SENSOR SYSTEM FOR A ROAD PAVER

Description

[0001] Embodiments of the present invention relate to a sensor system for a construction machine, in particular for a road paver. Further embodiments relate to a construction machine, or in particular a road paver, with a corresponding sensor system. Additional embodiments relate to a method for determining a distance to a reference and / or an angle relative to the reference. Additional embodiments relate to a computer program. Preferred embodiments relate to a steering sensor for a road paver and a height sensor for leveling a paving screed for a road paver.

[0002] If we consider the main tasks of a road paver in practice, in addition to highly accurate leveling of the screed, precise steering is also necessary. Today, this is usually carried out manually by the paver operator. For the most accurate paving, the paver driver must make steering corrections according to a specified reference so that the paver travels as parallel as possible and at the same distance from this reference. Inaccuracies in the steering and interference require a steering correction of the screed, which is carried out by the screed operator via the control of the extendable section of the screed. Only the continuous and precise adjustment of the steering of the tractor section of the paver and the tracking of the extendable section of the screed guarantee the correct road course specified by the reference.

[0003] Automating the entire steering process (tractor and screed) could significantly reduce the workload of the paver operator during asphalt paving. Various sensor concepts for this purpose are known from the prior art, as outlined in US 4,647,784 A, US 9,587,937 B2, DE 10 2011 113752 A1, US 2018 / 164829 A1, DE 100 60 903 A1, and US 2018 / 237999 A1.

[0004] For this automation task, a sensor, hereinafter referred to as a steering sensor, is required that is capable of adapting to different reference types, tracking them, and determining the distance to the reference with high accuracy. Therefore, an improved approach is needed.

[0005] The object of the present invention is to create a sensor concept that achieves an improved compromise between accuracy, adaptability for different application conditions and ergonomics.

[0006] The problem is solved by the independent patent claims.

[0007] Embodiments of the present invention provide a sensor system for a construction machine, in particular for a road paver, comprising at least one (first) laser scanner and an evaluation unit. The first laser scanner is arranged, for example, laterally on the construction machine / road paver itself. The laser scanner is designed to search a predetermined angular range (e.g., a semicircle or 180-degree arc, or a full circle or 360-degree arc, or another angular range) for one or more objects (such as a rope, a marking, a milling cutter or curb edge, or the like) and to determine corresponding distance values ​​describing the distance to the one or more (found) objects, together with corresponding intensity values ​​describing the intensity of a reflection occurring at the one or more objects.This determination is made over the predefined angular range, specifically by assigning the distance values ​​or intensity values ​​to a respective angle within the predefined angular range. The evaluation unit is designed to recognize an object as a reference together with the associated angles based on a known pattern consisting of or comprising the distance values ​​and the intensity values ​​across the angles. Here, for example, based on a specific pattern (combination of the variation in the intensity values ​​together with the variation in the distance values ​​across the angles), the curb or the rope is recognized or even differentiated from one another so that it can serve as a reference. Furthermore, the evaluation unit is designed to determine a distance to the reference and / or an angle relative to the reference.For example, the distance between the first laser scanner and the reference is determined and / or an angle from a reference position (e.g. a horizontal line) to the determined reference.

[0008] In exemplary embodiments of the present invention, the underlying principle is that laser scanners, enhanced by appropriate evaluation capabilities, are suitable for detecting and differentiating measurement data patterns from various references relevant for steering or for height control / leveling of a paving screed of an asphalt paver, or more generally for controlling an asphalt paver. Furthermore, the evaluation unit analyzes or tracks the measured values ​​associated with the detected reference (continuously, particularly along the travel path of the construction machine) to determine the (lateral) position of the asphalt paver relative to the reference (e.g., distance or angle). According to a first application scenario, the described sensor system advantageously enables very precise control of the asphalt paver's steering, for example, during asphalt paving.The corresponding distance values ​​are forwarded to the steering system, for example. Based on this position information, the steering corrections or, in general, the steering task of the road paver or, in general, the control task of the road paver can optionally be automated. This corresponds to a control loop for the steering, which largely relieves the operating personnel of the steering task.

[0009] According to one embodiment, the laser scanner can alternatively or additionally be arranged on an extendable part of a screed of the road paver (or generally on a movable tool of the construction machine) in order to determine the (transverse) alignment of the component with respect to the reference. This results in the following application scenario, for example: In addition to or instead of the steering task, the sensor system can also advantageously be used to control the screed width: laser sensor(s) arranged on the extendable parts of the screed serve, for example, to guide the extendable parts of the screed towards a reference. The task of the (alternative or second) control loop constructed in this way for controlling the extendable parts is therefore to keep the distance to the reference constant by moving the extendable screed parts accordingly in order to enable small corrections to the width / transverse position of the pavement to be applied.

[0010] According to one embodiment, the laser scanner can alternatively or additionally be arranged on the towing arm or near the towing point and / or on the screed, for example on a side plate of the screed or on an extendable part of the screed of the road paver, and can be used or deployed as a height sensor to provide height information alternatively or in addition to the steering information. The sensor system can therefore advantageously also be used to control the height or level the screed. If the laser scanner is mounted near the towing point, it is also suitable, for example, for sensing the height of a reference cable. In this case, the sensor position of the laser scanner can, under certain circumstances, have a different (mounting) position when used as a height sensor than when used as a steering sensor, e.g. near the towing point of the construction machine, while the sensors used for steering purposes can be mounted at the corners.

[0011] As already indicated above, the evaluation unit is designed to recognize different types of objects as a reference based on different known patterns. For example, according to embodiments, the evaluation unit can be connected to a user interface via which a user has the option of making a user selection regarding the type of object to be recognized. In response, the evaluation unit then searches for the corresponding type of object to be recognized, such as a corresponding milling edge or a corresponding rope, to be used as a reference.

[0012] According to embodiments, the object to be detected is a rope. The evaluation unit detects a rope, for example, when a maximum of the intensity values ​​is present in the form of a (narrow) peak and when, at the same time, a minimum of the distance values ​​is also present in the form of a (narrow) peak. A (narrow) peak has, for example, a width of 2° to 4° or of 1° to 7.50° (generally in the range 0.1° to 10° or 15°). Alternatively, the evaluation unit can also detect a rope when a peak-shaped change (maximum) of the intensity values ​​and a peak-shaped change (minimum) of the distance values ​​are detected at the same angle in the specified measuring range. When using a rope as a reference, a distinction must be made between two modes (detection from a bird's eye view from above or detection from a lateral perspective).According to one embodiment, the evaluation unit detects a rope from a bird's eye view, e.g., based on the pattern explained above, and determines an angle α within the specified angular range, e.g., relative to a plumb line on the ground from the laser scanner. Furthermore, based on the measured / determined angle α, the evaluation unit can calculate a distance a using the formula a = tan α h (height h of the laser scanner relative to the rope). According to further embodiments, the evaluation unit is designed to detect a rope from a lateral perspective and, in doing so, to determine a distance to the rope based solely on the laser measurement.

[0013] According to further embodiments, the evaluation unit is designed, either additively or alternatively, to detect an edge, such as a milled edge or a curb edge. This edge can be detected in two different modes: a side view and a bird's-eye view. For example, the evaluation unit detects an edge in a side view if the intensity values ​​exhibit a peak within a specified angular range, or if the distance values ​​form a plateau within a specified angular range. Alternatively, the evaluation unit detects a combination of a plateau in distance values ​​and a peak in intensity values ​​as an edge, particularly if the plateau and the peak occur within a common angular range of the specified angular range.According to further embodiments, the evaluation unit detects an edge in a bird's-eye view if the distance values ​​form a jump at an angle within the specified angular range or if the distance values ​​form a (continuous) maximum at an angle within the specified angular range. Preferably, the evaluation unit detects an edge if the distance values ​​form a jump at an angle within the specified angular range and, at the same time, the distance values ​​form a maximum at this angle. According to further embodiments, analogous to the detection of the rope, it is possible to determine a (lateral) distance a based on the (measured) angle at which the edge was detected, using the formula a = tan α*height h.

[0014] According to a further embodiment, the evaluation unit is designed to detect a line, e.g., from a lateral perspective on a wall or from a bird's-eye view on the ground. According to embodiments, the evaluation unit detects a line when a maximum of the intensity values ​​in the form of a peak in combination with a continuously / steadily varying distance value or even a minimum of the continuously varying distance value is obtained at an angle. When determining the distance from the side, the distance value determined by laser is used as the reference value for control, while when the line is detected from above, the distance is determined by calculating the angle.

[0015] Depending on the specific implementation, the evaluation unit continuously reads the distance values, e.g., while driving, i.e., over a certain period of time or over a distance traveled. This yields, for example, n distance values, which, due to the fact that the distance traveled is very small at the typically low speeds driven, should be essentially the same. Therefore, these final distance values ​​can be averaged using the following formula: Abstand ¯ = L = ∑ i = 0 n li n wobei li der The distance value of each measurement is , i is the number of measurements, n is the number of consecutive approximately identical measurements, and L is the mean distance value to the reference.

[0016] As already explained above, the laser sensor can be arranged either on an extendable part of the screed or on the road paver itself. According to one exemplary embodiment, the sensor system therefore comprises at least two laser sensors, one arranged on the construction machine / road paver (for steering or leveling purposes) and one or even two arranged on the (two) extendable parts of the screed (for controlling the screed width) or for height control / leveling of the screed. The sensors are preferably arranged laterally (front and rear) on the side of the reference. In this case, the front of the road paver (opposite the screed, for example in the front area of ​​the travel drive), as far forward as possible, or the rear, namely as far back as possible, is preferably selected.According to another embodiment, the two laser sensors can, of course, be arranged on only one side, for example, if one assumes that only one reference is present on one side. According to another embodiment, the sensor system comprises at least four laser scanners: two on the extendable parts for controlling the screed width, and two on the paver itself for steering the paver (for example, in the front area of ​​the drive unit) or for height control / leveling of the screed, for example, if one assumes two lateral references.

[0017] According to exemplary embodiments, the sensor system comprises a control unit designed to control the extendable sections of the screed or the screed itself. This control can be implemented taking into account a machine fixed point, assuming that the laser scanner(s) are indeed arranged on the extendable section or on the screed, but with a certain offset to the surfaces to be controlled. According to further exemplary embodiments, the sensor system comprises a control unit for controlling the steering of the asphalt paver. Here, the control structure can be implemented taking into account a machine fixed point, e.g., the pivot point of the asphalt paver.

[0018] Another embodiment relates to the fact that, in addition to evaluating an edge or determining the distance to a reference wire, the laser scanner can also generate height information for leveling a paving screed of a road paver when the leveling of the screed is carried out using a reference wire. In this case, scanning preferably occurs to the side of the reference wire. The sensor is preferably mounted on the towing arm near the towing point, i.e., in the front area of ​​the towing arm as seen in the direction of travel of the road paver, and at this position offers options for optimized leveling of the paving screed of a road paver.

[0019] According to embodiments, the control system is designed to regulate or level the screed in its height.

[0020] Another embodiment relates to a method for determining a distance to a reference and / or an angle relative to the reference using at least one first laser scanner, as explained above. The method comprises the steps: Detecting an object as a reference along with the corresponding angle based on a known pattern, comprising the distances and intensity values ​​across the angles of the given angular range; determining a distance to the reference and / or an angle relative to the reference (from which the distance can then ultimately be determined).

[0021] This method can also be computer-implemented, as shown in further examples.

[0022] Another embodiment comprises a road paver and a corresponding sensor system. Further developments are defined in the dependent claims. Exemplary embodiments of the present invention are explained with reference to the accompanying drawings.

[0023] They show: Fig. 1a a schematic representation of a sensor system according to a basic embodiment; Fig. 1b a schematic representation of possible mounting locations of the sensors of the sensor system on a road paver according to further embodiments; Figs. 1c to 1d schematic representations to illustrate the measured variables to be measured by the sensor system in relation to the controlled variables; Figs. 2a to 2d schematic representations of a road paver with differently arranged laser scanners to explain the different target references according to embodiments; Figs. 3a to 3e schematic representation to explain the pattern recognition "rope" according to embodiments; Figs. 4a to 4f schematic representations to explain the pattern recognition "milling edge" according to embodiments; Figs. 5a to 5b schematic representations to explain the pattern recognition "line" according to embodiments; Fig.6a to 6b show schematic representations of functional blocks of an evaluation unit according to embodiments; Fig. 6c shows a schematic representation of a scanning range of a laser scanner; Fig. 7a shows a schematic representation of the laser scanner for use as a height sensor according to embodiments; Fig. 7b shows a schematic representation to explain the conversion of angle information into height information according to embodiments; and Fig. 7c shows a schematic representation to explain a measurement of the number of laser pulses until a reference wire is hit.

[0024] Before exemplary embodiments of the present invention are explained below with reference to the accompanying drawings, it should be noted that suitable elements and structures are provided with the same reference numerals so that the description is applicable or interchangeable.

[0025] Fig. 1a shows a schematic representation of a sensor system 1 with a laser module as the first laser scanner 10 and an evaluation unit 20, which is connected to the laser scanner 10, for example, via a cable.

[0026] The laser scanner 10 serves as a sensor element and scans the measuring area, e.g., in a laser plane 11, for objects such as a rope, a curb, or another element that can serve as a reference. The laser plane 11 forms a fan of possible scanning angles spanned by a laser beam (60-degree fans, 135-degree fans, or 180-degree fans, or fans with any angle / angle range), which forms the unrestricted measuring area. The fan is spanned, for example, perpendicular to the direction of travel, where perpendicular can mean that a zero angle extends vertically downwards and further angles to the left and right can be scanned with + / - x°, e.g., + / -90° (scanning is possible within this area, so that the area can be referred to as the comprehensive scanning angle).For this purpose, for example, a rotating laser beam (red light or light in the IR range) is emitted along the fan and the reflection characteristics are received by a receiver integrated into the scanner. Such scanners have a scan rate of 50 Hz, for example, to ensure temporal and angular resolution. The range of such scanners is in the range of a few millimeters (1 mm) to 100 m. The use of a laser 10 as a sensor offers the advantage that it operates without contact and can not only detect objects, but also simultaneously determine the distance between the object and the laser scanner and / or the angle of the object to a reference position (e.g. a horizontal or vertical line, which can vary depending on the orientation of the laser scanner and, if necessary, is also corrected for an offset resulting from an angled alignment / misalignment of the laser scanner) with high precision.Furthermore, this sensor also enables continuous tracking of the reference. Tracking means that the distance to and / or angle relative to the reference is determined / tracked over time based on a known value (position / orientation of the scanner). The detection, tracking, and evaluation of the reference is performed by the evaluation unit 20.

[0027] The evaluation unit 20 can, for example, be implemented by a CPU and is designed to process the measured values ​​supplied by the laser module 10 in such a way that, at the end of the calculation chain, the highly accurate distance to the steering or height reference is available as a measurement result. The result is then made available, for example, to a higher-level steering control system and / or a height leveling control system.

[0028] The steering sensor 1 or sensor system 1 shown here is universally applicable, namely for both tractor steering (steering of the drive system) and for plank control (lateral position and / or height). As referenced in Fig. 1b As shown, the universally applicable steering sensor 1 (sensor system 1) or the laser module 10 can be arranged at several different lateral positions of the road paver, depending on whether the sensor system 1 is used as a steering and / or height sensor.

[0029] Fig. 1b shows a road paver 50 with a screed 50b, which is laterally limited by the extendable screed booms 50a. Depending on the extended state of the extendable parts 50a, the width of the screed 50b changes and thus also the width of the asphalt layer 52 to be paved. In order to control the road paver 50, e.g., in the paving area 52e or to adjust the screed width and / or to level the height of the screed 50b, reference is made to a reference 54, e.g., a cable stretched next to the paving area 52e. This reference can be determined using the Fig. 1a explained laser sensors.

[0030] According to one initial option, an installation position on the asphalt paver 50, e.g., at the front 50v, would be conceivable. A steering sensor 10v is shown purely as an example. Here, it is positioned at a maximum distance from the pivot point 50d of the asphalt paver. Using this mounting location 10v, the steering of the asphalt paver can be supported or automated, as explained below. The steering of the asphalt paver 50 generally aims to control the forward movement of the machine 50 during asphalt paving, parallel to the reference 54. The tractor initially takes over the actual steering of the asphalt paver 50. Appropriate steering systems are available for this purpose, which are usually operated manually.

[0031] If the distance between sensor 10v and reference 54 changes, this can occur as a result of a steering correction (rotation around the steering pivot point 50d), causing the machine's direction vector to change. This change can be detected by sensor 10v. If the paver is positioned at the time of the steering correction (see Fig. 1d ), it can be seen that at the height of the pivot point 50d the distance a has changed compared to the time before the steering correction (cf. Fig. 1c ) has barely changed, while the distance b changes significantly more. Consequently, this measure results in a corresponding signal change for the steering sensor 10v or all steering sensors located far forward or far back at the time of the steering correction. Therefore, it is advantageous, but not mandatory, to select the mounting locations of the steering sensors 10v for the tractor or in general (this also applies to the further exemplary embodiment "screed mounting location") so that they are as far away as possible from the steering pivot point 50d.

[0032] According to a further embodiment, the steering sensor can also be arranged on the screed 50b or, in particular, on the extendable part of the screed 50a. This makes it possible, in particular, to guide the side plates of the extendable parts 50a relative to the reference 54. The mounting location 10h for the steering sensor on the extendable part 50a is shown here as an example. While the steering sensor 10v serves to automate the steering of the tractor 50d, the steering control circuit for the screed can be automated using the steering sensor 10h. Minor steering inaccuracies can be corrected via the screed 50b or the extendable parts 50a of the screed 50b. According to preferred embodiments, the rear-mounted steering sensors 10h together with the screed form a control circuit, while the front-mounted sensors 10v create a steering control circuit for the tractor.In this respect, there is a separate control loop for each sensor 10v and 10h, which maintains a constant distance from the specified reference 54. In particular, minor steering inaccuracies and other disturbances that do not lead to the desired paving should be corrected by the operating personnel at the control station or automatically via the extendable part 50a of the screed 50b.

[0033] The attachment of the steering sensors to the tractor and the screed, as well as the different reference types used in parallel in practice, requires different evaluation mechanisms that not only identify the reference but also determine the distance to the reference. This is explained in detail below.

[0034] According to an optional / alternative variant, the sensor 10z can also be mounted in the area of ​​the drawbar. Furthermore, another possible mounting location for the sensor is marked with reference numeral 10bh at the trailing edge of the screed. This mounting location represents a preferred option for height control.

[0035] In Fig. 2a The case of the "steering sensor" for the tractor part of the paver for scanning a milled edge is illustrated: The 10V steering sensor of the tractor 50 is intended, as referenced in Fig. 1c und 1d As explained, the sensor should be positioned as far forward as possible so that a steering correction by the paver significantly alters the distance to the reference point 54k (here, a milled edge). This results in considerably better fine-tuning of the steering. It should be noted that this positioning is preferred, but not mandatory. Similarly, positioning sensor 10v on the side is preferred, as shown in the front view. Fig. 2a The reason for the lateral arrangement is that the reference, here the milled edge 54k, is positioned within the relevant scan area 10s of the laser scanner 10v. As shown here, the laser scanner 10v scans the substrate 52e, onto which the asphalt layer 52 is to be applied, along a measuring area spanned, for example, at a 30-degree angle, following the milled edge 54k. This relevant measuring area 10s is already inclined relative to the horizontal, e.g., by 15 degrees. Thus, an exemplary scan range of 15 to 45 degrees relative to the horizontal is achieved. It should be noted that this measuring range can vary depending on the mounting height of the steering sensor 10v (relative to the substrate 52e) and the (lateral) distance of the milled edge 54k.

[0036] Fig. 2b Figure 1 illustrates another case, namely the arrangement of the steering sensor 10v for scanning a reference rope 54s, which in turn is arranged laterally on the paver 50 shown in the front view. In this embodiment, the rope 54s is arranged by means of a rope holder 54sh at approximately the same height relative to the surface 52e as the laser scanner 10v. In this embodiment, the laser scanner 10v does not scan the surface 52e, but rather the area to the side of the rope 54s. Starting from an identical position of the sensor 10v compared to the variant shown in Figure 1, the following applies: Fig. 2a In this non-angled variant, the distance between laser scanner 10v and rope 54s is determined directly by means of the laser, which in the variant from Fig. 2a either the distance between the milling edge 54k and the laser scanner 10v taking into account the angle or the height or the angle at which the milling edge 54k is obtained taking into account the height is taken as the corresponding reference measurement.

[0037] Fig. 2c shows the use of the laser scanner 10h on the screed to scan a milled edge 54k. Here, a laser scanner 10h is located on the rear part of the paver 50. Because the screed 50b or, in particular, the extendable parts of the screed 50a are always positioned in the outer area of ​​the asphalt layer 52a to be applied due to the process, the laser scanner 50h can be aligned vertically downwards so that it detects the milled edge 54k in a bird's eye view. For this purpose, the laser scanner 50h is arranged, for example, on the side plate of the extendable part 50a such that the sensor can detect the milled edge from above, and preferably such that it detects the milled edge 54k at an angle of 0 degrees, i.e., vertically below the laser scanner 54h, when the side plate of the extendable part 50h is correctly positioned. The deviation from this correct position, i.e.The angle at which the milling edge 54k is detected can be provided as a measured value to the control loop for the extendable parts 50a of the plank 50b.

[0038] In Fig. 2d A laser scanner 10h is shown arranged on the screed for scanning a reference cable 54s. The reference cable 54s is in turn held via the holder 54sh, preferably at the height of the laser scanner 10h. This use of a cable 54s as a reference can be alternatively or in addition to the milling edge evaluation. Here, as already explained in connection with Fig. 2b explained, the distance to the reference is measured, with the measured value being made available to the control loop for the extendable part of the plank.

[0039] Based on these positions, it becomes apparent that, according to preferred embodiments, a sensor system for the control loop of the extendable parts of the screed comprises at least one laser scanner (on the side of the laser scanner for steering control) or preferably two laser scanners (left, right), while a sensor system for steering the road paver comprises one or two laser scanners. According to one implementation, the sensor system comprises an evaluation unit and four laser scanners. Alternatively, each laser scanner can also be directly coupled to an evaluation unit. This is integrated directly into the sensor according to embodiments.

[0040] According to a preferred implementation, the sensor system comprises a total of four laser scanners 10v and 10h, which are arranged on the left and right of the extendable parts 50a and the paver 50 itself at the above-explained positions.

[0041] The laser scanner 10 or the sensor system 1 can alternatively or additionally be arranged on the pulling arm 50z or in the vicinity of the pulling point and / or on the screed 50b, for example on a side plate / side shield of the screed 50b or on an extendable part of the screed 50a of the road paver, and can be used or deployed as a height sensor to provide height information alternatively or in addition to the steering information. Advantageously, the sensor system can thus also be used to control or level the height of the screed 50b. If the laser scanner 10 is mounted near the pulling point, it is also suitable, for example, for sensing the height of a reference cable 54s. In this case, the sensor position of the laser scanner 10 can, under certain circumstances, have a different (mounting) position when used as a height sensor than when used as a steering sensor.

[0042] Scanning is preferably performed laterally from the reference wire / reference cable 54s. Preferably, the laser scanner 10 is mounted on the towing arm 50z near the towing point, i.e., in the front area of ​​the towing arm 50z as seen in the direction of travel of the road paver, and at this position offers possibilities for optimized leveling of the paving screed 50b of the road paver 50.

[0043] The laser scanner 10 enables height scanning based on the angle information provided with each sample. It is crucial that the laser scanner 10 has the highest possible angular resolution. In the example according to Fig. 7a An angular resolution of approximately 0.01° is assumed. The distance to the reference wire / reference rope 54s is typically between one and four meters.

[0044] The height resolution changes with the distance to the reference wire / reference rope 54s, ie it increases with increasing distance to the reference wire / reference rope 54s. As in Fig. 7a As shown, the height resolution Δh is calculated using the formula Δh = tan angle (angle resolution of the laser scanner) · distance. For example, the (measured) angle is used in combination with the (measured) distance to the reference wire 54s to calculate Δh. With an angular resolution of approximately 0.01° for the laser scanner 10, as specified above, and a distance of 4 m, the resulting height resolution Δh is 0.70 mm. In comparison, the height resolution Δh at a distance of 1 m is approximately 0.17 mm. Such height resolution values ​​are quite sufficient for leveling the screed of a paver. Besides the change in height resolution at different distances to the reference wire / cable 54s, the number of hits by the reference wire / cable 54s also changes due to the laser beam, which emits a laser pulse with each measurement and determines the distance based on the pulse's travel time.This change in the number of hits must be taken into account for a height calculation and will be discussed in more detail below.

[0045] A measurement of the height by the laser scanner 10, which is preferably arranged on the pulling arm 50z near the pulling point, i.e. in the front area of ​​the pulling arm 50z as seen in the direction of travel of the road paver 50, relative to the reference wire / reference rope 54s is therefore determined not only by a distance measurement, but also by an angle measurement that is assigned to each laser pulse. In order to obtain height information or to determine a height that is related to the reference wire / reference rope 54s and thus also represents the relative height of the road paver pulling arm 50z to the reference wire / reference rope 54s, the angle measurement by the laser scanner 10 has a fixed reference point whose position does not change. This means that the angle information always refers to this fixed point in the laser scanner 10. Starting from this fixed reference point, the measuring system then counts nm angle steps until the reference wire or reference rope 54s is hit.Using the counted angular steps nm (alternatively using the measured angle), the distance b to the rope 54s and the angle Δα, which represents the angle between two consecutive distance measurements, the relative height (h) can be determined using the formula h = tan (nm · Δα) · b. . Fig. 7b This should be clarified in more detail. The relative height (h) determined in this way can, in turn, be offset such that, in a calibrated state, the "Finished - Reference Wire" system outputs a height value of 0 mm from the measuring system.

[0046] If the reference wire is hit several times by the laser beam, nm must be evaluated so that the value of nm reflects the center of the rope 54s. Fig. 7c This should be clarified. The number of laser pulses until the reference wire 54s is hit is calculated as follows: n m = n i + n r 2 with: nl = number of laser measurements where the reference was not hit; and nr = number of laser measurements where the reference was completely hit by laser beams.

[0047] As an alternative to calculating the height in millimeters, the count of laser pulses in nm can also be used to specify the height information. The only difference to the height information in mm is that nm is dimensionless and does not take into account the distance between the laser scanner and the reference wire.

[0048] According to a preferred embodiment, any laser scanner is suitable for searching for a specific reference, e.g., the milling edge 54k or the reference rope 54s, based on user input, and for capturing this reference for distance measurement or continuously determining the distance. The selection is made via user input or automatically, depending on availability.

[0049] According to another embodiment, another object, such as a line drawn on a wall, can also serve as a reference. Before discussing distance measurement in detail below, the laser scanner, or rather an exemplary version of the laser scanner, will be explained first.

[0050] The laser scanner 10, as used for example in Fig. 1 or Fig. 6a The laser scanner shown can, for example, be designed as a rotating laser scanner that performs a continuous distance measurement, so that all contours in the rotation plane of the laser can be measured using the measured distance vectors. In addition to the distance value, the measurement vector from the laser scanner also contains information about the signal strength (reflectance of the measurement) and the measurement angle, which refers to an internal reference point. For this purpose, reference is made to the Fig. 6c The scanning area shown is referred to. As can be seen, the scanning area has two reference axes, namely a horizontal reference axis 10bh and a vertical reference axis 10bv. In the exemplary embodiment, all measuring angles α1, α2, and α3 are related to the X-axis 10bv, i.e., to the vertical plumb line. When the laser scanner is permanently mounted on the paver, the reference point also has a fixed reference to the paver itself, e.g., a distance to the motion vector through the pivot point. Overall, this results in a measurement vector consisting of three information components per measurement process: Distance value to the detected object Signal strength (reflectance) and measuring angle (to a reference axis 10bv or 10bh)

[0051] Depending on the height at which the sensor 10 is positioned, a measuring angle α1, α2, and α3 results from the respective reference. The reference angle α1 is entered for scanning, e.g., a milling edge 54k from above, α2 for scanning a lateral reference 54s from the side, and α3 for scanning a temporal milling edge 54k. The measuring angles α1, α2, and α3 represent the relationship to the reference axis 10bv of the laser plane.

[0052] The following refers to Fig. 3a bis 3e and 4a to 4f explain the pattern recognition of the respective reference. For the steering reference, or for the reference in general, the following possibilities arise in practice: Milling edge Tensioned reference cable Reference lines Curb edge

[0053] Every steering reference, or reference in general, has a specific reference contour. When scanned, this contour produces specific signal patterns, from which the reference can be identified. These signal patterns must be analyzed in an evaluation algorithm to determine not only the reference but also its exact distance.

[0054] In Fig. 3a The pattern recognition of a rope 54s using the laser scanner 10 is shown. The laser scanner 10 provides only a few measurements (3 to 5 measurements - depending on the distance and rope diameter) with a high signal amplitude and thus with a high reflectance. All further measurements are either further away and / or have a low signal amplitude.

[0055] For those in Fig. 3a The sampling situation depicted is fundamentally the result of the one described in Fig. 3ba The signal curve shown is for distance measurement values ​​15a and signal strength 15s. These two measurement values ​​15a and 15s are plotted against the measurement angle. As can be seen, peak-shaped signal curves for the measurement values ​​15a and 15s form in the scan area 17, e.g., in the range between 88 and 92 degrees. These characteristics of a change (minimum) in the measurement distance 15a occurring at the same angle with a change (maximum) in the signal strength 15s at an angle enable the detection of a rope. Starting from the measured value 15a at its minimum, the distance to the reference can be determined. In this respect, for the situation of lateral rope detection, the evaluation algorithm has the task of determining the minimum distance to the reference at maximum signal strength, which then also reflects the measurement distance to the reference.

[0056] Fig. 3bb illustrates an alternative signal curve for distance measurements 15a and signal strength 15s. Here, the scan range 17 is limited by minima 17b, between which a maximum of signal strength 15s develops. When detecting the rope, the minima 17b can be used in addition to the maximum signal strength.

[0057] Fig. 3c illustrates the scanning situation with a laser scanner 10 for detecting a cable 54s arranged below the laser scanner 10. In this case, the laser scanner is arranged, for example, on the side plate of the screed 50a. With such a measurement, the Fig. 3d The signal curve shown here. As can be seen here, the minimum and maximum of signal strength 15a and measuring distance 15s coincide in the scanning area 17, so that the position of the rope or the measuring angle for the rope can be detected here.

[0058] The evaluation of the reference rope 54s from above has measured values ​​with high signal amplitudes for a relatively large scan angle (30° to 50°), whereby a measurement jump (measured values ​​suddenly smaller) occurs directly above the reference rope. Fig. 3c shows the basic arrangement of the laser scanner 10 and scanning area 17, while Fig. 3d The corresponding signal waveform is illustrated. It should be noted that the measuring distance to the rope is measured in the Y-direction. However, a distance value in the X-direction is required for the control system. For this, as shown in Abbildung 3c shown a conversion can be made.

[0059] Therefore, in this embodiment, the distance is not determined solely by the distance value resulting from measurement 15a, but rather by the following calculation. The calculation is shown below based on: Fig. 3e explained. Fig. 3e shows the diagram Fig. 3d , which shows that measured values ​​15a and 15s coincide at position α = 0 degrees. The distance to the rope, or the height h above the rope, can be determined from measured value 15a. Therefore, the laser scanner 10 is located vertically above the rope 54s, which, in this embodiment, establishes the zero reference, i.e., the measured value at this point has the value α = 0. If the angle to the rope now changes, the distance a can be determined using the formula a = tan α · h, as shown in Fig. 3e The distance value a determined in this way provides the distance to the zero reference in the X direction.

[0060] While the zero reference is set in the laser scanner, the laser scanner must be installed during setup so that the distance value a is as close to zero as possible. The distance value determined in this way in the X direction can then be used as a control variable.

[0061] In this respect, the use of the rope as a lateral reference differs from the use of the rope as a reference when measuring from above, mainly in the calculation of the controlled variable, but not in the signal pattern that occurs when the object is detected.

[0062] Fig. 4a illustrates the pattern recognition of a milled edge 54k using the laser scanner 10 from the side. The laser scanner 10, for example, scans a scanning range of 15 to 45 degrees or 15 to 30 degrees.

[0063] A milling edge 54k also provides a special pattern that can be used to clearly determine the distance to the milling edge 54k. This should be Fig. 4b can be explained in such a way that the pattern of the milling edge can be recognized by successive identical measured values ​​with a relatively high signal amplitude. Abbildung 4b The signal waveforms of signal strength 15s and measurement distance 15a shown clearly illustrate the specific pattern recognition of the signal waveforms. A corresponding recognition and evaluation algorithm detects the slight increase in signal strength 15sp in the scan area 17, which represents the measurement angle for the milling edge 54h. Additively or alternatively, the evaluation algorithm can also detect approximately the same distance values ​​15a in this scan area 17. Therefore, the pattern recognition of a milling edge from the side consists of recognizing a lateral increase (see reference numeral 15s) as with the signal strength and / or a plateau 15ap for the distance measurement 15a, whereby 15sp and 15ap occur essentially in the same measurement area / angle range 17. The plateau 15ap also simultaneously represents the measurement distance to the milling edge to be evaluated.

[0064] Referring to Fig. 4c The pattern recognition of a milled edge 54k is explained from above. For this purpose, the laser scanner 10 is positioned above the milled edge 54k. The resulting signal profile is shown in Fig. 4d As shown by Fig. 4d As can be seen, evaluating the milling edge 54k from above results in a relatively large scan angle (e.g., 30° to 50°) of measured values ​​for signal strength 15s and measurement distance 15a with a high signal amplitude. At signal strength 15s, a measurement jump 15ss from h1 to h2 is observed at the position of the milling edge. This jump provides the exact position of the milling edge with respect to the measurement angle (here: α = 0 degrees). Crucially, in addition to the distance values, the scan angle at which the height jump from h1 to h2 occurs is decisive. The distance measurement here serves only to detect the change in distance from h1 to h2. Assuming that the angle α = 0 degrees or any angle within the measurement range is used as the reference value, in this application it is not the distance, but rather the scan angle at which the height jump occurs that needs to be kept constant.Alternatively, the scan angle can also be converted into a distance value (lateral or vertical distance), as shown in . Fig. 4e und 4f becomes apparent. Fig. 4e is the situation out Fig. 4c shown, however, the scanner 10 is not positioned vertically above, but laterally offset from the milling edge 54k. This results in an angle α (angle of the jump). Based on the formula a = tan(α) h, where a is the distance and h is the height (cf. Fig. 4f ) the lateral distance can be determined.

[0065] Both for the variant from Fig. 4c as well as for the variant from Fig. 4e For the distance calculation to the reference, the signal pattern from Fig. 4d Relevant. If the laser scanner 10 is positioned vertically above the milling edge 54s, the zero reference is defined here, meaning the measurement angle at this point has the value α = 0 degrees. If the laser scanner 10 is not positioned vertically above the reference (here, milling edge 54k with an upward right offset), the measurement angle α changes relative to the zero reference. The measurement distance to the reference can therefore be calculated like the tangent value, so that the distance value a determined in the X-direction (laterally) represents the distance to the zero reference. While the zero reference is defined in the laser scanner, the laser scanner 10 should be installed during setup so that the distance value a is as close to zero as possible.

[0066] The following refers to Fig. 5a a pattern recognition of a line 54l, e.g. on a tunnel wall 54t, is explained.

[0067] Fig. 5a shows a laser scanner arranged on a plank or in the extendable part 50a of the plank 50b, the measuring range of which is aligned such that it scans the tunnel wall 50t laterally. The reference line 54l attached to the tunnel wall 50t also provides a special pattern with the help of which the distance between the reference line 54l and the laser scanner 10 can be clearly determined. The example described here refers to a light (e.g. white) reference line 54l on a dark background (e.g. a concrete wall 54t). For the sake of completeness, it should be pointed out that with the described pattern recognition, a dark line 54l (e.g. black or gray line) on a light background 54t can also be recognized, in which case the representation of a signal curve is essentially reversed.

[0068] Fig. 5b The graph shows the signal waveform of signal strength 15a and measurement distance 50a plotted against the measurement angle α. The measurement vector with the highest signal strength, 50s, is used as the distance value to the reference, since a peak-shaped change (maximum) in signal strength 15s (see reference symbol 15sp) results from reflection at the line with the higher reflectance 54l. The distance at this measurement angle is taken as the distance measurement value (regardless of whether a maximum of 15a is present or not).

[0069] In the embodiment described above, it was assumed that a measurement was always taken to determine the distance or angle. However, according to the preferred embodiment, the measurement was taken continuously, i.e., over the time during which the road paver can also move. To appropriately account for the measured values, especially those taken at the same position, an average can be calculated, as explained below.

[0070] The n measurements that successively yield approximately the same distance value are selected, and an average is calculated from these measurements. The following equation underlies the calculation: Abstand ¯ = L = ∑ i = 0 n li n li = distance value of the respective measurement i = number of measurements n = number of consecutive approximately identical measurements L = average distance value to the reference contour

[0071] Since the distance or an angle is now available as a reference, either directly or averaged, the determined distance or angle can be used to control either the transverse control of the finished product or the width control of the screed, or even the height leveling of the screed. Therefore, a further embodiment includes a control device 14 (see FIG. Fig. 6a ), which is designed, for example, to track the extendable part of the screed in such a way that the distance to the reference or the measuring angle relative to the reference remains constant. As in Fig. 6a As shown, the control device 14 receives the measurement distance to the reference or the corresponding angle from the evaluation unit 12. According to a further exemplary embodiment, a controller can be designed to control the road paver such that the distance to the reference remains constant. Consequently, the distance values ​​or angle values ​​in relation to a reference contour are fed to a steering control, which controls the paver such that the paver paves the asphalt as parallel to the reference contour as possible. Furthermore, the controller can be designed to perform height leveling of the screed, i.e., to regulate or level the screed in its height.

[0072] As referring to Fig. 6a As shown, the laser scanner(s) 10 can be connected to the evaluation unit 12 via a CAN bus, RS232, Ethernet, or the like. Likewise, the evaluation unit can be connected to the control unit 14 via the CAN bus. It should be noted at this point that, for example, the control circuit for the screed can have its own evaluation unit of the control device, like the control circuit for the steering control.

[0073] Referring to Fig. 6b the evaluation unit is explained in detail. Fig. 6b shows the evaluation unit 12'. The evaluation unit 12' includes a measured value filter 12f', which filters the measurement signals received from one or more laser scanners.

[0074] According to exemplary embodiments, the measured value filtering can be performed as follows: In the evaluation unit, the individual measurement vectors are first examined for their signal amplitude. Only those measurement vectors that are within the specified measurement range and also have a high signal amplitude (high reflectance) are considered. Low signal amplitudes or a low reflectance indicate that the measured value does not belong to the immediate scanning range of the reference.

[0075] Alternatively, the measurement filtering can be performed as explained above for averaging over several measurements in this measurement filter 12f'.

[0076] The measured values ​​are transferred from the measured value filter 12f' to the pattern recognition 12m', which then, as already explained above, recognizes an object, such as a milling edge, a rope, or a line, as a pattern. Which object is recognized as a pattern is determined by means of a user interface, which is illustrated here using block 13b'. The user interface can, for example, be integrated into the control system of the road paver. The desired pattern is selected via the user interface 13b' and, in particular, the measuring range is limited. This measuring range limitation is carried out by means of the measuring range limiter 12mb', which receives its input from the user interface 13b'. The background is that the laser scanners explained above typically cover a fairly large angular range and thus simultaneously detect a rope stretched at the height of the laser scanner (19 degrees compared to 10bv from Fig. 6c ) as well as a milling edge at a lower angle (e.g. 60 degrees relative to 10bv from Fig. 6c ). The measuring range limiter 12mb' is then used to limit the angular range according to the preselected reference. The limitation is achieved, for example, in such a way that the measuring filter f' arranged at the input of the evaluation unit 12' only forwards values ​​with an angular range greater than x1 and less than x2 to the pattern recognizer 12m'. In addition, the evaluation unit also has a distance calculation unit 12a', which either directly determines a distance to an object based on the measured distance value (typically evaluation of the travel time) or calculates the distance based on a detected angle of the pattern to be searched for. The unit 12a' then outputs the distance values ​​to the reference.

[0077] According to exemplary embodiments, the evaluation unit 12' is designed to detect the reference contour based on the continuously measured distance vectors and to calculate the distance to the reference. Since all the operations explained above are carried out digitally, the evaluation unit 12' primarily comprises a microcontroller, which receives the measurement vectors from the laser scanner via an interface, such as a serial interface (CAN, RS232, Ethernet, or the like).

[0078] As already explained above, the evaluation unit 12', particularly based on the function blocks 13b' and 12mb', as well as 12m', is designed to detect different reference patterns. This can be done either automatically or optionally via operator input (see function block 13b'), which limits the measuring range (see 12mb').

[0079] According to another embodiment, the reference is selected as follows: The laser scanner first scans the possible reference points (e.g. milling edge, rope, reference line on the wall) and identifies the existing reference or references. If several references are available (e.g. rope and milling edge), the user is responsible for selecting the desired reference (rope or milling edge) using a corresponding input. Once a clear reference has been defined, the scan area for the selected reference is limited so that the sensor is also fixed on the selected reference and no jumping between references can occur. Limiting the measuring area also has the advantage that the evaluation of the individual measurement vectors is reduced to a minimum, thereby accelerating the evaluation algorithm and significantly suppressing interference.

[0080] The above example assumes that these sensors relate to distance / steering sensors for asphalt pavers. Since a sensor system is being described here, it can, of course, also be used with other machines, such as other construction equipment, e.g., a grader or a compaction roller. With the grader, the system described above monitors and / or controls either the steering or the positioning of the movable tool transversely to the direction of travel (analogous to positioning or width control of the screed), or the height leveling of the tool. Therefore, the device is particularly suitable for determining the position of the entire vehicle (construction equipment in general), especially transversely to the direction of travel for steering purposes, and / or for determining the position and leveling of the movable / extendable tool (transversely to the direction of travel) for tool control.It should be emphasized again that a particular advantage of all the implementations described above is that one and the same laser sensor can be used for different purposes: once as a steering sensor directly on the paver or construction machine, and another time as a sensor for the screed or, more generally, for extendable machine parts, as well as for leveling the screed, regardless of whether the reference to be searched for is located laterally, obliquely to the side, or below. The measuring range, or the potential location of the object to be detected, is determined by the orientation of the measuring sensor and / or by limiting the measuring range. Viewed from another perspective, the measuring system, or measuring and control system, described here forms the basis for the autonomous operation of construction machines.

[0081] Although exemplary embodiments were assumed to be implemented as devices, it should be noted here that another exemplary embodiment relates to a corresponding method, which can, for example, be executed on the microcontroller of the evaluation unit 12'. The method comprises the basic steps of pattern recognition (automatically or depending on user input). Pattern recognition is performed according to the exemplary embodiments described above and, depending on the precise implementation, can recognize laterally arranged patterns such as a rope or a line, as well as laterally angled patterns such as a milling edge. Furthermore, the pattern recognition method can also include steps for detecting a rope or a milling edge from above.

[0082] Although some aspects have been described in the context of a device, it should be understood that these aspects also represent a description of the corresponding method, so that a block or component of a device can also be understood as a corresponding method step or as a feature of a method step. Analogously, aspects described in the context of or as a method step also represent a description of a corresponding block, detail, or feature of a corresponding device. Some or all of the method steps may be performed by (or using) a hardware apparatus, such as a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, some or more of the key method steps may be performed by such an apparatus.

[0083] Depending on specific implementation requirements, embodiments of the invention may be implemented in hardware or software. The implementation may be performed using a digital storage medium, such as a floppy disk, a DVD, a Blu-ray Disc, a CD, a ROM, a PROM, an EPROM, an EEPROM, or a FLASH memory, a hard disk, or other magnetic or optical storage device storing electronically readable control signals that can interact or cooperate with a programmable computer system to perform the respective method. Therefore, the digital storage medium may be computer-readable.

[0084] Some embodiments according to the invention thus comprise a data carrier having electronically readable control signals capable of interacting with a programmable computer system such that one of the methods described herein is carried out.

[0085] In general, embodiments of the present invention may be implemented as a computer program product having a program code, wherein the program code is effective to perform one of the methods when the computer program product is run on a computer.

[0086] The program code can, for example, also be stored on a machine-readable medium.

[0087] Other embodiments include the computer program for performing one of the methods described herein, wherein the computer program is stored on a machine-readable carrier.

[0088] In other words, an embodiment of the method according to the invention is thus a computer program which has a program code for carrying out one of the methods described herein when the computer program runs on a computer.

[0089] Another embodiment of the methods according to the invention is thus a data carrier (or a digital storage medium or a computer-readable medium) on which the computer program for carrying out one of the methods described herein is recorded. The data carrier, the digital storage medium, or the computer-readable medium is typically tangible and / or non-perishable or non-temporary.

[0090] A further embodiment of the method according to the invention is thus a data stream or a sequence of signals that represents the computer program for carrying out one of the methods described herein. The data stream or the sequence of signals can be configured, for example, to be transferred via a data communication connection, for example, via the Internet.

[0091] A further embodiment comprises a processing device, for example a computer or a programmable logic device, which is configured or adapted to carry out one of the methods described herein.

[0092] A further embodiment comprises a computer on which the computer program for performing one of the methods described herein is installed.

[0093] A further embodiment according to the invention comprises a device or system designed to transmit a computer program for performing at least one of the methods described herein to a recipient. The transmission can be electronic or optical, for example. The recipient can be, for example, a computer, a mobile device, a storage device, or a similar device. The device or system can, for example, comprise a file server for transmitting the computer program to the recipient.

[0094] In some embodiments, a programmable logic device (e.g., a field-programmable gate array, an FPGA) may be used to perform some or all of the functionalities of the methods described herein. In some embodiments, a field-programmable gate array may interact with a microprocessor to perform any of the methods described herein. In general, in some embodiments, the methods are performed by any hardware device. This may be general-purpose hardware such as a computer processor (CPU) or method-specific hardware such as an ASIC.

[0095] The devices described herein may be implemented, for example, using a hardware apparatus, or using a computer, or using a combination of a hardware apparatus and a computer.

[0096] The devices described herein, or any components of the devices described herein, may be implemented at least partially in hardware and / or in software (computer program).

[0097] The methods described herein may be implemented, for example, using a hardware apparatus, or using a computer, or using a combination of a hardware apparatus and a computer.

[0098] The methods described herein, or any components of the methods described herein, may be implemented at least partially by hardware and / or by software.

[0099] The above-described embodiments are merely illustrative of the principles of the present invention. It is understood that modifications and variations of the arrangements and details described herein will be apparent to others skilled in the art. Therefore, it is intended that the invention be limited only by the scope of the following claims and not by the specific details presented in the description and explanation of the embodiments herein.

Claims

1. A sensor system (1) for a construction machine, in particular a road finishing machine (50), comprising: a first laser scanner (10) that can be arranged on the construction machine and is configured to search a specified angular range for objects and to determine corresponding distance values, which describe the distance to the one or several objects, together with corresponding intensity values, which describe an intensity of a reflection resulting at the one or several objects, across angles of the specified angular range, an evaluation unit (20) configured to detect an object as a reference (54, 54s, 54k) together with an associated angle α starting from the distance values determined and the intensity values determined and a known pattern comprising distance values and intensity values across scanning angles, and configured to determine a distance to the reference (54, 54s, 54k) and the angle α with respect to the reference (54, 54s, 54k); wherein the evaluation unit (20) is configured to detect different types of the objects as a reference (54, 54s, 54k) based on different known patterns; wherein the object to be detected as a reference is a rope (54s) and / or wherein the evaluation unit (20) is configured to detect an edge (54k), in particular a milling edge or curb edge, and / or wherein the evaluation unit (20) is configured to detect a line (54l) in a lateral perspective on a wall or in a bird's eye view on a ground.

2. The sensor system (1) according to claim 1, wherein the evaluation unit (20) obtains a user selection characterizing the type of object to be detected as a reference via a user interface.

3. The sensor system (1) according to any one of the preceding claims, wherein the distance to the reference (54, 54s, 54k) to be determined is a lateral distance a between the laser scanner (10) and the reference (54, 54s, 54k).

4. The sensor system (1) according to any of the preceding claims, wherein the evaluation unit (20) detects the rope (54s) when there is a maximum of the intensity values in the form of a peak and when there is a minimum of the distance values in the form of a peak or when there is a maximum of the intensity values in the form of a peak and a minimum of the distance values in the form of a peak at the same angle in the specified angular range.

5. The sensor system (1) according to any of the preceding claims, wherein the evaluation unit (20) is configured to detect the rope (54s) from a bird's-eye view and to determine the angle α in the specified angular range and, in particular, to calculate the distance a starting from the determined angle α using the formula a = tan α · height h, wherein h represents the height of the laser scanner relative to the reference, wherein a represents a lateral distance between the laser scanner (10) and the reference (54, 54s, 54k); and / or wherein the evaluation unit (20) is configured to detect the rope (54s) in a lateral perspective and to determine the distance to the rope (54s).

6. The sensor system (1) according to any of the preceding claims, wherein the evaluation unit (20) determines the edge (54k) in a lateral perspective, wherein the intensity values form a superelevation under an angular range of the specified angular range, or wherein the distance values form a plateau of the distance values under an angular range of the specified angular range, or if there is a combination of a plateau of the distance values and a superelevation of the intensity values in an angular range of the specified angular range; and / or wherein the evaluation unit (20) determines the edge (54k) in a bird's eye view, wherein the distance values form a jump at an angle of the specified angular range or when the distance values form a maximum at an angle of the specified angular range or wherein the distance values form a jump at an angle of the specified angular range and the distance values form a maximum at the angle of the specified angular range.

7. The sensor system (1) according to any of the preceding claims, wherein the evaluation unit (20) is configured to determine the distance a with the formula a = tan α - height h starting from the determined angle α of the angular range, wherein h represents the height of the laser scanner relative to the reference, wherein a represents a lateral distance between the laser scanner (10) and the reference (54, 54s, 54k).

8. The sensor system (1) according to any of the preceding claims, wherein the line (54l) is detected when a maximum of the intensity values in the form of a peak is obtained at an angle of the specified angular range in combination with a continuously varying distance value.

9. The sensor system (1) according to any of the preceding claims, wherein the evaluation unit (20) is configured to determine a plurality of n distance values over a time or distance traveled or to determine a plurality of n distance values over a time or distance traveled and to determine the n distance values using the following formula: distance ¯ = L = ∑ i = 0 n li n wherein li is the distance value of the respective measurement, i is the number of measurements, n is the number of successive measurements, and L is the average distance value to the reference (54, 54s, 54k).

10. The sensor system (1) according to any one of the preceding claims, wherein the sensor system (1) comprises a controller configured to control the steering of the construction machine starting from the distance to the reference (54, 54s, 54k) and / or the angle α with respect to the reference (54, 54s, 54k), in particular taking into account the distance of the laser scanner (10) from a machine fixed point of the construction machine; wherein either the first laser scanner (10) is arranged laterally in the area of a front side of the construction machine; or the first laser scanner is arranged laterally on a side of the road finishing machine (50) opposite with respect to a plank (50b) of the road finishing machine (50); or the first laser scanner (10) can be arranged on an extendable part of a plank (50b) of the road finishing machine (50); or the sensor system (1) further comprises a second or second, third and fourth laser scanners (10) and the first laser scanner (10) is arranged on the road finishing machine (50) on a first side of the road finishing machine (50) and the second laser scanner is arranged on an extendable part of a plank (50b) on the first side.

11. The sensor system (1) according to claim 10, wherein the sensor system (1) comprises a controller configured to control the extendable parts of the plank (50b) or the plank (50b) starting from the distance to the reference (54, 54s, 54k) and / or the angle α with respect to the reference (54, 54s, 54k), in particular starting from a a vertical distance to the reference, in particular if the sensor system comprises the second laser scanner according to claim 10, taking into account the distances of the first and second laser scanners (10) to a machine fixed point of the construction machine.

12. A construction machine, in particular road finishing machine (50) with a sensor system (1) according to any of the preceding claims.

13. A method for determining a distance to a reference (54, 54s, 54k) and an angle α with respect to the reference (54, 54s, 54k) using a first laser scanner (10) arranged on a construction machine and configured to search a specified angular range for objects and to determine corresponding distance values, which describe the distance to the one or several objects, together with corresponding intensity values, which describe an intensity of a reflection resulting at the one or several objects, across angles of the specified angular range, comprising the following steps: detecting an object as a reference (54, 54s, 54k) together with an associated angle α starting from the distance values determined and the intensity values determined and a known pattern comprising distance values and intensity values across scanning angles, and determining a distance to the reference (54, 54s, 54k) and the angle α with respect to the reference (54, 54s, 54k); wherein different types of the objects as a reference (54, 54s, 54k) are detected based on different known patterns; wherein the object to be detected as a reference is a rope (54s) and / or wherein an edge (54k), in particular a milling edge or curb edge is the object to be detected as a reference, and / or wherein a line (54l) in a lateral perspective on a wall or in a bird's eye view on a ground is the object to be detected as a reference.

14. A method according to claim 13, comprising the further step of controlling the construction machine or a component of the construction machine depending on the distance to the reference (54, 54s, 54k) and / or the angle α with respect to the reference (54, 54s, 54k).

15. A computer program comprising program code for performing the method of claim 13 or 14, when the program runs on the evaluation unit according to claim 1.