ANGULAR POSITION SENSOR AND ASSOCIATED METHOD OF USE
An angular position sensor comprising two planar excitation coils forming a substantially circular interior area and two planar sensing coils positioned within a minor sector of the substantially circular interior area. Each of the two planar sensing coils comprises a clockwise winding portion and a counter-clockwise winding portion. The angular position sensor further comprises a substantially circular rotatable inductive coupling element positioned in overlying relation to the two planar sensing coils and separated from the two planar sensing coils by an airgap, wherein the substantially circular rotatable inductive coupling element comprises three, substantially evenly space, sector apertures.
Numerous industries, including the automotive, industrial and aerospace industries, place stringent reliability requirements on their position sensing systems. Potentiometers are commonly known in the art for use in position sensing systems and are specifically used for determining displacement angles of motor controlled or regulated elements. Although potentiometers are a relatively inexpensive solution for position sensing, they are also susceptible to the effects of adverse environmental conditions and are subject to failure resulting from numerous operations, over time. To overcome the disadvantages of potentiometer-based sensing systems, non-contact position sensors are increasingly being used to meet the stringent reliability requirements. Non-contact position sensors are currently known in the art and may be based on various principles, including inductive, capacitive, Hall effect or magneto-resistive principles.
A non-contact sensor based on inductive principles in commonly known as an inductive position sensor, or a resolver. An inductive position sensor comprises a coil assembly having one or more excitation coils and two or more sensing coils. In the operation of an inductive position sensor, an alternating current (AC) is injected into the excitation coil(s) which results in the generation of a time varying magnetic field in the vicinity of the excitation coil. The time varying magnetic field is sufficient to induce a time varying voltage in the sensing coils as a result of the mutual magnetic coupling between the excitation coil and the sensing coils. To determine an angular position of a rotatable target with respect to the coil assembly, a conductive target is rotatably positioned within the time varying magnetic field between the excitation coil and the sensing coils and separated from the coils by an airgap. The presence of the rotatable target within the time varying magnetic field changes the mutual magnetic coupling between the excitation coil and the sensing coils, relative to the position of the rotatable target. The change in mutual coupling between the excitation coil and the sensing coils alters the time varying voltage induced in the sensing coils. Since the magnitude of the voltage change induced in the sensing coils is generally sinusoidal with respect to the angular position of the rotatable target relative to the coil assembly, the time varying voltage within the sensing coils can be measured and processed to determine the angular position of the rotatable target.
A coil assembly commonly used in conventional electromechanical resolvers is comprised of axial windings wound on a Ferro-magnetic core. However, this type of resolver assembly is expensive and consumes a considerable amount of space. In order to reduce the cost and size of resolvers, it is also known in the art to form planar coils on one or more printed circuit boards (PCB) to provide the coil assembly of the resolver. The present trend in position sensors based on planar coils has resulted in an increased demand for position sensors that are light weight, low cost and reliable and that also provide improved noise immunity. For example, there is increasing demand in the automobile industry for position sensors having a small form factor, such as 6 mm, 12 mm and 15 mm diameters. Additionally, there is a need in the art for a small form factor position sensor that meets airgap and accuracy requirements. However, the design of planar coil assemblies for inductive sensors currently known in the art do not meet the airgap, accuracy and form factor size requirements.
Accordingly, what is needed in the art is a non-contact angular position sensor utilizing a planar coil assembly implemented in a small form factor which meets airgap and sensing accuracy requirements.
SUMMARY OF THE INVENTIONIn various embodiments, the present invention provides a system and method for sensing an angular position of a rotatable inductive coupling element. The system and method of the present invention provides an improved, non-contact, inductive, angular position sensor which provides for a reduced form factor while still meeting airgap and sensing. accuracy requirements.
In one embodiment, the present invention provides an angular position sensor including two planar excitation coils forming a substantially circular interior area. The angular position sensor further includes, two planar sensing coils positioned within a minor sector of the substantially circular interior area and each of the two planar sensing coils comprising a clockwise winding portion and a counter-clockwise winding portion. The angular position sensor additionally includes a substantially circular rotatable inductive coupling element positioned in overlying relation to the two planar sensing coils and separated from the two planar sensing coils by an airgap, wherein the substantially circular rotatable inductive coupling element comprises three sector apertures that are substantially evenly spaced on the circular rotatable inductive coupling element.
In a particular embodiment, the minor sector of the substantially circular interior area formed by the two planar excitation coils of the angular position sensor has a central angle of about 120° and each sector aperture of the substantially circular rotatable inductive coupling element has a central angle of about 30°. In this embodiment, each of the clockwise winding portion and the counter-clockwise winding portion of each of the two planar sensing coils are positioned within one of four equal subsectors of the minor sector of the substantially circular interior area and wherein each of the four equal subsectors of the minor sector has a central angle of about 30°.
In an additional embodiment, the present invention provides a method for sensing an angular position of a rotatable inductive coupling element, which includes, establishing a magnetic coupling between two planar excitation coils and two planar sensing coils to induce a time varying voltage in the two planar sensing coils, wherein the two planar sensing coils are positioned within a minor sector of a substantially circular interior area formed by the two planar excitation coils and wherein each of the two planar sensing coils comprises a clockwise winding portion positioned opposite a counter-clockwise winding portion. The method further includes, positioning a rotatable inductive coupling element comprising three sector apertures that are substantially evenly spaced on the circular rotatable inductive coupling element in overlying relation to the two planar excitation coils and separated from the two planar excitation coils by an airgap, the position of the rotatable inductive coupling element to cause a variation in a magnetic coupling between the two planar excitation coils and the winding portions of each of the two planar sensing coils. The method further includes, measuring a time varying voltage induced in the two planar sensing coils as a result of the variation in the magnetic coupling to determine an angular position of the rotatable inductive coupling element relative to the position of the two planar sensing coils.
The accompanying drawings, which are incorporated in and form a part of this specification, illustrate various embodiments and, together with the Description of Embodiments, serve to explain principles discussed below. The drawings referred to in this brief description should not be understood as being drawn to scale unless specifically noted.
Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying drawings. While various embodiments are discussed herein, it will be understood that they are not intended to be limiting. On the contrary, the presented embodiments are intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope the various embodiments as defined by the appended claims. Furthermore, in this Detailed Description of the Invention, numerous specific details are set forth in order to provide a thorough understanding. However, embodiments may be practiced without one or more of these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the described embodiments.
It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, regions, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
The present invention provides an inductive angular position sensor having a planar coil assembly that is implemented on a multilayer layer printed circuit board (PCB). The coil patterns of the sensing coils and additional supporting circuitry are positioned within an interior of the excitation coils, thereby providing a reduced form factor. Additionally, the layout of the excitation coils provides improved sensing accuracy and the increased number of winding turns on the sensing coils allows for a larger airgap and increased sensing amplitude.
With reference to
The planar excitation coils 105, 110 and winding portions 130, 135, 140, 145 of the first and second planar sensing coils may include one or more winding turns, as shown in
The position sensor 100 of the present invention additionally includes a substantially circular rotatable inductive coupling element 150 positioned in overlying relation to the winding portions 130, 135, 140, 145 of the first and second planar sensing coils and the two planar excitation coils 105, 110, as illustrated with reference to
As shown in
In the exemplary embodiment of
Referring again to
Additionally, as shown in
In operation of the angular position sensor 100, when the two planar excitation coils 105, 110 are excited at the resonant frequency, a time varying magnetic field is established in the vicinity of the two planar excitation coils 105, 110 which induces a time varying voltage in the first and second planar sensing coils 115, 125. Since the direction of the current flowing in the winding directions of the winding portions of the first and second planar sensing coils 115, 125 are opposite to each other, a zero net voltage is induced in the first and second planar sensing coils 115, 125. The voltage sensing circuitry 405 senses and measures the time varying voltage in the first and second planar sensing coils 115, 125. The rotatable inductive coupling element 150, as shown in
As illustrated in
In
In
In
In
As the rotatable inductive coupling element 160 is rotated through each of the positions shown in
As shown in the graph 500 of
In general, the graph 500 of
At operation 605, the method includes, establishing a magnetic coupling between two planar excitation coils and two planar sensing coils to induce a time varying voltage in the two planar sensing coils, wherein the two planar sensing coils are positioned within a minor sector of a substantially circular interior area formed by the two planar excitation coils and wherein each of the two planar sensing coils comprises a clockwise winding portion positioned opposite a counter-clockwise winding portion. With reference to
At operation 610, the method includes, positioning a rotatable inductive coupling element comprising three sector apertures that are substantially evenly spaced on the circular rotatable inductive coupling element in overlying relation to the two planar excitation coils and separated from the two planar excitation coils by an airgap, the position of the sector apertures of the rotatable inductive coupling element to cause a variation in a magnetic coupling between the two planar excitation coils and the winding portions of each of the two planar sensing coils. With reference to
At operation 615, the method includes, measuring a time varying voltage induced in the two planar sensing coils as a result of the variation in the magnetic coupling. With reference to
At operation 620, the method includes, determining a ratio of the measured time varying voltage of each of the two planar sensing coils to determine the angular position of the rotatable inductive coupling element relative to the position of the two planar sensing coils. With reference to
The system and method of the present invention provides an improved, non-contact, inductive, angular position sensor which utilizes a planar coil assembly that can be implemented on a multilayer printed circuit board (PCB) to provide improved accuracy and allow for a larger airgap.
In one embodiment, portions of the angular position sensor may be implemented in an integrated circuit as a single semiconductor die. Alternatively, the integrated circuit may include multiple semiconductor die that are electrically coupled together such as, for example, a multi-chip module that is packaged in a single integrated circuit package.
In various embodiments, portions of the system of the present invention may be implemented in a Field Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC). As would be appreciated by one skilled in the art, various functions of circuit elements may also be implemented as processing steps in a software program. Such software may be employed in, for example, a digital signal processor, microcontroller or general-purpose computer.
Unless specifically stated otherwise as apparent from the discussion, it is appreciated that throughout the description, discussions utilizing terms such as “measuring”, “determining”, “generating”, “applying”, “sending”, “encoding”, “locking”, or the like, can refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission, or display devices.
Further, for purposes of discussing and understanding the embodiments of the invention, it is to be understood that various terms are used by those knowledgeable in the art to describe techniques and approaches. Furthermore, in the description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be evident, however, to one of ordinary skill in the art that the present invention may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the present invention. These embodiments are described in sufficient detail to enable those of ordinary skill in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical, and other changes may be made without departing from the scope of the present invention.
Claims
1. An angular position sensor comprising:
- two planar excitation coils forming a substantially circular interior area;
- two planar sensing coils positioned within a minor sector of the substantially circular interior area, the minor sector comprising four equal subsectors, each of the two planar sensing coils comprising a clockwise winding portion and a counter-clockwise winding portion and each of the clockwise winding portions and counter-clockwise winding portions positioned in one of the four equal subsectors of the minor sector; and
- a substantially circular rotatable inductive coupling element positioned in overlying relation to the two planar sensing coils and separated from the two planar sensing coils by an airgap, wherein the substantially circular rotatable inductive coupling element comprises three sector apertures that are substantially evenly spaced on the circular rotatable inductive coupling element.
2. The angular position sensor of claim 1, wherein each of the sector apertures of the substantially circular rotatable inductive coupling element has dimensions substantially equal to one of the four equal subsectors of the minor sector of substantially circular interior area formed by the two planar excitation coils.
3. The angular sensor of claim 1, wherein the rotatable inductive coupling element is a rotatable conductive disk having a radius that is substantially equal to a radius of the two planar excitation coils.
4. The angular position sensor of claim 1, wherein the rotatable inductive coupling element is comprised of a non-ferromagnetic conductive material.
5. The angular position sensor of claim 1, wherein the minor sector of the substantially circular interior area has a central angle of about 120° and each of the three sector apertures of the substantially circular rotatable inductive coupling element has a central angle of about 30°.
6. The angular position sensor of claim 1, wherein each of the four equal subsectors of the minor sector has a central angle of about 30°.
7. The angular position sensor of claim 1, wherein the clockwise winding portion and the counter-clockwise winding portion of each of the two planar sensing coils are positioned in alternating subsectors of the minor sector.
8. The angular position sensor of claim 1, wherein each of the clockwise winding portion and the counter-clockwise winding portion of the two planar sensing coils comprises a plurality of winding turns and wherein a number of winding turns of the clockwise winding portion is equal to a number of winding turns of the counter-clockwise winding portion of each of the two planar sensing coils.
9. The angular position sensor of claim 1, wherein each of the two planar excitation coils comprises a plurality of winding turns.
10. The angular position sensor of claim 1, further comprising a multilayer substrate and wherein each of the two planar excitation coils are positioned on a different layers of the multilayer substrate.
11. The angular position sensor of claim 1, further comprising a multilayer substrate and wherein each of the clockwise winding portion and the counter-clockwise winding portion of each of the two planar sensing coils are positioned on a different layer of the multilayer substrate.
12. The angular position sensor of claim 1, further comprising a DC voltage source coupled to the two planar excitation coils.
13. The angular position sensor of claim 1, further comprising a capacitor coupled to each of the two planar excitation coils, the two planar excitation coils and the capacitors forming a cross-coupled resonant tank circuit.
14. The angular sensor of claim 1, further comprising voltage sensing circuitry coupled to each of the two planar sensing coils.
15. An angular position sensor comprising:
- two planar excitation coils forming a substantially circular interior area;
- two planar sensing coils positioned within a minor sector of the substantially circular interior area, the minor sector having a central angle of about 120° and each of the two planar sensing coils comprising a clockwise winding portion and a counter-clockwise winding portion, wherein each of the clockwise winding portion and the counter-clockwise winding portion are positioned within one of four equal subsectors of the minor sector of the substantially circular interior area and wherein each of the four equal subsectors of the minor sector has a central angle of about 30°; and
- a substantially circular non-ferromagnetic coupling element positioned in overlying relation to the two planar sensing coils and separated from the two planar sensing coils by an airgap, wherein the substantially circular rotatable inductive coupling element comprises three sector apertures that are substantially evenly spaced on the circular rotatable inductive coupling element, each sector aperture having a central angle of about 30°.
16. A method for sensing an angular position of a rotatable inductive coupling element, the method comprising:
- establishing a magnetic coupling between two planar excitation coils and two planar sensing coils to induce a time varying voltage in the two planar sensing coils, wherein the two planar sensing coils are positioned within a minor sector of a substantially circular interior area formed by the two planar excitation coils and wherein each of the two planar sensing coils comprises a clockwise winding portion positioned opposite a counter-clockwise winding portion;
- positioning a rotatable inductive coupling element comprising three sector apertures that are substantially evenly spaced on the circular rotatable inductive coupling element in overlying relation to the two planar excitation coils and separated from the two planar excitation coils by an airgap, the position of the sector apertures of the rotatable inductive coupling element to cause a variation in a magnetic coupling between the two planar excitation coils and the winding portions of each of the two planar sensing coils responsive to rotation of the positioned rotatable inductive coupling element; and
- measuring a time varying voltage induced in the two planar sensing coils as a result of the variation in the magnetic coupling to determine an angular position of the rotatable inductive coupling element relative to the position of the two planar sensing coils.
17. The method of claim 16, further comprising rotating the rotatable inductive coupling element to at least partially position one of the sector apertures over at least one of the winding portions of the two planar sensing coils to cause the variation in the magnetic coupling between the two planar excitation coils and the at least one winding portion.
18. The method of claim 16, wherein measuring the time varying voltage induced in the two planar sensing coils as a result of the variation in the magnetic coupling to determine the angular position of the rotatable inductive coupling element relative to the position of the two planar sensing coils further comprises:
- measuring the time varying voltage of each of the two planar sensing coils; and
- determining a ratio of the magnitudes of the measured time varying voltage of each of the two planar sensing coils to determine the angular position of the rotatable inductive coupling element relative to the position of the two planar sensing coils.
19. The method of claim 16, wherein the minor sector of the substantially circular interior area has a central angle of about 120° and each sector aperture of the substantially circular rotatable inductive coupling element has a central angle of about 30°.
20. The method of claim 16, wherein each of the clockwise winding portion and the counter-clockwise winding portion of each of the two planar sensing coils are positioned within one of four equal subsectors of the minor sector of the substantially circular interior area and wherein each of the four equal sub sectors of the minor sector has a central angle of about 30°.
Type: Application
Filed: Jul 13, 2020
Publication Date: Jan 13, 2022
Inventors: Ganesh Shaga (Warangal), Kevin Mark Smith, JR. (Dana Point, CA), Hwangsoo Choi (La Habra, CA), Sudheer Puttapudi (Hyderbad)
Application Number: 16/927,553