GB2381112A

GB2381112A - A method of guiding back a motor vehicle

Info

Publication number: GB2381112A
Application number: GB0218500A
Authority: GB
Inventors: Arne Friedrichs; Gerd Draeger; Michael Laedke; Volker Swarek
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2001-08-25
Filing date: 2002-08-09
Publication date: 2003-04-23
Anticipated expiration: 2022-08-09
Also published as: JP2003161631A; DE10141695A1; FR2828930A1; FR2828930B1; GB0218500D0; GB2381112B; JP4567280B2

Abstract

A method of guiding back a motor vehicle comprises the steps of recording position data of the vehicle when it deviates from a route until a known point of reference is reached and then guiding the vehicle back using the recorded data. The route may be indicated by arrows on a visual display or digital map. Recording of the data may be interrupted if consecutive positions are the same or slightly different. Recording may also be stopped when position inaccuracies exceed a specified level. The generated directional arrows may be determined on the basis of the speed of the vehicle and turning radii of both the route and vehicle.

Description

2381 1 12

DESCRIPTION

METHOD OF GUIDING BACK A NAVIGABLE

OBJECT AND A DEVICE THEREFOR

The invention relates to a method of guiding back a navigable object.

Navigation devices are known which guide vehicles on a previously calculated route. Navigation devices which have access to data material outside the route travailed are able to guide the user to the destination on an alternative route which must be newly calculated where appropriate. However, if the user is located outside of the digitised road network, then the user is generally requested to turn around immediately or the direction and distance to a known point on the route are indicated in the form of a compass dial.

In accordance with a first aspect of the present invention there is provided a method of guiding back a navigable object comprising: - using route data specified within an area for tracking purposes, - recording position data of the object at least when the object departs from the area specified by the route data, - recording the position data at least until a point of reference known from recording the position data is reached, and

- guiding the object back from the known point of reference using the recorded position data.

In accordance with a second aspect of the present invention there is provided a device for guiding back a navigable object comprising the following functional units: - a memory for a digital map, - a locating unit, - a position recording unit, - a module for identifying the status of an object, - a unit for producing a position track from the data of the position recording unit and from the data of the status identification, and - a tracking module.

The present method and device render it possible to guide a navigable object, in particular a motor vehicle, even outside of a digitised road network back to a known point on the route.

In particular, the invention makes use of the fact that in current navigation systems a previously travelled stretch of road (tracking) is automatically recorded over a specific period of time or a specific stretch of road. In the case of the invention, this tracking is advantageously used to guide the navigable object in the opposite

direction back to the last known point on the route which is still recorded, for example, on the digital map located on board a motor vehicle.

One advantage of the invention resides in the fact that the navigable object or the motor vehicle can also be guided to the destination when located in a non-

digitised area, in that it is guided back on the known stretch of road. Such characteristics are of particular interest if merely incomplete data bases for tracking to the destination are available to the motor vehicle driver as is the case for off-board navigation.

The invention can be utilised in a particularly advantageous manner in the situation where circumstances make it impossible to guide the navigable object back on the route just travelled, e.g. if it is not immediately possible to turn the vehicle around, on roads where turning is not allowed, on one-way streets or the like. In these cases, the motor vehicle driver initially drives around lost on the known road network, in order then to find a known point of reference from where he is able to return on the route already travelled. In the non-digitised area, i.e. when departing from the area specified by the route data, this procedure is assisted in accordance with the invention by virtue ofthe fact that as the object departs from the known area this unknown area is automatically digitised by a device dedicated to the object. If this device then finds a point of reference where the navigable device has already been, it is able to guide the object back.

The procedure of guiding the vehicle back is made easier in particular if the expected route data and the current object speed are used to generate directional arrows, which render it possible by means of tracking support to travel on the previously used track in the off-road area or on a track to be newly travelled on possibly within the digitised area.

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows tracking upon deviation from the specified route data; Figure 2 shows the guidance of the object back along a position line to a known point of reference; Figure 3 shows a device for guiding a navigable object back; and Figure 4 shows the guidance of the object by means of directional indicators. For the purpose of carrying out the invention, a navigation system is required which is able to guide a navigable object on a specified digital road network, or to provide the vehicle driver with corresponding tracking instructions within an area of specified route data. Furthermore, the navigation system must be able to record position data of the object, i.e. route data which can then be used to obtain

position data of the object/vehicle. In particular, this includes GPSpositions and/or direction of travel and stretch of road.

Upon departing from the known stretch of road 1 or network (of the area specified by the route data), the present method records the position data determined by the locating unit, so-called tracking (cf. Figure 1). This Backing 2 is recorded until one or several newly determined positions coincide(s) with position information already recorded in the memory. If the vehicle comes across at least one item of tracking information, the driver can be guided back safely along this position line to the known road network or to the route (cf. Figure 2).

Two examples will be used to explain the approach of guiding an object back utilising the invention: Example 1: A vehicle is guided by means of a navigation system and departs from the area covered by the digital map provided in the device, so that it is located in a non-digitised area. From the moment of departure from this area, the stretch of road travelled by the vehicle is recorded permanently, so that after turning around the vehicle can then be guided back on the same stretch of road. This procedure is performed by playing back the recorded stretch of road in reverse, e.g. in the form of a tracking arrow or a digital map.

Example 2: The same vehicle departs from the area covered by the digital map provided in the navigation device, but is not able to travel back on the same stretch of road due to an unfavourable one-way street regulation in this area. The driver then drives around the one-way street independently. As soon as the driver then arrives in an area through which he has already travelled from any direction, the navigation system uses the stored data to attempt to guide the driver back to the known route.

An example of a device which is suitable for carrying out the method in accordance with the invention will be explained hereinunder with reference to Figure 3.

The device comprises a navigation system having a locating unit COO, of which the recorded position data relating to the navigable object are matched with the data in a memory 100 for a digital map. This navigation system is extended by a module 300 for status identification. This module 300 which evaluates the data of the locating unit 200 and of the memory 100 distinguishes between the following object/vehicle statuses: - Onroad: The vehicle is located or is travelling on a digitised section of road.

- Off-road: The vehicle is not located or travelling on a digitised section of road and is also not on a previously recorded position track.

- On-track: The vehicle is located or is travelling on a recorded position track.

A position recording unit 400 for the purpose of recording and filtering position data ensures that on the one hand a position track is recorded and on the other hand not every position determined by the locating unit 200 is recorded, but is filtered according to predetermined criteria. The filtering criteria can be as follows: - Stationary phase: Recording interrupted, as the position values determined in this case do not differ or differ only slightly from those previously determined.

- Inaccuracy of position too great: Recording is not continued or is interrupted in this case.

A module 500 for the purpose of generating tracking instructions uses the module 300 to determine suitable tracking instructions which can be issued for a new journey on the position track 700. At a suitable moment, a module 600 for tracking "on-track"provides the tracking instructions, which are generated by the module 500, to a suitable output unit 800. A common bus 900 can be provided for the data exchange between the modules/units 300, 400, 500, 600, 700 and 800.

The digital map which is generated from the recorded position data can be illustrated in combination with the specified digital map, in order not to burden the vehicle driver unnecessarily with additional information or two different forms

of illustration. As an alternative to or in addition to the digital map, it is possible to generate and displays directional arrows using the recorded position data used for guidance purposes.

In an advantageous manner, the module 500 determines tracking references on the basis of a track already travelled on within an off-road area. This serves to improve both travel safety and comfort, as the driver is prepared in advance to react at the right time to any change on the stretch of road like a turn.

Tracking instructions, which reflect the actual geographic situation in the form of roads leading off from each other, do not refer to a turning prompt. On the contrary, a turning prompt is to be understood as a means for preparing the driver for the fact that the subsequent course of road or route requires the driver to consider a driving behaviour appropriate for a turning procedure.

The tracking system analyses the expected roads (route) and sets this in relation to the current vehicle speed. If the route data and the turning radii to be expected therefrom and the current object speed produce an angular speed which is greater than the maximum permissible speed determined for this object (vehicle), then a fuming-like action is expected which results in a corresponding display. The output/display of a corresponding tracking instruction prepares the driver to reduce speed in good time and thus to follow the course of the road (route) safely.

This is illustrated in Figure 4. If the vehicle 5 is travelling at a sufficiently slow speed on the previously recorded track 6, only straight directional arrows 7 flash on which by means of a corresponding orientation with respect to the north position indicate the course of the track 6 ahead. Therefore, the driver is assisted in deciding which way to go at a junction.

A prerequisite for the tracking system is that digitised information, i.e. route (road) data must be available to the tracking device or the module 300. For the off-road navigation function, it is possible for this digitised route data to have been recorded as described above when travelling in the off-road area and recording the associated geographic coordinates as an associated track. It is also possible to transmit this type of track from other systems, by means of a radio transmission from a central control station which has digitised data relating to this offroad area which data are unknown to the memory 100 dedicated to the vehicle.

The tracking method can also be applied to conventional navigation devices, wherein the user travels within the area specified by the route data. For this purpose, it is necessary to obtain the required track from the digital map of the memory 100 dedicated to the vehicle.

The minimum turning radius is then calculated from the observed track within a specific distance from the vehicle location in the direction of travel. One advantageous development of the method checks the plausibility of the turning

radii, in order not to interpret noise or measurement errors in the track incorrectly as a bend. One further advantageous development of the method is that the track is evaluated at a speed-dependent distance from the vehicle position. The current vehicle speed v and the turning radius r are then used to calculate the maximum expected angular speed by means of = v/r. If this speed exceeds the maximum permissible values andior the generally observed values and/or the manually input values provided for this vehicle and/or for the driver, the output unit 800 will output a corresponding turning prompt.

If the vehicle is travelling at a sufficiently slow speed, then the stretch of road a short distance in front is represented as being straight. In one advantageous embodiment, the current direction of travel corresponds to the upwards direction shown on the screen of the output unit 800. The deviation to be expected at a short distance is illustrated as a deflection of the arrow with respect to the upwards direction shown on the screen.

In the case of the exemplified embodiment illustrated in Figure 4, a vehicle having a tracking system in accordance with the invention turns off from a digitised area to a non-digitised woodland path and thus the vehicle status is off-road by definition. The onset of the off-road status means that the track of the vehicle is recorded as a chain of path point coordinates (position data). After arriving at an intermediate destination in the non-digitised area, the driver wishes to be guided

back by the tracking system in accordance with the invention.

The tracking system guides the driver via the directional indicators along the recorded track to the destination. At a fork in the path, the driver goes in the correct direction due to the fact that a tracking arrow constantly indicates the way.

Turning prompts are output if the driver approaches any bends too fast.

Claims

1. A method of guiding back a navigable object comprising: - using route data specified within an area for tracking purposes, - recording position data of the object at least when the object departs from the area specified by the route data, - recording the position data at least until a point of reference known from recording the position data is reached, and - guiding the object back from the known point of reference using the recorded position data.

2. A method as claimed in claim 1, wherein the object is guided back via generated directional arrows using the recorded position data.

3. A method as claimed in claim 2, wherein in order to generate the directional arrows the route data to be expected in the current proximity to the object is analysed and set in relation to the current speed of the object.

4. A method as claimed in claim 3, wherein it is determined whether the route data and the turning radii to be expected therefrom and the current speed of the object produce an angular speed which is greater than the maximum permissible speed determined for this object, and a turning-like action is subsequently

indicated in the form of a corresponding directional arrow.

5. A method as claimed in claim I or 2, wherein the object is guided back using a digital map which is generated from the recorded position data.

6. A method as claimed in claim 5, wherein the digital map generated from the recorded position data is illustrated in combination with a specified digital map.

7. A method as claimed in any of claims 1 to 6, wherein for guiding the object back on a different route, e.g. as a result of a one-way street regulation, an independent object control is undertaken, until a known point of reference is reached from which the object can be guided back using the recorded position data.

8. A method as claimed in any of claims 1 to 7, wherein the recording of the position data is interrupted if consecutively determined position data do not differ or differ only slightly from previously determined position data.

9. A method as claimed in any of claims I to 8, wherein the recording of position data is not continued or is interrupted if the position inaccuracies exceed a specified level.

10. A device for guiding back a navigable object comprising the following functional units: - a memory for a digital map, - a locating unit, - a position recording unit, - a module for identifying the status of an object, - a unit for producing a position track from the data of the position recording unit and from the data of the status identification, and - a tracking module.

1 1. A device as claimed in claim 10, wherein the position recording unit is allocated a filtering device, in order to interrupt the recording in accordance with predetermined criteria the stationary phase of the object or positional inaccuracy becomes excessive.

12. A device as claimed in claim 10 or 1 1, wherein a module is provided for generating tracking instructions on the basis of vehicle status data.

13. A device as claimed in claim 10, wherien the nodule for generating the tracking instructions is operatively connected to the position track, in order to output tracking instructions when the object moves once again on to the position track.

14. A device as claimed in any of claims lO to 13, wherein the tracking module is connected to an output unit, in order to output the instructions, which are generated by a/the module for generating tracking instructions, in particular in the fonn of directional arrows.

15. A method of guiding back a navigable object, substantially as hereinbefore described, with reference to the accompanying drawings.

16. A device for guiding back a navigable object, substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawings.