Compactor System And Methods

Abstract

A compactor system includes a tipped drum having a plurality of tips, and a drum axle rotatably coupling the tipped drum to a frame. The compactor system further includes a sensor configured to sense a parameter indicative of a height of the drum axle above a surface of a material substrate, and an electronic control unit configured to output a compaction progress signal responsive to inputs from the sensor. Related methods of preparing a work area with a compactor system, and determining a compaction state of a material substrate, are also disclosed.

Description

TECHNICAL FIELD

The present disclosure relates generally to compactor systems and material compaction strategies, and relates more particularly to monitoring compaction progress by way of sensor data indicative of axle height of a tipped drum compactor.

BACKGROUND

A wide variety of different compacting systems are used in the preparation of earthen fill and compaction of other materials in civil engineering projects such as construction, road building and landfill activities. Self-propelled two-wheel and four-wheel compactors, tow-behind systems, and others are well known and widely used. Engineers have recognized for many years that the capacity of substrate materials to remain stable over time, support loads or serve as a barrier to liquids, as well as other properties, can depend in significant part upon compacting a given material to a certain compaction state. Simply passing a compactor over a work area will tend to increase the relative compaction state of the resident material. Thus, to some extent compactor coverage is one metric which has been used to enable an operator or site manager to estimate that a target compaction state has been achieved. While knowing how many times a compactor has traversed a given region of a work area can be useful information, many modern compaction projects require a more sophisticated understanding of the actual compaction state or compaction response of material.

Different materials may have a widely varying “compaction response” or change in properties resulting from coverage with a compactor machine. For instance, sandy or granular soils tend to exhibit a different change in relative compaction state than do clayey soils each time a compactor is passed over a given region. Local variations in material composition or moisture content within a work area, as well as changes in moisture content over time can also result in non-uniformity in compaction state even where compactor coverage has been uniform. In addition to project success depending upon satisfaction of compaction specifications, payments or bonuses to contractors can also be based on the quality and timeliness of a particular compaction job. Like many heavy-duty construction machines, compactors can be quite expensive to operate, and thus unnecessary work or remedial actions create undesired expense. For the foregoing and other reasons, there is often a premium on machines and/or operators capable of doing enough work with a compactor system to meet a predefined goal, but avoiding any substantial wasted effort.

To this end, various strategies are known which provide information to an operator or site manager which is indicative of a compaction state of material, apart from merely how many times the material has been traversed by a compactor. Nuclear density gauges are used to evaluate density of substrate material after coverage with a compactor. While such mechanisms are fairly precise, density of compacted material alone may not be the factor of most interest. Moisture content can affect density measurements, and may change over time due to precipitation and evaporation, resulting in material presumed to be ideally compacted based on density measurements, but which in fact is not. Measurements of the depth of ruts left by machines traveling over a compacted surface or similar tests are also used, and in some jurisdictions serve as a primary compaction specification. Rut depth measurements, however, often require manual activities by personnel at a work site and/or only provide a snapshot of the compaction state of the material at one location. Moreover, forming ruts over the entire surface of a work area with a machine having certain specifications, and then measuring rut depth, is impractical. So called “walk-out” testing has also been widely used, in which a tipped drum compactor is driven onto a compacted surface and visual inspection used to determine whether or not the drum tips substantially penetrate a compacted surface. If not, the compacted material may be roughly estimated to be sufficiently compacted.

Still other strategies leverage the difference between an actual radius of a compacting drum and an effective rolling radius. One example of such an approach is disclosed in commonly owned U.S. Pat. No. 7,428,455 to Corcoran. Indicating compaction by effective rolling radius has been shown to be a viable, and in some instances superior, approach as compared with other techniques. There remains room for still further improvements, however.

SUMMARY OF THE DISCLOSURE

In one aspect, a method of preparing a work area with a compactor system having a tipped drum includes compacting a material substrate within the work area at least in part by moving the compactor system such that an outer surface of the tipped drum rotates in contact with the material substrate. The method further includes supporting the tipped drum on radially projecting drum tips such that the outer surface of the tipped drum is elevated from the compacted material substrate, and sensing a parameter indicative of an axle height of the tipped drum relative to a surface of the compacted material substrate during supporting the tipped drum. The method further includes outputting a compaction progress signal responsive to the sensed parameter.

In another aspect, a method of determining a compaction state of a material substrate includes sensing a parameter indicative of an axle height of a compactor having a tipped drum supported by a plurality of radially projecting drum tips upon a surface of a compacted material substrate, and receiving sensor data associated with the sensed parameter at an electronic control unit. The method further includes outputting a signal from the electronic control unit which is indicative of compaction state of the compacted material substrate, responsive to the sensor date.

In still another aspect, a compactor system includes a frame, and a tipped drum defining an axis of rotation and having a plurality of tips radially projecting from a cylindrical outer drum surface. The compactor system further includes a drum axle rotatably coupling the tipped drum to the frame, and a sensor configured to sense a parameter indicative of a height of the drum axle above a surface of a material substrate, and an electronic control unit. The electronic control unit is coupled with a sensor and configured to output a compaction progress signal responsive to inputs from the sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side diagrammatic view of a compactor system, according to one embodiment;

FIG. 2 is a side diagrammatic view of a tipped compactor drum supported upon a substrate, at two different locations;

FIG. 3 is a pictorial view of a display illustrating mapped compaction state, according to one embodiment; and

FIG. 4 is a flowchart illustrating portions of a control/monitoring routine, according to one embodiment.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown a compactor system 10 including a compactor 11, according to the present disclosure. Compactor system 10 is shown in the context of a self-propelled four drum compactor having a frame 12 which includes a front frame unit 14 and a back frame unit 16, coupled together at an articulation joint 18. An operator cab 20 is mounted upon frame 12 and includes an operator control station 21 from where an operator can control activities of compactor system 10, as further described herein. Compactor 11 may be equipped with an implement 36 such as a blade or the like for purposes well known in the art. In FIG. 1, two tipped drums, including a right front drum 24 and a right back drum 22 are shown, each of which includes a plurality of tips 26 projecting from a cylindrical outer drum surface 28. It should be understood that compactor 11 may also include a left front drum and a left back drum, which are hidden from view in the FIG. 1 illustration. Tips 26 may be any of a wide variety of known drum trip configurations, including conventional sheep's foot, pad foot, or some other tip design, and it should be understood that the present disclosure is applicable to tipped drum compactor systems without limitation to any particular tip style.

In a similar vein, it should be understood that the machine configuration shown in FIG. 1 is illustrative only. A wide variety of tipped drum compacting systems may be advantageously designed and operated in accordance with the teachings set forth herein. For example, rather than a four drum self-propelled compactor system, compactor system 10 might include a tow-behind tipped drum compactor, a single drum compactor having a set of rearwardly mounted ground engaging propulsion wheels, or still another type of compactor. Each of tipped drums 22 and 24 may be rotatably coupled with frame 12 by way of a drum axle, one of which is shown and identified via reference numeral 30 in connection with tipped drum 22, having an axis of rotation A. Compactor system 10 is shown in FIG. 1 supported upon a material substrate Z having a surface S. Substrate Z may include soil, landfill trash, or another type of material, and tipped drums 22 and 24 are positioned such that cylindrical outer surface 28 contacts surface S, and tips 26 penetrate through surface S into the material of substrate Z. As will be further apparent from the following description, compactor system 10 may be uniquely configured to monitor and/or control compacting activities within a work area, and enable an operator or site manager, or automated system to control compactor system 10 such that target compaction specifications for a particular project are met and unnecessary effort is reduced or avoided.

To this end, compactor system 10 may include a control system 39 having a sensor 32 configured to sense a parameter indicative of a height of drum axle 30 above surface S. Sensor 32 may include a signal transducer configured to sense a transmitted signal, or component of a transmitted signal, reflected by surface S. In the illustrated embodiment, a single sensor 32 is shown coupled with and resident on frame 12. In other embodiments, additional sensors such as a front sensor (not shown) associated with front drum 24 might be used, or individual sensors located in proximity to each compacting drum for a total of four sensors. In one practical implementation strategy, sensor 32 may be located at or close to a center point of axle 30, at or close to a longitudinal centerline of frame 12. The transmitted signal may include a sonic signal, an RF signal, or a laser signal, for example, transmitted via a transmitter 34 mounted with sensor 32 in a housing 38. Sensor 32 may include a non-contact sensor such as the examples noted above. In other embodiments, a gauge wheel, skid or the like might be coupled with frame 12, and configured to change vertical position responsive to changes in axle height of axle 30 above surface S, and output a signal indicative of axle height and/or changes therein. A gauge wheel or the like might be understood as a direct mechanical sensing mechanism, in contrast to the non-contact sensing mechanisms noted above. In still other embodiments, information received from a global positioning system (GPS) or a local positioning system might also be used in monitoring axle height. Control system 39 may further include a position sensor 46 resident on compactor 11 which receives global or local positioning data, potentially used in axle height monitoring as mentioned above, but also used in establishing and tracking geographic position of compactor 11 within a work area. In one embodiment, further described herein, data received via position sensor 46 may be linked with data received from sensor 32 to map position data of compactor system 10 received via sensor 46 to axle height data received from sensor 32, for purposes which will be apparent from the following description.

Control system 39 may further include an electronic control unit 40 which includes at least one data processor 42, and a computer readable memory 44. Electronic control unit 40 may be coupled with sensor 32, and also with position sensor 46, and may be configured to output a signal responsive to inputs from sensor 32, as further described herein. A display 48 also coupled with electronic control unit 40 may be positioned at operator control station 29 to display various data to an operator relating to axle height, machine position, relative compaction state, or still other parameters. In the illustrated embodiment, control system 39 is resident on compactor 11. It should be appreciated that in other embodiments, control system 39 or parts thereof might be located remotely from compactor 11, such as at an offsite management office. In such an embodiment, data gathered relating to position of compactor 11 and axle height data might be transmitted to a remote computer, processed, and control commands sent to compactor 11 to direct an operator to take or forego certain actions, or to direct compactor 11 to autonomously take or forego certain actions. Taking actions in response to the axle height data and position data might include commencing travel of compactor 11 within a work area, stopping travel of compactor 11 within a work area, or redirecting or otherwise changing a planned compactor travel path or coverage pattern. Computer readable memory 44 may store computer executable code comprising a control algorithm for determining a relative compaction state of material substrate Z and/or determining a change in relative compaction state, responsive to inputs from sensor 32, and the same or another algorithm for controlling or directing operation of compactor 11. In one embodiment, the determination of relative compaction state or changes therein may be based at least in part upon a difference between an axle height of axle 30 when material substrate Z is at a relatively lower compaction state and an axle height of axle 30 when material substrate Z is at a relatively greater compaction state.

Referring now also to FIG. 2, those skilled in the art will be familiar with the difference between the way a tipped drum may interact with a material substrate at a relatively uncompacted stated versus a relatively more compacted state. In particular, when a tipped drum compactor initially commences compacting a material substrate, the drum tips will typically sink into the material such that the outer drum surface of the tipped drum contacts the material substrate and compacts the same. Meanwhile, penetration of the drum tips into the material will also compact the material, from the bottom up. As compaction progresses, typically via additional compactor passes over a particular area of a work area, an increased compaction of the material substrate may result in the drum tips penetrating the material less at each successive pass, such that the outer drum surface is actually elevated from a surface of the compacted material substrate. The present disclosure leverages this phenomenon and an associated change in axle height, to determine a relative compaction state of the material and/or changes therein, enabling the monitoring of compaction progress.

In FIG. 1, compactor 11 is shown as it might appear during an initial or early stage of compacting substrate Z where outer surface 28 contacts surface S, such as during a first pass across surface S. In FIG. 2 tipped drum 22 is shown supported on substrate Z as it might appear after compactor 11 has performed one or more initial passes, typically multiple passes, across surface S to compact substrate Z to a state at which outer surface 28 is elevated from surface S. It may thus be noted that in FIG. 1, axle 30 is elevated a first, relatively lesser distance from surface S, whereas in FIG. 2 axle 30 is elevated a second, relatively greater distance from surface S. In FIG. 2, axle height is illustrated via reference letter D. One way in which the change in axle height may be leveraged to determine a change in relative compaction state is by comparing axle height D with a radius R of a circle defined by outer surface 28 about axis A. For instance, when compactor 11 is operating under conditions similar to those depicted in FIG. 1, a height of axle 30 above surface S within a footprint of drum 22 may be equal to radius R. When compactor 11 is operating under conditions similar to those depicted in FIG. 2, axle height may be relatively greater than radius R. Electronic control unit 40 may, in one embodiment, be configured to compare axle height D with radius R or a value indicative of radius R, and output a signal responsive to the difference. Since inputs received by electronic control unit 40 from sensor 32 are indicative of axle height, the outputted signal from electronic control unit 40 may also be understood as responsive to the sensor inputs. In further embodiments or extensions of such an embodiment, electronic control unit 40 may output a signal based on an arithmetic difference between axle height D and radius R. When the arithmetic difference is equal to or greater than a predefined threshold, it may be determined that material substrate Z has been compacted part way or all the way to a specified target compaction state.

As discussed above, increasing the relative compaction state of substrate Z may transition compactor 11 from a state in which outer surface 28 contacts surface S during rotating tipped drum 22 in contact with surface S, to a state in which outer surface 28 is elevated from surface S during rotating tipped drum 22 in contact with surface S. Accordingly, the signal outputted from electronic control unit 40 responsive to inputs from sensor 32 may be indicative of a relative compaction state or change in relative compaction state of the material comprising substrate Z. Where determining or estimating relative compaction state alone is desired, information pertinent to the determination or estimation, such as the weight of compactor 11, surface areas and numbers of drum tips 26, geometry of drum tips 26, and other factors such as soil composition and moisture, are known to those skilled in the art or may be determined empirically. Where determining or estimating a change in relative compaction state is desired, a change in determined axle height between one compactor pass and a next compactor pass may be empirically related via prior field or laboratory testing or simulation to a change in relative compaction state, for a particular compactor system. Further, a simple determination that axle height D is greater than radius R may be sufficient to determine that compaction progress is being made. It may further be appreciated that no change in axle height will typically be detected until substrate Z has been compacted sufficiently to elevate outer surface 28 above surface S. Monitoring of axle height may take continuously during operating compactor system 10, periodically, or only after detection of some trigger or satisfaction of predetermined conditions. For example, in one strategy axle height may be continuously monitored throughout a compacting procedure. In another strategy, axle height may be monitored only after, say, three compactor passes have occurred, while in still another strategy axle height might be monitored during a separate test run after a site manager has estimated it is likely that the project is finished but wishes to obtain assurance that specifications are satisfied. In any of these examples, as well as others contemplated herein, the signal outputted from electronic control unit 40 responsive to inputs from sensor 42 may include a compaction progress signal, indicating that a predefined increase in relative compaction state or satisfaction of predefined specifications has occurred. Thus, the term “compaction progress” as used herein may be understood to mean that some identifiable interim goal or end goal has been achieved.

It may also be noted from FIG. 2 that tipped drum 22 is shown at two different locations, the leftmost being in phantom, upon substrate S. As alluded to above, in one embodiment control system 39 might be configured to periodically sense axle height when compactor 11 is operating, such as at the two locations shown in FIG. 2. Monitoring of axle height may alternatively be essentially continuous such that axle height measurements are determined while rotating tipped drum 22 in contact with material substrate Z throughout a compaction project. In either case, control system 39 may be configured to link position data received via position sensor 46 with the axle height data, such that relative compaction state may be mapped to geographic coordinates within a work area. Axle height at the leftmost location of drum 22 in FIG. 2 might include a first distance, whereas axle height at the rightmost location might include a second distance, due to a local variation in compaction response, and the different axle heights or associated compaction state can be mapped to particular regions of the work area.

In one further embodiment, mapping relative compaction state may be based upon a length coordinate and a width coordinate such that a work area can be divided into cells, for example based on relative compaction state thereof. Referring also now to FIG. 3, there is shown a pictorial view of display 48 illustrating graphical information which might be displayed to an operator or manager at a particular work site. In FIG. 3, a work area X is shown in the process of being prepared and having been compacted by at least one pass via compactor system 10, and where compactor system 10 is performing an additional pass over work area X. One strategy for dividing work area X into cells includes setting a cell width coordinate W which is approximately equal to a width of compactor 11, and setting a length coordinate L for each of the cells which may vary based upon average axle height, or determined relative compaction state. Another way to understand the illustration in FIG. 3 is that compactor system 10 may proceed across a work area, and as axle height data is gathered, control system 39 may group together areas in which the axle height data indicates a similar relative compaction state, or similar change in relative compaction state as compared with proceeding compactor passes. Thus, length coordinate L may be mutable whereas width coordinate W may be fixed. Alternatively, a fixed cell width and fixed cell length might be used. In the FIG. 3 illustration, displaying horizontal lines within the individual cells may indicate that material substrate Z is at a level=0 and has not been compacted sufficiently to elevate outer surface 28 from surface S. Intersecting diagonal lines indicates cells where material substrate Z has compacted to a level=1, sufficient to elevate surface 28 a first distance from surface S, signifying some compaction progress but not achievement of compaction specifications. Non-intersecting diagonal lines indicate cells at a level=2, where material substrate Z has compacted sufficiently such that outer surface 28 is elevated a second, relatively greater distance, signifying achievement of compaction specifications. A variety of other information display strategies might be used within the present context. For instance, a fixed grid/cell system for the work area might be used. A planned compactor travel path might also be displayed, and updated if axle height data indicates that certain regions need more work or that certain regions are finished. In one embodiment, a default compactor travel path may be based on uniform coverage, but changed upon discovery of differentially compacting regions with a work area. Any of the information or graphics displayed on display 48 may be generated or updated responsive to the signal outputted by electronic control 40 in response to inputs from sensor 32.

INDUSTRIAL APPLICABILITY

Referring now to FIG. 4, there is shown a flowchart 100 illustrating certain steps in a control and monitoring process whereby a work area such as work area X is prepared via compactor system 10, or another compactor system as contemplated herein. The process of flowchart 100 may start at step 110, and may proceed to step 120 at which compactor system 10 is operated. Commencing operation of compactor system 10 may include compacting material substrate Z within work area X via moving compactor system 10 such that outer surface 28 of tip drum 22 rotates in contact with material substrate Z. This initial step of operating compactor system 10 may include performing one or more, and typically at least two, passes over all of work area X.

Subsequently, operating compactor system 10 may also include operating compactor system 10 where tipped drum 22 is supported on radially projecting drum tips 26 such that outer surface 28 is elevated from compacted material substrate Z. This step may occur during subsequent passes over work area X, such as a third, fourth, or fifth pass, depending upon material type or condition, compactor specifications, and other factors. Prior to or during operating compactor system 10 such that tipped drum is supported on drum tips 26, a signal may be transmitted from transmitter 34 toward surface S. The transmitted signal may be reflected by surface S, and sensor 32 may sense the transmitted and reflected signal or components thereof at step 140. From step 140, the process may proceed to step 150 wherein electronic control unit 40 may calculate axle height, estimate axle height, or otherwise determine a value indicative of axle height, in the manner described herein. From step 150, the process may proceed to step 160 at which electronic control unit 40 may output a compaction progress signal as described herein. In response to the compaction progress signal, compactor 11 may be directed via commands generated by electronic control unit 40 or another computer, or a site operator, to continue as planned, change the compactor coverage plan, cease operation, or take some other action. Such commands may be displayed in an operator format on display 48, or communicated via an alarm or still another mechanism. From step 160, the process may proceed to finish at step 170. Receipt of position data, linking the position data with the compaction progress signal or otherwise with the axle height data, and displaying information to an operator or other party may occur during executing the routine of flowchart 100, in parallel, or subsequently.

Those skilled in the art will be familiar with conventional tests of relative compaction state and compaction response of material. The above described examples of nuclear density measurements, effective rolling radius, rut depth measurements, and walk-out tests, have all found applicability in various environments over the years. The present disclosure presents an alternative strategy, improving over conventional approaches in at least certain environments. The ability to sense axle height directly enables an operator or site manager to continuously or periodically monitor compaction progress in a manner not available, or at least not practicable with many traditional strategies. Nuclear density measurements may be time consuming, require specialized equipment, and may even require specially trained technicians. Walk-out tests typically require visual observation of drum tip penetration. Not only is visual observation inherently unreliable and qualitative only, it is typically necessary to halt compactor operation to allow an observer to inspect the drum tip penetration. Further, since walk-out by definition is restricted to observations at one location at a time, trends in drum tip penetration over time and variance in drum tip penetration among different regions of a work area, limit the extent and practicability of using walk-out to evaluate ongoing compaction progress or take action based on non-uniformity in compaction state of material within a work area. The present disclosure can enable snapshot determinations of relative compaction state, an overall picture of how a work area is responding to compaction efforts, and analysis of trends in compaction response of material.

With regard to monitoring compaction state by way of effective rolling radius, while such strategies have been widely and advantageously applied, and could even be integrated with the teachings of the present disclosure within a single system, effective rolling radius may in at least certain instances require moving the associated compactor a travel distance equal to or greater than one full circumference of the compacting drum. The present disclosure allows compaction state to be mapped at a relatively high map resolution, in which a length of cells within a work area can be less than one full drum circumference. Moreover, implementing effective rolling radius approaches in four-wheel compactors, while theoretically possible, may be complex from the standpoint of processing data from the calculations for multiple rotating drums, or for other reasons. Rut depth measurements and similar strategies leverage phenomena different from the penetration of multiple drum tips into a substrate, and like other conventional strategies discussed herein, do not generally enable any robust determination or estimation of the shear strength of compacted material. The present disclosure may be applied to determine quantitative or qualitative measurements relating to shear strength, based upon known machine parameters and the extent to which drum tips penetrate into a compacted material substrate.

The present description is for illustrative purposes only, and should not be construed to narrow the breadth of the present disclosure in any way. Thus, those skilled in the art will appreciate that various modifications might be made to the presently disclosed embodiments without departing from the full and fair scope and spirit of the present disclosure. Other aspects, features and advantages will be apparent upon an examination of the attached drawings and appended claims.

Claims

1. A method of preparing a work area with a compactor system having a tipped drum comprising the steps of:

compacting a material substrate within the work area at least in part by moving the compactor system such that an outer surface of the tipped drum rotates in contact with the material substrate;

supporting the tipped drum on radially projecting drum tips such that the outer surface of the tipped drum is elevated from the compacted material substrate;

sensing a parameter indicative of an axle height of the tipped drum relative to a surface of the compacted material substrate during supporting the tipped drum; and

outputting a compaction progress signal responsive to the sensed parameter.

2. The method of claim 1 wherein the tipped drum is rotatably coupled with a frame of a self-propelled compactor machine, and wherein the step of sensing includes sensing the parameter by way of a sensor resident on the compactor machine.

3. The method of claim 2 further comprising a step of transmitting a signal from a transmitter resident on the compactor machine toward the surface of the compacted material substrate, and wherein the step of sensing includes sensing the transmitted signal reflected by the surface.

4. The method of claim 2 wherein the step of supporting includes supporting the tipped drum during rotating the tipped drum in contact with the compacted material substrate.

5. The method of claim 2 further comprising the steps of receiving position data of the compactor machine, and linking the received position data with the compaction progress signal.

6. The method of claim 5 wherein the compaction progress signal includes a signal indicative of a relative compaction state of the material substrate, and wherein the step of linking further includes mapping relative compaction state to geographic coordinates defining a region of the work area.

7. The method of claim 6 wherein mapping relative compaction state further includes mapping relative compaction state at a map resolution based on a width coordinate, and a length coordinate which is equal to less than one full circumference of the outer surface of the tipped drum.

8. The method of claim 1 further comprising the steps of receiving data of the sensed parameter, determining a value indicative of the axle height responsive to the data, and comparing the determined value with a value indicative of the radius of a circle defined by the tipped drum about an axis of rotation of the tipped drum, and wherein the step of outputting takes place responsive to a difference between the compared values.

9. A method of determining a compaction state of a material substrate comprising the steps of:

sensing a parameter indicative of an axle height of a compactor having a tipped drum supported by a plurality of radially projecting drum tips upon a surface of a compacted material substrate;

receiving sensor data associated with the sensed parameter at an electronic control unit; and

outputting a signal from the electronic control unit which is indicative of compaction state of the compacted material substrate, responsive to the sensor data.

10. The method of claim 9 wherein the step of sensing further includes sensing the parameter during moving the compactor within the work area.

11. The method of claim 9 further comprising the steps of receiving position data of the compactor, and linking the position data with the sensor data, and wherein the step of receiving sensor data further includes receiving sensor data for a plurality of separate regions of the work area.

12. The method of claim 9 wherein receiving sensor data for the plurality of test regions further includes receiving sensor data from a non-contact sensor resident on the compactor.

13. The method of claim 12 wherein the electronic control unit is configured to compare a value indicative of the axle height with a reference value indicative of the radius of a circle defined by the tipped drum about an axis of rotation thereof, and further configured to output the signal responsive to a difference between the compared values.

14. A compactor system comprising:

a frame;

a tipped drum defining an axis of rotation and having a plurality of tips radially projecting from a cylindrical outer drum surface;

a drum axle rotatably coupling the tipped drum to the frame;

a sensor configured to sense a parameter indicative of a height of the drum axle above a surface of a material substrate; and

an electronic control unit coupled with the sensor, the electronic control unit being configured to output a compaction progress signal responsive to inputs from the sensor.

15. The compactor system of claim 14 wherein the electronic control unit is configured to determine a value indicative of the height of the drum axle responsive to the inputs, and further configured to compare the determined value with a reference value indicative of the radius of a circle defined by the tipped drum about the axis of rotation.

16. The compactor system of claim 15 further comprising a transmitter coupled with the frame and configured to transmit a signal toward the surface of the compacted material substrate.

17. The compactor system of claim 16 further comprising a self-propelled compactor which includes the frame and the tipped drum, and a position sensor coupled with the electronic control unit, and wherein the transmitter, sensor, position sensor and electronic control unit are resident on the self-propelled compactor.