Inertially Tracked Objects

• US 20110320153A1
• Filed: 06/23/2010
• Published: 12/29/2011
• Est. Priority Date: 06/23/2010
• Status: Active Grant

• Current Assignee: MAKO Surgical Corporation (Stryker Corporation)
• Original Assignee: MAKO Surgical Corporation (Stryker Corporation)
• Inventors: Kang, Hyosig, Lightcap, Chris
• Granted Patent: US 9,226,799 B2
• Time in Patent Office: Days
• US Class Current: 702/94
• CPC Class Codes: A61B 2017/00477 Coupling A61B2017/0046 takes precedence
• CPC Class Codes: A61B 2017/00725 Calibration or performance testing
• CPC Class Codes: A61B 2017/00876 magnetic
• CPC Class Codes: A61B 2034/2048 using an accelerometer or inertia sensor
• CPC Class Codes: A61B 2034/2059 Mechanical position encoders
• CPC Class Codes: A61B 2034/2068 using pointers, e.g. pointers having reference marks for determining coordinates of body points
• CPC Class Codes: A61B 2034/207 Divots for calibration
• CPC Class Codes: A61B 2090/0818 Redundant systems, e.g. using two independent measuring systems and comparing the signals
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
• CPC Class Codes: G01C 21/166 Mechanical, construction or arrangement details of inertial navigation systems

Abstract

Described are computer-based methods and apparatuses, including computer program products, for inertially tracked objects with a kinematic coupling. A tracked pose of a first inertial measurement unit (IMU) is determined, wherein the first IMU is mounted to a first object. The tracked pose of the first IMU is reset while the first object is in a first reproducible reference pose with a second object.

Claims

1. A method of resetting a tracking element, comprising:

determining, by an inertial tracking system, a tracked pose of a first inertial measurement unit (IMU), wherein the first IMU is mounted to a first object; and

resetting, by the inertial tracking system, the tracked pose of the first IMU while the first object is in a first reproducible reference pose with a second object.

2. The method of claim 1, wherein the first IMU comprises a first coupling configured to couple to a second coupling mounted to the second object to achieve the first reproducible reference pose.

3. The method of claim 1 further comprising:

determining, by the inertial tracking system, a tracked pose of a second IMU, wherein the second IMU is mounted to the second object; and

resetting, by the inertial tracking system, the tracked pose of the second IMU while the first object is in the first reproducible reference pose with the second object.

4. The method of claim 3, wherein resetting the tracked pose of the first IMU and resetting the tracked pose of the second IMU comprise:

determining the first object and the second object are in the first reproducible reference pose; and

resetting the tracked pose of at least one of the first IMU and the second IMU based on the first reproducible reference pose.

5. The method of claim 3 wherein the first reproducible reference pose comprises a predetermined transformation indicative of a first pose of the second IMU with respect to a first pose of the first IMU.

6. The method of claim 3 further comprising determining a tracked pose of the second IMU with respect to the first IMU based on the tracked pose of the first IMU, the tracked pose of the second IMU, and the first reproducible reference pose.

7. The method of claim 3 wherein the first IMU comprises a first kinematic coupling and the second IMU comprises a second kinematic coupling.

8. The method of claim 7, wherein:

the first kinematic coupling is configured to kinematically couple to the second kinematic coupling to achieve the first reproducible reference pose; and

resetting the tracked pose of the first IMU, resetting the tracked pose of the second IMU, or both, occurs when the second kinematic coupling is kinematically coupled to the first kinematic coupling.

9. The method of claim 3, further comprising:

determining, by the inertial tracking system, that an error associated with the first IMU, the second IMU, or both, exceeds a predetermined threshold; and

resetting the tracked pose of the first IMU, the tracked pose of the second IMU, or both, based on the first reproducible reference pose.

10. The method of claim 3, wherein the first reproducible reference pose comprises a predetermined transformation indicative of a first pose of the second IMU with respect to a first pose of the first IMU, and resetting the tracked pose of the first IMU and resetting the tracked pose of the second IMU comprise:

setting the tracked pose of the first IMU to the first pose of the first IMU;

or

setting the tracked pose of the second IMU to the first pose of the second IMU;

or both.

11. The method of claim 3, further comprising:

a third object configured to couple to at least one of the first object and the second object to achieve a second reproducible reference pose;

receiving data indicative of the first object being coupled to at least one of the second object in the first reproducible reference pose and the third object in the second reproducible reference pose; and

resetting a tracked pose of the second IMU, a third IMU mounted to the third object, or both based on the data.

12. The method of claim 3, further comprising:

a third object configured to couple to at least one of the first object and the second object to achieve a second reproducible reference pose;

receiving data indicative of the third object being coupled to the at least one of the first object and the second object in the second reproducible reference pose; and

resetting a tracked pose of a third IMU mounted to the third object based on the data.

13. The method of claim 1, wherein the second object includes a first portion configured to couple to the first IMU to achieve the first reproducible reference pose and a second portion configured to couple to a second IMU mounted to a third object to achieve a second reproducible reference pose.

14. The method of claim 13, further comprising:

determining, by the inertial tracking system, a tracked pose of the second IMU; and

resetting, by the intertial tracking system, the tracked pose of the first IMU, the tracked pose of the second IMU, or both, when the first IMU is coupled to the first portion of the second object in the first reproducible reference pose and the second IMU is coupled to the second portion of the second object in the second reproducible reference pose.

15. The method of claim 1, further comprising:

determining, by the inertial tracking system, that an error associated with the first IMU exceeds a predetermined threshold; and

resetting the tracked pose of the first IMU based on the first reproducible reference pose.

16. The method of claim 1, wherein resetting comprises:

determining the first object and the second object are in the first reproducible reference pose; and

resetting the tracked pose of the first IMU based on the first reproducible reference pose.

17. The method of claim 16, wherein determining the first object and the second object are in the first reproducible reference pose comprises determining the second object is kinematically coupled to the first object.

18. A method for inertially tracking one or more objects, the method comprising:

determining, by an inertial tracking system, that an error associated with a first IMU, a second IMU, or both, exceeds a predetermined threshold, wherein the error is indicative of a first discrepancy between a tracked pose of the first IMU and an actual pose of the first IMU, a second discrepancy between a tracked pose of the second IMU and an actual pose of the second IMU, or both; and

resetting the tracked pose of the first IMU, the tracked pose of the second IMU, or both, based on a reproducible reference pose, wherein the reproducible reference pose comprises a predetermined transformation indicative of a first pose of the second IMU with respect to a first pose of the first IMU, comprising;

setting the tracked pose of the first IMU to the first pose of the first IMU;

or

setting the tracked pose of the second IMU to the first pose of the second IMU;

or both.

19. The method of claim 18, further comprising receiving data indicative of the first IMU being kinematically coupled to the second IMU to achieve the reproducible reference pose.

20. The method of claim 18, further comprising determining a tracked pose of the second IMU with respect to the first IMU based on the tracked pose of the first IMU, the tracked pose of the second IMU, and the reproducible reference pose.

21. A computer program product, tangibly embodied in a computer readable storage medium, the computer program product including instructions being operable to cause a data processing apparatus to:

determine a tracked pose of a first inertial measurement unit (IMU), wherein the first IMU is mounted to a first object; and

reset the tracked pose of the first IMU while the first object is in a first reproducible reference pose with a second object.

22. An apparatus for inertially tracking one or more objects, the apparatus comprising an inertial tracking system configured to:

determine a tracked pose of a first inertial measurement unit (IMU), wherein the first IMU is mounted to a first object; and

reset the tracked pose of the first IMU while the first object is in a first reproducible reference pose with a second object.

23. An apparatus for inertially tracking one or more objects, the apparatus comprising a means for:

determining a tracked pose of a first inertial measurement unit (IMU), wherein the first IMU is mounted to a first object; and

resetting the tracked pose of the first IMU while the first object is in a first reproducible reference pose with a second object.