JP7126645B1 - Magnet position/direction detector - Google Patents

Abstract

An object of the present invention is to develop a magnetic field vector sensor grid using a GSR sensor and to enable detection of the position and orientation of a micro-magnet. A magnetic field vector sensor and a magnetic field vector sensor grid having a detection power of 10 nT or less are developed to measure the magnetic field generated by a magnet body. It consists of a device that detects the position and orientation of a magnet with high accuracy by appropriately selecting and inputting it. [Selection drawing] Fig. 14

Description

TECHNICAL FIELD The present invention relates to a detection apparatus that has a micromagnet at the tip of a microobject and measures the position and orientation of the microobject in real time with high accuracy.

In the medical field, it is used to measure the position and orientation of detection objects at the tip of endoscopes and catheters. And there is a growing need to accurately measure the azimuth and the amount of rotation.
A system has been developed in which a magnetic field vector sensor is attached to a detection object and a magnetic field is applied from the outside, and the position is calculated by measuring the external magnetic field with the magnetic field vector sensor, and a system in which a magnet is attached to the detection object and the position is measured. .

The method of detecting the position and orientation by providing a magnet to the detection body is simple, but the precision decreases when the magnet body is made smaller. Since only a small magnet with a diameter of about 0.3 to 2 mm can be used as the magnet, a magnetic field vector sensor is required that can measure the minute magnetic field generated by the magnet from the outside with high sensitivity. A magnetic field vector sensor grid with high density magnetic field vector sensors and position/direction calculation program technology are required. Only inferior ones have been developed. In addition, the position and orientation measurement speed of existing products is less than 1 Hz, and significant improvement is required.

Patent Document 1 discloses a magnet type position/orientation calculation system. It consists of NdFeB magnets (three magnets of size 0.8 mm × 2.5 mm) having a magnetic moment of about 4.8 × 10 ^-9 Wbm and an FG sensor having a magnetic field detection power of about 1 nT. Using a 3-axis magnetic field sensor, the position of the magnet can be measured with an accuracy of about 4 mm. The performance is significantly inferior to the positional accuracy of 0.5 mm or less required for the tip of the catheter.

The main reason for this is considered to be the mutual displacement of the positions of the measured values of the three-axis magnetic field sensors. Although not precisely described in Patent Document 1, assuming that the diameter of the magnetic field sensor described in FIG. This is considered to be the cause of the great loss of positional accuracy.
Also, since this invention does not use a magnetic field vector sensor, it cannot be calculated according to the Gauss-Newton method, so an iterative process utilizing magnetic field gradients is performed to minimize the error between the measured and theoretical values. , Y, Z, θ, and φ are obtained, but the calculation speed is slow due to the iterative process, and real-time performance seems to be a problem. In fact, the patent document 1 does not describe the position measurement speed.

As a three-axis magnetic field sensor, Patent Document 2 describes an electronic compass manufactured by Aichi Steel Co., Ltd. as a type using an MI sensor. This is an assembly of three elements, and the measurement positions of the magnetic fields in the X-axis, Y-axis, and Z-axis directions are different by about 1 mm, and the magnetic field vector at a predetermined position cannot be measured with pinpoint accuracy. Also, the magnetic field detection power is as low as 200 nT. Therefore, even if this electronic compass is applied to the invention of Patent Document 1, improvement in the positional accuracy of the magnet cannot be expected. In order to improve the positional accuracy, it is important to use a magnetic field vector sensor capable of pinpoint magnetic field vector measurement using a three-dimensional magnetic field sensor instead of a three-axis magnetic field sensor.

As a magnetic field vector sensor, Patent Document 3 describes an electronic compass manufactured by Asahi Kasei Corporation as a magnetic field measuring device using a Hall sensor. It is a combination of four Hall elements and one permalloy magnetic collector, and the sensor element spacing is about 1 mm, and it is possible to measure the magnetic field vector at a pinpoint predetermined position. Although it is possible to fabricate a sensor grid arranged at a high density, there is a problem that the magnetic field detection capability is only about 10 mG (=1000 nT), and minute magnetic fields cannot be measured.

As a magnetic field vector sensor, Patent Document 4 describes an integrated magnetometer using a GMR sensor. It has a small size of 2 mm x 2 mm, a detection power of about 500 nT, and a problem that the measurement accuracy of Hx and Hy differs from that of Hz. As a result, there is a problem that a minute magnetic field cannot be measured.

As a magnetic field vector sensor, Non-Patent Document 1 describes an nT meter manufactured by MTI using an FG sensor. Although the detection power is at the level of 1 nT, the elements are attached to the six sides of a 30 mm cube. For this reason, the distance between the sensor elements is about 30 mm, and when measuring the magnetic field vector with a large gradient created by the mini-magnet, the magnetic field gradient is measured, and it is not possible to pinpoint the magnetic field measurement at a specific position. . In addition, there is also the drawback that it is not possible to manufacture a sensor grid in which the sensor intervals are arranged at high density.

On the other hand, Patent Document 6 describes an electronic compass manufactured by Magnedesign Co., Ltd. using a GSR sensor (Patent Document 5). It is a combination of four GSR elements and a pair of permalloy magnetic collectors. The distance between the GSR elements is about 0.5 mm, and it is possible to measure the magnetic field vector at a pinpoint predetermined position. there is However. This is insufficient when compared with the required magnetic field detection force of 10 nT or less. If this product is applied to the invention of Patent Document 1, an improvement in the positional accuracy of the magnet can be expected, but the limit seems to be about 1.5 mm. Since it is an iterative process method, the localization speed must be less than 1 Hz.

In order to accurately and quickly measure the position and orientation of a small magnet placed on a detection object, it is necessary to develop a compact magnetic field vector sensor with high magnetic field detection capability. Specifically, it is possible to measure a magnetic field vector at a pinpoint predetermined position in a minute space of 6 mm × 6 mm × 3 mm or less with a detectability of a minute magnetic field of 10 nT or less, and the accuracy of the measured values of Hx, Hy, and Hz is high. There is a need to develop magnetic field vector sensors that are the same.

Gauss-Newton's method is widely known as a method of simultaneously determining the position and orientation of a magnet using a magnetic field vector sensor grid. Non-Patent Document 2 describes a method of defining an error function and finding three coordinate components X, Y, and Z that minimize the error function. However, it does not describe how to obtain .theta. and .phi., and does not describe how to obtain the three coordinate components X, Y and Z and the directions .theta. and .phi. from the error function.
Strictly speaking, the magnetic field vector sensor described in Non-Patent Document 2 has a deviation of 1.8 mm between the measurement positions of the three-axis sensor. The measurement position error is as large as 5.5 mm, which is not of a practical level.

Theoretically, the accuracy of position and orientation calculations depends on the strength of the magnet, the detection power of the magnetic field vector sensor, the distance between the magnet body and the sensor grid, and the like. It also depends on the density, number and area size of the magnetic field vector sensor grid, and the assembly accuracy of the sensor grid. Furthermore, it depends on the method of acquiring and selecting data used for calculation, the algorithm of the calculation program, and the method of data processing. Based on these well-known techniques, improvements in the accuracy of the calculation of the position and orientation of the magnet have been pursued.

However, all of the conventional inventions actually use a magnetic field vector sensor with a deviation of about 1 mm to 2 mm in the measurement position of each axis, or use a sensor with a very low detection power of 100 nT level. Positional accuracy is only about 3 mm to 5 mm. The inventors of the present invention have realized that it is a major premise to use a magnetic field vector sensor that has excellent detection power and can measure the magnetic field vector at a pinpoint position. I decided to pursue development.
The size of the micro magnet (mini ^magnet ) is ^0.3 to 2 mm in diameter and 1 to 15 mm in length. The area of the grid is a square with a side of 40 to 200 mm, which is sufficiently wide, and the distance between the magnet body and the magnetic field vector sensor grid is 20 to 100 mm, which is sufficient. and the Gauss-Newton method, the positional accuracy of the magnet body is improved from the conventional 5 mm to 0.5 mm or less, and the azimuth accuracy of 1 degree or less and the measurement speed of 1 Hz to 50 Hz can be realized. I decided to aim to invent a position and orientation detection system for

Japanese Patent Publication No. 2001-524012 Japanese Patent No. 3781056 Japanese Patent Application Laid-Open No. 2004-61380 Japanese Patent Publication No. 2013-518273 Japanese Patent No. 6506466 Japanese Patent No. 6021239

MTI Co., Ltd. Website Product information FGS3-1000 Takashi Nagaoka, Akihiko Uchiyama: Tateishi Foundation for the Promotion of Science and Technology Grant Research Results: No. 15, pp. 52-55 (2006)

Based on the principle technology related to the position and orientation calculation system of the magnetic body which has already been developed,
An object of the present invention is to greatly improve the position and orientation accuracy and the measurement speed of minute magnets.

The first technical development task for this purpose is the development of a magnetic field vector sensor with a detection power of 0.1 nT to 10 nT. A GSR sensor has been developed as a compact magnetic field sensor capable of detecting minute magnetic fields. The object is to devise a magnetic field vector sensor structure that can make the measurement error of Hz the same.

A second challenge is the design of a well-designed magnetic field vector sensor grid. As the density of the sensor grid increases, the accuracy of the position and orientation calculations improves, but the measurement accuracy of points far from the magnet drops significantly. Accuracy is reduced. Also, as the number of sensors increases, the control speed of the electronic circuit and the calculation speed of position and orientation decrease, so it is necessary to optimize the size and density of the sensor grid.

The third task is to devise a calculation program based on the Gauss-Newton method to calculate the position and orientation of the magnet with high precision and excellent real-time performance. In the magnetic field vector sensor grid, when the magnetic field vector emitted by the magnet is measured as the magnetic field vector at each measurement point, no iterative process is required. and calculating X, Y, Z and θ, φ from its minimum value is widely known as the Gauss-Newton method.
Theoretically, the more measurements you use in your calculations, the more accurate your calculations will be. However, in the present invention, since the magnet is small and the magnetic field generated by the magnet is weak, the more the measurement position is away from the position of the magnet, the greater the error in the measured value. Including such measured values in the calculation would adversely reduce the accuracy of the calculation. In the present invention, the area area of the grid and the sensor density are devised, and only the measured values with small errors are selected to ensure calculation accuracy.

The present invention comprises a magnet, a magnetic field vector sensor, a magnetic field vector sensor grid, a sensor grid data processing circuit, a position and orientation calculation program, and a position and orientation calculation device incorporating it. Therefore, the present inventor first worked on the development of a magnetic field vector sensor having high detection power, which is the first problem.

Focusing on the GSR sensor, the present inventor succeeded in developing a magnetic field vector sensor with a magnetic field detection power of 10 nT or less and a size of 6 mm x 6 mm x 3 mm or less, which is ultra-compact and excellent in magnetic field detection power.

A GSR sensor is described in detail in US Pat. As shown in FIG. 1, the GSR sensor consists of a detection coil formed of a magnetic field detection magnetic wire having conductivity on a substrate, a circulating coil wound around the wire, two electrodes for wire conduction, and an electrode for detecting coil voltage. Means for applying a pulse current having a frequency of GHz to the GSR element composed of wiring connecting two electrodes and its magnetic wire, and detecting the coil voltage generated when the pulse current is applied, and applying the coil voltage to the external magnetic field H. It is an ultra-sensitive micro magnetic field sensor consisting of a converting electronic circuit.

The detection power of the GSR sensor increases in proportion to the length of the magnetic wire. In order to measure a minute magnetic field of 10 nT or less in a minute space range, the inventor manufactured and used a small GSR element with a length of 0.4 to 3 mm and a width of 0.2 to 0.4 mm. It was to be.

As the electronic circuit, the electronic circuit of the GSR sensor shown in FIG. 2 was adopted, and an application specific integrated circuit (hereinafter referred to as ASIC) was produced and used in the present invention. As a result, the detectability of the GSR sensor was in the range of 0.1-10 nT.

As shown in FIGS. 3 and 4, the magnetic field vector sensor element is obtained by attaching GSR elements to four slopes of a truncated quadrangular pyramid in four-fold symmetry and mirror symmetry. As for the size, the length of one side of the square on the upper surface corresponds to the width of the GSR element, and is 0.2 to 0.4 mm. The base corresponds to 2 cos θ times the length of the GSR element plus the length of one side of the square on the upper surface, and ranges from 0.6 mm at minimum to 6 mm at maximum. The height of the pedestal is sin θ times the length of the GSR element. The inclination angle θ was set to 20 degrees to 45 degrees.

A magnetic field vector sensor element was fabricated by attaching four of these GSR elements to the slope of a truncated quadrangular pyramid having an inclination angle θ in four-fold symmetry and mirror symmetry. The output voltages of the four elements are processed by the electronic circuit shown in FIG. Calculate (Hx1-Hx2), Hy = (1/2 cos θ) (Hy1-Hy2), Sensor Hz = (1/4 sin θ) (Hx1 + Hx + Hy1 + Hy), magnetic field (Hx, Hy, Hz) at the measurement position can be asked for.

When the tilt angle θ is 35.2 degrees (tan θ = 1/√2, sin θ = 1/√3, cos θ = √2/√3), Hx = √6/4 (Hx1-Hx2), Hy = √6 /4(Hx1-Hx2), Hz=√3/4(Hx1+Hx+Hy1+Hy). At this time, the measurement errors σx, σy, and σz of Hx, Hy, and Hz are all the same, that is, σx=σy=σz=0.86σ, so this is the most recommended angle. Practically, if σz is allowed to differ by about 25% from σx (=σy), then θ is about 20 degrees to 45 degrees. When emphasizing the accuracy of the magnetic field in the horizontal direction, it is slightly reduced from 35.2 degrees to about 20 degrees. be able to.

To assemble the magnetic field vector sensor, as shown in FIG. 6, a magnetic field sensor element assembled with four GSR elements is placed on a sensor substrate, and the electrodes of the magnetic field sensor element and the electrodes of the sensor substrate are connected and wired.
Further, three parts were assembled: a magnetic field sensor element assembled with ASIC and four GSR elements, and a sensor substrate on which these elements were mounted.
Assuming that the electronic circuit is an ASIC, a surface wiring diagram of the ASIC is shown in FIG. FIG. 8 shows a surface wiring diagram of the sensor substrate.
The wiring connects the four electrodes of each element and the 16 element electrodes on the substrate surface with conducting wires. The 16 ASIC element electrodes on the sensor substrate and the element electrodes on the ASIC side are soldered. Further, the external connection electrodes on the ASIC side and the external connection electrodes on the surface side of the sensor substrate are soldered.

When the bottom side of the element pedestal was sufficiently larger than the ASIC, that is, when the base was 2 mm or more, the central portion of the bottom side was made hollow, the ASIC was attached there, and both were placed on the sensor substrate. When the base is 2 mm or less, the back surface of the ASIC is attached directly to the bottom of the truncated quadrangular pyramid-shaped magnetic field sensor element.

FIG. 9 shows an assembly drawing of a magnetic field vector sensor in which a magnetic field sensor element, an ASIC, and a sensor substrate are combined. The sensor substrate has 16 element electrodes, 16 ASIC element electrodes, and a plurality of external connection electrodes on the front side. It has a wiring structure connected to the connection electrode.
As a result, the external magnetic field detected by the element is processed by the ASIC to obtain the magnetic field vector (Hx, Hy, Hz), which can be extracted from the external connection electrodes on the back side of the sensor substrate.

The coupling between the GSR element and the ASIC is achieved by forming the GSR element on the surface of the special ASIC, attaching four GSR sensors to the slope of the truncated square pyramid in mirror symmetry with four rotational symmetry, and forming the magnetic field vector sensor element. It can be made and used.

In the present invention, when a single GSR element is installed on a slope and the coil voltage is wired to the ASIC, the coil voltage may drop or external noise may be felt. In such a case, a GSR element may be formed directly on an integrated circuit ASIC to form a GSR sensor (referred to as an on-ASIC type GSR), and attached to the slope of a quadrangular pyramid to form a magnetic field vector sensor. good. Note that the on-ASIC type GSR sensor is disclosed by the present inventor in Japanese Patent Laid-Open No. 2019-191016.

As for the design of the magnetic field vector sensor grid, which is the second issue, the area area should be a square of 40 mm to 200 mm in consideration of the measurement site. It can also be rectangular depending on the measurement site. Based on this assumption, the design factor that most affects accuracy in design is the effect of the magnetic field vector sensor spacing of the magnetic field vector sensor grid. At least 25 magnetic field vector sensors were arranged on the sensor grid substrate at intervals of 5 to 15 mm.

Therefore, as a result of investigating the effect of the magnetic field vector sensor spacing on the magnetic field vector sensor grid using a position and orientation calculation program to be described later, as shown in FIG. An improvement in the positional accuracy of about double was observed. As for the azimuth accuracy, as shown in FIG. 13(b), when the interval between the magnetic field vector sensors was reduced to 1/2, the azimuth accuracy was improved by about two times. The investigation conditions are that the magnetic field vector sensor has a detection power of 1 nT, a magnetic moment of 50×10 ⁻¹⁰ Wbm, and a distance of 40 mm between the magnetic field vector sensor grid and the magnet body.

However, since the detection power of the magnetic field vector sensor decreases as the size of the magnetic field vector sensor decreases, there is a trade-off relationship between the space between the magnetic field vector sensors and the size of the magnetic field vector sensor. In order to obtain a position accuracy of 0.5 mm or less and an orientation accuracy of 1 degree or less, the interval between the magnetic field vector sensors is set to 2 mm or more and 10 mm or less. Given the performance of the current GSR sensor, the spacing is preferably 4-8 mm.

A combination of the magnetic moment, the detection power of the sensor, and the pixel size of the grid is basically used in an appropriate combination to obtain a position accuracy of 0.5 mm or less. Alternatively, if the required value is 0.1 mm or less, which is stricter than 0.5 mm, it is necessary to further optimize the combination. Conversely, the present invention can also be used in the case of specifications with slightly higher positional accuracy, for example, 1 mm or less.

A magnetic field vector sensor grid was fabricated using the above magnetic field vector sensor. The substrate of the magnetic field vector sensor grid was made in a square with a side of 40 mm to 200 mm. It should be noted that the magnetic field vector sensor grid substrate of the present invention is not limited to this size and shape. The spacing of the magnetic field vector sensors of the magnetic field vector sensor grid was set to 2 to 10 mm. If the area of the magnetic field vector sensor grid is small, it is possible to determine the position and orientation with sufficient accuracy by arranging at least 25 magnetic field vector sensors.

The magnetic field vector sensor grid board is coupled column by column with a multiplexer MUX, as shown in FIG. 10, and all subsequent data is coupled with the final MUX and transferred to external signal processing circuitry. Although not shown, power supply wiring VDD and ground wiring GND are connected to each sensor so that power can be supplied to all the magnetic field vector sensors when the sensor grid is in operation.
The assembly accuracy of the magnetic field vector sensor grid is required to be as small as possible, preferably 10 μm or less.

The Gauss-Newton method is known for the principle of calculating the position and orientation using the magnetic field vector sensor grid, which is the third problem. In Non-Patent Document 2, according to the _Gauss -Newton method, the error function E Create _ij = Σ(ε _ij ) ² , partially differentiate it with respect to magnet positions X, Y, Z and magnet orientations θ and φ to find simultaneous equations, and calculate the value that minimizes the error function. It is known to calculate and obtain the measured positions X, Y, Z of the magnets and the orientations θ, Φ of the magnets.

However, until now, the 3-axis magnetic field sensor using the FG sensor with high magnetic field detection power was as large as 30 mm, and the positional deviation between the sensors was as large as 1 mm to 3 mm. Because it was not possible, the positional accuracy was limited to about 4 mm. Existing magnetic field vector sensors include the Hall sensor type and the GSR sensor type, but their detection power (=sensor σ error) is as low as 50 nT to 1000 nT, and the position calculation accuracy is low. In other words, there is a trade-off relationship between size and detection power, and there is a limit as long as the existing magnetic field vector sensor is used.
In the present invention, it is assumed that the detection power of the magnetic field vector sensor is 100 times or more, or the size is reduced to 1/10 or less than that of the commercially available magnetic field vector sensor, so that a magnetic field vector sensor grid having a precise sensor density is manufactured and used. In addition, I created a calculation program (Fig. 11) that simultaneously obtains the position and orientation.

Position calculation was performed using the above calculation program, and the relationship between magnetic moment and position accuracy was investigated. The positional accuracy of the positions X, Y, Z depends on the height of the magnet, in other words, on the distance between the magnet and the surface of the sensor grid. In this experiment, the height was fixed at 40 mm, the magnet body was repeatedly moved ±10 mm in the X, Y, and Z directions, and the position measurement was repeated each time it returned to the original position, and the variation was measured.
The survey conditions were as follows: magnetic field vector sensor interval of 6 mm in the magnetic field sensor grid area (196 mm × 196 mm); number of magnetic field vector sensors: 17 × 17; was set to 0.1 nT, 1 nT and 10 nT, and the influence of the magnetic moment of the magnet was investigated.
As a result, as shown in FIG. 12(a), the position accuracy improved as the magnetic moment increased. A 4-fold increase in magnetic moment appeared to improve accuracy by a factor of 4, a 9-fold increase by a factor of 9, and a 100-fold increase by a factor of 100.

Similarly, the above calculation program was used to calculate the azimuth, and the relationship between the magnetic moment and the azimuth accuracy was investigated. The azimuth accuracies of the azimuths θ and φ are obtained by repeating θ rotation of ±10° on the XY plane and φ rotation of ±10° along the XZ plane, based on the horizontal direction in the X direction. The azimuth measurement was repeated each time it returned to the azimuth of , and its variability was measured.
The investigation conditions were the same as the conditions for obtaining the above positional accuracy.
As a result, as shown in FIG. 12(b), the azimuth accuracy improved as the magnetic moment increased.
Similar results were obtained for the effect of the magnetic moment and the effect of the magnetic field sensor spacing on the positional accuracy and azimuth accuracy in the Y direction.

Also, when the detection power of the magnetic field vector sensor was increased 100 times from 10 nT to 0.1 nT, the positional accuracy was improved by about 100 times and the azimuth accuracy was increased by about 100 times. In the present invention, in order to obtain a position accuracy of 0.5 mm or less and an orientation accuracy of 1 degree or less, the magnetic moment of the magnet is 1×10 ⁻¹⁰ to 500×10 ⁻¹⁰ Wbm and the detection power of the magnetic field sensor is 10 nT or less. I decided to

The present invention minimizes the size of the magnet body to ^0.3 to 2 ^mm in diameter and 3 to 15 mm in length. , The magnetic field vector sensor used in the magnetic field vector sensor grid has a detection power of 0.1 to 10 nT, the magnetic field vector sensor interval of the magnetic field vector sensor grid is 5 to 15 mm, and the magnetic field generated by the magnet is measured by the magnetic field vector sensor grid. , using only measurement points with an S/N ratio of 25 or more among all the measurement data, calculating with a position and orientation calculation program based on the Gauss-Newton method, and processing with a sensor grid data processing circuit. It is something to do. As a result, it is possible to provide a magnet position/orientation detecting device capable of determining the position and orientation of a magnet with a position accuracy of 0.5 mm or less and an orientation of 1 degree or less.

The present invention enables in vivo navigation systems such as catheters and gastroscopes, precise control of handpieces for dental treatment, and grasping of precise movements of alveolar ridges and teeth, and is expected to greatly improve the level of treatment.

2 is a plan view of a GSR element; FIG. Fig. 3 is an electronic circuit diagram for a GSR sensor; FIG. 3 is a plan view of a magnetic field sensor element having a truncated square pyramid shape according to an example; FIG. 10 is a cross-sectional view of the magnetic field sensor element having a truncated square pyramid shape according to the example taken along line A1-A2; 1 is an electronic circuit diagram for an example magnetic field vector sensor; FIG. FIG. 3 is an electrode wiring diagram of a magnetic field sensor element and a sensor substrate according to an example; 1 is a surface layout diagram of an ASIC according to an example; FIG. It is a surface wiring diagram of a sensor substrate according to an example. 1 is an assembly drawing of a magnetic field vector sensor according to an example; FIG. It is a magnetic field vector sensor grid and a wiring diagram according to an embodiment. Fig. 2 shows a flow chart diagram of a calculation program; (a) shows the influence of the magnetic moment of the magnet on the positional accuracy, and (b) shows the influence of the magnetic moment on the azimuth accuracy. FIG. 7a shows the effect of the spacing of the magnetic field vector sensors on the position accuracy, and FIG. 7b shows the effect of the spacing of the magnetic field vector sensors on the orientation accuracy. FIG. 4 is a plan view of a magnetic field sensor element using an on-ASIC type GSR sensor according to an embodiment;

A magnet position/orientation detecting device of the present invention comprises a magnet, a magnetic field vector sensor, a magnetic field sensor grid, a sensor grid data processing circuit, and a position and orientation arithmetic unit.
The magnet has a diameter of 0.3 to 2 mm, a length of 1 to 15 mm, and a magnetic moment of 1×10 ⁻¹⁰ to 500×10 ⁻¹⁰ Wbm.
The magnetic field vector sensor has four GSR sensor elements 35 attached to the magnetic field sensor element 3, as shown in FIGS. It is attached.

The GSR element is described in detail in Patent Document 5, which is cited here. The gist is described below. As shown in FIG. 1, a magnetic field detecting magnetic wire 12 having conductivity is placed on a substrate 11, a detecting coil 13 formed of a winding coil wound therearound, two electrodes (15) for wire conduction, and a coil voltage. The detection electrode (18) is composed of wires connecting two electrodes.

A GSR sensor consists of means for applying a pulse current with a frequency of GHz to the magnetic wire of the GSR element, and an electronic circuit that detects the coil voltage generated when the pulse current is applied and converts the coil voltage into an external magnetic field H. With a sensitive micro-magnetic field sensor, the detection power of the GSR sensor increases in proportion to the length of the magnetic wire. Therefore, the inventor designed a compact GSR element with a length of 0.4 to 3 mm and a width of 0.2 to 0.4 mm in order to measure a minute magnetic field of 10 nT or less in a minute space range.
As the electronic circuit, the electronic circuit 2 of the GSR sensor shown in FIG. 2 was adopted, and an application specific integrated circuit (hereinafter referred to as ASIC) was produced and used in the present invention.

The magnetic field vector sensor element 3 is obtained by affixing four GSR elements 35 in mirror symmetry with four-fold symmetry on the slope of the pedestal 30, which is a truncated quadrangular pyramid having an inclination angle (37)θ. As for the size, the length of one side of the square of the upper surface 31 corresponds to the width of the GSR element, and is 0.2 to 0.4 mm. The base 32 corresponds to 2 cos θ times the length of the GSR element plus the length of one side of the top square, and ranges from 0.6 mm at minimum to 6 mm at maximum. The height of the pedestal is sin θ times the length of the GSR element 35 . The inclination angle θ was set to 20 degrees to 45 degrees.

As shown in FIG. 6, the magnetic field vector sensor 4 has the magnetic field sensor element 3 assembled with four GSR elements 35 mounted on the sensor substrate 40, and the electrodes 41 (61) of the magnetic field sensor element 3 and the sensor substrate. An ASIC electrode was joined and wired, and three parts, ie, the magnetic field sensor element 3 assembled with the ASIC and four GSR elements, and the sensor substrate 40 on which these elements were mounted, were assembled.

Assuming that the electronic circuit is an ASIC, a surface wiring diagram of the ASIC is shown in FIG. FIG. 8 shows a surface wiring diagram of the sensor substrate.
The wiring connects the four electrodes of each element and the 16 element electrodes on the substrate surface with conducting wires. The 16 ASIC element electrodes on the sensor substrate and the element electrodes on the ASIC side are soldered. Further, the external connection electrodes on the ASIC side and the external connection electrodes on the surface side of the sensor substrate are soldered.

When the base 32 of the pedestal 30 was sufficiently larger than the ASIC, that is, when the base 32 was 2 mm or more, a hollow 38 was formed in the center of the base side, and the ASIC was mounted there, and both were placed on the sensor substrate. When the base is 2 mm or less, the back surface of the ASIC is attached directly to the bottom of the truncated quadrangular pyramid-shaped magnetic field sensor element.

FIG. 9 shows an assembly drawing (sectional view) of a magnetic field vector sensor 4A in which the magnetic field sensor element 3, the ASIC 40A, and the sensor substrate 40 are combined. The sensor substrate 40 has 16 element electrodes 41, 16 ASIC element electrodes, and a plurality of external connection electrodes on the front side. It has a wiring structure connected to the corresponding external connection electrode.
As a result, the external magnetic field detected by the magnetic field sensor element 3 is processed by the ASIC 40A to obtain the magnetic field vector (Hx, Hy, Hz), which can be taken out from the external connection electrodes on the back side of the sensor substrate.

The magnetic field vectors are obtained by processing the output voltages of the four GSR elements by the electronic circuitry shown in FIG. Hx = (1/2 cos θ) (Hx1-Hx2), Hy = (1/2 cos θ) (Hy1-Hy2), sensor Hz = (1/4 sin θ) (Hx1 + Hx + Hy1 + Hy) are calculated, and the magnetic field at the measurement position (Hx, Hy, Hz) can be determined.

When the tilt angle θ is 35.2 degrees (tan θ = 1/√2, sin θ = 1/√3, cos θ = √2/√3), Hx = √6/4 (Hx1-Hx2), Hy = √6 /4(Hx1-Hx2), Hz=√3/4(Hx1+Hx+Hy1+Hy). At this time, the measurement errors σx, σy, and σz of Hx, Hy, and Hz are all the same, that is, σx=σy=σz=0.86σ, so this is the most recommended angle. Practically, if σz is allowed to differ from σx (=σy) by about 25%, the tilt angle θ is about 20 degrees to 45 degrees. When emphasizing the accuracy of the magnetic field in the horizontal direction, it is slightly reduced from 35.2 degrees to about 20 degrees. be able to.

The performance of the magnetic field vector sensor is that the magnetic field vector (Hx, Hy, Hz) can be measured at a pinpoint position, the measurement sensitivity and measurement σ noise of Hx, Hy, and Hz are the same, and the magnetic field detection power is 0.5. The sensor is 1 nT to 10 nT or less, has a quadrangular pyramid shape, has a base of 2 mm to 6 mm and a height of 3 mm or less, is ultra-compact, and has excellent magnetic field detection capability.

In the present invention, when a single GSR element is installed on a slope and the coil voltage is wired to the ASIC, the coil voltage may drop or external noise may be felt. In such a case, the GSR element is formed directly on the integrated circuit ASIC to form a GSR sensor (referred to as an on-ASIC type GSR sensor), and is attached to the slope of the quadrangular pyramid to form a magnetic field vector sensor. good too.

The magnetic field vector sensor grid for measuring the magnetic field emitted from the magnet consists of at least 25 magnetic field vector sensors arranged on the plane of the magnetic field vector sensor substrate with a magnetic field vector sensor interval of 5 to 15 mm, and is measured by the magnetic field vector sensor grid. It consists of a sensor grid data processing circuit for processing measured data and a position and orientation calculation device for calculating the position and orientation from the sensor grid data.

A detailed description will be given below.
<Magnet body>
The size of the magnet body is 0.3 to 2 mm in diameter, 1 to 15 mm in length, and the magnetic moment of the magnet body is 1×10 ⁻¹⁰ to 1000×10 ⁻¹⁰ Wbm. Although the smaller the magnet, the smaller the magnet, the smaller the magnetic moment, the weaker the generated magnetic field, and the lower the positioning accuracy.

<Magnetic field vector sensor>
The magnetic field vector sensor 4, which is one pixel of the magnetic field vector sensor grid 8, will be described.
The magnetic field vector sensor 4 is composed of a pedestal 30 on a sensor substrate 40 and GSR elements 35 arranged on four slopes of the pedestal 30, as shown in the assembly drawing of FIG. 9 and the magnetic field sensor element 3 of FIGS. A magnetic field sensor element 40G is mounted, and is composed of an ASIC 40A and electrodes/wiring.
This magnetic field vector sensor 4 can measure a three-dimensional magnetic field vector and has a magnetic field detection power of 0.1 to 10 nT.

The structure of the GSR element is shown in FIG.
The size of the GSR element is 0.4-3 mm in length and 0.2-0.4 mm in width.

As the electronic circuit, the electronic circuit 2 of the GSR sensor shown in FIG. 2 was adopted, and an integrated circuit (ASIC) was produced. Two detection timing adjustment circuits 25a and 25b are used, and the sample and hold circuit uses two capacitors 28a and 28b and two electronic switches 27a and 27b. It should be noted that the present invention is not limited to this combination as long as the object of the present invention is met.

The magnetic field sensor element 40G(3), as shown in FIGS. √5), four of the GSR elements (1, 35) are attached to the slope (pedestal 30) of the truncated square pyramid with 4-fold symmetry.

The four GSR elements are connected to an electronic circuit 2A shown in FIG. 8, and the outputs Hx1, Hx2, Hy1 and Hy2 of the four GSR elements (70X1, 70X2, 70Y1 and 70Y2) are processed by a signal processing circuit. , is converted to Hx, Hy, and Hz by the arithmetic circuit, and then output from the data communication circuit.

In the wiring assembly of the magnetic field vector sensor, first, as shown in FIGS. 6 and 9, the magnetic field sensor element 40G and the sensor substrate 40 are wire-connected. ASIC surface wiring diagram 5 consists of device electrodes 51 and output electrodes 52, as shown in FIG.
As shown in FIG. 5, the sensor substrate 40 is provided with 16 element electrodes 61, 16 ASIC element electrodes 62, and a plurality of external connection electrodes on the surface side. It has a wiring structure that connects to the corresponding external connection electrodes on the back side through the holes.
The ASIC 40A is bonded to the surface of the sensor substrate 40 by connecting the output electrodes of the ASIC 40A and the ASIC output electrodes 52 of the sensor substrate 40, and connecting the output electrodes 52 of the ASIC and the output electrodes 63 of the sensor substrate. , all wirings of the magnetic field sensor are connected and connected to the output electrodes 46 on the rear surface of the sensor substrate through the through holes 44 of the sensor substrate 40 (FIGS. 7 and 8).

As shown in FIG. 9, the assembled magnetic field sensor 4A is composed of three parts, ie, a magnetic field sensor element assembled with an ASIC 40A and four GSR elements 40G, and a sensor substrate 40 on which these elements are mounted. 3 and 4, when the base 32 of the pedestal 30 is sufficiently larger than the ASIC 40A, that is, when the base is 2 mm or more, a hollow 38 is formed in the center of the base side. The ASIC 40A was attached there, and both were installed on the sensor substrate 40. FIG. When the base is 2 mm or less, the back surface of the ASIC is attached directly to the bottom surface 36 of the truncated quadrangular pyramid-shaped magnetic field sensor element.

In the magnetic field sensor 4, the external magnetic field detected by the magnetic field sensor element 40G is processed by the ASIC 40A to obtain magnetic field measurement values Hx1, Hx2, Hy1, and Hy2. Hx1-Hx2), Hy = (1/2 cos θ) (Hy1-Hy2), Hz = (1/4 sin θ) (Hx1 + Hx + Hy1 + Hy) are calculated to obtain the magnetic field (Hx, Hy, Hz) at the measurement position, and the sensor It can be taken out from the external connection electrode on the back side of the substrate.
As long as the three-dimensional magnetic field vector sensor has a magnetic field detection power of 0.1 to 10 nT, its configuration and type are not limited.

<Magnetic field vector sensor grid>
Next, when the magnetic field vector sensor 4 is used as a magnetic field vector sensor lid, the pixel size of the magnetic field vector sensor is 0.6 mm minimum to 6 mm maximum, but considering the width of the wiring, the minimum pixel size is 2 mm. up to 10 mm.

The sensor grid substrate 85, as shown in FIG. 10, is connected with multiplexers MUX 82 column by column, then all data is connected with the final MUX 83 and transferred to the external signal processing circuit. As for the power wiring, the power wiring VDD and the ground wiring GND are connected to each sensor using the row wiring.

Example 1 of the present invention will be described.
The size of the magnet is a stainless steel magnet with a diameter of 0.5 mm and a length of 5 mm, and the magnetic moment of the magnet is 5×10 ⁻⁹ Wbm.
The stainless magnet was made by wire-drawing 18Cr-8Ni austenitic stainless steel with a diameter of 1.0 mm to a diameter of 0.5 mm at a degree of cold working of 75%. After obtaining an 85% martensite content, a magnetic field of 3000 Oe was applied in the axial direction of the bar to magnetize the bar with a length of 5 mm to obtain a magnet.

The GSR sensor used was a GSR sensor element 1 having the structure shown in FIG. 1 and having a length of 2 mm and a width of 0.2 mm. The electronic circuit is an integrated circuit (ASIC) of the electronic circuit 2 of the GSR sensor shown in FIG. 2, and has a magnetic field detection power of 0.5 nT.

The magnetic field sensor element 3 is a pedestal of a truncated quadrangular pyramid having an inclination angle θ of 35.2 degrees (tan θ=1/√2, sin θ=1/√3, cos θ=√2/√3). As shown in FIGS. 3 and 4, four are attached to the slope of 30 in four-fold symmetry and mirror symmetry. The length of the base was 4 mm, and the height of the base was 2.4 mm.

Four GSR elements (70X1, 70X2, 70Y1, 70Y2) are connected to the electronic circuit 2A shown in FIG. , is converted into Hx, Hy, and Hz by the arithmetic circuit 75 and then output from the data communication circuit 76 .

In the wiring assembly of the magnetic field sensor, first, as shown in FIG. 6, the magnetic field sensor element and the sensor substrate 40 are wire-connected. The ASIC surface wiring diagram consists of device electrodes 51 and output electrodes 52, as shown in FIG. As shown in FIG. 8, the sensor substrate 40 is provided with 16 element electrodes 61, 16 ASIC element electrodes 62, and a plurality of external connection electrodes on the surface side. It has a wiring structure that connects to the corresponding external connection electrodes on the back side through the holes.
The ASIC is bonded to the surface of the sensor substrate. At that time, the output electrodes of the ASIC are connected to the ASIC output electrodes of the sensor substrate, and the output electrodes of the ASIC and the output electrodes of the sensor substrate are connected to form the wiring of the magnetic field sensor. are all connected to the output electrodes on the rear surface of the sensor substrate through the through holes of the sensor substrate.

As shown in FIG. 9, the assembled magnetic field vector sensor 4A is composed of three parts: the magnetic field sensor element (3) assembled with the ASIC 40A and four GSR elements, and the sensor substrate 40 on which these elements are mounted. The ASIC 40A is arranged in the hollow portion (38) of the bottom surface (36) of the element pedestal 40G.

The above-mentioned magnetic field vector sensor processes the external magnetic field detected by the GSR element with an ASIC to obtain magnetic field measurement values Hx1, Hx2, Hy1 and Hy2, which are converted to the inclination angle θ is 35.2 degrees. Ask. At this time, the measurement errors σx, σy, and σz of Hx, Hy, and Hz are all the same, that is, σx=σy=σz=0.86σ. Moreover, it was possible to improve the detection power of the magnetic field sensor used by about 14%.

As for the magnetic field vector sensor grid, since the base of the magnetic field vector sensor base is 4 mm, the pixel size was set to 5 mm in consideration of the wiring width. That is, the interval between the magnetic field vector sensors was set to 5 mm.

The sensor grid substrate 85, as shown in FIG. 10, is connected to the multiplexer MUX 82 column by column, then all data is connected to the final MUX 83 and transferred to the external signal processing circuit. A power supply wiring system is not shown, but power is supplied to all magnetic field vector sensors for magnetic field vector sensor grid operation.

The program for calculating the position and orientation of the magnet is to calculate and obtain the measured positions X, Y, and Z of the magnet and the orientations Θ and Φ of the magnet according to the flow chart shown in FIG. ,calculate.

As a result, the position and orientation of the magnet can be determined at a position and orientation measurement speed of 20 Hz with a position accuracy of 0.3 mm or less and an orientation accuracy of 0.7 degrees or less.

A second embodiment of the present invention consists of a magnetic field vector sensor using an on-ASIC type GSR sensor 91, and will be described with reference to FIG.
First, the magnet, the magnetic field vector sensor, the electronic circuit, the magnetic field vector sensor grid, and the formulas for calculating Hx, Hy, and Hz are configured according to the first embodiment.
The on-ASIC type GSR sensor 91 has a GSR element 912 directly formed on the surface of the ASIC 911, and four GSR sensors 91 are installed on the slope of a rectangle 902 on a base of a truncated quadrangular pyramid as shown in FIG.

The size of the GSR sensor 91 is 2.5 mm in length and 1.0 mm in width. The size of the magnetic field vector sensor is 6 mm in base and 1.5 mm in height. It is about five times better than the GSR sensor.
The position/orientation accuracy of Example 2 was 0.06 mm for position accuracy, 0.2 degree for orientation accuracy, and 20 Hz for position measurement speed.

The present invention can be used to measure the position and orientation of the tip of endoscopes and catheters, and in the dental field, to measure the position, movement, orientation, and rotation of mini-parts such as movement of teeth and alveolar ridges, and movement distance of treatment handpieces. It will be possible to accurately measure the amount, and it is expected to be widely applied.

1: GSR element 11: substrate, 12: magnetic wire, 13: coil, 14: wire terminal, 15: wire electrode,
16: Connection wiring (for wire electrode), 17: Coil terminal, 18: Coil electrode, 19: Connection wiring (for coil electrode)
2: Electronic circuit (electronic circuit of GSR sensor)
21: pulse oscillator, 22: GSR element, 221: wire electrode, 222: coil electrode, 23: parasitic capacitance, 24: circuit input electrode, 25a: first stage detection timing adjustment circuit (T1), 25b: second stage detection Timing adjustment circuit (T2), 26: sample and hold circuit (output side circuit), 27a: 1st stage electronic switch (SW1), 27b: 2nd stage electronic switch (SW2), 28a: 1st stage sample and hold capacitor ( C1), 28b: second-stage sample-and-hold capacitor (C2), 29: amplifier 2A: electronic circuit (magnetic field sensor electronic circuit)
70 (70X1, 70X2, 70Y1, 70Y2): GSR element, 71: pulse oscillator, 72: signal processing circuit, 73: selector switch, 74: AD converter, 75: arithmetic circuit, 76: data communication circuit 3: magnetic field vector sensor Element 30: Pedestal, 31: Upper surface, 32: Base, 33: Ridge, 34: Axis line mark, 35: GSR element 351: Magnetic wire, 36: Bottom, 37: Tilt angle, 38: Hollow part (hollow)
4, 4A: Magnetic field vector sensor (assembly)
40: sensor substrate, 40A: ASIC, 40G: element pedestal (consisting of pedestal 30 and GSR element), 41: element electrode (element electrode on surface of sensor substrate 40), 42: connection wiring (electrode of element 35 and element electrode 41), 43: Connection wiring (wiring between the element electrode 41 and the ASIC electrode), 44: Through hole, 45: Connection wiring (wiring on the back surface of the sensor substrate 40) 46: Output electrode (wiring on the sensor substrate 40) output electrode on the back)
5: ASIC electrode arrangement 51: ASIC element electrode 52: ASIC output electrode 6: Wiring diagram on the surface of the sensor substrate 61: element electrode (element electrode 41) 62: ASIC electrode (ASIC element electrode) 63: output electrode, 64: connection wiring (wiring between device electrode 61 and ASIC electrode 62)
8: Magnetic field vector sensor grid 81: Magnetic field vector sensor 82: Signal output primary multi-breaker MUX 83: Signal output secondary multi-breaker 84: Signal output terminal 85: Sensor grid board 86: Wiring board 9: Magnetic field sensor element (on-ASIC type)
90: Pedestal, 901: Triangular slope, 902: Rectangular slope, 903: Square upper surface 91: GSR sensor, 911: ASIC, 912: GSR element, 913: Magnetic wire

Claims (3)

In a magnet position/orientation detection device comprising a magnet, a magnetic field vector sensor, a magnetic field sensor grid, a sensor grid data processing circuit, and a position and orientation calculator,
The magnet body has a diameter of 0.3 to 2 mm and a length of 1 to 15 mm, and a magnetic moment of the magnet body is 1×10 ⁻¹⁰ to 500×10 ⁻¹⁰ Wbm,
The magnetic field vector sensor measures a magnetic field vector emitted from the magnet, and is composed of a magnetic field vector sensor element, an electronic circuit, and an arithmetic circuit,
The magnetic field vector sensor element has a base of 0.6 mm to 6 mm, a height of 0.3 mm to 3 mm, and four slopes of a pedestal of a truncated quadrangular pyramid or an octagonal truncated pyramid having an inclination angle θ of 20 degrees to 45 degrees. Four GSR elements are attached in four-fold symmetry and mirror image symmetry to
The electronic circuit converts the output voltages of the four GSR elements into four magnetic field measurements Hx1, Hx2, Hy1, Hy2 at a measurement sampling rate of 100 Hz to 10 KHz with a magnetic field detectivity of 0.1 to 10 nT. have the function
The arithmetic circuit is
Hx = (1/2 cos θ) (Hx1-Hx2),
Hy = (1/2 cos θ) (Hy1-Hy2),
Hz = (1/4 sin θ) (Hx1 + Hx + Hy1 + Hy),
Calculate the magnetic field vector (Hx, Hy, Hz) with the following formula,
The magnetic field vector sensor grid comprises at least 25 magnetic field vector sensors arranged on a plane plate at intervals of 5 to 15 mm,
The sensor grid data processing circuit processes the magnetic field measurement data measured by the magnetic field sensor grid at high speed and transfers it to the position and orientation calculation device,
The position and orientation calculation device calculates the positions X, Y, Z and the orientations Θ, Φ of the magnet from the sensor grid data by the Gauss-Newton method, and measures the position and orientation with a position accuracy of 0.5 mm or less and an orientation accuracy of 1 degree or less. A magnetic body position/direction detector, characterized in that a velocity is calculated from 1 Hz to 50 Hz and the calculated value is output to a display device.

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