EP1118713B1 - Method for steering a construction machine or roadpaver and road finisher - Google Patents

Abstract

The method involves determining the actual position of a measurement point on a drive unit or working device in a geodetic position measurement system, deriving the actual position of the working device or an element indicative of the marked route, comparing this with a desired position to generate correction signals and actuating control elements to bring the actual position to the desired position. Independent claims are also included for the following: a road making machine.

Description

The invention relates to a method according to the preamble of patent claim 1 and a paver according to claim 12.

Construction machines affected here include road pavers, graders, Crawlers, slipform pavers and traffic area recycling machines where the working device works the subsoil to a planned route to shape, with the driving unit acting as a carrier of the working device, the necessary Applying propulsive force and taking the direction and an adjustment the longitudinal and / or cross slope and / or working width of the working device is possible on the drive unit.

With a paver, the screed has the material evenly over the Spread, compact and smooth the width. Using a sensor The screed is leveled with the control system Setpoint values adjusted in height and / or bank angle. When using a extending screed the working width can also be adjusted. Usually will guide wires representing the desired height and course (EP-B-542 297) stretched along the planned route, which are scanned by sensors, to get information about leveling the screed. The high effort for adjusting the guide wires is disadvantageous. So far, the others have been similar Construction machines of the group mentioned above controlled. Some construction machines are automatically steered, with a guide wire providing directional information. at Automatic steering is not absolutely necessary for grades and caterpillars; however the working device is still along the planned route Taxes.

In a method known from DE-B-11 51 531, the paver is made of Hand directed. The screed is leveled using two guide wires without guide wires stationary telescopes for observing height marks on the screed and via control devices on the telescopes, which the adjustment devices control the screed.

The following procedures are also used in practice:

With a geodetic device like a total station or a GPS system, a Measuring point recorded on the driving unit. Taking into account further measured variables, Like machine longitudinal and cross slope, a machine model is created with which the position of the construction machine is defined in a digital terrain model. The actual data can be compared with target data from the planning. Position deviations determined in the process are used to control control elements. With slip shift ready e.g. the steering cylinders and the lifting cylinders of the height adjustment of the support frame controlled. Automatic guidance of the construction machine in the field and leveling of the working device still need a guide wire or a similar reference element for deriving directional information and therefore a considerable measurement effort. specially In the case of construction machinery traveling on caterpillars, precise steering is difficult and steering errors can affect the accuracy of the settings of the working device significantly affect if primarily the driving unit and secondarily the processing device of the driving unit is tracked.

In the self-propelled control method known from US-A-5 549 412 Construction machines are made using a geodetic positioning system from a comparison of the derived actual work position and a planned one Target work position position deviations determined and from the position deviations Generated correction signals for the control elements of the working device, to actuate the control elements on the basis of the correction signals, to the actual working position to bring to the target working position and the working device in the to run the planned route. However, the driving unit of the construction machine controlled by hand.

The invention has for its object a method of the type mentioned to create with the working device a construction machine without guide wires or Earth-based reference elements with high working accuracy automatically in one the planned route is mobile, and an automatically precisely controllable one Specify paver.

The task is with the features of claim 1 and the sibling Claim 12 solved.

Using the geodetic positioning system, the working device is first of the construction machine exactly in the planned route. stringlines or earthbound Reference elements are not required. Nevertheless, the planned The route was created very precisely because the work fixture was used with the positioning system led transversely to the direction of travel and in their height and inclination is, and the driving unit only in the second line of the working device can be. Thereby the knowledge is taken into account that it is for high work accuracy it is important to control the work equipment primarily, and only secondarily the driving unit, since steering movements of the driving unit and made via the driving unit Adjustments of the working device would be too imprecise. Independently of, whether the measuring point is on the driving unit or on the working device is, the position of the working device is determined via the measuring point determined and are used in the control in addition to the position information of the measuring point additional information relevant to the location of the working device, for example via sensors, procured and used for control. The is used for the automatic steering of the driving unit guided working device for reference.

Automatic width control is advisable the screed using the planned data of obstacles, for example Gullies or the like, the control elements of the screed for driving around of the obstacle. It is possible to overcome an obstacle with either Bypass working width, or the working width in the area of the obstacle to reduce or enlarge only on one side. The automatic width control has no influence on the automatic control of the screed along the planned route. With the automatic width control, one-sided or double-sided parking or alternative bays or constrictions shape, the automatic width control of the guide of the Screed is superimposed along the planned route. Arranged on the paver Sensors detect oncoming obstacles, such as gullies, and control the control elements of the extendable screed to close the obstacles bypassed.

The paver is to perform a fully automatic Control along the planned route with the help of a geodetic positioning system designed. Regardless of where the measurement point is supporting mast (on the drive unit or on the working device), is always the real or virtual reference point on the screed or at one for the planned one The route determines the relevant element and this reference point controlled that the screed forms the planned route. By deriving of direction vectors using the measuring point and the respective reference point the driving unit can also be steered automatically. That for the design element is a lower outer edge, for example the screed or the rear end point of this lower outer edge, the should be routed along the planned outline of the route. Largely The working width is independent of the driving movement of the driving unit Control elements of the screed parts in the transverse direction in the planned route adjustable, and the transverse and longitudinal inclinations of the screed are remotely controlled adjustable.

The mast carrying the measuring point is on a spar of the screed appropriate. The actual working position is controlled with additional information determined, for example, representing strokes of the control elements Signals and / or calculated direction vectors.

There will be relative or automatic steering of the driving unit absolute deviations from a measured reference direction measured, and, if they exceed a tolerance range, for automatic Steering used.

Alternatively or in addition, additionally calculated or derived from a digital terrain model or from a compass, a Direction sensor or a GPS-based system measured direction information be taken into account in the automatic steering. But that's always the case precise guidance of the working device in the foreground and becomes the driving unit of the Work device tracked. This can result in inaccurate steering movements not on the positioning of the working device in the planned route impact or simply be compensated.

It becomes the abundance of the total data acquired for the control processed with at least one system computer, the stationary or in the construction machine itself can be provided.

According to the method, special direction vectors are determined, from which correction signals for automatic steering of the driving unit.

For a paver with a screed with a constant working width, which can be moved back and forth in a linear transverse guide are used in the automatic Guiding the screed along the planned route also adjusted the longitudinal and / or transverse slope of the screed. The measurement point is expediently arranged on the screed to always keep the location, for example to know a lower outer plank edge. The measuring point can also be at the Driving unit or be arranged on a spar of the screed, then using Known machine-specific information or information derived from sensors from the measuring point the position of the screed or the outer one Edge of the screed calculated.

In the case of a paver with a pull-in screed, the derived one is used Correction signals controlled the width adjustment device to initially a screed part to run exactly in the planned route. The other screed part is either adjusted in exactly the opposite direction to a screed section, in order to achieve a constant working width, or is even adjusted individually, to achieve a working width that varies according to plan. The Longitudinal and / or transverse inclination of the screed in accordance with the planned specifications adjusted to keep the extending screed exactly in the planned route to drive. The measuring point can either be on the screed, expediently even on a screed section, on the drive unit or on a spar of the screed be arranged.

In any case, it can be useful for a road paver for the actual working position relevant reference point to the lower outer edge of the screed or even put the rearmost end of this lower outer edge because of this created an outer edge of the route or ceiling layer.

In the above-described process variants and embodiments only one geodetic positioning system was assumed, the used to control the working device and the driving unit becomes. However, it would be conceivable to add two geodetic positioning systems use, for example, to separate the working device and the driving unit Taxes. However, this solution would be very complex.

The method according to the invention can be used with a grader in order to the rotatability of the graders in the planned route drive. The line of motion of the other end of the group of degrees is by calculation known at any time. For a caterpillar with a pushed or pulled Dozer blade can be guided exactly in the planned route. In the case of a slipform paver, the slipform and / or the screed guided in the planned route. It can be changed or unchangeable Working width. The same applies to a traffic area recycling device its working device guided in the planned route. Here too, you can work with a fixed or variable working width.

A geodetic position determination system is used for a route section Stationary total station installed near the planned route, i.e. a kind of theodolite with appropriate equipment and actuators, if necessary combined with the process computer or one with the process computer linked calculator. As an alternative you can use a stationary or moving GPS system are used, using a DGPS system to increase accuracy recommends working with a stationary reference station in order to get the procured Precise or calibrate position data. The data transfer or the transmission of measurements and correction signals can be wireless, e.g. through radio or laser transmission, or via one or more cable harnesses.

Fig. 1

einen Funktionsplan des erfindungsgemäßen Verfahrens bei einer Baumaschine in Form eines Straßenfertigers mit einer Einbaubohle konstanter Arbeitsbreite,

Fig. 2

eine schaubildartige Maschinenkonfiguration des Straßenfertiges zum Funktionsplan der Fig. 1,

Fig. 3

einen Funktionsplan zur Durchführung des Verfahrens bei einer als Straßenfertiger mit einer Ausziehbohle ausgebildeten Baumaschine,

Fig. 4

eine Maschinenkonfiguration zum Straßenfertiger passend zum Funktionsplan der Fig. 3,

Fig. 5

eine Maschinenkonfiguration als Beispiel einer Baumaschine mit an der Fahreinheit angebrachtem Messpunkt, nämlich einem Straßenfertiger mit einer Ausziehbohle,

Fig. 6

eine schematische Draufsicht auf einen Straßenfertiger in einer planungsgemäßen Trasse mit Hindernissen, die durch eine automatische Breitensteuerung der Ausziehbohle berücksichtigt werden, und

Fig. 7

eine schematische Draufsicht auf einen in einer planungsgemäßen Trasse fahrenden Straßenfertiger mit Ausziehbohle, dessen Ausziehbohle mit variabler Arbeitsbreite arbeitet.

Embodiments of the invention are explained with reference to the drawing. Show it:

Fig. 1

2 shows a functional diagram of the method according to the invention in a construction machine in the form of a paver with a screed of constant working width,

Fig. 2

2 shows a diagram-like machine configuration of the finished road for the functional diagram of FIG. 1,

Fig. 3

a functional diagram for carrying out the method in a construction machine designed as a paver with a screed,

Fig. 4

3 shows a machine configuration for the road paver suitable for the functional diagram of FIG. 3,

Fig. 5

a machine configuration as an example of a construction machine with a measuring point attached to the driving unit, namely a paver with a screed,

Fig. 6

a schematic plan view of a paver in a planned route with obstacles, which are taken into account by automatic width control of the extending screed, and

Fig. 7

is a schematic plan view of a road paver traveling in a planned route with extending screed, the extending screed of which works with a variable working width.

1 and 2, a method for controlling a self-propelled construction machine A based on a functional plan (Fig. 1) and one shown in Fig. 2 Machine configuration explained. Construction machine A is, for example, a paver with a driving unit M and a working device B, namely one on bars 1 towed screed with constant working width. The construction machine A is self-driving. The transverse and longitudinal slopes of the screed are included Adjustable elements, as well as the height of the screed above the Subgrade. The screed is in a linear guide 2 on the spars 1 transverse to Direction of travel back and forth adjustable, by means of at least one control element 3, for example a hydraulic cylinder, which is controlled by a controller C1 becomes. In the driving unit M there is also a controller C for functions of the driving unit M is provided, e.g. for the driving speed, the steering angle etc. From the Control C2 off may also have functions in and on the screed controllable. Furthermore, in the embodiment shown, a system computer CPU is on the driving unit M provided (Fig. 2).

The screed has sensors 4 for the longitudinal and / or transverse inclination the control C2 and / or the system computer CPU are connected. At the Screed is fixed to a measuring point P, for example at one at one End 5 of the screed stationed mast 6, which carries a prism 18, the measuring point P defined. The driving unit M can be steered in the direction of a double arrow 15. On The driving unit M is provided with a real or virtual reference point 9.

The procedure below for automatically controlling the paver is also for other self-propelled construction machines with at least one each Appropriate working device. Such construction machines are without the scope want to restrict the invention, for example with paver Extending screeds (high compaction screed or normal screed), graders with graders, Slipform paver with supporting frame, slipforms and at least one Screed, traffic area recycling equipment and caterpillars with drawn or pushed Dozer blade.

To control the construction machine A based on the measuring point P, a geodetic Positioning system G used, which via a signal and information transmitting Route 17 is connected to the system computer CPU. The system computer could be arranged externally of the construction machine A and with the control communicate with the construction machine.

Examples of geodetic positioning systems that are useful here would be the well-known GPS system, which works satellite-guided, the DGPS system, the satellite-guided and with a stationary reference station to specify the Position determination works (DGPS = differential GPS), or a total station, the stationary near the construction site or the planned route, for example is arranged within a range of 5 km and in the manner of a high-performance theodolite with laser scanning of the measuring point P.

In the function diagram in FIG. 1, the actual position of the actual point P is turned on in a step S1 the screed B in the x, y, z directions. If necessary, a second measuring point provided on the screed or on the construction machine and be scanned.

From the known, planned data or the planned course The route that the screed is to follow in the terrain is specified with regard to of the target position of the measuring point P, i.e. it becomes a digital one in a step S2 Prepared terrain model. The course of the planned route is, for example determined by the course of the edges, the thickness, the inclination and the width of a ceiling layer to be installed on a subgrade, the driving unit drives on the formation and the screed above the specifications of the formation is managed.

Furthermore, using machine-specific information, for example of the signals from the sensors 4 and from signals which indicate the height adjustment of the screed represent a spatial machine model created above the formation. in the Step S4 takes place with the planning data from step S2 and the spatial machine model a target-actual comparison from step S3, for example by calculation in the CPU system computer.

The position is then controlled on the basis of a detected position deviation Working device, in this case the screed. The screed becomes transverse is adjusted to the direction of travel in the linear guide 2. At the same time, the Signals from the sensors 4 and, via the control C2, also longitudinal and / or bank adjustments and screed height settings according to the target values be made. This takes place in a step S5. Become such Adjustments made, then the respective change in position in a step S6 of the screed relative to the driving unit M. In a step S7 is off the result of step S6 determines a directional deviation, expediently in the form of a direction vector 8 between the measuring point P and the virtual one or real measuring point 9 on the driving unit M.

In step S8, the steering of the driving unit M is controlled by a longitudinal movement in the direction of the double arrow 15 the driving unit M, e.g. according to the Target values from the planning data, automatically steer and the working device to track.

3 and 4, the automatic control of a construction machine A is based of a paver with a so-called extending screed. The the Extending screed representing working device B is on the spars 1 of the driving unit M hauled and is in its height above the formation, and in its transverse and / or Longitudinal inclinations adjustable. It has one connected to the spars 1 Screed base body 10 of predetermined working width and two extending screed parts 11, 12, which can be extended and retracted relative to the basic screed body 10 via adjusting elements 3 ', 3 " are. The measuring point P is attached to a mast 13 in an elevated position, the one on a screed part 11, preferably in the outer End, is fixed. The height of the measuring point P is selected so that the Total station T of the geodetic positioning system G also via terrain-related Elevations or construction site-related obstacles "see" the measuring point. Each screed part 11, 12 can be transverse to the direction of a double arrow 7 Move the direction of travel back and forth. The height settings are made in the direction of a Double arrow 14. Steering movements of the driving unit M are in the direction of a Double arrow 15 controlled. The virtual or real measuring point 9 on the driving unit M is used to generate a direction vector 8 between the measuring points P, 9. Die Total station T scans the actual position of the measuring point P, for example using laser beams and communicates with the system computer, not shown. In the total station For example, a high-performance theodolite 16 is provided. The total station T can work independently from a GPS system. But it can be useful be using position information from a GPS or DGPS system.

In step S2, target values for the position of the Measuring point P or the target working position generated. Is the measuring point at the end of the Extending screed part 11, then its position represents the actual working position the decisive element of the extending screed for the route, e.g. the outer, lower edge of the screed part 11. Is the Measuring point P further inside, then in this case its transverse distance from the outside lower edge of the screed part 11 as a constant value for determining the Actual work position taken into account. In step S3, a spatial machine model created, for example, the working device B, with information from the sensor 4 and a height sensor for the height of the screed. This spatial machine model is converted into digital with its actual working position Terrain model set, which is generated from target values of the planning data. in the Step S4 becomes a positional deviation between the actual position of the measuring point P or the actual working position and the target position.

In step S5, an adjustment is made on the basis of the calculated position deviation the screed. The screed part 11 is in the direction of Double arrow 7 adjusted by a certain amount transversely and relative to the driving unit M. is then to form a planned route with a constant working width in step S9 the other, opposite screed part 12 is adjusted in opposite directions, i.e. when extending one screed part 11, the other screed part 12 retracted accordingly, and vice versa. However, it is a varying one Drive working width, then the other screed part 12 is controlled individually, where its respective location based on the machine-specific data or Sensor signals is determined and set.

In step S6, the one that occurs due to the adjustment of the one screed part 11 Change in position of measuring point P compared to measuring point 9 of the driving unit M captured.

In step S7, the change in position or the directional deviation or the direction vector 8 is determined, in comparison to the previous relative position of the two measuring points P, 9.

Finally, in step S8, the steering of the driving unit M is controlled by the Tracking unit M of the extending screed. With the automatic steering of the Driving unit can also relative or absolute directional deviations measured against a planned reference direction and taken into account by a compass, a direction sensor or a GPS system measured direction information.

Basically, the scanning of the measuring point P becomes the actual working position the working device, e.g. the screed, or one for the planned one Line of relevant elements of the working device, e.g. one Extending screed part outer edge, captured to the working device exactly in the planned Route to drive. The measuring point is directly on the relevant element arranged the working device so that it exactly its movements follows, then the measuring point largely represents the actual working position. Is the Measuring point, however, on the driving unit or, for example, the screed spar fixedly arranged, then machine-specific to determine the actual work position Data also taken into account to determine the respective position from the actual position Obtain actual work position. In the latter case, this can be done using direction vectors take place, so that for example the outer lower edge of the screed or even the rear end of the edge exactly along a line of the planned one Route is maintained. The opposite can also be used as a starting point Edge.

In the machine configuration in Fig. 5 is based on a paver with an over Spars 1 towed extending screed B the measuring point P on a mast 13 arranged in an elevated position on a spar 1. It will be real or virtual Measuring point 19 at the outer lower edge of one screed part 11 or even the position of the rear end 20 of that edge, e.g. about one Direction vector 25 and with corresponding measurements of the sensor 4 or one Screed height sensor (not shown). This real or virtual measuring point 19 and the end point 20 are routed in the planned route e.g. by adjusting movements in the direction of the double arrows 7, 14. The other screed part 12 becomes exactly the opposite direction depending on whether a constant working width is to be traveled adjusted, or individually if the working width varies according to plan. The real or virtual further measuring point is on the driving unit M of the construction machine A. 9 is provided so that a direction vector between the measurement points 9 and P. 8 can be calculated, for automatic steering (steering movements in the direction of the double arrow 15) of the driving unit M is used to move the driving unit M of the working device B to track.

6, an automatic width control of the working device B, here an extendable screed of a paver to be explained. This automatic Width control can be completely independent of an automatic guidance control the construction machine A are used or this is superimposed to Obstacles H in the planned route must be taken into account. On the paver A, for example on the screed parts 11, 12, are sensors 23, e.g. Ultrasonic sensors, which are placed on the formation with a view to emerging Scan obstacles H. This may even take place while the paver is running with the total station T and the measuring point attached to the screed part 11 P is controlled automatically. Sets one of the sensors 23, for example oncoming left-hand obstacle H, e.g. a gully, firm, that's how it will be Actuating element 3 ', taking into account the driving speed of the driving unit M, around the one screed part 11 according to the dotted line 21 around the obstacle H. The other screed part is correspondingly 12 guided by its sensor 23 around obstacles present on the right. This on-board latitude control with the automatic is expediently Control combined, i.e. the adjusting movements of the respective screed part 11 or 12 when driving around an obstacle H in automatic control ignored, so that the screed is still along the planned route travels, for example along a line 22 of the route. Scanning areas 24 of the sensors 23, which could additionally or alternatively also be arranged on the driving unit M, are sufficiently deep and wide. There may be a plurality of sensors provided precise information about the position, width and length of the Win obstacles.

Finally, FIG. 7 shows how an automatic width control of the working device B, here the extendable screed of a paver, with the help of the geodetic Position determination system, here a total station T, made becomes. The exact coordinates for the location and size of an obstacle H are in the contain planned data that are processed by the controller. Further is the course of, for example, the planned edge line 22 with an alternative bay 22 'known. The measuring point P is arranged on a spar 1 as in FIG. 5. Direction vectors 25 and 8 are used to determine the actual working position of the Measuring point 19, 20 and the actual position of measuring point 9 on the driving unit M. In addition, based on the planned data of the obstacle H and over the process computer CPU corresponding to the measuring point 19, 20 of the one screed part 11 the dotted line 21 around the left-hand obstacle H. In the evasive bay 22 ', on the other hand, becomes the actuating element based on the planned data 3 "of the other screed part 12 is adjusted to the evasive bay 22 ' to form. The driving unit M can continue to be steered automatically in such a way that the obstacle H and the escape bay 22 'only by the adjustments of the screed parts 11, 12 are deliberately steered to the right, in combination with appropriate Adjustment movements of the two screed parts 11, 12. In the case of FIG. 7 described automatic width control of the extending screed B is strict controlled according to planned information on obstacles H or the like, with continuous determination of the actual working position of the measuring point 19, 20 via the measuring point P.

In the above process and design variants, each with a geodetic positioning system worked. In practice, this means that at least two such geodetic positioning systems exist have to be because one is used to control each section of the route will be adjusted during the subsequent route section got to. As an alternative, the automatic control could be in a route section the construction machine with two geodetic positioning systems working simultaneously be made, the one for example the working device and the other controls the driving unit. Then would be for the continuous A total of four geodetic positioning systems are required.

Claims (13)

1. A method of controlling on a planned route a self-propelled construction machine (A), such as a road finisher having at least one paving screed, or a crawler with a bulldozer blade, a grader with a grader blade, a slip form paver with slip forms and at least one screed, or a traffic-area recycling machine, said construction machine comprising a drive unit (M) and at least one work device (B) which is movable relative to said drive unit by means of adjusting elements (3, 3', 3"), and said method comprising the steps of deriving correction signals by comparing detected actual positions and desired positions and processing said correction signals for the purpose of control, characterized by the following steps:

   by means of a geodetic positioning system (G, T) the actual position of a measurement point (P) arranged on the drive unit (M) or on the work device (B) is determined while the construction machine travels on the planned route,

   the actual work position of the work device (B) is determined on the basis of the actual position and on the basis of machine-specific position information,

   position deviations are detected on the basis of a comparison between the derived actual work position and a planned desired work position,

   the correction signals for the adjusting elements of the work device are generated on the basis of the position deviations,

   the adjusting elements are actuated on the basis of the correction signals so as to bring the actual work position to the desired work position and so as to guide the work device on the planned route, characterized by the following additional steps:

   directional information is determined on the basis of the desired work position and on the basis of machine-specific position information concerning the relative position between the work device and the drive unit (M),

   on the basis of the directional information, the drive unit (M) is automatically steered on the planned route and caused to follow the work device (B).
2. A method according to claim 1, characterized in that, for automatically steering the drive unit (M), the relative or the absolute directional deviation relative to a planned reference direction is measured.
3. A method according to claim 1, characterized in that, for automatically steering the drive unit (M), directional information is taken into account, which has additionally been calculated, derived from a digital terrain model, or measured, e.g. measured by a compass, a direction sensor, or a GPS-assisted system.
4. A method according to at least one of the preceding claims, characterized in that generated planned, machine-specific and geodetic data are processed by means of at least one system computer CPU provided as a stationary unit or in the construction machine (A).
5. A method according to claim 1, characterized in that the directional information for automatically steering the drive unit (M) is ascertained in the form of direction vectors (8, 25) related to the measurement point (P).
6. A method according to at least one of the preceding claims, characterized in that, in the case of a road finisher having a dragged paving screed of unchangeable operating width, the measurement point (P) is arranged on the paving screed (B) and the paving screed is adjusted to the right and to the left by means of the correction signals in a linear transverse guide means (2), e.g. the drive unit (M), making use of at least one linear adjusting element (3), and that the longitudinal and/or transverse inclination(s) of the paving screed is/are additionally adjusted according to planned predetermined data, e.g. in the digital terrain model.
7. A method according to at least one of the claims 1 to 5, characterized in that in the case of a road finisher having an extendable paving screed provided with extendable screed components (11, 12) and with width adjusting means (3', 3"), said width adjusting means (3', 3") is activated by the correction signals, that, for an application width of the route remaining uniform as planned, the second extendable screed component (12) is adjusted by the width adjusting means (3") in a direction precisely opposite to the direction of the first extendable screed component (11) or, for an application width varying as planned, the second extendable screed component (12) is adjusted individually relative to said first extendable screed component (11), and that the longitudinal and/or transverse inclination(s) of the paving screed is/are adjusted according to planned predetermined data.
8. A method according to claim 1, characterized in that the actual work position of an element (20), which is of decisive importance to the planned route, is determined as actual work position of the work device (B) by means of the measurement point (P) which is fixedly attached to the drive unit (M) and by means of determined machine-specific information concerning the respective relative position between the measurement point (P) and said decisive element (20).
9. A method according to claim 1, characterized in that the actual work position of the work device (B) is determined by means of the measurement point (P) which is fixedly attached to the work device (P) at a fixed position relative to the at least one element which is of decisive importance to the planned route.
10. A method according to claim 1, characterized in that, in the case of a road finisher constituting the construction machine (A) with a paving screed constituting the work device, an automatic width control of the extendable paving screed (B) by temporarily reducing the operating width only on the side of the obstacle (H) is carried out, on the basis of the actual work position, for driving round at least one obstacle (H) which is taken into account in the plan and which occurs in the course of the planned route, said actual work position being determined with the aid of the geodetic positioning system.
11. A method according to claim 10, characterized in that the automatic width control of the extendable paving screed is carried out with the aid of sensors (23) which are arranged on the road finisher and which detect an obstacle (H) approaching along the planned route, said sensors activating adjusting elements (3', 3") of the extendable paving screed in accordance with the detected width and length of said obstacle (H).
12. A road finisher comprising a drive unit (M), a dragged paving screed coupled to said drive unit (M) via beams (1), and longitudinal- and transverse-inclination sensors (4) on the paving screed, wherein said paving screed either has a fixed operating width and is adjustable to the left and to the right by means of adjusting elements (3) in a linear transverse guide means or comprises screed components (11, 12) which are adapted to be extended and retracted by means of adjusting elements (3', 3") so as to vary the operating width, and said road finisher being adapted to be controlled in accordance with the method according to claim 1, characterized in that the road finisher has provided thereon on a beam (1) an upright mast (13) carrying a measurement point (P) provided for a stationary, geodetic positioning system including at least one process computer (CPU), and that at least one real or virtual reference point (9, 19, 20) is provided on the drive unit (M) or on the drive unit and on the paving screed, said reference point (9, 19, 20) being used for generating at least one direction vector (8, 25) between said measurement point (P) and the reference point (9, 19, 20) for automatically steering the drive unit (M) provided with an actuable steering system.
13. A road finisher according to claim 12, characterized in that the real reference point (19) is the end of a lower outer paving-screed edge or smoothing-plate edge which constitutes the rearmost end (20) in the travelling direction.

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