Patent Application
20130076346
This disclosure relates generally to a system and method for determining the position of a movable member relative to a reference member and, more particularly, to a system and method for determining the position of the movable member in two different directions.
Many systems measure the displacement of a movable member relative to a reference member to determine the location of an element connected to the movable member. For example, knowing the distance that a shaft within a hydraulic cylinder is extended may be sufficient to determine the location of an implement connected to the hydraulic cylinder. In some systems, the location of an element may be determined by monitoring sensors that read or sense the location of indicia positioned on the movable member.
U.S. Patent Application Publication No. 2010/0039103 A1 discloses a system for determining the position of a movable member with respect to a fixed member. The movable member includes a first and second magnet and a secondary magnet. A sensor assembly on the fixed member detects the first and secondary magnets and thus determines the axial position of the movable member relative to the fixed member.
In systems in which the movable member may move in more than one direction, measurement of displacement in a single direction may be insufficient to accurately determine the location of an attached element. In addition, determining the location of an element may be especially complex when the element is driven or connected to more than one movable member. In such case, it may be necessary to determine the movement of each of the movable members in more than one direction to determine the location of the attached element.
The foregoing background discussion is intended solely to aid the reader. It is not intended to limit the innovations described herein nor to limit or expand the prior art discussed. Thus the foregoing discussion should not be taken to indicate that any particular element of a prior system is unsuitable for use with the innovations described herein, nor is it intended to indicate any element, including solving the motivating problem, to be essential in implementing the innovations described herein. The implementations and application of the innovations described herein are defined by the appended claims.
In one aspect, a system for determining the displacement of a moveable member relative to a reference member is provided. The moveable member is configured for movement relative to the reference member along a range of positions in a first direction and in a second direction. A set of sensors is fixed relative to one of the reference member and moveable member. An array of encoded words on another of the reference member and moveable member is provided. The encoded words define the positions of the moveable member along the first direction and a position of the encoded words relative to the set of sensors defines the positions of the movable member along the second direction. Each encoded word includes a plurality of indicia and each indicia is a multi-level logic unit configured as one of at least two states.
In another aspect, a method is provided for determining the displacement of a moveable member relative to a reference member. The moveable member is configured for movement relative to the reference member along a range of positions in a first direction and in a second direction. A set of sensors is provided together with an array of encoded words on the moveable member. The encoded words define the positions of the moveable member along the first direction and includes a plurality of indicia. Each indicia is a multi-level logic unit that is configured as one of at least two states. Upon moving the moveable member relative to the reference member, the indicia of an encoded word aligned with some of the sensors are sensed. The displacement of the moveable member along the first direction is determined based upon the sensed indicia. The displacement of the movable member along the second direction is determined based upon the position of the sensed indicia.
Referring to
In a machine such as motor grader 30 that utilizes multiple hydraulic cylinders to control an implement, rotation of the elongated shaft within some or all of the cylinders may affect the positioning of the implement, As a result, it may be difficult to determine the position of the implement by measuring displacement of the hydraulic cylinders in a single direction. In other words, the position of the implement may be affected by not only the linear displacement of each of the shafts of hydraulic cylinders but also by the rotation of the shafts. Accordingly, some or all of the hydraulic cylinders that control the position of moldboard 35 may include the system 20 for determining the displacement of the shaft of each cylinder in both a first direction along the generally linear path of travel 23 and along a second direction along an arcuate path 24 generally about the axis of rotation 25. Determining both the linear displacement of elongated shaft 22 as well as its rotation may allow the position of the moldboard 35 to be determined based on the positions of the various hydraulic cylinders, and thus simplify the operation of the motor grader 30. Further, utilizing the system 20 may allow the position of the moldboard 35 to be determined by monitoring fewer than all of the hydraulic cylinders that control the moldboard.
Referring to
The indicia 45 may be provided along arcuate outer surface 26 of elongated shaft 22. In one configuration, the indicia 45 may be magnetic elements that are positioned adjacent or below the outer surface 26 of the elongated shaft 22. In another configuration, the indicia 45 may be optically reflective elements that are positioned on the outer surface 26 of the elongated shaft 22. In the embodiment depicted in
A plurality of sensors 50 may be mounted on hydraulic cylinder 21 for sensing the status and position of the indicia 45. More specifically, a first set 51 of sensors may be positioned generally in a first plane 52 and a second set 53 of sensors may be generally positioned in a second plane 54. As best seen in
If desired, the sensors 50 may be positioned within the hydraulic cylinder 21 as depicted in
Controller 55 may be an electronic controller that operates in a logical fashion to perform operations, execute control algorithms, store and retrieve data and other desired operations. The controller 55 may include or access memory, secondary storage devices, processors, and any other components for running an application. The memory and secondary storage devices may be in the form of read-only memory (ROM) or random access memory (RAM) or integrated circuitry that is accessible by the controller 55. Various other circuits may be associated with the controller 55 such as power supply circuitry, signal conditioning circuitry, driver circuitry, and other types of circuitry. The controller 55 may be a single controller or may include more than one controller disposed to control various functions and/or features together with system 20. The functionality of the controller 55 may be implemented in hardware and/or software without regard to the functionality.
One or more data maps relating to the position of the elongated shaft 22 may be stored in the memory of controller 55. Each of these maps may include a collection of data in the form of arrays, tables, graphs, and/or equations. In one example, the position of the elongated shaft 22 along the path of travel 23 and about the arcuate path 24 may be determined by comparing the indicia read or sensed by sensors 50 with the data maps associated with controller 55.
The first set 51 of sensors reads or senses the status of a first encoded word within the array and the second set 53 of sensors reads or senses the status of a second encoded word 48. The array of indicia 45 is configured so that the encoded words sensed by the first set 51 of sensors and the second set 53 of sensors define a unique position of the elongated shaft 22 along the path of travel 23. As depicted, the first set 51 of sensors and a second set 53 of sensors are spaced apart along the path of travel 23 by a distance generally equal to the spacing between the indicia 45 forming the encoded words 48. In such a configuration, the pairs of adjacent encoded words 48 define a plurality of positions of the elongated shaft 22 along the path of travel 23. The spacing between and number of rows 47 of indicia 45 define the number of unique positions of the shaft that may be determined. More specifically, each encoded word 48 defines a position of the elongated shaft 22 along the path of travel 23 and thus the indicia 45 define a range of positions through or along the path of travel. The spacing of the indicia 45 along the path of travel 23 (and thus within each column 46) define the spacing between the positions that may be measured along the path of travel.
It should be noted that in some situations, the spacing between the first set 51 of sensors and the second set 53 of sensors may be set so that the encoded words 48 being read or sensed by the sensors 50 are not adjacent to each other. In such case, the spacing between the encoded words 48 utilized to define each position of the elongated shaft 22 along the path of travel 23 remains a fixed distance apart and is set by the distance between the first set 51 of sensors and the second set 53 of sensors. In other words, in the embodiment depicted in
The identity of the encoded words 48 aligned with the first set 51 of sensors and the second set 53 of sensors defines the position of elongated shaft 22 along path of travel 23 while the alignment of the encoded words with specific ones of the sensors 50 defines the position of the elongated shaft 22 along arcuate path 24. More specifically, the first set 51 of sensors and the second set 53 of sensors read or sense the status of the indicia 45 aligned therewith and which of the sensors 50 are aligned with the columns 46 of indicia 45 defining the borders. This configuration permits the controller 55 to determine the linear position of the elongated shaft and the position of elongated shaft 22 about the arcuate path 24.
In some embodiments, columns 46 of indicia 45 configured as one or more borders may be included to increase the reliability of the system 20 when determining the angular position of the elongated shaft 22. By determining which sensors 50 are aligned and interact with the columns 46 that define the borders, the amount of rotation about axis of rotation 25 may be determined and thus the angular position of elongated shaft 22. For example, referring to
As stated above, each of the indicia 45 that defines the encoded words 48 may be a multi-level logic unit configured as one of at least three states. In one example, the indicia may be magnetic elements with a “0” being configured as a “North” magnetic polarity or designation, a “1” being configured as a neutral polarity or designation, and a “2” being configured as a “South” magnetic polarity or designation. In other words, the first state generally corresponds to a first designation, the third state generally corresponds to an opposite designation, and the second state generally corresponds to a designation generally midway between the first designation and the third designation. When magnetizing each of the magnetic elements in such a configuration, all of the indicia 45 may first be magnetized as a “North” magnetic polarity. Each of the indicia 45 that are desired to be configured as a “1” or a “2” may then be magnetized with an opposite or “South” polarity which, when combined with the “North” polarity, will change each of those indicia to a neutral polarity. The indicia 45 that are desired to correspond to a “2” may then be again magnetized with an additional “South” polarity. This results in the desired three states of indicia with some of the indicia having a first polarity, other indicia having an opposite polarity, and still others having a neutral polarity or designation. When the indicia 45 are magnetized as multi-level logic units configured as one of at least three states, the sensors 50 may be analog magnetic field sensors.
Other arrays of indicia 45 may be configured to create desired patterns of encoded words 48. For example, referring to
It should be noted that in the embodiment depicted in
Although
In still another alternate embodiment,
While the moveable member is depicted as an elongated shaft 22 that is moveable in a first direction along generally linear path of travel 23 and in a second direction about arcuate path 24, the concepts disclosed herein may also be applicable to a moveable member that is moveable in two directions that are generally perpendicular or orthogonal to each other. In such case, the array of indicia 45 may be configured in a generally planar manner and the first set 51 of sensors and the second set 53 of sensors may both be in a linear array rather than in an arcuate array.
Although described above with respect to magnetic indicia 45 and sensors 50, the indicia 45 and the sensors 50 may operate through other mediums. For example, the indicia 45 and the sensors 50 may be optical rather than magnetic. In such case, the indicia 45 may be configured with different degrees of reflectivity and the sensors 50 may be optical sensors configured to determine the amount of reflection from the indicia. In one example, a “0” may be approximately one hundred percent reflective, a “1” may be approximately fifty percent reflective, and a “2” may be generally non-reflective. Additional states may be added by defining different points of reflectively between one hundred percent reflective and generally non-reflective. For example, “0” may be approximately one hundred percent reflective, “1” may be approximately sixty-six percent reflective, “2” may be approximately thirty-three percent reflective, and “4” may be generally non-reflective.
As depicted, the border is configured utilizing columns 46 of indicia 45 with a repeating pattern of states “0” and “1.” However, other or additional borders may be utilized using other combinations of states such as “0” and “2” or “1” and “2.” In addition, the borders could use multi-level logic units configured with three or more states as described above with respect to the encoded words 48. Such additional or different borders could be used to determine the rotational displacement without monitoring or sensing all of the indicia 45 within each row. In another configuration, it may be desirable to re-use or duplicate the array of encoded words but change the border within a row of indicia. This would permit the measurement of additional positions along the path of travel 23 without adding additional columns of indicia. As an example, the array of
In another configuration, system 20 (
In other embodiments for use with such a modified system 20 that includes only the first set 51 of sensors 50, the array of indicia 45 defining the encoded words 48 may be multi-level logic units configured for binary operation or with only two states. For example, the encoded words 48 of the array of
It should be noted that based upon the binary counting sequence, rows 16, 31 and 32 at least two repeating patterns of four “1's.” Such repeating pattern may reduce the reliability of the angular position sensing functionality. In such case, it may be desirable to eliminate the rows in which a repeating pattern of four “1's” would exist. In addition or in the alternative, it may be desirable to add additional columns 46 of border indicia 45 configured as “0's” on both ends of the borders. In such case, the border designation becomes “011110.” Referring to
The industrial applicability of the system 20 described herein will be readily appreciated from the foregoing discussion. The present disclosure is applicable to determining displacement of a moveable member relative to a reference member. The moveable member is configured for movement along a range of a positions in both a first direction and a second direction. The system permits the determination of the absolute position of the moveable member by monitoring or sensing the identity and location of encoded words positioned along the moveable member.
In one aspect, a system 20 for determining the displacement of a moveable member relative to a reference member is provided. The moveable member is configured for movement relative to the reference member along a range of positions in a first direction and in a second direction. A first set 51 of sensors is fixed relative to one of the reference member and moveable member. An array of encoded words 48 on another of the reference member and moveable member is provided. The encoded words 48 define the positions of the moveable member along the first direction and a position of the encoded words relative to the first set 51 of sensors defines the positions of the movable member along the second direction. Each encoded word 48 includes a plurality of indicia 45 and each indicia is a multi-level logic unit configured as one of at least two states.
In another aspect, a method is provided for determining the displacement of a moveable member relative to a reference member. The moveable member is configured for movement relative to the reference member along a range of positions in a first direction. A first set 51 of sensors is provided together with an array of encoded words 48 on the moveable member. The encoded words 48 define the positions of the moveable member along the first direction and includes a plurality of indicia 45. Each indicia 45 is a multi-level logic unit that is configured as one of at least three states. Upon moving the moveable member relative to the reference member, the indicia 45 of an encoded word 48 aligned with some of the sensors 50 are sensed. The displacement of the moveable member along the first direction is determined based upon the sensed indicia 45. The displacement of the movable member along the second direction is determined based upon the position of the sensed indicia 45.
It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated.
Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.
Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.
