Patent ID: 12208834

DETAILED DESCRIPTION

Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the features, as claimed. As used herein, the terms “comprises,” “comprising,” “having,” including,” or other variations thereof, are intended to cover a non-exclusive inclusion such that a method or apparatus that comprises a list of elements does not include only those elements, but may include other elements not expressly listed or inherent to such a method or apparatus. In this disclosure, relative terms, such as, for example, “about,” “substantially,” “generally,” and “approximately” are used to indicate a possible variation of ±10% in the stated value or characteristic.

FIG.1illustrates an exemplary machine steering system10for straight-line steering assistance of a mobile machine12. Machine steering system10may include machine12, such as a track-type tractor, excavator, hauling truck, or other machine useful for performing work and/or off-highway travel, an orientation sensor such as a yaw rate sensor22and/or a position sensor24, and an electronic steering assistance device26(also referred to herein as a steering correction device) for generating steering commands in response to inputs provided by an operator of machine12and based on one or more sensors of steering system10.

Machine12may include a frame14connected to a chassis that supports machine12on one or more ground-engaging devices16such as tracks (shown inFIG.1) or wheels. Machine12may also include an operator cabin15having one or more input devices20, an implement18such as a bucket, blade, ripper, dump body, etc., a positioning system for moving implement18(e.g., a hydraulic system, a pneumatic system, etc.), and an energy source that provides propulsion power for machine12, such as an internal combustion engine, a fuel cell, an energy storage device (one or more battery packs), etc.

Machine12may be configured for manual operation in which components of machine12respond to inputs generated by an operator. As used herein “manual” operation includes control of machine12by an operator physically located within cabin15, or remote operation in which an operator is located outside of cabin15and controls the machine with the use of one or more remote input devices20located outside of machine12, such as at an off-site location. These remote input devices20may be connected to machine12over a wired or wireless network via one or more computing systems and, if desired, may simulate an input device20that is present in cabin15.

Whether machine12is manually operated from within cabin15or from outside of machine12, machine12may be configured to receive a steering command. When controlled or operated from within cabin15, the steering command may be received from input device20. Input device20may include a joystick (shown inFIG.1), a foot-pedal, a lever, or a steering wheel. If desired, input device20may include other devices, such as a touch screen interface, one or more physical buttons, switches, etc. Input device20may be configured to generate a command, or request, to direct the machine in a straight path. When input device20is a joystick or steering wheel, this request may correspond to a neutral position of the joystick or wheel and/or the absence of a change to the position of input device20. Additionally or alternatively, input device20may include one or more buttons or switches that, when actuated, generate a command or request to direct the machine in a straight path.

FIG.2is a top view of machine steering system10, illustrating machine12traveling on a worksite. Machine12may include at least one ground-engaging device16that is responsive to commands issued by input device20to steer machine12in a desired direction30. When ground-engaging device16includes tracks, as shown inFIGS.1and2, the steering direction of machine12may be controlled by setting and/or adjusting the speeds of the individual tracks. In embodiments where machine12includes wheels, the wheels may be repositioned to control the direction of travel of machine12.

System10may include one or more components for monitoring a steering direction of machine12, represented as an actual steering direction32, and for monitoring an actual orientation of machine12. These components of system10, which may include an orientation sensor (yaw rate sensor22and/or position sensor24) and steering assistance device26, may enable detection of actual direction32for comparison to a requested or desired orientation or direction30set with input device20, to determine a steering error34.

When the orientation sensor of system10includes yaw rate sensor22, yaw rate sensor22may be located within frame14. In particular, yaw rate sensor22may be connected to a chassis of machine12. Yaw rate sensor22may be included in group of sensors, such as a group of sensors of an inertial measurement unit (“IMU”). An IMU may contain a plurality of inertial sensors, one or more of these sensors being a yaw rate sensor (e.g., a sensor configured to detect changes in position about a vertical axis). The yaw rate (velocity of movement around an axis extending vertically through machine12) measured by sensor22may be changes in yaw over a predetermined period of time. These changes in yaw may be measured with one or more Coriolis elements. In particular, yaw rate sensor22may be configured to detect the rate of rotation, or yaw28, about a vertical axis, and in particular, a yaw28of machine12that can be represented in radians or degrees per second. If desired, yaw rate sensor22may be a standalone sensor (e.g., a sensor that only measures rotation about a vertical axis).

When the orientation sensor of system10includes position sensor24, position sensor24may be configured to determine an instantaneous rotational position of machine12. In one configuration, position sensor24may include a global navigation satellite system (GNSS) receiver or a global positioning system receiver that is configured to monitor a position of machine12over time. Position sensor24may enable steering assistance device26to receive a plurality of positions or orientations of machine12over a period of time during which machine12receives a request to travel in a straight direction.

While the orientation sensor may include yaw rate sensor22, position sensor24, or both, as described above, other types of sensors may be configured to identify disturbances that cause a change in the yaw of machine12. For example, the orientation sensor may include one or more vision devices (e.g., a stereo camera system), LIDAR, radar, etc. A vision device, LIDAR, radar, or other observation system may enable detection of the position of one object or surface, or a plurality of objects or surfaces. By monitoring apparent changes in the position of stationary objects or surfaces, the vision device or other orientation sensor may enable identification of a change in orientation of machine12, as compared to these stationary objects or surfaces.

Steering assistance device26may be an electronic control unit programmed to receive inputs and control one or more aspects of machine12. While steering assistance device26may be a standalone device that is configured to generate a command for adjusting steering of machine12, steering assistance device26may be configured to control other aspects of machine system10. For example, steering assistance device26may be part or an electronic control module that is configured to control an internal combustion engine of machine system10, a position for positioning implement18, or other components of machine system10.

Steering assistance device26may be enabled, via programming, to generate outputs (e.g., steering command adjustment128shown inFIG.3) for counteracting disturbances encountered by machine12when machine12operates in a straight-line mode. Steering assistance device26may be configured to receive signal(s) output from the orientation sensor, such as orientation data, and, based on the received signal(s), identify changes in orientation that cause a change in the yaw rate of machine12. In an exemplary configuration, steering assistance device26may be configured to identify steering disturbances, such as changes in an orientation of machine12in the absence of a request to change the orientation of machine12. In some configurations, steering assistance device26may identify a change in orientation and/or a steering disturbance based on a yaw rate (e.g., a rate of change of yaw28detected with yaw rate sensor22), or, if desired, a change in yaw28measured with position sensor24. Based on the yaw rate, position, and/or other information received by steering assistance device26, steering assistance device26may generate an output to control the steering of machine12in a manner that counteracts the steering disturbance, thereby correcting steering without the need of an operator to manually counteract the steering disturbance by interacting with input device20.

FIG.3is a block diagram representing an exemplary configuration of steering correction device26. Steering correction device26may be a control unit embodying a single microprocessor or multiple microprocessors that receive inputs (e.g., yaw rate112, steering command114, and travel direction124), and generate outputs (e.g., steering command adjustment128). Steering correction device26may include a memory, a secondary storage device, a processor such as a central processing unit, or any other means for accomplishing a task consistent with the present disclosure. The memory or secondary storage device associated with steering correction device26may store data and software to allow steering correction device26to perform its functions, including the functions described with respect toFIG.3and one or more steps of method400, as described below. Numerous commercially available microprocessors can be configured to perform the functions of steering correction device26. Various other known circuits may be associated with steering correction device26, including signal-conditioning circuitry, communication circuitry (e.g., for enabling remote control of machine12), and other appropriate circuitry.

As shown inFIG.3, steering correction device26may receive, as inputs110, a yaw rate signal112, a steering command signal114, and a travel direction signal124. Yaw rate signal112may indicate an instantaneous yaw rate, a yaw rate over a predetermined period of time, or particular change in yaw over a predetermined period of time, each of which can represent an amount of deviation of machine12. Yaw rate signal112may include another signal indicative of a steering disturbance that changes the orientation (e.g., yaw) of machine12this signal also representing an amount of deviation of machine12. In an exemplary configuration, yaw rate signal112may be generated by yaw rate sensor22and may provide orientation data that is received by steering correction device26. However, yaw rate signal112may instead be a calculated yaw rate based on a type of orientation sensor other than a yaw rate sensor, such as position sensor24. Steering command114may be generated with input device20, either in cabin15or at a remote location outside of machine12. Travel direction signal124may be received by steering correction device26to indicate a direction of travel of machine12, such as a forward direction or a reverse direction. Travel direction signal124may correspond to the position of a forward-neutral-reverse or “FNR” lever to indicate a requested direction of travel to steering correction device26.

An enable module116of steering correction device26may be configured to determine when steering correction device26is permitted to enter a steering assist mode, also referred to herein as a “straight line mode,” during which steering correction device26is enabled to generate steering corrections. Enable module116may be configured to generate an enable signal118for permitting the straight line mode. Enable signal118may be received by a yaw rate integrator120which, in response to the enable signal118, generates a yaw error122. While signal118is described as an enable signal, if desired, signal118may instead be a disable signal that causes yaw rate integrator120to cease outputting yaw error122. Yaw rate integrator120may be configured to receive yaw rate signal112and integrate the yaw rate to generate a yaw error122. Yaw error122may represent a positional error, or a heading error, corresponding to the deviation of machine12from a straight path, this positional error being instantaneous or corresponding to the predetermined or incremental period of time.

Steering corrector126may receive yaw error122and travel direction signal124and, based on these signals, generate a suitable steering command adjustment128. Steering corrector126may be configured to determine the magnitude of steering error (e.g., steering error34shown inFIG.2) between a current heading or orientation of machine12(e.g., actual direction32) and the last direction requested by an operator (e.g., desired direction30). Steering corrector126may receive yaw error122representing an instantaneous or incremental yaw error. Steering corrector126may be configured to accumulate a plurality of instantaneous or incremental yaw errors122to calculate a current steering error34(FIG.2), which corresponds to the current, accumulated, steering error. Thus, steering corrector126may enable steering correction device26to monitor changes between desired direction30and actual direction32over time.

Steering corrector126may calculate a command for returning machine12towards desired direction30based on a magnitude and direction of steering error34. For example, steering corrector126may determine a steering command adjustment128by retrieving a value from one or more maps, look-up tables, or other data storage structures that permit steering corrector126to generate steering command adjustment128. Steering command adjustment128may modify the operation of ground-engaging devices16, such as by adjusting a speed of a track relative to another track or adjusting an angular position of one or more wheels. In particular, steering corrector126may calculate steering error34in the form of an angular offset, such as a number of degrees, and multiply this steering error34by a gain to calculate the direction and magnitude for steering command adjustment128. Steering command adjustment128may be provided to another controller (e.g., a PID controller) or may be output to an actuator that alters the speed and/or position of ground-engaging devices16to seek a steering error of zero.

In some aspects, steering corrector126may include safeguards to prevent large steering corrections. For example, when yaw rate112, yaw error122, or an accumulated steering error34exceeds a predetermined threshold, steering command adjustment128may be limited to a predetermined maximum value. Thus, the maximum amount of adjustment permitted by steering corrector126may be limited. Additionally or alternatively, steering corrector126may be disabled when one or more of yaw rate signal112, yaw error122, or steering error34exceeds a maximum permitted value.

INDUSTRIAL APPLICABILITY

System10may be useful in any machine12that is configured for manual operation by an on-site and/or remote user. Suitable machines12may include machines such as track-type tractors, motor graders, excavators, hauling trucks, etc., having tracks or wheels that propel the machine in response to commands issued during this manual operation. Machine12may be propelled by any suitable power-generation device, such as an internal combustion engine, fuel cell, battery pack, etc.

With reference toFIG.4, a method400for steering correction may be performed during the operation of machine12, and in particular, when machine12travels in a worksite. Method400may be performed continuously during propulsion of machine12, or intermittently during propulsion of machine12. Machine12may be propelled during method400in response to a request from an operator within cabin15or a remotely-positioned operator manually operating machine12by interacting with an input device20such as a foot pedal, lever, button(s), etc. Method400may include performing work with machine12while machine12is propelled. In examples where machine12is an earthmoving machine, this work may involve transporting material or grading material by engaging material with an implement18in the form of a blade or bucket. However, method400may also be performed without performing work, such as when implement18is actuated to a raised position. Method400may enable steering adjustment or correction when machine12is manually operated, regardless of whether machine12is performing work or travelling without performing work.

A step402of method400may include detecting a steering request with steering correction device26. This steering request may be a request to travel in a straight direction. As an example, step402may include detecting (e.g., receiving) a steering command114generated with one or more input devices20. Steering command114may correspond to a neutral position of input device20, or may be generated by interacting with a switch, button, touchscreen interface, or other suitable device for requesting straight-line travel. During the straight-line mode, steering command114may indicate the absence of a request to steer machine12away from a straight direction.

In step404, enable module116may determine that the steering request detected in step402reflects a request to propel machine12in a straight direction. When input device20is a joystick, enable module116may generate an enable signal118that indicates straight-line travel when the joystick remains in a neutral position with respect to a left-right direction of machine12. Enable signal118may cause steering corrector126of steering correction device26to enter a steering assist mode, and in particular, a straight-line mode.

A step406may include determining a deviation of machine12from a desired direction. For example, as described above, yaw rate integrator120may receive yaw rate signal112, which constitutes orientation data and that is integrated or otherwise transformed to calculate yaw error122, representing an instantaneous deviation or a deviation measured during a predetermined period of time (e.g., by sampling yaw rate signal112).

A step408may include generating an adjusted steering command, such as steering command adjustment128. The steering command adjustment128may correct the current steering error34and seek a steering error of zero. When steering correction device26is included in a system10for a track-type machine, as shown inFIG.1, steering command adjustment128may cause a modification in the speed of one track with respect to another. In machines that include wheels, steering command adjustment128may cause a change in the angle of the wheels with respect to frame14of the machine.

In addition to steps402,404,406, and408, method400may include one or more steps or actions for disabling the straight-line mode and/or limiting the corrections permitted during the straight-line mode. For example, when input device20is in a position that requests a turn, enable module will not generate enable signal118, and can disable the straight-line mode. Upon detecting a turn, steering corrector126may also reset any accumulated yaw error122. In some aspects, steering correction device26may be programmed with a so-called “dead zone” such that inadvertent or other slight movements of input device20do not disrupt the operation of steering correction device26when in straight-line mode.

Method400may also include taking one or more actions to facilitate consistent operation of the straight-line mode. For example, when a straight-line mode is entered and subsequently terminated (e.g., when input device20is manipulated in a manner that requests a turn), steering correction device26may wait a minimum period of time before permitting another entry into the straight-line mode. For example enable module116may apply a “timeout” period before generating enable signal118to enable a subsequent entry into the straight-line mode.

While steps402,404,406, and408have been described in an exemplary sequence, as understood, one or more of these steps may be performed simultaneously or performed and/or repeated in a different order. Moreover, any two or more of these steps may be performed simultaneously and/or at overlapping periods of time.

The disclosed system and method may facilitate straight-line propulsion of a machine, even when the machine encounters a disturbance that tends to cause the machine to deviate from an intended straight-line path. The system and method may facilitate maintenance of a straight line trajectory when the machine encounters an external disturbance such as a sloped surface, uneven implement (e.g., blade) load, or different soil properties on opposite sides of the machine. Additionally, the system and method may enable the machine to travel along and maintain a straight path when internal disturbances exist, such as left and right tracks that have different track tensions, left and right tires that have different tire pressures, or inefficiencies in a hydraulic system that tend to cause the machine to veer to the left or to the right. The system and method may enable the machine to traverse a straight path, even when one or more external and/or internal disturbances act to disrupt the linear travel of the machine.

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