Patent Application
20160097658
This disclosure relates generally to an implement control system for a machine, and more particularly to systems and methods for determining a position on an implement relative to a reference position on the machine.
Earthmoving machines such as track type tractors, motor graders, scrapers, and/or backhoe loaders, have an implement such as a dozer blade or bucket, which is used on a worksite in order to alter a geography or terrain of a section of earth. The implement may be controlled by an operator or by a control system to perform work on the worksite such as achieving a final surface contour or a final grade on the worksite. Continuously positioning the implement with enough precision to achieve a final grade, however, is a complex and time-consuming task that requires expert skill and diligence if the operator is controlling the movement. Thus, it is often desirable to provide autonomous control of the implement to simplify operator control.
To control the implement autonomously, it is sometimes necessary to determine the accurate position of at least one point on the implement relative to a reference point on the machine. It is also sometimes necessary to determine the precise distance between at least one point on the implement and a reference point on the machine. Determining the accurate relative position and precise relative distance of a point on the implement and a reference point on the machine may require calibrating or updating an implement control system using the position and distance information.
Previous systems relied on sensors to determine the relative movement of each link that connects to the implement in order to determine the position and orientation of the implement. The relative movement of each link, such as a hydraulic cylinder, is sensed and communicated to a controller which then calculates the orientation of the implement. Such systems often need to be calibrated with the machine stationary on a flat surface each time the machine is started. Such systems are also dependent on the accuracy and robustness of each individual sensor.
Such a sensor is disclosed in U. S. Pat. No. 7,757,547 to Kageyama et al., issued Jul. 20, 2010, entitled “Cylinder stroke position measurement device,” discloses an apparatus for determining the stroke of a cylinder using a sensor wheel and a Hall effect sensor. The Kageyama apparatus however is susceptible to dirt that could cause binding or slipping of the sensor wheel. The Kageyama apparatus is further susceptible to hydraulic oil that could cause slipping of the sensor wheel which could cause an inaccuracy in the cylinder stroke measurement.
A system and method that more directly determines the position and orientation of an implement and is less susceptible to dirt and contamination is required.
A system for determining a position and orientation of an implement relative to a frame of a machine is disclosed. The system comprises an implement being attached to and moveable relative to the machine and a fiber optic shape sensing system associated with the implement. The fiber optic shape sensing system comprises an interrogation module mounted to the machine frame, a reference frame fixed to the interrogation module and machine frame, and a fiber bundle joined to the interrogation module at a proximal end and to the implement at a distal end. The interrogation module is configured to receive strain information from the fiber bundle and compute the location of at least one position of the fiber bundle that is associated with the implement relative to the reference frame.
In a second aspect of the current disclosure, a method for determining the position and orientation of an implement relative to a frame of a machine is disclosed. The method comprises providing a fiber optic shape sensing system associated with the implement that comprises an interrogation module mounted to the machine frame, a reference frame fixed to the interrogation module and machine frame, and a fiber bundle joined to the interrogation module at a proximal end and to the implement at a distal end. The method further comprises receiving reflection spectrum information from the fiber bundle in the interrogation module, and computing the location of at least one position of the fiber bundle that is associated with the implement relative to the reference frame.
In a third aspect of the current disclosure, a machine equipped with a system for determining the position and orientation of an implement relative to a frame of the machine is disclosed. The machine comprises a power source, a ground engaging mechanism, an implement attached to and moveable relative to the machine, and a fiber optic shape sensing system associated with the implement. The fiber optic shape sensing system comprises an interrogation module mounted to the machine frame, a reference frame fixed to the interrogation module and machine frame, and a fiber bundle joined to the interrogation module at a proximal end and to the implement at a distal end. The interrogation module is configured to receive strain information from the fiber bundle and compute the location of at least one position of the fiber bundle that is associated with the implement relative to the reference frame.
This disclosure relates to systems and methods for determining a position on an implement relative to a reference position on a machine. An exemplary embodiment of a machine 100 is shown schematically in
In an illustrated embodiment, the machine 100 includes a power source 102, an operator's station or cab 104 containing controls necessary to operate the machine 100, such as, for example, one or more input devices for propelling the machine 100 and/or controlling other machine components. The machine 100 further includes an implement 106, such as, for example, a blade, a bowl, a ripper, or a bucket for moving earth. The one or more input devices may include one or more joysticks disposed within the cab 104 and may be adapted to receive input from an operator indicative of a desired movement of the implement 106. The cab 104 may also include a user interface having a display for conveying information to the operator and may include a keyboard, touch screen, or any suitable mechanism for receiving input from the operator to control and/or operate the machine 100, the implement 106, and/or the other machine components.
The implement 106 may be adapted to engage, penetrate, or cut the surface of a worksite and may be further adapted to move the earth to accomplish a predetermined task. The worksite may include, for example, a mine site, a landfill, a quarry, a construction site, or any other type of worksite. Moving the earth may be associated with altering the geography at the worksite and may include, for example, a grading operation, a scraping operation, a leveling operation, a bulk material removal operation, or any other type of geography altering operation at the worksite.
As illustrated in
The hydraulic mechanisms may include one or more hydraulic lift actuators 114 and one or more hydraulic tilt actuators 116 for moving the implement 106 in various positions, such as, for example, lifting the implement 106 up or lowering the implement 106 down, tilting the implement 106 left or right, or pitching the implement 106 forward or backward. In the illustrated embodiment, the machine 100 includes one hydraulic lift actuator 114 and one hydraulic tilt actuator 116 on each side of the implement 106. The illustration in
The power source 102 is an engine that provides power to a ground engaging mechanism 118 adapted to support, steer, and propel the machine 100. The power source 102 may embody an engine such as, for example, a diesel engine, a gasoline engine, a gaseous fuel-powered engine, or any other type of combustion engine known in the art. It is contemplated that the power source 102 may alternatively embody a non-combustion source of power (not shown) such as, for example, a fuel cell, a power storage device, or another suitable source of power. The power source 102 may produce a mechanical or electrical power output that may be converted to hydraulic power for providing power to the machine 100, the implement 106, and to other machine 100 components.
The machine 100 further includes a frame or machine frame 120 disposed between the implement 106 and the ground engaging mechanisms 118. A position determining system 122 adapted to receive and process position data or signals may be mounted to the machine frame 120 of the machine 100. The position determining device 122 may be a global position satellite (GPS) system receiver. The GPS receiver, as is well known in the art, receives signals from a plurality of satellites and responsively determines a position of the receiver in a site coordinate system 123 relative to the worksite, that is, in a site coordinate system. The site coordinate system 123 may be a Cartesian system having an x-coordinate 124, a y-coordinate 126, and a z-coordinate 128. In alternative embodiments, the position determining system 122 may include other types of positioning systems without departing from the scope of this disclosure, such as, for example, laser referencing systems. The position determining device 122 may include two or more GPS receivers without departing from the scope of the current disclosure. Locations of multiple GPS are fixed and known and their locations may be provided to the controller 304 and fiber optic shape sensing system 260.
The machine 100 further includes an implement control system 130 operatively connected to the input device and to the hydraulic actuators 114, 116 for controlling movement of the implement 106. The control system 130 may direct the implement 106 to move to a predetermined or target position in response to an operators' desired movement of the implement 106 for engaging the implement 106 with the terrain of the worksite. The control system 130 may further direct the implement 106 to move to a predetermined or target position indicative of an automatically determined movement of the implement 106, based in part on, for example, an engineering or site design, a productivity or load maximizing measure, or a combination of site design and productivity measure.
To direct the implement 106 to move precisely in response to an automatically determined movement signal or command, the control system 130 may require certain predetermined measurement data associated with the machine 100 and may need to perform certain predetermined calibrations on other systems and components associated with operating the machine 100. As illustrated in
As illustrated in
For example, the controller 304 may direct the implement 106 to move to a predetermined or target position in response to an input signal received from a grade control system 306, which may direct the implement 106 to cut to a predetermined or target grade profile. To direct the implement 106 to move precisely in response to an automatically determined movement signal, such as, for example, the grade control system 306 signal, the controller 304 may calibrate the grade control system 306 using the measurements A, B, and C to establish initial machine conditions. The controller 304 may also calibrate the machine sensors 300 and/or the implement sensors 302 using the measurements A, B, and C.
As illustrated in
The controller 304 may be further adapted to determine the measurement A, representative of the vertical dimension of the machine 100, based in part on the reference position 132 and the one or more desired points 400, 402. The controller 304 may also be adapted to determine the measurement B and/or the measurement C, which are representative of the horizontal dimensions of the machine 100, based in part on the reference position 132 and the one or more desired points 400, 402. Alternatively, or additionally, the controller 304 may be adapted to determine a measurement (not shown) representative of the distance from the reference position 132 to the one or more desired points 400, 402. The controller 304 may derive or determine the measurements A, B, and C using known algorithms, such as, for example, vector math, and/or using customized algorithms, for example, customized kinematic equations.
It is known that each of the FBGs 210 may be interrogated for strain information. A fiber bundle 190 may contain two or more fiber cores 200 and the FBGs 210 in each fiber core 200 are located at the same length along the fiber core 200. As the index of refraction of a medium depends on stress and strain, the bend direction and axial twist of the fiber core 200 may be determined from the strains in each core's FBG 210. From the strain information from each fiber core 200 at each FBG 210 location along the length of the fiber core 200 the shape of the fiber core 200 can be determined.
A curvilinear coordinate system is defined with an origin at the proximal end of the fiber bundle 190 where it is joined to an interrogation module 220. A fiber termination 192 is located at the distal end of the fiber bundle 190. A Cartesian coordinate system is also defined as a base reference frame 230 having an origin coincident with the curvilinear coordinate system's origin.
To determine the approximate shape of the fiber core 200, the strain information measured at each FBG 210 location is used to determine the approximate local bend for the length of fiber core 200 without FBG 210. For example, the strain information from three fiber cores 200 in a fiber bundle 190 is used to compute the plane and the bend radius of the fiber bundle 190. Segments are defined at various locations along the fiber bundle 190, and each segment ends at a co-located ring of FBG 210 in the three fiber cores 200. Given the Cartesian x,y,z position of the FBG 210 ring being processed (i.e., the segment end position), the position of the next FBG 210 ring can be computed with simple geometry. The position of the first segment's end location with respect to the base frame 230 is then determined from the first segment's bend information. Next, strain information for the second segment is processed to determine the second segment's bend. The second segment's bend information is combined with the position of the first segment's end location to determine the second segment's end location position with respect to the base frame. Thus the position of each segment end location is determined with respect to the base frame 230, and the position information is used to determine the approximate shape of the fiber bundle 190. Accordingly, the position of multiple points along the fiber bundle 190, including the fiber termination 192, relative the base frame 230 can be determined. An example of a 3D representation of the shape of the fiber bundle 190 is shown in
A second use of FBG 210 for the present disclosure employs Optical Frequency Domain Reflectometry (OFDR). This approach uses low reflectivity gratings all with the same center wavelength and a tunable laser source. The FBGs 210 may be located on a single optical fiber core 200. This allows hundreds of strain sensors to be located down the length of the fiber core 200. This configuration allows strain measurements to be acquired at much higher spatial resolution than other current sensor technologies, making it flexible enough to employ a user-selected grating density depending on the type of application.
The principles of operation of the fiber shape sensing concept are known and can be found in U.S. Pat. No. 8,116,601 to Prisco, issued Feb. 14, 2012, entitled “Fiber optic shape sensing,” U.S. Pat. No. 20,130,308,138 to ‘T Hooft et al., issued Nov. 21, 2013, entitled “FIBER OPTIC SENSOR FOR DETERMINING 3D SHAPE,” and U.S. Pat. No. 7,715,994 to Richards et al., issued May 11, 2010, entitled “Process for using surface strain measurements to obtain operational loads for complex structures.”
Referring to
A fiber optic shape sensing system 260 as applied to an implement 106 of a machine 100 is illustrated in
As shown in
The fiber bundle 190 is comprised of a connecting section 194 that spans the distance between the machine frame 120 and the implement 106. The relative position of the proximal end and distal end of the connecting section 194 will change as the implement 106 is lifted and lowered. The change in relative position can be determined by the interrogation module 220 and a signal corresponding to the position of the implement 106 relative to the machine frame 120 is generated and communicated to the position determining system 122 and the controller 304. The position of the implement 106 relative to the machine frame 120 is thereby determined at any position as the implement 106 is lifted and lowered.
The fiber bundle 190 may be further comprised of a vertical section 196 that is mounted to the implement 106. The relative position of the proximal end and distal end of the vertical section 196 will change as the implement 106 is tilted fore and aft or rolled. The change in relative position can be determined by the interrogation module 220 and a signal corresponding to the position of the implement 106 relative to the machine frame 120 is generated and communicated to the position determining system 122 and the controller 304. The tilt position of the implement 106 relative to the machine frame 120 is thereby determined at any position as the implement 106 is tilted fore and aft or rolled.
The fiber bundle 190 may be further comprised of a horizontal section 198. The relative position of the proximal end and distal end of the horizontal section 198 will change as the implement 106 is angled about the yaw axis or rolled. The change in relative position can be determined by the interrogation module 220 and a signal corresponding to the position of the implement 106 relative to the machine frame 120 is generated and communicated to the position determining system 122 and the controller 304. The yaw position of the implement 106 relative to the machine frame 120 is thereby determined at any position as the implement 106 is angled about the yaw axis or rolled.
It will be understood by a person skilled in the art that the vertical section 196 and the horizontal section 198 can be positioned in any order along the fiber bundle 190.
In one aspect of the current disclosure, the fiber bundle 190 may be comprised of a diagonal section 193 rather than a vertical section 196 and a horizontal section 198. The proximal end of the diagonal section 193 is joined to the distal end of the connecting section 194 and the distal end of diagonal section 193 is located at a different location on the implement 106.
The distal end of the diagonal section 193 should be placed a distance from the proximal end of the diagonal section 193 along the plane defined by the implement 106 (y-z plane in
In one aspect of the current disclosure, the fiber bundle 190 may be comprised of a body section 199 as illustrated in
The fiber bundle 190 may be routed any number of ways, such that the interrogation module 220 is mounted to the machine frame 120 and the distal end of the fiber bundle 190 is mounted to the implement 106. Examples include routing the fiber bundle 190 along a push arm 140, the tag link (not shown), or along any harness or hydraulic line that runs between the machine frame 120 and the implement 106.
The fiber bundle 190 may be protected in a hardened shroud at any point along its length. Where the fiber bundle 190 may span a distance that is unsupported by rigid structures, such as is the case with the connecting section 194, the fiber bundle 190 may be protected by a hardened flexible conduit as is known to be used with wiring harnesses and hydraulic lines. The fiber bundle 190 may also include sections that provide strain relief such as coiled sections, curved sections, support springs, and relief bushings.
In one aspect of the current disclosure, the interrogation module 220 and position determining system 122 may be mounted at the same location on the machine frame 120 and may be attached to one another. Such an arrangement may simplify calculations and calibration needed by controller 304 and the fiber optic shape sensing system 260.
According to the current disclosure, the controller 304 is adapted to determine or derive the measurements A, B, and C from the position signals received from the position determining system 122. The controller 304, for example, may be adapted to determine a position of a reference position 132 on the machine 100 in the site coordinate system 123. The reference position 132 or reference position may be representative of an absolute position of the position determining system 122 mounted to the machine frame 120.
As illustrated in
A fiber optic shape sensing system 260 is adapted to determine the position and orientation of an implement 106 relative to a machine frame 120. A position determining system 122 is mounted to the machine frame 120 in a place where the GPS receiver associated with the position determining system 122 has a clear line of sight to space. The position determining system 122 may be mounted to the machine's cab 104 or to a roll-over protection system (ROPS) that is integrated into the cab 104. In either case, the position determining system 122 is considered to be fixed and mechanically grounded to the machine frame 120. In one aspect of the current disclosure, the position determining device 122 may include two or more GPS receivers. The locations of the multiple GPS are fixed and known and their locations may be provided to the controller 304 and fiber optic shape sensing system 260.
The fiber optic shape sensing system 260 includes a fiber bundle 190 that is attached to implement 106. There are various ways to route and attach the fiber bundle 190 to the implement 106 as can be understood by a person skilled in the art. A few such examples are included in, but not limited to, the description and figures of the current disclosure. The routing and attachment method may be chosen depending on the application and may be physically done in a location such as a factory. Whichever routing and attachment arrangement is chosen, the location of each position of the fiber bundle 190, and thereby each FBG 210, is known relative to the implement 106. Therefore, as the orientation of the implement 106 changes as it lifts, tilts, and yaws, the shape of the fiber bundle 190 changes in relation to the interrogation module 220. The shape of the fiber bundle 190 can then be determined and communicated to controller 304. Therefore, the position and orientation of the implement 106 relative to the machine frame 120 can be determined.
The locations of the position determining system 122 and the interrogation module 220 are fixed and known. The locations are known by the designers of the machine frame 120 and the locations are physically fixed at a location such as a factory. The locations can be input into the controller 304. Therefore, the position and orientation of the implement 106 relative to the position determining system 122 can be determined. Furthermore, the position and orientation of the implement 106 relative to the site coordinate system 123 can be determined.
Desired points 400, 402 on the implement 106 may correspond to a cutting or engaging edge. The locations of the desired points 400, 402 in the implement 106 are fixed and known. The positions of the desired points 400, 402 relative to the machine frame 120 and the site coordinate system 123 can be determined. The implement control system 130 can therefore position the desired points 400, 402 at a predetermined location on the site coordinate system 123.
A predetermined surface contour or final grade of a work site may be defined by a site designer or back office and communicated to the implement control system 130. The machine communication system may connect to a site management system and to the implement control system 130 and may include bidirectional transfer of information about the machine 100 and worksite. The implement control system 130 can therefore position the implement 106 in the proper position to achieve the predetermined surface contour or final grade of the work site.
