Apparatus and method for magnetically sensing the position of a rotating device
The apparatus and method using a ring magnet with varying pole pairs and a digital circuit enhance angular position sensing, addressing accuracy issues in magnetic sensors for rotating devices, enabling precise control in automotive and industrial applications.
Patent Information
- Application Number
- JP2025538582
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-12-31
- Filing Date
- 2023-10-17
- Publication Date
- 2026-01-14
AI Technical Summary
Existing magnetic sensors face challenges in providing accurate and unambiguous angular measurements for rotating objects, particularly in automotive and industrial applications, where precise rotational angle sensing is required.
An apparatus and method utilizing a ring magnet with multiple magnetic pole pairs of varying sizes and a magnetic polarity-sensitive sensor to generate distinct analog signals, which are processed by a digital circuit to distinguish between different pole pairs and determine the rotational position of a rotating device.
Enables accurate and repeatable detection of rotational positions, providing identifiable home and stop points, enhancing control and positioning accuracy in systems like BLDC motors and fluid control valves.
Smart Images
Figure 2026501390000001_ABST
Abstract
Description
[Technical Field]
[0001]
[0001] This disclosure is generally directed to magnetic sensors. More particularly, this disclosure relates to an apparatus and method for magnetically sensing the position of a rotating device. [Background technology]
[0002]
[0002] Various sensors are known in the magnetic effect sensing technology. Examples of common magnetic effect sensors include magnetoresistive and Hall effect technologies. Such magnetic sensors can generally respond to changes in a magnetic field, which is affected by the presence or absence of a ferromagnetic object of a designed shape passing through the sensing area of the magnetic effect sensor. The sensor can then provide an electrical output, which can be further modified as needed by subsequent electronics to obtain sensing and control information. Angular position sensors have applications in many fields, such as automotive and industrial technology. For example, in automotive applications, angular position sensors are used to detect the position of a rotor in a brushless direct current (BLDC) motor during operation, or in steering angle measurement to provide information about the direction a driver wants to travel for automatic steering applications (e.g., electric power steering). Angular position sensors also find application in thermal management systems, where they can control valves and the flow of cooling and heating fluids through the system. In automotive and industrial technology, magnetic concepts prevail as cost-effective and robust systems. Typically, these comprise pivoted magnetic transmitters that interact with stationary sensors that detect magnetic fields. In some applications, unambiguous angular measurement of one full rotation of a rotating object may be required. Providing accurate measurements for such applications is not straightforward, and therefore, there is a need for improved methods and apparatus for magnetically sensing the rotational angle or position of a rotating object. Summary of the Invention
[0003]
[0003] The present disclosure relates to an apparatus and method for magnetically sensing the position of a rotating device.
[0004] In a first aspect, an apparatus for use in magnetic sensing applications is disclosed. The apparatus includes a magnetic polarity-sensitive sensor and a ring magnet associated with the sensor. The ring magnet includes multiple magnetic pole pairs of opposite polarity, at least one pole pair being larger than at least three other pole pairs. The sensor detects each period of an analog signal generated by the magnetic polarity of each pole pair and couples the generated analog signal to a digital circuit to distinguish the three smaller pole pairs from at least one larger pole pair.
[0004]
[0005] In a second aspect, a method for determining the position of a ring magnet affixed to a rotating device is disclosed. The method includes positioning the ring magnet proximate a magnetic polarity-sensitive sensor. The ring magnet has multiple magnetic pole pairs of opposite magnetic polarity, such that at least one pole pair is larger than at least three other pole pairs. The method further includes generating an output signal for each pole pair, the output signal corresponding to a period during which the sensor detects the magnetic polarity of the pole pair as the ring magnet is rotated by the device. The method also includes coupling the output signal to a digital circuit that distinguishes three smaller pole pairs from at least one larger pole pair to determine the position of the ring magnet.
[0005]
[0006] Other technical features may be readily apparent to those skilled in the art from the following figures, descriptions, and claims.
[0007] For a more complete understanding of the present disclosure, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: [Brief explanation of the drawings]
[0006] [Figure 1]
[0008] FIG. 1 illustrates an example apparatus of the present disclosure. [Figure 2]
[0009] 1 illustrates an example ring magnet that may be used in the present disclosure. [Figure 3]
[0010] FIG. 10 illustrates an example graph showing the relationship between pole pair segments and magnetic analog signals for a ring magnet of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION
[0007]
[0011] The figures discussed below and the various embodiments used to explain the principles of the present invention in this patent document are merely exemplary and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that the principles of the present invention may be implemented in any type of suitably arranged device or system.
[0008]
[0012] FIG. 1 shows a diagram of an exemplary apparatus for detecting the position of a rotating device according to the present disclosure. The apparatus may be used to detect the rotational position of a rotating device, such as, for example, a motor shaft extending from an electric motor. The present disclosure may also be used to sense the rotation and position of other rotary drives, such as, for example, a steering column core and a motor driving a window lift used in a vehicle or a geared actuator valve used in a fluid or pneumatic system. The apparatus of the present disclosure provides a unique N-S pattern that creates an identifiable home position and other repeatable, identifiable positions as the ring magnet is rotated. The arrangement of the ring magnet generates a specific magnetic wave pattern during rotation whose position is uniquely identifiable and repeatable.
[0009]
[0013] The example apparatus 100 comprises a control system, which may include a controller 105, and a motor driver circuit 110. The control system is communicatively coupled to an electric motor 120 via the motor driver circuit 110. The controller may receive instructions from a central controller (not shown) via a communication bus 106 to the controller 105 to cause the controller to activate and drive the electric motor 120. Control signals from the controller 105 are sent to the motor driver circuit 110, which excites and drives the electric motor 120 to a commanded rotational position. When energized, the electric motor 120 rotates a core or shaft 115 attached to the electric motor 120.
[0010]
[0014] The position detection device consists of a multi-pole ring magnet 200 and a fixed position sensor 210 used to detect the rotational position of the core 115. The ring magnet 200 is rotationally fixed to the core 115 and rotates about a central axis A. The ring magnet 200 is rotated by the core 115 when the motor 120 is rotated. This disclosure describes rotating the ring magnet in a clockwise direction by the core 115 of the electric motor 120. However, the ring magnet 200 can be rotated by the core 115 in a counterclockwise direction, or alternately in both clockwise and counterclockwise directions according to commands sent by the controller 105.
[0011]
[0015] The position sensor 210 is electrically connected to the controller 105 and electrically couples a signal representative of the rotational position of the ring magnet 200 to the controller 105. The position sensor 210 comprises an anisotropic magnetoresistive (AMR) sensing device or a Hall effect device. The position sensor 210 is used to sense the magnetic field generated by the magnet segments positioned on the ring magnet 200 and transmit an electrical signal representative of the rotational position of the ring magnet 200. The signal from the sensor 210 can be used by the controller 105 to calculate the position of the core 115, to provide confirmation of the current position of the core 115, and to control the electric motor 120 to rotate the core 115 and place it in a selected or commanded position.
[0012]
[0016] 2 illustrates a diagram of a ring magnet 200 of the present disclosure. In FIG. 2, a top view 202 and a side view 204 of the ring magnet 200 are shown. The ring magnet 200 is configured to include a central portion 206 that is not magnetized and is arranged to be attached to the core 115 in any suitable fastening manner.
[0013]
[0017] The central portion 206 is surrounded by a magnet body 220 in the shape of a ring or other circular shape. The magnet body 220 can be rotated by the core 115 using the central portion 206. The ring magnet 200 depicted in FIG. 2 can be configured as an axially magnetized ring magnet. A fixed position sensor 210 is positioned proximate to the ring magnet 200, and in the top view 202, the position sensor 210 senses the ring magnet axially. Note that the position sensor 210 can also be positioned parallel to the magnet body 220, either above or below the ring magnet 202, as shown in the side view 204.
[0014]
[0018] Ring magnet 200 is configured as an asymmetrically magnetized ring, as evidenced by the asymmetric pattern of magnetic N-S segments positioned along the periphery of magnet body 220. Multiple magnetic poles (such as N-SNS) are generally configured along magnet body 220 in one or more segment pole pairs. Each pole pair includes a N (i.e., north) pole and a S (i.e., south) pole. In the example of FIG. 2, six pole pair segments with south and N poles are shown. This includes three pole pair segments 230a, 230b, and 230c, each consisting of a south pole that is smaller in size than its associated north pole. Three additional pole pair segments 240a, 240b, and 240c are positioned around the periphery of magnet body 220. Each pole pair segment 240a, 240b, and 240c has an equally sized south / south pole.
[0015]
[0019] In the embodiment of FIG. 2, each pole pair segment 230a, 230b, 230c has the same arc length. Each pole pair segment 240a, 240b, 240c also has the same, but smaller, arc length than pole pairs 230c, 230b, and 230c. Each pole pair segment 240a, 240b, and 240c spans a 45° angle around the magnet body 220. Each pole pair segment 240a, 240b, and 240c spans a 15° angle around the magnet body 220, totaling 45° and comprising the remainder of the circumference of the magnet body 220. Within each pole pair segment 230a, 230b, and 230c, the size of the north pole is the same as each north pole within each pole pair segment 230a, 230b, and 230c. Similarly, the south pole of each of pole pair segments 230a, 230b, and 230c has the same size as the respective south pole of pole pair segments 230a, 230b, and 230c. The north and south poles of each pole pair segment 240a, 240b, and 240c are the same size.
[0016]
[0020] Position sensor 210 is positioned to be stationary with respect to rotational displacement of ring magnet 200. Position sensor 210 is positioned to detect the magnetic field generated by pole pair segments 230a, 230b, 230c and 240a, 240b, and 240c positioned along the periphery of magnet body 220 as ring magnet 200 rotates.
[0017]
[0021] FIG. 3 shows a graph 300 illustrating the relationship between the magnetic analog signals generated by pole pair segments 230a, 230b, 230c, and 240a, 240b, 240c, in accordance with a preferred embodiment of the present invention. In graph 300, one period of magnetic analog signal 310 may be generated for each pole pair segment between the south and south pole polarities of the pole pair segments. The graph defines the south magnetic region as line 315 and the north magnetic region as line 320. Rotation of ring magnet 200 clockwise from a zero arc degree location generates a magnetic signal that swings north as it passes from the south pole of pole pair segment 230a to the north pole of pole pair segment 230a. The crossing between the south poles of pole pair segment 230a occurs at point 325 of analog signal 310. At crossing point 325 to the north pole, magnetic analog signal 310 reaches its maximum north magnetic strength at approximately 45 degrees of arc rotation of magnet body 220. Further rotation of the ring body continues swinging north until it reaches the south pole of pole pair 230b. The crossing from the north pole of pole pair 230a to the south pole of pole pair 230b occurs at crossover point 328. The maximum strength of the magnetic south signal occurs at approximately 90 degrees of rotation of magnet body 220. As shown at 350, the magnetic analog signal can be represented as a digital signal that cycles between 0v and 5v.
[0018]
[0022] The magnetic analog signal 310 generated by pole pair segments 230b and 230c generates magnetic analog signals in the same manner as described above for pole pair segment 230a because pole pair segments 230b and 230c have equal arc lengths to pole pair segment 230a. The maximum S magnetic analog signal for pole pair 230b occurs at approximately 90 degrees of rotation, and the maximum N magnetic analog signal occurs at 135 degrees of rotation. For pole pair 230c, the maximum S magnetic analog signal occurs at 180 degrees, and the maximum N magnetic analog signal occurs at 225 degrees of rotation.
[0019]
[0023] As magnet body 220 continues to rotate clockwise, it reaches crossover point 330 at the south pole of pole pair 240a. Magnetic analog signal 310 then swings north to crossover point 332 where it reaches maximum magnetic south strength at the south pole of pole pair segment 240b. As illustrated in FIG. 3, digital signal 351 of magnetic analog signal 310 generated by pole pair segment 240a is substantially smaller than digital signals 350 generated by each of pole pair segments 230a, 230b, and 230c.
[0020]
[0024] Because pole pairs 240b and 240c have an arc length equal to that of pole pair 240a, a series of three short digital signal pulses 351 representing a reference point for rotation of ring magnet 200 is generated by pole pair segments 240a, 240b, and 240c. For example, if three short digital signal pulses are coupled from sensor 210 to controller 105, this can signal to controller 105 that a home position 370 has been reached. The home position can be used to establish a reference point for the actuator for further commanded rotation to reach a specific location, or it can simply be used as a first actuation point, such as placing a valve in a first position. Further rotation through a S-to-N signal transition indicates that a second position 372 has been reached, which can place the valve in a second switching position. Further stop points 373 and 374 can be located by the sensing device at 180 and 270 degrees of rotation, respectively. The crossover between the magnetic analogue runouts can be used to signal the approach of a stop point. For example, the crossover point 328 from the north pole of pole pair segment 230a to the south pole of pole pair segment 230b occurs approximately 13 degrees before the location of maximum magnetic strength of the north pole. The crossover transition can be used as a signal that an actuator stop is approaching, and the actuator is adjusted to stop within a specific distance of reaching the crossover. The ring magnet of the present disclosure provides a unique N-S pattern that creates an identifiable home position and a repeatable, identifiable position as the ring magnet is rotated by the core 115. The ring magnet arrangement generates a specific magnetic wave pattern during rotation that is uniquely identifiable and repeatable in position.
[0021]
[0025] It will be advantageous to specify definitions of certain words and expressions used throughout this patent document. The term "communicate" and its derivatives encompass both direct and indirect communication. The terms "include" and "comprise," and their derivatives, mean inclusion without limitation. The term "or" is inclusive and / or. The expression "associated with" and its derivatives may mean including, contained within, interconnected with, containing, contained within, connected to or with, coupled to or with, communicable with, cooperate with, interleave with, juxtaposed with, proximate to, bound to or with, having the property of, having a relationship to or with, or the like. The expression "at least one of," when used in conjunction with a list of items, means that different combinations of one or more of the listed items may be used, and that only one item in the list may be required. For example, "at least one of A, B, and C" includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C.
[0022]
[0026] Nothing in this application should be read as suggesting that any particular element, step, or function is essential or critical to inclusion in the scope of the claims. The scope of the subject matter claimed for patent is defined solely by the allowed claims. Furthermore, none of the claims are intended to invoke 35 U.S.C. §112(f) with respect to any of the appended claims or claim elements unless the precise phrase “means for” or “step for” is expressly used within a particular claim, followed by a participial phrase identifying the function. The use of terms such as, but not limited to, “mechanism,” “module,” “apparatus (device),” “unit,” “component,” “element,” “member,” “apparatus,” “machine,” “system,” or “controller” within the claims is understood and intended to refer to structures known to those skilled in the art, as further modified or enhanced by the features of the claims themselves, and is not intended to invoke 35 U.S.C. §112(f).
[0023]
[0027] While this disclosure has described specific embodiments and generally associated methods, modifications and rearrangements of these embodiments and methods will be apparent to those skilled in the art. Accordingly, the above description of exemplary embodiments does not define or constrain this disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of this disclosure, as defined by the following claims.
Claims
1. 1. An apparatus for use in magnetic sensing applications, comprising: Magnetic polarity sensitive sensors, a ring magnet associated with the sensor, the ring magnet being magnetized to include multiple pole pairs of opposite magnetic polarity, at least one pole pair being larger than at least three other pole pairs; and a digital circuit associated with the sensor that detects each period of an analog signal generated by the magnetic polarity of each pole pair and couples the generated analog signal to the digital circuit to distinguish the three smaller pole pairs from the at least one larger pole pair; An apparatus comprising:
2. The apparatus of claim 1 , wherein the ring magnet includes a magnet body positioned at a periphery of the ring magnet.
3. The apparatus of claim 2 , wherein the ring magnet includes a non-magnetic central portion surrounded by the magnet body.
4. The apparatus of claim 2 , wherein the plurality of pole pairs are positioned on the magnet body.
5. The apparatus of claim 1 , wherein the sensor device is an anisotropic magnetoresistive (AMR) sensing device.
6. The apparatus of claim 1 , wherein the sensor device is a Hall effect device.
7. The apparatus of claim 2 , wherein the plurality of pole pairs includes three pole pairs that are larger than the at least three other pole pairs.
8. 8. The apparatus of claim 7, wherein the three larger pole pairs each have an equal arc length, and each larger pole pair includes a magnetic south pole that is smaller than its associated magnetic north pole.
9. 8. The apparatus of claim 7, wherein the three smaller pole pairs each have an equal arc length, and each smaller pole pair includes a south magnetic pole that is the same size as its associated north magnetic pole.
10. 2. The apparatus of claim 1, wherein the digital circuit is a digital controller configured to convert the analog signal into a digital signal used to distinguish the three smaller pole pairs from the at least one larger pole pair.
11. 1. A method for determining the position of a ring magnet fixed to a rotating device, comprising: positioning the ring magnet in proximity to a magnetic polarity sensitive sensor, the ring magnet being magnetized to include multiple magnetic pole pairs of opposite magnetic polarity, with at least one pole pair being larger than at least three other pole pairs; generating an output signal for each pole pair, the output signal corresponding to a period during which the sensor detects the magnetic polarity of the pole pair as the ring magnet is rotated by the device; coupling the output signal to a digital circuit that distinguishes the three smaller pole pairs from the at least one larger pole pair and determines the position of the ring magnet; A method comprising:
12. The method of claim 11 , wherein the ring magnet further comprises a magnet body positioned at a periphery of the ring magnet.
13. 13. The method of claim 12, wherein the ring magnet further comprises a non-magnetic central portion surrounded by the magnet body, the central portion being fixed to the rotating device such that when the device is rotated, the device rotates the central portion and the magnet body.
14. The method of claim 13 , wherein the plurality of pole pairs are positioned on the magnet body.
15. 12. The method of claim 11, wherein the step of generating an output signal includes using an anisotropic magnetoresistive (AMR) sensing device to generate an analog signal representative of the output signal.
16. The method of claim 11 , wherein the step of generating an output signal includes using a Hall effect device to generate an analog signal representative of the output signal.
17. The method of claim 12 , wherein the plurality of pole pairs includes three pole pairs that are greater than the at least three other pole pairs.
18. 18. The method of claim 17, wherein the three larger pole pairs each have equal arc lengths, and each larger pole pair includes a magnetic south pole that is smaller than its associated magnetic north pole.
19. 18. The method of claim 17, wherein the three smaller pole pairs each have an equal arc length, and each smaller pole pair includes a magnetic south pole that is the same size as its associated magnetic north pole.
20. 12. The method of claim 11 , wherein the step of coupling the output signal to a digital circuit includes using a digital controller to convert the output signal into a digital signal that is used to distinguish the three smaller pole pairs from the at least one larger pole pair and determine a position of the ring magnet.