Title:
Towed compaction determination system utilizing drawbar force
Kind Code:
A1


Abstract:
A compaction determination system for monitoring the compaction in a material produced by a rotary device as the rotary device is towed over the material is disclosed. The compaction determination system may have a force sensor associated with a drawbar used to tow the rotary device, the force sensor being configured to sense a force transmitted to the rotary device via the drawbar. The compaction determination system may further have a controller in communication with the force sensor. The controller may be configured to determine a compaction of the material produced by the rotary device based on the sensed force.



Inventors:
Corcoran, Paul Thomas (Washington, IL, US)
Application Number:
11/790205
Publication Date:
10/30/2008
Filing Date:
04/24/2007
Assignee:
CATERPILLAR INC.
Primary Class:
International Classes:
E01C19/23
View Patent Images:



Primary Examiner:
MAWARI, REDHWAN K
Attorney, Agent or Firm:
CATERPILLAR/FINNEGAN, HENDERSON, L.L.P. (901 New York Avenue, NW, WASHINGTON, DC, 20001-4413, US)
Claims:
What is claimed is:

1. A compaction determination system for monitoring the compaction in a material produced by a rotary device as the rotary device is towed over the material, comprising: a force sensor associated with a drawbar used to tow the rotary device, the force sensor being configured to sense a force transmitted to the rotary device via the drawbar; and a controller in communication with the force sensor, the controller being configured to determine a compaction of the material produced by the rotary device based on the sensed force.

2. The compaction determination system of claim 1, wherein the controller determines a higher compaction of the material when the sensed force is lower, and determines a lower compaction of the material when the sensed force is higher.

3. The compaction determination system of claim 1, further including an incline sensor configured to sense an incline in a surface of the material, wherein the controller is in communication with the incline sensor and configured to determine the compaction of the material produced by the rotary device based further on the sensed incline.

4. The compaction determination system of claim 3, wherein the controller determines a higher compaction for a given sensed force when a decline is sensed, and determines a lower compaction for the given sensed force when an incline is sensed.

5. The compaction determination system of claim 1, wherein the controller is further configured to display within the mobile machine a representation of the determined material compaction.

6. The compaction determination system of claim 1, wherein the controller determines compaction by comparing the sensed force to a target value.

7. The compaction determination system of claim 1, wherein the controller determines compaction by comparing the force sensed during a current compaction pass to a force sensed during a previous compaction pass.

8. A method of determining compaction, comprising: towing a rotary device over a material to compact the material; sensing a force of the towing; and determining an amount of compaction created by the rotary device based on the sensed force.

9. The method of claim 8, wherein the amount of compaction is determined to be higher when the sensed force is lower, and the amount of compaction is determined to be lower when the sensed force is higher.

10. The method of claim 8, further including sensing an incline in the surface of the material, wherein the amount of compaction is determined based further on the sensed incline.

11. The method of claim 10, wherein the amount of compaction is determined to be higher for a given sensed force when a decline is sensed, and the amount of compaction is determined to be lower for the given sensed force when an incline is sensed.

12. The method of claim 8, further including visually displaying a representation of the determined material compaction.

13. The method of claim 8, wherein determining includes comparing the sensed force to a target value.

14. The method of claim 8, wherein determining includes comparing the force sensed during a current compaction pass to a force sensed during a previous compaction pass.

15. A surface compaction system, comprising: a machine; a rotary device pulled by the machine over a material to compact the material; a drawbar connecting the rotary device to the machine; a force sensor associated with the drawbar being configured to sense a force transmitted from the machine to the rotary device via the drawbar; an inclinometer configured to sense an incline in a surface over which the rotary device is operating; and a controller in communication with the force sensor and the inclinometer, the controller being configured to determine a compaction of the material produced by the rotary device based on the sensed force and the sensed incline.

16. The surface compaction system of claim 15, wherein the controller determines a higher compaction of the material when the sensed force is lower, and determines a lower compaction of the material when the sensed force is higher.

17. The surface compaction system of claim 15, wherein the controller determines a higher compaction for a given sensed force when a decline is sensed, and determines a lower compaction for the given sensed force when an incline is sensed.

18. The surface compaction system of claim 15, wherein the controller is further configured to display within an operator station of the machine a representation of the determined material compaction.

19. The surface compaction system of claim 15, wherein the controller is configured to determine compaction by comparing the sensed force to a target value.

20. The surface compaction system of claim 15, wherein the controller is configured to determine compaction by comparing the force sensed during a current compaction pass to a force sensed during a previous compaction pass.

Description:

TECHNICAL FIELD

The present disclosure relates generally to a compaction determination system, and more particularly, to a system for determining material compaction levels based on the drawbar force of a towed compactor.

BACKGROUND

Compaction machines are utilized in the construction of road beds, pavements, foundations, dams, runways, landfills, and other projects. In order to ensure that these projects meet required standards of load bearing, strength, durability, space, and permeability, the materials used in the construction process must be sufficiently compacted. Thus, tight control over the compaction process is required.

One way to control the compaction process is to periodically measure a level of compaction resulting from the process as the project progresses. That is, if a low compaction level is measured, additional compaction is provided until a stipulated level of compaction is attained. Common ways to measure compaction levels include impacting the material surface and measuring an indentation resulting from the impact, moving a tipped roller over the surface and measuring a distance off of the surface that the roller raises as a result of tip penetration being less than tip length, penetrating a surface with a predefined instrument and force and then measuring the penetration depth, and measurements of the density of a compacted layer of material with devices such as a nuclear density gauge. However, each of these methods have associated negative aspects such as cost, destruction of the finished surface, excessive time consumption, and being labor intensive.

One way to quickly and economically determine soil hardness is disclosed in U.S. Pat. No. 6,041,582 (the '582 patent) issued to Tiede et al. on Mar. 28, 2000. The '582 patent discloses a faring system for performing work on an agricultural field, while compaction conditions of the field are being recorded. The farming system includes an agricultural tractor equipped with ground penetrating farm tools such as a plow, an “S” shaped tine, a coil shank tool, or a sub-soil ripper. The tractor pulls the tool through the soil by way of a drawbar or hitch. A strain gauge is connected to the drawbar and, based on a measurement of force imparted by the tools to the soil provided by the strain gauge, soil compaction or hardness of the tilled field is calculated and recorded. From this data, a map is generated that shows varying compaction or hardness of the field, which can be utilized to effect farming practices such as tillage depth, fertilizing, seeding, watering, and the application of insecticides and herbicides.

Although the faring system of the '582 patent may provide a quick and economical way to determine compaction of an agricultural field, its accuracy and use may be limited. Specifically, because the only input is drawbar force, an incline or decline could significantly affect the measured force, resulting in an inaccurate representation of soil compaction or hardness at a particular location. For example, when operating the tractor up an incline, the drawbar strain gauge may read high levels of force and associate this force with high compaction, even though a significant portion of the measured force may be due to gravity acting on the farm tool. Similarly, when operating the tractor down all incline, the drawbar strain gauge may read low levels of force and associate this force with low compaction, even though gravity may again be acting on the farm tool to lessen the measurement. Further, because the drawbar force measured by the strain gauge is related to the force required to move a tool through soil, only applications allowing a disruption of the surface may benefit from the farming system. That is, when creating a roadway, a measurement system that requires a tool be ripped through the surface of the roadway may be undesirable.

The disclosed machine system is directed to overcoming one or more of the problems set forth above.

SUMMARY OF THE DISCLOSURE

In one aspect, the present disclosure is directed to a compaction determination system for monitoring the compaction in a material produced by a rotary device as the rotary device is towed over the material. The compaction determination system may include a force sensor associated with a drawbar used to tow the rotary device, the force sensor being configured to sense a force transmitted to the rotary device via the drawbar. The compaction control system may further include a controller in communication with the force sensor. The controller may be configured to determine a compaction of the surface produced by the rotary device based on the sensed force.

In another aspect, the present disclosure is directed to a method of determining compaction of a material. The method may include towing a rotary device over a material to compact the material. The method may also include sensing a force of the towing, and determining an amount of compaction created by the rotary device based on the sensed force.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic illustration of an exemplary disclosed machine;

FIG. 2 is a schematic and diagrammatic illustration of an exemplary disclosed control system for use with the machine of FIG. 1;

FIG. 3 is a flowchart depicting an exemplary disclosed method performed by the compaction determination system of FIGS. 1 and 2; and

FIG. 4 is flowchart depicting another exemplary disclosed method performed by the compaction determination system of FIGS. 1 and 2.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary embodiment of a machine 10. Machine 10 may be a mobile machine that perform some type of operation associated with an industry such as mining, construction, farming, or any other industry known in the art. For example, machine 10 may be an earth moving machine such as a track type tractor, a wheeled tractor, or any other suitable operation-performing machine. Machine 10 may include a power source 12 and at least one traction device 14. Machine 10 may also have an operator cabin 16 for manual control of power source 12 and traction device 14.

Power source 12 may embody an engine such as, for example, a diesel engine, a gasoline engine, a gaseous fuel powered engine such as a natural gas engine, or any other type of engine apparent to one skilled in the art. Power source 12 may alternatively embody a non-combustion source of power such as a fuel cell, a power storage device, an electric motor, or other similar mechanism. Power source 12 may be connected to drive traction device 14, thereby propelling machine 10.

Traction device 14 may include tracks located on each side of machine 10 (only one side shown). Alternately, traction device 14 may include wheels, belts or other known traction devices. Traction device 14 may transmit power from power source 12 to a ground surface.

Operator cabin 16 may contain operator controls and instruments that show various information on the operational status and modes of machine 10. For example, operator cabin 16 may, if desired, contain one or more interface devices 40 as described below in reference to FIG. 2.

Towed compactor 20 may include a drawbar 22 and a rotary compactor 24. Drawbar 22 may transmit force from machine 10 to rotary compactor 24. Rotary compactor 24 may be any rotary compactor known in the art, such as, for example, a smooth solid roller, a smooth hollow roller designed to be filled with ballast, or a tipped roller as shown. Rotary compactor 24 may compact material by using its weight to compress the material as rotary compactor 24 is towed over the material. Smooth rollers may provide compression from the top of the material, while tipped rollers may offer additional internal compression of the material due to the action of the tips as they penetrate the surface of the material. Rotary compactor 24 may additionally include a vibratory mechanism, if desired.

As illustrated in FIG. 2, machine 10 may include an attachment means 18, for attaching towed implements, such as towed compactor 20. Attachment means 18 may be any attachment means known in the art for attaching towed implements, such as, for example, a single-point hitch, a thee-point hitch, or an articulated joint. Attachment means 18 may also include a means known in the art (not shown) for providing electrical power to the towed implement and/or for two-way communication of control signals with towed implement 20.

A compaction determination system 28 may be associated with towed compactor 20 to determine an effectiveness of rotary compactor 24 based on a sensed force. Compaction determination system 28 may include a force sensor 32, an inclinometer 34, a position determining unit 38, a display 40a, an input 40b, and a controller 30. Controller 30 may receive communication from force sensor 32, inclinometer 34, position determining unit 38, and input 40b, and may send communication to display 40a responsive to the received communications.

Force sensor 32 may be associated with drawbar 22 to sense a force on towed compactor 20 and to generate a signal in response thereto. Force sensor 32 may be any force sensor commonly known in the art, such as, for example, a load link, a strain gauge, a transducer, or a load cell. Force sensor 32 may optionally include temperature compensation means commonly known in the art. For example, if force sensor 32 comprises strain gauges, the strain gauges may be configured in the form of a Wheatstone bridge to compensate for temperature-induced strain that may affect a reporting of the true drawbar force. The force reported by force sensor 32 may be indicative of the force required for machine 10 to pull towed compactor 20 over the material to be compacted when machine 10 is driven at a constant speed. A lower force reported by force sensor 32 may be indicative of a more compact material, while a higher force reported by force sensor 32 may be indicative of a less compact material.

Inclinometer 34 may be associated with drawbar 22 to sense an incline of towed compactor 20 and to generate a signal in response thereto. Alternatively, inclinometer 34 may be located on machine 10, if desired. The incline of towed compactor 20 may correspond with the slope of a surface over which towed compactor 20 is being towed. Alternatively, any other incline or slope sensor known in the art may be used. Controller 30 may use the incline of towed compactor 20 to calculate a resultant force on the drawbar associated with the incline, and subsequently to determine a true draft force on drawbar 22.

Position determining unit 38 may be associated with towed compactor 20 to determine the location of towed compactor 20. Alternatively, position determining unit 38 may be located on machine 10, if desired. Position determining unit 38 may be GPS based, laser based, or utilize any other technology commonly known in the art. Position determining unit 28 may be used by controller 30 to determine the location of towed compactor 20. Controller 30 may also or alternatively use position determining unit 38 to create a visual representation of the area to be compacted on display 40a and to show the location of the towed compactor 20 and the measured compaction in that area.

Display 40a may be located within the operator cabin 16 of machine 10 for viewing by the machine operator, or it may be an external display of the type commonly known in the art that is connected to a display port (not shown) of controller 30. Alternatively, display 40a may be in wireless communication with controller 30 and located elsewhere, including a location remote from towed compactor 20 and machine 10. Display 40a may comprise one or more cathode ray tubes (CRT), liquid crystal displays (LCD), plasma displays, or another device that is capable of displaying graphics and/or text. Display 40a may receive data from controller 30 and display the data for an operator of machine 10. Preferably, the displayed data may be relevant to the amount of compaction currently being generated, such as, for example, the force required to pull towed compactor 20 as it moves over the material. In addition, display 40a may indicate the location of towed compactor 20 in real time geographic coordinates. The displayed information may be graphical, text, tabular, numeric, and or any other format desired to effectively display the desired data.

Input 40b may be located on the towed compactor 20, within the operator cabin 16 of the machine 10 for use by the machine operator, or located remotely from towed compactor 20. Input 40b may include a wide variety of devices configured to input data into controller 30. For example, input device 40b may include a keyboard, a mouse, a joy-stick, a touch-screen, a disk drive, a magnetic card reader, a scanner, a CD drive, a DVD drive, a floppy disk drive, a memory stick input, a USB port, or any other suitable device. Input 40b may be used to input data such as results from proof compaction tests done on-site or in a laboratory, coordinates or other information describing the site to be compacted, weather information, information describing the type and condition of the material to be compacted, moisture content of the material to be compacted, desired measurement intervals, compactor width, compactor weight, compactor diameter or other parameters of rotary compactor 24, and date and time.

Controller 30 may embody a single microprocessor or multiple microprocessors that include a means for controlling an operation of the disclosed compaction determination system. Numerous commercially available microprocessors can be configured to perform the functions of controller 30 and it should be appreciated that controller 30 could readily embody a general machine microprocessor capable of controlling numerous machine functions, including sending and receiving control and data signals. Controller 30 may include a memory, a secondary storage device, a processor, wireless communication circuitry, external connection ports, and/or any other components for running an application. Various other circuits may be associated with controller 30 such as power supply circuitry, signal conditioning circuitry, solenoid driver circuitry, and/or other types of circuitry.

Controller 30 may be in communication with the various components of compaction determination system 28. In particular, controller 30 may be in communication with force sensor 32, inclinometer 34, position determining unit 38, display 40a, and input 40b via communication lines 44, 46, 48, 50, and 52, respectively. Controller 30 may receive and store in memory for subsequent display or calculation the signals from each of force sensor 32, inclinometer 34, and position determining unit 38. Controller 30 may receive and store data and commands from input 40b, and send signals to display 40a in response to received signals and calculations performed on data stored in the memory. Controller 30 may perform calculations on data received or stored in memory, and store the results of the calculations in memory for use in subsequent calculations, for display on display 40a, or for use in future compaction events.

Controller 30 may perform a variety of calculations. For example, using the incline reported by inclinometer 34 and the weight of towed compactor 20, which may be provided by the manufacturer or obtained by measurement, controller 30 may use Equation 1 below to calculate the incline force on drawbar 22 that is a result of an uphill or downhill incline of towed compactor 20:


IF=sin α*W (Equation 1)

where IF is the incline force, α is the angle of incline reported by inclinometer 34, and W is the weight of towed compactor 20. The angle of incline may have a positive value for uphill inclines, and a negative value for downhill inclines.

Controller 30 may then combine the calculated incline force with the drawbar force reported by force sensor 32 to determine the true draft force on drawbar 22 using Equation 2 below:


DF=SF−IF (Equation 2)

where SF is the drawbar force reported by force sensor 32 and DF is the true draft force. Controller 30 may store the results of these calculations in memory, and/or display them on display 40a.

Controller 30 may compare the results of calculations with target values or the results of prior calculations. For example, controller 30 may compare the draft force with a target draft force value stored in memory and/or supplied from the input 40b to determine whether the draft force is less than, equal to, or greater than the target draft force. If the calculated draft force is greater than the target draft force, additional passes of the area may be required. However, if the calculated draft is less than or equal to the target draft force, it can be concluded that compaction of that area is complete. Controller 30 may store the results of this calculation in memory, and/or display them on display 40a.

Alternatively, controller 30 may compare the draft force calculated for a current compacting pass of a specific area with the draft force calculated during a previous compacting pass of the same area, to determine the difference in draft force between the two passes using Equation 3 below:


ΔDF=DF(n−1)−DF(n) (Equation 3)

where ΔDF equals a differential draft force, DF(n) equals the draft force on a current pass, and DF(n−1) equals the draft force on a previous pass. Controller 30 may then determine whether this differential draft force is less than, equal to, or greater than a target differential draft force stored in memory. If the calculated differential draft force is greater than a target differential draft force, it may be concluded that the material has not yet been compacted as fully as desired, and additional passes of the area may be required. However, if the calculated differential draft force is less than or equal to a target differential draft force, it may be concluded that the material has reached the desired compaction level. Controller 30 may store the results of this calculation in memory, and/or display them on display 40a.

Controller 30 may allow for input of a desired measurement interval. The measurement interval may be defined by a measure of length, such as, for example, one foot, one meter, or a length equivalent to the circumference of rotary compactor 24. Controller 30 may use the measurement interval to virtually subdivide a compaction site area and define the resolution of the compaction determination. For example, controller 30 may use the measurement interval as a trigger for when to record and store data by receiving data from position determining unit 38 and comparing that data to the stored value of the measurement interval. When controller 30 determines that rotary compactor 24 has traveled a distance equal to the measurement interval, controller 30 may then take a snapshot of the data being recorded from force sensor 32, inclinometer 34, and position determining unit 38, and use the sensed values at the tine of that snapshot as values for that measurement interval. Alternatively, controller 30 may use any sampling technique known in the art to continuously record and store data while rotary compactor 24 traverses each measurement interval, and then calculate an average value of the data recorded and stored from force sensor 32, inclinometer 34, and position determining unit 38 as the values for the measurement interval while traversing that measurement interval.

The memory of controller 30 may contain a virtual map of an area to be compacted. The data contained in the virtual map may be received from the input of controller 30, or it may be generated by controller 30 during operation of machine 10. For example, the virtual map may contain the boundaries of the area to be compacted. The boundaries may be input by several methods, including, for example, by driving machine 10 around the boundary of an area and obtaining the coordinates of the boundaries from position determining unit 38, inputting the boundaries manually by taking measurements of the area, downloading the boundaries of the area from data obtained during previous compaction activities, or downloading from commercial mapping services. The virtual map may also contain data such as site topography, material composition, moisture content, and other environmental conditions.

The memory of controller 30 may also contain compaction data about the material derived from on-site or laboratory tests. The data may, for example, contain information about the desired compaction amount of the material and the draft force required to tow rotary compactor 24 over material in that compaction state. Such data may be used as target values for comparison with calculated values of the draft force.

Controller 30 may control display 40a to display a variety of compaction information in a variety of ways. For example, controller 30 may display the virtual map on display 40a and use information from position determining unit 38 to display a representation of towed compactor 20 on the virtual map. Controller 30 may update this display in real-time as towed compactor 20 is towed around the compaction area. Controller 30 may also display on display 40a data recorded during compaction, as well as results of compaction after controller 30 determines that compaction is complete or as compaction progresses.

FIG. 3 shows a flowchart illustrating an exemplary method of operating compaction determination system 28 in a first mode. In this first operating mode, compaction determination system 28 may determine compaction of a material based on a proof test performed on a small portion of a compaction site. A compaction specification for this method of operation may include a predetermined compaction level in any terms commonly known in the art, such as, for example, the desired density of a material, as determined by a Proctor test. To perform the proof test, towed compactor 20 may be used to fully compact a small test area of the compaction site. Compaction may be determined using any compaction verification method commonly known in the art to determine that the compaction of the material in the test area of the site satisfies the compaction specifications. After it is verified that the compaction in the test area is complete, towed compactor 20 may be towed once more over the compacted test area, and controller 30 may determine the draft force required to tow rotary compactor 24 over the compacted material. Controller 30 may then store this draft force for use as a target value to determine when the remaining portions of the compaction site are compacted to the specified level within a specified range, such as, for example, ±5%.

The embodiment illustrated in FIG. 4 shows a second operating mode of compaction determination system 28. In this second operating mode, compaction determination system 28 may determine compaction of a material based on a comparison of a calculated draft force on towed compactor 20 between successive passes. A compaction specification for this method of operation may specify, for example, that a rotary compactor of a certain weight is to be towed over a compaction site until a differential draft force is about equal to a desired differential draft force. The compaction specification may specify that a desired compaction is attained when the difference in draft force between a current pass and the previous pass over the material is about equal to a target value. Compaction determination system 28 may determine the differential draft force between two successive passes, and determine if the differential draft force is within a specified range of the target differential draft, such as, for example, within about ±5%.

FIGS. 3 and 4 will be described in detail below to further illustrate aspects of the disclosed system.

INDUSTRIAL APPLICABILITY

The disclosed compaction determination system may be applicable to any towed compactor where quantifiable and repeatable control of material compaction is desired. Particularly, the disclosed compaction determination system may provide a simple, reliable way to determine the amount of material compaction based on the draft force required to tow a towed compactor, without requiring destruction or penetration of the compacted material. The operation of compaction determination system 28 will now be described.

Towed compactor 20 may be attached to machine 10 through attachment means 18. An operator may then operate machine 10 and pull towed compactor 20 over a compaction area containing a material to be compacted. The operator may make one or more passes over the compaction area, such that the number of passes is sufficient to compact the material to a predetermined level, as determined by an operating mode of compaction determination system 28. Each pass may generally correspond to the width of rotary compactor 24, attempting to minimize overlap among contiguous passes, and ensuring that no area is left uncompacted. Controller 30 may use position determining unit 38 to determine that the entire compaction area reaches the desired compaction level, and alert an operator of machine 10 through display 40a as to the results of compaction.

As illustrated in FIG. 3, controller 30 may receive and store in memory any necessary information associated with the current compacting operation, such as, for example, the boundaries of the area to be compacted, a desired measurement interval, a desired compaction amount, and any other information necessary to describe the compaction site (Step 100). The boundaries may be defined by, for example, inputting into controller 30 through input 40b a description of the area using GPS coordinates, Cartesian coordinates, latitude and longitude, or any other coordinate system sufficient to describe the area. Alternatively, the boundaries may be input by driving machine 10 and towed compactor 20 around the boundary of the area to be compacted, while controller 10 receives and stores data from position determining unit 28 sufficient to define the boundaries of the area. Other information that the operator may input include, for example, material type, material moisture content, date, time, and weather information.

Step 100 may be better understood through an example. In this example, controller 30 receives various data about a particular compaction site, including a weight of rotary compactor 24 being 10000 lb, a width of rotary compactor 24 being 6 feet, a measurement interval being 15 feet, the boundaries of the site in GPS coordinates, the material type being clay, the moisture content as measured on site, and the date and time.

Controller 30 may then receive and store in memory calibration data such as, for example, the draft force on drawbar 22 reported by force sensor 32, the incline of towed compactor 20 reported by inclinometer 34, and the position of towed compactor 20 reported by position determining unit 38 (Step 102). The data may be received as the operator drives machine 10 with attached towed compactor 20 over material in a test area, which may be a smaller subdivision of the compaction site. In addition to receiving and storing the calibration data into memory, controller 30 may create associations in memory among the various parameters, such as, for example, an association that a specific drawbar force, incline, and distance traveled are associated with a specific location or region of the compaction site. These associations may be used by controller 30 to calculate accurate determinations of the amount of compaction, as well as to provide visual representations of the amount of compaction on display 40a. The data stored during this step may be used for various calculations and visual representations, including, for example, calculations by controller 30 to predict and determine the performance of rotary compactor 24 during compaction of the entire compaction site.

After it is verified by compaction verification means known in the art that the compaction value of the test site satisfies the compaction specification, controller 30 may receive and store in memory data such as, for example, the force on drawbar 22 reported by force sensor 32, the incline of towed compactor 20 reported by inclinometer 34, and the position of towed compactor 20 reported by position determining unit 38, as towed compactor 20 is towed over the compacted test area. Controller 30 may then calculate the draft force on towed compactor 20 using Equations 1 and 2. Controller 30 may store this draft force as a target value for the compaction of the remainder of the compaction site.

Continuing with the example from step 100 above, the test area is determined to be a small area the width of towed compactor 20 (6 feet), and the length of the measurement interval (15 feet). After verifying that the desired compaction value of the test area has been reached, towed compactor 20 is towed over the test area once again. During this final pass, controller 30 receives a force measurement of 2700 lb from force sensor 32, and an incline measurement of 4 deg. from inclinometer 34. Controller 30 then uses Equation 1 to calculate an incline force of 698 lb, and Equation 2 to calculate a draft force of 2002 lb that accounts for the incline. Controller 30 then stores the 2002 lb value as the target draft force for use in later compaction level determinations.

Controller 30 may receive and store in memory operational data such as, for example, the force on drawbar 22 reported by force sensor 32, the incline of towed compactor 20 reported by inclinometer 34, and the position of towed compactor 20 reported by position determining unit 38, as towed compactor 20 makes one or more passes over the entire compaction site (Step 104). In addition to receiving and storing the operational data in the memory, controller 30 may create associations in memory among the various parameters, such as, for example, an association among a drawbar force, incline, distance traveled and location or region of the compaction site. These associations may be used by controller 30 to accurately calculate the amount of compaction of the site, as well as to provide visual representations of the amount of compaction on display 40a.

Controller 30 may use the operational data received and stored in step 104 to calculate the draft force on towed compactor 20 for the entire compaction site (Step 106). Controller 30 may first use Equation 1 to calculate the incline force on the towed compactor, and then Equation 2 to calculate the draft force on towed compactor 20. Controller 30 may then compare the draft force calculated using Equation 2 to the target draft force value stored during step 102. Controller 30 may perform these calculations and comparisons for each pass of each subdivision of the compaction site, as defined by the measurement interval. Controller 30 may store in memory the results for each pass of each subdivision. When controller 30 determines that the draft force on the most recent pass is greater than the target draft force, then controller 30 may signal the operator that compaction is not yet complete, and that one or more passes may still be required (return to Step 104). When controller 30 determines that the draft force on the most recent pass is less than or equal to the target draft force, then controller 30 may determine that compaction is complete. Controller 30 may evaluate the results of the comparison of the draft force using a range of acceptable compaction, such as, for example, ±5% of the desired compaction level.

Continuing with the example from steps 100 and 102, controller 30 receives a force measurement of 8500 lb from force sensor 32, and an incline measurement of 6 deg. from inclinometer 34 during a particular measurement interval. Controller 30 then uses Equation 1 to calculate an incline force of 1045 lb, and Equation 2 to calculate a draft force of 7455 lb that accounts for the incline. In Step 106, controller 30 determines that the calculated draft force of 7455 lb is greater than the target draft force of 2002 lb determined in Step 102, and therefore compaction is not yet complete (return to Step 104). In Step 104, on the second pass of a particular area, moving in the opposite direction, controller 30 receives a force of 980 lb from force sensor 32, and an incline of −6 deg. from inclinometer 34. Controller 30 then uses Equation 1 to calculate an incline force of −1045 lb, and Equation 2 to calculate a draft force of 2025 lb that accounts for the incline. In Step 106, controller 30 then determines that the calculated draft force of 2025 lb is within ±5% of the target draft force of 2002 lb, and therefore that compaction is complete.

Once controller 30 has determined that compaction is complete, controller 30 may display compaction information on display 40a for each subdivision (Step 108). This information may be used by the operator in determining which subdivisions of the compaction area may still need one or more passes of rotary compactor 24 to achieve the desired compaction. After controller 30 determines that the compaction level of the entire compaction site has reached the desired value, controller 30 may gather and store the final information about the compaction as an archive file within its memory. Controller 30 may display the information on display 40a, and/or download or otherwise record it using any apparatus commonly known in the art for downloading and/or recording data. This downloaded and/or recorded data may be used in future compaction activities and/or as quality control or quality assurance of the compaction activities in validation that the proper compaction level has been achieved.

Continuing the example from the preceding steps, in Step 108, controller 30, having determined that the calculated draft force of 2025 lb is within the specified range of the target draft force of 2002 lb, determines that compaction is complete. Controller 30 then displays information on display 40a to notify the operator that compaction of the area is complete, and then stores the data for later use.

The second operating mode of compaction determination unit 38 shown in FIG. 4 will now be described. Controller 30 may receive and store in memory any necessary information associated with the current compacting operation, as described above in Step 100 (Step 200).

Step 200 may be better understood through an example. Controller 30 receives various data about a compaction site as described in Step 100 above. In addition, a target differential draft force of 500 lb is entered, as compaction may be determined to be complete when, according to the compaction specification, the differential draft force between two passes is less than about 500 lb, within a range of ±5%.

Controller 30 may then receive and store in memory operational data as described in Step 104 above (Step 202). Controller 30 may use the operational data received and stored in step 202 to calculate a differential draft force experience by compactor 20 between passes (Step 204). Controller 30 may use Equation 1 to calculate the incline force on the towed compactor, and Equation 2 to calculate the draft force on towed compactor 20 to account for the incline. Controller 30 may then use Equation 3 to compare the draft force of the current compacting pass over a single subdivision to the draft force for the previous compacting pass over that same subdivision. When controller 30 determines that the differential draft force after the current pass is greater than the target differential draft force, controller 30 may signal the operator that compaction is not yet complete, and that one or more passes may still be required (return to Step 202). However, when controller 30 determines that the differential draft force after the current pass is less than or equal to the target differential draft force, then controller 30 may determine that compaction is complete. Controller 30 may evaluate the results of the comparison of the differential force using a range, such as, for example, ±5%, as specified by the compaction specification.

Continuing the example from step 200, on pass 1 of a subdivision of the compaction site, controller 30 receives data from force sensor 32 reporting a force measurement of 8500 lb and inclinometer 34 reporting an incline measurement of 6 degrees. Controller 30 uses Equation 1 to calculate an incline force of 1045 lb, and then uses Equation 2 to calculate the draft force to be 7455 lb that accounts for the incline. In Step 204, because this was the first pass, controller 30 cannot compare the calculated draft force to the draft force from the previous pass, so controller 30 stores the calculated draft force value and returns to step 202. In step 202, on pass 2, controller 30 receives data from force sensor 32 reporting a force measurement 980 lb and inclinometer 34 reporting an incline measurement of −6 degrees. Controller 30 then uses Equation 1 to calculate an incline force of −1045 lb, and Equation 2 to calculate the draft force to be 2025 lb that accounts for the incline. In step 204, controller 30 uses Equation 3 to determine that the differential draft force between pass 1 and 2 is 5429 lb. Because controller 30 calculates this differential draft force is greater than the target differential force of 500 lb, controller 30 stores the draft force value of 2025 lb for pass 2 and returns to step 202. In Step 202, on pass 3 of the same area, controller 30 receives data from force sensor 32 reporting a force measurement of 2750 lb and inclinometer 34 reporting an incline measurement of 6 degrees. Controller 30 uses Equation 1 to calculate an incline force of 1045 lb, and Equation 2 to calculate the draft force to be 1705 lb that accounts for the incline. In step 204, controller 30 uses Equation 3 to determine that the differential draft force between pass 2 and 3 is 321 lb. Because controller 30 calculates this differential draft force of 321 lb is within the acceptable range of the target differential force of 500 lb, controller 30 has determined that compaction is complete.

Controller 30 may make a determination that compaction is complete for one or more subdivisions of the compaction area, and/or for the entire compaction area, as described in Step 108 above (Step 206). Controller 30 may display information on display 40a that shows the subdivisions for which controller 30 has determined that compaction is complete, as described above.

The examples in the preceding paragraphs illustrate several aspects of the disclosed compaction detection system The disclosed apparatus and method may allow compaction determination in a manner that does not require disruption of the material surface. This may be beneficial because a disruption of some surfaces, such as the surface of a roadway, may be undesirable.

A second aspect of the disclosed compaction detection system is the measurement of an incline of a surface for use in determining the amount of compaction of a material. This measurement may allow compaction determination to be more accurate by accounting for the draft force that results from the incline.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed compaction determination system without departing from the scope of the invention. Other embodiments of the compaction determination system will be apparent to those skilled in the art from consideration of the specification and practice of the compaction determination system disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.