Road marking robot

Abstract

The invention relates to road marking robot (100) which is autonomous and is arranged to move on a road, and comprises a mass container (105) for storing thermoplastic road marking mass and for keeping it warm, and a print head (106) for printing out thermoplastic mass. The road marking robot (100) also comprises communication means (111) arranged to receive, as a result of analysis of sensor data captured from the road, a location control signal for guiding the road marking robot (100) to move to the correct location for printing out, and a printing control signal for controlling the printing out of a road marking. The print head comprises hatches (105) which are opened at different times during movement of the road marking robot (100) to make the road marking as a pattern of thermoplastic mass flowing out of the hatches (105). The invention also relates to a method for printing out road markings by a road marking robot (100), and to a computer program product.

Description

[0001] ROAD MARKING ROBOT

[0002] Field of the invention

[0003] The invention relates to a road marking robot which is independent of a parent vehicle and comprises a print head for printing road marking patterns, a method for printing road markings by a road marking robot, as well as a computer program for controlling printing by a road marking robot.

[0004] Background of the invention

[0005] Now, increasing requirements relating to safety at road works make it necessary that road markings are made by a device. Most common road markings include longitudinal markings, i.e. lane lines, such as broken white lines which separate different lanes of a road from each other, roadside edge lines, as well as cross markings, i.e. markings made crosswise to the road, such as pedestrian crossings and symbols. Normally, longitudinal road markings are made by painting white or yellow markings on asphalt by a road marking device which may be a road marking machine constructed as a fully autonomous device, or a road marking device mounted on a truck. Cross markings are made by drawing manually or, more recently, by printing the road markings by a road marking device, for example with thermoplastic mass onto the surface of the road / asphalt.

[0006] However, modern marking machines are not capable of producing all types of road markings, or road markings for all targets. The reason is often the difficult location of the road marking to be made. The location may be difficult, for example, because the road marking cannot be painted with present devices without causing a danger to the rest of the traffic, for example, because of no or insufficient possibility to pass by. Painting the road marking may also be physically impossible because of, for example, ditches or guardrails or other physical constraints. These problems are often caused by the large size of the device used for painting road markings. Thus, for example, a road marking device mounted on a truck bed, for example a printer for printing road marking symbols onto a road, may either block the road or not physically fit at all marking targets for painting a road marking. One option for a road marking device mounted on a truck bed, i.e. a printer road marking device, is a four-wheeled road marking robot based on nozzle technique. Molten mass filled in it is kept warm in its boiler for road marking mass and is printed onto the road by the robot. Alternatively, the robot may use paint for making the road markings. The robot has a so-called parent vehicle for filling the robot with the masses or paints and beads and for transporting it to the sites to be provided with markings. Such robots can print markings in more confined spaces than marking devices mounted on truck beds. Markings suitable to be made by a robot include e.g. all symbols, also when located in confined spaces, and parking lots.

[0007] Brief summary of the invention

[0008] The invention relates to an autonomous road marking robot comprising a print head for printing road marking patterns, a method for printing road markings by a road marking robot, as well as computer program for controlling printing by a road marking robot. The invention is characterized in what is defined in the independent claims.

[0009] According to a first aspect, the invention relates to a road marking robot. The road marking robot is autonomous and arranged to move on a road. The road marking robot comprises a mass container for storing thermoplastic road marking mass and for keeping it warm, as well as a print head for printing thermoplastic mass. In addition, the road marking robot comprises communication means arranged to at least receive a location control signal, as a result from an analysis of sensor data captured on the road, for controlling the road marking robot to move to the correct printing location, and a printing control signal for controlling the printing of the road marking. The print head comprises hatches which are opened at different times during movement of the road marking robot to make the road marking as a pattern of thermoplastic mass flowing out of the hatches.

[0010] In an embodiment, the road marking robot comprises means of mobility for moving on a road. In an embodiment, the means of mobility are four separately controllable wheel units. In an embodiment, the road marking to be printed out is a raster pattern. In an embodiment, the printing control signal defines data of the road marking to be printed out. In an embodiment, the data of the printing control signal comprises data of the printing path of the road marking, the schedule of opening and the order of opening of the hatches of the road marking robot. In an embodiment, the road marking robot further comprises at least one image sensor for collecting sensor data of the road, the image data being transferred by communication means of the road marking robot to a data processing device for analysis. In an embodiment, the road marking robot further comprises at least one positioning sensor for collecting location data of the road, the location data being transferred by the communication means of the road marking robot to a data processing device for analysis. In an embodiment, the road marking robot comprises a data processing device. In an embodiment, the road marking robot further comprises a battery or a fuel aggregate. In an embodiment, the positioning sensor is a camera or a LiDAR device.

[0011] According to a second aspect, the invention relates to a method for printing out road markings by a road marking robot according to the first aspect, or an embodiment thereof. The method comprises capturing sensor data of a road; analysing the sensor data; and generating, as a result of analysing the sensor data, a location control signal for guiding the robot to the location of the road marking to be printed out, and a printing control signal for controlling the printing of the road marking.

[0012] In an embodiment, the sensor data is received from a road marking robot comprising at least one image sensor or a positioning sensor for capturing sensor data of the road. In an embodiment, the sensor data is received from a parent vehicle for the road marking robot, the parent vehicle comprising at least one image sensor or positioning sensor for collecting sensor data of the road. In an embodiment, the sensor data captured by the image sensor is analysed by a data processing device by using an algorithm for recognizing printing indications.

[0013] According to a third aspect, the invention relates to a computer program product which is stored in a computer readable medium and is executable in a data processing device, wherein the computer program product comprises instructions for printing out road markings by a method according to the second aspect or an embodiment thereof, by a road marking robot according to the first aspect or an embodiment thereof.

[0014] In the following, the invention will be described in more detail with reference to the appended drawings, in which

[0015] Fig. 1 a shows a road marking robot according to the invention in a slanted perspective view from the rear,

[0016] Fig. 1 b shows a road marking robot according to the invention in a slanted perspective view from above,

[0017] Fig. 1 c shows a road marking robot according to the invention in a slanted perspective view from the front,

[0018] Fig. 1 d shows a road marking robot according to the invention in a side view,

[0019] Fig. 2 shows a road marking robot according to the invention with a parent vehicle,

[0020] Fig. 3 shows a flow chart of a method for printing a road marking by a road marking robot according to the invention, and

[0021] Fig. 4 shows a print head, with a roll, of a road marking robot according to the invention.

[0022] Detailed description of the invention

[0023] As said, standards relating to safety at road works often require that road markings are made by a device. A road marking is a marking, such as a line or a symbol, made onto the surface of a road, asphalt, concrete, or another hard ground covering material by painting, by printing with thermoplastic mass, or in another way suitable for making a marking to be used either as such or together with traffic signs for controlling traffic. In this context, the term “road marking” or shortly merely “marking” thus covers any markings made onto the surface of a road, asphalt, concrete, or another hard ground covering material by painting, by printing with thermoplastic mass, or in another way; and the term “road” covers roads, grounds, parking lots, port areas etc. where traffic control markings may be used or needed. The aim of road markings is, among other things, to improve traffic safety, smooth traffic flow, and comfortable driving. Traffic safety is improved by road markings which are not only painted but are also reflective, particularly in dark and bad weather. Longitudinal road markings include, for example, a centre line, a lane line, a roadside edge line and an extension to an edge line, as well as a barrier line and a hazard warning line. Cross markings are marks that are crosswise to the road, belonging to so-called other markings. Cross markings include, for example, extensions to pedestrian passageways and bicycle paths, markings of speed limits and restricted zones, stop and give way lines, as well as lane arrows.

[0024] Road marking work involves a number of challenges, because the work has to be done by the road marking machine not only in the midst of traffic but also at different times of the day and in different weather conditions and also in confined areas. With large road marking devices of prior art, mounted on truck beds, it is in many cases not possible to make sufficiently sharp turns when painting e.g. line markings, whereby that part of the marking is either completely omitted or is made by marking manually. Also, when using road marking devices mounted on truck beds, similar challenges are faced when making symbol markings as with the line markings. In addition to those mentioned above, another challenge is the accurate positioning of the painting or printing of road markings in exactly the right places on the road.

[0025] A road marking machine / device suitable for even demanding road marking work is a four-wheeled autonomous road marking robot according to the invention, which prints thermoplastic road markings out of its hatches at the print head. In this context, autonomous means that the robot has no driver but the road marking robot prints out the road markings with the thermoplastic mass autonomously, separately from other vehicles, either in a self-driven way, or it can be remote controlled, for example from a so-called supporting or parent vehicle. The supporting or parent vehicle may be, for example, a truck or another suitable vehicle. This road marking robot according to the invention will be described in more detail herein below.

[0026] The road marking robot operates, i.e. moves and prints thermoplastic mass, by using electricity produced by a fuel aggregate. An alternative to the fuel aggregate is, for example, one or more batteries or a battery pack. In this context, the fuel aggregate and battery / battery pack can be called by the generic term power generating means. The robot normally has four wheel units which it uses for movement, each of them comprising e.g. at least one wheel and a hub motor or another electric motor suitable for the operation of the wheel unit, for example a shaft stepper motor. Consequently, the wheel units, and thereby also the wheels, normally have both a lifting functionality and a turning functionality. The lifting functionality may be necessary e.g. in situations where the terrain is uneven or the robot has to move over an obstacle, such as a curb. Thus, each wheel of the robot can turn and rise independently of the other wheels; that is, each wheel unit with the respective wheel is separately controllable. By means of the separately controllable wheel units and wheels, it is possible to achieve even complex paths of movement, and the robot can move even in difficult terrain. However, the wheel units may also be different from those mentioned above, as long as they are suitable for movement and transportation of the robot. The wheels are controlled by motor-drive mechanisms, and the motor-drive mechanisms are controlled by a data processing device, i.e. a computer, either by the robot’s own computer or the computer of the parent vehicle, or by an external server or a cloud server. Control signals, such as location control signals, are used for the control.

[0027] Typically, in existing road marking devices for painting thermoplastic road markings, thermoplastic road marking mass is melted from powder in mass containers in the road marking devices themselves; that is, the road marking device prepares its own thermoplastic mass in its container. For work and energy efficiency, and for the smallest possible size of the robot, the mass container for thermoplastic road marking mass on the robot according to the invention is intended to contain finished thermoplastic mass filled in the container and to keep it sufficiently warm for printing, not to prepare the mass. However, it is also possible in some cases to arrange the robot according to the invention to be suitable for preparing the thermoplastic mass instead of merely for keeping it warm. The prepared warm thermoplastic mass is filled in the mass container of the road marking robot, for example, from its parent vehicle via a pipe or the like. Normally, the parent vehicle has prepared the mass to be filled in.

[0028] The mass container comprises an inner mass space, surrounded by a heating oil jacket for maintaining the temperature of the thermoplastic mass in the mass container. The heating oil of the jacket can be heated, for example, by a diesel burner or by another heating method suitable for the purpose, such as electric resistances or, in the future, possibly by e.g. nuclear power. From the oil jacket, heat is transferred by conduction and radiation into the mass space and the thermoplastic mass contained in it. If the mass were heated directly, instead of heating the oil jacket, by e.g. a diesel burner or another heating method, this would involve the risk of burning the thermoplastic mass and rendering it unusable. Thanks to the heating via an oil jacket, the thermoplastic mass in the mass space remains sufficiently warm or at a desired temperature but does not burn. Around the heating oil jacket, an insulation layer is normally provided, contributing to the retention of heat in the oil jacket and the mass. A suitable temperature for applying, i.e. printing out, the thermoplastic mass is normally about 200°C, at which temperature the mass is also stored in the mass container. However, the temperature may deviate from this, for example according to the mass used. The mass container is normally provided with a mixer for keeping the mass homogeneous and suitable for printing. The mixer is normally driven by an electric motor. The mixer may be, for example, a kneader or another mixing means moving in a reciprocating or rotating manner in the container.

[0029] A print head is connected to the mass container of the road marking robot so that the thermoplastic mass can flow to the print head and further to be printed out as a road marking onto a road surface. The print head prints out a desired road marking, for example, a symbol, onto a desired target, i.e. the right location, on the road. The print head is normally arranged wider than the body of the road marking robot, that is, wider than the pairs of wheels placed on the sides of the body, that is, wider that two parallel wheels. This is to prevent the robot, when making markings, from driving on the markings printed out by itself, whereby the wheels and thus further the areas not intended to be marked could be stained and thermoplastic mass could enter areas where it is not intended to be applied. Depending on the body, the print head may have a width of, for example, 80 to 120 cm, if the body has a width of, for example, 60 to 100 cm. The robot normally comprises two pairs of wheels: a pair of front wheels and a pair of rear wheels.

[0030] The print head consists of the body, a roll, a screw, and hatches. The hatches are used as the nozzle for the road marking robot. Hot oil in the oil jacket for the mass container can be circulated not only in the oil jacket of the mass container but also at the print head to prevent the thermoplastic mass from cooling too much when it is transferred from the mass container to the print head, or within the print head. Excessive cooling may harden the thermoplastic mass, whereby printing of road markings is no longer possible, or it is more difficult. In other words, the thermoplastic mass flows from the mass container into the body of the print head. Within the body of the print head, a screw is provided for spreading the mass evenly, substantially over the entire area of the wide print head, to prevent a situation where mass to be printed out would not be contained or evenly distributed in the whole print head. In conventional solutions, thermoplastic material is pumped or merely poured from the mass container to the print head. However, these solutions do not distribute the mass evenly over the entire area of the print head, or at least it is difficult to pump or pour a correct amount of mass onto the entire area of the print head.

[0031] The print head is provided with printing hatches at regular intervals substantially across the whole width of the print head. The hatches of the print head may have, for example, a width of about 1 cm and / or a height of 1 cm or a diameter of 1 cm, but they may also be slightly larger or smaller. Their shape may be square, rectangular, semicircular, circular, or any shape suitable for the purpose. Their spacing may be, for example, 0.5 cm to 2 cm, or greater or smaller. By opening one or more selected hatches at a time while the road marking robot is moving, a raster pattern is created with the road marking mass onto the road. That is, when the robot proceeds along a substantially straight line forward, one or more hatches are always opened at that location of the road where mass is intended to be dropped from the open hatches, to create a desired pattern by printing. If the road marking pattern to be printed out does not have a width equal to the whole width of the print head, at least one or more of the hatches are closed. The open hatches do not need to be adjacent hatches, but hatches may be open in different parts of the print head. For example, if hatches are open at both ends and in the middle of the print head, the hatches in the sections between these are closed, and the robot moves forward, the output consists of three stripes. In other words, when the robot is moving, different hatches are opened at the respective locations of the road where a marking is to be printed out. The robot can thus make the markings as a raster pattern and not merely by, for example, turning in another direction and following the shape of the marking to be printed out. For a wider marking, the robot may drive two or more times at the marking to be made, along adjacent paths. Even more complex patterns can be made by opening hatches at such locations of the road where a marking is to be produced, by dropping mass onto the road by a desired number of hatches, by the desired hatches, and along a path of a desired length passed by the robot. However, the robot according to the invention can also be arranged not to proceed along a straight line but to follow the shape of the road marking by varying its travel direction, whereby it prints out the marking by following the road marking to be made, or its shape, such as a line marking to be made by the robot.

[0032] For levelling out pressure in the print head, the print head may contain a roll providing precise control of the quantity of the mass used for printing, that is, the quantity of thermoplastic mass to be transferred from the print head onto the road. The roll is a hollow or solid cylindrical metal part whose surface is provided with indentations, for example by machining. By the number and size of the indentations, and / or the roll speed, it is possible to adjust the quantity and texture of the mass. The indentations may also be holes, whereby the material passes through the roll.

[0033] The hatches are opened by a lever mechanism operated by an actuator according to wireless printing control from a data processing device in the parent vehicle. The actuator is thus a component which, induced by an external signal, produces a given movement. The signal may be, for example, electronic, hydraulic, or pneumatic. As an alternative to wireless control from the parent vehicle, the printing control data may also be downloaded, for example from the parent vehicle or a cloud service, into the data processing device of the robot. The lever mechanism is operated by pulling it back and forth by the actuator. The actuator may comprise, for example, one or more electromagnetic solenoids or pneumatic cylinders. The lever mechanism can thus be implemented, for example, so that an electromagnetic solenoid of the actuator moves the lever mechanism which turns the hatch to either open or closed position. Thus, the solenoid needs to generate electromagnetic power only momentarily. The momentary power generation helps to extend the service life of the solenoids and to reduce the amount of electric energy needed for printing. The actuator is powered by the power supply means of the robot.

[0034] For the aggregate and the oil burner, the robot may further comprise a fuel tank; that is, the road marking robot has a fuel tank on board. In addition to the fuel tank, the robot may comprise a battery; that is, the robot may have a battery, batteries, or a battery pack on board, to secure the reliability of the robot, for example in case of a failure of the aggregate. As already mentioned above, the road marking robot according to the invention may also comprise no aggregate; in this case, the aggregate is replaced with one or more batteries or battery packs for supplying the electricity needed by the robot.

[0035] The correct location for printing out the road marking may be indicated by marks on the road, such as small marks of paint or the like. The printing location may also be, for example, an old road marking which should be coated with a fresh printout of the road marking. These marks or old markings may be called printing indications. However, for selecting the correct printing location on the ground, physical printing indications are not necessary. Instead, the user may determine the correct printing location, so to say, manually.

[0036] To find, i.e. position, the correct location of the printing indication, that is, to align the correct printing location for the road marking to be made on the road, the road marking robot and / or the parent vehicle comprises at least one or more image sensors. In this context, the term image sensor comprises, for example, a camera, a machine vision system, a LiDaR (LightDetection and Ranging) device, i.e. an optical radar, a laser scanner, or any other sensor suitable for detecting an indication on the road. The camera may be, for example, an RGB (Red Green Blue) camera, an sRGB camera, or a CCD (Charge- Coupled Device), such as a digital camera or another ordinary photographic camera, or any other camera that produces images comparable with those of a normal camera, but in some cases the camera may also use e.g. different wavelengths or other necessary or suitable techniques for finding the location for a road marking and / or for detecting and / or positioning an old marking.

[0037] A LiDaR device is a device operating by light pulses and capturing data of a road by measuring the time between transmitting and receiving the light pulses. LiDaR devices are used for measuring distances with accurate results. Data collected by the LiDaR device is thus a relatively dense point cloud which is a 3D representation of the object scanned, in this case a road. It is also possible that the robot and / or the parent vehicle applies more than one image sensors of the above described type at a time for detecting the mark, and also e.g. an image database provided with data for each image sensor to be used for machine learning and in an algorithm for detecting the printing indications. In this context, data generated by an image sensor is called image data, and the term image sensor may comprise a camera as well as a LiDaR device. Thus, by means of sensor data acquired by the image sensor, it is possible to find out the location of a road marking to be made on a road.

[0038] Using accurate positioning technology, such as GNSS, RTK and IMU (inertial measurement unit) sensors, which are called positioning sensors in this context, and a point cloud formed by a LiDaR sensor and / or a camera sensor, the robot can also find the accurate printing location by means of digital data only. Also, the positioning sensors may be arranged in either the robot or the parent vehicle, or both. An IMU sensor is a device for measuring speed, direction and magnetism by means of an acceleration sensor, a gyroscope and a magnetometer, so that when the IMU sensor is placed in the road marking robot, for example, data can be analysed to find out the direction, actual acceleration and position of the road marking robot. The IMU sensor is used, for example, for correcting distortions in a laser scanned point cloud, and it thereby has an impact on the accuracy of the image given by the primary sensor, i.e. the LiDaR device.

[0039] Positioning sensors provide supplementary data in addition to the data generated by the image sensor / sensors; in other words, they may be so-called auxiliary sensors; preferably, the sensor data provided by them is utilized for guiding the robot to move to the exactly correct printing location. Normally, the robot comprises at least one image sensor, such as a camera or a LiDaR device, or a positioning sensor, such as an IMU sensor. The parent vehicle may comprise at least one or more image sensors, such as a camera or a LiDaR device, and possibly also one or more positioning sensors. The image sensors and positioning sensors used in the parent vehicle correspond to the image sensors and positioning sensors used in the robot.

[0040] In addition to or instead of the road marking robot, the parent vehicle may capture image data of the road to find printing indications. In many cases, the parent vehicle is more capable than the road marking robot of capturing image data efficiently, because its image sensor(s) can be placed higher up than in the robot, providing better visibility. The image sensors, such as a LiDaR device or a camera, may collect an accurate point cloud of the environment. The point cloud contains not only data of the relative coordinates of the points but also a colour value for each point, corresponding to the colour value of a pixel used in a normal image file. All the data needed for printing out the road marking can be derived from the point cloud.

[0041] The image data of the road, captured by the image sensor, or the location data obtained from the positioning sensors, i.e. the sensor data collected, is transmitted by the robot and / or the parent vehicle to a data processing device for analysis. The data processing device may be arranged in the robot, in the parent vehicle, in an external server, or in a cloud. The robot and the parent vehicle comprise the communication means needed for the transmission of data, for example a transmitter or a transceiver for transferring the data from the sensor to the data processing device in a wireless manner or via a wired connection. The data processing device comprises at least one processor, at least one memory containing a computer program code for one or more software units, and means, for example a receiver or a transceiver, for receiving the captured sensor data from an image sensor or positioning sensor in a wireless manner or via a wired connection. Several processors may also be provided, for example a general-purpose processor, a graphic processor and / or a digital signal processor (DSP), and / or several different memories may be provided, for example a volatile memory for storing data and software, and a non-volatile memory, such as a hard disk for permanent storage of data and software. The data processing device may be any data processing device suitable for analysing sensor data and for defining / processing and transmitting control data for the road marking robot, such as a data processing unit or a computer. The data processing device may be electronically connected to a sensor / sensors via signal lines, via which it may also transmit control data, such as control signals, i.e. configuration messages, to the robot and / or the sensor. The data processing device may thus be a part of the robot, i.e. an internal data processor in the robot, or it may be an external data processing device, such as a data processing device comprised in a parent vehicle, a server or a cloud server. The data may be transmitted from the robot or the parent vehicle to the data processing device over a communication network, for example a wireless local area network (WLAN), or by GSM, CDMA or WCDMA technologies, or future technologies, or other data network technologies.

[0042] The data processing device may be configured to apply a system corresponding to a face recognition system for recognizing printing indications. The system is an algorithm, taught by machine learning, which applies an image sensor and is capable of comparing image data to images in a database and of recognizing whether a trace, an image, a deviation, a marking, etc. in the image data corresponds to a printing indication in the database. An appropriate algorithm and a sufficiently large number of images of printing indications in the image database increase the probability for successful recognition of the printing indication. For a LiDaR device, for example, the database contains uploaded information on point clouds formed of different indications. Consequently, the recognition of printing indications is implemented by training the algorithm to recognize different printing indications and their different features by supplying the algorithm with sufficient data. For this, a sufficient amount of image data or other data has to be available for the system to learn to distinguish between different printing indications. The algorithms used for image recognition are based on comparing features computed from images. They compare pixel groups with each other, and when the comparison produces a sufficient recognition level, that is, the printing indication is recognized with sufficient probability as a given printing indication, the road marking robot is guided to the location defined by the printing indications to print either the road marking defined by the printing indication, or a road marking defined for the robot in another way. However, it is also possible that instead of image recognition, the user recognizes the printing indications from the image data captured by the image sensor, e.g. on a display, whereby the location for the markings can also be defined by the user; that is, the user can define the location for the road marking to be printed by the robot, for example, by setting the road marking to a correct coordinate point by means of a data processing device. Defined by the user, the location for the road marking and / or the road marking will serve the same purpose as the location for the road marking and / or the road marking recognized by machine vision. Moreover, the user can select the location for the road marking to be printed out and, if necessary, also the road marking to be printed out, for example by applying a data processing device, even without an analysis of image data. In some situations, it may also be necessary for the user to determine the location, for example when an old road marking detected by sensor data is at an incorrect location on the road and the location for the new marking to be printed out is to be changed to the correct one.

[0043] On the basis of an analysis of captured sensor data, such as image data and possibly also positioning data, movement paths are determined for the robot; that is, the robot is guided by control signals to move to the correct printing location, such as onto the printing indications. At the correct printing location, such as at the printing indication / s found by analysis, the robot passes slowly over the correct printing location, and the hatches needed for printing the road marking are instructed by printing control signals to open at the location where the road marking is printed with thermoplastic mass as a raster pattern on the road. For a wider marking, the robot passes repeatedly over the printing location by moving along adjacent paths, for example twice, three times, or as many times as are needed to complete the road marking. Here, adjacent paths mean that parts of the pattern are produced in sections: on the first pass, the robot prints out one section of the marking, and on the next pass along an adjacent line it continues printing out the marking where it ended on the first pass. Thus, the robot does not print out the road marking by following the shapes of the road marking, but the marking is formed by opening the respective hatches when moving along straight paths. However, it should be noted that in addition to or instead of straight paths, the marking can be printed out by following the shapes of the marking to be made, if this is necessary for the marking in question, for example for a wide marking to be printed out on a large area which can be produced more efficiently by following the shapes of the marking, such as a large island at a crossing; or if this is otherwise sensible in view of the circumstances, for example to go around a barrier formed by curbs at an intersection and to print out the marking by following the edge of the curb.

[0044] In addition to monitoring the printing indications on the road, the parent vehicle fills the road marking robot with thermoplastic marking material melted from powder and ready to use. The filling can be done, for example, as follows: when the road marking robot is taken on board the parent vehicle, for example on a rack at the front of the vehicle, which rack may correspond to e.g. the fork of a forklift, the robot can be filled with thermoplastic mass and possibly beads. The robot can also be transported by means of the rack of the vehicle to the next location where a road marking is needed.

[0045] On top of a road marking, such as a symbol, printed out on the road, for example glass beads can be applied, so that the marking is reflected in headlights of vehicles. A bead container may be provided on top of the print head and filled with glass beads. By gravity, the glass beads sink to the bottom of the bead container, from where the beads pour out on top of the symbol printed out. The number of dropping beads can be limited and levelled out by a rotating roller arranged inside the bead container, at the outlet of the container. The application of beads can be limited by letting out beads in the width direction merely on top of the symbol printed out, by simple hatches of the bead container.

[0046] In the solution according to the invention, sensor data, i.e. image data, on the road is acquired / captured by the image sensor / s of the road marking robot and / or the parent vehicle; the sensor data, e.g. image data, is analysed, for example, by machine learning based algorithm / s for recognizing printing indications, i.e. by artificial intelligence (Al), utilising a database that contains a sufficient amount of stored data for the respective image sensor to be used for teaching the algorithm as well as for recognizing the printing location defined by the printing indications; and the marking intended for the road is printed out by the robot by passing along at least one straight or relatively straight path over the location of the printing indication. The road marking to be printed out may be defined for the robot in advance, or it can be defined, for example, by a configuration message or another suitable method of transmitting information after the previous pattern has been printed out or after the location for the road marking to be printed out next, i.e. the road marking location, has been found in image data or in digital printing points defined by the user. It is also possible that the printing indication / s detected in the image data define the road marking intended to be printed by the robot; that is, the road marking intended to be printed out is recognized in image data and is defined for the robot, for example, by a configuration message or another suitable method of transmitting information. It is also possible to supply the robot with the data of several symbols, i.e. a group of symbols, to be printed out next, whereby the robot can print out several symbols smoothly one after another. The printing paths can be adjusted more precisely in real time according to the positioning of the robot. The positioning data of the robot are obtained, for example, from data which is captured by the robot’s IMU sensor and which the robot can transmit by its communication means to a data processing device either at regular intervals or upon a request for data by the data processing device, or when the robot detects a deviation of at least predetermined magnitude from normal data values in the data captured by its IMU sensors.

[0047] Figure 1 a shows a road marking robot 100 according to the invention in a slanted perspective view from the rear. The robot 100 is a four-wheeled autonomous road marking robot for printing out thermoplastic road markings on the surface of a road. The road marking robot 100 is driven by electricity which is produced by a fuel aggregate 101 running on fuel, such as diesel oil, for which a separate fuel container (not shown) is provided in the robot. An oil burner (not shown) is also driven by electricity produced by the fuel aggregate 101 or, for example, by fuel pumped out from the fuel container. The robot 100 also comprises an image sensor 110 for capturing sensor data, i.e. image data, on the road, and communication means 111 for transmitting the image data to a data processing device 112 for analysis and for receiving control data, i.e. control signals, from the data processing device 112. The image sensor 110 may be, for example, a LiDaR device or a camera for generating a point cloud of the road. This road marking robot 100 thus comprises its own image sensor 110 and data processing device 112. The image data of the road, captured by the image sensor 110, is analysed and processed by the data processing device 112 to detect the data needed for making the road marking. The data to be detected from the image data may be, for example, location data for the road markings to be printed out. From the location data, movement paths are calculated for the robot to move to the correct printing location, and transmitted as control signals to the robot, for example in a file format. The movement paths correspond to paths computed for e.g. / 3D printer or CNC machines. Here, the file format may be G code, for example. The file format may be different as well, and alternatively, the movement paths may also be sent as separate signals, commands, or configuration messages. When printing markings, the robot 100 may also change its movement paths in real time on the basis of data obtained from one or more of its sensors, such as the positioning sensor 113 of the robot 100. The positioning sensor 113 may be, e.g. an IMU sensor. Similarly, the sensor data of the positioning sensor 113 can be transferred to the data processing device 112 for analysis, and as a result of the analysis, the robot 100 can receive control data, for example a new location control signal, from the data processing device 112.

[0048] In other words, if, as a result of analysis of the image data, at least one item of location data of a road marking to be printed out is detected and recognized, then at least one control signal for controlling the operation of the robot 100 is transmitted, for guiding the robot 100 to the correct printing location on the road. This control signal can be called a location control signal. In an alternative, the location control signal is transmitted on the basis of a digitally positioned road marking, instead of location data obtained from image data. In addition to the location control signal, a printing control signal can be transmitted to the robot, comprising information on the printing path for the robot, i.e. the movement paths during printing, the schedule and order of opening of the hatches, that is, which hatch is opened and at what time when the robot 100 is moving along its printing path. It is also possible that the printing control signal has been sent to the robot in advance. Or, the data of the printing indication, corresponding to the printing control signals, i.e. the data of the printing path, the schedule and order of opening of the hatches, may have been defined in advance and stored in the robot 100, whereby only the road marking to be printed out is defined by the printing control signal. Or, the marking to be printed out is detected from the image data, in addition to the location data, and the printing control signal is transmitted on the basis of the image data, in addition to the location control signal.

[0049] The robot 100 comprises four wheel units 102, each comprising at least one wheel 103 and an in-wheel motor, i.e. a hub motor. The wheels 103 may have both a lifting functionality and a turning functionality. The wheels are controlled by motor controllers, and the motor controllers are controlled by a data processing device, i.e. a computer, which transmits control signals for the wheel unit 102 to the motor controllers. Each wheel 103 of the robot 100 can be controlled to turn or rise independently of the other wheels 103.

[0050] Instead of using the robot’s 100 own data processing device 112, it is possible to process, i.e. analyse, the sensor data, such as image data, by a data processing device outside the robot 100, such as a data processing device in the parent vehicle, or by an external server or cloud server. Similarly, image data can be captured by one or more image sensors of the parent vehicle, in addition to or instead of the image sensor of the robot 100. The data processing device 112, either belonging to the robot 100 itself or being outside the robot 100, comprises at least one processor; at least one memory containing a computer program code for one or more software units for running an algorithm for recognizing a printing indication; and means for receiving image data from the camera 110 of the robot 100, for example a receiver or a transceiver; and means for transmitting control data, i.e. control signals, to the robot, i.e. for determining the correct location of a road marking and possibly also the correct road marking, for example a transmitter or a transceiver. Several processors may be provided, for example a general-purpose processor and a graphic processor and a digital signal processor (DSP); and / or several different memories may be provided, for example a volatile memory and a non-volatile memory, such as a hard disk for permanent storage of data and software. The locations for the image sensor 110, the communication means 111 , the positioning sensor 113, and the data processing device 112 in the robot 100 can be selected as desired.

[0051] Moreover, the robot 100 comprises a mass container 105 for thermoplastic mass. The inner mass space of the mass container 105 is for the thermoplastic mass. Around the mass space, a heating oil jacket is provided for keeping the mass warm. An insulation layer is provided around the heating oil jacket. The heating oil jacket is kept warm by an oil burner (not shown) which can be connected to the electrical power supply of the fuel aggregate 101 , or it may be battery-operated as well.

[0052] A print head 106 is connected to the mass container of the road marking robot 100, for printing out the road marking, for example a symbol, defined by a printing control signal, via its openable hatches 107 to a target defined by a location control signal on the road, i.e. at a correct location on the road. The parts and the operation of the print head 106 have been described in a previous section in this text. The reference numeral 109 depicts an actuator for opening the hatches 107, which actuator may be, for example, one or more electromagnetic solenoids or air cylinders. The roll, i.e. cylinder (not shown), provided with machined indentations, is contained in the print head 106. By the number of indentations in the roll, and the rotation speed of the roll, it is possible to adjust the quantity and texture of the thermoplastic mass running i.e. being printed out from the hatches 107.

[0053] Figure 1 b shows a road marking robot 120 according to the invention in a slanted perspective view from above. The robot 120 corresponds to the road marking robot 100 of Fig. 1 a in other respects except that it does not have its own data processing device for analysing sensor data, but the data is transmitted to an external data processing device 132 for analysis. The data processing device may be located in the parent vehicle or even outside the parent vehicle. The robot 120 comprises communication means 131 , an image sensor 130, a positioning sensor 133, a print head 126, wheel units 122 with wheels 123, the print head 126 with hatches 127 and actuators 129, and a mass container 125, The data processing device 132 comprises communication means 133 for receiving sensor data from the sensors 130 and 133 and for transmitting control signals to the robot 120. The road marking robot 120 runs on electricity which is generated by a fuel aggregate 121. The sensor data itself is analysed in a way similar to the case of the robot 100 in Fig. 1 a. The robot 120 is also controlled in the same way as the robot 100.

[0054] Figure 1 c shows a road marking robot 140 according to the invention in a slanted perspective view from the rear. The robot 140 corresponds to the road marking robots 100 and 120 of Figs. 1 a and 1 b in other respects but it does not have an image sensor nor a data processing device of its own. The robot 140 has communication means 141 , wheel units 142 with wheels 143, a print head 148 with hatches 147 and actuators 149, and a mass container 145. The robot 140 receives control signals, such as a location control signal and a printing control signal, for controlling its movement and printing from an external data processing device 144a which receives the image data from the image sensors 144b of the parent vehicle which may comprise one or more sensors, and analyses the image data. The robot 140 also comprises a positioning sensor, for example an IMU sensor (not shown), so that its paths can be changed during printing, based on data obtained from the positioning sensor. Similarly, the sensor data of the positioning sensor can be transferred to the data processing device 144a for analysis, and as a result of the analysis, the robot 140 can receive a position control signal from the data processing device 144a.

[0055] Figure 1 d shows a side view of a road marking robot 150 according to the invention. The road marking robot 150 runs on electricity stored in a battery pack 156. The robot 150 comprises communication means 151 , an image sensor 160, wheel units 152 with wheels 153, a print head 158 with hatches 157 and actuators 159, and a mass container 155. The robot 150 receives control signals from an external cloud service 154a which obtains image data from the image sensors 154b of a parent vehicle which may comprise one or more image sensors, and from the robot 150, and analyses the image data. This road marking robot 150 also comprises a positioning sensor 161.

[0056] Thus, the road marking robot may or may not comprise an image sensor (sensors) and / or a positioning sensor (sensors) and / or a data processing device, and / or a battery, and / or a fuel aggregate. The robot is supplied with electricity from a fuel aggregate or a battery, or both if it comprises both.

[0057] In other words, the image data from the image sensor or sensors and the positioning data from the positioning sensor or sensors are processed by a data processing device which may be placed in, for example, the road marking robot, the parent vehicle, an external server or cloud service; and data needed for printing of road markings, for example location data of the road markings to be printed out, are extracted from the sensor data by analysis. From the location data, it is possible to calculate the paths for the robot, these paths being transmitted to the robot. The paths may be transmitted in a file format or also in the form of separate signals or commands. The data to be transmitted is transmitted by an existing wireless communication protocol, for example 4G or WiFi, or a protocol that will be introduced in the future. When printing out markings in real time, the robot may also change its paths on the basis of data obtained from the sensors of the robot. If necessary, all this processing may also be carried out by processors in the robot, so that the robot may, in some situations, operate independently of the parent vehicle. If needed, however, the analysis of the image data can be made by the user in addition to or instead of the data processing device.

[0058] Figure 2 shows a road marking robot 200 according to the invention, and a parent vehicle 201 . By at least one image sensor 202, the image sensor 202 being a camera in this embodiment, the parent vehicle 201 has collected image data of the road, i.e. it has captured the road and analysed the image data with the printing indication recognition algorithm of its data processing device

[0059] 203. After detecting and recognizing a printing indication in the image data, which in this case means that the robot 200 should print out yield signs 204 consisting of parallel triangles at the location of the printing indication 206, the data processing device 203 applies communication means 207 to transmit the necessary control signals to the road marking robot 200 which also comprises communication means. A location control signal guides the road marking robot 200 to move to / onto the printing indication 206, and a printing control signal controls the movements and hatches of the robot 200 so that the robot 200 will move across the road 205 along a substantially straight line; and the triangles of the yield signs 204 will be printed out as a raster pattern when the robot 200 proceeds to the correct location on the road, the respective hatches of the robot 200 opening and dropping thermoplastic mass onto the road, which hatches are needed to print out the respective section / part of the yield sign

[0060] 204. In Fig. 2, most of the road marking, i.e. the yield signs 204, has already been printed out. The printing indications 206 for only one triangle of the yield signs 204 to be printed out are left visible.

[0061] Figure 3 shows a flow chart of a printing method 30 for a road marking robot according to an embodiment of the invention, i.e. a method for printing out road markings by a road marking robot according to the invention. In a first step, step 31 , sensor data of the road is received by e.g. an image sensor. In step 32, the received sensor data is analysed by a data processing device in, for example, the robot, the parent vehicle, a cloud server, or another external server. In step 33, the analysis of the sensor data results in generating a location control signal for guiding the robot to the location of the road marking to be printed out, and a printing control signal for controlling the printing of the road marking to be printed out. The type of the control signals may be any signals / messages suitable for controlling the operation and movement of the road marking robot; they can be transmitted in, for example, a stream, a package or a file.

[0062] Figure 4 shows a print head 400 of a road marking robot according to the invention. The print head 400 comprises a roll 401 and hatches 402. The roll 401 is contained in the print head 400. Some of the hatches 402 of the print head 400, in the lower part of the print head 400, below the roll 401 , are also shown. Indentations 403 machined in the roll 401 are visible as well. The size and shape of the indentations 403 in the roll 401 may also be different from those shown in the figure. By their size and / or shape, in addition to the rotation speed of the roll 401 , it is possible to adjust the amount and texture of the thermoplastic mass running from the hatches 402, i.e. being printed out. It is also possible that the indentations 403 have mutually different sizes and shapes.

[0063] The features of the invention described and the embodiments mentioned in the application are freely combinable and interchangeable, except if the application particularly states that the embodiments or features are not interchangeable. The exemplary features described in connection with the different embodiments can be used with any other embodiment even if this were not mentioned separately.

Claims

Claims:

1. A road marking robot, which road marking robot is autonomous and arranged to move on a road without a driver and independently of other vehicles, and which road marking robot comprises a mass container for storing thermoplastic road marking mass and for keeping it warm, and a print head for printing out thermoplastic mass; the road marking robot further comprises communication means arranged to receive, as a result of analysis of sensor data captured from the road, a location control signal for guiding the road marking robot to move to the correct location for printing out, and a printing control signal for controlling the printing out of a road marking, and the print head comprising several adjacent hatches, which adjacent hatches are opened at different times during movement of the road marking robot to make a road marking as a pattern of thermoplastic mass running from the hatches.

2. The road marking robot according to claim 1 , which road marking robot comprises means of mobility for moving on a road.

3. The road marking robot according to claim 2, wherein the means of mobility are four separately controllable wheel units.

4. The road marking robot according to any of the preceding claims, wherein opening of adjacent hatches at different times during movement of the road marking robot prints out a road marking as a raster pattern.

5. The road marking robot according to any of the preceding claims, wherein the printing control signal defines data of the road marking to be printed out.

6. The road marking robot according to any of the preceding claims 1 to 4, wherein the data of the printing control signal comprises data of the printing- out path of the road marking, the schedule of opening and the order of opening of the hatches of the road marking robot.

7. The road marking robot according to any of the preceding claims, which further comprises at least one image sensor for capturing sensor data of the road, the image data being transferred by communication means of the road marking robot to a data processing device for analysis.

8. The road marking robot according to any of the preceding claims, which further comprises at least one positioning sensor for capturing location data of the road, the location data being transferred by the communication means of the road marking robot to the data processing device for analysis.

9. The road marking robot according to any of the preceding claims, wherein the road marking robot comprises a data processing device.

10. The road marking robot according to any of the preceding claims, wherein the road marking robot further comprises a battery or a fuel aggregate.11 . The road marking robot according to any of the preceding claims, wherein the positioning sensor is a camera or a LiDaR device.

12. A method for printing out road markings by a road marking robot according to any of claims 1 to 11 , the method comprising capturing sensor data of a road; analysing the sensor data; and generating, as a result of analysing the sensor data, a location control signal for guiding the robot to the location of the road marking to be printed out, and a printing control signal for controlling the printing out of the road marking.

13. The method according to claim 12, wherein the sensor data is received from a road marking robot comprising at least one image sensor or a positioning sensor for capturing sensor data of the road.

14. The method according to claim 12 or 13, wherein the sensor data is received from a parent vehicle for the road marking robot, the parent vehiclecomprising at least one image sensor or positioning sensor for capturing sensor data of the road.

15. In an embodiment, the sensor data captured by the image sensor is ana- lysed by a data processing device using an algorithm for recognizing printing indications.

16. A computer program product which is stored in a computer readable medium and is executable in a data processing device, wherein the computer program product comprises instructions which make a road marking robot according to any of the claims 1 to 11 execute a method for printing out a road marking according to any of the claims 12 to 15.

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