Patent Description:
Compaction machines are used in a variety of ground compaction and ground leveling applications. Most compaction machines have supports in the form of plates or rollers that rest on the surface to be compacted, and most of these supports are excited to vibrate so as to compact and level a worked surface. These machines are commonly referred to as "vibratory compactors.

A common vibratory compactor, and one to which the invention is well-suited, is a vibratory trench roller. The typical vibratory trench roller includes a chassis supported on the surface to be compacted by front and rear rotating drum assemblies. Each drum assembly supports a respective subframe of the chassis. In the case of an articulated trench roller, the subframes are coupled to one another by a pivot connection. Each of the drum assemblies may include a stationary axle housing and a drum that is mounted on the axle housing and that is driven to rotate by a dedicated hydraulic motor. Hydraulic motors are typically supplied with pressurized hydraulic fluid from a pump which may be powered by an engine or electric motor mounted on one of the subframes.

Each drum may be excited to vibrate by a dedicated exciter assembly that is located within the associated subframe and is powered by a motor connected to a pump. Each exciter assembly typically comprises one or more eccentric masses mounted on a rotatable shaft positioned within the subframe. Rotation of the eccentric shaft imparts vibrations to the subframe and to the remainder of the drum assembly. The entire machine may be configured to be as narrow as possible so as to permit the machine to fit within a trench whose floor is to be compacted. Machine widths of less than <NUM> feet (<NUM> meter) are common. Vibratory trench rollers of this basic type are disclosed, e.g., in <CIT>; <CIT>; <CIT>; <CIT>; and <CIT>; and <CIT> Further technological background can be found in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>. <CIT> relates to a skid loader wherein the steering angle can be limited.

Vibratory trench rollers often are controlled remotely using a transmitter on a remote controller that transmits infrared (IR), Radio, or other signals to the trench roller. The control signal is generated by manipulation of a joystick and/or other controls on the remote controller and controls operation of the machine. For example, an operator uses a single axis joystick to control hydraulic cylinder extension or retraction from a neutral or central direction. Joystick movement in one direction from a center position extends the hydraulic cylinder to steer in one direction (left or right), while movement in the other direction retracts the hydraulic cylinder to steer in the other direction (right or left).

The articulated trench roller, however, has no feedback that can be used to determine its direction of travel. Unlike in most other driving systems, the articulated trench roller will continue traveling at the last commanded angle. If the machine was turning, it will continue to turn. This constant turn might not be desirable in many instances.

Additionally, the articulated trench roller further does not provide any feedback to the operator that the hydraulic cylinder has reached the maximum travel or its "stroke limit" in either direction. The operator can therefore attempt to extend the hydraulic cylinder past its stroke limit in either direction, resulting in unnecessary strain on the hydraulic system power and efficiency losses as the excessive hydraulic flow is directed over the relief valve.

There is therefore a need to provide a method of providing feedback regarding the direction the articulated trench roller is traveling.

There is additionally a need to provide feedback regarding whether the stroke limit of the actuator effecting the turn is reached.

The need additionally has arisen to return the steering actuator of an articulated trench roller to the neutral position in the absence of a steering command signal to cause the machine to automatically return to straight-line travel.

In accordance with an aspect of the invention, a compaction machine, such as a vibratory trench roller, is provided in communication with a remote control. The compaction machine includes a mobile chassis having a first and second subframes pivotably connected to each other via a pivot connection, one or more steering actuators (hereafter collectively and individual referred to as a steering actuator) extending between the first and second subframes and configured to pivot the first and second subframes about the pivot connection to steer the machine, a steering angle sensor configured to provide data indicative of a machine steering angle, and a control unit in communication with the steering angle sensor and the steering actuator to determine an operational stroke of the steering actuator. The remote control includes a direction control and a transmitter configured to transmit an operator-generated steering command from the direction control to the control unit of the compaction machine. The control unit is configured to control the steering actuator based on the operator-generated steering command from the direction control and the determined machine angle as determined by the steering angle sensor.

In accordance with the invention, the control unit is configured to determine, based on the input from steering angle sensor, whether the steering actuator is at a limit of its operational stroke. If so, the control unit is configured to override commands from the direction control that otherwise would attempt to alter the machine steering angle beyond that the limit of the operational stroke of the steering actuator.

In another possible aspect of the invention, the control unit is configured to automatically return the steering actuator to a neutral position in the absence of a steering command signal.

In accordance with another aspect of the invention, the steering angle sensor is a position sensor that is disposed at or adjacent to the pivot connection and that is configured to sense an angular orientation of the pivot connection. In turn, the controller is configured to determine the stroke of the steering actuator based on the sensed angular orientation of the pivot connection.

In accordance with yet another aspect of the invention, the compaction machine may include at least one receiver configured to receive the input from the direction control and to transmit the input from the direction control to the control unit.

In accordance with yet another aspect of the invention, in instances in which there is no input from the direction control, the machine control unit may instruct the hydraulic cylinders to return to or maintain a neutral position to straighten out the compaction machine's direction of travel
The steering actuator may be a hydraulic cylinder. In this case, the compaction machine further includes a source of pressurized hydraulic fluid, a reservoir, and a control valve that controls fluid flow between the hydraulic cylinder, the source of pressurized hydraulic fluid, and the reservoir. The control unit operates the control valve to control the operational stroke of the hydraulic cylinder. Further yet, the control valve may be an on/off hydraulic solenoid valve as opposed to a proportional flow control valve.

Also disclosed is a method of operating a compaction machine having at least some of the features described above.

These and other features and advantages of the invention will become apparent to those skilled in the art from the following detailed description and the accompanying drawings. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention.

Exemplary embodiments of the invention are illustrated in the accompanying drawings in which like reference numerals represent like parts throughout, and in which:.

Referring now to the drawings, and initially to <FIG> and <FIG>, an exemplary compaction machine <NUM> is illustrated that is constructed in accordance with an embodiment of the present invention. The machine <NUM> of this embodiment is a vibratory trench roller <NUM>. The vibratory trench roller <NUM> includes a self-propelled machine controlled by a remote control <NUM>. The machine <NUM> includes a first, front rotating drum assembly <NUM> and a second, rear rotating drum assembly <NUM>. It is typically used to compact the bottom of trenches prior to laying pipelines or the like and/or to compact recently filled trenches. The machine <NUM> includes an articulated chassis <NUM> having a first, front subframe <NUM> and a second, rear subframe <NUM>. The front and rear subframes <NUM> and <NUM> are connected to one another via a pivot connection <NUM> and are supported on the ground via the front and rear drum assemblies <NUM> and <NUM>, respectively. The pivot connection is preferably oriented along a longitudinal centerline <NUM> of the machine <NUM>, which is shown in <FIG> as the front and rear subframes <NUM>, <NUM> are colinear indicative of the machine <NUM> traveling in a straight line. When the machine <NUM> is turning, at least one of the front and rear subframes <NUM>, <NUM> is pivoted about the pivot connection <NUM> to deviate from the longitudinal centerline <NUM>. The longitudinal centerlines of the two subframes <NUM> and <NUM> nevertheless intersect at the pivot connection <NUM>.

As shown in <FIG> and <FIG>, the pivot connection <NUM> is formed from an upper pivot 62A and a lower pivot 62B. The pivots 62A and 62B are identical to one another. The following discussion of "pivot connection <NUM>" applies equally to both pivots 62A and 62B unless otherwise noted.

Still referring to <FIG> and <FIG>, pivot connection <NUM> includes first and second ear mounts <NUM>, <NUM> extending rearwardly from the rear of the front subframe <NUM>, forwardly from the front of the rear subframe <NUM>, respectively, and a pivot pin <NUM> extending vertically through aligned bores in the front and rear ear mounts <NUM>, <NUM>. Articulation and, thus, steering, occurs about the pin <NUM>. A sensor also is provided to measure the steering angle of the machine, i.e., the angular orientation of the font subframe <NUM> relative to the rear subframe <NUM>. In the present embodiment, the steering angle sensor takes the form of a position sensor <NUM> disposed so as to measure the angular orientation of the front and rear subframes <NUM>, <NUM> about the pivot connection <NUM>. In the representative embodiment of the invention, the position sensor <NUM> is located on the upper pivot 62A, however, it may be located at the lower pivot 62B. Other embodiments of the invention may include any number of pivot connections <NUM>. As a result, the position sensor <NUM> may be located at any of the pivot connections <NUM> of the machine <NUM>. Further aspects of the position sensor <NUM> are described below.

The machine <NUM> is steered by at least one steering actuator <NUM> extending between the front and rear subframes <NUM>, <NUM> along one or more lines offset from the center of the pivot axis of the articulated subframes <NUM>, <NUM> and the pivot connection <NUM>. In the representative embodiment of the invention, the steering actuator <NUM> is in the form of two double acting hydraulic cylinders 32A, 32B disposed on opposed sides of the longitudinal centerline <NUM>. Extension and retraction of the hydraulic cylinders 32A, 32B causes the subframes <NUM>, <NUM> to pivot relative to one another, thereby steering the machine <NUM>. Alternative embodiments of the invention may use a single hydraulic steering cylinder <NUM> that extends and retracts to cause the subframes <NUM>, <NUM> to pivot about the pivot connection <NUM>. Yet other embodiments of the invention, may include a steering actuator <NUM> other than a hydraulic cylinder, for example, a pneumatic actuator or other electromechanical actuators. The hydraulic cylinders 32A and 32B are mirror images of one another. All discussion of hydraulic cylinders <NUM> herein apply equally to both hydraulic cylinders 32A and 32B unless otherwise noted.

Because the angular orientation of the pivot connection <NUM> is indicative of the stroke of the hydraulic steering cylinder <NUM>, the position sensor <NUM> is able to provide data indicative of the stroke of the hydraulic steering cylinder <NUM> based on the angular orientation of the pivot connection <NUM>. In other embodiments of the invention, the position sensor <NUM> may be located in other locations, such as, but not limited to, on the hydraulic steering cylinder <NUM> to measure the stroke of the hydraulic steering cylinder <NUM>. Further yet, the position sensor <NUM> may be in the form GPS sensors position on the front and rear subframes <NUM>, <NUM> that measure the relative orientation and position of the front and rear subframes <NUM>, <NUM> and, in turn, measure the resulting stroke of the hydraulic steering cylinder <NUM>. In sum, the position sensor <NUM> is configured to provide data regarding the steering angle of the machine <NUM> and/or the stroke of the hydraulic steering cylinder <NUM> - one being dependent on the other.

The chassis <NUM> may have a narrow width, such as about <NUM> inches (<NUM>) wide, to permit the machine <NUM> to be used to compact the bottom of relatively narrow trenches for laying pipeline and the like. The front subframe <NUM> may support a prime movere (not shown) accessible via a hood <NUM>. The prime mover may, for example, be a gasoline engine, a diesel engine, or an electric motor. The term "engine" as used herein is understood to apply to these and any other suitable prime movers. Either subframe <NUM> or <NUM> may support a control system for the machine <NUM> as well as an enclosed storage compartment accessible via a pivotable cover <NUM> on a rear hood <NUM>. In the present case, the front subframe supports the control system. As is generally understood in the art, each of the front and rear drum assemblies <NUM> and <NUM> may be excited to vibrate by a dedicated exciter assembly (not shown) that is powered by a drive system. Each exciter assembly typically comprises one or more eccentric masses (not shown) mounted on a rotatable shaft(s) (not shown) positioned within an axle housing. Rotation of each eccentric mass imparts vibrations to the associated axle housing and, in turn, to the remainder of the drum assembly. In this way, the front and rear rotating drum assemblies <NUM> and <NUM> are operable to compact the ground.

The machine <NUM> includes at least one receiver for receiving signals from a transmitter on the remote control device <NUM>. The receiver may be a transceiver that both sends and receives signals. In the present example in which the machine <NUM> is controlled by RF or another line of sight signal, the machine <NUM> includes receivers or eyes <NUM>, <NUM> located at the front and rear ends of the machine <NUM>, respectively. In the representative embodiment of the invention, a supplemental third receiver or eye <NUM> is provided at a location between the first and second eyes <NUM>, <NUM>.

Each of the eyes <NUM>, <NUM>, and <NUM> of the illustrated embodiment is an IR photodetector. However, each eye <NUM>, <NUM>, <NUM> could be configured to detect signals in other spectrums in addition not or instead of signals transmitted in the IR spectrum. In varying embodiments of the invention, the trench roller <NUM> may include any number of eyes distributed between the front and rear subframes <NUM>, <NUM>. Each of the eyes <NUM>, <NUM>, and <NUM> includes a receiver and related circuitry forming a module within the machine <NUM>.

Electronics of the machine <NUM> receive signals from the eyes <NUM>, <NUM>, and <NUM> to start and stop the machine <NUM>, to control propulsion and steering of the machine <NUM> in a desired (forward or reverse) direction, and to control the machine's exciter assemblies.

Alternatively, the transmitter may transmit a radio signal or another signal that does not require line of sight, and the receiver may be configured to receive that signal.

The machine <NUM> is controlled by an operator <NUM> via a hand-held remote control device <NUM> that transmits signals to the receiver on the machine. In the present example, the transmitted signal is an IR signal <NUM>. However, as mentioned above, the signal could be radio signal or another signal that need not rely on line of sight. The remote control <NUM> can be actuated to control some or all operating parameter of the machine. For example, it can be used to start and stop the engine. It also can be used to control the FORWARD/REVERSE direction of machine travel and to steer the machine <NUM>, using a direction control <NUM> such as joysticks on the remote control <NUM>. Remote control <NUM> also can be used to control the machine's vibrations as generated by the exciters, including at least an "ON/OFF" control and possibly including controlling vibration intensity as well such as via a "HIGH/LOW" control. The IR signal <NUM> can be set to one of several different control channels in order to allow multiple machines to operate in the same area without interference from one another. This function can be controlled, for example, by a channel selection switch on the remote control <NUM>. The remote control <NUM> performs these functions by transmitting an IR signal <NUM> from a transmission device <NUM> (<FIG>). The transmitted signal <NUM> propagates from the remote control <NUM> in an expanding arc until it impinges on the machine <NUM>. The signal <NUM> is received by one or more of the eyes <NUM>, <NUM>, and <NUM> on the machine <NUM>, transmitted to the machine's circuitry, and decoded to execute the commands transmitted by the remote control <NUM>.

<FIG> depicts the machine <NUM> disposed within a trench <NUM> including reinforcement or "trench shoring" that often takes the form of vertical reinforcing sheets or walls <NUM> located along each side wall of the trench <NUM>. A number of cross supports <NUM> extend laterally between the walls <NUM> near a top edge <NUM> of the trench <NUM>. In the instance shown in <FIG>, the front eye <NUM> is outside of the second reception zone of the remote control <NUM> because it is not within the arc of the IR signal <NUM>. In addition, the rear eye <NUM> is in a dead zone consisting of the shadow located downstream of one of the cross supports <NUM> in the direction of IR signal propagation. The dead zone is bordered by the line <NUM> in <FIG>. However, even though transmission to the rear eye <NUM> is blocked by the obstruction <NUM>, the machine <NUM> nevertheless continues to be controlled because the signal <NUM> is still received by the third eye <NUM>, which is positioned in a common reception zone with the second eye <NUM>.

Referring now to <FIG>, the remote control <NUM> may be configured to transmit two separate signals simultaneously. The first signal <NUM> is a relatively high-intensity control signal <NUM> having a range on the order of <NUM>-<NUM> ft (<NUM>-<NUM>). This signal is often called a far field signal. The second signal <NUM> is a relatively low-intensity safety signal <NUM> having a range of about <NUM> ft (<NUM>). This signal often is called a near field signal. The safety or near field signal <NUM> may be generated whenever the remote control <NUM> is active and causes the machine <NUM> to cease moving and vibrating upon machine receipt of the safety signal <NUM> via one or more of the eyes <NUM>, <NUM>, <NUM>. The machine <NUM> thus stops moving and vibrating if an operator <NUM> is located in a safety zone of about a <NUM> radius from the machine <NUM>.

Referring next to <FIG>, a schematic diagram of the machine <NUM> and the remote control <NUM> and their respective internal components is shown. The machine <NUM> includes a machine control unit <NUM> configured to interact with sensors <NUM>, such as the position sensor <NUM>. Other sensor(s) <NUM> may be included to provide information concerning the operational status of the machine <NUM>, the compaction state of the surface being compacted, etc. The machine control unit <NUM> is also in communication with one or more receivers <NUM>, such as eyes <NUM>, <NUM>, <NUM>, that receive a signal from the remote control <NUM>. The machine control unit <NUM> is configured to use signals from the sensors <NUM> and/or the receiver <NUM> to control the hydraulic steering cylinder <NUM> and other controlled components <NUM> of the machine <NUM>, such as the motor and rollers <NUM>, <NUM>.

The remote control <NUM> includes a direction control <NUM>, typically in the form of a joystick. However, other alternatives of the invention may include other direction controls, such as, but not limited to levers, buttons, toggle switches, etc. The remote control <NUM> further includes transmission device <NUM> which, as stated above, is configured to transmit a signal generated by the direction control <NUM> to the machine <NUM>. As discussed above, the signal may be received by the eyes <NUM>, <NUM>, <NUM> and/or an alternative receiver <NUM> and relayed to the control unit <NUM>. It is contemplated that a separate control device may also be included in the remote control <NUM> to receive inputs from the direction control <NUM> and generate the signal(s) transmitted by the transmission device <NUM>. The above-described machine control unit <NUM> and any such control device may be integrated into any other components discussed above within or exterior to the machine <NUM> and/or the remote control <NUM>.

<FIG> further illustrates the actuator <NUM> in the form of hydraulic cylinders with an associated hydraulic circuit <NUM>. A single hydraulic circuit <NUM> may control operation of both hydraulic steering cylinders 32A and 32B (shown as a single hydraulic steering cylinder <NUM> in <FIG>) and the other components of the machine <NUM> operated by hydraulic pressure via lines L1, L2, L3, and L4 of the hydraulic circuit <NUM>. A pump <NUM> and a reservoir or tank <NUM> within the hydraulic circuit <NUM> are able to provide the necessary hydraulic pressure to L1, L2, L3, L4 in order to operate the components of the machine <NUM>. The hydraulic circuit <NUM> also includes a relief valve <NUM>.

The hydraulic steering cylinder <NUM> is shown as having first and second fluid chambers 132A and 132B. A valve <NUM> is disposed at the hydraulic steering cylinder <NUM> in order to control hydraulic fluid flow into and out of the chambers 132A and 132B to extend and retract the hydraulic steering cylinder <NUM>. The illustrated valve is a three way, three position electronically-actuated solenoid valve. It could be a proportional control valve, which would permit variation of the operating speed of the hydraulic cylinder. However, a less expensive valve lacking proportional control capability, such as an on/off solenoid valve, could be used as well for reasons detailed below. In the illustrated position, the valve <NUM> isolates both chambers 132A, 132B from the pump <NUM> and the reservoir <NUM> to hydraulically lock the hydraulic steering cylinder <NUM> in position. In order to extend the hydraulic steering cylinder <NUM>, the valve <NUM> is switched to a position in which fluid flows into the chamber 132B from the pump <NUM> and flows out of the chamber 132A toward the reservoir <NUM>. Conversely, in order to retract the hydraulic steering cylinder <NUM>, the valve <NUM> is switched to a position in which fluid flows into the chamber 132A from the pump <NUM> and flows out of the chamber 132B toward the reservoir <NUM>.

As described above, the machine control unit <NUM> is configured to use data received from the sensors <NUM> and/or signals received by the receiver <NUM> to control the hydraulic steering cylinder <NUM>. More specifically, the machine control unit <NUM> sends control signals to the hydraulic solenoid valve <NUM> to control the stroke of the hydraulic steering cylinder <NUM> and, therefore, to effect steering of the machine <NUM>.

As stated above, the receiver <NUM> is configured to receive signals from the remote control <NUM> and, more specifically, signals indicative of user input in the direction control <NUM> of the remote control <NUM>. For example, in response to the operator <NUM> moving the direction control <NUM> to the right or left, the remote control <NUM> sends a signal to the machine control unit <NUM> that the operator <NUM> wants the machine <NUM> to steer to the right or left, respectively. In turn, the machine control unit <NUM> can control the valve <NUM> to adjust the stroke of the steering cylinder <NUM> to adjust the steering angle of the machine <NUM>.

The instruction from the machine control unit <NUM> to the valve <NUM> is based on both the input from the operator <NUM> on the remote control <NUM> and input of the position sensor <NUM>. The position sensor data is indicative both of the steering angle of the machine <NUM> and the stroke of the steering cylinder <NUM>. The machine control unit <NUM> can use this data as feedback to control steering cylinder <NUM> operation to achieve the directional control commanded by the existing control (joystick) stroke. For instance, and as will be described later with respect to <FIG>, the machine control unit <NUM> is able to determine whether the stroke of the steering cylinder <NUM> needs to be adjusted (either extended or retracted) to adjust the steering angle of the machine <NUM> to match the operator-generated steering command of the direction control <NUM>. Additionally, when the direction control <NUM> of the remote control <NUM> returns to neutral, the machine control unit <NUM> is configured to adjust the stroke of the steering cylinder <NUM> to a neutral position that causes straight-ahead travel, preventing undesired turns.

The machine control unit <NUM> is also able to use the data received from the position sensor <NUM> to determine whether the steering cylinder <NUM> is disposed at a limit of its stroke, which may be either a maximum (fully-extended) or minimum (fully-retracted) stroke. This can be a simple mathematically calculation based on a known correlation between machine steering angle as measured by position sensor <NUM> and steering cylinder position. In a situation in which the operator actuates the direction control <NUM> to request an additional change in steering angle in a given direction when the steering cylinder <NUM> stroke is at a limit, i.e., is fully extended or retracted, the machine control unit <NUM> overrides the command from the remote control <NUM> and belays the transmission of an instruction to the valve <NUM> to adjust fluid flow into and out of the chambers 132A, 132B to attempt to alter the stroke of the steering cylinder <NUM>. As a result, the machine control unit <NUM> prevents an unnecessary buildup of pressure within the steering cylinder <NUM>, which would normally result in activation of the relief valve <NUM> and a resulting significant draw of mechanical power from the engine to operate the relief valve <NUM>. By preventing attempted over-steering and a need for activation of the relief valve <NUM>, the machine <NUM> is able to maintain efficient use of the mechanical power of the engine without employing a proportional control valve as the valve <NUM>.

Now referring to <FIG>, a flowchart is shown depicting the control of the machine <NUM> by the machine control unit <NUM> based on an operator-generated steering command received from the remote control <NUM> and data received from the position sensor <NUM>. The process begins at blocks <NUM> and <NUM>, which may happen in any order or simultaneously. In block <NUM>, the machine control until <NUM> receives data from the position sensor <NUM>. As stated above, the data received from the position sensor <NUM> is indicative of the steering angle of the machine <NUM> as reflected, directly or indirectly, by the angular orientation of the pivot connection <NUM> between the first and second subframes <NUM>, <NUM>. In block <NUM>, the machine control unit <NUM> receives the operator-generated steering command input from the direction control <NUM> of remote control <NUM>.

In block <NUM>, the machine control unit <NUM> determines whether the stroke of the hydraulic steering cylinder <NUM> needs to be adjusted (extended or retracted) in response to the data received from the position sensor <NUM> and the operator-generated steering command input received from the direction control <NUM>. Where, as here, steering is controlled by a joystick, a change in joystick stroke generates a command to adjust hydraulic steering cylinder stroke. If the machine control unit <NUM> determines that the stroke of the hydraulic steering cylinder <NUM> needs to be adjusted to adjust the turning radius, the process moves to block <NUM>, wherein the machine control unit <NUM> determines whether the stroke of the hydraulic steering cylinder <NUM> is at an operational limit (maximum stroke or minimum stroke). As previously discussed, the machine control unit <NUM> is able to determine the stroke of the hydraulic steering cylinder <NUM> using the steering angle determined using data from the position sensor <NUM>. If the machine control unit <NUM> determines that the stroke of the hydraulic steering cylinder <NUM> is at an operational limit, the process proceeds to block <NUM>, where the machine control unit <NUM> overrides the command from the joystick to prevent the valve <NUM> from attempting to adjust the stroke of the hydraulic steering cylinder <NUM>. By preventing an attempt to adjust the stroke of the hydraulic steering cylinder <NUM> beyond its operational limit, the machine control unit <NUM> is able to prevent activation of the relief valve <NUM> and maintain the efficiency of the machine <NUM>. After block <NUM>, the process returns to blocks <NUM> and <NUM> to continue efficient operation of the machine <NUM>. Returning to block <NUM>, if the machine control unit <NUM> determines that the stroke of the hydraulic steering cylinder <NUM> is not at an operational limit, the process continues to block <NUM>, in which the control unit <NUM> operates the valve <NUM> to adjust the stroke of the hydraulic steering cylinder <NUM> in response to the change in joystick position. The routine then returns to blocks <NUM> and <NUM>.

Returning to block <NUM>, if the machine control unit <NUM> determines that the steering angle does not need to change and the stroke of the hydraulic steering cylinder <NUM> thus does not need to be adjusted, the process moves to block <NUM>. In block <NUM>, the machine control unit <NUM> determines whether the directional joystick has returned to its neutral position, either under active control by the operator or automatically upon release by the operator. If so, the process proceeds to block <NUM>, where the control unit <NUM> operates the valve <NUM> to return the hydraulic steering cylinder <NUM> to its neutral position, resulting in straight-line travel.

Returning back to block <NUM>, if the machine control unit <NUM> continues determines that the joystick has not returned to its neutral position, and thus as not changed since block <NUM>, the process proceeds to block <NUM> where the machine control unit <NUM> operates the valve <NUM> to maintain the existing stroke of the hydraulic steering cylinder <NUM>. As a result, if the operator-generated steering command input is indicative of wanting the maintain the existing turning radius of the machine <NUM>, the machine control unit <NUM> is able to maintain the existing position of the hydraulic steering cylinder <NUM> in order to maintain the turning radius of the machine <NUM>. The process then returns to blocks <NUM> and <NUM>.

While decision blocks <NUM>, <NUM>, <NUM> are shown in a specific order, it is contemplated that these decision blocks may occur in any order to result in the same outcomes identified in the flowchart of <FIG>.

Although the best mode contemplated by the inventors of carrying out the present invention is disclosed above, practice of the above invention is not limited thereto. It will be manifest that various additions, modifications, and rearrangements of the features of the present invention may be made without deviating from the scope of the appended claims.

Claim 1:
A compaction machine system comprising:
a compaction machine (<NUM>) including:
a mobile chassis (<NUM>), the mobile chassis (<NUM>) including a first subframe (<NUM>) pivotably connected to a second subframe (<NUM>) about a pivot connection (<NUM>);
a steering actuator (<NUM>) configured to cause the first and second subframes (<NUM>, <NUM>) to pivot with respect to one another;
a steering angle sensor configured to provide data indicative of a machine steering angle;
a control unit (<NUM>) in communication with the steering angle sensor and the steering actuator (<NUM>), the control unit (<NUM>) being configured to control operation of the steering actuator (<NUM>) and to determine an operational stroke of the steering actuator (<NUM>),
a remote control (<NUM>) exterior to the compaction machine (<NUM>), the remote control (<NUM>) including a direction control (<NUM>) and a transmitter configured to transmit an operator-generated steering command from the direction control (<NUM>) to a receiver on the control unit (<NUM>) of the compaction machine (<NUM>);
wherein the control unit (<NUM>) is configured to control the steering actuator (<NUM>) based on the operator-generated steering command from the direction control (<NUM>) and the determined operational stroke of the steering actuator (<NUM>); and
characterized in that
the control unit (<NUM>) is configured to determine, based on input from the steering angle sensor, whether the steering actuator (<NUM>) is at a limit of its operational stroke and, if so, to override commands from the direction control (<NUM>) to alter the machine steering angle beyond that which results in the limit of the operational stroke of the steering actuator (<NUM>).