METHOD FOR MOVING A VEHICLE TO A COMPONENT OF AN OBJECT AT A DISTANCE THEREFROM (PRE-POSITIONING POINT)

Abstract

A method for moving a vehicle to a component of an object at a distance therefrom, the vehicle having a navigation module which has a camera and an evaluation electronics, and an identification element is attached to the object in a predetermined position in such a way that it is recognized by the camera in a far range (D.sub.max) of the vehicle from the object, and a reverse driving line of the vehicle is calculated by the evaluation electronics from the perspective position of the camera in relation to the identification element. The method improves the approach of a vehicle to a stationary object. A close-range (D.sub.min) is defined in the direction of the object by a close-range radius (R.sub.min) and the reverse driving line is calculated up to a virtual pre-positioning point (S.sub.Vi, S.sub.Vii, S.sub.Viii) lying on the close-range radius (R.sub.min).

Claims

1. A method for moving a vehicle to a component of an object at a distance therefrom, the vehicle having a navigation module which has a camera and an evaluation electronics, comprising the steps of: attaching an identification element is attached to the object in a predetermined position in such a way that it is recognized by the camera in a far range (D.sub.max) of the vehicle from the object, and calculating a reverse driving line of the vehicle by the evaluation electronics from the perspective position of the camera in relation to the identification element, wherein a close-range (D.sub.min) is defined in the direction of the object by a close-range radius (R.sub.min) and the reverse driving line is calculated up to a virtual pre-positioning point (S.sub.Vi, S.sub.Vii, S.sub.Viii) lying on the close-range radius (R.sub.min).

2. The method according to claim 1, wherein a target path is calculated from the pre-positioning point (S.sub.Vi, S.sub.Vii, S.sub.Viii) in the direction of the component of the object.

3. The method according to claim 1, wherein several reverse driving lines are always calculated with different mathematical functions and the vehicle follows one selected reverse driving line.

4. The method according to claim 3, wherein a respective pre-positioning point (S.sub.Vi, S.sub.Vii, S.sub.Viii) is calculated on the close-range radius (R.sub.min) for each of the plurality of reverse driving lines.

5. The method according to claim 4, wherein from each pre-positioning point (S.sub.Vi, S.sub.Vii, S.sub.Viii) always an associated target path is calculated in the direction of the component of the object.

6. The method according to claim 5, wherein from the plurality of reverse driving lines that one is determined as the selected reverse driving line at which an angle (φ.sub.i, φ.sub.ii, φ.sub.iii) between the target path and the vehicle longitudinal axis (x) of the trailer vehicle is as small as possible.

7. The method according to claim 1, wherein the reverse driving line has/have a tolerance corridor, in which an actual route of the vehicle is corrected.

8. The method according to claim 7, wherein when the tolerance corridor is left, new reverse driving lines are calculated from a new start position (S).

9. The method according to claim 1, wherein the identification element is read and verified in the far-range (D.sub.max).

10. The method according to claim 1, wherein the object is identified in the far-range (D.sub.max) by means of information stored on the identification element.

11. The method according to claim 1, wherein an approach area (D.sub.med) is provided between the far-range (D.sub.max) and the close-range (D.sub.min), wherein the approach area (D.sub.med) is delimited to the far-range (D.sub.max) by means of an approach area radius (R.sub.med) and to the close-range (D.sub.min) by the close-range radius (R.sub.min), the reverse driving line being calculated in the far-range (D.sub.max) and/or in the approach area (D.sub.med) using a mathematical function.

12. The method according to claim 1, wherein the close-range (D.sub.min) in the direction of the object, separated by a target area radius (R.sub.mic), follows a target area (D.sub.mic), wherein on the target area radius (R.sub.mic) a lifting point (S.sub.A) is defined, in which an air suspension of the vehicle is raised.

13. The method according to claim 12, wherein a coupling means of a trailer vehicle, in particular a kingpin, is detected by the camera in the target area (D.sub.mic).

14. The method according to claim 2, wherein several reverse driving lines are always calculated with different mathematical functions and the vehicle follows one selected reverse driving line, and wherein a respective pre-positioning point (S.sub.Vi, S.sub.Vii, S.sub.Viii) is calculated on the close-range radius (R.sub.min) for each of the plurality of reverse driving lines.

15. The method according to claim 14, wherein from each pre-positioning point (S.sub.Vi, S.sub.Vii, S.sub.Viii) always an associated target path is calculated in the direction of the component of the object, and wherein from the plurality of reverse driving lines that one is determined as the selected reverse driving line at which an angle (φ.sub.i, φ.sub.ii, φ.sub.iii) between the target path and the vehicle longitudinal axis (x) of the trailer vehicle is as small as possible.

16. The method according to claim 15, wherein the reverse driving lines have a tolerance corridor, in which an actual route of the vehicle is corrected, and wherein when the tolerance corridor is left, new reverse driving lines are calculated from a new start position (S).

17. The method according to claim 16, wherein the identification element is read and verified in the far-range (D.sub.max), and wherein the object is identified in the far-range (D.sub.max) by means of information stored on the identification element.

18. The method according to claim 17, wherein an approach area (D.sub.med) is provided between the far-range (D.sub.max) and the close-range (D.sub.min), wherein the approach area (D.sub.med) is delimited to the far-range (D.sub.max) by means of an approach area radius (R.sub.med) and to the close-range (D.sub.min) by the close-range radius (R.sub.min), the reverse driving line being calculated in the far-range (D.sub.max) and/or in the approach area (D.sub.med) using a mathematical function.

19. The method according to claim 18, wherein the close-range (D.sub.min) in the direction of the object, separated by a target area radius (R.sub.mic), follows a target area (D.sub.mic), wherein on the target area radius (R.sub.mic) a lifting point (S.sub.A) is defined, in which an air suspension of the vehicle is raised.

20. The method according to claim 19, wherein a coupling means of a trailer vehicle, in particular a kingpin, is detected by the camera in the target area (D.sub.mic).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] For better understanding, the invention is explained in more detail below with reference to 8 Figures, which show in

[0035] FIG. 1 is a perspective view of a towing vehicle and an object in form of a trailer before coupling;

[0036] FIG. 2 is a plan view of an identification element in the form of a sign with markers;

[0037] FIG. 3 is a perspective view of an object in form of a loading ramp;

[0038] FIG. 4 is a side view of a vehicle comprising a towing vehicle and a semi-trailer coupled thereto when approaching a loading ramp;

[0039] FIG. 5 is a perspective view of a towing vehicle with a navigation module attached to the towing vehicle coupling;

[0040] FIG. 6 is a plan view of a towing vehicle with three reverse driving lines to a semi-trailer;

[0041] FIG. 7 is a plan view of a towing vehicle with a reverse driving line running through different areas to a semi-trailer; and

[0042] FIG. 8 is a flowchart of method steps according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0043] FIG. 1 shows a perspective view of a vehicle 10 in the form of a towing vehicle 15, which is being driven backwards towards a component 21 of an object 20 in the form of a trailer vehicle 22 at a distance from the towing vehicle 15 in order to pick up the trailer vehicle 22 and mechanically couple it to one another.

[0044] In the coupled state, the towing vehicle 15 and the trailer vehicle 22 form an articulated tractor-trailer assembly. For a detachable connection to the trailer vehicle 22, the towing vehicle 15 has a towing vehicle coupling 16, into which a coupling means 23 of the trailer vehicle 22 can be inserted and locked. The towing vehicle coupling 16 can be seen particularly well in FIG. 5 and comprises a coupling plate 17 which is fastened to the towing vehicle 15 by means of two bearing blocks 18 mounted laterally thereon. The bearing blocks 18 stand on a mounting plate 19, which in turn rests on two beams of a vehicle frame not further identified and being permanently connected to them.

[0045] The coupling means 23 of the trailer vehicle 22 is usually a king pin that projects downwards forming the component 21 of the object 20 and is shown enlarged in FIG. 1 for a better understanding. For a smooth and damage-free coupling, the towing vehicle 15 must be reversed as precisely as possible towards the stationary trailer vehicle 22.

[0046] For an autonomous or semi-autonomous approach of the towing vehicle 15 to the trailer vehicle 22, the towing vehicle 15 has a navigation module 11 which includes at least one camera 12 and evaluation electronics 13. It is preferred to attach the navigation module 11 to components of the towing vehicle coupling 16, in particular to the coupling plate 17, one of the bearing blocks 18 and/or the mounting plate 19. In any case, a detectable field of view of the camera 12 is in a vehicle longitudinal axis x of the vehicle 10 to the rear, directed towards the object 20.

[0047] An identification element in the form of a sign 30 is fixed in place on the object 20 and is located on a front side 24 of the trailer vehicle 22 in FIG. 1. The sign 30 can, but does not have to, be aligned centrally in a vehicle longitudinal axis x of the trailer vehicle 22. However, it is preferable to attach the sign 30 in a mounting radius R.sub.S around the vehicle longitudinal axis x corresponding to half the width T.sub.B (see FIG. 7) of the trailer vehicle 22 so that the camera 12 can accurately find and read it.

[0048] The sign 30 has a number of markers 31, which can be seen in FIG. 2 by way of example. Each marker 31 is designed as a square field with a high-contrast, dark filling on the surface of the sign 30. Markers 31 are used to calculate in the evaluation electronics 13 on the towing vehicle 15 at least one reverse driving line 40.sub.i, 40.sub.ii, 40.sub.iii, as shown in FIG. 6 based on a perspective change in the relative position of the camera 12 and the sign 30. The further the camera 12 migrates laterally to the sign 30 as the vehicle 10 approaches, the greater the distortion of the markers 31. The position of the vehicle 10 relative to the sign 30 is calculated from the distortion of the markers 31. The sign 30 is always searched for in the entire field of view of the camera 12.

[0049] The corners of an outer marker 32, which forms a closed outer border, are used in particular for an accurate calculation of the reverse driving line 40.sub.i, 40.sub.ii, 40.sub.iii. Additional inner markers 33 enable the navigation module 11 to recognize whether the vehicle 10 is approaching the object 20 from the front or rear, since there are no markers 31, in particular no inner markers 33, on the back of a sign 30 that is sometimes free-standing. The inner markers 33 are arranged offset to an outer contour of the outer marker 32 inwards by the amount of their size. Individual inner markers 33 border on free spaces 34 which have the same size as the inner markers 33. In principle, all markers 31 are applied to a single sign 30.

[0050] In addition, a three-dimensional position information of the component 21, in the embodiment of FIG. 1 of the king pin 23, relative to the sign 30 is stored in the markers 31, in particular in the inner markers 33. A three-dimensional position information is understood to mean the distance of sign 30 from component 21, for example king pin 23, in vehicle longitudinal axis x, in a vehicle transverse axis y, and in a vehicle vertical axis z.

[0051] The navigation module 11 reads the three-dimensional position information and mathematically modifies the coordinates of the mounting position of the sign 30 according to an offset, so that the vehicle 10 hits the component 21 of the object 20 instead of the sign 30. It is essential that the sign 30 is always fixed in place on the object 20 according to the three-dimensional position information about the component 21 stored thereon and does not change its own position.

[0052] The markers 31, in particular the inner markers 33, also contain information about the identity of the object 20, which is also read out by the navigation module 11. In this way, for example, the vehicle 10 receives information as to what type of trailer vehicle 22 the trailer vehicle 22 to be coupled is. The type of trailer vehicle 22 is understood to mean, for example, whether it is a refrigerated, silo or tank trailer. Such trailer vehicles 22 often have an interfering contour that must be taken into account when the vehicle 10 approaches. The information contained in markers 31 relates, among other things, to geometric or technical data on the nature of object 20, which is taken into account when calculating reverse driving lines 40i, 40.sub.ii, 40.sub.iii (see FIG. 6, FIG. 7) in order to enable an accident-free approach.

[0053] In addition to the markers 31, the sign 30 also has a coding field 35 in which, in particular, a QR code is applied. Provision can also be made for an identification number of the trailer vehicle 22 to be implemented in the sign 30 which is read out by the camera 12, expediently in the coding field 35 or alternatively also in the markers 31, in particular the inside markers 33. Logistic information relating to the object 20 or trailer vehicle 22 can be linked to the sign 30 via the identification number, so that the object 20 or trailer vehicle 22 is identified as the one being sought when the towing vehicle 15 approaches. In principle, the coding field 35 contains information that is primarily important for the logistical and less important for the navigational evaluation.

[0054] A lifting point S.sub.A for the towing vehicle 15 can also be defined in the markers 31, in particular the inner markers 33, or with the help of an identification number of the trailer vehicle 22 implemented on the coding field 35, wherein at the lifting point S.sub.A an air suspension 14 (see FIG. 5) of the towing vehicle 15 is raised at least until the coupling plate 17 comes into contact with the semi-trailer 22.

[0055] FIG. 3 shows an alternative exemplary embodiment of the invention, in which the object 20 is a loading ramp 25, the middle position of an upper edge 26 of which represents the component 21 to navigate to. At a predetermined position of the loading ramp 25 a sign 30 is fixed in place, in which the three-dimensional position information of the middle position upper edge 26 of the loading ramp 25 relative to the sign 30 is stored. A vehicle 10 consisting, for example, of a towing vehicle 15 and a semi-trailer 22 coupled to it, as shown in FIG. 4, moves in the direction of sign 30, corrected by the three-dimensional position information of the middle position upper edge 26 of loading ramp 25, and hits the component 21 to be controlled backwards in the middle.

[0056] In this exemplary embodiment, the camera 12 of the navigation module 11 or an additional camera 12a connected to the navigation module 11 should be arranged on a rear side 27 of the trailer vehicle 22 in order to ensure a clear field of view of the sign 30.

[0057] FIG. 6 shows the approach of a vehicle 10 in the form of a towing vehicle 15 to a parked trailer vehicle 22 in a plan view. The towing vehicle 15 is in the starting position S. The sign 30 of the trailer vehicle 22 has already been captured by the camera 12 of the navigation module 11 arranged on the towing vehicle 15, read out and a total of three reverse driving lines 40.sub.i, 40.sub.ii, 40.sub.iii have been calculated on the basis of different mathematical functions.

[0058] For reasons of clarification, only the middle reverse driving line 40.sub.ii of the three reverse driving lines 40.sub.i, 40.sub.ii, 40.sub.iii, which has already been identified as the selected reverse driving line 40a by the navigation module 11, is provided with a tolerance corridor 41. A tolerance corridor 41 is understood as an kinematic envelope around one or more reverse driving lines 40.sub.i, 40.sub.ii, 40.sub.iii, within which the towing vehicle 15 can still countersteer in the event of deviations from the selected reverse driving line 40a in order to return to the originally selected reverse driving line 40a. If it is determined in the navigation module 11 that a current position of the towing vehicle 15 is outside of the tolerance corridor 41, steering back is no longer possible. Instead, the current position is interpreted as the new starting position S, from which a new set of curves of reverse driving lines 40.sub.i, 40.sub.ii, 40.sub.iii is calculated again in the navigation module 11. The newly calculated reverse driving lines 40.sub.i, 40.sub.ii, 40.sub.iii are preferably also each provided with a tolerance corridor 41.

[0059] In all of the exemplary embodiments, the reverse driving line(s) 40.sub.i, 40.sub.ii, 40.sub.iii calculated by the navigation module 11 always ends in an associated pre-positioning point S.sub.Vi, S.sub.Vii, S.sub.Viii in front of the trailer vehicle 22. When one of the pre-positioning points S.sub.Vi, S.sub.Vii, S.sub.Viii is reached, the towing vehicle 15 exclusively drives straight backwards. The reverse driving lines 40.sub.i, 40.sub.ii, 40.sub.iii are therefore no longer continuously calculated after the pre-positioning point S.sub.Vi, S.sub.Vii, S.sub.Viii has been passed. Each of the pre-positioning points S.sub.Vi, S.sub.Vii, S.sub.Viii lies on a close-range radius R.sub.min, whose distance from the object 20 is predetermined by the field of view of the camera 12, 12a. As the towing vehicle 15 approaches a camera 12 arranged in the vicinity of the towing vehicle coupling 16 moves under the front side 24 of the trailer vehicle 22 with the sign 30 attached to it, so that from the pre-positioning point S.sub.Vi, S.sub.Vii, S.sub.Viii the sign 30 is no longer located in the field of vision of the camera 12. From the pre-positioning point S.sub.vi, S.sub.Vii, S.sub.Viii onwards, the towing vehicle 15 is no longer in a controlled approach along a selected reverse driving line 40a, but in a controlled straight-ahead travel on one of the associated target paths 43.sub.i, 43.sub.ii, 43.sub.iii in a linear direction the component 21 of the object 20.

[0060] The reverse driving line 40i running on the left in the image plane of FIG. 6 ends on the close-range radius R.sub.min in the associated pre-positioning point S.sub.Vi. The straight target path 43.sub.i running from here in the direction of the coupling means 23 spans an angle φ.sub.i with respect to the vehicle longitudinal axis x of the trailer vehicle 22. The reverse driving line 40.sub.iii running on the right in the image plane also ends on the close-range radius R.sub.min in the pre-positioning point S.sub.Viii. The straight target path 43.sub.iii running from the pre-positioning point S.sub.Viii in the direction of the coupling means 23 spans an angle φ.sub.iii to the vehicle longitudinal axis x of the trailer vehicle 22.

[0061] The middle reverse driving line 40.sub.ii ends on the close-range radius R.sub.min in the pre-positioning point S.sub.Vii, in the middle in front of the trailer vehicle 22. The straight target path 43.sub.ii runs from the pre-positioning point S.sub.Vii to the coupling means 23 and is ideally aligned with the vehicle longitudinal axis x of the trailer vehicle 22. The angle is in this case 0°. From the calculated reverse driving lines 40.sub.i, 40.sub.ii, 40.sub.iii, the navigation module 11 identifies as the selected reverse driving line 40a this one which has an angle φ.sub.i, φ.sub.ii, φ.sub.iii with the lowest value.

[0062] Typically, a vehicle 10 is moved in the direction of an object 20 on a route 42 running through four different areas, which is shown graphically in FIG. 7 and explained as a flow chart in FIG. 8. To simplify the representation, only one of several possible reverse driving lines 40.sub.i, 40.sub.ii, 40.sub.iii is shown in FIG. 7, namely the reverse driving line 40.sub.ii already identified as favorable in FIG. 6.

[0063] In a far-range D.sub.max, the vehicle 10 driving in the forward direction, for example a towing vehicle 15, approaches a semi-trailer 22 to be coupled. The semi-trailer 22 has a predetermined length T.sub.L and width T.sub.B.

[0064] The far-range D.sub.max is delimited outwards in the radial direction towards the object 20 by a far-range radius R.sub.max and in the direction of the object 20 by an approach area radius R.sub.med. Outside the far-range radius R.sub.max, the vehicle 10 moves in its usual driving environment without relevance for a method and a system for approaching the vehicle 10 to a stationary object 20. The far-range radius R.sub.max has, starting from the lifting point S.sub.A, a length of 12.00 m to 17.00 m, preferably 13.00 m to 16.00 m, very preferably 14.00 m to 15.00 m, and covers an angle of 100° to 120° in the straightforward direction of the object 20.

[0065] Within the far-range D.sub.max, the method or system for moving a vehicle 10 to an object 20 is triggered when the approach point system start A.sub.S is reached. The system start can be triggered manually by the driver, by means of a remote control from a control station, or by predetermined programming.

[0066] While the vehicle 10 is still driving forward, it reaches an approach point for establishing a link connection A.sub.V, from which point the camera 12 is switched on and a sign 30 on an object 20 is searched for. If the link connection at the approach point A.sub.V is successful, an identification number of the object 20, in particular of the trailer vehicle 22, is subsequently read out in an object information approach point A.sub.O. Consequently, the navigation module 11 knows the type of trailer vehicle 22 and sometimes also its geometric dimensions. The forward travel of the vehicle 10 on the route 42 ends in the starting position S. The speed of the vehicle 10 is less than 50 km/h in the far-range D.sub.max.

[0067] Starting from the start position S located in the far-range D.sub.max, at least one reverse driving line 40.sub.i, 40.sub.ii, 40.sub.iii is generated by means of the navigation module 11, wherein the respective line is identified in FIG. 7 as the selected reverse driving line 40a. The reverse driving line 40.sub.ii is calculated based on the perspective alignment of the camera 12 to the markers 31 applied to the sign 30 and corrected by the three-dimensional position information of the component 21 of the object 20, the position information also being stored in the markers 31 of the sign 30. If necessary, the navigation module 11 also determines an associated tolerance corridor 41 for one or more reverse driving lines 40.sub.i, 40.sub.ii, 40.sub.iii.

[0068] After passing the approach area radius R.sub.med, the vehicle 10 has changed to the approach area D.sub.med. Starting from the lifting point S.sub.A, the approach area radius R.sub.med has a length of 6.00 m to 10.00 m, preferably 7.00 m to 9.00 m, and covers an angle of 130° to 140° in the straight forward direction of the object 20. While driving through the approach area D.sub.med, the already generated reverse driving line 40ii, 40a is traveled along and the three-dimensional position information is read from the sign 30 and the position of the sign 30 relative to the camera 12 is tracked. The speed of the vehicle 10 is reduced in the approach area Dined with respect to the far-range D.sub.max and can be a maximum of 20 km/h, for example.

[0069] The approach area D.sub.med transitions into a close-range D.sub.min when the close-range radius R.sub.min is reached. The close-range radius R.sub.min has a length of 3.00 m to 4.00 m, preferably 3.30 m to 3.70 m, starting from a target position S.sub.Z that corresponds to the component 21, and covers an angle up to 140° in the straight forward direction of the object 20. The speed of the vehicle 10 is reduced even further in the close-range D.sub.min with respect to the approach area D.sub.med and can be a maximum of 5 km/h, for example.

[0070] Upon reaching the close-range radius R.sub.min, the vehicle 10 is located in the pre-positioning point S.sub.Vii, which is located immediately in front of the component 21 of the object 20 in the forward direction. From the pre-positioning point S.sub.Vii onwards, the sign 30 attached to the front side 24 of the object 20 is no longer captured by the field of view of the camera 12 and therefore is no longer usable for capturing the relative position of vehicle 10 to the object 20, since the rear of the towing vehicle 15 has already driven under the trailer vehicle 22. However, the towing vehicle 15 and trailer vehicle 22 are aligned with one another in the vehicle longitudinal axis x, so that the towing vehicle 15 only needs to reverse in order to hit the coupling means 23 of the trailer vehicle 22.

The close-range D.sub.min transitions into the target area D.sub.mic when a target area radius Rem is reached. Starting from the target position S.sub.Z that matches the component 21, the target area radius R.sub.mic has a length corresponding to half of the width of the object 20, in the present example half of the width T.sub.B of the trailer vehicle 22 of 2.55 m, for example, and covers an angle in the straight forward direction of the object 20 of up to 180°. The lifting point S.sub.A, at which the rear of the towing vehicle 15 together with the towing vehicle coupling 16 is lifted by the air suspension 14, lies on the target area radius R.sub.mic in the longitudinal axis x of the vehicle. From the lifting point S.sub.A, the towing vehicle coupling 16 is in sliding contact with the trailer vehicle 22 until it reaches the target position S.sub.Z, in which the kingpin 23 has entered the towing vehicle coupling 16. The speed of the vehicle 10 is reduced even further in the target area D.sub.mic with respect to the close-range D.sub.min and can be a maximum of 2.5 km/h, for example.

LIST OF REFERENCE NUMBERS

[0071] 10 vehicle [0072] 11 navigation module [0073] 12 camera [0074] 12a additional camera trailer vehicle [0075] 13 evaluation electronics [0076] 14 air suspension [0077] 15 towing vehicle [0078] 16 towing vehicle coupling [0079] 17 coupling plate [0080] 18 bearing block [0081] 19 mounting plate [0082] 20 object [0083] 21 component [0084] 22 trailer vehicle, semi-trailer [0085] 23 coupling means, king pin [0086] 24 front side trailer vehicle [0087] 25 loading ramp [0088] 26 middle position upper edge loading ramp [0089] 27 rear of trailer vehicle [0090] 30 identification element/sign [0091] 31 markers [0092] 32 outer markers [0093] 33 inner markers [0094] 34 free space [0095] 35 coding field [0096] 40.sub.i-iii reverse driving lines [0097] 40a selected reverse driving line [0098] 41 tolerance corridor [0099] 42 route vehicle [0100] 43.sub.i-iii target path/target straight(s) [0101] A.sub.O approach point object information [0102] A.sub.S approach point system start [0103] A.sub.V approach point link connection [0104] D.sub.max far-range [0105] D.sub.med approach area [0106] D.sub.min close-range [0107] D.sub.mic target area [0108] R.sub.max far-range radius [0109] R.sub.med approach area radius [0110] R.sub.min close-range radius [0111] R.sub.mic target area radius [0112] R.sub.S mounting radius sign [0113] S start position [0114] S.sub.Vi-Viii pre-positioning points [0115] S.sub.A lifting point [0116] S.sub.Z target position [0117] T.sub.B width trailer vehicle/semi-trailer [0118] T.sub.L length trailer/semi-trailer [0119] x vehicle longitudinal axis [0120] y vehicle transverse axis [0121] z vehicle vertical axis [0122] φ.sub.i-iii angle of target path or line/vehicle longitudinal axis