Patent Description:
A compaction machine may include a chassis and two vibrating drums rotatably mounted to the chassis so that the drums compact a work surface (e.g., an asphalt mat) as the compaction machine moves thereon. A compaction machine may include eccentric masses (also referred to as eccentric shafts) in the respective drums that are rotated at speed to generate vibrations that are transmitted as impacts by the drums to the work surface. Various examples of compaction machines are discussed, for example, in <CIT> entitled "Vibrating Roller," <CIT> entitled "Vibratory System For Compactor Vehicles," and <CIT> entitled "Apparatus And Method For Controlling the Start Up And Phase Relationship Between Eccentric Assemblies. " Documents <CIT> and <CIT> disclose the preamble of independent claim <NUM>.

Notwithstanding known compaction machines, there continues to exist a need in the art for compaction machines, methods, and/or controllers providing increased efficiency of operation and/or improved compaction.

According to one aspect, a vibratory compaction machine according to claim <NUM> is provided, including a chassis, first and second drums rotatably mounted to the chassis to allow rotation of the first and second drums over a work surface, first and second vibration mechanisms, and a vibration controller. The first vibration mechanism is configured to generate vibrations that are transmitted as impacts by the first drum to the work surface, and the second vibration mechanism is configured to generate vibrations that are transmitted as impacts by the second drum to the work surface. The vibration controller is configured to determine a first pattern of impacts based on a first configuration of the first vibration mechanism; determine a second pattern of impacts based on a second configuration of the second vibration mechanism; and control at least one of a vibration speed and a phase of at least one of the first and second vibration mechanisms so that the first pattern of impacts transmitted to the work surface by the first drum and the second pattern of impacts transmitted to the work surface by the second drum are coordinated as the compaction machine moves over the work surface , wherein impact positions of the second pattern of impacts transmitted to the work surface are offset with respect to impact positions of the first pattern of impacts transmitted to the work surface.

Impact positions of the second pattern of impacts transmitted to the work surface are offset with respect to impact positions of the first pattern of impacts transmitted to the work surface. For example, the first and second patterns of impacts may be coordinated with respect to a section of the work surface so that the impact positions of the second pattern of impacts on the section of the work surface are offset with respect to the impact positions of the first pattern of impacts on the section of the work surface once both of the first and second drums have traversed the section of the work surface. Moreover, the impact positions of the second pattern on the section of the work surface are interleaved with respect to the impact positions of the first pattern on the section of the work surface.

The vibratory compaction machine may also include a drive motor coupled with at least one of the first and second drums to propel the compaction machine over the work surface. The first vibration mechanism may include a first eccentric mass mounted inside the first drum, and a first vibration motor coupled with the first eccentric mass wherein the first vibration motor is configured to spin the first eccentric mass inside the first drum to generate the vibrations that are transmitted as the impacts by the first drum to the work surface. The second vibration mechanism may include a second eccentric mass mounted inside the second drum, and a second vibration motor coupled with the second eccentric mass wherein the second vibration motor is configured to spin the second eccentric mass inside the second drum to generate the vibrations that are transmitted as the impacts by the second drum to the work surface. In addition, the vibration controller may be configured to coordinate the first and second patterns of impacts responsive to at least one of a phase of the first eccentric mass, a frequency of rotation of the first eccentric mass, a phase of the second eccentric mass, a frequency of rotation of the second eccentric mass, a speed of the compaction machine over the work surface, a distance traversed by the compaction machine over the work surface, a center to center distance between the first and second drums, and sizes of the first and second drums.

The controller is further configured to adjust relative rotational phases of the first and second eccentric masses while coordinating the first and second patterns of impacts transmitted to the work surface by adjusting at least one of a speed of the vibratory compaction machine, a rotational frequency of the first eccentric mass, a rotational frequency of the second eccentric mass, a distance between impacts of the first pattern delivered by the first drum, a distance between impacts of the second pattern delivered by the second drum, and an offset between adjacent impacts of the first and second patterns.

The controller may be further configured to maintain an offset of rotational phases of the first and second eccentric masses while coordinating the first and second patterns of impacts transmitted to the work surface by controlling at least one of a speed of the vibratory compaction machine, a rotational frequency of the first eccentric mass, a rotational frequency of the second eccentric mass, a distance between impacts of the first pattern delivered by the first drum, a distance between impacts of the second pattern delivered by the second drum, and an offset between adjacent impacts of the first and second patterns.

The controller may be configured to coordinate the first pattern of impacts and the second pattern of impacts by setting operational parameters of the first vibration mechanism to provide the first pattern of impacts transmitted to the work surface by the first drum as a baseline, and adjusting operational parameters of the second vibration mechanism responsive to the baseline to provide the second pattern of impacts transmitted to the work surface.

According to still another aspect, a method according to claim <NUM> is provided.

The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in a constitute a part of this application, illustrate certain non-limiting embodiments of inventive concepts. In the drawings:.

<FIG> illustrates a self-propelled compaction machine according to some embodiments of inventive concepts. The compaction machine of <FIG> may include a chassis <NUM>, <NUM>, first (e.g., leading) and second (e.g., trailing) rotatable drums <NUM> and <NUM> at the front and back at of the chassis <NUM>, <NUM>, and a driver station including a seat <NUM> and a steering mechanism <NUM> (e.g., a steering wheel) to provide driver control of the compaction machine. Moreover, each drum may be coupled to the chassis <NUM>, <NUM> using a respective frame <NUM>, <NUM> (also referred to as a yoke). One or both of the drums <NUM>, <NUM> may be driven by a drive motor over a work surface <NUM>.

Each of drums <NUM> and <NUM> also includes a vibration mechanism <NUM>. Within the scope of the present embodiment the vibration mechanism <NUM> may be any device or devices, such as, for example, a variety of eccentric rotating mass systems, linear resonant actuator systems, etc., that are capable of generating vibrations transmitted as impacts by the first and second drums <NUM> and <NUM> to the work surface <NUM>. By way of example, the vibration mechanism <NUM> may be provided using: one eccentric assembly including a single eccentric shaft (single amplitude machine); one eccentric assembly including two eccentric shafts (multiple amplitude machine); multiple eccentric assemblies including single and/or double eccentric shaft systems (oscillatory machines); or using a linear actuator moving a mass at a speed to achieve similar vibration characteristics. Those of ordinary skill in the art will appreciate that numerous vibration mechanisms are known, and the scope of the present embodiment is not limited to the particular vibration system <NUM> illustrated. While lesser or more complex eccentric systems may be employed within the scope of the present embodiment, for the sake of simplicity and brevity, <FIG>, shows a relatively simple vibration mechanism <NUM> that includes a single rotatable eccentric mass <NUM>, which may, for example, be driven by an eccentric motor <NUM> and supported by a mounting assembly <NUM>. Those of ordinary skill in the art will appreciate that the center of mass of the eccentric mass <NUM> is imbalanced and does not reside on the rotational axis <NUM> about which the eccentric mass <NUM> rotates. Those of ordinary skill in the art will also appreciate that, for purposes of increasing compaction efficiency, the imbalanced nature of the eccentric mass <NUM> of each drum <NUM>, <NUM> imparts vibration to the drums <NUM>, <NUM> as the eccentric mass rotates about rotational axis <NUM>. Those of ordinary skill in the art will also appreciate that as the eccentric mass <NUM> rotates that the eccentric mass <NUM> generates a downward force that is transmitted as an impact by the drums <NUM>, <NUM> to the work surface <NUM> Furthermore, those of ordinary skill in the art will appreciate that as the eccentric mass <NUM> rotates, the eccentric mass also generates an upward force which urges the drums <NUM>, <NUM> upward, relative to the occurrence of a downward impact force.

In a conventional compaction machine, front and rear drums may vibrate independently. Accordingly, impacts may be inefficiently delivered by the front and rear drums over a same section of asphalt. If impacts are delivered by the front and rear drums at the same locations over a section of asphalt, for example, uneven compaction may occur requiring more passes of the compaction machine to achieve a desired uniformity and/or density of the asphalt, thereby reducing efficiency. Moreover, insufficient control of the vibrations of the front and rear drums may result in increased vibration through the chassis, potentially causing durability issues with respect to the compaction machine and/or components thereof.

Impacts per foot is one parameter used to measure machine performance. During operation, each eccentric mass may be rotated to generate vibrations transmitted as impacts by the first and second drums <NUM> and <NUM> to the work surface <NUM> The frequency of impacts and the compaction machine travel speed together determine the impacts per foot for each drum, which may strongly influence a number of passes the compaction machine must make over a given section of asphalt (also referred to as a patch or length of asphalt) to achieve a desired density of the asphalt. Each drum, for example, may deliver in the range of <NUM> to <NUM> impacts per foot (so that positions/locations of consecutive impacts of a drum are spaced <NUM> to <NUM> inches across the asphalt), and more particularly, in the range of <NUM> to <NUM> impacts per foot (so that positions/locations of consecutive impacts are spaced in the range of <NUM> to <NUM> inches across the asphalt). With current vibratory drum system designs, a lack of coordination between positions/locations of impact delivered by the two drums may result in additional passes.

According to some embodiments of inventive concepts, a control system may be provided in the compaction machine to coordinate impacts of the first and second drums to allow tuning for improved performance and/or efficiency. Moreover, relative phases of the eccentric masses may be adjusted while coordinating impacts to reduce vibrations transmitted through the chassis. In order to adjust relative phases of the eccentric masses while maintaining coordination of leading and trailing drum impact patterns, relative offsets between leading and trailing drum impact patterns may be adjusted, speed of the compaction machine may be adjusted, and/or frequencies of rotation of the leading and trailing eccentric masses may be adjusted.

As discussed herein, a pattern of impacts refers to a pattern of impact positions on an asphalt mat (or other work surface <NUM>) at which a vibratory compaction drum delivers impacts to the asphalt mat due to vibrations caused by the rotating eccentric mass. Moreover, first (e.g., leading) drum <NUM> and second (e.g., trailing) drum <NUM> of a vibratory compaction machine will deliver respective first and second patterns of impacts to a same section of asphalt at different times because the leading and trailing drums pass over the section of asphalt at different times. Impact positions of the second pattern of impacts from the second drum <NUM> may be offset and interleaved with respect to impacts from the first drum <NUM> over the section of asphalt even though the first and second drums <NUM> and <NUM> traverse the section of asphalt at different times.

By deliberately tuning vibrations of the drums (e.g., by controlling frequencies of rotation of the respective eccentric masses, phases of rotation of eccentric masses, speed of the compaction machine, etc.), impact positions of the trailing drum <NUM> may be shifted slightly or offset with respect to impact positions of the leading drum <NUM> over the same section of asphalt after both drums have passed over that section of asphalt, while both drums deliver a same number of impacts per unit length (e.g., impacts per foot). For example, impacts of the trailing drum <NUM> may be controlled to hit peaks (areas of lesser density) that were left behind by the leading drum <NUM>. Stated in other words, vibrations of the drums may be coordinated/controlled so that positions of impact (also referred to as locations of impact) of the trailing drum <NUM> on the asphalt may be controlled to fall between positions of impact of the leading drum on the asphalt.

<FIG> is a diagram where the upper section illustrates leading and trailing drums <NUM> and <NUM> compacting a work surface <NUM> such as an asphalt mat, and the lower section of the diagram illustrates a representation of the work surface <NUM> of the asphalt mat zoomed in significantly to show fine detail of the working surface that may result from a particular impacts per unit length (e.g., "impacts per foot") machine performance. By coordinating impacts from the leading and trailing drums <NUM> and <NUM> as shown in <FIG>, the compaction machine may provide a desired density/uniformity of the asphalt in fewer passes thereby improving efficiency, productivity, and/or a quality of the resulting asphalt. An average density of the asphalt is represented in <FIG> by the different dot densities in sections 31a, <NUM>1b, and 31c of the asphalt mat. While not indicated by the dot pattern of section <NUM>1b, a periodic variation in density may occur after the leading drum <NUM> passes, with areas of higher density occurring at positions most directly impacted by the leading drum <NUM> (indicated by solid line arrows and also referred to as impact positions or positions of impact) and with areas of lower density occurring between these positions of most direct impact. In section 31c, these periodic density variations may be reduced after passage of both leading and trailing drums <NUM> and <NUM> by coordinating impacts of the drums.

As the compaction machine moves from right to left across the asphalt mat work surface <NUM> in <FIG>, leading drum <NUM> provides a first phase of compaction indicated by the change in density from section 31a (not yet compacted by the leading drum <NUM>) to section 31b of the asphalt mat work surface <NUM> (compacted by the leading drum <NUM> but not the trailing drum <NUM>), and trailing drum <NUM> provides a second phase of compaction indicated by the change in density from section 31b to 31c (compacted by both leading and trailing drums <NUM> and <NUM>) of the asphalt mat work surface <NUM>. The solid line arrows at the bottom of <FIG> indicate positions of impact of the leading drum <NUM> on sections 31b and 31c of the asphalt mat work surface <NUM>. The longer dashed line arrows at the bottom of <FIG> indicate positions of impact of the trailing drum <NUM> on section 31c the asphalt mat work surface (that have been compacted by the trailing drum <NUM>), and the shorter dashed line arrows indicate intended positions of impact of the trailing drum <NUM> on section 31b of the asphalt mat work surface (not yet compacted by the trailing drum <NUM>).

As shown in <FIG>, vibrations of at least one of the leading and trailing drums <NUM> and <NUM> may thus be controlled so that a first pattern of impacts transmitted to the asphalt mat work surface <NUM> by the leading drum <NUM> and a second pattern of impacts transmitted to the asphalt mat work surface <NUM> by the trailing drum <NUM> are coordinated as the compaction machine moves over the work surface <NUM>. More particularly, the patterns of impacts from the leading and trailing drums <NUM> and <NUM> may be coordinated so that impacts of the trailing drum <NUM> are offset and/or interleaved with respect to impacts of the leading drum <NUM> over section 31c of the asphalt mat work surface <NUM> that has been traversed by both leading and trailing drums <NUM> and <NUM> as shown in <FIG>.

Impact positions of the leading drum <NUM> indicated with solid line arrows and impact positions of the trailing drum <NUM> indicated with longer dashed line arrows over section 31c may thus be interleaved and offset in a pattern as shown in <FIG> over a section 31c of the asphalt mat work surface <NUM> having a certain length. As discussed above, each drum may deliver in the range of <NUM> to <NUM> impacts per foot (so that impacts from a same drum are spaced <NUM> to <NUM> inches across the asphalt), and more particularly, in the range of <NUM> to <NUM> impacts per foot (so that impacts of each drum are spaced <NUM> to <NUM> inches across the asphalt). At <NUM> impacts per foot, impact positions from trailing drum <NUM> may be spaced in the range of about <NUM> to <NUM> inches relative to adjacent impact positions from leading drum; at <NUM> impacts per foot, impact positions from trailing drum <NUM> may be spaced in the range of about <NUM> to <NUM> inches from adjacent impact positions from leading drum <NUM>; at <NUM> impacts per foot, impact positions from trailing drum <NUM> may be spaced by about <NUM> to <NUM> inches from adjacent impact positions from leading drum <NUM>; and at <NUM> impacts per foot, impact positions from trailing drum <NUM> may be spaced by about <NUM> to <NUM> inches from adjacent impact positions from leading drum <NUM>.

As shown in <FIG>, impact positions from trailing drum <NUM> may be substantially centered between adjacent impact positions from leading drum <NUM> after both drums have traversed section 31c of the asphalt mat. According to some other embodiments, impact positions from trailing drum may be shifted from a center position between adjacent impact positions from the leading drum. According to some other embodiments, impact positions of leading and trailing drums <NUM> and <NUM> may be coordinated to coincide.

In greater detail, section 31a of the asphalt mat work surface <NUM> has not been compacted by either drum, section <NUM>1b of the asphalt mat work surface <NUM> has been compacted by the leading drum <NUM> but not the trailing drum <NUM>, and section 31c of the asphalt mat work surface <NUM> has been compacted by both the leading and trailing drums <NUM> and <NUM>. Based on the speed of the compaction machine and vibrations generated by rotation of eccentric mass 23a, leading drum <NUM> may generate impacts at locations on the asphalt mat work surface <NUM> indicated by the solid line arrows. Over section <NUM>1b of the asphalt mat work surface <NUM> where only the leading drum <NUM> has passed, variations in density and/or surface (e.g., peaks and valleys) may occur as indicated by the representation of the asphalt mat work surface below the arrows. To reduce these variations, vibrations of the trailing drum <NUM> may be controlled so that impact positions of the trailing drum <NUM> will occur between previous impact positions of the leading drum <NUM>. For example, impacts of the trailing drum <NUM> may occur at surface peaks left by the leading drum <NUM> and/or at regions of lower asphalt density left by the leading drum <NUM>. The shorter dashed line arrows for section 31b indicate intended impacts of the trailing drum <NUM>. According to some embodiments, impact locations of the trailing drum <NUM> may be evenly spaced between impact locations of the leading drum <NUM> to reduce variations in density and/or surface peaks/valleys.

For section 31c where both the leading and trailing drums <NUM> and <NUM> have passed, the solid line arrows indicate impact positions from the leading drum <NUM> on the asphalt mat work surface and the longer dashed line arrows indicate impact positions from the trailing drum <NUM> on the asphalt mat work surface. As shown, the impact positions of the trailing drum <NUM> may be arranged between the impact positions of the leading drum <NUM> on the section 31c of the asphalt mat work surface <NUM> where both leading and trailing drums have passed. Over section 31c of the asphalt mat work surface <NUM>, variations in density and/or surface (e.g., peaks and valleys) may be reduced as indicated by the representation of the asphalt surface below the arrows. By offsetting and interleaving impact positions of the leading and trailing drums <NUM> and <NUM>, a uniformity of asphalt density and/or surface may be improved.

A control system of <FIG> may include controller <NUM> configured to coordinate patterns of impacts delivered by leading and trailing drums <NUM> and <NUM> as discussed above with respect to <FIG> responsive to at least one of a phase of the first eccentric mass, a frequency of rotation of the first eccentric mass, a phase of the second eccentric mass, a frequency of rotation of the second eccentric mass, a speed of the compaction machine over the work surface <NUM>, a center to center distance between the first and second drums, and sizes (e.g., diameter, radius, circumference, etc.) of the leading and trailing drums <NUM> and <NUM>. As shown in <FIG>, controller <NUM> inputs may be coupled to a speed/distance sensor <NUM> (e.g., coupled with a drum and/or Global Positioning System GPS receiver) providing information regarding speed of the compaction machine and/or distance traveled across the asphalt mat work surface <NUM>, a leading eccentric mass sensor 405a providing information regarding a frequency and phase of rotation of leading eccentric mass 23a, and a trailing eccentric mass sensor 405b providing information regarding a frequency and phase of rotation of trailing eccentric mass 23b. In addition, controller <NUM> outputs may be coupled with speed control interface <NUM> (e.g., coupled with the drive motor) to control a speed of the compaction machine across the asphalt mat work surface <NUM>, a vibration control interface 409a (e.g., coupled with the vibration motor for the leading eccentric mass) for leading drum <NUM> to control a frequency and phase of rotation of eccentric mass 23a, and a vibration control interface 409b (e.g., coupled with the vibration motor for the trailing eccentric mass) for trailing drum <NUM> to control a frequency and phase of rotation of eccentric mass 23b. While sensors and control interfaces are shown in <FIG> separate from controller <NUM>, one or more of the sensors and/or control interfaces of <FIG> or portions thereof may be incorporated in controller <NUM>.

Eccentric mass sensors 405a and 405b (e.g., coupled with the respective vibration motors) may thus provide phase positions of eccentric masses 23a and 23b to be used by controller <NUM> to coordinate impact patterns of leading and trailing drums <NUM> and <NUM>. In a single amplitude machine (with a single eccentric mass in each drum) as shown in <FIG>, a single index may be used by eccentric mass sensors 405a and 405b to determine phases of respective eccentric masses. In a multiple amplitude machine, an eccentric mass assembly may spin with the inner and outer eccentric masses in different orientations to provide different amplitudes of vibration. Accordingly, an eccentric mass sensor may be configured to generate phase information regarding the respective orientations/amplitudes based on different indexing. Sensing in multiple amplitude machines is discussed by way of example in <CIT>, the disclosure of which is hereby incorporated herein in its entirety by reference. By coupling each eccentric mass to the respective vibration motor with a known orientation relative to the vibration motor, a respective eccentric mass sensor may determine both a frequency of rotation and a phase of rotation of the eccentric mass (e.g., a position of the eccentric mass) by monitoring a position/index of a rotor on the vibration motor.

Distance travelled while vibrations of leading and trailing drums <NUM> and <NUM> are turned on may be calculated continuously by speed/distance sensor <NUM> and thus known to controller <NUM>. This information may use fixed machine geometry (e.g., drum diameter, center to center distance between drums, etc.) and operator inputs (e.g., travel speed) to produce and update the data used by controller <NUM>.

Control logic of controller <NUM> may thus monitor and adjust machine parameters (e.g., machine speed, frequency/phase of rotation of leading drum, frequency/phase of rotation of trailing drum, space between impacts of each drum on the working surface, offsets between impacts of leading and trailing drums, etc.) to achieve a desired performance in terms of impact coordination between leading and trailing drums, impacts per unit length (e.g., impacts per foot), impact amplitude, vibration, etc..

According to some embodiments, leading drum <NUM> may be set as a master or baseline from which other parameters may be adjusted. In such a system, trailing drum <NUM> may be set as a slave so that parameters of the trailing drum <NUM> (e.g., rotational frequency/phase of eccentric mass 23b) may be adjusted to achieve a desired coordination of impact patterns of leading and trailing drums <NUM> and <NUM>. According to some other embodiments, trailing drum <NUM> may be set as a master, and leading drum <NUM> may be set as a slave so that parameters of the leading drum <NUM> may be adjusted to achieve a desired coordination. Moreover, the compaction machine may operate in both forward and in reverse so that one drum is set as the master when the compaction machine travels in one direction (e.g., forward) and the other drum is set as the master when the compaction machine travels in the other direction (e.g., reverse).

Impacts and/or vibrations of the leading and trailing drums may be coordinated to provide improved performance, efficiency, and/or quality of asphalt. By controlling phases of impacts delivered by the leading and trailing drums, the trailing drum may be controlled to compact targeted zones in the asphalt mat work surface that were missed by the leading drum, thereby allowing for fewer compaction machine passes to achieve a desired asphalt density. Moreover, by coordinating machine speed with the coordinated impact patterns of the leading and trailing drums (e.g., space between adjacent impact locations of each drum on the asphalt mat, an offset between impact patterns of the two drums, etc.), a desired phase relationship between eccentric masses may be achieved to reduce vibrations coupled into the chassis of the machine.

Operations of controller <NUM> will now be discussed with reference to the flow charts of <FIG>. At block <NUM>, controller <NUM> may receive system inputs from speed/distance sensor <NUM> (providing a speed of and/or distance traveled by compaction machine over the work surface <NUM>), leading eccentric mass sensor 405a (providing a frequency and/or phase of rotation of eccentric mass 23a), and trailing eccentric mass sensor 405b (providing a frequency and/or phase of rotation of eccentric mass 23b). Responsive to these system inputs and responsive to machine parameters (e.g., center to center distance of leading and trailing drums, sizes of first and second drums, etc.) at block <NUM>, controller <NUM> may coordinate a first pattern of impacts transmitted to the work surface <NUM> (e.g., an asphalt mat work surface) by the leading drum <NUM> and a second pattern of impacts transmitted to the work surface <NUM> (e.g., an asphalt mat work surface) by the trailing drum <NUM> by controlling at least one of rotational frequency/phase of eccentric mass 23a via vibration control interface 409a and vibration motor 21a, rotational frequency/phase of eccentric mass 23b via vibration control interface 409b and vibration motor 21b, and/or speed of the compaction machine via speed control interface <NUM> as the compaction machine moves over the work surface <NUM>.

According to some embodiments, operations of coordinating impact patterns at block <NUM> may be performed as discussed with respect to blocks 603a and 603b of <FIG>. At block 603a, controller <NUM> may be configured to set operational parameters of eccentric mass 23a and/or associated vibration motor 21a to provide the first pattern of impacts transmitted to the work surface <NUM> by the first drum as a baseline (including a spacing between positions of impacts delivered by the first drum) so that drum <NUM> is designated as the master. At block 603b, controller <NUM> may be configured to adjust operational parameters of eccentric mass 23b and/or associated vibration motor 21b responsive to the baseline to provide the second pattern of impacts transmitted to the work surface <NUM> (such that positions of impacts of the second pattern are offset relative to positions of impacts of the first pattern) so that drum <NUM> is designated as the slave. According to some embodiments, the leading drum <NUM> (with eccentric mass 23a) may thus be designated as a master, and the trailing drum (with eccentric mass 23b) may be designated as a slave. According to some other embodiments, the trailing drum <NUM> (with eccentric mass 23b) may be designated as a master, and the leading drum (with eccentric mass 23a) may be designated as a slave.

Operations of blocks <NUM> and <NUM> may thus provide an inner control loop coordinating impact patterns from leading and trailing drums <NUM> and <NUM>. At block <NUM>, controller <NUM> may monitor rotational phases of eccentric masses 23a and 23b and/or chassis vibration to maintain a desired phase offset and/or to reduce vibrations transmitted to the chassis. Responsive to monitoring at block <NUM>, controller <NUM> may determine whether a phase offset between eccentric masses 23a and 23b is within a desired range and/or whether chassis vibrations are within a desired range. Provided that the rotational phases of eccentric masses 23a and 23b are within a desired range (e.g., that the phases are sufficiently offset) and/or that the chassis vibration is within a desired range (e.g., that chassis vibration is sufficiently low), controller <NUM> may continue operations of blocks <NUM> and <NUM>.

Responsive to rotational phases of eccentric masses 23a and 23b falling outside the desired range (e.g., that the phases are not sufficiently offset) and/or chassis vibration falling outside the desired range (e.g., that the chassis vibration is too high) at block <NUM>, controller <NUM> may adjust relative phases of eccentric masses 23a and 23b to provide a sufficient offset at block <NUM>. Controller <NUM>, for example, may adjust relative rotational phases of eccentric masses 23a and 23b at block <NUM> while coordinating the first and second patterns of impacts transmitted to the work surface <NUM> at blocks <NUM> and <NUM> by adjusting at least one of a speed of the vibratory compaction machine, a rotational frequency of the eccentric mass 23a, a rotational frequency of eccentric mass 23b, a distance between impacts of the first pattern delivered by leading drum <NUM> (i.e., adjusting impacts per unit length), and a distance between impacts of the second pattern delivered by trailing drum <NUM>. Operations of blocks <NUM>, <NUM>, and <NUM> may thus provide an outer control look to provide that vibrations through the chassis do not exceed a desired threshold. Moreover, adjusting the relative phases may include adjusting the relative phases by adjusting a center-to-center distance between drums <NUM> and <NUM>, for example, by adjusting an articulable coupling between front and rear portions <NUM> and <NUM> of the chassis.

According to some other embodiments, controller <NUM> may maintain an offset of rotational phases of the first and second eccentric masses at block <NUM>. More particularly, controller <NUM> may maintain the offset of rotational phases while coordinating the first and second patterns of impacts transmitted to the work surface <NUM> by controlling at least one of a speed of the vibratory compaction machine, a rotational frequency of the first eccentric mass, a rotational frequency of the second eccentric mass, a distance between impacts of the first pattern delivered by the first drum, a distance between impacts of the second pattern delivered by the second drum, and an offset between adjacent impacts of the first and second patterns. Moreover, maintaining the relative phases may include maintaining the relative phases by adjusting a center-to-center distance between drums <NUM> and <NUM>, for example, by adjusting and articulable coupling between front and rear portions <NUM> and <NUM> of the chassis.

Controller <NUM> may include a processor coupled with a memory and an interface circuit, and the interface circuit may provide communication between the processor and speed/distance sensor <NUM>, the leading and trailing eccentric mass sensors 405a-b, the speed control interface <NUM>, and the vibration control interfaces 409a-b. The processor may thus be configured to execute computer program code in the memory (described below as a non-transitory computer readable medium) to perform at least some of the operations discussed above with respect to <FIG>.

The control system of <FIG> may thus control timing of the eccentric mass of the trailing drum so that impact forces are applied at mat peaks corresponding to areas that were missed by the leading drum in a pass. Control logic of controller <NUM> may monitor machine performance and adjust the frequency and phasing of the eccentric mass of the trailing drum to time the impacts accordingly. The phase and frequency of the eccentric mass of the trailing drum may be controlled according to the phase and frequency of the eccentric mass on the leading drum, the drum diameter, the center-to-center distance between the drums, and the travel speed of the compaction machine. In addition to increasing compaction efficiency, the phase of the eccentric mass of the trailing drum may be controlled to reduce vibration induced fatigue by reducing/avoiding harmful drum phases (e.g., when phases of both eccentric masses are aligned).

In the above-description of various embodiments of the present disclosure, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention as defined by the appended claims.

When an element is referred to as being "connected", "coupled", "responsive", "mounted", or variants thereof to another element, it can be directly connected, coupled, responsive, or mounted to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected", "directly coupled", "directly responsive", "directly mounted" or variants thereof to another element, there are no intervening elements present. The term "and/or" and its abbreviation "/" include any and all combinations of one or more of the associated listed items.

Claim 1:
A vibratory compaction machine comprising:
a chassis (<NUM>, <NUM>);
first and second drums (<NUM>, <NUM>) rotatably mounted to the chassis to allow rotation of the first and second drums over a work surface (<NUM>);
a first vibration mechanism (<NUM>) configured to generate vibrations that are transmitted as impacts by the first drum to the work surface;
a second vibration mechanism (<NUM>) configured to generate vibrations that are transmitted as impacts by the second drum to the work surface; characterized by
a vibration controller (<NUM>) configured to:
determine a first pattern of impacts based on a first configuration of the first vibration mechanism;
determine a second pattern of impacts based on a second configuration of the second vibration mechanism; and
control at least one of a vibration speed and a phase of at least one of the first and second vibration mechanisms so that the first pattern of impacts transmitted to the work surface by the first drum and the second pattern of impacts transmitted to the work surface by the second drum are coordinated as the compaction machine moves over the work surface,
wherein impact positions of the second pattern of impacts transmitted to the work surface are offset with respect to impact positions of the first pattern of impacts transmitted to the work surface.