GB2623484A - Apparatus, system and method for ground markings for autonomous vehicle navigation and other uses - Google Patents

Abstract

Methods and system for encoding and decoding machine-readable information on a ground marking on a ground surface are provided. A method for encoding machine-readable information on a ground marking comprises converting the machine-readable information into print instructions; and controlling a print head to deposit a molten plastics material 110a in discrete droplets to the ground surface and applying retroreflective particles 210 to the molten plastics material based on print instructions. A method for decoding machine-readable information on a ground marking comprises emitting light 1215 on the ground marking on the ground surface 120, capturing an image 1220 of the reflected light from retroreflective particles in the ground marking, and converting the image of the reflective light into the machine-readable information. The machine-readable information may provide information to autonomous vehicle systems and for autonomous vehicle navigation. The method may comprise up the machine-readable information into printable segments, wherein each printable segment has a corresponding print instruction. The retroreflective particles may be arranged in a machine-readable pattern. The print instructions may comprise a set of distinguishable symbols. The distinguishable symbols are formed by the arrangement of the retroreflective particles in the print instructions.

Description

APPARATUS,SYSTEM AND METHOD FOR GROUND MARKINGS FOR

AUTONOMOUS VEHICLE NAVIGATION AND OTHER USES

[0001] This invention relates to encoding and decoding machine-readable information on a ground marking on a ground surface, particularly, but not exclusively, for the purpose of providing information to autonomous vehicle systems and for autonomous vehicle navigation.

SUMMARY

[0002] Road and playground markings are applied by a variety of methods, which typically include painting. For example, white or yellow lines on roads, car park markings, and yellow paint step edges. For improved durability, thermoplastic strips or sheets are fused to tarmac or concrete surfaces by heat from gas torches to permanently mark, for example, car parks, roads, cycleways, airports, playgrounds, and the like. Thermoplastics are for hard-wearing, quick and easily applied surface marking solutions. Glass microbeads may also be applied to provide retro-reflectivity, these being applied to the thermoplastic strips while still molten, after any other particles (such as those to improve slid resistance) and when the surface temperature is lower.

[0003] Ground markings convey information to drivers and pedestrians alike by providing visible, reflective and/or tactile surfaces that serve as indicia upon a traffic surface. In the past such a function was typically accomplished by painting a traffic surface or laying premade signage that is melted into the ground. A problem with pre-loaded retroref I ective particles in such strip or sheet is that on gas torch application the particles sink into the plastic, and more must be spread on top while the material is molten.

[0004] Many technologies are now being made 'smart_. Intelligence, either passive or active intelligence, is being added to devices and surfaces to provide users with data. A ctive intelligence requires some computation unit which is impractical for ground markings.

Passive intelligence requires embedding information into a surface or an image, either inconspicuously or conspicuously, which would be appropriate for ground markings. This could be achieved with the retroreflective particles that are applied to the surface of the ground markings. Therefore, to add some passive intelligence to ground markings, e.g., machine-readable information and data, a controlled application of retroreflective particles to ground mark i ngs would be required.

[0005] Document E P2280370 describes a method of embedding machine-readable information on a substrate, including converti ng the information to machine-readable code format and writing the machine-readable code format on the substrate with at least one fluorescent marking material. Document E P2280370 does not disclose ground markings, thermoplasti c materials, or retrorefl ective particles; it discusses fluorescent inks on a paper substrate. Document J P2006070466 describes a method for printing a pattern on a surface of the pavement the method comprises laying down, on an asphalt surface, a primer layer, followed by an ink-jet printed image layer, then a surface protective layer, for decorating the surface of pavement such as a footpath, carriageway or cycle track. The possible solution disclosed in J P2006070466 lacks durability and requires an additional surface protective layer and does not involve hardening plastic material or the deposition of retroreflective particles. Document CA2836558 describes a method for forming and applying retroreflective pavement markings comprising spraying the area with a hot epoxy binder, depositing particles of a mi crocrystal line ceramic element having a high refractive index onto the fresh epoxy binder, depositing relatively large spherical glass beads onto the fresh epoxy binder, and depositing relatively small spherical glass beads onto the fresh epoxy binder. However, CA2836558 does not describe arranging the retroreflective particles in such a manner to encode information or some passive intelligence into the ground markings.

[0006] The present invention provides novel methods and systems for encoding and decoding machine-readable information on a ground marking on a ground surface that also have advantages over the conventional methods described above. A first aspect of the invention provides a method for encoding machine-readable information on a ground marking applied to a ground surface. The method comprises converting the machine-readable i nformati on into one or more print instructions, control Ii ng a print head to deposit a plurality of discrete droplets of molten plasti c material on to the ground surface and apply retroreflective particles to the molten plastic material based on the one or more print instructions.

[0007] In some examples, the method further comprises breaking up the machine-readable information into printable segments, wherein each printable segment has a corresponding print instruction.

[0008] In some examples, wherein the discrete droplets harden into a durable ground marking. In some examples, the discrete droplets and retroreflective particles are applied in layers, each layer having different retroreflective properties configurable to comprise different machi ne-readable i nformati on.

[0009] In some examples, the method further comprises receiving an image, converting the image into print i nstructi ons, and wherein the plurality of discrete droplets of molten plastic material is deposited based on the one or more print instructions to form the image.

[0010] In some examples, the retroreflective particles are comprised of at least two types of retroreflective panicles. In some examples, a first retroreflective particle is activated by a first wavelength of light, and a second retroreflective particle is activated by a second wavelength of light [0011] In some examples, the printable segments comprise a set of distinguishable symbols comprising a first symbol for encoding:zeros-and a second symbol for encoding:ones-.

In some examples, the distinguishable symbols are formed by the arrangement of the retroreflective particles in the one or more print instructions. In some examples, the retroref I ective particles are arranged in a machine-readable pattern.

[0012] In some examples, the machine-readable information is at least one of: navigation data, road boundary information, direction information, parking i nformati on, parking guidance data, autonomous driving instructions, hazard information, ground surface data, instructions for an autonomous vehicle, contextual information, or point of interest information. In some examples, the discrete droplets harden into a durable ground marking.

[0013] A second aspect of the invention provides an autonomous printing device comprising a print head comprising a plurality of nozzles configured to deposit a molten plastics material and apply retroreflective particles to a ground surface, and a controller operable to carry out the methods of the first aspect of the invention.

[0014] A third aspect of the invention provides a method for decoding machine-readable information on a ground marking applied to a ground surface The method comprises emitting light on the ground marking on the ground surface, wherein the ground marking comprises retroreflective particles, acquiring at least one image of the reflected light from the retroreflective particles, and converting the image of the reflected light into machine-readable information.

[0015] In some examples, the emitted light is emitted at a first wavelength. In some examples, the method further comprises filtering the image to select the first wavelength and rejecting other wavelengths to reveal a pattern from the image.

[0016] In some examples, the discrete droplets and retroreflective particles are applied in layers, each layer having different retroreflective properties configurable to comprise different machine-readable information. Accordingly, in some examples, the retroreflective particles are comprised of at least two types of retroreflective particles. In some examples, a first retroreflective particle is activated by a first wavelength of light, and a second retroreflective particle is activated by a second wavelength of light [0017] In some exarnpl es, the machine-readable information is at least one of: navigation data, road boundary information, direction information, parking information, parking guidance data, autonomous driving instructions, hazard information, ground surface data, i nstructions for an autonomous vehicle, contextual information, or point of interest information.

[0018] In some examples, the retroreflective particles are arranged into sets of distinguishable symbols comprising a first symbol for encoding zeros and a second symbol for encoding ones.

[0019] In some examples, the retroreflective particles are arranged in a machine-readable pattern.

[0020] In a fourth aspect of the invention, there is provided an autonomous vehicle. The autonomous vehicle comprises a light source configured to emit light on a ground surface, a camera to capture an image of a ground marking on the ground surface, and a controller operable to carry out the methods of the third aspect [0021] Coded visible or machine-readable markings, which may include retroreflective materials, such as glass beads, magnetic particles, ceramic particles, or the like that can be used for guidance for pedestrian or vehicular traffic. Retro-reflective beads may simulate caLs-eyes in road markings, for example, or appear as coded symbols waming of hazards or defining a route which an autopilot system may follow. Rather than having multiple identical such markings, as is necessary with conventional cat-s eyes, which are mass produced, :custom-markings are made possible that can indicate distance from hazards such as road junctions, road boundaries, SOS zones, and the like.

[0022] An advantage of the application technique of the present disclosures over the conventional gas torch application is that information can be embedded/encoded with an accuracy for machine-readable capturing and decoding. Furthermore, gas torch appl i cation is only applicable for outdoor concrete or tarmac, while the present printing techniques work on a wider van eW of surfaces including wood and composite surfaces, as well as indoor surfaces, for warehouses and the like that comprise autonomous vehicles.

[0023] Each of the various aspects of the invention, as described above, are herein compatible with each other various aspect in any combination. Whilst the benefits of the systems and methods may be described by reference to asphalt concrete, it is understood that the benefits of the present disclosure are not limited to this specific type of blacktop_ and other such types of composite materials commonly used to surface roads, parking lots, airports, and the surfaces of playgrounds would also benefit from the present disclosures.

[0024] These examples and other aspects of the disclosure will be apparent and elucidated with reference to the example(s) described hereinafter. It should also be appreciated that particular combinations of the various examples and features described above and below are often illustrative and any other possible combination of such examples and features is also intended, notwithstanding those combinations that are clearly intended as mutually exclusive.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and other objects and advantages of the disclosures herein will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which: [0026] FIG. 1 illustrates a cross-section through a three-layer ground marking on a surface, in accordance with at least one of the examples descri bed herein; [0027] FIG. 2 illustrates retroreflective particles arranged in a machine-readable pattern, in accordance with at least of the examples described herein; [0028] FIG. 3 illustrates a cross-section of retroreflective particles arranged in a machine-readable pattern, in accordance with at least of the examples described herein; [0029] FIG. 4 shows an area of print in close-up, in accordance with at least one of the examples described herein; [0030] FIG. 5 shows a line printer arrangement, in accordance with at least one of the examples described herein; [0031] FIG. 6 is a diagrammatic plan view of one embodiment of ground marking apparatus, in accordance with at least one of the examples described herein; [0032] FIG. 7 is a front elevation of the apparatus of Figure 3, in accordance with at least one of the examples described herein; [0033] FIG. 8 is a diagrammatic view of another embodiment of ground marking apparatus, in accordance with at least one of the examples described herein; [0034] FIGS. 9A-9D illustrate components on a print head of a device suitable for ground marking, in accordance with at least one of the examples described herein; [0035] FIG. 10 is a schematic diagram of an Exemplary apparatus for applying ground markings, in accordance with at least one of the examples described herein; [0036] FIG. 11 is a schematic diagram of an exemplary autonomous system for applying ground markings, in accordance with at least one of the examples described herein; [0037] FIG. 12 is a schematic diagram of an exemplary autonomous system for decoding machine-readable information on ground markings, in accordance with at least one of the examples described herein; and [0038] FIG. 13 illustrates a block diagram of a computing module, in accordance with at least one of the examples described herein.

The present techniques will be described more fully hereinafter with reference to the accompanying drawings. Like numbers refer to like elements throughout. Paris of the autonomous ground printer are not necessarily to scale and may just be representative of components of the ground print machines, or other described entities.

DETAIL DESCRIPTION

[0039] The appropriate choice of surface course material plays a key role in providing road markings that are safe, meet the needs of the user, and offer good value for money. A mixture of glass beads, pigments, binder, and filler materials, and commonly a thermoplastic are ubiquitous materials in the field of ground markings. Thermoplastics, as their name suggests, become liquid when heat is applied and are a popular choice due to being an environmentally and user-safe compound. Generally, glass beads provide the retro-reflectivity necessary for visualising ground markings during darkness; pigments provide desired colours and opacity; binders are a mixture of plasticizer and resins that provide toughness, flexibility, and bond strength while holding all the components together, and fillers, such as calcium carbonate, sand and/or other inert substances, provide bulk.

[0040] There are two basic types of thermoplastic available. The two, hydrocarbon and alkyd, take their names from their binder types. Hydrocarbon thermoplastic is made from petroleum-derived resins. Hydrocarbon tends to be more heat stable, with more predictable application properties, than alkyd. Because it tends to break down under oil drippings and other automobile contaminants, hydrocarbon is recommended for long-line, skip lines and edge-line applications and not for high-traffic areas where cars are stationary (e.g., stop bars, crosswalks, turn arrows, and the like).

[0041] Alkyd thermoplastic is made from wood-derived resins that are resistant to petroleum products. Al kyd thermoplastic exhibits some advantages over hydrocarbon materials such as higher retroref I ective values; being oil impervious; and higher durability.

Al kyd is recommended for inner-city markings and other high-traffic areas where petroleum drippings are common.

[0042] Both hydrocarbon and alkyd thermoplastics are available in granular or block form. Hot applied thermoplastic is prepared for road application in a melting kettle where the granular or block material is introduced and heated until it liquefies at temperatures exceeding 4000F. An agitator blends the ingredients until thermoplastic is transferred into a screed, ribbon or spray device where it is then shaped into its specified width and thickness as a line, legend or symbol; in the art, this is where a large amount of variation and waste is generated as the skill of the user at application is paramount Retroreflective particles and anti-slip material are immediately applied and sink into the molten thermoplastic material. When applied on asphaltic surfaces, thermoplastic material develops a thermal bond via heat-fusion. When applied on Portland Concrete Cement and on oxidized or aged asphaltic surfaces, and a recommended sealer is properly applied, a tenacious mechanical bond is achieved.

[0043] Providing that all necessary conditions are met concerning the temperature of material and substrate, absence of moisture, road preparation and minimum thickness, excel lent performance can be achieved using thermoplastic pavement marking compounds. Typical performance life ranges from 4 to 8 years depending on roadway conditions. However, currently, there is a great deal of subjective assessment from the installers of previous ground markings. Quantifying values (such as thickness and surface friction values) and preparing surfaces accordingly, leads to more controller application of ground markings.

[0044] FIG. 1 illustrates a cross-section through a three-layer ground marking on a surface, in accordance with at least one of the examples described herein. As mentioned above, conventionally, ground markings are created by fusing plastic strip or sheet material to a ground surface 120 using a gas torch. The markings are pre-cut to size and shape and laid in position prior to fusing to the ground. Once fused, the plastic surface hardens, and the material is then very difficult to remove. So exact placement is essential. During the fusi ng operation, anti-slip or anti-skid particles are cast onto the molten plastic surface and become embedded. If retro-reflectivity is required, glass microbeacls are scattered after the particles when the plastic has cooled by some amount. judging how much material to scatter and when calls for expertise and experience and can lead to the markings needing remelting, or being wasted, if not done correctly.

[0045] The method of the present invention can use the same plastic material as is currently applied conventionally. However, it is not necessary to supply the material in strip or sheet form. One example method corrprises depositing a molten plastics material 110 at a target position on a ground surface 120, wherein the molten plastics material hardens into a durable ground marking. In some examples, the molten plastic material 110 is deposited in discrete droplets 105. In some examples, the method further comprises controlling a print head (e.g., print head 800 of FIG. 8) to form the discrete droplets into a patterned ground marking. In some examples, the patterned ground marking is obtained by layering the discrete droplets at the target position into a plurality of layers 110A-C.

[0046] In some examples, the discrete droplets are layered to a threshold thickness. In some further examples, the threshold thickness is 2mm In some examples, the step of depositing the first molten plastics material further comprises projecting the discrete droplets at a first velocity. In some examples, the method further comprises depositing a second molten plastics material in discrete droplets on the ground surface, the second molten plastics material having at least one characteristic which is different to at least one characteristic of the first molten plastic material. The second molten plastics material may be layered on top of the first molten plastics material. For example, the bottommost layer, in contact with the ground surface, may be a hydrocarbon-based thermoplastic, which is more heat stable and therefore easier to apply to the ground surface and ensure good bonding. However, because hydrocarbon thermoplastics tend to break down under oil drippings and other automobile contaminants, the second (and indeed subsequent layers) 110A-B may be an alkyd-based thermoplasti c, that is applied after the first layer has cooled. Using both thermoplasti c types is avoided in the current art as the risk of cross-contamination of the hydrocarbon and alkyd is high and the different types of thermoplastics must be kept separate (i.e., separate kettles, applicators, etc.).

[0047] The layers of the molten thermoplastics material 110 may each have different characteristics, such as, brittleness, opacity, electrical resistance, heat resistance, stress and 30 strain characteristics, acidic resistance, oil resistance, or colour. Anti-skid and retroreflective particles are applied to the top-most layer, 110A.

[0048] Temperature is the most important factor in the proper mixing, melting and bonding of thermoplastic. Heated to a temperature between 400 and 440 F and agitated properly, the thermoplastic compound becomes a homogenized liquid. Applied at this temperature, the thermoplastic me113 into the upper surface of the asphalt formi ng a thermal bond. When installed on porous surfaces, such as open-graded asphalt or tined concrete, the hot liquid thermoplastic fills all voids, creating a good mechanical lock on concrete. The thickness of the applied thermoplastic should be as specified. A mini mum thi ckness of around 2mm (90 mils) is i rnportant to the material "s ability to hold the heat necessary for good bonding. The thermal bonding that occurs when the application is at the proper thickness ensures the thermoplasti Cs durability and long-term retro-reflectivity. A minimum thickness of around 0.75mm (30 mils) is required to hold the heat necessary for proper bonding when recapping a line because of poor reflectivity or inadequate thickness The discrete droplet 105 mini rum thickness may be in the order of 0.75mm.

[0049] In some examples, the layers 110A -C of the discrete droplets overlap to create beveled, chamfered and/or rounded edges after hardening. For example, the edge discrete droplets 105 are layered within the boundary of the discrete droplet 105 of a layer below. A chamfered edge provides a nurnber of advantages, in particular around trip hazards. In the art, if the thickness of the ground marking approaches 4-6mrn, pedestrians are Ii kely to trip. Chamfered edges help to mitigate that risk. In addition, chamfered edges reduce the impact from foot or vehicular traffic, and aid in the durability of the ground marking. At 2mm thick, a marking edge would not represent a trip hazard, but a chamfered or rounded edge may be less liable to damage from foot or vehicular traffic. A thickness of 2mm is adequate for most purposes, depending on the properties of the plastic. However, compared to the methods of applying plastic conventionally with gas torches, 2mm is a very adequate thickness, and this represents a material saving over the conventional gas torch application, which requires the plastic to be thicker, often in the order of 4mrn to 4.5mm, in order not to bubble during application (overheating),In some examples, the molten plastics material is deposited in discrete droplets 105, that overlap with each other in the same layer 110A-C. Overlapping in this way creates a surface texture when the molten plastics material hardens into the durable ground marking, aiding in anti-slip properties or adding in 'rumble_ effects when driven over by a car.

[0050] Typically, the marking will be created in monotone (e.g., white lane marking in roads or yellow parking control lines), however, multiple colours are possible using the present invention and al low for patterning or for the creation of artistic or uti lily marki ngs, as in the application of promotional or warning signs, lettering or symbols to steps and other ground markings. This can be done by laying a foundation layer 110C having one colour topped with a layer or layers 110A-B of a different colour or colours in a design.

The foundation layer 110C may show through the topping layer or layers 110A-B in the fashion of a stencil, or the topping layer may cover the whole of the foundation layer, or each colour may be built up in a block from the ground up, all to be level at the surface, without art' single colour foundation layer. FIG. 1 shows discrete droplets 105 building up layer on layer, with the surface layer 110A differently coloured to the lower layers 110B-C.

[0051] Desirably, the plastics material as laid will be durable and heat resistant -as it may need to survive atmospheric temperatures substantially in excess of 406C and direct sunlight in tropical and subtropical areas, for example in Australia, wherein the ground surface temperature regularly exceeds 606C. The plastics material currently used for ground surface markings develops such resistance as a result of the gas torch heating by which they are fused to the ground surface. As 3D printed materials are not necessarily subject to such high temperatures during the application, it may be necessary to subject the ground markings to a post-application hardening treatment, which may be by microwave or infra-red heati ng, for example. A nti-sl i p/anti-ski d treatment may al so be applied duri ng this post-application treatment, as may the addition of microbeads.

[0052] FIG. 2 illustrates retroreflective particles arranged in a machine-readable pattern, in accordance with at least of the examples described herein. FIG. 3 illustrates a cross-section of retroreflective particles arranged in a machine-readable pattern, in accordance with at least of the examples described herein. As shown, retroreflective particles 210 are embedded in the topmost layer 110a of the discrete droplets 105. Shown are singular 'particles_ however, these may be groups of particles or indeed singular particles. For example, the retroreflective particles 210 may be deposited in sets of symbols, shown as white and black dots, to convey 'zeroes_ and 'ones_ to represent a binary instruction or code. In the present example of FIGS. 2 and 3, white dots represent zeros and the black dots represent ones, for a result of 0100100 which in ASCII binary is the symbol 1 _ -which may be interpreted as a warning to any device reading the retrorefl ective particles in such a way, as shall be further described herein.

[0053] As shown in FIG. 3 in particular, the retroreflective particles are partially submerged in the plastics material. In some examples, the retroreflective particles are partially submerged by 30-70% of their volume. It is necessary for the particles to be applied while the thermoplastics material is still molten so that the retroref I ective particles 210 particles sink into the topmost layer 110a and are 'keyed_ into place. In this way, the particles are very durable and still function as intended, partial submersion less than 30% jeopardizes the 'keying i n_ of the retroref I ective particles 210; similarly, greater than 70% jeopardizes the retroreflective ability of the retroreflective particles 210. In some examples, the retroreflective particles are deposited in a coded visible or machine-readable marking.

[0054] Additionally, coded visible or machine-readable markings may be introduced in other materials, which may include retro-reflective materials or metallic particles, such as magnetic particles, that can be used for guidance for pedestrian or vehicular traffic. R etroreflective beads may simulate cats-eyes in road markings, for example, or appear as coded symbols warning of hazards or defining a route which an autopilot system may follow.

Rather than having multiple identical such markings, as is necessary with conventional cars eyes, which are mass produced, it will be easy to print:custom-markings that can indicate distance from road junctions, for example. In some examples, the retroreflective particles are glass beads. The information to be encoded into the ground marking is to be converted into a format expected by the receiving device, which will be explained in more detail below, with reference to FIG. 12.

[0055] FIG. 4 shows an area of print in close-up, in accordance with at least one of the examples described herein. In some examples, the methods further comprise receiving an image; dividing the image into printable segments 410, wherein each printable segment comprises instructions for depositing a plurality of discrete droplets 105 on a ground surface and applying a plurality of retroreflective particles 210 on the ground discrete droplets. In some examples, the instructions comprise a type of molten plastics material, colour, number of layers, or another physical characteristic. The instructions may be referred to as a 3D printing map of the ground marking. The methods further comprise applying discrete droplets 105 according to the printable segments to form the image, wherein the patterned ground marking represents the image.

[0056] Printable segments 410 may contain a 3D matrix of printable instructions. For example, a ground marking may be a road boundary marking, such as a hard shoulder line for a highway. The instructions will comprise 3D matrix, wherein a first layer comprises the instructions for the location, shape, and colour for a thermoplastics material to be deposited, and a second layer comprises instructions for the location, depositing velocity, and shape of the application of retroreflective particles 210. Each layer of the 3D matrix may also comprise a plurality of other data.

[0057] In some examples, after hardening, the ground marking comprises at least two colours. A marking may be applied in a design using more than one colour by printing individual colours in separate areas of the marking. However, as with inkjet colour printing, a wide range of colours may be printed by melding primary colours. Whereas, using the conventional technique, multi-coloured surface markings for roads, playgrounds and the like are made in a restricted range of colours, sharply delineated, using methods according to the invention, a much wider range of colours may be had, which may blend smoothly into one another. L ikewise, a plurality of symbols, shapes, and different types of retroreflective particles may be applied to the surface of the thermoplastics materials to encode different information. The information may be inconspicuous or conspicuous to humans, that is to say that the arrangement (and therefore information represented by the retroreflective particles) may be visible to humans and/or machine-readable.

[0058] FIG. 4 shows a small area of discrete droplets of different primary colours Red (R) 422, Blue (B) 426, Green (G) 424, Black (B1) 434 and white (W) 432. These markings can be applied using a single print head comprising a plurality of dispensers, dispensing plastic in the form or droplets or as a filament as will be described in more detail below. Such a single print head may comprise a plurality of dispensers for different colours, for example, five such dispensers, one for white, one for black and three for primary colours. A further dispenser may be provided for clear plastic, acting perhaps as a varnish or other surface texture finish. The head may be scanned to produce a layer at a time. A surface layer or layers only may be coloured or patterned.

[0059] In some examples, the print instructions further comprise the step of arranging the discrete droplets in a machine-readable pattern. For example, some discrete droplets 105 may be deposited in a fashion that computer vision can read as an instruction. Such discrete droplets may comprise paints or inks that are invisible to the human eye, such as ultraviolet or infrared markings.

[0060] In some examples, it may be desired that after the molten plastics material has hardened, a higher coefficient of friction is required. This can be achieved by incorporating into the printing instructions the step of applying anti-slip material to improve the coefficient of friction of the molten plastics material. In some examples, the anti-slip material is applied at a first temperature. In some examples, the first temperature is in the range of 170C -230C. In some examples, the anti-slip particles comprise at least one of glass, flint sand, calcium carbonate, alumina particles, or mixtures thereof. The former application of anti-ski cVanti-s1 i p material would be in addition to the printing instructions comprising the step of applying retro-reflective particles. In some examples, the retrorefl ective particles are applied after the application of the anti -sl i p material, while the molten plastics material is at a second temperature, wherein the second temperature is lower than the first temperature. Accordingly, the plastics material may be deposited in a liquid phase such that the application of anti-slip material or retroreflective particles is keyed into the thermoplastics material adequately.

[0061] FIG. 5 shows a line printer arrangement, in accordance with at least one of the examples described herein. The line printer arrangement comprises a print head 620 and a plurality of dispensers 625. The dispensers 625 are adapted to dispense different colours of plastics material, and retroreflective particles 210. Accordingly, the dispensers 625 are fluidly connected to hoppers comprisi ng, as described above, white, black and three primary colours of plastics materials. A further dispenser 625 can be adapted to dispense clear molten plastics material (or at least a molten plastics material that goes clear after hardening), where, for example, a lower layer is required to show through. A further dispenser 625 is fluidly connected to a hopper comprising the retroreflective particles to be applied to the surface of the molten plastics material on the ground surface.

[0062] The print head 620 may comprise a line, as shown in FIG. 5, or a two-dimensional array (not shown) of dispensers 625, that are moved in the direction of Arrow A. The dispensers can be adapted to dispense different colours according to instructions for applying a plurality of discrete droplets 105 at a target location (e.g., target location 710 of FIG. 7) on the ground surface 120 so that the desired ground marking is built up.

[0063] The marking can be applied, however, using a line of dispensers 625, similar to a line printer in paper printing, which is traversed in the direction of Arrow A perpendicular to the line, or a two-dimensional array of dispensers, whereby to print in blocks of colour or pattern.

[0064] In addition to 3D printing plastics material, anti-slip/anti-skid finish is applied at time of printing, in the form, for example, of particles of glass or flint, which materials do not adversely affect the colour of the plastic, or aluminium oxide. In order to be retained in the surface and not sink in so far that they are completely absorbed, whereby they contribute nothing to retro-refl ectivity, such particles are applied at a given temperature of the plastic surface, which will depend on the physical properties of the material but can, for any particular material, be determined empirically. M i crobeads, imparting retro-reflectivity, are to be applied after any ant-slip/anti-skid material, and this may be at a different temperature. The anti-sl i p/anti -skid and retro-reflective treatment can be applied to the whole or to selected parts of the marking to encode information within the ground marking.

[0065] Desirably, the plastics material as laid will be durable and heat resistant -it may need to survive atmospheric temperatures substantially in excess of 406C and direct sunlight in tropical and subtropical areas, for example in Australia. The plastics materials currently used for ground surface markings develop such resistance as a result of the gas torch heating by which they are fused to the ground surface. As the presently disclosed materials are not necessarily subject to such high temperatures during application as gas torch application, it may be necessary to subject them to a post-application hardening treatment, which may be by microwave or infra-red heating, for example, or a chemical treatment such as a cross-I inking or curing treatment A nti-sl i p/anti -ski d treatment can also be applied dud ng this post-application treatment, as may the addition of microbeacls.

[0066] Applying ground marking discussed herein can result in markings of reduced thickness, as compared to conventionally applied plastic strips or sheet A problem with pre-loaded retroreflective particles in such strip or sheet available from at least one supplier thereof, is that on gas torch application the particles sink into the plastic, and more must be spread on top while the material is molten. These are supported, at least to some extent by the sunken particles. With thinner layers such as are possible with the current disclosure, much less particulate matter can be held in the plastic, and it is closer to the surface so that it supports surface particulate matter even when the upper surface is molten, perhaps as a result of hardening heat treatment. H owever, the layer-by-layer application of the molten plastic material means in any event that only the surface layer needs to be heated while the particulate material is being applied. If just a surface layer is required to be heated, an infra-red heater may be used instead of the microwave treatment which may tend to penetrate further.

[0067] An advantage of the application technique of the present disclosures over the conventional gas torch application is that the range of ground surfaces to which the marking may be applied is extended. Gas torch application is only applicable for outdoor concrete or tarmac, while the present printing techniques work on a wider variety of surfaces including wood and composite surfaces (e.g., by i ncorporati ng rubber crumb as a filler), as well as indoor surfaces.

[0068] FIG. 6 is a diagrammatic plan view of one embodiment of ground marking apparatus, in accordance with at least one of the examples described herein. The ground marking apparatus, or printing device 610, applies durable ground markings to a target position on a ground surface. The printing device 610 comprises at least one print head 620 comprising a plurality of dispensers 625; and a control unit (not shown) opedale to control the dispensers 625 to deposit plastics material 645 on the ground surface and apply retroref I ective particles 210 to the surface of the plastics material. The plastics material 645 may be stored/housed in a hopper 640. In some examples, the hoppers 640 may be adapted to gravity or pressure feed the dispensers they are fluidly connected to. In some examples, the dispensers may comprise nozzles through which the molten plastics material emerges in drops (or as a filament) under the control of valve means.

[0069] In some examples, the print head further comprises a print rack, the print rack comprises at least a horizontal rail, arranged orthogonal to a direction of movement of the printing device; a vertical rail, arranged orthogonal to the horizontal rail; and wherein the print head is affixed to the vertical rail.

[0070] FIG. 7 is a front elevation of the apparatus of FIG. 6, in accordance with at least one of the examples described herein. A second aspect of the invention provides an autonomous printing device 700 for encoding machine-readable information on a ground marking applied to ground surface 710. The autonomous printing device 700 comprises at least traction means 720 for supporting the printing device on the ground surface 120; drive means (not shown) for driving the traction means 720, and a control system (such as control system 1050 of FIG. 10) configured to control the drive means to guide the autonomous printing device across the target position on the ground surface. The autonomous printing device further comprises the print device 610 of the example in FIG. 6, as described above.

In particular, the print head 620 comprises at least one dispenser 625, and a print control unit (not shown) operable to control the dispenser 625 to deposit molten plastics material and apply retroreflective particles 210 at a target position 720 on the ground surface 120, wherein the molten plastics materi al hardens into a durable ground marking. Aspects of the ground marking apparatus, as described with reference to FIG. 6, are herein compatible with the autonomous printing dein ce.

[0071] FIG. 8 is a diagrammatic view of another embodiment of ground marking apparatus, in accordance with at least one of the examples described herein. FIG. 8 shows a vacuum nozzle 810, a heat source 820, a plastics dispenser 830, an aftertreatment device 840, a baffle 850, a grit dispenser 860 and a reiroreflective bead dispenser 870. The entirety of the apparatus moves in the direction of Arrow B. [0072] Glass beads (e.g., reiroreflective particles) from the retroreflective bead dispenser 870 are to be evenly dropped onto the hot thermoplastic strip immediately after its application, embedding and anchoring at a depth of 30% to 70%, preferably SO to 60%, by volume. In the art, the purpose of the glass beads is to provide initial night-time retrorefl ectivity of the pavement marking which without them, would be barely visible to the motorist However, the present application teaches to encode machine-readable information by arranging the reirorefl ective beads from bead dispenser 870 in a way to be read by a sensor or camera on a vehicle thereafter. In this way, the ground markings are given passive intelligence and can provide supplementary information to, for example, autonomous or semi-autonomous vehicles. The bead dispenser 870 shall be inspected frequently to ensure proper operation and to ensure uniform rates of each application over the entire marking surface.

[0073] In some examples, the glass beads are deposited in a coded visible or machine-readable marking. To begin machine-readable information is converted into one or more print instructions for the ground marking machine to print the machine-readable information. A controller (not shown) of the ground marking machine is configured to control a print head 800 to deposit a plurality of discrete droplets of molten plastic material on to the ground surface 120 and apply retroreflective particles, using retroreflective bead dispenser 870, to the molten plastic material based on the one or more print instructions. The method may also comprise breaking up the machine-readable information into printable segments, wherein each printable segment has a corresponding print instruction. The one or more print instructions comprise a set of distinguishable symbols, comprising a first symbol for encoding:zeros-and a second symbol for encoding:ones-. The distinguishable symbols are formed by the arrangement of the retroreflective particles as described in the one or more print instructions. The retroreflective particles may be arranged in a machi ne-readable only pattern, that is inconspicuous to a human when shining a light on the ground marking. The machine-readable information is at least one of: navigation data, road boundary information, di recti on information, parki ng i nformati on, parking guidance data, autonomous driving instructions, hazard information, ground surface data, instructions for an autonomous vehicle, contextual information, or point of interest information. The retroreflective particles are comprised of at least two types of retroreflective panicles, a first retroreflective particle activated by a first wavelength of light, and a second retroreflective particle activated by a second wavelength of light A baffle 850 separates the bead dispenser from vacuum nozzle 810, heat source 820, plastics dispenser 830, an aftertreatment device 840.

[0074] In some examples, the print head further comprises a thermometer (not shown) for detecting the temperature of the ground surface at the target position, an ambient temperature, and/or a temperature of a surface of the plastics material after deposition to the target position. Based on the sensed temperature heat source 820 provides a thermal energy adequate to pre-treatment the ground surface or provide an aftertreatment to the plastics material. In addition to applying molten plastics material, an anti-slip/anti-skid finish may be applied at the Ii me of printing, in the form of materials that do not adversely affect the cd our of the ground marking once hardened from grit dispenser 860. To be retained on the surface and not sink in so far that they are completely absorbed, whereby they contribute nothing to anti-sl i p or anti-skid protection, such particles should be applied at a given temperature of the plastic surface -specific to the composition of the molten plastics material. Likewise, glass beads, or other particles imparting metro-reflectivity, are applied at a temperature different to that at which anti-slip/anti-skid particles are applied from bead dispenser 870, and they are applied after anti-sl ip/anti-skid particles. The antisl i p/anti-skid and retro-reflective treatment may be applied to the whole or to selected parts of the marking.

[0075] FIGS. 9A-9D illustrate components on a print head of a device suitable for ground marking, in accordance with at least one of the examples described herein. There are various devices used to screed/extrude thermoplastic material onto the pavement The device should be positioned to protect it from the wind, sometimes the use of a baffle 850 or housed within a housing is suitable. In some examples, the print head further comprises a print rack, the print rack comprises at least a horizontal rail 912, arranged orthogonal to a direction of movement of the printing device; a vertical rail 914, arranged orthogonal to the horizontal rail 912; and wherein the print head is affixed to the vertical rail 914 moveable by a motor 910.

[0076] FIG. 9A comprises priming equipment for use on the ground surface 120 at the target position 710 before the application of the thermoplastic material. The priming equipment comprises a heater 924, such as heater 1072 of FIG. 10, and a primer material dispenser 922. The primer material shall be sprayed on the surface at the specified rates recommended by the manufacturer of the primer/sealer material. All of the priming equipment should be inspected and checked to ensure that it is completely operational and capable of disbursing the primer/sealer at the rate prescribed by the manufacturer. Because bond failures are most likely application related, they can be mi nimized by proper application controls. This can be accomplished through correct inspection at the target site and adapting the pretreatment of the ground surface based on the condition of the target site; therefore, computer vision is employed to provide this inspection (not shown). If specified prior to the thermoplastic application, the primer must be applied to all pavement surfaces at the manufacturers recommended application rates. It must set for the specified cure or evaporation time prior to thermoplastic being applied. Primed pavement surfaces must be striped within the specified set ti me or within the same working day. If the primed surfaces are not striped within these time limits, they must be reprimed prior to the thermoplastic application at the prescribed rate denoted by the manufacturer. If an approved epoxy primer is used, proportional mixing must be checked and thermoplastic application must occur before epoxy has cured. Improper primer/sealer application will cause bond failure between the thermopl asti c and substrate. Irrproper application may also result in physical degradation of the thermoplastic material by excessive pi nholi ng and blistering of the line. This degradation may occur through extraction of the binder by the solvent system contained in the primer/sealer promoted by improper drying time and application rates.

[0077] FIG. 9B comprises a print head with a plurality of dispensers 932. In addition to coloured molten thermoplastics material, as described above (e.g., with reference to FIG. 4). One of dispensers 932 may be a ribbon dispenser (e.g., soft filament dispensers), which typically requires heaters to complete the anchoring/melting of the thermoplastic once applied to the ground surface. Ribbon dispensers are and are suspended above the road surface, applying a forced-extrusion, well-defined thermoplastic line. Another type of dispenser 932 is spray dispensing devices, which create thermoplastic spray patterns that result in a uniformly thick, well-defined and securely bonded stripe as specified. Another type of dispenser utilizes a screed extrusion technique, that dispenses shoe rides (e.g., rumble strips) directly on the road surface and a continuous line is formed by a three-sided die with a control gate set to a pre-determined thickness -typically over 8mm. Although al kyd and hydrocarbon materials will fuse to one another on the road, they are incompatible in a melting kettle, hence separate dispensers are required for separate materials. Failure to completely clean out kettles during material changeovers can cause severe equipment problems, this is mitigated in the present system.

[0078] FIG. 9C comprises a heater 932 and temperature sensor 934 cleaner to clean the ground surface prior to the priming equipment treating the surface. The ground surface 120 should be more than visibly dry. Moisture is the most detrimental factor in bonding. Subsurface moisture can be present in amounts sufficient to affect proper bonding. Early morning dew and fog conditions will usually cause dampness. If excess pavement moisture exists, it will usually result in blistering the hot-applied marking. Blisters wiII form as surface bubbles which may or may not have burst open. They are easily spotted, and if the condition occurs, marking operations should be stopped until the pavement dries. The only way to be certain whether moisture is present is to conduct a test. There are numerous ways to test for moisture. When heating the target position 720 of the ground surface 120, nearby thermoplastic material can be monitored by the temperature sensor 934, if thermoplastic material is overheated, the colour pigments tend to break down and change in colour: white thermoplastic turns beige or creamy; yellow develops a brown or greenish tint.

[0079] FIG. 9D comprises a vacuum cleaner 944 to clean the ground surface prior to the priming equipment treating the surface. Ground surfaces must be clean, dust free, and dry.

Heavy deposits of existing painted pavement markings, polymer traffic tapes, built-up roadside accumulations of dirt, etc., will all require removal. In some cases, an air blast or manual or mechanical brooming will be sufficient to clean the surface. In others, more effort or different methods such as abrasive-blasti ng, water blasting, or mechanical removal will be needed. New thermoplastic applications should successfully bond to worn existing thermoplastic lines or preform thermoplastic markings, therefore, a sensor or camera (not shown) to detect the previously applied thermoplastics may be present next to the vacuum to determine if priming is needed or if a full 2mm of deposition is required. For example, it may be that due to a worn down prior thermoplastic marking, with a thickness of 1mm, no priming but application of an additional 1mm of thermoplastic is all that is required.

[0080] FIG. 10 is a schematic diagram of an exemplary apparatus for applying ground markings, in accordance with at least one of the examples described herein. A compressor (e.g., an air compressor) 1010 is fluidly connected to a solenoid 1020 and solenoid valve 1022 to provide an air supply 1015. The air supply to dispense the molten plastics material from dispenser 1024. A controller 1050 and battery 1055 are electrically connected through wires 1052 to the solenoid valve 1022 and compressor 1010, as well as the other components as described below. The controller 1050 provides control to devices and the battery 1055 provides power, however, the battery may be replaced or used in conjunction with a *shoreli ne_ power system mains power, or the like. A hopper 1032, such as a metal kettle or the like, comprising the plastics material (typically in a molten state), is fluidly connected to a pump/extruder 1034, controllable by controller 1050 through wires 1052 (from point A to point A) to pump the molten plastics material through a hose 1036 to the solenoid 1020 and solenoid valve 1022. In some Examples, the compressed air provided by the compressor 1010 atomises the molten plastics material into a spray as a deposition modality. In some examples, hose 1036 comprises insulation, heating elements, or a combination thereof. In some examples, a hopper 1032 may comprise anti-slip material or retroref I ective particles to be fluidly connected to a dispenser such as a solenoid 1020.

[0081] Compressor 1010, air supply 1015, solenoid 1020, solenoid valve 1022, dispenser 1024, hopper 1032, pump/extruder 1034, and hose 1036 are collectively referred to as the deposition system. A baffle 1040 is utilized to separate the deposition system from the treatment system. The treatment system may be used for pre-Weatment or after-treatment of the ground surface 120 (or more particularly, the target position 720 on the ground surface 120). The treatment system comprises a ground temperature sensor 1060, for example, an IR temperature sensor; a heater 1072, which may be a ground fan heater, a microwave heater, or an open flame gas torch; a vacuum ground cleaner 1074; and rotary encoder 1080 which may be a mechanical, optical, on-axis magnetic, or off-axis magnet rotary encoder; absolute or incremental.

[0082] The rotary encoder 1080 is used for converting the angular position or mot on of a shaft or axle to analogue or digital output signals; useful for knowing the position of the print head, and position of the autonomous (or semi-autonomous) device. For example, an optical encoder uses a light shining onto a photodi ode through slits in a metal or glass disc. Reflective versions also exist. This is one of the most comrnon technologies. However, optical encoders are sensi tive to dust, but this is typically not a problem with molten plastics material deposition. Power from battery 1055 and control from controller 1050 is delivered to the Treatment system by wires 1052. That is to say that the components of the aftertreatment system are electrically connected to the control ler 1050 and the battery 1055.

[0083] Mixing and agitating equipment may be incorporated in the hoppers 1032. Such equipment, such as kettles, must be equipped with material agitators to prevent hardening in the liquid phase, and must be capable of thoroughly mixing the material at a rate which will ensure even disbursement and uniform temperatures throughout the material mass.

[0084] FIG. 11 is a schematic diagram of an exemplary autonomous system for applying ground markings, in accordance with at least one of the exarrples described herein. The autonomous printing system 1100, comprises driving means 1110, which may be independently controllable motors affixed to wheels. The driving means 1110 move the autonomous system across the ground surface. The autonomous system may be semiautonomous. In the present disclosure semi-autonomous refers to devices and systems that require minimum human intervention and uti I i se advanced driver assist technologies, such as adaptive cruise control, lane keep assist and intelligent park assist, to reduce the effort required to manoeuvre the autonomous system and create the desired ground markings. A utonomous refers to devices and systems that are capable of manoeuvring without a human operator. The Society of Automotive Engineers (SA E) International and the US National Highway Traffic Safety Administration (NHTSA) have defined five different levels of semi-autonomous and autonomous vehicles based on the amount of human intervention required. The autonomous system comprises the exemplary apparatus for applying ground markings as described with reference to FIG. 10.

[0085] FIG. 12 is a schematic diagram of an exemplary autonomous system for decoding machine-readable information on ground markings, in accordance with at least one of the examples described herein. The autonomous system here is selected to be a road vehicle (e.g., a car) 1200, however, autonomous robots in factories, or the like, are considered to be within the scope of 'autonomous vehi de_ and is not intended to exclude other examples.

[0086] The vehicle 1200 comprises a light source 1210, a sensor 1220, and a controller (not shown). The light source 1210 is configured to emit light 1215 onto a ground surface 120 to illuminate ground markings comprising retroreflective particles 210, arranged in a machi ne-readable pattern, the machine-readable pattern comprising machine-readable information. T he light source 1210 may be configured to emit specific wavelengths of light, for example in the visible spectrum for revealing the retroreflective particles to the user.

The light source 1210 may be configured to emit specific wavelengths of light not in the visible spectra to keep the machine-readable pattern of the retroreflective particles inconspicuous to a user, but not the vehicle 1200.

[0087] The sensor 1220 may be a camera or the like, configured to capture an image of the ground surface 120 comprising a ground marking with retroreflective particles thereon. The sensor may be configured to selectively filter the captured image, or to selectively sense, a particle wavelength of light preferably the wavelength of light emitted by light source 1210. In addition, the sensor may be configured to reject other wavelengths of light to reveal the retro-reflective particles arranged in a machine-readable pattern on the ground surface 120.

[0088] The controller (not shown) is configured to decode the machine-readable information on a ground marking applied to a ground surface. To decode the machine-readable information the controller is configured to emit light 1215, from light source 1210, on the ground marking on the ground surface 120, wherein the ground marking comprises retroreflective particles, acquire at least one image of the reflected light from the retroref I ective particles, and convert the image of the reflected light into machine-readable information.

[0089] The ground marking may be made up of a plurality of discrete droplets and retroreflective particles that have been applied in layers. Each layer may have different retroref I ecti ve properties configurable to comprise different machine-readable information. For example, each layer may be activatable by a different wavelength of light, or only be readable (i.e., retroreflective) at specific angles -such that as the vehicle approaches the ground marking different layers, and therefore machine-readable information is revealed, in a similar manner to approach lighting systems used around runways for aircraft [0090] In some examples, the retroreflective particles are comprised of at least two types of retroreflective particles. A first retroreflective particle activated by a first wavelength of light, and a second retroreflective particle activated by a second wavelength of light [0091] The rehroreflective particles may be arranged in a machine-readable pattern. The retroref I ective part c I es may be arranged into sets of distinguishable symbols comprising a first symbol for encoding:zeros-and a second symbol for encoding:ones-. For example, the retroreflective particles 210 may be deposited in sets of symbols, shown as white and black dots, to convey 'zeroes_ and 'ones_ to represent a binary instruction or code. In the present example of FIG. 12, the symbols are shown as white and black dots to represent zeros and ones, respectively, for a result of 01001010, 01000100, 01000010 -such data is machine readable as binary, and can be decoded using known formats such as ASCII to be decoded as the symbols DB B. Such machine-readable information may be interpreted by the vehicle's on-board computer as at least one of: navigation data, road boundary information, di recti on information, parking i nformati on, parking gui dance data, autonomous driving instructions, hazard information, ground surface data, instructions for an autonomous vehicle, contextual information, or point of interest information.

[0092] FIG. 13 illustrates a block diagram of a computing module, in accordance with at least one of the examples described herein. In some examples, computing module 1302 may be corrrnunicatively connected to a user interface. In some examples, computing module 1302, may be the controller of the apparatus 1000 as described with reference to FIG. 13. In some examples, computing module 1302 may include processing circuitry, control circuitry, and storage (e.g., RAM, ROM, hard disk, a removable disk, etc.). Computing module 1302 may include an input/output. I/O, path 1306. I/O path 1320 may provide device information, or other data, over a local area network (LAN) or wide area network (WAN), and/or other content and data to control circuitry 1310, which includes processing circuitry 1314 and storage 1312. Control circuitry 1310 may be used to send and receive commands, requests, signals (digital and analog), and other suitable data using I/O path 1320. I/O path 1320 is connected to control circuity 1310 (and specifically processing circuitry 1314) to one or more communications paths. In some examples, computing module 1302 may be an on-board computer of the apparatus for paint markings, such as apparatus 1000. In some examples, the control circuitry 1310 is operable to receive an image to be printed. In some examples, the controller is configured to demarcate the image into a plurality of segments to be printed. In some exarnpl es, the control unit is operable to control the dispenser to deposit molten plastics material forming the image.

[0093] Control circuitry 1310 may be based on any suitable processing circuitry such as processing circuitry 1314. As referred to herein, processing circuitry should be understood to mean circuitry based on one or more microprocessors, microcontrollers, digital signal processors, programmable logic devices, field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), etc., and may include a multi-core processor (e.g., dual-core, quad-core, hexa-core, or any suitable number of cores) or supercomputer. In some examples, processing circuitry may be distributed across multiple separate processors or processing units, for example, multiple of the same type of processing units (e.g. two Intel Core i7 processors) or multiple different processors (e.g., an Intel Core i5 processor and an Intel Core i7 processor). In some examples, processing circuitry 1314 executes instructions for computing module 1002 stored in memory (e.g., storage 1312).

[0094] The memory may be an electronic storage device provided as storage 1312, which is part of control circuitry 1310. As referred to herein, the phrase "electronic storage device" or "storage device" should be understood to mean any device for storing electronic data, computer software, or firmware, such as random-access memory, read-only memory, hard drives, solid-state devices, quantum storage devices, or any other suitable fixed or removable storage devices, and/or any combination of the same. Non-volatile memory may also be used (e.g., to launch a boot-up routine and other instructions). Storage 1312 may be sub-divided into different spaces such as kernel space and user space. K emel space is a portion of memory or storage that is, e.g., reserved for running a privileged operating system kernel, kernel extensions, and most device drivers. User space may be considered an area of memory or storage where application software generally executes and is kept separate from kemel space so as to not interfere with system-vital processes. K ernel mode may be considered as a mode when control circuitry 1010 has permission to operate on data in kemel space, while appl icati ons running in user mode must request control circuitry 1310 to perform tasks in kernel mode on its behalf.

[0095] Computing module 1302 may be coupled to a communications network. The communication network may be one or more networks including the Internet, a mobile phone network, mobile voice or data network (e.g., a 36, 46, SG or LTE network), mesh network, peer-to-peer network, cable network, cable reception (e.g., coaxial), microwave link, DS L reception, cable i ntemet reception, fiber recepti on, over-the-ai r infrastructure or other types of communications network or combinations of communications networks. Computing module 1302 may be coupled to a secondary communication network (e.g., Bluetooth, Near Field Communication, service provider proprietary networks, or wired connection). Paths may separately or together include one or more communications paths, such as a satellite path, a fiber-optic path, a cable path, a path that supports Internet communications, free-space connections (e.g., for broadcast or other wireless signals), or any other suitable wired or wireless communications path or combination of such paths.

[0096] In some examples, the control circuitry 1310 is configured to carry out any of the methods as described herein. For example, storage 1312 may be a non-transitory computer-readable medium having instructions encoded thereon to be carried out by processing circuity 1314, which cause control circuitry 1010 to carry out a method for encoding and decoding ground markings.

[0097] It should be understood that the examples described above are not mutually exclusive with any of the other examples described with reference to FIGS. 1 -13. The order of the description of any examples is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to i mplementations that solve any disadvantages noted above or in any part of this disclosure.

[0098] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed disclosure, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

[0099] This disclosure is made to illustrate the general principles of the systems and processes discussed above and is intended to be illustrative rather than limiting. More generally, the above disclosure is meant to be exemplary and not limiting and the scope of the disclosure is best determined by reference to the appended claims. In other words, only the claims that follow are meant to set bounds as to what the present disclosure includes.

[0100] While the present disclosure is described with reference to particular example applications, it shall be appreciated that the disclosure is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements may be made without departing from the scope and spirit of the present disclosure. Those skilled in the art would appreciate that the actions of the processes discussed herein may be omitted, modified, combined, and/or rearranged, and any additional actions may be performed without departing from the scope of the disclosure.

[0101] Any system feature as described herein may also be provided as a method feature and vi ce versa. As used herein, means plus function features may be expressed alternatively in terms of their corresponding structure. It shall be further appreciated that the systems and/or methods described above may be applied to, or used in accordance with, other systems and/or methods.

[0102] Any feature in one aspect may be applied to other aspects, in any appropriate combination. In particular, method aspects may be applied to system aspects, and vice versa. Furthermore, any, some, and/or all features in one aspect can be applied to any, some, and/or all features in any other aspect in any appropriate combination. It should also be appreciated that particular combinations of the various features described and defined in any aspect can be implemented and/or supplied and/or used independently.

Claims (20)

1. CLAIMS1. A method for encoding machine-readable information on a ground marking applied to a ground surface, the method comprising: converting the machine-readable information into one or more print instructions; and controlling a print head to: deposit a plurality of discrete droplets of molten plastic material on to the ground surface; and apply retroreflective parti cl es to the molten plastic material based on the one or more print instructions.
2. The method of claim 1, further comprising breaking up the machine-readable information into printable segment, wherein each printable segment has a corresponding print instruction.
3. The method of claims 1 or 2, wherein the discrete droplets and retroreflective particles are applied in layers, each layer having different retroreflective properties configurable to comprise different machine-readable information.
4. The method of any of claims 1 to 3, wherein the discrete droplets harden into a durable ground marking.
5. The method of any of claims 1 to 4, further comprising: receiving an image; converting the image into print instructions; and wherein the plurality of discrete droplets of molten plastic material is deposited, based on the print instructions, to form the image. 2. 3. 4. 5.
6. 6. The method of any of claims 1 to 5, wherein the retroreflective particles are comprised of at least two types of retroreflective particles, a first retroreflective particle activated by a first wavelength of light, and a second retroreflective particle activated by a second wavelength of light
7. 7. The method of any of claims 1 to 6, wherein the one or more print instructions comprise a set of distinguishable symbols, comprising a first symbol for encoding:zeros-and a second symbol for encoding:ones-.
8. 8. The method of claim 7, wherein the distinguishable symbols are formed by the arrangement of the retroref I ective particles in the one or more print instructions.
9. 9. The [lied iod of any of claim 1 to 8, wherein the retroreflective particles are arranged in a machine-readable pattern. 15
10. 10. The method of any of claims 1 to 9, wherein the machine-readable information is at least one of: navigation data, road boundary information, direction information, parking information, parking guidance data, autonomous driving instructions, hazard information, ground surface data, instructions for an autonomous vehicle, contextual information, or point of interest information.
11. 11. An autonomous pri nti ng device comprising: a print head comprising a plurality of nozzles configured to deposit a molten plastics material and apply retroreflective particles to a ground surface; and a controller operable to carry out the method of clairns 1 to 10.
12. 12. A method for decoding machine-readable information on a ground marking applied to a ground surface, the method comprising: emitting light on the ground marking on the ground surface, wherein the ground marking corrprises retroreflective particles; acquiring at least one image of the reflected light from the retroreflective particles; and converting the image of the reflected light into machine-readable i nformati on.
13. 13. The method of claim 12, wherein the emitted light is emitted at a first wavelength, the method further comprising: filtering the image to select the first wavelength; and rejecting other wavelengths to reveal a pattern from the image.
14. 14. The method of claims 12 or 13, wherein the discrete droplets and retroreflective particles are applied in layers, each layer having different retroreflective properties configurable to comprise different machine-readable information.
15. 15. The method of any of claims 12 to 14, wherein the retroreflective particles are comprised of at least two types of retroreflective particles.
16. 16. The method of claim 15, further comprising a first retroreflective particle activated by a first wavelength of light and a second retroreflective particle activated by a second wavelength of light.
17. 17. The method of any of claims 12 to 17, wherein the reWoreflective particles are arranged into sets of distinguishable symbols comprising a first symbol for encoding:zeros-and a second symbol for encoding:ones-.
18. 18. The method of claim of claims 12 to 17, wherein the retroreflective particles are arranged in a machine-readable pattern.
19. 19. The method of any of claims 12 to 18, wherein the machine-readable information is at least one of: navigation data, road boundary information, direction information, parking information, parki ng guidance data, autonomous driving instructions, hazard information, ground surface data, instructions for an autonomous vehicle, contextual information, or point of interest information.
20. 20. An autonomous vehicle comprising: a light source configured to emit light onto a ground surface; a sensor to capture an image of a ground marking on the ground surface; and a control ler operable to carry out the method of any of claims 12 to 19.