WO2020164725A1

WO2020164725A1 - Route planning for servicing a technical appliance

Info

Publication number: WO2020164725A1
Application number: PCT/EP2019/053761
Authority: WO
Inventors: Yongzhi Liu; Yiheng CHI; Ulf GROHMANN
Original assignee: Voith Patent Gmbh
Priority date: 2019-02-15
Filing date: 2019-02-15
Publication date: 2020-08-20

Abstract

Present invention concerns planning a service task for a technical appliance. A proposed method comprises steps of determining service steps comprised by the service task, the service steps corresponding to physical access points to the appliance; determining a three-dimensional physical description of the appliance; determining minimum effort paths between pairs of access points, wherein an effort corresponding to a path is determined on the basis of the length of the path according to the description; and generating a route comprising a succession of minimum effort paths over the access points.

Description

Route Planning for Servicing a Technical Appliance

Present invention concerns servicing a technical appliance. More specifically the invention concerns determining an optimized route for servicing the technical appliance.

Background of the Invention

A technical appliance requires conducting a service task to ensure its operational safety, longevity or efficiency. The service task usually comprises several predetermined service steps, each of which may be associated to a specific location of the appliance. For instance, a first service step may comprise closing a valve in a first location of the appliance and a second step may comprise checking a gauge in a second location. If the appliance is large, e.g. a paper machine or an energy plant, a considerable distance may lie between service locations. A complex service task may comprise many service steps at different service locations and a person carrying out the service task may have to spend a significant portion of his service effort on moving between locations.

CN 101 299 861 B1 proposes a method for determining a shortest route between several base stations in a mobile telecommunications network. Station coordinates are taken from a geographic information system. The route is determined on the basis of a road network in an area of the station coordinates. However, this approach is of limited use on one coherent appliance.

A problem underlying present invention consists in providing an improved technique for planning a service task for a technical appliance. Present invention solves the given objective through the subject-matter of enclosed independent claims. Dependent claims describe preferred embodiments.

Disclosure of the Invention

According to a first aspect of present invention a method for planning a service task for a technical appliance comprises steps of determining service steps comprised by the service task, the service steps corresponding to physical access points to the appliance; determining a three-dimensional physical description of the appliance; determining minimum effort paths between pairs of access points, wherein an effort corresponding to a path is determined on the basis of the length of the path according to the description; and generating a route comprising a succession of minimum effort paths over the access points.

The route may be determined on the basis of a first optimization that finds minimum effort paths between service points, and a second optimization that determines a most favourable sequence or succession of minimum effort paths. Through this twofold optimization the determined route may represent a least strenuous succession of paths between access points. A determination effort may be minimized. The provided route may represent the shortest route or the route requiring the least effort to travel. The service task may be carried out by a service person with a minimum effort. By minimizing the effort, the task may be carried out fastest possible, freeing the person for other activities. An operational limitation of the appliance associated with the task may be shortened, thus maximizing use of the appliance. Service tasks may be scheduled more frequently or more thoroughly with the same effort. Through improved service the appliance may last longer or be operated more efficiently.

It is preferred that the technical appliance comprises a building with a machine inside. The building may form a unit with the machine in that the machine is not practically movable outside the building and the building is designed and implemented such as to house and protect the machine. In most cases the machine will not be moveable at all due its large size and/or mass. The machine could for instance comprise a paper machine, a power plant, a large scale transformer or a cement kiln, and the building may comprise a hall in which the machine is disposed. The building generally comprises a roof and may be open or closed laterally. The building may be adapted to protect the machine from environmental influences like weather. It may also protect the environment from emissions like sound or substances the machine may emit.

The three-dimensional physical description is preferred to comprise information covering both the building and the machine. In this, one joint model comprising machine and building information is preferred over a collection of separate models, especially over a combination of a first model covering the building and a second model covering the machine. The building information may especially comprise architectural information like length, breadth or height information of various sections of the building and their geometric relationships to each other; information about hardware installation (e.g. electricity, water, data or a pneumatic system), doors and windows and the like. Information covering side aspects of the technical appliance like a transport connection to the building may also be comprised by the preferred joint model.

It is preferred that a vertical component of a path has more influence on the effort of the path than a horizontal component. Vertical movement of e.g. a service person between service points or locations may require more effort than horizontal movement. Vertical movement may involve taking steps, stairs or an elevator, which may take longer time, especially in an upwards direction, or require more physical effort than horizontal movement. In the case of an elevator, a possible waiting time may be added to the effort. By accounting a vertical movement greater than a horizontal movement, the determined path may be associated a more realistic effort value.

The effort corresponding to a path may be determined on the basis of a time that is required to travel the path. In this, the physical description of the appliance may comprise travel time information along a path or a section of a path. For instance, travelling along a narrow, low-ceilinged, dark or winding passage may generally be more stressful than along a broad, high, straight and well-lit corridor. An average travel time along a path or a section may be available from the description of the appliance. The information may be explicit, e.g. in the shape of a travelling time or as a length and a given travelling speed. Alternatively, travelling time may be determined on the basis of information like an inclination or lighting conditions of a path or a section.

The effort corresponding to a path may also be determined on the basis of an obstacle along the path. Example obstacles may comprise an access lock, a manhole, a narrow passage, a low passage, a step, a gap, a barrier or a barricade. An elevator that may not be readily available may also be considered an obstacle. Each obstacle may slow down a person following the path or add to the energy required to travel the path. By allowing for the obstacle, the effort associated to the path may be determined more realistically. The effort corresponding to a path may further be determined on the basis of an environmental condition affecting a person travelling the path. Example conditions comprise heat, noise, vibration, a hazardous area or exposure to a potentially harmful substance along the path. A person being exposed to such conditions may be exhausted just by sustaining the given influences. The straining condition may especially be determined on the basis of an operating condition of the appliance. Should e.g. the appliance be running at maximum power, environmental conditions at certain service points may be more stressful than if the appliance runs on partial power. Other example operating conditions of the appliance comprise a substance being processed, a processing temperature, use of predetermined chemicals or a predetermined processing step. A relationship between operating conditions of the appliance and an environmental condition at one or more paths or service points may be indicated in the description.

The technical appliance may comprise service points on multiple floors. The appliance may be installed in-house like a paper machine, outdoors like a conveyor belt in open pit mining. The appliance may also represent an industrial installation like a water power plant or spread over more than one building like a petrochemical processing system. In other words, it is preferred that the appliance is big, typically several times as tall as a person and at least the same size in one or more horizontal directions. The appliance may comprise a machine or any other industrial facility. Typically such an appliance has more than one working floor or vertical level. Service points may be located at arbitrary positions over the floors.

The succession of minimum effort paths may be determined through a

component adapted to solve a problem of the ..travelling salesman" kind (TSP: travelling salesman problem). In this prototype problem a number of cities and relative distances between them are given and the object is to find the shortest route connecting all of the given cities, so that a fictional salesman can visit all of them without travelling further than necessary. The solution to this problem is a succession or sequence of cities. A city may occur more than once in this succession. The problem of determination of the route from the minimum effort paths may be NP-hard. Example solvers for this class of problem comprise an ant colony optimization algorithm, a simulated annealing algorithm and mixed integer optimization. Other approaches may be applicable as well.

In one embodiment the succession of minimum effort paths is determined without external constraints. In another embodiment a constraint concerning one or more service tasks is considered when the succession is determined. The constraint may especially relate to a predetermined order in which two of the service points should be visited, a timeframe in which one or more service tasks must be completed or an external condition under which a service task shall be carried out.

The physical description may be read from a building information modelling (BIM) file. BIM can be described as an emerging process of generating and managing digital representation of buildings, while containing comprehensive engineering information of the buildings in multiple cycles of their constructions. It may enable more efficient asset management and thus is becoming a popular industrial tool.

A BIM file may be in a publicly documented or a proprietary format and contain proprietary data. Information can be extracted, exchanged or networked to support decision-making regarding a building or other built asset. It is proposed to use BIM information for servicing a technical appliance, especially where the appliance is large enough to require a service person moving between service points. The appliance may have architectural character in that it may be connected to the solid ground or generally be unmovable as a whole.

According to another aspect of present invention a computer program product may contain program code means, wherein the computer program product is adapted to carry out a method according to one of the above claims.

According to yet another aspect of present invention a computer readable medium is provided on which is stored a computer program product described herein.

According to one more aspect of present invention, a device for planning a service task for a technical appliance comprises a first interface for reading the service task, the service task comprising service steps corresponding to physical access points to the appliance; and a second interface for determining a three- dimensional physical description of the appliance. The processing means is adapted to determine minimum effort paths between pairs of access points, wherein an effort corresponding to a path is determined on the basis of the length of the path according to the description. The processing means is furthermore adapted to generate a route comprising a succession of minimum effort paths over the access points. The determined route is preferred to involve a minimised travelling effort between service points.

The processing means may especially be adapted to carry out completely or in part a method described herein. To this end, the processing means may comprise a programmable microcomputer or microcontroller and the method may be implemented as a computer program product with program code means. The computer program product may be written on a computer readable media.

Features or advantages of a method described herein may be applicable to an appliance described herein and vice versa.

The physical description is preferred to be stored in storage means for storing a building information modelling file.

According to another aspect of the invention another device comprises positioning means for determining a position of the device; first memory means for storing positions of predetermined service points on a technical appliance; second memory means for storing a predetermined succession of service points on the technical appliance; processing means for determining directional information from one service point of the succession to a following service point of the succession; and output means for outputting the determined directional information.

The device may be used to guide a service person like a technician or engineer along a succession of service points. The succession of service points may be chosen such that a moving or travelling effort for the service person is minimized. The service person may be guided between service points on a minimum effort path. The succession may especially be determined according to a method disclosed herein. The guiding device may be adapted determine the succession of service parts or perform a part of the determination. In one advantageous embodiment, the device comprises sensing means for sensing an identifier that is disposed at a service point of a technical appliance. The guiding device may thus be enabled to check whether the predetermined succession of service points is obeyed. In the case of a deviation from the predetermined succession, a corresponding indication or alarm may be provided.

Brief Summary of the Enclosed Figures

The above-described properties, features and advantages of present invention as well as the way they are achieved will be made clearer and better understandable in the light of the following discussion, making reference to exemplary

embodiments shown in accompanying figures, in which

Fig. 1 shows, by way of example, a schematic representation of a

processing device;

Fig. 2 shows a flow chart of an exemplary method;

Fig. 3 show a view of an exemplary technical appliance;

Figs. 4-6 show visualizations of different processing stages during

determination of a service route for an example appliance; and Fig. 7 shows a schematic diagram of a guiding device.

Detailed Exemplary Embodiments of the Invention

Figure 1 shows a schematic representation of an exemplary device 100 for planning a service task for a technical appliance 105, which may for instance comprise a water power plant (cf. exemplary Fig. 3). The appliance 105 may comprise one or several floors 110 on different vertical levels which may be used, e.g. by a person, to access predetermined physical service points 115. Each service point 1 15 may be assigned a physical location with respect to the appliance 105.

Three dimensional information of the appliance 105 is stored in a file or set of files 125 with building information (BIM-file). The file 125 may for instance come in the Revit format or any other file format like CSV, CSL, XSLX, CSV etc. The file 125 is preferred to comprise three-dimensional geometric description of the appliance, primarily its shape and dimensions. The file 125 may also comprise the location of service points 115 and/or the layout of paths 120 between service points 115. Infrastructural information like the location and/or type of electrical power outlets, switches or lights may also be comprised. Similarly, hydraulic or heating information may be given, like the location and/or function of a valve, a gauge or a thermometer. More information may comprise environmental conditions at different locations of the appliance 105, like, humidity, temperature, sound, vibration or exposure to chemicals, their kind or concentration. Generally, the BIM file 125 may contain any kind of information for describing the physical appearance and/or certain functional aspects of the appliance 105. However, the BIM file 125 is generally not adapted to convey comprehensive information for running or controlling the appliance 105. In this, the BIM file 125 could be described as giving architectural information on the appliance 105.

A service task 135 that may be carried out on appliance 105 comprises several service steps 140, each of which may comprise a service point 1 15 or service location and a service activity 145. Generally, the service steps 140 do not have a predetermined order in which they must be carried out. For completing the service task 135 it is generally necessary for a service person to visit each service point 115 mentioned in the service steps 140 of said service task 135. Information on the service task 135 is preferred to be contained in a service file 150.

The device 100 is preferred to have a first interface 155 for retrieving information about the service task 135, especially adapted to reading a service file 150, and a second interface 160 for retrieving BIM information, especially adapted to reading a BIM file 125. The device 100 comprises processing means 165 adapted to determine, on the basis of the read information, paths 120 with the least associated effort between two service points 1 15, and a route 170 comprising a succession of least effort paths 120. The route 170 is determined such that the overall effort for visiting all service points 1 15 associated to a predetermined service task 135 is minimized. Various kinds of information extracted from the BIM file 125 may be used to determine the effort required to travel a path 120 between two given service points 1 15. The processing means 165 is preferred to be adapted to carry out a method disclosed herein. The method may be realized as a computer program product with program code means and the processing means 165 may comprise a microcomputer or microprocessor. The processing means 165 may comprise a first storage means for instruction code and optionally a second storage means for a processing result. The processing means 165 may operate on a

predetermined clock signal and comprise a corresponding clock signal generator. Semiconductors may be used for implementing the processing means 165 or parts thereof. A source of electrical energy may be used for powering the processing means 165.

Figure 2 shows a flow chart of an exemplary method 200 for determining a route 170 covering all service points 115 associated to service steps 140 of a given service task 135. The method 200 may start in a step 205 in which a service task 135 is determined. The service task 135 may for instance comprise maintenance, status report, inspection or quality control. Service steps 140 comprised by the service task 135 are identified. In a step 210, for each service step 140 a service point 115 is determined. A service point 115 represents a three-dimensional physical location at or on the technical appliance 100.

In a step 215, a three-dimensional description 125 of the appliance 105 is determined. The description comprises information on physical locations of each of the service points 1 15 and allows determination of at least one path 1 15 between any two given service points 115. It is preferred that the information contained in the description 125 also permits determination of an effort that is required for travelling a given path. In the simplest case, the effort may be a function of the distance to travel between the service points 1 15. Generally, this will not be the Euclidian distance but a more complex path, depending on the geometry of the appliance. In a preferred embodiment, a vertical movement will add more to a determined travelling effort than a horizontal movement over the same distance. It is furthermore preferred that all kinds of obstacles, necessary waiting times or stressful conditions that may apply to a person travelling a path 1 15 will be determined on the basis of the description 125.

In a step 225, a least effort path 120 is determined for at least one pair of service points 1 15. Should only one possible path 120 exist between the service points - I Q -

1 15, this path 120 is used and the associated effort is determined. Should more than one path 120 be possible, an associated effort can be determined for every possible path 120. The least effort path 120 will then be the patch 120 that is associated the smallest effort figure. After step 225, there will be one known path 120 between every pair of service points 115 and it is preferred that this path 120 is associated the least effort. A determined least effort path 120 may be stored for later reuse.

In a step 230, determined paths 120 are concatenated in such a way that all service points 1 15 will be visited and an accumulated effort figure is as low as possible. This problem is of the kind that is known as“travelling salesman problem” (TSP) and various techniques are known for finding a solution. Any such technique may be employed for determining a route 170 that comprises a succession of paths 115 (each path 1 15 being preferred to be a least effort path for the service points 1 15 it connects) that connects all service points 115 comprised by the predetermined service task 135. It is to be noted that the TSP may comprise constraints like the order in which two or more service tasks are to be carried out, a maximum time that may lie between two predetermined service tasks or an external condition that must be fulfilled for a service task be carried out. The condition may be related to the appliance 105 and/or its operation. Such a constraint could for example reflect a situation where the service task comprises a first task of taking a probe at a first service point, and a second task of delivering the probe to evaluation at a second service point. Another example comprises reading a gauge at a second service point no longer than a

predetermined time after operating a valve at a first service point. All kinds of constraints may be considered within the scope of determining an optimized sequence of minimum effort paths in step 230.

In a step 235, the route 170 may be provided. Generally, the route 170 is intended to be travelled by a service person for the appliance 105 like a technician or an engineer.

Figure 3 shows a longitudinal section view of a technical appliance 105 in the exemplary shape of a water power plant. The information given through figure 3 may be comprised by one or more BIM files 125. The pictured example appliance 105 comprises service points 115 which may be located on different floors 1 10 of the appliance. A path 120 between two given service points 115 may have

- a length in horizontal direction;

- a length in vertical direction; and/or

- a length along a slope of a given steepness.

These properties may be considered part of an effort required for travelling along the path 120. The effort may also be dependent on other properties like:

- a height of the path 120;

- a width of the path 120;

- an unevenness of a ground to walk on;

- a slippery ground and/or

- lighting conditions.

There may be one or more obstacles along the path 120 which may add to a travel effort, for instance:

- a step;

- a flight of stairs;

- an elevator;

- a gap;

- possible traffic;

- an outside area.

Environmental influences potentially increasing a travel effort for a person on the path 120 may comprise:

- noise;

- wetness;

- wind;

- vibration;

- a chemical substance;

- heat; and/or

- a hazardous area.

Apart from the given examples, additional or different properties or influences may be considered for determining a travel effort on a path 1 10. An effort for travelling along a path 120 may be determined by assigning an effort index or figure to every known influence. Effort indexes may each be multiplied with the length of a path 120 over which they apply. A sum of determined effort indexes will yield an overall effort for a path 120. It is to be noted that the effort associated to a path 120 may vary over time, especially if an operating condition of the appliance 105 has influence on the effort.

Figures 4 through 6 show visualizations of different example processing stages during determination of a service route 170 for an example appliance 105. In each of these figures, an exemplary three-dimensional representation of service points 115 is given. For the given example, only the Euclidian distance between a pair of service points 1 15 is considered for determination of a travel effort.

Figure 4 shows service points 1 15 of an exemplary appliance 105. Four of the points 115 are exemplary service points 115 that are comprised by service steps 140 of a given service task 135. Figure 5 shows an exemplary least effort path 120 between two of the given service points 1 15. The path 120 incidentally leads over other service points 115. It is assumed that other paths 120 between the same pair of service points 115 can be constructed; however, none of them is associated a lesser effort (corresponding to a shorter distance in present example). Figure 6 shows a complete route 170, connecting all four service points 115 in a succession of determined least effort paths 120. In addition, an optional extra path 120 between the first and the last service points 1 15 may be provided, closing the route 170 into a loop or round trip. The route 170 is preferred to be chosen so that an overall effort for travelling along the route 170 is minimized as far as possible.

Figure 7 shows a schematic diagram of a guiding device 700 that is preferred to be adapted to support a service person in a service task 135 that involves moving over a number of service points 1 15 of a technical appliance 105. The device 700 is preferred to comprise positioning means 705, memory means 710, processing means 715, communication means 720, output means 725, input means 730 and/or sensing means 735.

The guiding device 700 may be based upon a personal device like a smart phone, a tablet computer or a laptop computer. The positioning means 705 may comprise a receiver for a satellite based navigation system like GPS, GALILEO or GLONASS. It may also comprise an inertial sensor or any other means for determining a position of the device 700. The memory means 710 may be realized as a magnetic or logic memory and be adapted to hold different kinds of information. A first kind of information comprises a position of a service point 1 15 of a technical appliance 105 and a second kind of information comprises a predetermined succession of service points 115. The memory means 710 may also hold further information concerning the technical appliance, especially in the form of map data. Such information may comprise a BIM file 125 about the appliance 105 or be derivable from this kind of file. The stored memory may especially comprise a subset of said BIM file 125. Two or more separate memory means 710 may be provided for the different kinds of information.

The processing means 715 is preferred to be realized as a micro-computer or microprocessor, especially with a von-Neumann architecture. In a preferred embodiment the succession of service points 1 15 is received from an instance external to the device 700. This may be done via the communication means 720, which may be adapted to perform wireless communication, for instance over WLAN, Bluetooth or a mobile telecommunication network. In this embodiment a modest processing means 715 with limited computing power may be sufficient.

In another embodiment, the processing means may be adapted to carry out a method 200 according to Fig. 2 in part or completely, in which case it is preferred that the processing means are strong enough to ensure swift enough processing of said method 200.

The output means 725 may be optically, acoustic and/or haptically. The optional input means 730 may be acoustic or haptically. Output means 725 and input means 730 may be integrated into one unit for instance in the shape of a touch screen. The sensing means may be adapted to sense an identification tag 740 which may be disposed in the vicinity of a service point 115 of the appliance 105. Sensing may be done optically and the tag 740 may comprise a one- or two- dimensional optical code. Alternatively, sensing may be carried out with radio waves and said tag 740 may comprise an RFID or NFC tag. The tag 740 may provide a unique identification which is associated to a predetermined position or a service point 1 15 (which has a predetermined position).

In another embodiment of present invention there may be tags 740 at arbitrary positions in an area of said appliance 105, so that a position of the device 700 may be determined on the basis of identifications of tags 740 in the vicinity. It is preferred that said device 700 is adapted to provide an indication to a person for following a predetermined route 170 that connects a number of predetermined service points 115 in a certain succession. The route 170 is preferred to be determined such that a travelling effort for said person along said route 170 is minimized. Additional constraints may also be considered. The device may be adapted to determine its position and determine a deviation from the

predetermined route 170. Should the deviation exceed a predetermined threshold, a warning may be provided. Should a service point 115 be visited out of the predetermined sequence, another warning may be provided. The device 700 may be adapted to record a route 170 taken or a succession of service points 1 15 visited.

Even though present invention has been illustrated and explained in detail above with reference to the preferred embodiments, the invention is not to be construed as limited to the given examples. Variants or alternate combinations of features given in different embodiments may be derived by a subject matter expert without exceeding the scope of present invention.

Reference List

100 device

105 technical appliance

1 10 floor

115 service point

120 path

125 BIM file

135 service task

140 service step

145 service activity

150 service file

155 first interface (to service file)

160 second interface (to BIM file)

165 processing means

170 route

200 method

205 determine service task with service steps

210 determine access points

215 determine appliance description

220 determine service point locations

225 determine minimum effort paths between points

230 solve TSP

235 provide route

305 machine

310 building

700 guiding device

705 positioning means

710 memory means

715 processing means

720 communication means output means input means sensing means identification tag

Claims

Patent Claims

1. Method (200) for planning a service task (135) for a technical appliance (105), wherein the method comprises steps of:

- determining (205) service steps (140) comprised by the service task (135), the service steps (140) corresponding to physical access points (115) to the appliance (105);

- determining (215) a three-dimensional physical description (125) of the appliance (105);

- determining (225) minimum effort paths (120) between pairs of access points (115),

- wherein an effort corresponding to a path (120) is determined on the basis of the length of the path (120) according to the description (125); and

- generating (230) a route (170) comprising a succession of minimum effort paths (120) over the access points (115).

2. Method (200) according to claim 1 , wherein the technical appliance (105) comprises a building (305) and a machine (310) inside.

3. Method (200) according to claim 1 or 2, wherein a vertical component of a path (120) has more influence on the effort corresponding to the path (120) than a horizontal component.

4. Method (200) according to one of the above claims, wherein the effort corresponding to a path (120) is determined on the basis of a time that is required to travel the path (120).

5. Method (200) according to one of the previous claims, wherein the effort corresponding to a path (120) is determined on the basis of an obstacle along the path (120).

6. Method (200) according to one of the previous claims, wherein the effort corresponding to a path (120) is determined on the basis of an

environmental condition affecting a person travelling the path (120).

7. Method (200) according to claim 6, wherein the condition is determined on the basis of an operating condition of the appliance (105).

8. Method (200) according to one of the previous claims, wherein the

technical appliance (105) comprises Service points (1 15) on multiple floors.

9. Method (200) according to one of the previous claims, wherein the

succession of minimum effort paths (120) is determined through a component adapted to solve a problem of the ..travelling salesman" kind.

10. Method (200) according to one of the previous claims, wherein a constraint concerning one or more service tasks is considered when the route (170) is generated (230).

1 1. Method (200) according to one of the previous claims, wherein the physical description (125) is read from a building information modelling file (125).

12. Computer program product with program code means, wherein the

computer program product is adapted to carry out a method (200) according to one of the above claims.

13. Computer readable medium on which is stored a computer program

product according to claim 12.

14. Device (100) for planning a service task (135) for a technical appliance (105), wherein the device comprises:

- a first interface (155) for reading the service task (135), the service task (135) comprising service steps (140) corresponding to physical access points (1 15) to the appliance (105);

- a second interface (160) for determining a three-dimensional physical description (125) of the appliance (105); and

- processing means (165) that is adapted to

o determine minimum effort paths (120) between pairs of access points (115); the basis of the length of the path (120) according to the description (125); and

o generate a route (170) comprising a succession of minimum effort paths (120) over the service points.

15. Device (100) according to claim 14, wherein the physical description (125) is stored in storage means for storing a building information modelling file.

16. Device (700), comprising

- positioning means (705) for determining a position of the device (700);

- first memory means (710) for storing positions of predetermined service points (115) on a technical appliance (105);

- second memory means (710) for storing a predetermined succession of service points (115) on the technical appliance (105);

- processing means (715) for determining directional information from one service point (115) of the succession to a following service point (115) of the succession; and

- output means (725) for outputting the determined directional information.