POSITION SENSING

BACKGROUND

1. Field of the Invention

[0001] The subject invention relates to a system and method for high accuracy magnetic position sensing of an object, and more specifically, wherein magnetic position sensing is accomplished by measuring three vector components of a magnetic field produced by the object.

2. Description of Related Art

[0002] Magnetic position sensing technology is becoming an increasingly popular form of detection in various systems. However, conventional methods of magnetic position sensing determine position using only two vector components of a magnetic field of an object being sensed. For example, in automotive applications, such as clutch position measurement systems and transmission gear position sensing systems, conventional methods of sensing position using only two vector components of a magnetic field are inadequate for providing high-accuracy and high-precision measurements required for modern time-sensitive and position-sensitive automotive control systems. Another exemplary application is brushless DC motor control systems, where measurement of magnetic elements of rotors of brushless DC motors is required for tuning and efficient operation of the motors. Conventional methods of magnetic position sensing measure only two vector components of a magnetic field of an object being sensed and base determination of location of the object thereon. Therefore, conventional methods are not accurate and precise enough to allow for reliable operation of innovative position- sensitive control systems that are reliant on high-accuracy position determination.

SUMMARY

[0003] One embodiment of a system for determining position is provided. The system includes an object. The object is configured to produce a magnetic field having a first vector component, a second vector component, and a third vector component. The first, second, and third vector components are orthogonal to one another. A sensor is configured to measure a magnitude of each of the first, second, and third vector components when the object is within a range of positions. A controller is connected to the sensor. The controller is configured to determine a relative position of the object within an undetermined cycle of a plurality of cycles based on the magnitude of the first vector component and the magnitude of the second vector component. The controller is configured to determine a cycle of the plurality of cycles in which the object is located based on the magnitude of the third vector component. The controller is configured to determine an absolute position of the object based on the relative position of the object and the cycle in which the object is located.

[0004] One method of operating a system for determining position is provided. The system includes an object, a sensor, and a controller connected to the sensor. The object is configured to move within a range of positions. The object is further configured to provide a magnetic field having a first vector component, a second vector component, and a third vector component. The first, second, and third vector components are orthogonal to one another. The object is moved within the range of positions. The sensor measures a magnitude of each of the first, second, and third vector components when the obj ect is within the range of positions . The controller determines a relative position of the obj ect within an undetermined cycle of a plurality of cycles based on the magnitude of the first vector component and the magnitude of the second vector component. The controller determines a cycle of the plurality of cycles in which the object is located based on the magnitude of the third vector component. The controller determines an absolute position of the object based on the relative position of the object and the cycle in which the object is located.

[0005] One embodiment of an object for use in position sensing is also provided. The object has a length. The object is configured to move linearly within a range of positions. The object is configured to produce a magnetic field having a first vector component, a second vector component, and a third vector component. The first, second, and third vector components are orthogonal to one another. A magnitude of the first vector component and a magnitude of the second vector component each vary cyclically along the length of the object. The magnitude of the third vector component is unique for every position of the sensor along the length of the object.

[0006] The system, method, and object advantageously provide high accuracy determination of position of the object through three-dimensional magnetic sensing. By determining position of the object based on magnitudes of three dimensions of the magnetic field produced by the object, position of the object can be determined with extremely high accuracy and precision. This allows the system and method to be implemented within innovative position-sensitive control systems that are reliant on high- accuracy position sensing, such as transmission control modules of automated manual transmissions for automobiles, which are reliant on high-accuracy position determinations for clutches, as well as high-efficiency and high-precision brushless DC motor control systems, which are reliant on high-accuracy position determinations for magnetic rotors.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description, when considered in connection with the accompanying drawings.

[0008] Figure 1 is a perspective view of one embodiment of a system for determining position of an object using a sensor located a fixed distance from the object and a controller in communication with the sensor.

[0009] Figure 2 is a perspective view of another embodiment of the system for determining position, wherein the object includes a plurality of magnets.

[0010] Figure 3 is a layout of one embodiment of an object for use in positions sensing.

[0011] Figure 4 is a chart illustrating magnitudes of a first, a second, and a third vector component of the object acquired by the sensor according to one example.

[0012] Figure 5 is a chart illustrating the relationship of the first and second vector components to a relative position of the object and the relationship of the third vector component to a cycle within a plurality of cycles in which the object is located according to one example.

[0013] Figure 6 is a perspective view of yet another embodiment of the system for determining position, wherein the obj ect is fixed to a clutch positioning component of an automated manual transmission.

[0014] Figure 7 is a flowchart of an embodiment of a method of determining position. DETAILED DESCRIPTION

[0015] Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, aspects of a system 10 and a method 30 for sensing position of an object 12 are provided.

I. System Description

[0016] Figure 1 illustrates an embodiment of the system 10. The system 10 includes an object 12, a sensor 14, and a controller 16. The object 12 is configured to produce a magnetic field H. The magnetic field H has a first vector component VI, a second vector component V2, and a third vector component V3. The first, second, and third vector components VI, V2, V3 are orthogonal to one another.

[0017] The object 12 can have several configurations. In FIG. 1, the object 12 is substantially cylindrical and has a first end 18 and a second end 20. Each of the first, second, and third vector components VI, V2, V3 has both a direction and a magnitude. The direction of the first vector component VI extends radially from the object 12 in the direction of the sensor 14. The direction of the second vector component V2 extends longitudinally through the object 12 orthogonal to the first vector component VI . The direction of the third vector component V3 extends radially from the object 12 orthogonal to both the first and second vector components VI, V2. The object 12 can be any shape suitable to produce the magnetic field H. The object 12 may have configurations other than those specifically described herein.

[0018] In FIG. 1, the object 12 is a single magnet configured to produce the magnetic field H. In FIG. 2, the object 12 includes a plurality of magnets 26 configured to altogether produce the magnetic field H. In some embodiments, the magnets 26 are permanent magnets. In other embodiments, the magnets 26 are electromagnets.

[0019] The sensor 14 is a magnetic field sensor configured to measure the magnitudes of each of the first, second, and third vectors components V 1 , V2, V3 of the magnetic field H when the object 12 is within a range of positions 22. The magnitudes of each of the first, second, and third vector components V 1 , V2, V3 can be measured in terms of either magnetic flux density or magnetic field intensity. Although the letter 'H' is used herein to refer to the magnetic field H, referring to strength of the magnetic field H expressed in amperes per meter, the magnetic field H can also be expression in terms of the Lorentz force it exerts on moving electric charges, i.e. 'Β', or any other suitable method of expressing a field generated by magnetized material.

[0020] The range of positions 22 is defined such that as the object 12 is moved within the range of positions 22, the object 12 moves along a single axis such that the sensor 14 is located between the first end 18 and the second end 20 and the sensor 14 remains a fixed distance 24 from the object 12. The object 12 may move along the single axis via a predetermined path. In some embodiments, the range of positions 22 is shorter due to an edge effect of the magnetic field H. The edge effect affects measurement of the magnetic field H such that measuring the magnitudes of the first, second, and third vector components VI, V2, V3 near the first end 18 or the second end 20 of the object 12 is undesirable.

[0021] The sensor 14 is configured to measure the magnitude of each of the first, second, and third vector components VI, V2, V3 of the magnetic field H substantially simultaneously. The sensor 14 can be any type of sensor capable of measuring the magnitude of each of the first, second, and third vector components VI, V2, V3 of the magnetic field H, such as, but not limited to, a rotating coil, hall effect, magnetoresistive, fluxgate, superconducting quantum interference device, or spin-exchange relaxation-free atomic magnetometer. The sensor 14 may have configurations other than those specifically described herein.

[0022] The controller 16 is in communication with the sensor 14. The controller 16 performs many of the high-accuracy position determination steps of the method 40. The controller 16 receives the magnitudes of the first, second, and third vector components VI, V2, V3 of the magnetic field H from the sensor 14. The controller 16 can be a microcontroller, state machine, field-programmable gate array, CPU, or any other device suitable for receiving and analyzing the magnitudes of the first, second, and third vector components VI, V2, V3 from the sensor 14.

[0023] With reference to FIG. 4, the object 12 is configured such that the magnitude of the first vector component V 1 and the magnitude of the second vector component V2 measured by the sensor 14 as the object 12 is moved across the range of positions 22 are each periodic functions. In one embodiment, the magnitude of the first vector component VI and the magnitude of the second vector component V2 are each sinusoidal. The magnitudes of the first and second vector components VI, V2 measured at any position within the range of positions 22 have a phase difference Δ. In another embodiment, the magnitude of the first vector component VI substantially resembles a cosine wave and the magnitude of the second vector component V2 substantially resembles a sine wave.

[0024] The object 12 is configured such that the magnitude of the third vector component V3 has a unique value for each possible position of the sensor 14 relative the object 12 as the object 12 is moved across the range of positions 22. In some embodiments, the magnitude of the third vector component V3 is a monotonic function. In one example, the magnitude of the third vector component V3 continually increases as the object 12 is moved across the range of positions 22. In another example, the magnitude of the third vector component V3 continually decreases as the object 12 is moved across the range of positions.

[0025] Figure 4 is a chart illustrating the magnitudes of the first, second, and third vector components VI, V2, V3 of an exemplary embodiment of the invention. The chart has a horizontal position axis and a vertical magnetic field axis. The position axis corresponds to position of the object 12 within the range of positions 22. The left-most value on the position axis corresponds to the object 12 being located within the range of positions 22 such that the sensor 14 is nearest the first end 18 of the object 12. Increasing values of the position axis, i.e. values further toward the right of the position axis, correspond to the object 12 being located such that the sensor 14 is nearer the second end 20 of the object 12. The right-most value on the position axis corresponds to the object 12 being located within the range of positions 22 such that the sensor 14 is nearest the second end 20 of the object 12.

[0026] The magnetic field axis corresponds to the magnitudes of the first, second, and third vector components VI, V2, V3 measured by the sensor 14 and communicated to the controller 16 at each position along the horizontal axis. In FIG.4, the magnitudes of the first and second vector components VI, V2 are sinusoidal and the phase difference Δ is about π/2 radians, i.e. 90 degrees. The magnitudes of the first and second vector components VI,

V2 are periodic functions related to the position of the object 12 within the range of positions 22. The magnitude of the third vector component V3 is a monotonic function related to the position of the object 12 within the range of positions 22. In FIG. 4, the magnitude of the third vector component V3 continually increases as the object 12 is moved across the range of positions 22 such that the sensor 14 measures the magnitude of the third vector component V3 from near the first end 18 of the obj ect 12 to near the second end 20 of the object 12.

[0027] With continued reference to FIG. 4, position of the object 12 over each period of the magnitudes of each of the first and second vector components V 1 , V2 defines each cycle of a plurality of cycles 28a, 28b, 28c, 28d, 28e. In the embodiment of the invention illustrated in FIG. 4, the plurality of cycles 28a, 28b, 28c, 28d, 28e includes five cycles. The number of cycles is dependent upon the magnetic field H, and is thereby dependent upon configuration of the obj ect 12. It should be appreciated that the obj ect 12 can be configured in many ways, and the plurality of cycles 28a, 28b, 28c, 28d, 28e can include any amount of cycles.

[0028] Figure 3 illustrates one embodiment of the object 12 including the plurality of magnets 26. The number of cycles included in the plurality of cycles 28a, 28b, 28c, 28d, 28e is dependent upon the number of magnetic included in the plurality of magnets 26. In FIG. 3, the plurality of magnets 26 includes five magnets, thereby causing the plurality of cycles 28a, 28b, 28c, 28d, 28e to include two cycles. The edge effect prevents the plurality of cycles 28a, 28b, 28c, 28d, 28e from including more than two cycles, as the sensor 14 in unable to reliably measure the magnetic field H near the first and second ends 18, 20 of the object 12.

[0029] With continued reference to FIG. 3, the magnets 26 each have a north pole N and a south pole S. The magnets 26 are oriented such that the north and south poles N, S that are adjacent to one another have opposing polarities, i.e. each of the north poles N is adjacent only to one or more of the south poles S, and each of the south poles S is adjacent only to one or more of the north poles N. The opposing polarities of the north and south poles N, S cause the magnitudes of the first and second vector components VI, V2 to be sinusoidal with respect to position of the object 12 within the range of positions 22 as shown in FIG.4.

[0030] The controller 16 is configured to determine a relative position of the object 12 within an undetermined cycle of the plurality of cycles 28a, 28b, 28c, 28d, 28e based upon the magnitudes of the first and second vector components V 1 , V2. The relative position of the object 12 is a position of the object 12 determined within an undetermined cycle of the plurality of cycles 28a, 28b, 28c, 28d, 28e. For example, when the plurality of cycles 28a, 28b, 28c, 28d, 28e includes five cycles, the controller 16 determines precisely where the object 12 is located within one cycle of the five cycles, but within which cycle of the five cycles the object 12 is located is undetermined. In other words, although the controller 16 may accurately determine the relative position of the object 12 within any given single cycle, the controller 16 cannot determine which cycle of the plurality is being measured based upon the magnitudes of the first and second vector components V 1 , V2.

[0031] Accordingly, the controller 16 is configured to determine in which cycle of the plurality of cycles 28a, 28b, 28c, 28d, 28e the object 12 is located based on the magnitude of the third vector component V3. The controller 16 determines the cycle in which the object 12 is located by corresponding the magnitude of the third vector component V3 with the cycle in which the object 12 is located. The techniques by which the controller determines the cycle in which the object 12 is located are described in detail below.

[0032] Referring now to FIG. 6, in some embodiments, a secondary obj ect 30 is fixed to the object 12. The secondary object 30 is fixed to the object 12 such that the secondary object 30 has constant position relative the object 12 as the object 12 is moved within the range of positions 22. For example, in FIG. 6, the secondary object 30 is fixed to the object 12 such that the secondary object 30 is located directly below the object 12. As the object 12 is moved within the range of positions 22, the secondary object 30 will continue to be located directly below the object 12. The secondary object 30 can be fixed to the object 12 and located relative the object 12 in ways other than those specifically described herein. The controller 16 is programmed with location and of the secondary object 30 relative the object 12. As the controller 16 determines location of the object 12, the controller can also determine location of the secondary obj ect 30 based on location of the secondary obj ect 30 relative the obj ect 12.

[0033] With continued reference to FIG. 6, an exemplary embodiment including a clutch actuation component 30 for an automobile, commonly a truck, having an automated manual transmission is shown. The automated manual transmission allows an automobile transmission having a manual transmission gearbox to change gears without manual operation of a clutch pedal by a human operator. The automobile transmission changes gears with automated clutch actuation by a transmission control module. The transmission control module is a closed-loop control system. In some embodiments, the controller 16 includes the transmission control module.

[0034] The clutch actuation component 30 is fixed to a clutch positioning rod 32. The clutch positioning rod 32 is actuated according to signals from the transmission control module to control position of an automotive clutch during automated shifting operations of the automated manual transmission.

[0035] The transmission control module requires high-accuracy knowledge of position of the automotive clutch to facilitate smooth operation of the vehicle during gear shifting. The object 12 is fixed to and extends along a length of the clutch actuation component 30. The object 12 is moved within the range of positions 22 as the clutch positioning rod is actuated. The controller 16 communicates position of the object 12 to the transmission control module. The transmission control module infers position of the automotive clutch by knowledge of fixed distances between the object 12, the clutch actuation component 30, and the automotive clutch.

II. Method Description

[0036] Figure 7 is a flowchart illustrating detailed operation of the method 40 for determining high-accuracy position of the object 12. As described, the method 40 occurs while the object 12 is within the range of positions 22.

[0037] At step 200, the object 12 is moved to within the range of positions 22. The object 12 can be moved to within the range of positions 22 from a position within the range of positions 22 or can be moved to within the range of positions 22 from a position outside the range of positions 22.

[0038] At step 202, the sensor 14 measures a magnitude of each of the first, second, and third vector components VI, V2, V3.

[0039] At step 204, the controller 16 determines the relative position of the object 12 within the undetermined cycle of the plurality of cycles 28a, 28b, 28c, 28d, 28e. The relative position is expressed as a position parameter. In one embodiment, the controller

16 does so by determining a position parameter having a tangent equal to a quotient of both the magnitude of the first vector component VI and the magnitude of the second vector component V2. The position parameter is a value between -nil radians and nil radians, i.e. -90 degrees and 90 degrees.

[0040] FIG. 5 is a chart having a horizontal position axis, a vertical magnetic field axis, and a vertical angle axis. The position axis corresponds to position of the object 12 within the range of positions 22. The left-most value on the position axis corresponds to the object 12 being located within the range of positions 22 such that the sensor 14 is nearest the first end 18 of the object 12. Increasing values of the position axis, i.e. moving toward the right of the position axis, corresponds to the object 12 being located within the range of positions 22 such that the sensor 14 is nearer the second end 20 of the obj ect 12, wherein the right-most value on the position axis corresponds to the object 12 being located within the range of positions 22 such that the sensor 14 is nearest the second end 20 of the object 12.

[0041] The magnetic field axis corresponds to the magnitude of the third vector component V3 measured by the sensor 14 and communicated to the controller 16 at each position along the position axis. In FIG. 5, the magnitude of the third vector component V3 continually increases as the object 12 is moved across the range of positions 22 such that the sensor 14 measures the magnitude of the third vector component V3 from near the first end 18 of the object 12 to near the second end 20 of the object 12.

[0042] The angle axis corresponds to the value of the position parameter calculated at step 204 by the controller 16 for each position of the object 12 along the position axis. The value of the position parameter is a periodic function having the same period as the sinusoids of the magnitudes of the first and second vector components VI, V2 due to the position parameter being a function of the magnitudes of the first and second vector components V 1 , V2. Therefore, each period of the value of the position parameter corresponds to a cycle of the plurality of cycles 28a, 28b, 28c, 28d, 28e. The undetermined cycle of the plurality of cycles 28a, 28b, 28c, 28d, 28e is undetermined due to the position parameter having an identical value Θ1, Θ2 within each cycle of the plurality of cycles 28a, 28b, 28c, 28d, 28e. Therefore, determination of the position parameter allows for high-accuracy determination of the relative position of the object 12 within the undetermined cycle of the plurality of cycles 28a, 28b, 28c, 28d, 28e.

[0043] In some embodiments, the controller 16 determines the relative position by retrieving the position parameter from a position parameter lookup table. The position parameter lookup table is a section of memory accessible by the controller 16 having recorded values of the position value corresponding to the magnitudes of the first and second vector components V 1 , V2. In other embodiments, the controller 16 determined the relative position by calculating the position parameter as a function of the magnitudes of the first and second vector components VI, V2. Retrieving the position parameter from the position parameter lookup table is advantageous in situations where the controller 16 has limited processing power. Calculating the position parameter as a function of the magnitudes of the first and second vector components V 1 , V2 is advantageous in situations where the controller 16 has limited memory.

[0044] At step 206, the controller 16 determines the cycle in which the object 12 is located. With continued reference to FIG. 5, the magnitude of the third vector component V3 is unique for each position of the object 12 within the range of positions 22 due to the magnitude of the third vector component V3 being a monotonic function of the position of the object 12 within the range of positions 22. Therefore, each cycle of the plurality of cycles 28a, 28b, 28c, 28d, 28e has a corresponding range of magnitudes of the third vector component V3 that correspond thereto. In FIG. 5, the plurality of cycles 28a, 28b, 28c, 28d, 28e includes 2.5 cycles. The magnitude of the third vector component V3 has a distinct range of magnitudes corresponding to each cycle of the plurality of cycles 28a, 28b, 28c, 28d, 28e. In some embodiments, the controller 16 determines the cycle in which the object 12 is located by retrieving from a cycle lookup table the cycle corresponding to the magnitude of the third vector component V3. In other embodiments, the controller 16 determines the cycle in which the object 12 is located by calculating the cycle in which the object 12 is located as a function of the magnitude of the third vector component V3.

[0045] FIG. 5 illustrates an exemplary position P 1 , a first exemplary position parameter Θ 1 , a second exemplary position parameter Θ2, and an exemplary third vector component HP 1. The exemplary position PI is within a first cycle 28a. The first and second exemplary position parameters Θ1, Θ2 are determined when the object 12 is located at the exemplary position PI . The first exemplary position parameter Θ1 is within the first cycle 28a. The second exemplary position parameter Θ2 has value equal to the first exemplary position parameter Θ 1 and is within a second cycle 28b . The exemplary third vector component HP 1 is the magnitude of the third vector component V3 measured when the obj ect 12 is located at the exemplary position PI .

[0046] At step 208, the controller 16 calculates an absolute position of the object 12 based on the relative position and the cycle. The absolute position of the object 12 is a high- accuracy determination of position of the object 12 within the cycle of the plurality of cycles 28a, 28b, 28c, 28d, 28e within which the object 12 is located. The controller 16 determines the absolute position of the object 12 by combining the determination of the relative position of the object 12 at step 204 with the determination of the cycle in which controller

16 determined the object 12 is located at step 206. [0047] The present invention has been described herein in an illustrative manner. It is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Obviously, many modifications and variations of the invention are possible in light of the above teachings. The invention may be practiced otherwise than as specifically described within the scope of the appended claims.