Position Tracking System Employing External Magnetic Field

• US 20180010925A1
• Filed: 07/09/2016
• Published: 01/11/2018
• Est. Priority Date: 07/09/2016
• Status: Active Grant

• Current Assignee: Maximillian Hobson-Dupont
• Original Assignee: Maximillian Hobson-Dupont
• Inventors: Hobson-Dupont, Maximillian
• Granted Patent: US 10,761,616 B2
• Time in Patent Office: Days
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G06F 17/16 Matrix or vector computation , e.g. matrix-matrix or matrix-vector multiplication, matrix factorization matrix transposition G06F7/78
• CPC Class Codes: G06F 3/0346 with detection of the device orientation or free movement in a 3D space, e.g. 3D mice, 6-DOF [six degrees of freedom] pointers using gyroscopes, accelerometers or tilt-sensors
• CPC Class Codes: G06F 3/038 Control and interface arrangements therefor, e.g. drivers or device-embedded control circuitry
• CPC Class Codes: G06F 3/0383 Signal control means within the pointing device

Abstract

A common method for providing user-input to an electronic system consists of tracking the position and motion of an object moved by the user and conveying this information to the electronic system. One embodiment of a positional tracking system for an object has an external and stationary magnetic-field emitter, a magnetic-field sensor which moves with the tracked object, and a microprocessor that compares magnetic-field intensity measurements taken by the sensor and compares it to magnetic-field characteristics defined for the external magnetic field emitter. A nonlinear equation solver, particle filter, or other method is used to determine the position of the sensor in the magnetic field. In this way the position of an object can be tracked using a single magnetic field emission source. This positional information can be combined with an inertial tracking system to mitigate drift errors.

Claims

1. A method for tracking motion of an object, comprising:

a. providing a magnetic field emission means which is able to emit a predetermined magnetic field,

b. providing a magnetic field sensing means to sense said magnetic field,

c. providing a computational means for predicting the characteristics of said magnetic field wherein a location in the magnetic field is given as an input and the characteristics of said magnetic field at said location are taken as the output of said computational means,

and

d. providing a logical means for determining the position of said magnetic sensing means in said emitted magnetic field by varying the positional input of said computational means until the output of said computational means is equivalent to the output of said magnetic field sensing means,

whereby the positional input of said computational means is equivalent to the physical location of the magnetic field sensing means.

2. The method for tracking motion of an object of claim 1, additionally providing a computational means for modifying the output of the magnetic field sensing means such that the output is corrected for a change in orientation of the object whose motion is being tracked

3. The method for tracking motion of an object of claim 1, additionally providing computational means for modifying the output of the computational means for predicting the characteristics of the known magnetic field such that the output is corrected for a change in orientation of the object whose motion is being tracked

4. The method for tracking motion of an object of claim 2, additionally comprising:

a. providing a plurality of magnetic sensing means arranged with known locations and distances relative to each-other,

b. providing a plurality of computational means for correcting the output of the magnetic field sensing means for a given input orientation, and

c. providing a logical means for determining the orientation of the object by varying the input orientation of each computational means for orientation correction until the resulting position outputs for each magnetic field measurement means result in relative distances between them being equal to the known distances between them

whereby the orientation input that results in agreement between the known and calculated distances is equivalent to the orientation of the objecting being tracked relative to the reference orientation of the magnetic field.

5. The method for tracking motion of an object of claim 1, additionally comprising:

a. providing an linear acceleration measurement means,

b. providing an angular velocity measurement means,

c. providing a computational means for determining object position and orientation using linear acceleration and angular velocity measurements, and

d. providing a computational means for combining measurements of object motion using linear acceleration, angular velocity and magnetic positional sensing means using a Kalman filter

whereby the position of an object is known to a higher degree of certainty than if it were found using all three measurement means.