This application claims the benefit of Taiwan application Serial No. 107140436, filed Nov. 14, 2018, the disclosure of which is incorporated by reference herein in its entirety.
This disclosure relates to a localization method and a system thereof, and more particularly to a localization and attitude estimation method using magnetic fields and a system thereof.
An automated guided vehicle (AGV) is an important carrier in automated material transfer field. Compared with the conventional transfer method using a conveyor belt, the AGV has the advantages of occupying less space and more flexibly adjusting in the production line. For the trackless guided AGV, the localization of the existing AGV is normally achieved through a laser reflective label, a magnetic lamdmark, a two-dimensional bar code label or the like. However, when the label localization technology is actually used, the space site needs to be emptied in advance. So, it is hard to be used for those plants lack of pre-planning site. In addition, the label localization technology is limited to the two-dimensional condition, and thus cannot be applied to a three-dimensional localization system. Also, the label localization technology cannot judge the attitude of the object in the three-dimensional space, and therefore needs to be improved.
This disclosure is directed to a localization and attitude estimation method using magnetic fields and a system thereof, and the position information of magnetic landmarks and magnetic sensors may be obtained by analyzing the magnetic fields of multiple magnetic landmarks in a three-dimensional space.
According to one embodiment of this disclosure, a localization and attitude estimation method using magnetic fields is provided. The method includes the following steps. First, at least three magnetic landmarks arbitrarily disposed around a moving carrier in three-dimensional coordinates are selected, wherein any two of the at least three magnetic landmarks have different magnetic directions. Position information and magnetic moment information of the at least three magnetic landmarks in the three-dimensional coordinates are unknown information. One set of at least five tri-axes magnetic sensors is used to sense the magnetic fields of the at least three magnetic landmarks, and three magnetic components on three axes of a current position of each of the tri-axes magnetic sensors are respectively generated using a demagnetization method, wherein spatial distributions of the set of at least five tri-axes magnetic sensors are not located on a same plane. Five non-linear magnetic equations are obtained according to the three magnetic components on the three axes of the current position of each of the tri-axes magnetic sensor. Then, the five non-linear magnetic equations are solved according to magnetic moment vectors of the at least three magnetic landmarks in a null space to obtain the position information and the magnetic moment information of the at least three magnetic landmarks in the three-dimensional coordinates. In addition, position vectors and attitude vectors of the set of at least five tri-axes magnetic sensors in the three-dimensional coordinates are estimated according to tri-axes magnetic moment vectors of the at least three magnetic landmarks.
According to another embodiment of this disclosure, a localization and attitude estimation system using magnetic fields is provided to localize a moving carrier. The localization and attitude estimation system includes at least three magnetic landmarks, one set of at least five tri-axes magnetic sensors and a logic operation processing unit. At least three magnetic landmarks are arbitrarily disposed around the moving carrier in three-dimensional coordinates, wherein any two of the at least three magnetic landmarks have different magnetic directions. The set of at least five tri-axes magnetic sensors is disposed on the moving carrier, wherein spatial distributions of the set of at least five tri-axes magnetic sensors are not located on a same plane. The logic operation processing unit is connected to the set of at least five tri-axes magnetic sensors. The set of at least five tri-axes magnetic sensors senses the magnetic fields of the at least three magnetic landmarks, and generates at least fifteen sets of magnetic field information to the logic operation processing unit. The logic operation processing unit estimates position vectors and attitude vectors of the set of at least five tri-axes magnetic sensors in the three-dimensional coordinates according to tri-axes magnetic moment vectors of the at least three magnetic landmarks sensed by each of the tri-axes magnetic sensors.
The above and other aspects of this disclosure will become understood with regard to the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings.
In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing.
The embodiments are described in detail as below, and the examples are only intended to be illustrative and not intended to limit the scope of this disclosure. In the following illustration, the same/similar symbols represent the same/similar elements. Directional terms, such as up, down, left, right, front, back and the like, mentioned in the following examples, only refer to the directions of the drawings. Therefore, the directional terms are used to describe but not to limit this disclosure.
Referring to
The number of the magnetic landmarks 111 to 113 is not restricted, and may be an arbitrary number equal to or greater than 3. The magnetic landmarks 111 to 113 may be disposed in an area around the moving carrier 120, such as the ground, walls or any point in the three-dimensional space. When the moving carrier 120 moves to a current position, at least three magnetic landmarks 111 to 113 arbitrarily disposed around the current position of the moving carrier 120 are selected as the magnetic landmarks for localization. When the moving carrier 120 moves to a new position, at least three magnetic landmarks 111 to 113 disposed around the new position of the moving carrier 120 may be selected as the magnetic landmarks for localization, and so on.
The logic operation processing unit 130 may be, for example, a computer or a single-chip microprocessor disposed in the computer, or may include a computer program stored in a computer readable recording medium. In another embodiment, the logic operation processing unit 130 can be disposed on the moving carrier 120. Before the logic operation processing unit 130 receives magnetic field information, noise in the magnetic field information may be reduced through a low-pass filter, and the signal to noise ratio is increased. Then, the magnetic field information may be converted into digital magnetic field information through an analog/digital converter.
Referring to
In one embodiment, the at least three magnetic landmarks 111 to 113 do not located at the same point in the three-dimensional coordinates (X, Y, Z) and are not restricted to be orthogonal to one another. That is, the three magnetic landmarks 111 to 113 need not to be restricted to be orthogonal to one another and located at the same point as long as the sum of any two of magnetic field vectors is unequal to the multiple of the other one of the magnetic field vectors, so that the flexibility of the system is enhanced.
Referring to
In this embodiment, each of the tri-axes magnetic sensors 121 to 125 is connected to the logic operation processing unit 130, to generate at least three sets of magnetic field information to the logic operation processing unit 130, and thus at least fifteen sets of magnetic field information may be provided to the logic operation processing unit 130. In order to facilitate calculation of magnetic field components of the at least three magnetic landmarks 111 to 113, magnetic fields of the three magnetic landmarks 111 to 113 may be separated using a demagnetization method, wherein each of the magnetic sensors obtains the sum of the magnetic field vectors of the three magnetic landmarks 111 to 113, and the sum of the magnetic field vectors BS1, BS2, . . . , BSN is expressed as follows, N is an integer equal to 5 or greater than 5:
Next, the logic operation processing unit 130 may use the demagnetization method of a band pass filter to obtain three magnetic components of magnetic field vectors having different constant frequencies on three axes of the current position of each of the tri-axes magnetic sensors 121 to 125, which are respectively expressed as BS1′, BS2′, . . . , BSN′, where
The demagnetization method includes using an extended Kalman filter having three different constant frequencies functioning as restriction items to resolve waveforms and amplitudes of the at least three magnetic landmarks 111 to 1113 and obtain at least three sets of waveforms and amplitudes as the three magnetic components of the at least three magnetic landmarks 111 to 113 on the three axes of the three-dimensional coordinates (X, Y, Z). Next, in the step S13, for the same magnetic landmark, the position vector and the attitude vector of each of the magnetic landmarks 111 to 113 may be obtained through the following steps.
The magnetic field of each of the magnetic landmarks is known as
where X=P−OB, R=|X|, |H|=1, P is a position of a single tri-axes magnetic sensor, OB is a position of a single magnetic landmark, H is a magnetic moment unit vector of the single magnetic landmark, X is a position vector of the single tri-axes magnetic sensor relative to each of the magnetic landmarks, and R is an absolute value of the position vector X (i.e., a distance). In
In addition, the magnetic field of each of the magnetic landmarks 111 to 113 is a closed curve, and the magnetic force lines are not interlaced. So, a magnetic field vector and a magnetic moment and a displacement vector of each point on each magnetic force line are disposed on the same plane, and an inner product space thereof is null, that is, B×X·H=0. According to the above-mentioned X=P−OB, B×P·H+H×OB·B=0 may be obtained. Rearrange the above results can obtain
For all tri-axes magnetic sensors 121 to 125, at least five non-linear magnetic equations may be obtained as follows according to the three magnetic components on the three axes of the current position of each of the tri-axes magnetic sensors 121 to 125,
According to the above-mentioned relationship, it is obtained that
the above-mentioned five non-linear magnetic equations are solved according to magnetic moment vectors of the at least three magnetic landmarks 111 to 113 in a null space, and the unit vector of the null space may be determined. The calculation process is as follows. Firstly, let the null space be
then HLi=V(4:6). Let r=HLi×OBLi=V(1:3), and OBLi=r×HLi+tHLi, and substitute OBLi back to Equation (3), so that the parameter t can be solved, and OBLi is obtained. BT is determined according to OBLi and HLi. If BT is negative, then HLi is multiplied by a minus sign.
According to the above-mentioned results, the logic operation processing unit 130 may obtain the position information and the magnetic moment information (i.e., OBLi and HLi) of the at least three magnetic landmarks 111 to 113 in the three-dimensional coordinates (X, Y, Z). As shown in
Next, in the step S14, after the position information and the magnetic moment information of the at least three magnetic landmarks 111 to 113 are obtained, the position vector of each of the tri-axes magnetic sensors 121 to 125 relative to the each of the magnetic landmarks 111 to 113 can be obtained according to Equation (1), and the attitude vector of each of the tri-axes magnetic sensors 121 to 125 in the three-dimensional coordinates (X, Y, Z) can be estimated according to the tri-axes magnetic moment vector of each of the three magnetic landmarks 111 to 113 sensed by each of the tri-axes magnetic sensors 121 to 125.
As shown in
Next, in the step S15, an magnetic moment pointing matrix of the current magnetic landmark is [HL1 HL2 . . . HLN]=HL. If an initial state matrix is known as H0, then the current rotation matrix relative to the initial state is R=(H0HLT(HLHLT)−1). Any current position of the magnetic landmark is oB. If the initial position of the magnetic landmark is known as oB
After PGlobal and R are obtained, the magnetic moment information HL and the position information OB of a unknown magnetic landmark relative to HL0 and OB0 of the initial coordinate system can be calculated according to the following equations, and the magnetic moment information HL and position information OB can be recorded, where
OB0=RTOB+PGlobal
HL0=RTHL
That is, in the step S15, when the moving carrier 120 moves to a new position A (see
Referring to
Alternatively, in
The localization and attitude estimation method using magnetic fields and the system thereof disclosed by the above-mentioned embodiment of this disclosure may be used to detect the position and the attitude of the moving carrier (such as the unmanned vehicle or the arbitrary object) in the space, and the position of the magnetic landmark may be arbitrarily placed without establishing the map in advance to reduce the data quantity and the computation amount for the map. Therefore, this disclosure does not require site layout of the environment in advance, so that the localization system is more flexible and the localization range is wider, and the mobility and convenience of the site layout are possessed.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.
Number | Date | Country | Kind |
---|---|---|---|
107140436 | Nov 2018 | TW | national |
Number | Name | Date | Kind |
---|---|---|---|
6269291 | Segeren | Jul 2001 | B1 |
6690963 | Ben-Haim | Feb 2004 | B2 |
6762600 | Khalfin | Jul 2004 | B2 |
6841994 | Wiegert | Jan 2005 | B1 |
6888353 | Wiegert | May 2005 | B1 |
7292948 | Jones, Jr. et al. | Nov 2007 | B2 |
7425829 | Zeller | Sep 2008 | B2 |
7835785 | Scully et al. | Nov 2010 | B2 |
7912633 | Dietsch et al. | Mar 2011 | B1 |
8220710 | Hoffman et al. | Jul 2012 | B2 |
8928602 | Wan | Jan 2015 | B1 |
9329599 | Sun et al. | May 2016 | B1 |
9348009 | Sontag | May 2016 | B2 |
9459124 | Khalfin et al. | Oct 2016 | B2 |
10026001 | Falconer et al. | Jul 2018 | B2 |
10027952 | Karvounis | Jul 2018 | B2 |
10168393 | Stetson, Jr. | Jan 2019 | B2 |
20060038555 | Higgins et al. | Feb 2006 | A1 |
20090128139 | Drenth et al. | May 2009 | A1 |
20100127696 | Huber et al. | May 2010 | A1 |
20120277529 | Popescu | Nov 2012 | A1 |
20140320394 | Costanzo | Oct 2014 | A1 |
20150061648 | Park et al. | Mar 2015 | A1 |
20160147231 | Sun et al. | May 2016 | A1 |
20180011472 | Sun et al. | Jan 2018 | A1 |
20180172454 | Ghadiok et al. | Jun 2018 | A1 |
20180189565 | Lukierski et al. | Jul 2018 | A1 |
20190078909 | Luo | Mar 2019 | A1 |
20200370889 | Eitel | Nov 2020 | A1 |
Number | Date | Country |
---|---|---|
102147259 | Aug 2011 | CN |
102686979 | Feb 2015 | CN |
103288116 | Feb 2015 | CN |
105044630 | Nov 2015 | CN |
204871280 | Dec 2015 | CN |
107063237 | Aug 2017 | CN |
2 863 284 | Apr 2015 | EP |
11-304405 | Nov 1999 | JP |
10-2018-0079215 | Jul 2018 | KR |
200934710 | Aug 2009 | TW |
M465591 | Nov 2013 | TW |
201407308 | Feb 2014 | TW |
I431247 | Mar 2014 | TW |
201447525 | Dec 2014 | TW |
I470386 | Jan 2015 | TW |
201619038 | May 2016 | TW |
I582035 | May 2017 | TW |
I608243 | Dec 2017 | TW |
201802487 | Jan 2018 | TW |
I634404 | Sep 2018 | TW |
WO 2018088873 | May 2018 | WO |
Entry |
---|
Hu (Hu, Chao et al., “A Cubic 3-Axis Magnetic Sensor Array for Wirelessly Tracking Magnet Position and Orientation,” IEEE Sensors Journal, vol. 10, No. 5, May 2010, pp. 903-913.). (Year: 2010). |
C. Hu (Hu, Chao et al., “A Novel Positioning and Orientation System Based on Three-Axis Magnetic Coils,” IEEE Transactions on Magnetics, vol. 48, No. 7, Jul. 2012, pp. 2211-2219.). (Year: 2012). |
Marins (Marins, J. L. et al., “An Extended Kalman Filter for Quaternion-Based Orientation Estimation Using MARG Sensors,” IEEE/RSJ International Conference on Intelligent Robots and Systems, Maul, Hawaii, USA. Oct. 29-Nov. 3, 2001, pp. 2003-2011.). (Year: 2001). |
Chung et al., “Indoor Location Sensing Using Geo-Magnetism,” MIT Media Laboratory, pp. 141-154. |
Hou et al., “Experimental Study of Magnetic-based Localization Model for Miniature Medical Device Placed Indwelling Human Body,” Proceedings of the 2005 IEEE, Engineering in Medicine and Biology 27th Annual Conference, Shanghai, China, Sep. 1-4, 2005, pp. 1309-1312. |
Hu et al., “A Novel Positioning and Orientation System Based on Three-Axis Magnetic Coils,” IEEE Transactions on Magnetics, vol. 48, No. 7, Jul. 2012, pp. 2211-2219. |
Hu et al., “A Robust Orientation Estimation Algorithm Using MARG Sensors,” IEEE Transactions on Instrumentation and Measurement, vol. 64, No. 3, Mar. 2015, pp. 815-822. |
Kemppainen et al., “Magnetic field SLAM exploration: frequency domain Gaussian processes and informative route planning,” Department of Computer Science and Engineering, University of Oulu, Finland, 2015, 7 pages. |
Le Grand et al., “3-Axis Magnetic Field Mapping and Fusion for Indoor Localization,” 2012 IEEE International Conference on Multisensor Fusion and Integration for Intelligent Systems (MFI), Sep. 13-15, 2012. Hamburg, Germany, pp. 358-384. |
Nara et al., “A Closed-Form Formula for Magnetic Dipole Localization by Measurement of Its Magnetic Field and Spatial Gradients,” IEEE Transactions on Magnetics, vol. 42, No. 10, Oct. 2006, pp. 3291-3293. |
Pang et al., “Integrated Compensation of Magnetometer Array Magnetic Distortion Field and Improvement of Magnetic Object Localization,” IEEE Transactions on Geoscience and Remote Sensing, vol. 52, No. 9, Sep. 2014, pp. 5670-5676. |
Skog et al., “Pedestrian tracking using an IMU array,” IEEE CONECCT2014 1569825763, Department of Signal Processing, ACCESS Linnaeus Centre, KTH Royal Institute of Technology. Stockholm, Sweden, pp. 1-4. |
Sun et al., “A Single Dipole-based Localization Method in Near Magnetic Field using IMU Array,” 2016 IEEE International Workshop on Advanced Robotics and its Social Impacts (ARSO), Shanghai, China, Jul. 8-10, 2016, pp. 152-157. |
Vallivaara et al., “Magnetic field-based SLAM method for solving the localization problem in mobile robot floor-cleaning task,” The 15th International Conference on Advanced Robotics, Tallinn University of Technology, Tallinn, Estonia, Jun. 20-23, 2011, pp. 198-203. |
Vallivaara et al., “Monty Hall Particle Filter: a new method to tackle predictive model uncertainties,” Computer Science and Engineering Laboratory, University of Oulu, Finland, 2013, 8 pages. |
Vallivaara et al., “Simultaneous Localization and Mapping Using Ambient Magnetic Field,” 2010 IEEE International Conference on Multisensor Fusion and Integration for Intelligent Systems, University of Utah, Salt Lake City, UT, USA, Sep. 5-7, 2010, pp. 14-19. |
Vallivaara, “Simultaneous Localization and Mapping Using the Indoor Magnetic Field,” Acta Univ. Oul. C 642, 2018, pp. 1-98. |
You et al., “Localization Using Magnetic Patterns for Autonomous Mobile,” International Journal of Advanced Robotic Systems, 2014, 11:50, pp. 1-10. |
Taiwanese Office Action and Search Report for Taiwanese Application No. 107140436, dated Jun. 3, 2019. |
Number | Date | Country | |
---|---|---|---|
20200149862 A1 | May 2020 | US |