DE3238186C2 - - Google Patents

Description

The invention relates to a dead reckoning system to determine the target position of a vehicle, according to the preamble of the first claim.

From DE-OS 29 38 373 a method for determining errors of a sensor, with which signal is generated in accordance with the distance traveled or the speed of a vehicle, is known. In this method, the respective vehicle position is determined by means of a navigation system, in particular from the signals from the sensor and a direction indicator in a computer via a coupling calculation. In addition to the first coupling calculation, with which a position P ₂ deviating from the actually reached position P ₂ is determined, at least one further coupling calculation is carried out with a predetermined speed or acceleration-dependent pseudo error and a correspondingly falsified position P ₃ is determined.

With this method, the above-mentioned coupling calculations have to be done with little carried out at least two routes between known positions will. From the coordinates of the named positions the speed or acceleration-dependent errors of the sensor certainly.

Furthermore, a method is known from DE-OS 28 05 628, at which with a dead reckoning calculation from the Direction signals of a course gyro and the path signals a position sensor calculates the position of a vehicle becomes. However, this position is due to the unknown Drift of the course gyro falsified. Furthermore, in an additional coupling calculation one with a certain predetermined drift or pseudo drift determined tool position.

To determine the unknown drift of the course gyro and thus in the further determination of the actual position of the vehicle as accurately as possible determine it is necessary to have a known position approach and from the ratio of the distances of the requested showed positions and the actual position of the Vehicle and the directional angles of these positions  North to carry out the correction calculation.

This procedure is also only possible if Knowledge of the location and in particular the coordinates of certain reference points are available.

In unknown terrain or, for example, bad ones Visibility, the finding of a reference point can prevent a drift determination and thus a bottom position correction can not be carried out.

The object of the invention is a dead reckoning system to specify the exact position at which who needs no knowledge of the area used the.

This task is accomplished by the features of the first patent characteristics specified resolved.

The north direction can, for example, from the signals a so-called north-seeking gyroscope, as in the be used in navigation systems, won will. The north accuracy achieved with this is a essential feature of this gyroscope and allows a very precise navigation of the vehicle. For purposes at those with low accuracy can go to the north direction determination an earth field probe who applied the. This is often used in conjunction with an odometer for determining the position of road vehicles, such as B.  Ambulance applied.

Since the signal z. B. the Erdfeldmeßsonde not constantly for Ver stands, but is temporarily affected by interference fields is flowing, a steering angle sensor is provided, which wäh delivers a direction signal during the disturbance time. This However, the direction signal is like a course gyro with a drift. Especially when cornering there is a significant drift error that affects the positions ad distorted. This drift is in a shape tion of the invention according to the relationship

determined.

Here isa _N the difference measured after the fault angle between the beginning and the end of the measurement determined north direction angle of the vehicle, wherein course a change of course of the vehicle not in the sem angle is included. This angle is divided by the distance covered during the measurementS _N.

When determining the drift of a course gyro, it is called a divi factor between the last two measurements gene used because the drift of the course gyro a radio tion of time and regardless of the distance traveled.  

In the dead reckoning system according to the invention, the course direction of the course reference device is determined by determining the north direction at the beginning and at the end of the route. The coordinate values E _s , N _{s of} the actual position P _s are according to the relationships

certainly. Place hereE _J,N _J by driftD _N the course reference obtained coordinate values andE _P,N _P by the pseudo driftD _P obtained coordinate values. The unknown driftD _N becomes doing the differenceα _N the orientation of the course reference device determined at the beginning and at the end of the distance traveled.  

In the dead reckoning system according to the invention, the position is determined essentially for smaller differences suitable angle or drift. Larger deviations are due to the high accuracy requirements not common on navigation systems. It is sufficient known from the rotation of the earth and geographical Wide dependent proportion of the drift of a course gyro with simple means to compensate. This makes it single interesting, the redefinable parts of the drift determine and thereby improve the position display. However, this can also be done with this dead reckoning system Compensate entire gyro drift.

The invention is explained in more detail below with reference to the drawing. It is initially assumed that the vehicle is initially at a known position P _O and that the heading angle of the vehicle is known. The coordinates N _O , E _{O of} this position and the course angle δ are entered in a known manner in the navigation computer. If the vehicle now begins its journey through the area, the coupling calculation is carried out in the usual way, by means of which the distances covered and course changes are continuously evaluated and the coordinates of the respective location are determined, albeit falsified by a drift error. The respective location can be displayed on a map device, for example.

The distanceA between the pointsP _O-P _S represents the deed neutrally driving distance of the vehicle. For simpler A straight route was chosen, self-ver Of course, any route is possible Lich. The location display in a map device describes however the routeB between the pointsP _O-P _J, thereby the unknown drift of the course gyro the displayed course experiences a directional deviation. This deviation will integrated over time and requires in certain ab stands  a correction of the displayed position coordinates. To in addition to calculating the vehicle position from the drift-prone course display of the course gyro is constant dig determines another vehicle position, which of the routeC. between the pointsP _O-P _P corresponds. These You get a route by calculating a course with a so-called pseudo drift, which turns into an unknown gyroscope drift added up. After a driving timeT / _N t_Nthat any can be selected or automatically based on different Criteria is determined, and according to which the vehicle the pointP _S the course angle is new averages. This happens with a north search using a gyrocompass or an earth field probe. The course angle determined here corresponds in the off guidance example through the straight routeA the Starting course angle. The location or position display however shows a positionP _J at by the spinning top drift is falsified and a heading angleδ +α _N including tet.

A third location display P _P is obtained from the calculation of the position using a pseudo drift. The unknown drift D _{N of} the course gyroscope is now calculated according to the relationship

certainly.

The coordinate values for the actual You get the location of the vehicle as follows:  

after reshaping, the east value of the coordinate value sought results in

the north value is calculated in the same way

The behavior of the drifts can of course also be under Use of formula (1) as a ratio of the drift angles α _N,α _P represent the angleα _N according to the relation hung

a _N =α _F -δ

and the angleα _P after the relationship

α _P =α _FP -α _F

is to be determined. Here isa _F the angle that as driving tool direction is displayed in relation to the north direction andα _FP the angle between the north direction and the vehicle direction falsified by the pseudo drift. The angleδ is the heading angle, d. that is, the actual win between vehicle direction and north direction. By one set the angular relationships in equations (3) and (4) the coordinate valuesE _S,N _S according to the relationships gene

determine.  

These values are used to correct the displayed values or the position display on the map device. For the further travel distance, the drift D _N determined here can now be used to determine the position, a new position correction being carried out after a further travel time using the same procedure. With the dead reckoning system according to the invention, it is thus possible to monitor the drift behavior of the heading gyro and to constantly improve the position display.

Claims (6)

1. dead reckoning system for determining the actual position P _{S of} a vehicle after covering any route, in which a dead reckoning with an unknown drift D _N caused by a course reference and at least one further arbitrarily chosen pseudo drift D _{P is} carried out and in which the distances the position thus obtained (P _J , P _P ) are evaluated, the north direction being determined in order to determine the course direction of the course reference device, characterized in that the course direction of the course reference device is determined by determining the north direction at the beginning and at the end of the route that the Coordinate values of the actual position E _S , N _S according to the relationships E _S = E _J - (E _P - E _J ) · D _N / D _P
N _S = N _J - (N _P - N _J) · D _N / D _P are formed, E _J, N _J by the drift D _N of the course reference device obtained coordinate values and E _P, N _P by the pseudo drift _Dp represent the coordinate values obtained, the unknown drift D _{N being determined} from the difference α _{N in} the alignments of the course reference device at the beginning and at the end of the distance traveled (course angle error). 2. dead reckoning system according to claim 1, characterized in that the drift D _N according to the relationship is determined, where t _{N is} the travel time for covering the route. 3. dead reckoning system according to claim 1, characterized in that the drift D _N according to the relationship is determined, where S _{K is} the length of the route. 4. dead reckoning system according to claim 1, characterized in that the ratio of the drifts D _N / D _P from the determined directional angles according to the relationship is formed, where a _{F represents} the angle between the displayed vehicle direction and the north direction at the end of the route, δ the actual angle between the vehicle direction and north direction at the beginning of the route and α _FP the angle between the vehicle direction falsified by the pseudo script and the north direction at the end of the route . 5. dead reckoning system according to one of the preceding claims, characterized in that the north direction by means of a gyrocompass is determined. 6. dead reckoning system according to one of claims 1 to 5, characterized characterized that the north direction by means of an earth field probe is determined.