Accelerometer with proof mass displacement sensitivity reduction feature

Abstract

The invention discloses an accelerometer system, and the accelerometer system comprises a first magnetic assembly which comprises a first pole shoe; the second magnetic assembly comprises a second pole shoe, and the physical shape of the second pole shoe is different from that of the first pole shoe; and a proof mass assembly, the proof mass assembly comprising: a proof mass, the proof mass being between the first magnetic assembly and the second magnetic assembly. A first magnetic flux flows from the first magnetic assembly to the first pole shoe, wherein an amount of the first magnetic flux through the first coil is based on the physical shape of the first pole shoe; a second magnetic flux flows from the second magnetic assembly to the second pole shoe, and wherein a magnitude of the second magnetic flux is based on the physical shape of the second pole shoe.

Description

Technical Field

[0001] This disclosure relates to accelerometers. Background Technology

[0002] Accelerometers function by detecting the displacement of a test mass under inertial forces. Some accelerometers include a capacitive pickup system. For example, a conductive material (e.g., a capacitor plate) may be disposed on the upper surface of the test mass, and a similar conductive material may be disposed on the lower surface of the test mass. An acceleration or force applied along the sensitive axis of the accelerometer causes the test mass to deflect upward or downward, thereby changing the distance (e.g., capacitance gap) between the pickup capacitor plate and the upper and lower non-moving components. This change in capacitance gap causes a change in the capacitance of the capacitor element, which represents the displacement of the test mass along the sensitive axis. The change in capacitance can be used as a displacement signal, which can be applied to a servo system including one or more electromagnets (e.g., a force rebalancing coil) to return the test mass to a zero or rest position. Summary of the Invention

[0003] Generally, this disclosure relates to apparatus, systems, and techniques for reducing the impact of vibration on the accuracy and sensitivity of an accelerometer system. Vibration experienced by an example accelerometer system used to determine the acceleration of one or more devices can affect the induction of magnets within the accelerometer system, which can affect the scaling factor of the accelerometer system and the accuracy of the output generated by the accelerometer system. In some examples, minute variations in components of the accelerometer system can lead to an imbalance in the magnetic flux applied to opposite sides of a test mass. For example, when the test mass moves out of zero, this imbalance can cause a decrease in the accuracy of the output generated by the accelerometer system.

[0004] The apparatus, system, and techniques described in this disclosure alter the distribution of magnetic flux around the test mass, for example, to reduce magnetic flux imbalance and minimize net changes in magnetic flux within the system, such as due to movement of the test mass within the accelerometer. This can result in a reduction of the effect of vibration on the output of the accelerometer system, thereby improving the accuracy of the accelerometer system compared to other accelerometer systems.

[0005] In some examples, this disclosure describes an accelerometer system comprising: a first magnetic assembly including a first pole shoe, a first excitation ring, and a first magnet configured to generate a first magnetic flux; a second magnetic assembly including a second pole shoe, a second excitation ring, and a second magnet configured to generate a second magnetic flux, wherein the physical shape of the second pole shoe differs from that of the first pole shoe; a test mass assembly including: a test mass block positioned between the first and second magnetic assemblies; and a first coil disposed around the first pole shoe, wherein... A first magnetic flux flows from a first excitation ring through a first coil to a first pole shoe, and wherein the magnitude of the first magnetic flux through the first coil is based on the physical shape of the first pole shoe; a second coil is arranged around a second pole shoe, wherein a second magnetic flux flows from a second excitation ring through the second coil to the second pole shoe, and wherein the magnitude of the second magnetic flux through the second coil is based on the physical shape of the second pole shoe; and a processing circuit configured to: cause a first current to flow through the first coil to apply a first Lorentz force to the test mass block; and cause a second current to flow through the second coil to apply a second Lorentz force to the test mass block.

[0006] In some examples, this disclosure describes an accelerometer system comprising: a first magnetic assembly including a first pole shoe, a first excitation ring, and a first magnet configured to generate a first magnetic flux; a second magnetic assembly including a second pole shoe, a second excitation ring, and a second magnet configured to generate a second magnetic flux; a test mass assembly including a test mass between the first and second magnetic assemblies; and a first coil disposed around the first pole shoe, wherein the first magnetic flux flows from the first excitation ring through the first coil to the first pole shoe, and wherein the first magnetic flux passes through the first excitation ring through the first coil to the first pole shoe. The first magnetic flux of a coil is based on the physical shape of a first pole shoe; a second coil is arranged around a second pole shoe, wherein a second magnetic flux flows from a second excitation ring through the second coil to the second pole shoe, and wherein the magnitude of the second magnetic flux through the second coil is based on the physical shape of the second pole shoe; and a processing circuit configured to: allow a first current to flow through the first coil to apply a first Lorentz force to a test mass block; and allow a second current to flow through the second coil to apply a second Lorentz force to the test mass block, wherein at least one of the first or second pole shoes defines a chamfer extending around the outer periphery of the at least one pole shoe.

[0007] In some examples, this disclosure describes an accelerometer system comprising: a first magnetic assembly including a first pole shoe, a first excitation ring, and a first magnet configured to generate a first magnetic flux; a second magnetic assembly including a second pole shoe, a second excitation ring, and a second magnet configured to generate a second magnetic flux, wherein the physical shape of the second excitation ring differs from the physical shape of the first excitation ring; a test mass assembly including: a test mass block positioned between the first and second magnetic assemblies; and a first coil disposed around the first pole shoe, wherein... A first magnetic flux flows from a first excitation ring through a first coil to a first pole shoe, and wherein the magnitude of the first magnetic flux through the first coil is based on the physical shape of the first excitation ring; a second coil is arranged around a second pole shoe, wherein a second magnetic flux flows from a second excitation ring through the second coil to the second pole shoe, and wherein the magnitude of the second magnetic flux through the second coil is based on the physical shape of the second excitation ring; and a processing circuit configured to: cause a first current to flow through the first coil to apply a first Lorentz force to the test mass block; and cause a second current to flow through the second coil to apply a second Lorentz force to the test mass block.

[0008] The present invention is intended to provide an overview of the subject matter described herein. It is not intended to provide an exclusive or exhaustive description of the systems, apparatus, and methods detailed in the following drawings and specification. Further details of one or more examples of this disclosure are set forth in the following drawings and specification. Other features, objects, and advantages will be apparent from the description and drawings, as well as from the claims. Attached Figure Description

[0009] Figure 1 This is a block diagram illustrating an accelerometer system according to one or more technologies of this disclosure.

[0010] Figure 2 It shows Figure 1 A conceptual diagram of a side cross-section of an example accelerometer system.

[0011] Figure 3 It shows Figure 2 A conceptual diagram of the test mass block and pole shoes of the accelerometer system.

[0012] Figure 4 It shows Figure 1 A conceptual diagram of a side cross-section of another example of an accelerometer system.

[0013] Figure 5 It shows the use of Figure 1 A flowchart illustrating an example technique for determining acceleration using an electromagnetic accelerometer.

[0014] Figure 6It shows the manufacturing process. Figure 1 A flowchart illustrating an example technique for electromagnetic accelerometers.

[0015] Similar reference characters are used to denote similar elements throughout the specification and drawings. Detailed Implementation

[0016] This disclosure relates to apparatus, systems, and techniques for determining the acceleration of an object using an accelerometer system. For example, the accelerometer system may be an electromagnetic accelerometer system configured to accurately measure acceleration values. The electromagnetic accelerometer system uses a combination of electrical and magnetic signals to determine the acceleration of an object. For example, the accelerometer system may include magnetic pole shoes, an electric coil, a non-moving member, and a test mass. Magnetic flux can travel from the pole shoes through the coil to the non-moving member and back to the test mass. Current can flow through the coil. The accelerometer system can generate a Lorentz force based on the magnetic flux and current, which represents a servo effect preventing displacement of the test mass.

[0017] In some cases, the accelerometer system is configured to measure the acceleration of an object in real time or near real time, allowing processing circuitry to analyze the object's acceleration over a time period to determine the object's positional displacement during that period. For example, the accelerometer system may be part of an inertial navigation system (INS) used to track the object's position based at least in part on its acceleration. Alternatively, the accelerometer system may be positioned on or within the object, causing it to accelerate along with the object. Thus, when the object accelerates, the accelerometer system (including a mass sensing block) accelerates along with the object. Since acceleration over time is the derivative of velocity over time, and velocity over time is the derivative of position over time, in some cases, the processing circuitry may be configured to determine the object's positional displacement by performing a double integral of the object's acceleration over a time period. Determining the object's position using an accelerometer system positioned on the object without using an external navigation system (e.g., a Global Navigation Satellite System (GNSS)) can be termed "dead reckoning."

[0018] An accelerometer system can experience vibrations during an object's acceleration. For example, an object may vibrate during movement and / or acceleration, and these vibrations can be transmitted to the accelerometer system. Under vibration, a test mass can move into and out of zero position.

[0019] In a balanced accelerometer system, the test mass is held at zero position within the accelerometer system. In some examples, such as due to variations in components used to manufacture the accelerometer system and / or differences in magnetic induction, the accelerometer system may include an unbalanced magnetic flux loop. An imbalance in the magnetic flux loop can cause the test mass to shift from zero, which can affect the accuracy of the acceleration values ​​determined by the accelerometer system. For example, variations in components between magnetic assemblies on opposite sides of the test mass can generate different Lorentz forces, leading to an imbalance of Lorentz forces on opposite sides of the test mass, thus allowing the test mass to shift.

[0020] The apparatus, system, and techniques described herein reduce the impact of test mass displacement on the accuracy of acceleration values ​​determined by the accelerometer system. The apparatus, system, and techniques compensate for test mass displacement by balancing the magnetic flux loop of the accelerometer system, thereby reducing the net change in magnetic flux in the accelerometer system due to test mass movement. The apparatus, system, and techniques address existing asymmetries in the accelerometer system by redistributing the magnetic flux flow within the accelerometer system via one or more features within the system. This redistribution of the magnetic flux flow can create an asymmetry in the magnetic flux loop that cancels out another existing asymmetry in the accelerometer system to balance it. This feature improves the symmetry of the magnetic flux loop between different magnetic components of the accelerometer system, which improves the balance between the Lorentz forces acting on the test mass, thereby reducing and / or eliminating the impact of test mass movement on the Lorentz forces and, consequently, the acceleration values ​​output by the accelerometer system.

[0021] Figure 1 This is a block diagram illustrating an accelerometer system 100 according to one or more technologies of this disclosure. Figure 1 As shown, the accelerometer system 100 includes a processing circuit 102, a test mass block 104, a first pole shoe 106A, a second pole shoe 106B (collectively referred to as "pole shoe 106"), a first non-moving component 108A, a second non-moving component 108B (collectively referred to as "non-moving component 108"), a first coil 110A, a second coil 110B (collectively referred to as "coil 110"), a first sensor 112A, and a second sensor 112B (collectively referred to as "sensor 112").

[0022] The accelerometer system 100 is configured to determine the relationship between an object and its surroundings based on the magnitude of one or more electrical signals transmitted to the coil 110. Figure 1(Not shown in the image) The associated acceleration, this electrical signal prevents the inspection mass block 104 from shifting from zero position. For example, a first sensor 112A may be configured to generate a first sensing signal indicating the size of the gap between the inspection mass block 104 and the first non-moving member 108A; and a second sensor 112B may be configured to generate a second sensing signal indicating the size of the gap between the inspection mass block 104 and the second non-moving member 108B. The processing circuit 102 may generate a first electrical signal for transmission to the first coil 110A based on the first sensing signal, and may generate a second electrical signal for transmission to the second coil 110B based on the second sensing signal. The first and second electrical signals may generate one or more Lorentz forces to prevent the inspection mass block 104 from shifting from zero position. For example, the first electrical signal may generate a first Lorentz force and the second electrical signal may generate a second Lorentz force, wherein the first and second Lorentz forces interact with the inspection mass block 104 to suppress the inspection mass block 104 from shifting from zero position.

[0023] The Lorentz force represents the force caused by the interaction of an electric field and a magnetic field. For example, the Lorentz force can be defined by the cross product of the electric and magnetic fields, where the direction of the Lorentz force depends on the directions of the electric and magnetic fields, and the magnitude of the Lorentz force depends on the magnitudes of the electric and magnetic fields.

[0024] Processing circuitry 102 may include one or more processors configured to implement functions and / or processing instructions for execution within accelerometer system 100. For example, processing circuitry 102 may be able to process instructions stored in memory. Processing circuitry 102 may include, for example, a microprocessor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or integrated logic circuitry, or a combination of any of the foregoing. Therefore, processing circuitry 102 may include any suitable structure, whether in hardware, software, firmware, or any combination thereof, to perform the functions described herein for processing circuitry 102.

[0025] Memory ( Figure 1 (Not shown) can be configured to store information within the accelerometer system 100 during operation. The memory may include a computer-readable storage medium or a computer-readable storage device. In some examples, the memory includes one or more of short-term memory or long-term memory. The memory may include, for example, random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), magnetic disk, optical disk, flash memory, or electrically programmable memory (EPROM) or electrically erasable programmable memory (EEPROM). In some examples, the memory is used to store program instructions executed by the processing circuitry 102.

[0026] Processing circuit 102 can generate a first electrical signal and a second electrical signal as part of one or more negative feedback loops that hold the inspection mass block 104 at a zero position. Processing circuit 102, first coil 110A, and first sensor 112A represent components of the first negative feedback loop. The first negative feedback loop can maintain the width of the gap between the inspection mass block 104 and the first non-moving member 108A at a first zero width. For example, the first sensor 112A can generate a first sensing signal indicating a capacitance value. The capacitance value is associated with the width of the gap between the inspection mass block 104 and the first non-moving member 108A, and the first sensing signal is transmitted to processing circuit 102. Processing circuit 102 can generate a first electrical signal based on the first sensing signal and transmit the first electrical signal to first coil 110A to maintain the capacitance value of the first sensing signal at a first zero capacitance value. By generating the first electrical signal to maintain the capacitance value of the first sensing signal at a first zero capacitance value, processing circuit 102 maintains the width of the gap between the inspection mass block 104 and the first non-moving member 108A at a first zero width.

[0027] Processing circuit 102, second coil 110B, and second sensor 112B represent components of a second negative feedback loop. The second negative feedback loop maintains the width of the gap between the test mass block 104 and the second non-moving member 108B at a second zero width. For example, the second sensor 112B can generate a second sensing signal indicating a second capacitance value. The capacitance value is associated with the width of the gap between the test mass block 104 and the second non-moving member 108B, and the second sensing signal is transmitted to processing circuit 102. Processing circuit 102 can generate a second electrical signal based on the second sensing signal and transmit the second electrical signal to second coil 110B to maintain the capacitance value of the second sensing signal at a second zero capacitance value. By generating a second electrical signal to maintain the second capacitance value of the second sensing signal at a second zero capacitance value, processing circuit 102 maintains the width of the gap between the test mass block 104 and the second non-moving member 108B at a second zero width.

[0028] In addition, by keeping the width of the gap between the inspection mass block 104 and the first non-moving member 108A at a first zero width and the width of the gap between the inspection mass block 104 and the second non-moving member 108B at a second zero width, the processing circuit 102 can keep the position of the inspection mass block 104 relative to the non-moving member 108 at zero.

[0029] As the acceleration of the accelerometer system 100 changes along the sensing axis, the final acceleration force applied to the test mass 104 can change. Therefore, the processing circuit 102 can change the magnitude of a first electrical signal transmitted to the first coil 110A and a second electrical signal transmitted to the second coil 110B to prevent the test mass 104 from shifting relative to the non-moving member 108. In one example, the acceleration along the sensing axis can increase from a first acceleration value to a second acceleration value. The processing circuit 102 can change the magnitude of the first electrical signal and the magnitude of the second electrical signal to account for the change in acceleration, such that the test mass 104 remains at zero relative to the non-moving member 108. The processing circuit 102 can determine the acceleration of the accelerometer system 100 along the sensing axis based on the magnitude of the first electrical signal transmitted to the first coil 110A and the magnitude of the second electrical signal transmitted to the second coil 110B.

[0030] In some examples, the magnitude of the first electrical signal transmitted to the first coil 110A is proportional to the acceleration along the sensing axis. In some examples, the magnitude of the second electrical signal transmitted to the second coil 110B is proportional to the acceleration along the sensing axis. Thus, an increase in the magnitude of the first electrical signal can correspond to an increase in the acceleration along the sensing axis, and an increase in the magnitude of the second electrical signal can correspond to an increase in the acceleration along the sensing axis. Alternatively, a decrease in the magnitude of the first electrical signal can correspond to a decrease in the acceleration along the sensing axis, and a decrease in the magnitude of the second electrical signal can correspond to a decrease in the acceleration along the sensing axis.

[0031] The accelerometer system 100 may include a first flux loop and a second flux loop. The first flux loop may include a first pole shoe 106A, a first non-moving member 108A, and a first coil 110A. Within the first flux loop, a first magnetic flux may travel from the first pole shoe 106A through the first coil 110A to the first non-moving member 108A. The first magnetic flux then travels through the first non-moving member 108A back to the first pole shoe 106A. In some examples, the first pole shoe 106A may include a first magnet that generates the first magnetic flux. The second flux loop may include a second pole shoe 106B, a second non-moving member 108B, and a second coil 110B. Within the second flux loop, a second magnetic flux may travel from the second pole shoe 106B through the second coil 110B to the second non-moving member 108B. The second magnetic flux then travels through the second non-moving member 108B back to the second pole shoe 106B. In some examples, the second pole shoe 106B may include a second magnet that generates a second magnetic flux.

[0032] Accelerometer system 100 can represent a servo system that uses a Lorentz force parallel to the sensing axis to counteract acceleration along the sensing axis. For example, if accelerometer system 100 accelerates along the sensing axis, the acceleration can apply an accelerating force to test mass 104, wherein the accelerating force is applied to test mass 104 in the opposite direction to the acceleration of accelerometer system 100. Processing circuit 102 transmits a first electrical signal to first coil 110A and a second electrical signal to second coil 110B to generate one or more Lorentz forces to counteract the accelerating force generated by acceleration along the sensing axis. That is, one or more Lorentz forces are applied to test mass 104 in the opposite direction to the accelerating force, such that test mass 104 does not shift from zero position due to the accelerating force. The magnitude of the accelerating force varies based on the change in the magnitude of acceleration along the sensing axis. Therefore, in order to prevent the inspection mass block 104 from shifting from the zero position, the processing circuit 102 changes the value of the first electrical signal transmitted to the first coil 110A and the value of the second electrical signal transmitted to the second coil 110B, so as to change the value of one or more Lorentz forces that counteract the acceleration signal.

[0033] The Lorentz force is a force generated by the interaction between an electric field and a magnetic field. As discussed above, the accelerometer system 100 includes a first magnetic flux loop and a second magnetic flux loop. The first magnetic flux loop includes a channel for a first magnetic flux from pole shoe 106A through a first coil 110A to a first non-moving member 108A. A first electrical signal flows through the first coil 110A. The first magnetic flux and the first electrical signal cause a first Lorentz force to be applied to the test mass 104 in the opposite direction to the accelerating force applied to the test mass 104 due to acceleration along the sensing axis. Additionally, the second magnetic flux loop includes a channel for a second magnetic flux from second pole shoe 106B through a second coil 110B to a second non-moving member 108B. A second electrical signal flows through the second coil 110B. The second magnetic flux and the second electrical signal cause a second Lorentz force to be applied to the test mass 104 in the opposite direction to the accelerating force applied to the test mass 104 due to acceleration along the sensing axis.

[0034] In some examples, the magnetic flux generated by the pole shoe 106 may be asymmetrical due to variations in components of the accelerometer system 100 (e.g., pole shoe 106, non-moving member 108, and / or coil 110) and / or torque on the test mass 104. This asymmetry in the magnetic flux can lead to an imbalance in the Lorentz force generated by an electrical signal and applied to the test mass 104, thereby enabling the test mass 104 to move within the accelerometer system 100. This movement of the test mass 104 can affect the output of the accelerometer system 100.

[0035] The accelerometer system 100 may include one or more of pole shoes 106 or non-moving members 108, characterized by being configured to adjust the distribution of magnetic flux within the accelerometer system 100, for example, to improve the symmetry of the magnetic flux and the balance of the Lorentz force generated within the accelerometer system 100. Components such as pole shoes 106 and / or non-moving members 108 may include one or more features that alter the magnetic reluctance of the component. One or more features may include, but are not limited to, chamfers, fillets, material variations, dimensional variations, passages, openings, cavities, protrusions, etc.

[0036] One or more features can alter the magnetic reluctance of a component to create an asymmetry in the magnetic field at opposite ends of the test mass 104. For example, one or more features can cause a first magnetic flux to differ from a second magnetic flux. The variation in the magnetic reluctance of a component can alter the path of magnetic flux through the component. For example, the variation in the magnetic reluctance of a component can reduce the concentration of magnetic flux at one or more locations within the accelerometer system 100 (e.g., along the surfaces and / or edges closest to the test mass 104 and / or coil 110). The adjusted path of travel can create an asymmetry in magnetic flux across opposite ends of the test mass 104, which can counteract magnetic flux asymmetry caused by variations in the component and / or torque on the test mass 104, for example, as discussed previously herein.

[0037] The cancellation of magnetic flux asymmetry (e.g., asymmetry arising from changes in reluctance characteristics counteracting asymmetry arising from variations in components and / or torque on the test mass 104) can result in a balance of magnetic flux and Lorentz force across opposite ends of the test mass 104. This balance of magnetic flux and Lorentz force minimizes and / or eliminates the net change in magnetic flux due to displacement of the test mass 104, which improves the accuracy of the accelerometer system 100's output. For example, the accelerometer system 100 can reduce the net change in magnetic flux within the accelerometer system 100 due to displacement of the test mass 104. For example, by adjusting the distribution of magnetic flux through coil 110, due to the displacement of the test mass 104, the accelerometer system 100 can experience a gain in magnetic flux through one coil of coil 110 (e.g., through first coil 110A), which is equal to or substantially equal to the loss in magnetic flux through another coil of coil 110 (e.g., through second coil 110B) due to the same displacement of the test mass 104.

[0038] Figure 2 This is a conceptual diagram showing a side cross-sectional view of an accelerometer system 100 according to one or more technologies of this disclosure. Figure 2As can be seen, the accelerometer system 100 includes a test mass assembly 204, a first pole shoe 106A, a second pole shoe 106B, a first non-moving component 108A, a second non-moving component 108B, a first coil 110A, a second coil 110B, a first magnet 220A, and a second magnet 220B (collectively referred to as "magnet 220"). The test mass assembly 204 includes a test mass 104, a first capacitor plate 205A, and a second capacitor plate 205B (collectively referred to as "capacitor plate 205"). Figure 2 In the example, the accelerometer system 100 also includes central raised pads 222A to 222B (collectively referred to as "central raised pad 222"), outer raised pads 224A to 224D (collectively referred to as "outer raised pad 224"), a first band 226A, a second band 226B (collectively referred to as "band 226"), a first capacitor gap 232, and a second capacitor gap 234. Figure 2 In one example, the accelerometer system 100 may include accelerometer supports 214A to 214B (collectively referred to as “accelerometer support 214”), which may be formed by a combination of pole shoe 106, non-moving member 108 and magnet 220.

[0039] Accelerometer system 100 can be configured to sense acceleration along sensing axis 201. For example, accelerometer system 200 can be configured to sense acceleration along sensing axis 201 in a first direction 211A. In some cases, accelerometer system 200 determines the magnitude of acceleration along sensing axis 201 in the first direction 211A with real-time or near real-time precision, such that processing circuitry ( Figure 2 (Not shown in the image) Dead reckoning can be used to track the position of the accelerometer system 200. For example... Figure 2 As can be seen, the test mass assembly 204 is suspended between the first non-movable member 108A and the second non-movable member 108B via the central protrusion 222 and the outer protrusion 224. In some examples, the processing circuitry may receive a first sensing signal indicating the width of the first capacitor gap 232 and a second sensing signal indicating the width of the second capacitor gap 234. The processing circuitry may then transmit a first electrical signal to the first coil 110A and a second electrical signal to the second coil 110B to prevent the test mass 104 from displacing in response to the acceleration of the accelerometer system 100 along the sensing axis 201. The magnitudes of the first and second electrical signals may be correlated with the magnitude of the acceleration.

[0040] Non-movable member 108 may be attached (e.g., clamped to) the central raised pad 222 and the outer raised pad 224 to secure the test mass assembly 204 between the first non-movable member 108A and the second non-movable member 108B. The term "non-movable member" may refer to a member indicating a reference position to which the position of the test mass assembly 204 can be compared. In other words, the position of the test mass assembly 204 may indicate the position of the test mass assembly 204 relative to the non-movable member 108. In some examples, the non-movable member 108 comprises a bimetallic material that may be part of a flux loop. In some examples, the non-movable member 108 may resemble the stator of a variable capacitor.

[0041] Coil 110 is conductive, allowing electrical signals to flow through it. For example, a first electrical signal can flow through the path of the first coil 110A, and a second electrical signal can flow through the path of the second coil 110B. The path of each coil in coil 110 can define a circular, elliptical, square, triangular, or other polygonal path. Each coil in coil 110 extends completely around the outer surface of the corresponding pole piece in pole piece 106, for example, such that a first electrical signal flows around the outer surface of pole piece 106A through the first coil 110A, and a second electrical signal flows around the outer surface of pole piece 106B through the second coil 110B.

[0042] The band 226 is a metal piece that fastens the first non-movable member 108A to the second non-movable member 108B. In some examples, the band 226 may be attached (e.g., bonded with epoxy resin) to the non-movable member 108 when it is attached to the test mass block assembly 204 via the central raised pad 222 and the outer raised pad 224. The accelerometer system 100 includes a first capacitance gap 232 and a second capacitance gap 234. The first capacitance gap 232 represents the gap between the first capacitor plate 205A and the first non-movable member 108A, and the second capacitance gap 234 represents the gap between the second capacitor plate 205B and the second non-movable member 108B. The first capacitor plate 205A can generate a first sensing signal indicating a first capacitance value. The first capacitance value is associated with the width of the first capacitance gap 232. The second capacitor plate 205B can generate a second sensing signal indicating a second capacitance value. The second capacitance value is associated with the width of the second capacitance gap 234. In this way, the first capacitor plate 205A can represent Figure 1 The first sensor 112A and the second capacitor plate 205B can represent Figure 1 The second sensor 112B. Processing circuit ( Figure 2 (Not shown) can receive a first sensing signal and a second sensing signal, and control the electrical signal transmitted to the coil 110 based on the first sensing signal and the second sensing signal.

[0043] In some examples, the zero width of the first capacitor gap 232 may be defined by the widths of the outer raised pad 224 and the central raised pad 222. In some examples, the zero width of the first capacitor gap 232 is in the range of 0.0127 mm (e.g., about 0.0005 inches) to 0.0635 mm (e.g., about 0.0025 inches). In some examples, the zero width of the second capacitor gap 234 may be defined by the widths of the outer raised pad 224 and the central raised pad 222. In some examples, the zero width of the second capacitor gap 234 is in the range of 0.0127 mm (e.g., about 0.0005 inches) to 0.0635 mm (e.g., about 0.0025 inches). When the width of the first capacitor gap 232 is at its zero width and the width of the second capacitor gap 234 is at its zero width, the inspection mass block 104 may be located at zero. That is, the mass block 104 can be located at zero position, so that the processing circuit is configured to determine the acceleration along the sensing axis 201 based on the first electrical signal transmitted to the first coil 110A and the second electrical signal transmitted to the second coil 110B.

[0044] In some examples, the first capacitor gap 232 may have a first capacitance value. The processing circuitry can detect the first capacitance value of the first capacitor gap 232, which can be detected and used in a closed-loop differential capacitor configuration to determine the acceleration of the accelerometer system 100. Additionally, the second capacitor gap 234 may have a second capacitance value. The processing circuitry can detect the second capacitance value of the second capacitor gap 234, which can be detected and used in a closed-loop differential capacitor configuration to determine the acceleration of the accelerometer system 100. In some examples, an increase in the width of the first capacitor gap 232 and a decrease in the width of the second capacitor gap 234 can indicate the acceleration of the accelerometer system 100 in a first direction 211A. Conversely, an increase in the width of the second capacitor gap 234 and a decrease in the width of the first capacitor gap 232 can indicate the acceleration of the accelerometer system 200 in a second direction 211B. The processing circuitry can transmit a first electrical signal to the first coil 110A and a second electrical signal to the second coil 110B to counteract the displacement of the test mass block 104 from its zero position. The magnitudes of the first and second electrical signals can be correlated with the magnitude of the acceleration along the sensing axis 201.

[0045] Magnet 220 is a magnet used to provide a magnetic field to drive the magnetic circuit of magnet 220, pole shoe 106, coil 110, and non-moving member 108. In some examples, magnet 220 may be made of AlNiCo alloy, samarium-cobalt, neodymium-iron-boron, or other such materials. In some examples, magnet 220 may receive forces and / or stresses transmitted from non-moving member 208 due to the construction of accelerometer system 100. In some examples, magnet 220 may be part of a null metering configuration of accelerometer system 100.

[0046] The pole shoe 106 is a magnetic structure that enables the magnetic field of magnet 220 to be focused and drive the magnetic circuit of magnet 220, pole shoe 106, coil 110, and non-moving member 108. For example, the pole shoe 106 may be a magnetic structure that allows the magnetic field of the magnet to bend and flow through coil 110. In these examples, by allowing the magnetic field of magnet 220 to pass through coil 110, the magnetic field of magnet 220 can enter and flow around non-moving member 108 to the opposite side of the magnet, and flow back to the test mass block through the magnet, thus completing the magnetic circuit. For example, the first magnetic circuit may represent a flux loop in which a first magnetic flux is transferred from the first magnet 220A to the first pole shoe 106A. The first magnetic flux travels from the first pole shoe 106A through the first coil 110A to the first non-moving member 108A. Then, the first magnetic flux travels back to the first magnet 220A through the first non-moving member 108A to complete the first magnetic circuit. The second magnetic circuit can represent a magnetic flux loop, wherein a second magnetic flux is transferred from the second magnet 220B to the second pole shoe 106B. The second magnetic flux travels from the second pole shoe 106B through the second coil 110B to the second non-moving member 108B. Then, the second magnetic flux travels back to the second magnet 220B through the second non-moving member 108B to complete the second magnetic circuit.

[0047] In some examples, the pole piece 106 may be part of the zero-meter configuration of the accelerometer system 100. In some examples, the pole piece 106 may be made of a magnetically permeable material, such as Invar alloy, nickel-iron high-permeability alloy, iron-nickel alloy, or other such materials.

[0048] In some examples, the accelerometer system 100 may include coils 110 attached to each side of the test mass. In some examples, the accelerometer system 100 may include processing circuitry. Figure 2(Not shown in the image), the processing circuitry is configured to transmit a first electrical signal and a second electrical signal to coil 110 to position the test mass block 104 at zero. In some examples, as the accelerometer system 100 accelerates along sensing axis 201, the processing circuitry may increase the current magnitude of the first electrical signal and the current magnitude of the second electrical signal to hold the test mass block 104 at zero. In this example, the current magnitudes of the first and second electrical signals are proportional to the magnitude of the acceleration along sensing axis 201.

[0049] Preventing the inspection mass block 104 from shifting from zero may be referred to herein as a "servo effect." In some examples, the processing circuitry can cause one or more Lorentz forces to counteract the acceleration force applied to the inspection mass block 104, preventing the inspection mass block 104 from moving from zero. This means that the processing circuitry is configured to adjust one or more Lorentz forces in real time or nearly real time, such that one or more Lorentz forces counteract the acceleration force applied to the inspection mass block 104 at any given time, thereby continuously holding the inspection mass block 104 at zero. The processing circuitry can generate the electrical signals required to produce one or more Lorentz forces based on a first sensing signal received from the first capacitor plate 205A and a second sensing signal received from the second capacitor plate 205B.

[0050] Coil 110 can be mounted on either side of the test mass 104 of the test mass assembly 204. In some examples, the processing circuitry can modify the current from coil 110 to the servo test mass 104 to maintain a zero position. Any acceleration of the accelerometer system 100 will instantaneously move the test mass of the test mass assembly 204 out of the zero-position plane, and the increase in current required to hold the test mass 104 at zero is proportional to the magnitude of the acceleration of the accelerometer system 100 along the sensing axis 201.

[0051] although Figure 2 An accelerometer system 100 is shown with capacitor plates and coils on both sides of the test mass assembly 204 to form a combined capacitance pickup system. However, it should be understood that the accelerometer system 100 may have capacitor plates and coils only on one side of the test mass assembly 204. Similarly, although... Figure 2 An accelerometer system 100 is shown with non-movable members on both sides of the test mass assembly 204 to form a combined capacitive pickup system. However, it should be understood that the accelerometer system 100 may have non-movable members and capacitor plates on the same side of the test mass assembly 204.

[0052] like Figure 2 As shown, one or more pole shoes in pole shoe 106 may include features 240 at or around the distal end of the pole shoe. For example, as Figure 2As shown, the second pole shoe 106B may include a feature 240 extending around the distal edge of the second pole shoe 106B. Feature 240 may include, but is not limited to, chamfers, fillets, recesses, passages, openings, protrusions, etc. Although feature 240 is primarily described herein as a chamfer, feature 240 may be any of the example features listed herein.

[0053] Feature 240 removes a portion of the magnetically conductive material at or around the distal end of the corresponding pole piece 106 (e.g., the second pole piece 106B). The distal end of the corresponding pole piece 106 refers to the end of the pole piece 106 closest to the test mass assembly 204 along the sensing axis 201. In an example pole piece 106 without feature 240 (e.g., the first pole piece 106A), the magnetic flux is concentrated at the distal edge of the pole piece 106 (e.g., the edge defining the outer periphery of the distal end of the pole piece) and flows from the pole piece 106 to the corresponding coil 110 (e.g., the first coil 110A) at the distal edge. Feature 240 removes the magnetically conductive material at the distal edge of the pole piece, which redirects the magnetic flux flow from the second pole piece 106B to the second coil 110B at a location along the sensing axis 201 further away from the test mass assembly 204 than the distal end of the second pole piece 106B. For example, the redirection of magnetic flux flow compared to the first magnetic circuit can alter the distribution and density of the magnetic field in the second magnetic circuit, thereby creating a first asymmetry between the first and second magnetic circuits. When the object moves, the first asymmetry can cancel out the second asymmetry between the first and second magnetic circuits caused by changes in the magnet 220, pole shoe 106, capacitor plate 205, non-moving component 108, belt 226, central raised pad 222, and outer raised pad 224 within the accelerometer system 100.

[0054] The cancellation between the first and second asymmetries balances the Lorentz force applied to the capacitor plate 205 and reduces the net change in magnetic flux in the accelerometer system 100. For example, since the redistribution of magnetic flux through the second pole shoe 106B due to feature 240 cancels out other asymmetries within the accelerometer system 100, any loss of the first magnetic flux due to the displacement of the test mass 104 toward the second non-moving member 108B can be canceled out by the gain of the second magnetic flux, and vice versa. Therefore, it is possible that there is essentially no net change in magnetic flux within the accelerometer system 100 due to displacement of the test mass 104 (e.g., due to vibration of the accelerometer system 100 and / or due to torque acting on the test mass 104).

[0055] Although Figure 2Only the second pole shoe 106B is shown as including feature 240, but the first pole shoe 106A may include corresponding features, for example, to guide the flow of a first magnetic flux within the first magnetic circuit. In such examples, the features on the pole shoes 106 may differ (e.g., may define different sizes, may be of different types) to make the shape and / or structure of the first pole shoe 106A different from the shape and / or structure of the second pole shoe 106B, for example, to define an asymmetry between the first and second magnetic circuits.

[0056] Figure 3 It shows Figure 2 A conceptual diagram of the test mass block 104 and pole shoe 106 of the accelerometer system 100. Although Figure 2 Only one of the pole shoes 106 (e.g., the second pole shoe 106B) is shown as including feature 240 and is described herein primarily with reference to that single pole shoe; however, in other example accelerometer systems, each pole shoe may include a corresponding feature. In such examples, the features on the different pole shoes may be asymmetrical, for example, such that the different pole shoes of the example accelerometer system are asymmetrical in shape and / or size. Although Figure 2 This document primarily describes feature 240 as a chamfer on the edge of one of the pole shoes 106, but feature 240 may include, but is not limited to, rounded objects, rounded corners, recesses, passages, protrusions, inserts, or any other feature disposed on or within the pole shoe.

[0057] like Figure 2 As shown, feature 240 may be a chamfer extending around the distal edge of pole shoe 106B. The chamfer may extend from the distal side 302B of pole shoe 106B to the proximal side 303B of pole shoe 106B. In some examples, the chamfer extends partially from the distal side of pole shoe 106B toward the proximal side of pole shoe 106B.

[0058] As described herein, the distal sides 302A, 302B of pole shoes 106 (collectively referred to herein as "distal sides 302") refer to the face of each pole shoe 106 that is relatively closer to the test mass block 104 along the sensing axis 201. As described herein, the proximal sides 303A, 303B of pole shoes 106 (collectively referred to herein as "proximal sides 303") refer to the face of each pole shoe 106 that is relatively further away from the test mass block 104 along the sensing axis 201 (e.g., compared to the distal sides 302). Each distal side of the distal sides 302 may be connected to a corresponding central protrusion pad in the central protrusion pad 222. Each proximal side of the proximal sides 303 may be connected to a corresponding magnet in the magnet 220. For example, the distal side 302B of the second pole shoe 106B may be connected to the central protrusion pad 222B, and the proximal side 303B of the second pole shoe 106B may be connected to the second magnet 220B.

[0059] Feature 240 may be defined by a chamfer angle 304 and a chamfer length 308. The chamfer angle 304 defines the depth of feature 240 along the sensing axis 201. The chamfer angle 304 may be up to 60 degrees (e.g., up to 45 degrees). The chamfer length 308 defines the length of feature 240 along a reference axis orthogonal to the sensing axis 201 (e.g., along a reference axis parallel to the distal side surface 302B of the second pole piece 106B). The chamfer length 308 may be up to 0.6 millimeters (mm) (e.g., up to 0.53 mm, up to 0.595 mm). Feature 240 may be a circumferentially symmetrical or asymmetrical chamfer around the distal side surface 302B.

[0060] Feature 240 can affect the amount of magnetic permeable material at or around the distal side 302B of the second pole piece 106B. For example, as Figure 2 As shown, compared to the near-side 303B, feature 240 causes the second pole shoe 106B to include a reduced amount of magnetic permeable material at or around the far-side 302B. When magnetic flux flows from the magnet 220B through the second pole shoe 106B and into the second coil 110B, the magnetic flux can be concentrated in regions of increased permeability, such as the portion of the second pole shoe 106B without feature 240. Figure 2 In the example shown, the magnetic flux may be concentrated around the proximal edge of the second pole shoe 106B at or around the distal edge, compared to the distal edge at or around the distal side 302B. This is, for example, due to an increase in the permeability of the magnetic material forming the second pole shoe 106B compared to the air surrounding the second pole shoe 106B. In such examples, the distribution of magnetic flux within and / or around the second pole shoe 106B may differ from the distribution of magnetic flux within and / or around the first pole shoe 106A.

[0061] In some examples, with the pole shoes 106 substantially the same, an asymmetry may exist between the first magnetic flux traveling through the first pole shoe 106A and the first coil 110A and the second magnetic flux traveling through the second pole shoe 106B and the second coil 110. For example, the first and second magnetic fluxes may not change by substantially similar amounts in response to movement of the accelerometer system 100. The asymmetry may result from one or more differences between the pole shoes 106, the magnet 220, the coil 110, the non-moving member 108 (not shown), etc. For example, the magnet 220 may have different small hysteresis loop slopes, which may cause the magnet 220 to exhibit different inductions when the accelerometer system 100 inputs current into the coil 110.

[0062] Feature 240 can influence the amount and / or distribution of the magnetic permeable material within the second pole piece 106B to create an asymmetry between the pole pieces 106. This asymmetry between the pole pieces 106 can counteract a pre-existing asymmetry, such that the first flux loop (extending through the first magnet 220A, the first pole piece 106A, and the first coil 110A) is symmetrical to the second flux loop (extending through the second magnet 220B, the second pole piece 106B, and the second coil 110B). This symmetry of the magnetic field promotes the conservation of magnetic flux within the accelerometer system 100 as the test mass 104 moves along the sensing axis 201. For example, feature 240 can promote an equivalent change between the first magnetic flux of the first flux loop and the second magnetic flux of the second flux loop in response to the movement of the test mass 104, such that the net magnetic flux within the accelerometer system 100 remains substantially unchanged. In such examples, the output of the accelerometer system 100 may not be adversely affected by the movement of the test mass 104; for example, the scaling factor of the accelerometer system 100 may not be affected by the movement of the test mass 104.

[0063] Figure 4 It shows Figure 1 A conceptual diagram of a side cross-section of another example of an accelerometer system 100. In addition to feature 402 disposed on one or more non-moving members in non-moving member 108. Figure 4 The example shown is basically similar to Figure 2 Examples are shown and discussed herein. As a supplement to or alternative to feature 240, the accelerometer system 100 may include feature 402. Although feature 402 is discussed herein primarily with reference to the second non-moving member 108B including feature 402, each of the non-moving members 108 may include a corresponding feature 402. In such examples, the different features 402 on different non-moving members 108 may be asymmetrical, for example, such that the non-moving members 108 define different shapes and / or sizes.

[0064] Similar to feature 240, feature 402 removes magnetic material and / or adds magnetic material to non-movable member 108 (e.g., second non-movable member 108B), for example, to regulate the magnetic flux flow from second pole shoe 106B through second coil 110B and into second non-movable member 108. Feature 402 may include one or more of chamfers, fillets, rounded edges, recesses, openings, protrusions, inserts, etc. Figure 4As shown, feature 402 removes material at or near the distal end of the second non-moving member 108B (e.g., one end along the sensing axis 201 near the test mass 104). As magnetic flux flows from the second magnet 220B through the second pole shoe 106B and the second coil 110B, the flux can move away from feature 402 and concentrate towards a more proximal portion of the second non-moving member 108 (e.g., due to increased concentration of magnetic material at or around the more proximal portion). For example, feature 402 thus alters the flow of magnetic flux through the second non-moving member 108B compared to the first non-moving member 108A without feature 402, thereby creating an asymmetry in the magnetic field on the opposite side of the test mass 104. This asymmetry can counteract pre-existing symmetries in the accelerometer system 100 (e.g., due to variations in the pole shoe 106, non-moving member 108, coil 110, and / or magnet 220), thus creating an overall symmetry in the magnetic field within the accelerometer system 100.

[0065] Compared to feature 240, feature 402 may alter the amount of magnetically permeable material within the second non-movable member 108 to achieve the same redistribution of magnetic flux. For example, feature 402 may define a larger chamfer angle and / or chamfer length than feature 240, and / or remove material with a larger mass and / or volume than feature 240 to achieve the same redistribution of magnetic flux within the accelerometer system 100. The difference between feature 240 and feature 402 may be attributed to (but not limited to) an increase in the strength of the magnetic field at locations around the pole shoe 106 and / or magnet 220 compared to locations radially further away from the pole shoe 106 and / or magnet 220.

[0066] Figure 5 This is a flowchart illustrating an example operation for determining acceleration using an electromagnetic accelerometer according to one or more techniques of this disclosure. Relative to Figure 1 100 pairs of accelerometer systems Figure 5 To describe. However, Figure 5 The technology can be performed by different components of the accelerometer system 100 or by additional or alternative devices.

[0067] The processing circuit 102 can receive a first capacitance signal (502) indicating the capacitance value from the first sensor 112A. In some examples, the first sensor 112A may represent a first capacitor plate located on a first side of the inspection mass block 104 (e.g., Figure 2The first capacitor plate 205A). The processing circuit 102 can generate an electrical signal based on the capacitance signal to include a current value (504) that holds the test mass block 104 at zero. The processing circuit 102 can transmit the electrical signal to the first coil 110A (506). In some examples, the processing circuit 102 can transmit the electrical signal to the first coil 110A such that the first coil 110A applies a Lorentz force to the test mass block 104, thereby counteracting the acceleration force applied to the test mass block 104.

[0068] Processing circuit 102 can determine the current value corresponding to the electrical signal (508). Subsequently, processing circuit 102 can identify the acceleration of accelerometer system 100 based on the current value (510). In other words, the strength of the electrical signal required to keep the test mass 104 at zero position is correlated with the acceleration of accelerometer system 100 along the sensing axis.

[0069] Figure 6 It shows the manufacturing process. Figure 1 A flowchart illustrating an example technology for electromagnetic accelerometers. This is in contrast to, for example, forming via the fabrication of components. Figure 1 The accelerometer system 100 is used to describe Figure 6 .However, Figure 6 The technology can be performed by manufacturing components to form any of the alternative devices described herein, including the components and / or alternative devices. Figure 6 The technology can be performed by manufacturing components (e.g., automated and / or semi-automated manufacturing components) and / or one or more manufacturers.

[0070] The manufacturing components can determine the Lorentz force (602) generated by each coil of the coils 110 of the accelerometer system 100 in response to the motion of the test mass 104. The accelerometer system 100 can generate two separate magnetic fields, each applying a Lorentz force to the test mass 104. For example, a first flux loop formed by a first magnet 220A, a first pole shoe 106A, a first coil 110, and a first non-moving member 108 can apply a first Lorentz force to the test mass 104 in a first direction along the sensing axis 201, and a second flux loop formed by a second magnet 220B, a second pole shoe 106B, a second coil 110B, and a second non-moving member 108 can apply a second Lorentz force to the test mass 104 in a second direction along the sensing axis 201. In such examples, the Lorentz force can act in opposite directions to inhibit movement of the test mass 104 along the sensing axis 201. As the inspection mass 104 moves along the sensing axis 201, the magnitude of a Lorentz force can decrease, while the magnitude of an opposite Lorentz force can increase to hold the inspection mass 104 at a zero position and allow the processing circuit 102 to sense the electrical signal required to maintain the inspection mass. The manufacturing assembly can simulate the movement of the inspection mass 104 from the zero position and determine the magnitude of the Lorentz force acting on the inspection mass 104 in response to the movement.

[0071] The manufacturing component can determine the magnetic flux value (604) corresponding to the Lorentz force. When the manufacturing component simulates the movement of the test mass 104, it can determine the change in the Lorentz force caused by the simulated movement. The manufacturing component can determine the change in magnetic flux caused by the simulated movement based on the change in the Lorentz force.

[0072] The manufacturing components can determine whether the magnitude difference between the changes in magnetic flux in the two flux loops is less than or equal to a threshold (606). In a balanced accelerometer system 100 in which the first and second flux loops are symmetrical, the net magnetic flux within the accelerometer system 100 may remain substantially unchanged when the test mass 104 moves along the sensing axis 201. For example, in a balanced accelerometer system 100, when the test mass 104 moves toward the first flux loop and away from the second flux loop, the increase in the first magnetic flux may be substantially similar to the decrease in the second magnetic flux, and vice versa. Minimal change in net magnetic flux can isolate the output of the accelerometer system 100 from the movement of the test mass 104, thereby improving the accuracy of the output. The manufacturing components can identify the presence and magnitude of an imbalance based on the difference in the magnitude of the changes in the first and second magnetic flux in response to the movement of the test mass 104. For example, the manufacturing components can determine whether the first and second magnetic fluxes change by the same amount for the same movement of the test mass 104. The manufacturing process can compare the difference in the amount of variation with a threshold. The threshold can be as high as 0.08 Tesla (e.g., as high as 0.077 Tesla).

[0073] Based on the determination that the difference is less than or equal to a threshold (the "yes" branch of 606), the manufacturing component can complete the assembly of the accelerometer system 100 (610). The manufacturing component can determine that the first flux loop and the second flux loop are balanced and complete the assembly and / or testing of the accelerometer system 100.

[0074] Based on the determination that the difference is greater than a threshold (the "No" branch of 606), the manufacturing component can adjust one or more features (608) on one or more of the pole shoes 106 and / or one or more non-moving members 108 of the accelerometer system. The manufacturing component can form features 240 and / or 402 respectively on one or more pole shoes 106 and / or one or more non-moving members 108. Features 240 and / or 402 can create asymmetry in the shape and size of the pole shoes 106 and / or non-moving members 108 of different flux loops, thereby creating asymmetry between flux loops. The asymmetry formed by features 240 and / or 402 can counteract asymmetry identified by the manufacturing component, for example, from the magnetic flux of the flux loops, to balance the first flux loop with the second flux loop.

[0075] After forming and / or adjusting one or more features, the manufacturing component may perform each of steps 602 to 606 to determine whether the one or more features achieve a balance between the first and second flux loops. The manufacturing component may iteratively perform steps 602 to 608 until the manufacturing component determines that the flux loops are balanced (i.e., the "yes" branch of 606).

[0076] This disclosure describes the following embodiments:

[0077] Example 1: An accelerometer system comprising: a first magnetic assembly including a first pole shoe, a first excitation ring, and a first magnet configured to generate a first magnetic flux; a second magnetic assembly including a second pole shoe, a second excitation ring, and a second magnet configured to generate a second magnetic flux, wherein the physical shape of the second pole shoe differs from that of the first pole shoe; a test mass assembly including a test mass between the first and second magnetic assemblies; and a first coil disposed around the first pole shoe, wherein the first magnetic flux passes through the first excitation ring. The first magnetic flux flows through the first coil to the first pole shoe, and the magnitude of the first magnetic flux through the first coil is based on the physical shape of the first pole shoe; a second coil is arranged around the second pole shoe, and the second magnetic flux flows from the second excitation ring through the second coil to the second pole shoe, and the magnitude of the second magnetic flux through the second coil is based on the physical shape of the second pole shoe; and a processing circuit configured to: allow a first current to flow through the first coil to apply a first Lorentz force to the test mass block; and allow a second current to flow through the second coil to apply a second Lorentz force to the test mass block.

[0078] Example 2: The accelerometer system according to Example 1, wherein the physical shape of the first pole piece includes a first elongated body, and wherein the physical shape of the second pole piece includes a second elongated body having a chamfer around the outer periphery of the second elongated body.

[0079] Example 3: An accelerometer system according to Example 2, wherein the accelerometer system defines a longitudinal axis extending through the first magnetic component, the second magnetic component, and the test mass assembly, and wherein the second elongated body extends from a first end to a second end along the longitudinal axis, wherein the first end of the second elongated body is fixed to the second magnet, wherein the second end of the second elongated body is longitudinally disposed between the first end of the second elongated body and the test mass, and wherein the chamfer extends around the outer periphery of the second end of the second elongated body.

[0080] Example 4: An accelerometer system according to any one of Examples 2 or 3, wherein the chamfer is defined to a depth of up to 0.5 mm.

[0081] Example 5: An accelerometer system according to any one of Examples 2 to 4, wherein the chamfer includes a first chamfer, and wherein the first elongated body defines a second chamfer around the outer periphery of the first elongated body, the second chamfer defining a different depth than the first chamfer.

[0082] Example 6: An accelerometer system according to any one of Examples 2 to 5, wherein the first elongated body defines a first cylinder, wherein the second elongated body defines a second cylinder, and wherein the outer periphery of the second elongated body includes the outer circumference of the second cylinder.

[0083] Example 7: An accelerometer system according to any one of Examples 1 to 6, wherein the different physical shapes of the first pole piece and the second pole piece are configured to reduce the net change in magnetic flux generated in the accelerometer system in response to the movement of the test mass within the accelerometer system.

[0084] Example 8: The accelerometer system according to Example 7, wherein the net change in magnetic flux within the accelerometer system includes the sum of an increase in one of the first magnetic flux or the second magnetic flux in response to the movement of the test mass and a decrease in the other of the first magnetic flux or the second magnetic flux.

[0085] Example 9: An accelerometer system according to any one of Examples 1 to 8, wherein the different physical shapes of the first pole shoe and the second pole shoe reduce the asymmetry between the change in the first Lorentz force and the change in the second Lorentz force in response to the movement of the test mass within the accelerometer system.

[0086] Example 10: An accelerometer system comprising: a first magnetic assembly including a first pole shoe, a first excitation ring, and a first magnet configured to generate a first magnetic flux; a second magnetic assembly including a second pole shoe, a second excitation ring, and a second magnet configured to generate a second magnetic flux; a test mass assembly including: a test mass between the first and second magnetic assemblies; and a first coil disposed around the first pole shoe, wherein the first magnetic flux flows from the first excitation ring through the first coil to the first pole shoe, and wherein the first magnetic flux passing through the first coil... The quantity is based on the physical shape of the first pole shoe; and a second coil, the second coil being disposed around the second pole shoe, wherein the second magnetic flux flows from the second excitation ring through the second coil to the second pole shoe, and wherein the quantity of the second magnetic flux through the second coil is based on the physical shape of the second pole shoe; and a processing circuit configured to: allow a first current to flow through the first coil to apply a first Lorentz force to the test mass block; and allow a second current to flow through the second coil to apply a second Lorentz force to the test mass block, wherein at least one of the first pole shoe or the second pole shoe defines a chamfer extending around the outer periphery of the at least one pole shoe.

[0087] Example 11: An accelerometer system according to Example 10, wherein the accelerometer system defines a longitudinal axis extending through the first magnetic assembly, the second magnetic assembly and the test mass assembly, and wherein the at least one pole shoe extends along the longitudinal axis from a first end to a second end, wherein the second end is longitudinally disposed between the first end and the test mass, and wherein the chamfer extends around the outer periphery of the second end of the at least one pole shoe.

[0088] Example 12: An accelerometer system according to any one of Examples 10 or 11, wherein the chamfer is defined to a depth of up to 0.5 millimeters (mm).

[0089] Example 13: An accelerometer system according to any one of Examples 10 to 12, wherein the first pole piece includes a first cylinder, and wherein the second pole piece includes a second cylinder.

[0090] Example 14: An accelerometer system according to any one of Examples 10 to 13, wherein the chamfer extending around the outer periphery of the at least one pole shoe is configured to reduce the net change in magnetic flux generated in the accelerometer system in response to movement of the test mass within the accelerometer system.

[0091] Example 15: The accelerometer system according to Example 14, wherein the net change in magnetic flux within the accelerometer system includes the sum of an increase in one of the first magnetic flux or the second magnetic flux in response to the movement of the test mass and a decrease in the other of the first magnetic flux or the second magnetic flux.

[0092] Example 16: An accelerometer system according to any one of Examples 10 to 15, wherein the chamfer extending around the outer periphery of the at least one pole shoe is configured to reduce the asymmetry between the change in the first Lorentz force and the change in the second Lorentz force in response to the movement of the test mass within the accelerometer system.

[0093] Example 17: An accelerometer system comprising: a first magnetic assembly including a first pole shoe, a first excitation ring, and a first magnet configured to generate a first magnetic flux; a second magnetic assembly including a second pole shoe, a second excitation ring, and a second magnet configured to generate a second magnetic flux, wherein the physical shape of the second excitation ring is different from the physical shape of the first excitation ring; a test mass assembly including: a test mass between the first and second magnetic assemblies; and a first coil disposed around the first pole shoe, wherein the first magnetic flux passes through the first excitation ring. The first magnetic flux flows through the first coil to the first pole shoe, and the magnitude of the first magnetic flux passing through the first coil is based on the physical shape of the first excitation ring; a second coil is arranged around the second pole shoe, and the second magnetic flux flows from the second excitation ring through the second coil to the second pole shoe, and the magnitude of the second magnetic flux passing through the second coil is based on the physical shape of the second excitation ring; and a processing circuit is configured to: allow a first current to flow through the first coil to apply a first Lorentz force to the test mass block; and allow a second current to flow through the second coil to apply a second Lorentz force to the test mass block.

[0094] Example 18: The accelerometer system according to Example 17, wherein the physical shape of the first excitation ring includes a first elongated body, and wherein the physical shape of the second excitation ring includes a second elongated body having a chamfer around the outer periphery of the second elongated body.

[0095] Example 19: An accelerometer system according to any one of Examples 17 or 18, wherein the different physical shapes of the first excitation ring and the second excitation ring are configured to reduce the net change in magnetic flux generated in the accelerometer system in response to the movement of the test mass block within the accelerometer system.

[0096] Example 20: An accelerometer system according to any one of Examples 17 to 19, wherein the different physical shapes of the first excitation ring and the second excitation ring are configured to reduce the asymmetry between the change in the first Lorentz force and the change in the second Lorentz force in response to the movement of the test mass block within the accelerometer system.

[0097] In one or more examples, the accelerometer described herein may implement the functions using hardware, software, firmware, or any combination thereof. Those functions implemented in software may be stored as one or more instructions or code on or transmitted via a computer-readable medium and executed by a hardware-based processing unit. The computer-readable medium may include a computer-readable storage medium corresponding to a tangible medium such as a data storage medium, or a communication medium that includes, for example, any medium facilitating the transfer of a computer program from one place to another according to a communication protocol. Thus, a computer-readable medium may generally correspond to: (1) a non-transitory tangible computer-readable storage medium, or (2) a communication medium such as a signal or carrier wave. The data storage medium may be any available medium accessible by one or more computers or one or more processors to retrieve instructions, code, and / or data structures for implementing the techniques described herein.

[0098] Instructions may be executed by or communicatively coupled to one or more processors within the accelerometer. These processors may, for example, include one or more DSPs, general-purpose microprocessors, application-specific integrated circuits (ASICs), FPGAs, or other equivalent integrated or discrete logic circuits. Therefore, the term "processor" as used herein may refer to any of the foregoing structures or any other structure suitable for implementing the techniques described herein. Furthermore, in some aspects, the functions described herein may be provided within dedicated hardware and / or software modules configured to perform the techniques described herein. Moreover, these techniques may be implemented entirely within one or more circuit or logic elements.

[0099] The techniques disclosed herein can be implemented in various devices or apparatuses including integrated circuits (ICs) or a set of ICs (e.g., chipsets). Various components, modules, or units are described in this disclosure to emphasize functional aspects of a device configured to perform the disclosed techniques, but they do not necessarily need to be implemented by different hardware units. Instead, various units may be combined with or provided by a collection of interoperable hardware units (including one or more processors as described above) incorporating suitable software and / or firmware.

Claims

1. An accelerometer system, the accelerometer system comprising: A first magnetic assembly, the first magnetic assembly including a first pole shoe, a first excitation ring and a first magnet configured to generate a first magnetic flux; The second magnetic assembly includes a second pole shoe, a second excitation ring, and a second magnet configured to generate a second magnetic flux, wherein the physical shape of the second pole shoe is different from the physical shape of the first pole shoe. Inspection quality block assembly, the inspection quality block assembly comprising: An inspection mass block is located between the first magnetic assembly and the second magnetic assembly; A first coil, the first coil being disposed around a first pole shoe, wherein a first magnetic flux flows from a first excitation ring through the first coil to the first pole shoe, and wherein the magnitude of the first magnetic flux through the first coil is based on the physical shape of the first pole shoe; and A second coil, the second coil being arranged around the second pole shoe, wherein a second magnetic flux flows from the second excitation ring through the second coil to the second pole shoe, and wherein the magnitude of the second magnetic flux through the second coil is based on the physical shape of the second pole shoe; and Processing circuit, the processing circuit being configured to: A first current flows through the first coil to apply a first Lorentz force to the test mass block; and A second current is made to flow through the second coil to apply a second Lorentz force to the test mass block.

2. The accelerometer system of claim 1, wherein the physical shape of the first pole shoe includes a first elongated body, and wherein the physical shape of the second pole shoe includes a second elongated body having a chamfer around the outer periphery of the second elongated body.

3. The accelerometer system according to claim 2, The accelerometer system defines a longitudinal axis extending through the first magnetic assembly, the second magnetic assembly, and the test mass assembly, and The second elongated body extends from the first end to the second end along the longitudinal axis, wherein the first end of the second elongated body is fixed to the second magnet, wherein the second end of the second elongated body is longitudinally disposed between the first end of the second elongated body and the inspection mass block, and wherein the chamfer extends around the outer periphery of the second end of the second elongated body.

4. The accelerometer system according to any one of claims 2 and 3, wherein the chamfer is defined to a depth of up to 0.5 mm.

5. The accelerometer system according to any one of claims 2 to 4, wherein the chamfer includes a first chamfer, and wherein the first elongated body defines a second chamfer around the outer periphery of the first elongated body, the second chamfer defining a different depth than the first chamfer.

6. The accelerometer system according to any one of claims 2 to 5, wherein the first elongated body defines a first cylinder, wherein the second elongated body defines a second cylinder, and wherein the outer periphery of the second elongated body includes the outer circumference of the second cylinder.

7. The accelerometer system according to any one of claims 1 to 6, wherein the different physical shapes of the first pole shoe and the second pole shoe are configured to reduce the net change in magnetic flux generated within the accelerometer system in response to movement of the test mass within the accelerometer system.

8. The accelerometer system of claim 7, wherein the net change in magnetic flux within the accelerometer system comprises the sum of an increase in one of the first magnetic flux or the second magnetic flux in response to the movement of the test mass and a decrease in the other of the first magnetic flux or the second magnetic flux.

9. The accelerometer system according to any one of claims 1 to 8, wherein the different physical shapes of the first pole shoe and the second pole shoe reduce the asymmetry between the change in the first Lorentz force and the change in the second Lorentz force in response to the movement of the test mass within the accelerometer system.

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