Patent Application
20230194311
This invention relates generally to a position sensing system for an actuator with error detection and correction.
Conventional technologies for position sensing in actuators (particularly linear actuators) often use a contact-based potentiometer or position sensing. This method was generally accurate as the potentiometer provided a repeatable position signal which was mechanically linked to actuator travel. The downside of this conventional technology is that the contact based potentiometer was subject to contact wear over time and/or mechanical failures.
More recently, non-contact methods have been developed which use non-contact sensing technology, such as Hall-effect sensors. In such an arrangement, for example, a rotating magnet located on an actuator shaft of the actuator is used in combination with a Hall-effect sensor. The Hall-effect sensor counts pulses during the rotation of the actuator shaft in order to determine a distance traveled. This method is useful to calculate distance traveled, however, it is not always sufficient (by itself) to determine the latest position of the actuator shaft without a known point of reference.
In theory, it is possible to deduce the position of the actuator shaft if the starting point of the actuator shaft is known when the actuator was constructed. In practice, however, the actuator accumulates some amount of position error over time with no means of self-detection and/or correction.
To mitigate this problem, some actuators have more recently integrated a means to self-check the position of the actuator shaft by automatically and periodically moving the actuator shaft to a known reference point (or points) and checking the position of the actuator shaft. To correct for error and reorient the position of the actuator shaft, such autocorrecting actuators may (i) move the actuator shaft to a minimum extent and/or a maximum extent, or (ii) move the actuator shaft past a single in-path reference point. These methods can be effective, but have a few shortcomings. For some applications, traveling to both extents of the actuator is not possible or impractical. For example, the actuator may have more stroke than its associated linkage can allow, so actuator motion would be limited by the bounds of the linkage to which it is attached.
The single in-path reference is a viable solution to the previously mentioned stroke limitation problem for some actuators, however, the single in-path reference solution typically requires a dedicated effort to drive the actuator past this point to reorientation, and such a solution can be inconvenient, impractical or troublesome for many applications. Referring to the example of a car, the single in-path reference solution would be like returning home to reorient your position in the middle of a long journey with lots of stops, which would be impractical.
In keeping with the car analogy, what is proposed herein are mile posts along the highway, whereby each mile post is a unique identifier along the journey. Using the mile posts in combination with an odometer (e.g., non-contact travel sensor) provides a means of repetitious checking and correction of position at any point along the journey, and without need for a specific return to home or travel to both ends of the highway.
Thus, what is sought is a position sensing system for an actuator that does not suffer from the disadvantages described above.
In one exemplary aspect, an actuator position sensing system for sensing a position of an actuator, said actuator position sensing system comprising: a first sensor for detecting a position of a first moveable portion of the actuator; a plurality of second sensors each being configured for detecting a position of a second moveable portion of the actuator; and a controller connected to the first sensor and the plurality of second sensors, said controller being configured to determine a position of the second movable portion based upon data transmitted from the first sensor and one or more of the plurality of second sensors. The actuator may be a linear actuator.
The controller is configured to calculate a difference between (i) a position of the second movable portion as calculated based upon the data transmitted from the first sensor, and (ii) a position of the second movable portion as calculated based upon the data transmitted from said one or more of the plurality of second sensors.
A motor is connected to the first movable portion that is configured to move the first moveable portion based upon a difference, which is calculated by the controller, between (i) a position of the second movable portion as calculated based upon the data transmitted from the first sensor, and (ii) a position of the second movable portion as calculated based upon the data transmitted from said one or more of the plurality of second sensors.
The first movable portion and the second movable portion are connected together such that movement of the first moveable portion causes movement of the second movable portion.
The first movable portion and the second movable portion are connected together such that rotation of the first moveable portion causes translation of the second movable portion.
The first movable portion and the second movable portion are connected together such that rotation of the first moveable portion causes translation, but not rotation, of the second movable portion.
The first movable portion is a fastener having male threads and the second movable portion is a rod having female threads, and the male threads are engaged with the female threads.
One or more magnets are mounted to the first movable portion, wherein the first sensor is configured to sense a rotational position of the first movable portion based upon a magnetic field generated by the one or more magnets mounted to the first movable portion. The first sensor may be a Hall-Effect sensor.
One or more magnets are mounted to the second movable portion, wherein the plurality of second sensors are each configured to sense a translational position of the second movable portion based upon a magnetic field generated by the one or more magnets mounted to the second movable portion. Each of the plurality of second sensors may be a Hall-Effect sensor.
A component of a combine harvester is mounted to the second movable portion of the actuator, wherein said component of the combine harvester is, for example, a concave of the combine harvester, a louver of a sieve of the combine harvester, or a linkage in the sieve of the combine harvester.
In another exemplary aspect, a method of sensing a position of an actuator, comprises:
detecting, by a first sensor, a position of a first moveable portion of the actuator;
detecting, by a plurality of second sensors, a position of a second moveable portion of the actuator; and
determining, by a controller connected to the first sensor and the plurality of second sensors, a position of the second movable portion based upon data transmitted from the first sensor and one or more of the plurality of second sensors.
The method further includes calculating a difference, by the controller, between (i) a position of the second movable portion as calculated based upon the data transmitted from the first sensor, and (ii) a position of the second movable portion as calculated based upon the data transmitted from said one or more of the plurality of second sensors.
The method further includes activating a motor connected to the first movable portion to move the first moveable portion, which moves the second movable portion, based upon the calculated difference.
The method further includes sensing a rotational position of the first movable portion using the first sensor based upon a magnetic field generated by one or more magnets mounted to the first movable portion.
The method further includes sensing a translational position of the second movable portion using one or more of the plurality of second sensors based upon a magnetic field generated by one or more magnets mounted to the second movable portion.
The method further includes moving a component of a combine harvester that is mounted to the second movable portion of the actuator, wherein said component of the combine harvester is a concave of the combine harvester, a louver of a sieve of the combine harvester, or a linkage in the sieve of the combine harvester.
Embodiments of inventions will now be described, strictly by way of example, with reference to the accompanying drawings, in which:
Exemplary embodiments of the present invention provide a system and method for sensing a position of an actuator.
Actuator 102 may be a linear actuator having a fastener or screw 120 and an actuator rod 122. Screw 120 may be referred to herein as a “first moveable portion” of the actuator, while rod 122 may be referred to herein as a “second moveable portion” of the actuator 102. Movement of the first and second moveable portions of the actuator 102 is different, i.e., first moveable portion rotates without translation, whereas second moveable portion translates with rotation.
Screw 120 includes a threaded segment 124 extending from a cylindrical (or otherwise shaped) head portion 126. A series of magnets 128 are disposed (either uniformly or non-uniformly) about the perimeter of the cylindrical head portion 126. The male threaded segment 124 of the screw 120 is meshed with female threads disposed in a blind hole 130 that is formed in the rod 122. The open end of the blind hole 130 is formed in a cylindrical (or otherwise shaped) flange 132 on the rod 122. One (or more) magnets 134 are disposed (either uniformly or non-uniformly) about the perimeter of the flange 132. Rod 122 is not limited to any particular shape or size, and may be referred to as a shaft, sleeve or nut.
The screw 120 is configured to rotate about axis A, but not translate along axis A, whereas, the rod 122 is configured to translate along axis A, but not rotate about axis A, in response to rotation of the screw 120. Screw 120 and rod 122 are supported by means (not shown) enabling the aforementioned movement. The means 112 for driving (i.e., rotating) the screw 120 of the actuator 102 may be a motor, a solenoid, an electric motor, or a hydraulic motor, for example. Means 112 may be connected to a motor by a gear, a hydraulic line, or a belt, for example. The motor may be a motor of a combine harvester, for example.
It should be understood that the actuator 102 is not limited to the linear actuator which is shown and described herein. For example, the actuator 102 could be a rotary actuator (which may or may not rotate less than 360 degrees). In sum, the actuator 102 requires a first moving portion (e.g., screw 120), the movement of which imparts movement to a second moving part (e.g., rod 122).
First sensor 106 may be a Hall-effect sensor, a rotary encoder, or an optical sensor, for example. The first sensor 106 is preferably a non-contact sensor (i.e., no contact with actuator 102), but could also be a contact sensor, such as a potentiometer. Other means for detecting the movement (e.g., rotation) of a component are known. First sensor 106 may be described herein as a “first sensor means” or “first means for sensing.”
First sensor 106 is configured for sensing the rotational position of the screw 120 of the actuator 102. Specifically, the sensor 106 senses the rotational position by detecting the presence (and/or absence) of the magnetic field of the individual magnets 128 on the head 126 of the screw 120, and transmits a signal to the controller 110. Accordingly, sensor 106 is aligned with head 126 along a plane or axis that is transverse to axis of rotation A. The above described process of Hall-effect sensing is known to those skilled in the art. Based upon the signals received from the first sensor 106, a processor of the controller 110 is configured to determine the rotational position of the screw 120. And, based upon the rotational position of the screw 120, the controller 110 is configured to determine the translational position of the rod 122. It should be understood that rotation of the screw 120 by a pre-determined amount results in translation of the rod 122 by a pre-determined amount. The pre-determined amount of translation is a function of the thread pitch of the screw 120 and the threaded hole 130, as is known in the art.
As is noted in the Background section, despite the ability of the first sensor 106 to detect rotation of the screw 120 and the ability of the controller to calculate translation of the rod 122 as a function of rotation of the screw 120, the actuator 102 will accumulate some amount of positional error over time with no means of self-detection. Thus, it would be desirable to verify the position of the actuator 102 (e.g., the translation position of the rod 122 of the actuator 102) by an alternative measurement mechanism.
In view of the foregoing desire, the second sensors 108 are configured for sensing the translational position of the flange 132 of the rod 122 of the actuator 102. Notably, the second sensors 108 are configured for sensing the translational position of the flange 132 of the rod 122 in both translational directions (i.e., forward and backward) of rod 112. Specifically, the second sensors 108 each sense the presence (or absence) of the magnetic field of the magnet 134 on the flange 132 of the rod 122, and transmits a signal to the controller 110. Magnet 134 may be positioned at another location on rod 122. Hall-effect sensing is known to those skilled in the art. Based upon the signals received from the second sensors 108, the processor of the controller 110 is configured to determine the translational position of the rod 122. Second sensors 108a and 108d may be positioned at the extents or “end-stops” of travel of the rod 122, and second sensors 108b and 108c are positioned between those end-stops. Accordingly, second sensors 108b and 108c are positioned at locations where the rod 122 most often travels.
Each of the second sensors 108 may be a Hall-effect sensor, as described above, a rotary encoder, or an optical sensor, for example. The second sensor 108 is preferably a non-contact sensor, but could also be a contact sensor, such as a potentiometer. Other means for detecting the movement (e.g., translation) of a component are known. Second sensor 108 may be described herein as a “second sensor means” or “second means for sensing.”
Sensors 106 and 108 are fixed to a stationary component, and may not be capable of moving with respect to actuator 102. Sensors 106 and 108 are (optionally) aligned along a straight and linear path. Sensors 108a-108d may be spaced apart by a distance that is either uniform (i.e., equal) or non-uniform.
The controller 110 is connected to the sensors 106 and 108 and the control means 112, as depicted in
The actuator 102 may be connected to a moveable component on a combine harvester, for example. The moveable component could be a header (or a component of a header) of the combine harvester. Further details of a combine harvester are disclosed in U.S. Pat. Nos. 7,487,024 and 6,119,531, which are each incorporated by reference herein in their entirety and for all purposes.
More particularly, the end 138 of the rod 122, which is opposite the flange 132, is connected to a component 140 to be moved. By way of non-limiting example, the component 140 to be moved may be a concave of a combine harvester, in which case the actuator 102 represents a concave adjustment actuator that sets the distance between the concave and the rotor of the harvester. Such a concave adjustment actuator is described in U.S. Pat. No. 7,452,267, which is incorporated by reference herein in its entirety. Alternatively, the component 140 may be a louver (or louvers) of a sieve of a harvester, in which case the actuator 102 is a louver actuator that is configured to adjust the rotational position of the louver(s) of a sieve for adjusting the size of the opening in the sieve in order to permit a pre-determined grain size to pass through the opening in the sieve that is controlled by the rotational position of the louvers. Such a louver actuator is described in U.S. Pat. No. 5,041,059, which is incorporated by reference herein in its entirety. As another alternative, the component 140 may be a linkage in a sieve of a harvester, in which case the actuator 102 is configured to adjust the degree of side shake experienced by a sieve. Such a linkage is described in U.S. Patent App. Pub. No. 2019-0357441, which is incorporated by reference herein in its entirety. It should be understood that the component to be moved may be any component requiring precise position control, and is not limited to being a component of a combine harvester.
The system 300 generally comprises a hydraulic actuator 302 including a pump motor 320 (i.e., the first moveable portion) that is fluidly connected to a cylinder 360 by way of two fluid lines 362a and 362b that are fluidly connected to opposite sides of a flange 332 of a piston 322 (i.e., the second movable portion) that is movably positioned within the cylinder 360. The pump motor 320 is configured for moving the piston 322 within the cylinder 360 in two different directions depending upon the direction of rotation of the pump motor 320. It should be understood that fluid cannot move across the flange 332. The above-described component 140 to be moved is connected to the piston 322, for the applications described above. Component 140 may represent a steering cylinder of a combine harvester, for example.
The system 300 further includes a first sensor 306 for detecting movement of the first moveable portion of the actuator 302, namely, the pump motor 320. The system 300 further includes a grouping of second sensors 308a-308d (referred to either individually or collectively as second sensor(s) 308) for detecting movement of a second moveable portion of the actuator 302, namely, the piston 322. The controller 310 is generally configured to receive inputs from each of the sensors 306 and 308, determine whether actuator 302 is in its intended position, and (optionally) control pump motor 320 based upon the inputs received from the sensors 306 and 308 to correct the position of the actuator 302.
First sensor 306 is configured for sensing the rotational position of the pump motor 320 of the actuator 302. Specifically, the sensor 306 senses the rotational position by detecting the presence (and/or absence) of a magnetic field of a rotating magnet (for example) in or on the pump motor 320, and transmits a corresponding signal to the controller 310. Based upon the signals received from the first sensor 306, a processor of the controller 310 is configured to determine the rotational position of the pump motor 320. And, based upon the rotational position of the pump motor 320, the controller 310 is configured to determine the translational position (i.e., displacement) of the piston 322 based upon basic fluid theory and using a table or look up function. It should be understood that rotation of the pump motor 320 by a pre-determined amount results in translation of the piston 322 by a pre-determined amount.
As is noted in the Background section, despite the ability of the first sensor 306 to detect rotation of the pump motor 320 and the ability of the controller to calculate translation of the piston 322 as a function of rotation of the pump motor 320, the actuator 302 will accumulate some amount of positional error over time with no means of self-detection. Thus, it would be desirable to verify the position of the actuator 302 (e.g., the translation position of the piston 322 of the actuator 302) by an alternative measurement mechanism.
In view of the foregoing desire, the second sensors 308 are configured for sensing the translational position of the flange 332 of the piston 322 of the actuator 302. Specifically, the second sensors 308 each sense the presence (or absence) of the magnetic field of the magnet 334 on the flange 332 of the piston 322, and transmit a signal to the controller 310. Based upon the signals received from the second sensors 308, the processor of the controller 310 is configured to determine the translational position of the piston 322.
The controller 310 includes a conventional processor that is configured to determine whether actuator 302 is maintained in its intended position, as determined by the second sensors 308, and (optionally) actuate the pump motor 320 based upon the inputs received from the sensors 306 and 308 to move the position of the piston 322 of the actuator 302 to its intended position. The steps described in
The system 400 generally comprises an actuator 402 including a worm screw 420 (i.e., the first moveable portion) that is meshed with a spur gear 422 (i.e., the second moveable portion) such that rotation of worm screw 420 about its axis causes rotation of spur gear 422 about its respective axis. The above-described component 140 to be moved is connected to the spur gear 422, for the reasons and applications described above. A motor 412 is configured for rotating worm screw 420 about its axis, which in turn rotates the spur gear 422, which in turn rotates the component 140. Spur gear 422 can be rotated in two different directions depending upon the direction of rotation of the motor 412. Motor 412 may be electrically or hydraulically operated, for example.
The system 400 further includes a first sensor 406 for detecting movement of the first moveable portion of the actuator 402, namely, the worm screw 420. The system 400 further includes a grouping of second sensors 408a-408d (referred to either individually or collectively as second sensor(s) 408) for detecting movement of a second moveable portion of the actuator 402, namely, the spur gear 422. The controller 410 is generally configured to receive inputs from each of the sensors 406 and 408, determine whether actuator 402 is in its intended position, and (optionally) control motor 412 based upon the inputs received from the sensors 406 and 408 to correct the position of the actuator 402.
First sensor 406 is configured for detecting the presence (and/or absence) of the magnetic field of one or more magnet 428 that are disposed on a rotating flange 426 of the worm screw 420, and transmits a corresponding signal to the controller 410. Flange 426 is non-rotatably connected to worm screw 420. Based upon the signals received from the first sensor 406, a processor of the controller 410 is configured to determine the rotational position of the worm screw 420. And, based upon the rotational position of the worm screw 420, the controller 410 is configured to determine the rotational position of the spur gear 422 by applying basic gear theory and using a table or look up function.
As is noted in the Background section, despite the ability of the first sensor 406 to detect rotation of the worm screw 420 and the ability of the controller to calculate the rotational position of the spur gear 422 as a function of rotation of the worm screw 420, the actuator 402 will accumulate some amount of positional error over time with no means of self-detection. Thus, it would be desirable to verify the position of the actuator 402 (e.g., the rotational position of the spur gear 422 of the actuator 402) by an alternative measurement mechanism.
In view of the foregoing desire, the second sensors 408 are configured for sensing the presence (or absence) of a magnet 434 that is fixed to the side of the spur gear 422. It should be understood that the magnet 434 is spatially offset from the gear teeth and does not interfere with the gear teeth. Specifically, the second sensors 408 each sense the presence (or absence) of the magnetic field of the magnet 434 on the spur gear 422, and transmit a signal to the controller 410. Based upon the signals received from the second sensors 408, the processor of the controller 410 is configured to determine the rotational position of the spur gear 422.
The controller 410 includes a conventional processor that is configured to determine whether actuator 402 is maintained in its intended position, as determined by the second sensors 408. The controller 410 is also (optionally) configured to actuate the motor 412 to adjust the worm screw 420 based upon the inputs received from the sensors 406 and 408 to move the position of the spur gear 422 of the actuator 402 to its intended position. The steps described in
It is noted that system may be applicable to arrangements where worm gear rotation is less than or equal to 360 degrees, but could be useful for applications requiring multi-turn rotation. Modifications to the system 400 are envisioned. For example, the sensors 408 may track rotation of spur gear 422, and sensor 406 may track rotation of worm screw 420.
It is to be understood that the operational steps are performed by the controller 110 upon loading and executing software code or instructions which are tangibly stored on a tangible computer readable medium, such as on a magnetic medium, e.g., a computer hard drive, an optical medium, e.g., an optical disc, solid-state memory, e.g., flash memory, or other storage media known in the art. Thus, any of the functionality performed by the controller described herein is implemented in software code or instructions which are tangibly stored on a tangible computer readable medium. Upon loading and executing such software code or instructions by the controller, the controller may perform any of the functionality of the controller described herein, including any steps of the methods described herein.
The term “software code” or “code” used herein refers to any instructions or set of instructions that influence the operation of a computer or controller. They may exist in a computer-executable form, such as machine code, which is the set of instructions and data directly executed by a computer's central processing unit or by a controller, a human-understandable form, such as source code, which may be compiled in order to be executed by a computer's central processing unit or by a controller, or an intermediate form, such as object code, which is produced by a compiler. As used herein, the term “software code” or “code” also includes any human-understandable computer instructions or set of instructions, e.g., a script, that may be executed on the fly with the aid of an interpreter executed by a computer's central processing unit or by a controller.
It will be understood that changes in the details, materials, steps, and arrangements of parts which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles and scope of the invention. The foregoing description illustrates the preferred embodiments of the invention; however, concepts, as based upon the description, may be employed in other embodiments without departing from the scope of the invention. Accordingly, the following claims are intended to protect the invention broadly as well as in the specific form shown.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2021/023088 | 3/19/2021 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 62992220 | Mar 2020 | US |
