Machine-readable surface and method

Abstract

A method of preparing a machine-readable surface for an autonomous vehicle comprising, coating the surface of a drive area for the autonomous vehicle in a substantially curable material and optically detectable elements and a protective layer, to provide a machine- readable code throughout substantially the entire drive area of the vehicle.

Description

[0001] Machine-Readable Surface and Method

[0002] The invention relates to a machine-readable surface and a method of producing a machine- readable surface for an autonomous vehicle.

[0003] Background

[0004] AMRs (automated / autonomous mobile robots), AGVs (automated guided vehicles), IGVs (intelligent guided vehicles) and SDVs (self-driving vehicles) are driverless vehicles that are used to transport materials, pallets or other items in industrial warehouses or manufacturing units.

[0005] In order to perform tasks, an autonomous vehicle or robot requires knowledge of its environment and its location, as well as location information around other objects or entities that it may need to engage with or avoid.

[0006] Sensors on the vehicles help them to learn routes and navigate autonomously or to follow a programmed route, for example around a warehouse.

[0007] Navigation systems commonly include fixed line or grid-based systems, which may involve the use of QR codes, optical or magnetic tape, reflectors or LEDs. Such systems can be expensive to set up accurately and maintain. It can also be difficult to optimise routes or change the layout following the initial installation and programming.

[0008] The vehicles can be configured to follow a trained path on a pre-built map, but this has the disadvantage that any changes or variations may be difficult to incorporate. Alternatively, the vehicle can be configured to perform an initial scan of an existing area to collect environmental data and build a map of the environment. Such maps can also be updated dynamically based on sensor input as the vehicle moves around gathering data.

[0009] This is particularly useful for logistics systems and warehouse management where, for example the vehicle can relay its position to dispatching systems to monitor performance and enhance efficiency in production lines and warehouses.

[0010] It would be desirable to provide an improved machine-readable surface. One aspect of the invention provides a method of preparing a machine-readable surface for an autonomous vehicle comprising, coating the surface of a drive area for the autonomous vehicle in a substantially curable material; dispersing a plurality of irregular solid flakes on the substantially curable material before fully curing; and applying a protective layer over the irregular solid flakes; wherein the irregular solid flakes adhere to the substantially curable material in a substantially random configuration to provide a machine-readable code throughout substantially the entire drive area of the vehicle.

[0011] Advantageously, dispersing the plurality of irregular solid flakes on the wet substantially curable material before it is fully dried and / or it is substantially uncured, provides the advantage that the flakes adhere to the substantially curable material where they fall. The substantially curable material may therefore cure with the flakes in situ in the substantially curable material.

[0012] One advantage of the present invention is that the irregular shape of the solid flakes may provide increased variation in the machine readable surface.

[0013] Optionally, dispersing the plurality of irregular solid flakes comprises scattering.

[0014] The flakes may be scattered under pressure using a stream of compressed gas.

[0015] In certain embodiments, dispersing the plurality of irregular solid flakes comprises spraying.

[0016] Advantageously, the plurality of irregular solid flakes may be sprayed under pressure using compressed gas, preferably compressed air.

[0017] Advantageously, the plurality of irregular solid flakes may be directed in a stream of compressed air.

[0018] In this way, it may be advantageously possible to direct the dispersal of irregular solid flakes in pressurised gas and prevent clumping of flakes. Optionally, the method comprises the step of creating an electronic map of substantially the entire drive area using the machine-readable code.

[0019] The substantially random configuration may comprise non uniform orientation of the plurality of irregular solid flakes.

[0020] The non-uniform orientation may comprise substantially randomly oriented planes, with respect to the plane of the surface.

[0021] Advantageously, the non-uniform orientation of the plurality of irregular solid flakes with respect to the plane of the surface, may increase variation in the machine readable surface pattern.

[0022] In certain embodiments, the irregular solid flakes adhere to the substantially curable material in a non-planar arrangement.

[0023] This provides the advantage that some flakes may sink further into the substantially curable material and others may remain on the surface, providing greater variation in the machine- readable surface.

[0024] In certain embodiments, non-uniform orientation of the plurality of irregular solid flakes comprises a non-planar surface.

[0025] Optionally, the method comprises a step of buffering and / or sanding the drive area to provide a substantially flat or uniform surface.

[0026] Optionally, the machine-readable code comprises a quick-response code.

[0027] In certain embodiments, the plurality of optically detectable elements comprise randomly shaped particles having a maximum diameter of between about 0.5 and 10mm.

[0028] In certain embodiments, the plurality of optically detectable elements may comprise a maximum diameter of between about 0. 1mm to about 3mm.

[0029] In certain embodiments, the plurality of optically detectable elements may comprise a maximum diameter of between about 0.5mm to about 3mm.

[0030] Optionally, the plurality of irregular solid flakes comprises a mixture of first and second optically detectable elements having contrasting colours.

[0031] The protective layer may comprise a matte finish. Advantageously the protective layer provides a low reflectance value for optimum performance sensitivity for the sensor of an automated guided vehicle.

[0032] The plurality of irregular solid flakes are dispersed at a density of between about 150 to 500 per 35cm2.

[0033] In certain embodiments, the irregular solid flakes comprise plastic flakes.

[0034] In certain embodiments, the plurality of irregular solid flakes are dispersed at a density of between about 350 to 425 per 35cm2.

[0035] This range of flake density advantageously provides optimum performance sensitivity for the sensor of an automated guided vehicle and provides sufficient contrast between flakes and surface coating.

[0036] Another aspect of the invention provides a machine-readable surface prepared by the method of the invention.

[0037] Another aspect of the invention provides a machine-readable surface for an autonomous vehicle comprising a drive area coated In a substantially curable material; said substantially curable material comprising a plurality of irregular solid flakes adhered thereto; and a protective layer over the irregular solid flakes; wherein the irregular solid flakes are adhered to the substantially curable material in a substantially random configuration and non-uniform orientation to provide a machine-readable code throughout substantially the entire drive area of the vehicle.

[0038] Yet another aspect of the invention provides apparatus for dispersing a plurality of irregular solid flakes on a surface comprising a body portion having an inlet for connecting a source of compressed air, an actuator and a nozzle a nozzle outlet; a chamber for holding the irregular solid flakes; and an elongate directing means defining a channel in fluid communication with the nozzle outlet; wherein the elongate directing means is configured to direct propulsion of the flakes from the apparatus in a stream of compressed air and collect the irregular solid flakes which are propelled through the nozzle outlet but are not expelled from the channel.

[0039] Advantageously, the directing means provides control of flake density applied to the surface and prevents clumping of flakes.

[0040] The directing means may be an elongate tube. In certain embodiments, the directing means is detachable from the nozzle.

[0041] Advantageously, in use, the directing means may be directed in a substantially upwards direction at near vertical or an acute angle to the vertical.

[0042] Yet another aspect of the invention provides a system comprising the apparatus for preparing a machine-readable surface for an autonomous vehicle by dispersing a plurality of irregular solid flakes on a surface having the substantially curable layer before fully curing; such that the irregular solid flakes adhere to the substantially curable material in a substantially random configuration to provide a machine-readable code throughout substantially the entire drive area of the vehicle.

[0043] Yet another aspect of the invention provides a kit of parts comprising a substantially curable material; a plurality of irregular solid flakes; and a topcoat; and instructions for preparing a machine-readable surface for an autonomous vehicle by the method of the invention.

[0044] In certain embodiments, the kit of parts comprises the apparatus for dispersing a plurality of irregular solid flakes on a surface comprising a body portion having an inlet for connecting a source of compressed air, an actuator and a nozzle a nozzle outlet; a chamber for holding the irregular solid flakes; and an elongate directing means defining a channel in fluid communication with the nozzle outlet; wherein the elongate directing means is configured to direct propulsion of the flakes from the apparatus in a stream of compressed air and collect the irregular solid flakes which are propelled through the nozzle outlet but are not expelled from the channel.

[0045] One aspect of the invention provides a method of preparing a machine-readable surface for an autonomous vehicle comprising, coating the surface of a drive area for the autonomous vehicle in a substantially curable material; dispersing a plurality of optically detectable elements on the substantially curable material; and applying a protective layer over the optically detectable elements; wherein the optically detectable elements provide a machine-readable code throughout substantially the entire drive area of the vehicle. In certain embodiments, the method comprises the step of creating an electronic map of substantially the entire drive area using the machine-readable code.

[0046] The plurality of optically detectable elements may be dispersed in a substantially random configuration.

[0047] Optionally, the machine-readable code comprises a quick-response code.

[0048] In certain embodiments, the plurality of optically detectable elements comprise randomly shaped particles having a diameter of between about 0.5 and 10mm.

[0049] In certain embodiments, the plurality of optically detectable elements comprise a diameter of between about 0.5mm to 3mm.

[0050] Optionally, the plurality of optically detectable elements comprises a mixture of first and second elements optically detectable elements having contrasting colours.

[0051] The protective layer may comprise a matte or non-reflective finish.

[0052] Advantageously, the protective layer may have a low reflectance value.

[0053] The reflectance value be a gloss value of under around 100, preferably under about 90 and more preferably under about 70, when measured with a gloss meter of 85 degree incident angle.

[0054] In certain embodiments, the plurality of optically detectable elements are dispersed at a density of between about 150 to 500 per 35cm2.

[0055] In certain embodiments, the plurality of optically detectable elements are dispersed at a density of between about 215 to 714 per 50cm2.

[0056] In certain embodiments, the plurality of optically detectable elements are dispersed at a density of between about 500 to 600 per 50cm2.

[0057] In certain embodiments, the substantially curable material comprises a liquid.

[0058] In certain embodiments, the optically detectable elements comprise plastic flakes.

[0059] Advantageously, the optically detectable elements may be recycled plastic flakes.

[0060] Optionally, the step of applying the optically detectable elements comprises applying said optically detectable elements to the substantially curable material before curing the substantially curable material. This may provide the advantage of securing the optically detectable elements in place before application of a protective layer.

[0061] In certain embodiments, the surface comprises a floor, such as a factory floor.

[0062] In certain embodiments, the drive area comprises the entire floor area.

[0063] Advantageously, the machine-readable code may be for navigation of the autonomous vehicle.

[0064] In certain embodiments, the method comprises the step of scanning the machine readable code provided by the optically detectable elements using an autonomous vehicle.

[0065] In certain embodiments, the method comprises the step of creating an electronic map of substantially the entire drive area using the machine-readable code.

[0066] Optionally, the machine-readable code comprises a QR code.

[0067] In certain embodiments, the substantially curable material is bonded to the drive area.

[0068] In certain embodiments, the protective layer is substantially transparent.

[0069] Advantageously, the protective layer may be bonded to the substantially curable material.

[0070] The method may be a coating method.

[0071] Another aspect of the invention provides a machine-readable surface prepared by the method of the invention.

[0072] The machine-readable surface may comprise a base layer, a layer comprising optically detectable elements, and a protective layer.

[0073] The machine-readable surface may comprise a laminate coating.

[0074] The laminate coating may comprise a base layer, a layer comprising optically detectable elements dispersed in a substantially random configuration, and a substantially transparent protective layer.

[0075] Advantageously, each location of the drive area comprises a unique machine-readable code.

[0076] Advantageously, the substantially random configuration of the optically detectable elements may comprise a quick-response (QR) code readable by the autonomous vehicle. Optionally, the substantially random configuration comprises a substantially continuous quick-response (QR) code throughout substantially the entire drive area.

[0077] Another aspect of the invention comprises a floor comprising the machine-readable surface prepared by the method of the invention.

[0078] Yet another aspect of the invention comprises a system comprising the machine-readable surface prepared by the method of the invention and a computer for controlling navigation of one or more autonomous vehicles.

[0079] The system may optionally comprise one or more autonomous vehicles.

[0080] Yet another aspect of the invention provides a kit of parts comprising a substantially curable material; a plurality of optically detectable elements; and a topcoat; and instructions for preparing a machine-readable surface for an autonomous vehicle by the method of the invention.

[0081] Figures

[0082] In the Figures, which illustrate embodiment of the invention by way of example only:

[0083] Figure 1 is a schematic representation of one embodiment of the method of the invention.

[0084] Figure 2 shows one embodiment of the surface of the invention

[0085] Figures 3a to 3b show embodiments of the surface of the invention having different flake densities.

[0086] Figure 4a is a perspective view of one embodiment of the applicator of the invention

[0087] Figure 4b is a perspective view illustrating one embodiment of the nozzle of the applicator of the invention.

[0088] Figure 4c is a perspective view illustrating the elongate tube of the applicator of the invention. Detailed Description

[0089] Where the existing floor of a warehouse or factory has been painted with an epoxy or polyurethane coating, or is otherwise homogeneous, the use of automated guided vehicles requires expensive adaptation and may require ceiling guides or a fixed line system that the robot can follow to navigate around the floor.

[0090] Using the method of the present invention, existing flooring can be adapted for use with an autonomous vehicle.

[0091] Referring to Figure 1, which illustrates one embodiment of the method of the invention, at a step 1, one or more base layers is / are applied to an existing floor using an epoxy or acrylicbased product, that may have a gloss finish, such as Black Wax Black Ultra 10, an ultra high gloss floor polish for black floors, or a clear wax floor polish over a painted surface. In other embodiments, other products may be used to form the base layer and such products may be of another base colour, such as white, grey etc. The base layer colour is preferably a light colour, such as light grey RAU 7047, 7035 or light blue RAU 5015. Other colours, such as traffic green RAU 6024, traffic yellow RAU 1023 or traffic red RAU 3020.

[0092] Darker colours may also be utilised because plastic flakes dispersed in Step 2, are of contrasting colours and therefore will provide contrast sufficient for a sensor of an autonomous vehicle to read.

[0093] The base layer may be applied to the entire floor, using for example, a microfibre roller. If multiple layers are applied, each layer is allowed to dry before application of the next, until a final layer is applied and is ready to receive application of plastic flakes.

[0094] The base layer is applied in a sufficient thickness for optimal drying / curing time. It may be applied by mechanical or manual means. A microfibre roller may be utilised to apply the black wax, to give an even coating and the correct thickness.

[0095] If too much black wax is applied before the plastic flakes are applied, the flakes tend to float and clump together with black wax in between. If black wax layer too thick it will not dry in time.

[0096] The base layer is applied at between 50g and 200g per m2. This results in a thickness of between around 0.1 mm and 0.4 mm. At a step 2, Botdrops™ are applied to the base layer in a random pattern. Botdrops™ are small, thin pieces of one or more of: plastic, textile, quartz, ceramic, metal, wood, paper and / or glass. The small, thin pieces of any of these materials may be in the form of flakes formed by shredding or grinding. In certain embodiments, Botdrops™ may comprise paint splatters of between about 0.1 and 5mm. It is envisaged that suitable for use within the scope of the invention may comprise any colour variation that can be read, depending on the type of floor and application.

[0097] In the illustrative example shown in the Figures, at a Step 2, plastic flakes are applied to the base layer in a random pattern. The flakes stick to the black wax layer, and this is then left to dry / cure with the flakes in place (step 3).

[0098] Plastic flakes are widely available in the form of recycled plastic flakes such as rPET or other mixed plastic materials and come in randomly shaped flakes. The plastic flakes are small, thin pieces of plastic having irregular and random shapes and aspect ratios.

[0099] Flakes may be provided by random shredding or chopping, or otherwise broken into small pieces of sheet material such as plastic. In other embodiments of the invention, any suitable small and irregular particles may be utilised, such as sheet flakes, chips, pellets or granules, flakes made from metal or foil, wood or other fibrous materials.

[0100] The plastic shapes may be of contrasting colours, such as black and white flakes in a roughly 50 / 50 mix. This is particularly advantageous where the base layer colour is a dark colour, such as with black wax. When a dark floor is sprinkled with too many flakes, the contrasting colours of the flakes reduce large white or dark spots on the floor, therefore minimising any areas of low contrast that could otherwise affect efficacy of the sensor.

[0101] At an optional step 4, the floor is prepared to receive a topcoat. This may require sanding with a buffer to remove any plastic flakes or parts of flakes that may be protruding from the surface because of the random orientation of flakes landing in the black wax base layer. A non-uniform surface created by random orientation of flakes sticking in the base layer is undesirable for movement of the autonomous vehicle. The floor may then require vigorous cleaning to remove any flakes that are not properly adhered or have become loosened during the buffer treatment. At step 5, a protective layer is applied to the floor, which may be a transparent matte polyurethane varnish. This provides a durable top layer, which is wear resistant and protects the plastic flakes, because tire wear can be detrimental to the floor.

[0102] The protective layer or topcoat is required to be sufficiently transparent and sufficiently thin such that the sensor of an autonomous vehicle can easily detect the unique pattern made by the combination of plastic flakes on the floor. Without the protective layer, tires of the autonomous vehicle or other vehicles such as forklifts, may dislodge the flakes, which could disrupt the integrity of the pattern.

[0103] The transparent protective layer has a consumption of around 100g per m2, this results in a layer thickness of around 1mm. In some embodiments the layer may be between around 1- 3mm.

[0104] The surface of the protective layer is matte ie has a low reflectance value.

[0105] The PU protective topcoat is applied in an even distribution and bonds to the layer comprising the plastic flakes, sealing the floor to provide a smooth drive surface for the autonomous vehicle, which is both smooth and matte ie has a low reflectance value, for example a gloss value of under 100, or more preferably under 90 when measured with a gloss meter of 85 degree incident angle.

[0106] In some cases, an initial floor preparation step 0 may be required to repair any areas of floor that may need filling for an even surface, or to remove existing floor coatings, which may otherwise interfere with bonding and cause peeling of the laminate machine-readable coating.

[0107] At a step 6 the flooring is mapped to a computer by scanning the floor with a reading device, which may comprise the sensor of an autonomous vehicle, which can acquire images of the floor as it moves. In this way, the image data from the sensor can be used to create an electronic map of the floor. Because of the random shapes and distribution of the plastic flakes, each location readable by the sensor on the floor produces a unique image or QR code, which can be used by the robot and / or system to determine location of the robotic vehicle at any point on the floor, with respect to the electronic map, and the vehicle may travel on any desired route over the entire floor. To enhance accuracy, the vehicle may be equipped with more than one sensor and pairs of images or consecutive images may be compared.

[0108] The terms autonomous vehicle, robotic vehicle, robot and vehicle are used interchangeably in this document and are intended to refer to any kind of robotic entity of the kind that are used to or capable of transporting materials, pallets or other items, such as those used in industrial warehouses or manufacturing units. This includes but is not limited to AMRs (automated / autonomous mobile robots), AGVs (automated guided vehicles), IGVs (intelligent guided vehicles) and SDVs (self-driving vehicles) and other driverless vehicles.

[0109] Using this method, the entire exposed surface of a warehouse factory floor or warehouse can form a movement area - or drive area, in which an autonomous vehicle can successfully operate. In effect, the method produces a substantially continuous QR code across the entire surface of the flooring in a factory or warehouse, which has a unique footprint at each location read by a sensor.

[0110] As shown in Figures 2 and 3a-3c, a flooring surface 20, such as a painted floor of a warehouse or factory, comprises base coat 21, black plastic flakes 22 and white plastic flakes 23. A transparent top coat (unlabelled) covers, and is bonded to, the layer comprising plastic flakes.

[0111] With the right combination of flakes, a unique pattern is created over the entire floor area, making the entire area into a uniquely coded environment.

[0112] It has been determined that the optimum flake size is particles with a maximum diameter of between about 0.1 and 3mm. In certain embodiments the flake size (maximum diameter) may be between about 0.5 and 10mm, and more preferably between about 0.5 - 3mm. In some examples the flake size is around 1mm. The diameter of the flakes can vary slightly because the flakes have random differing shapes. Maximum diameter refers to the greatest distance between two points on the perimeter of the flake (which may be of an irregular shape).

[0113] The method of the invention utilised a mixture of flakes in highly contrasting colours, such as a monochrome mix of black and white flakes, in approximately equal ratio. At least two colours of contrasting flakes are used. In certain embodiments, more than two flake colours may be utilised, such as black, white and brown flakes together.

[0114] As well as flake size, the density and distribution of flakes are important factors for accurate reading of images and mapping of location by autonomous vehicles. AGVs tested included models from Kumatech BV and Primevision US.

[0115] The flakes are distributed on the flooring surface at around 1kg of flakes per 20m squared, or 215 ft. The flakes may be applied to the surface by any means necessary to ensure random distribution of the flakes over that area in the required density. This may include machine or hand application. Areas of flooring mat be divided or mapped into sections using a chalk line or strap line to ensure the correct density per sectioned area.

[0116] As illustrated in Figures 3a to 3c, sample areas of 7cm by 5cm were tested for accurate reading by AGV sensors to determine the optimum flake density. For optimum performance of the robot, this was determined to be between 150 - 500 particles (flakes) in an area of 7cm by 5 cm, which corresponds to the sensor view area.

[0117] If too many particles are present in any portion of the floor, the paint or black wax is obscured from camera view and will not produce a clearly contrasting image. As such, the density of flakes is important, with an optimum high number of flakes but with a contrasting floor remaining visible.

[0118] The speed of motion of the AGV may also affect quality of reading, depending on flake density. Usually the AGV travels at a speed of around 6km per hour. A flake density of between about 150 to 400 particles per 35cm2produces a very good result, with between around 150 to 425 particles per 35cm2being an optimum density. In general, at faster speeds of AGV motion, a lower number of particles produces a better imaging result.

[0119] Referring to Figure 3a, the flake density of the sample (7 x 5cm) is 101, which gives moderate distribution of flakes and can be read by the AGV. At a higher flake density of 376 (per 35cm2) as shown in Figure 3b, the AGV reading is highly accurate. However, as in Figure 3c at a low density of 54 flakes per 35cm2errors in establishing location may occur.

[0120] The invention provides a number of advantages over existing systems. Low cost materials such as recycled plastics can be utilised to adapt existing flooring using an inexpensive and non-labour intensive coating method. Further, because of the random pattern throughout the floor, if any areas are damaged, those areas may be quickly and easily repaired using the same method and the floor can be re -mapped for accurate navigation.

[0121] As illustrated in Figure 4a to 4c, a spray gun 24 is used to disperse the optically detectable elements such as plastic flakes on a surface. As shown in Figure 4a, a hand held spray gun 24 is configured to receive and disperse solid material such as flakes or chips under pressure using compressed air.

[0122] The spray gun 24 comprises a generally L shaped body 25 with a handle portion 26 and a nozzle head 27. A trigger or finger grip lever 28 is pivotable with respect to the body 25 to control flow of compressed air via one or more valves (not shown) from an air inlet 29. The air inlet 29 is connectable to a source of compressed air via a hose (not shown), typically utilising 2-4 bar of pressure.

[0123] A container 30 having a substantially conical portion 30’ and a lid 30” is mounted on the nozzle head 27 of the spray gun 24 the hold solid dry material such as plastic flakes.

[0124] The nozzle head 27 is illustrated in greater detail in Figure 4b. An inlet 31 is configured to receive the plastic flakes. A discharge opening 32 in the nozzle head 27

[0125] When the finger grip lever is pivoted towards the handle portion 26, air flows through a channel in the body 25, dry plastic flakes are drawn into the nozzle head 27 and expelled in a stream of air via a discharge opening 32 in the nozzle head.

[0126] The discharge opening 32 is at least 3mm in diameter, to allow for expulsion of plastic flakes without clogging of the aperture.

[0127] As shown in Figures 4a and 4c, an elongate tube 33 is mounted on the nozzle head 27 and defines a conduit in fluid communication with the discharge opening 32. The elongate tube 33 is a metal tube with a wall thickness of around 1mm. The elongate tube 33 is around 25cm in length and around 10cm in diameter. In other embodiments, the tube 33 may be of plastic or other material.

[0128] In use, the spray gun 24 is positioned such that the elongate tube 33 is angled in an upwards direction with respect to a flooring surface, which may be substantially vertical or at an angle to the vertical. In accordance with the method of the invention, the flooring surface is coated with an epoxy or polyurethane base layer as in Step 1 of Figure 1, which base layer may still be wet / not fully cured when the plastic flakes are applied using the spray gun 24.

[0129] The lever 28 is manually activated to commence airflow through the spray gun 24, and flakes in the container 30 are drawn into the stream of compressed air passing through the nozzle head 27 and forced through the discharge opening 32 into the elongate tube 33 and expelled into the atmosphere via an open end 34 of the elongate tube 33, which in use is angled upwards.

[0130] The flakes are blown out under pressure from the elongate tube 34 and fall in a random pattern on the flooring surface. They stick to the uncured / wet base coating, adding texture and structure. Because the base layer is uncured or not fully cured when the flakes are applied, they adhere to it where they fall. The flakes land on the floor at different angles and adhere to in non- uniform orientations, thereby creating a non-planar surface arrangement.

[0131] Many flakes will land and stick to the floor in such a way that they are randomly oriented and do not lay flat in the plane of the floor. The randomly oriented planes of the flakes on the floor enhances the random effect of the pattern created by increasing variation. Some flakes sink deeper into the base layer and others remain partially sticking out.

[0132] Because of the random orientation of the flakes with respect to the floor, a floor preparation step referred to at step 2 of Figure 1 in which sanding and / or buffering may be required to ensure a uniform surface is created before application of the protective layer.

[0133] The elongate tube 33 provides several advantages. It ensures even spreading and prevents clumping of flakes that may otherwise fall straight into the wet paint below the spray gun 24. The tube 33 also acts as a collector for excess material. It prevents uncontrolled fall-through due to pressure loss or clogging at the discharge opening 32. Since the spray gun 24 is used in an upwards firing direction, any non-discharged flakes will fall back under gravity into the elongate tube 33. Smaller flakes which lose speed during expulsion get caught in the tube rather than clogging the system, allowing clean, controlled dispersion. The elongate tube 33 may be detachable such that is can be easily removed for cleaning or replaced.

[0134] The spray gun assembly provides precision spreading and direction of plastic flakes onto a surface, allowing control of required flake density and more uniform coverage, preventing clumping or excessive accumulation in some areas of the floor.

[0135] Further embodiments of the applicator are envisaged within the scope of the invention. For example, applicator may be in the form of a non-manual dispersal apparatus or broadcasting spreader of any suitable type.

Claims

Claims1. A method of preparing a machine -readable surface for an autonomous vehicle comprising, coating the surface of a drive area for the autonomous vehicle in a substantially curable material; dispersing a plurality of irregular solid flakes on the substantially curable material before fully curing; and applying a protective layer over the optically detectable elements irregular solid flakes; wherein the irregular solid flakes adhere to the substantially curable material in a substantially random configuration to provide a machine-readable code throughout substantially the entire drive area of the vehicle.

2. A method according to Claim 1, comprising the step of creating an electronic map of substantially the entire drive area using the machine-readable code.

3. A method according to Claim 1 or 2, wherein the substantially random configuration comprises non uniform orientation of the plurality of irregular solid flakes.

4. A method according to any of claims 1 to 3, wherein the machine-readable code comprises a quick-response code.

5. A method according to any preceding claim, wherein the plurality of irregular solid flakes comprise randomly shaped particles having a maximum diameter of between about 0.5 to about 10mm.

6. A method according to any preceding claim, wherein the plurality of irregular solid flakes comprise a maximum diameter of between about 0. 1mm to about 3mm.

7. A method according to any preceding claim, wherein the plurality of irregular solid flakes comprises a mixture of first and second optically detectable elements having contrasting colours.

8. A method according to any preceding claim, wherein the protective layer comprises a matte finish.

9. A method according to any preceding claim, wherein the plurality of irregular solid flakes are dispersed at a density of between about 150 to 500 per 35cm2.

10. A method according to any preceding claim, wherein the plurality of irregular solid flakes are dispersed at a density of between about 350 to 425 per 35cm2.

11. A machine-readable surface prepared by the method of any of claims 1 to 10.

12. A machine-readable surface for an autonomous vehicle comprising a drive area coated In a substantially curable material; said substantially curable material comprising a plurality of irregular solid flakes adhered thereto; and a protective layer over the irregular solid flakes; wherein the irregular solid flakes are adhered to the substantially curable material in a substantially random configuration and non- uniform orientation to provide a machine-readable code throughout substantially the entire drive area of the vehicle.

13. Apparatus for dispersing a plurality of irregular solid flakes on a surface comprising a body portion having an inlet for connecting a source of compressed air, an actuator and a nozzle a nozzle outlet; a chamber for holding the irregular solid flakes; and an elongate directing means defining a channel in fluid communication with the nozzle outlet; wherein the elongate directing means is configured to direct propulsion of the flakes from the apparatus in a stream of compressed air and collect the irregular solid flakes which are propelled through the nozzle outlet but are not expelled from the channel.

14. A system comprising the apparatus of claim 13 for preparing a machine-readable surface for an autonomous vehicle by dispersing a plurality of irregular solid flakes on a surface having the substantially curable layer before fully curing; such that the irregular solid flakes adhere to the substantially curable material in a substantiallyrandom configuration to provide a machine-readable code throughout substantially the entire drive area of the vehicle.

15. A kit of parts comprising a substantially curable material; a plurality of optically detectable elements; and a topcoat; and instructions for preparing a machine -readable surface for an autonomous vehicle by the method of any of claims 1 to 10 .

Images