DE4201142C2 - Driving speed limiting device - Google Patents

Description

The invention relates to a driving speed boundary device with the features of the preamble of Claim 1.

In recent years, different types of automa table-controlled, electronic driving systems known which have been developed to enable drivers to move, drive safely and comfortably, independently of their driving technique and driving experience. For example automatically delay vehicle distance control devices a motor vehicle and give an alarm if that force vehicle a distance from the vehicle in front comes, which is shorter than a safety distance, which corresponds to a vehicle speed at which the Motor vehicle is currently driving.

To increase driving safety, motor vehicles must Art controlled that a security speed depending on the road condition as well as a safe safety distance between two motor vehicles is maintained. If, for example, a motor vehicle before a sharp cure ve first on a straight line with proportionate drives at high speed and wants to take the curve, should be the driving speed before the motor vehicle enters enters the curve at a suitable approach speed  to be reduced under the Reiseege speed lies, corresponding to a radius of a sharp fen curve before a curve approach point is reached. When the car turns into a sharp curve with a higher Speed as the appropriate approach speed if it goes in, it may be through Zen centrifugal force carried out of the curve, which vice versa returns proportional to the radius of the curve with the square of Driving speed increases. However, if a curve is confusing or blind on the way, it is difficult rig to estimate the radius of the blind curve. When a Curve on the way, although it is sufficiently clear to oversee hen is icy or to estimate the radius of the curve is wet, a safe journey is only guaranteed if the motor vehicle at a lower speed than at the speed that drives into the curve can be estimated visually if only the curve radius in Is considered. Such an estimate of a radius and a speed is difficult while driving with sufficient accuracy and speed feasible.

A carriage is from the generic WO 88/05199 A1 speed limiting device for a motor vehicle become known in which a navigation device he knows when the motor vehicle is on a path section approaches a curve and has reached that curve, and then to a control device safety-relevant information delivers over the curve, based on which the Fahrge speed can be adjusted. The security relevant information stored in a memory are, for example, contain one for the curve given maximum speed.

DE 38 19 215 A1 describes a driving speed indicator boundary device known, in which the respective state location of the vehicle by a navigation device dig determined and thus the route is tracked. About the actual speed value passes through an ex Remote control center depending on the location setpoint, a warning device is actuated and a decrease in the driving speed of the motor vehicle sat triggered. However, the speed setpoint will without considering individual parameters, and curve detection by the navigation device does not happen.

From the Thoone, M.L.G .: "Carin, a car in formation and navigation system "in Philips Technical Re view Vol. 43, No. 11/12, Dec. 1987, is a navigation pre direction known for a motor vehicle, which is constantly Location determined and the driver via an acoustic off giving driving directions.

The invention has for its object a generic speed limiting device to create one in a simple way by each Prescribes driving speed dependent on cornering conditions.

This task becomes with the generic driving speed speed limiting device according to the invention solved by that the information about the curve at least the crumb contains radius and that the control device due the information provided by the navigation device NEN a limit speed at which the motor vehicle can safely negotiate the curve, calculated and as Ge speed setpoint.  

Advantageous embodiments of the invention are in the Un specified claims.

The invention is described below, for example, using the Drawing described; in this show:

Fig. 1 is a block diagram of a vehicle speed limiting device according to a Favor th embodiment of the invention;

FIG. 2 is a block diagram illustrating a vehicle navigation system using a global positioning satellite system in connection with the vehicle speed limit device shown in FIG. 1;

Fig. 3 is a block diagram illustrating a Fahrzeugort- detector means;

Fig. 4 and Fig. 5 representations of the principles of the vehicle location;

FIG. 6 is a flowchart illustrating an operation sequence of the vehicle navigation system shown in FIG. 2;

Fig. 7 is a flowchart illustrating a vehicle speed control sequence of the vehicle speed limiting device shown in Fig. 1;

Fig. 8 is an illustration of the operation of the vehicle speed limiting device shown in Fig. 1 and

According to the drawing and in particular according to FIG. 1, a vehicle speed limiting device according to a preferred embodiment of the invention, which cooperates with a vehicle navigation system, has a control device or the control device 23 . The control device 23 receives signals which are representative of the road condition, for example the road temperature and the humidity and the vehicle speed, the signals being supplied by a temperature sensor 29 , a humidity sensor 25 and a speed sensor 24 . The control device 23 also receives signals from a vehicle navigation system 22 , so that the necessary information about the road, which is required to guide the vehicle to a desired destination, is shown on a screen 6 , for example on a liquid crystal -An display device which is arranged in an instrument panel of the vehicle. On the basis of the signals and information from the sensors 24 , 25 and 29 and from the vehicle navigation system 22 , the control device 23 actuates various elements, for example a brake actuating element 26 , a throttle valve actuating element 27 and a warning device.

The vehicle navigation system 22 is shown in FIG. 2 Darge. USAGE The vehicle navigation system of FIG. 2 det the GPS (Global Positioning System), in which position data of satellites ge sends be. The vehicle navigation system 22 has a navigation control unit 10 which has a central computer 11 (CPU), a read-only memory 12 (ROM) for receiving a control program and a memory with direct access 13 (RAM) for receiving various control data. The central computer 11 is connected via a matching device 14 to various external units, which will be described later, in order to be able to exchange information between them. As external or external units with the navigation control unit 10 in the vehicle, a CD player 2 , a control switch unit 3 , a vehicle sensor 4 , a liquid crystal display 6 and an audio unit 9 are connected. The CD turntable 2 , which is connected to the navigation control unit 10 via a decoder 8 , drives a disk 1 (CD-ROM) as a read-only memory in which a large number of road maps are stored, which are of different sizes and reduced scale are stored, and has access to the disk 1 (CD-ROM) at a predetermined address, which is defined by a length Y and a width X, so that a desired road map can be read from the disk 1 (CD-ROM) and the data of the desired road map on the one hand to the central computer 11 via the decoder 8 and the adapting device 14 and on the other hand the audio unit 9 can be transmitted. The data for the central computer 11 are temporarily stored in the memory 13 with direct access. The control switch unit 3 , which is connected to the navigation control unit 10 via an encoder 16 , is used to set, reset and change a specific destination, change a desired route and change the command to display a specific map. The audio unit 9 , which is connected to the CD turntable 2 via the decoder 8 , has an amplifier, an equalizer, a loudspeaker, etc. The liquid crystal display device 6 , which is connected to the navigation control unit 10 via a display driver circuit 5 with a video memory 7 , illustrates a video image of a card which is read by the CD player 2 from the disk 1 (CD-ROM) . The vehicle location sensor 4 , which is connected directly to the navigation control unit 10 , determines a point Pn in the sense of width Xn and length Yn, where the vehicle is currently located.

In disk 1 (CD-ROM), the data of details of, for example, about 30,000 colored road maps are stored, corresponding to 15,000 sets of colored road maps, each set of maps of different sizes being reduced. The road map data includes at least details of roads, for example in the form of radii for curves, curvatures, bends and the like, in contrast to colored images.

The display switch unit 3 , which can be arranged as a switch device on a screen or can be designed in any other known way, has various switch functions, for example as a menu display, information display, destination reset, enlarged map display, normal sizes - Map display, point display and correction. Commands which are entered via the display switch unit 3 are encoded by the encoder 6 and then fed to the central computer 11 of the navigation control unit 10 via the adapter 14 . Depending on the commands, the central computer 11 carries out the necessary processing, for example to cause the display driver circuit 5 to display an image on the liquid crystal display device 6 .

As shown in Fig. 3 in detail, the vehicle detection sensor 4 has an extrapolation Navigationssy stem in the form of a first location sensing means 4 A, wel che utilizing the earth magnetism, and a GPS navigation system in the form of a second location sensing means 4 B. The first Vehicle location sensor device 4 A has, for example, an earth magnetic sensor 41 , for example a flux gate, in order to determine the direction of the earth's magnetism at a point where the vehicle is currently traveling, a vehicle speed sensor 42 , which serves to determine a speed in the form of a revolution To determine the wheel from which the vehicle speed and a covered distance can also be determined, a processing circuit 43 , the mode of operation of which is explained below in connection with FIG. 4, and which serves a point Pn in the form of width Xn and length Yn to determine where the vehicle is currently located This is because a distance D from a reference point Po (Xo, Yo) and a direction of the vehicle are determined. This is done so that the position of a point in relation to another point can easily be determined from the exact distance between the two points and a direction in which the one point is oriented.

To understand the basic principle that is used to find a location of a point relative to another point, consider a vehicle A that is viewed from a point A1, the location of which is the starting point or reference point Po , to another point An as the target point Pn, namely via points A2, A3,. . ., A9, as shown in FIG. 4, where at one direction (d) through the geomagnetic sensor 41 at any predetermined distance (A1-A2, A2-A3, A3-A4,..., A9-An ) of, for example, 5 m, which is derived from the number of wheel revolutions, which is sensed by the vehicle speed sensor 42 . Due to the distance or the distance (D) and the direction (d) of each point A2, A3,. . ., or On, a coordinate transformation is carried out relative to each preceding point in order to find the coordinates of the point in an orthogonal coordinate system, the east-west direction being the X coordinate axis and the north-south direction being the Y- Serve coordinate axis. A distance or a distance Dx between two adjacent points in the east-west direction is then determined from an equation Dx = Dcosd. Similarly, a distance or a distance Dy between two adjacent points in the north-south direction is calculated from an equation Dy = Dsind. The coordinates (Anx, Any) of the point An are determined by adding the distances Dx and Dy. In this way, the coordinates (Px, Py) of a target point Pn are determined.

The second location sensor device 4 B interacts with a global satellite positioning system, as illustrated in FIG. 5. Such a system is already in practical use. The global satellite positioning system has a ground control station 76 , which radiates a radio wave via a ground station antenna 75 , furthermore has at least 4, preferably 18 global positioning system satellites 77 A- 77 D, which serve to transmit the radio wave received, and further has a floor monitor station 85 to radio waves of the global Po sitionier sYSTEM satellites 77 a to receive 77 D, tungs- to rich or to determine bearing error coefficients may also be referred to as the azimuth error coefficient which indicate the magnitude of the bearing errors of the radio waves from the global positioning system satellites 77 A- 77 D. The bearing error coefficients are superimposed on the radio waves by the ground control station 76 .

As shown in FIG. 3, the second positioning is sensor means 4 B of the vehicle A, a radio wave receiving circuit 44, a second signal processing circuit 45, and a bearing error coefficient decision circuit 46. The second signal processing circuit 45 determines distances between the global positioning system satellites 77 A- 77 D and the vehicle A, a geographic latitude of the vehicle A and a time, based on radio waves from the global positioning system satellites 77 originate A- 77 D wherein the Ra diowellen 44 taken up by the radio wave receiving circuit to an absolute location to find Pn where the vehicle is currently located. The bearing error-Koeffizien th decision circuit 46 provides bearing error signals when the bearing error coefficients of the radio waves of the global positioning system satellites 77 A- 77 D are smaller than a predetermined value, which is expected in play because of the incorrect arrangement of the global positioning system satellites 77 a, when the on-vehicle a in a tunnel 77 is D and / or un zureichender field strength of the radio waves which are received by the radio wave receiving circuit 44, which may be caused in the pitch. The bearing error coefficients are classified into four levels, for example, which are represented by four geographical latitudes of the bearing error signals, namely the smallest width 0, a medium-small width 1 , a medium-sized width 2 and the largest width 3 .

The bearing error discriminator circuit 20 selects the second location sensor device 4 B if no larger width or bearing error signals 2 and 3 are supplied by the bearing error coefficient decision circuit 46 , or the first location sensor device 4 H if larger width or bearing error signals 2 and 3 3 are provided by the bearing error coefficient decision circuit 46 . The information of a vehicle location, which is supplied by the selected location sensor device, is transmitted to the central computer 11 , which is also referred to as a central processing unit and forms part of the navigation control unit 10 . The selection of the location sensor device by the DF error discriminator 20 , which can also be referred to as a switching device, is only effected if a map adaptation (which is described below) is not introduced.

In general it can be said that a bearing error, the size of which depends on the accuracy of the positioning method, inevitably occurs. Since such a positioning error is added up in particular when an extrapolation navigation system is used, a location of the vehicle may be displayed on an incorrect road on a road map displayed on a screen, which therefore does not correspond to the road on which this is being discussed stationary vehicle practically drives. For this reason, the navigation system with which the vehicle control system interacts performs a "map adjustment" to properly indicate the location of the vehicle on a road on the road map that is most likely to be virtually real on that road moves. The map adaptation is carried out after predetermined intervals or predetermined times, so that a display error of the vehicle location is corrected. To perform the map adjustment, all roads in the vicinity of the vehicle are listed, and information about the roads is read out from the fixed memory 13 to thereby determine the likelihood of any road on which the vehicle is practically running. A card adaptation program is stored in the central processing unit or the central computer 11 . While the map adaptation is being carried out, the switching device 20 selects both the first and the second location sensor devices 4 A and 4 B, so that vehicle location information is fed to the central computer 11 . The vehicle location information is evaluated in a selective manner, depending on the levels 0, 1, 2 and 3 of the direction finding error signal, in order to carry out a map adjustment in a stable manner. The navigation control unit 10 guides the vehicle in such a manner that it always follows the best route based on a relationship between a predetermined destination Pend and a current vehicle location Pn which is determined and displayed on a road map is displayed on the screen 6 .

Referring to FIG. 6, which illustrates a flowchart illustrating a proper route selection and a vehicle location display routine, the first process in step S1 is a disk 1 (CD-ROM) in the compact disk player 2 insert and operate the CD turntable 2 in such a way that the road map information is provided for reading. Before the vehicle A is started, a destination point Pend is entered via the control switch unit 3 and the vehicle location sensor 4 is activated to enter a starting point Po (Xo, Yo) in the memory with direct access 13 in step S2. Thereafter, a desired route between the starting point Po and the destination point Pend is set, and a road map is illustrated on which the starting point and a street along the desired route are displayed on the screen 6 . While the vehicle is running, the navigation system 22 properly marks a vehicle location, which is determined by the first and the second location sensor devices 4 A and 4 B, on the road map, with a map adjustment being carried out.

When the vehicle approaches a sharp curve or curvature 21 that has a small radius of curvature R, as illustrated in FIG. 8, on the way to the destination point Pend, the vehicle 90 must begin to initiate a deceleration or reduce its speed to a suitable vehicle limit speed VB, and this must be done at a suitable point A1 in front of the sharp curve 21 so that the vehicle can safely enter the sharp curve 21 . After the sharp curve 21 has been safely passed, the vehicle 90 accelerates or sets its speed up again, specifically in the region of the exit from curve 21 , and the vehicle then leaves curve 21 . This is a fundamental driving behavior, which could be described as "slowly in and quickly out". However, if a sharp curve or curvature has a very small radius of curvature and is smooth or icy, it is difficult to negotiate the curve safely and there is a risk of the vehicle being carried out of the curve. For this reason, the vehicle 90 should reduce its speed to a suitable limit speed VB, which is determined by the radius of curvature of the curve or curvature of a road and by the state of the road. However, if a curve is blind or confusing, it is very difficult to even roughly estimate the radius of curvature of the curve, making it difficult to estimate a suitable safety speed for the curve.

In the following, reference is made again to FIG. 1. The navigation system 22 shown there reads information about the radius of curvature R of a curve of a road as a function of a travel location Pn, which is determined by the vehicle location sensor 4 , and sends this information to the control device 23 . At the same time, the control device 23 receives signals which are representative of the road condition, for example the road temperature T and the humidity W, and the vehicle speed VA, corresponding signals being determined by a temperature sensor 29 , a humidity sensor 25 and a speed sensor 24 . On the basis of all signals and information about the road including the curve, the control device 23 calculates a vehicle limit speed VB, which is still permissible to safely go into the curve and to safely drive the vehicle through the curve through and out of the curve. If the actual vehicle speed VA is greater than the vehicle speed limit VB, the driver is given a warning signal by the warning device 28 or the brake actuation element 26 or the throttle valve actuation element 27 is actuated automatically, so that the vehicle speed VA is forced to the vehicle Limit speed VB is reduced. The operation of the vehicle speed control device 23 can best be understood with reference to FIG. 7, which is a flowchart illustrating a vehicle speed control sequence. It is state of the art to program a computer. The following description is intended to enable a programmer with average skill and knowledge to write a suitable program. The specific details of such a program would of course depend on the structure of the specially selected computer.

The first operation in step S1 is to input data of a vehicle location Pn (a point A1 in FIG. 8) at which the vehicle is currently located and further data of a radius of curvature R of a curve 21 which the vehicle is from the vehicle location Pn is approaching, and this data is input into the control device 23 from the vehicle navigation system 22 . After it has been indicated in step S2 that the vehicle is approaching a curve, the control device 23 receives a signal which is representative of the actual current vehicle speed VA from the speed sensor 24 , and furthermore data about the frictional resistance Fdo der Road surface from the vehicle navigation system 22 at step S3. Almost simultaneously, the control device 23 receives signals which are representative of the temperature T of the road and the humidity W of the road, respectively from the temperature sensor 29 and the humidity sensor 25 . This happens in step S4. Based on the temperature T of the road and the humidity or moisture W of the road and the frictional resistance Fdo of the road, the actual practical frictional resistance Fd is read out from a frictional resistance map. In the map, the frictional resistances are classified into, for example, three levels of practical frictional resistances Fd1, Fd2 and Fd3 depending on the road temperature T and the road humidity W, and taking into account the frictional resistance Fdo.

Then, in step S6, a vehicle speed limit VB is determined from the following equation:

VB = √g.R.Fd

When the vehicle speed VB at which the vehicle approaches curve 21 , which has a radius of curvature R, an angular speed w is expressed as follows:

w = VB / R

If g is used for the gravitational acceleration and m for the weight of the vehicle 90 , if the vehicle 90 , which is traveling at a vehicle speed VB at a point A2, is in dynamic equilibrium, the following equation is fulfilled:

Fd.mg = mR (VB / R) ²

If this equation is solved according to VB, the following relationship results:

VB = √g. R. Fd

The vehicle limit speed VB, which was determined in accordance with the radius of curvature R and the road conditions in curve 21 , allows the vehicle to safely drive through curve 21 .

At step S7, a decision is made as to whether a vehicle speed deviation dV, which corresponds to the difference between the actual vehicle speed VA and the vehicle limit speed VB, is still positive. If the answer to this question is "no", it indicates that the vehicle 90 has already reduced its speed below the vehicle limit speed VB before the curve 21 has been reached. Then the vehicle 90 is given permission to continuously continue at the vehicle speed VA. If the answer to the question asked is "yes", this indicates that the vehicle 90 must be decelerated. A further decision is then made in step S8 as to whether the vehicle speed deviation dV is greater than a predefined speed deviation dVo. The predefined speed deviation dVo has been set so that it can be eliminated by only closing the throttle valve of the machine. So if the answer to the decision in step S8 is "no", this indicates that the vehicle speed VA can be reduced below the vehicle limit speed VB by only closing the throttle valve. Then, the controller 23 causes the throttle valve actuator 27 to be operated to close the throttle valve in step S11. On the other hand, if the answer to the question in question in step S8 is "yes", this indicates that the vehicle cannot be slowed to or below the vehicle limit speed VB by closing the throttle valve. Then, the control device causes the brake actuation element 26 to forcefully brake the vehicle 90 in step S10, so that the vehicle speed VA in front of the curve 21 is reduced below the vehicle limit speed VB, immediately after the warning device 28 issues a warning in step S9 has been. This leads to the result that the vehicle can enter curve 21 with a lower than the vehicle limit speed VB, which was determined in accordance with the radius of curvature R and the road condition Fd of the curve, so that curve 21 can be safely driven through.

Claims (9)

1. Travel speed limiting device for a motor vehicle
with a vehicle-based navigation device that continuously determines the location of the motor vehicle and compares it with a road map,
with a device for specifying a location-dependent speed setpoint while the motor vehicle approaches a curve on a road,
with a driving speed sensor for delivering an actual speed value,
with a control device ( 23 ) which, when the location-specific predetermined speed setpoint is exceeded by the current speed actual value, actuates a warning device and / or triggers a reduction in the speed of the vehicle to the speed setpoint, and the navigation device then sends information about the curve to the control device ( 23 ) returns if the navigation device knows that the location of the motor vehicle is in front of this curve,
characterized by
that the information about the curve contains at least the radius of curvature,
that the control device ( 23 ), based on the information provided by the navigation device, calculates a limit speed at which the motor vehicle can safely negotiate the curve and specifies it as the speed setpoint. 2. Travel speed limiting device after Claim 1 characterized, that the vehicle speed limiting device the vehicle automatically brakes when driving speed is greater than the limit speed efficiency. 3. Driving speed limiting device after Claim 1 characterized, that the speed limit device tion automatically a throttle valve of the motor vehicle closes when the driving speed is higher than the limit speed. 4. Driving speed limiting device after Claim 1 characterized, that the information about the curve continues the Friction resistance of the curve indicates. 5. Vehicle speed limiting device according to claim 4, characterized in that the limit speed (VB) is determined from the following equation:
VB = √gRF,
where g is the acceleration due to gravity,
where R is the radius of curvature of the curve and
where F is the frictional resistance of the road. 6. Driving speed limiting device after Claim 5 characterized, that featured a road condition sensing device is to see a moisture and a tempera to determine the road. 7. Driving speed limiting device after Claim 6 characterized, that the total frictional resistance of the road a frictional resistance, a temperature and a moisture of the curve is determined. 8. Driving speed limiting device after Claim 1 characterized, that the vehicle has a satellite receiver indicates which of several global positions signals received by the satellite and from these the current vehicle status determined location.   9. Driving speed limiting device after Claim 1 characterized, that the vehicle has an earth magnetism sensor exhibits the earth's magnetism at one point determine where the vehicle is currently traveling, to take into account further data such as the distance traveled, the current vehicle determine location.