to a minimum value (d _min ) if the preceding vehicle is on the same lane as the own vehicle , having. 7. The device according to claim 5 or 6, characterized in that the device ( 26 ) for adapting the default value to the course of the road means for determining a radius of curvature (r) of the road from the course of the road, a calculation unit for calculating a limit value for the speed ( v _max ) of the own vehicle from a predetermined limit value for the lateral acceleration (a _max ) of the own vehicle and the radius of curvature, a comparison unit for comparing the speed (v) of the own vehicle with the limit value (v _max ) and a limiting unit for limiting the default value (v _soll ) to a limit value (v _max ). 8. The device according to claim 7, characterized in that means ( 46 ) for detecting the adhesion state (u) of the vehicle and a calculation unit for calculating the limit value for the lateral acceleration (a _max ) of the own vehicle depending on the present adhesion state (u) are.