Complex Geometry Pavement Milling

BACKGROUND
1. Field

The present disclosure relates in general to systems and methods for pavement milling.

2. Related Art

Aggregate materials, such as asphalt and concrete, are commonly used to build and repair roads, parking lots, and other areas where a smooth durable surface is desired. Asphalt concrete, often abbreviated as simply as “asphalt,” may be comprised of aggregate, additives, and a binding material, usually comprising a bituminous binder.

Smooth road surfaces improve ride quality and reduce surface water collection areas. Compacted asphalt is more durable and has a higher load carrying capacity than initially deposited and spread asphalt. Compacting the asphalt removes air spaces contained in the aggregate and binder mix. As air is removed, asphalt density increases. Increasing compacted asphalt density, usually described as % maximum theoretical density, improves road longevity and load carrying capacity. Many road projects have a target density ranging between 93% and 96%.

Asphalt does not behave as a free-flowing fluid. Aggregate will extrude into nearby contours, but will not flow more than a few centimeters without direct agitation. Compression and extrusion forces under a screed or compactor are typically not enough to homogenize density across the entire width of that screed or compactor. This complicates road repair. Compaction analysis shows particles are mostly restrained in horizontal directions and can be approximated as vertical movement only. This simplifies required lift height and compaction estimates at the job site. Because mass is conserved, mass=density×volume results in the following ratio: density₁×volume₁=density₂×volume₂. With the vertical dimension, or height, as the only changing dimension, the ratio can be rewritten as density₁×height₁=density₂×height₂.

Delivered asphalt poured from the dump truck can have a relative density as low as 60%. Paving and compacting over an uneven sub-base or a sub-base with localized irregularities can cause bridging, where asphalt compacted over raised sub-base irregularities quickly reaches high density and holds the screed and compactor weight as if it were solid material. This prevents consistent asphalt compaction over lower sub-base areas. For example, an evenly spread top surface spread over an uneven sub-base with 0.5″ peaks and 0.5″ pits, a nominal starting lift height of 2.0″, and asphalt delivered at 65% relative density starts with a minimum lift of 1.5″, a nominal lift of 2″, and a maximum lift of 2.5″. Compaction will likely stop when the minimum areas reach high relative density, for example 97%. The new minimum height will be 65%×1.5″/97%=1″, or 0.5″ overall height reduction. Relative density in asphalt over the nominal height areas will be 0.65%*2″/1.5″=87%. Relative density in asphalt over the localized pits will be 0.65%×2.5/2″=81%. In this bridging example, the highly compacted asphalt over peaks supports the compacting surface, resulting in areas with relative compaction as low as 81%

The uncompacted surface, or starting height, can be directly viewed exiting some trench paver designs, but is usually a flow stagnation plane which intersects the invisible material head stagnation line as it contacts the front edge of the screed. Material below this stagnation plane will compact and pass under the screed. Material above usually slowly circulates above the stagnation plane.

Grading, milling, and otherwise preparing sub-base surfaces requires significant effort and equipment investment. When repairing a road it is common practice to use a road mill, sometimes called a cold planer or scarifier, to mill a trench at least 8 feet wide, the typical minimum paving width, even if only repairing a 2 foot wide defect. This additional effort is required to maintain a consistent density across the paved cross section from initially deposited material through to the final compaction operation while also trying to make the fully compacted repaired surface flush with the existing road surface at the edge of the repaired section.

Roadways paved with asphalt can develop ruts, potholes, cracks, surface irregularities, and other defects. These defects sometimes require that a section of asphalt roadway be partially removed and replaced. Existing systems mill a fixed width section while adjusting mill cutting depth. Common practice is to adjust mill cutting depth relative to the mill traction elements in order to maintain a smooth, flat milled surface as the mill passes over road defects.

The environmental impact of roadway resurfacing is significant. Used asphalt must be reprocessed or disposed of and new asphalt is petroleum based and energy intensive to produce. Both of these actions are a significant source of CO2. It has been estimated that 90M tons are milled and reprocessed in the US each year, and that 0.5 metric tons CO2 are released per ton of fresh asphalt paved.

One type of machine which attempts to adjust milled surface profiles is described in U.S. Pat. No. 10,323,364 by Cochran. This machine attaches the mill cutting tools to various diameter plates which are stacked on a rotating shaft. Mill profile can be adjusted by stacking cutting plates with different diameters in a sequence matching the desired mill profile. While this machine can create a continuous custom mill profile perpendicular to the cut path, it must be stopped and adjusted to change the mill profile.

Another type of machine which attempts to vary milled surface profiles is described in U.S. Pat. No. 8,262, 168 by Hall et al. This machine uses two or three horizontal mill drums, one drum placed on a forward axis and one or two drums placed on a rear axis. The mills can be adjusted laterally along the rotating axis, which allows milling various widths with one machine. The rear axis can also be lowered, which allows an offset cut that is the width of the rear mill. While this machine can adjust major cut boundaries, it does not have the resolution that may be desirable to remove localized defects with a minimum of material.

Another machine which cuts specific profiles is described in U.S. Pat. No. 6,843, 535 by Thomas et al. The apparatus described cuts a repetitive pattern in the upper surface, for example a rumble strip. The mill height control is mechanically linked to a cam profile which repetitively raises and lowers the mill as the milling machine moves along the cutting path. Changing the contour of the cam will change the repetitive cut pattern on the road surface. While this device does control surface cuts, it does not adapt those cuts to remove specific areas of material in random patterns.

Another machine which cuts channels and profiles along a variable path is described in U.S. Pat. No. 11,384,489 by Martinez. This cutting machine is attached to a guide rail. The guide rail can contain a combination of straight and curved sections. The cutting machine is attached a set distance from the guide rail and cuts a path that set distance from the rail. While this may allow a form of variable path cuts, it requires physically attaching a guide rail to the ground.

A machine which uses sensors in the cutting zone is described in U.S. Pat. No. 10,829,899 by Sturos. Cutting depth at multiple locations across the cut width may be measured and used to identify partial width cuts and to calculate the quantity of material removed. While sensing multiple heights across the width of the surface to be cut can provide an overall surface profile, it may not be sufficient to identify defects.

Another machine which uses sensors to control an autonomous vehicle along a defined path is described in U.S. Pat. No. 11,054,831 by O'Donnell et al. Boundaries, start points, work specifications, and a work plan are loaded into a machine controller, which activates steering and other machine operations based on machine location according to a work plan. While establishing a work plan may be beneficial while milling fixed width cuts, it is not sufficient for identifying defects and adjusting milling operations to minimize material removed with those defects.

Another machine which uses sensors to identify and avoid objects in the work zone is described in U.S. Publication 2020/0019192 by O'Donnell. This device uses 3D sensors to identify objects in the work zone and to override operator controls which may cause the machine to strike the object. While object identification and avoidance may be useful, it is not the same as identifying defects to be repaired.

A combination of machines which use sensors to identify road surface defects, remove them, and replace the removed area with new asphalt is described in U.S. Patent Application Publication 2022/0290383 by Buschmann et al. This device uses surface scans to create a digital surface, identifies a fixed and full width digital target milling profile, and controls operations to achieve that profile. While this approach may work with traditional milling and paving machines, it does not minimize material removal around the defects or prepare the surface for dynamic paving.

Another machine which uses sensors to identify and avoid objects in the work zone is described in U.S. Pat. No. 10,776,638 by Engelmann. This device uses sensors to identify objects in the work zone and milling machine direction of travel. Controllers initiate an object avoidance routine to avoid a predicted collision. While object identification and avoidance may be useful, it is not the same as identifying defects to be repaired.

Another machine which uses sensors to identify objects, warn the operator, and avoid collisions is described in U.S. Publication 2016/0265174 by Engelmann et al. This device uses ground penetrating radar to identify, locate, and notify the operator of objects hidden from view. While object identification and avoidance may be useful, it is not the same as identifying defects to be repaired.

As such, there is a need for a system and method to address such limitations.

SUMMARY

Advances in paving technology enable compacting asphalt to a consistent density over uneven surfaces and surface irregularities. Milling practices and machine designs which create a full width flat paving surface may no longer be necessary to maintain consistent asphalt density through subsequent compaction steps. In accordance with some embodiments, the apparatus disclosed herein can mill complex geometry as a mechanism to reduce the quantity of road material removed, reduce the quantity of road material reprocessed, and reduce the quantity of new material applied during road rehabilitation.

Disclosed is an apparatus that removes road material in complex geometries, and associated methods of operation. The apparatus performs a process that identifies a complex material removal pattern which removes defects with a minimum of additional material. A control system of the apparatus controls the milling machine in such a way that the complex geometry material removal is achieved within a defined variance.

One embodiment of the present disclosure comprises a digital surface of the road, electronic signatures of road defects, and a digital processing unit. The digital surface may be generated by visible sensors, Lidar sensors, infra-red sensors, radar, ground penetrating radar, ultrasonic sensors, a single sensor, multiple sensors of a single type, or multiple sensors of more than one type. The digital surface created by the sensors is entered into the processing unit. The processing unit compares the digital surface with signatures of road damage, which are stored on a digital memory device and are updated from time to time. The road defect signatures include not only an identification but also a minimum material removal requirement in all three dimensions. Once a defect is identified, a minimum material removal map is created and sent to a control system.

The control system compares the minimum material removal map with the available complex geometry milling tools. Tools are selected and tool paths, including a cut depth aka mill depth, are identified. The tool paths are selected to remove all material in the minimum material removal map while minimizing additional material removed outside the minimum material removal map. The intended 3D complex geometry cut, or predicted milled surface, is sent to the milling machine elements control unit, which may be the same unit as the 3D complex geometry control unit or may be a separate control unit.

In another embodiment, the apparatus is a road mill. The road mill may include a frame, traction devices, power unit, position detection sensor, control station, enclosed mill, cutting elements mounted on the mill, material extraction, material removal conveyor. Mill is divided into multiple drum segments, each of which can be independently raised and lowered. Drum segments may rotate horizontally or vertically, and a mill is comprised of horizontal drum segments, vertical drum segments, or both. A control unit adjusts drum segment height according to mill position over 3D complex geometry map.

Other devices, apparatuses, systems, methods, features, and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional devices, apparatuses, systems, methods, features, and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims.

BRIEF DESCRIPTION OF THE FIGURES

The invention may be better understood by referring to the following figures. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the figures, like reference numerals designate corresponding parts throughout the different views.

FIG. 1 is a schematic block diagram of a horizontal axis milling machine.

FIG. 2 is a schematic block diagram of a milling attachment coupled to a power unit.

FIG. 3 is an example illustration of a digital surface created from a measured surface.

FIG. 4A is a schematic top view of a road, illustrating pavement defects.

FIG. 4B is a schematic side cross-sectional view of a road, illustrating pavement defects on a road.

FIG. 5 is a top perspective view of a minimum material removal map.

FIG. 6 is a top perspective view of a predicted mill surface that is produced by using a tool path, mill cutting profiles, and a target depth.

FIG. 7 is a flowchart illustrating a method for minimizing milled road material using complex geometry.

FIG. 8A is a schematic block diagram of a multiple drum mill with more than one vertical mill arranged in two partially overlapping rows.

FIG. 8B is a schematic block diagram that illustrates the top view of a multiple vertical mill arranged in two partially overlapping rows.

FIG. 9A is a schematic block diagram of an example of a horizontal mill with multiple drums aligned in a row.

FIG. 9B shows the front section view of multiple horizontal mill 110 arranged in one row.

FIG. 10A is a side view schematic block diagram of a full width horizontal mill with laterally sliding horizontal drums aligned in a second row.

FIG. 10B shows the front section view of a full width horizontal mill with laterally sliding horizontal drums.

DETAILED DESCRIPTION

In this disclosure, where possible, the same reference numbers will be used throughout the drawings to refer to the same or similar parts.

FIG. 1 is a system block diagram of an example of a known horizontal axis milling machine 171. In this example, the horizontal axis milling machine 171 comprises a frame 172, one or more traction devices 173, a horizontal mill 110, a milling chamber 113, and one or more conveyors 112. Traction devices 173 may be attached to frame 172 with an actuator 174. Milling machine 171 typically removes damaged road material and the material around that damage. Road material may be asphalt 151 or another millable material. Extending actuator 174 raises frame 172 and the attached horizontal mill 110. The milling depth of cut 153 is controlled by adjusting front and rear actuators 174. Horizontal mill 110 comprises a drum 111 which rotates around drum axis 115. Drum axis 115 may be fixedly or adjustably attached to frame 172.

Multiple cutting elements 117 are fixedly attached to drum 111, each cutting unit holds a pick 114. Picks 114 are arranged in a pattern which substantially scrapes the full width of drum 111. Picks 114 wear during use and are accessible for repair and replacement while milling machine 171 is not operating.

Milling machine 171 traction devices 173 may drive on road surface 150 or sub-base 152 in direction of work 170. Milling machine 171 is operated to create the smoothest sub-base 152 possible, typically by maintaining a consistent depth of cut 153. In some cases, drum 111 is not wide enough to remove the desired amount of material. In these cases, milling machine 171 removes material in multiple partially overlapping passes.

The milling chamber 113 contains debris, which is collected and transported from the milling machine using conveyor 112. Some material may be temporarily held in hopper 116 before being transported to a truck for removal from the job site.

In this example, the milling operations may be manually controlled or partially controlled by one or more controllers 160. In some embodiments, each controller 160 may include one or more microprocessors configured with instructions to perform calculations, communications and other interactions with system components as described elsewhere herein including, without limitation, operation and positioning of horizontal mill 110, drum 111 and actuators 174.

While the arrangement of certain components of horizontal axis milling machine 171 is conventional and known, additional components and systems can be added for implementation of improved milling techniques, as described further herein. In particular, controller 160 may be configured to, inter alia, procure and/or analyze digital surface scans towards identification of pavement defects, and control operation of the milling machine for automated milling to e.g. minimize required material removal, as described hereinbelow. In some embodiments, digital surface sensor 300, also known as a scanning device, may be included directly on a milling machine in order to scan surface 150 before it is milled. Sensor 300 may collect information using, e.g., inertial sensors, physical contact sensors, electromagnetic sensors, sonic sensors, or a combination of more than one sensor type. Sensor 300 may be a single sensor or a combination of sensors, as described elsewhere herein.

While controller 160 is illustrated schematically as a block within horizontal axis milling machine 171, it is contemplated and understood that in some embodiments described herein, controller 160 may be implemented as a wholly or partially distributed system, as is known in the art of computational systems. For example, aspects described herein as being performed by controller 160 may be implemented, in whole or in part, by a network-connected server, or via a smartphone, tablet or other mobile computing device in operative communication with a local controller 160 within horizontal axis milling machine 171.

In FIG. 2, a system block diagram of an example of a known milling attachment 271 is shown coupled to a power unit 270. Power from power unit 270 is transferred to milling attachment 271 usually using hydraulic, mechanical, or electric connections. Milling attachment 271 may incorporate a horizontal mill 110 (analogous to that shown in FIG. 1), with horizontal mill 110 comprising a drum 111, a milling chamber 113, a drum axis 115, cutting elements 117, and picks 114. Attachment points on the power unit 270 are raised or lowered to change depth of cut 252. The milled debris is contained in milling chamber 113 and exits milling attachment 271 as loose-granular material covering the cut area. Milling attachment 271 cuts a fixed width path, in direction of work 170, where multiple passes may increase the total milling width. In this example, the milling operations may be manually controlled or partially controlled by one or more controllers 260 (analogous to controllers 160).

FIG. 3 is an example illustration, in partial perspective view, of a digital surface 320 created from a measured surface 328. FIG. 3 illustrates several common digital surface 320 formats, where each format converts measurements of the measured surface 328 into a digital processing system usable format. Measurements of the measured surface 328 may be captured by a scanning device, inertial sensors on the machine, physical contact sensors, or any other device with an analog or digital electric output. In some embodiments, such scanning sensors may be installed locally on a milling machine (such as sensor 300 on milling machine 171), whereby digital surface 320 may be procured and analyzed directly by milling machine 171, potentially enabling continuous, real-time scanning and complex milling of a paved surface.

In other embodiments, sensors procuring digital surface 320 may be provided on a separate scanning system (not shown), whereby digital surface 320 may first be procured by the separate scanning system. In some such embodiments, digital surface 320 may be transmitted to a separate processing system (such as controller 160) for analysis as described herein. In other embodiments, some portion of the subsequent analysis of digital surface 320, identification of defects and determination of milling paths may be performed locally by the scanning system, with processed data being output to a milling machine controller for implementation of the milling path, as described further hereinbelow.

One digital surface 320 format collects a series of point 321 measurements into a large number of points, called a point cloud 322. As the number of points 321 in a given area increase, the collection of points more accurately represents measured surface 328.

Another digital format uses a grid of pixels 323. When

viewed from the top, pixels 323 are continuous and non-overlapping. Each pixel 323 is assigned a height value, usually representing the average height of the measured surface 328 covered by that pixel 323. Smaller pixels have a higher surface density and more accurately represent measured surface 328.

Another digital surface 320 format combines a series of height measurements 325 recorded along one or more trace lines 324. Height measurements 325 may be evenly spaced or unevenly spaced. Trace lines 324 may be evenly spaced or unevenly spaced. Height measurements 325 may be a list of values or may be the result of a formula approximating values along trace lines 324.

Another digital surface 320 format combines mesh nodes 327 into a surface approximating mesh 326. Mesh nodes 327 may be evenly spaced or unevenly spaced. The mesh nodes 327 include heights that are usually calculated to make an average mesh 326 height approximate an average measured surface 328 height.

The above common digital surface formats are not exclusive and are included as examples for illustration. The complex geometry pavement milling method described e.g. in

FIG. 7 may use one or more of these, and/or other, digital surface 320 formats.

FIGS. 4A and 4B illustrate common types of road defects 450, with FIG. 4A providing a top plan view and FIG. 4B providing a cutaway cross sectional elevation. In one type of road defect 450, the bond between neighboring particles of aggregate has broken. This may be observed by visible surface defects, such as surface cracks 458, pits 451, and/or potholes 452 where the road material has separated from neighboring material and has been displaced from its original position. In many cases, one or more sub-surface defects 453 is present in addition to the visible surface defects. Sub-surface defect 453 could include overloaded sub-base material with damaged particles, partially displaced sub-base material, frost heaves, scoured sub-base material with air voids under the road surface, and saturated sub-base material which is unable to support surface loads.

Another common road defect 450 occurs between larger sections of road surfaces and/or multiple paving passes. This includes separated pavement joints 454 and granulated surfaces 455. Separated pavement joints 454 typically occur at the common edge of two paving passes where aggregate particles from one pass are not fully bound to neighboring aggregate particles from a second pass. Granulated surfaces 455, sometimes called raveling, can result from thin overlay lifts which do not sufficiently bond with underlying support lifts. Granulated surfaces 455 can also result when insufficient binder is included in the asphalt mix, when solvents dissolve some of the asphalt binder, and when abrasive vehicles scrape the top surface. Both separated pavement joints 454 and granulated surfaces 455 may have other causes.

Another common road defect 450 occurs when the road surface 150 is not as smooth as intended. This is usually the result of a surface rise 456 above the intended road surface or surface depression 457 below the intended surface. Surface rise 456 may be the result of heavily loaded roads, usually in hot climates, where road material is slowly extruded out from the loaded zone and into unloaded zones. Surface rise 456 may also be the result of paving practices, for example a compactor bow wave which cooled and hardened before subsequent compaction passes could press the surface back to the intended height. Surface rise 456 may also be the result of screed height adjustments, paver speed changes, paver stop/start points, or paving over an uneven sub-base 152 without a dynamic paver. In this case it may be part of a multi-meter long surface wave which is difficult to observe by eye but can be measured using lidar and other surface scanning sensors. Surface depression 457 typically are the result of similar events which cause surface rise 456. Both surface rise 456 and surface depression 457 may have other causes.

Other road defects, such as extra binder pooling to the surface, sometimes called bleeding, and broken aggregate particles can occur. The above descriptions are indicative of common road defects, not an exhaustive list.

FIG. 5 illustrates the minimum material removal map 520. Each type of road defect 450 will have a defined minimum horizontal clearance 550 and minimum vertical clearance 551. The machine operator may be able to adjust the minimum horizontal clearance 550 and minimum vertical clearance 551 from an initial value. The updated minimum horizontal clearance 550 and minimum vertical clearance 551 may be stored as a replacement for the initial value or as part of a unique user defined minimum clearance set. In some embodiments, minimum vertical clearance 551 may be set at a value extending between 0 and 150 mm below minimum height (i.e. the depth from the road surface) of road defect 450. In some embodiments, minimum horizontal clearance 550 may set at a value extending between 0 and 200 mm outward from the outer edges of road defect 450. Other values for minimum vertical clearance 551 and minimum horizontal clearance 550 may be used. In some embodiments, minimum vertical clearance 551 and minimum horizontal clearance 550 may depend, at least in part, on factors including one or more of road material characteristics, the nature of the defect being repaired, and anticipated load and utilization of the roadway under repair.

A minimum material removal volume 521 is created for each road defect 450 by combining boundary surfaces created by minimum horizontal clearance 550, minimum vertical clearance 551, and the upper road surface 150 enclosing a road defect 450. In some cases, the upper vertical boundary is extended beyond the upper road surface to an arbitrary large distance which simplifies volume creation calculations.

The minimum material removal volumes 521 are combined with digital surface 320 to create the minimum material removal map 520.

FIG. 6 illustrates the predicted milled surface 620, calculated using tool path 621, available mill cutting profiles, and target depth 622. The tool path 621 is created to remove all material in minimal material removal volumes 521 of minimum removal map 520, while minimizing additional material removed. In typical applications, material is removed from the area created by the mill cutting profile as it is swept along the tool path 621. Tool paths 621 may therefore depend upon the drum dimensions, include a lateral position along axis 624, and include a depth or vertical position for the drum which may vary along the tool path. Some mills may have multiple drums 111 such that the total material removed is the union of swept cutting profiles.

FIG. 7 shows a method 720 for minimizing milled road material using complex geometry. For ease of description, the method 720 is described with reference to elements found in FIGS. 1-6; however, it should not be considered an exhaustive list of representative elements, such that FIGS. 1-6 may include additional applicable elements that were omitted for simplicity rather than due to a lack of relevancy.

In step 721, the method begins by loading the digital surface 320 of the road into a controller 160. In the embodiment shown, a single upload for the entire pass or continuous section of work is loaded. Other embodiments may load shorter segments. Segments may be sufficiently small that the data upload may be considered a continuous process rather than a batch process. In some embodiments, digital surface 320 may be procured and generated locally by the milling machine performing the method (e.g. via digital surface sensor 300 in FIG. 1)

In some embodiments of step 721, sub-surface scans may be uploaded to controller 160 in addition to digital surface 320. Sub-surface scans identify subsurface defects 453 using ground penetrating radar, sonic scanners, magnetic resonance, nuclear density sensors, or some other means to measure sub-surface structure.

In step 723, road defects 450 are identified, including subsurface defects 453 when subsurface information is available.

A road defect 450 may be identified in some embodiments by comparing characteristics of a road surface (e.g. as reflected in digital surface 320 loaded in step 721) with predetermined defect digital characteristics. Defect digital characteristics comprise of a digital library with types of defects and variations of digital surface 320 which are unique to or associated with that type of defect. In embodiments where subsurface scans are loaded in step 721, defect digital characteristics associated with a defect type may also include subsurface scan variations which are unique to or associated with that type of defect. In some embodiments, such as where step 723 is performed locally by controller 160, the digital library of defect digital characteristics may be stored within, or otherwise made accessible to, controller 160.

Additional or alternative techniques may be utilized for identification of road defects 450 in step 723. For example, a machine learning model may be pretrained to identify types of road defect 450 based on digital surface scan data and/or subsurface scan data. Such a model may be used in combination with the aforementioned digital library of defect digital characteristics (e.g. the model being trained to select a defect type from amongst a library of defect types made available to the model), or in lieu of a digital library (e.g. the model being trained to directly identify and characterize defects based on digital surface data, without reference to a maintained library). In either case, such a model may be implemented locally (e.g. via controller 160, which may include or interoperate with neural network processors, AI inference engines, or the like), feeding digital surface 320 or subsurface scans as input to the model and outputting identification and characterization of road defects 450. Such identification and characterization may include, inter alia, the type of defect, affected portion of the road surface, and defect depth.

At step 724, minimum removal map 520 is created. Minimum material removal map 520 may be created using road defects 450 identified in step 723, minimum horizontal clearance 550 and minimum vertical clearance 551. Minimum material removal volume 521 can be determined as the combination of vertical and horizontal surfaces.

In one embodiment, the center of a road defect 450 is identified, e.g. by controller 160 analysis of digital surface 320. A horizontal defect boundary is calculated by vertically projecting road defects 450 to a virtual calculation plane. The virtual calculation plane is a horizontal plane which may be aligned with the average of road surface 150 heights, or which may be any other arbitrarily located horizontal plane. Lower resolution road defect 450 scans may create gaps in the horizontal defect boundary, which may be closed during processing with straight lines connecting defect edge points, defining a loop enclosing the road defect. The enclosed loop is expanded outward by minimum horizontal clearance 550. Vertical surfaces of minimum material removal volume 521 can then be determined by sweeping the extended enclosed loop vertically to create complex geometry vertical edges.

In another embodiment, the horizontal defect boundary is calculated by horizontally measuring the horizontal distance from the defect center-point to the outermost defect edge in radial increments of 3 degrees or less. The radial points are placed on a virtual calculation plane. Each of the radial points are connected with straight lines, curves which intersect the radial points, or a combination of both. The enclosed loop is expanded outward by minimum horizontal clearance 550. The extended enclosed loop is swept vertically to create complex geometry vertical edges defining the vertical surfaces of minimum material removal volume 521.

Target depth 622 may be set by the user at the start of a milling run, may be defined by subsurface defect 453 vertical depth and minimum vertical clearance 551, or a combination of both.

The uppermost surface of minimum material removal volume 521 comprises road surface 150 or a clearance surface above road surface 150.

Minimum material removal volume 521 is the volume enclosed by the surfaces defined above. Minimum material removal map 520 includes the minimum material removal volumes 521 with information from digital surface 320.

At step 726, tool path 621 is created using minimum material removal volume 521 and the mill cutting profile. Tool path 621 is created to remove all material in minimum removal map 520 while minimizing additional material removed, minimizing mill vertical movement, and, in mill embodiments configured for lateral movement, minimizing mill lateral translation. Material is removed from the volume created by the mill cutting profile as the mill is swept along tool path 621 at target depth 622. Some mills may have multiple drums 111 in which case portions of the milling tool path are followed by each of the multiple mill drums, and the total material removed is the union of swept cutting profiles.

At step 727, controller 160 adjusts mill drum 111 or multiple mill drums 111 to follow tool path 621 as milling machine 171 moves in the direction of work 170.

FIG. 8A illustrates one embodiment of multiple drum mill 810 with more than one vertical mill 811 arranged in two partially overlapping rows. Controller 160 adjusts vertical mill 811 height independently according to multiple tool paths 621 as the machine moves in direction of work 170. Each vertical mill 811 rotates around a drum axis 115. Both rows are contained within milling chamber 113, which consists of side plates 812 and moldboard 813. Controller 160 sends a signal to actuator 174, which adjusts drum height. Controller 160 sends a signal which starts or stops drum motor 870, independently spinning each drum as required. Drum motor 870 may be electric, hydraulic, pneumatic, or mechanical linkage to the main machine power unit. Another embodiment includes cutting wheels 814 tangentially aligned with vertical mill 811.

FIG. 8B shows the top view of multiple instances of vertical mill 811, arranged in two partially overlapping rows. Cut paths of multiple vertical mills 811 are created to remove the least amount of material while also fully removing minimum material removal volume 521. In another embodiment, vertical mills 811 are arranged in more than two rows. Vertical mills 811 may also be arranged in rows where the outer cut edge of the first-row drum is tangent to the cut diameter of the second-row drum (i.e. the cutting paths of vertical mills 811 do not overlap in the direction of work).

Another embodiment of a mill powers more than one instance of multiple drum mill 810 with the same power unit. These power units may be electrical, hydraulic, pneumatic, or mechanically linked to the main machine power unit. More than one drum may be physically linked, hydraulically linked, or otherwise connected to operate at the same time.

FIG. 9A illustrates an embodiment featuring horizontal mill 910 with multiple drums 911 aligned in a row. Controller 160 adjusts drum 810 height independently according to multiple tool paths 621.

Each horizontal mill 110 rotates around a drum axis 115. Collectively, all drums 111 are contained within an area defined by milling chamber 913, which includes side plates 9131 and moldboard 9132. Controller 160 sends a signal to actuator 174, which adjusts drum height. Controller 160 sends a signal which starts or stops drum motor 870, independently spinning each drum as required. Drum motor 870 may be powered by electric, hydraulic, pneumatic, or mechanical linkage to the main machine power unit. Drum legs 910, aligned with drum actuator 974, are reinforced with support arm 911, which pivots about hinge point 912.

FIG. 9B shows the front section view of multiple horizontal mill 910, having multiple independently-adjustable drums 911 arranged in one row. In another embodiment, horizontal mill 910 may include drums arranged in two or more rows. Cut paths of drums 911 are created to remove the least amount of material while also fully removing minimum material removal volume 521.

FIG. 10A illustrates a side view of a full width

horizontal mill 1000 with one or more laterally sliding horizontal drums 1011 aligned in a row. Laterally sliding horizontal drums 1011 are individually mounted to individual sliding frames 1010 or collectively added to multi-drum sliding frame. Controller 160 adjusts drum 1011 height and horizontal location independently according to multiple tool paths 621.

Another embodiment replaces sliding horizontal drums 1011 with laterally sliding vertical drums, or a combination of both.

Collectively, all drums 1011 are contained within milling chamber 1013, which consists of side plates 1022 and moldboard 1023. Controller 160 sends a signal to actuator 1074, which adjusts drum height. Controller 160 sends a signal to adjust the lateral positioning of laterally sliding horizontal drum 1011. Controller 160 sends a signal which starts or stops drum motor 1070, independently spinning each drum as required. As illustrated, drum motor 1070 is in line with actuator 1074; however, it is contemplated and understood that other embodiments and configurations of drum motor 1070 may be employed. For example, drum motor 1070 may be powered by electric, hydraulic, pneumatic, or mechanical linkage to the main machine power unit. Similarly, drum motor 1070 may be, in some embodiments, contained within drum 1011 (and powered by, e.g., hydraulic lines running around the drum edge). In other embodiments, drum motor 1070 may be a chain drive running perpendicular to the drum axis, or even a drive shaft. These and other arrangements of the drum and drum motor may be beneficially utilized in connection with various embodiments described herein.

FIG. 10B shows the front section view of a full width

horizontal mill 1000 with laterally sliding horizontal drums 1011, each movable laterally on a sliding frame 1010. Cut paths of multiple horizontal mills 1011 are created to remove the least amount of material while also fully removing minimum material removal volume 521.

In another embodiment, sliding frames 1010 may be configured to permit forward/rearward travel of the multiple drums 1011 at a velocity which differs from overall machine velocity and direction of work 170. Such forward/rearward travel may be provided in addition to, or in lieu of, lateral travel.

It will be understood that various aspects or details of the disclosure may be changed without departing from the scope of the disclosure. It is not exhaustive and does not limit the claimed disclosures to the precise form disclosed. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation. Modifications and variations are possible in light of the above description or may be acquired from practicing the disclosure. The claims and their equivalents define the scope of the disclosure. Moreover, although the techniques have been described in language specific to structural features and/or methodological acts, it is to be understood that the appended claims are not necessarily limited to the features or acts described. Rather, the features and acts are described as example implementations of such techniques.

Conditional language such as, among others, “can,” “could,” “might” or “may,” unless specifically stated otherwise, are understood within the context to present that certain examples include, while other examples do not include, certain features, elements and/or steps. Thus, such conditional language is not generally intended to imply that certain features, elements and/or steps are in any way required for one or more examples or that one or more examples necessarily include logic for deciding, with or without user input or prompting, whether certain features, elements and/or steps are included or are to be performed in any particular example. Conjunctive language such as the phrase “at least one of X, Y or Z,” unless specifically stated otherwise, is to be understood to present that an item, term, etc. may be either X, Y, or Z, or a combination thereof.

Furthermore, the description of the different examples of implementations has been presented for purposes of illustration and description, and is not: intended to be exhaustive or limited to the examples in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. Further, different examples of implementations may provide different features as compared to other desirable examples. The example, or examples, selected are chosen and described in order to best explain the principles of the examples, the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various examples with various modifications as are suited to the particular use contemplated.

It will also be understood that various aspects or details of the invention may be changed without departing from the scope of the invention. It is not exhaustive and does not limit the claimed inventions to the precise form disclosed. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation. Modifications and variations are possible in light of the above description or may be acquired from practicing the invention. The claims and their equivalents define the scope of the invention.

The description of the different examples of implementations has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the examples in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. Further, different examples of implementations may provide different features as compared to other desirable examples. The example, or examples, selected are chosen and described in order to best explain the principles of the examples, the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various examples with various modifications as are suited to the particular use contemplated.

Complex Geometry Pavement Milling

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