Inertially tracked objects

• US 9,226,799 B2
• Filed: 06/23/2010
• Issued: 01/05/2016
• Est. Priority Date: 06/23/2010
• Status: Active Grant

• Current Assignee: MAKO Surgical Corporation (Stryker Corporation)
• Original Assignee: MAKO Surgical Corporation (Stryker Corporation)
• Inventors: Lightcap, Chris, Kang, Hyosig
• Primary Examiner(s): Le, Toan
• Assistant Examiner(s): RIVERA VARGAS, MANUEL A
• Application Number:
  US12/821,365
• Publication Number:
  US 20110320153A1
• Time in Patent Office: 2,022 Days
• Field of Search: 702/94, 600/426, 606/130
• US Class Current: 1/1
• 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 initializing or resetting a tracking element, comprising:

initializing or resetting, by an inertial tracking system, an initial pose of a first inertial measurement unit (IMU) and a second IMU while the first and second IMUs are temporarily mechanically coupled together in a reproducible reference pose, wherein the initial poses of the first IMU and second IMU are known and achieved when the IMUs are coupled together in the reproducible reference pose;

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

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

resetting the initial pose of the first IMU and the second IMU, thereby eliminating drift caused over time between the tracked pose and the actual pose of the first IMU and second IMU, when the first IMU and the second IMU are returned to the reproducible reference pose.

2. The method of claim 1 wherein the first IMU comprises a first kinematic coupling and the second IMU comprises a second kinematic coupling.

3. The method of claim 2, wherein:

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

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

4. The method of claim 2, wherein the tracked pose of the first IMU and the tracked pose of the second IMU are reset when the kinematic coupling on the first IMU is kinematically coupled to the kinematic coupling on the second IMU.

5. The method of claim 1:

wherein the step of initializing or resetting, by the inertial tracking system, the initial pose of the first and second IMU is automatically initiated by detecting when the first IMU is coupled to the second IMU in the reference pose.

6. The method of claim 5, wherein determining the first IMU and the second IMU are in the reference pose comprises determining the second IMU is kinematically coupled to the first IMU.

7. The method of claim 5 further comprising:

configuring a detection mechanism that includes a state indicator to indicate a coupling of the first and second IMUs based on the detection mechanism.

8. 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 reference pose.

9. The method of claim 1, wherein the 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.

10. The method of claim 1 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 reference pose.

11. The method of claim 1, 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

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

12. The method of claim 1, further comprising:

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

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

initializing or resetting a tracked pose of the first IMU or the second IMU coupled to the third object based on the data.

13. The method of claim 1 further comprising:

affixing a third IMU to the first object to track the first object.

14. The method of claim 1 further comprising:

configuring the first IMU to be kinematically coupled to the second IMU, wherein the kinematic coupling is a self-detecting kinematic assembly.

15. The method of claim 1 further comprising:

configuring a first coupling associated with the first IMU and a second coupling associated with the second IMU to be removably engaged together in a specific geometric configuration to achieve the reference pose.

16. The method of claim 1, wherein the first object and the second object are surgical instruments.

17. The method of claim 1, further comprising:

calculating a transform between the first IMU and the first object; and

calculating a transform between the second IMU and the second object.

18. The method of claim 1, further comprising:

using the tracked poses to track the first object coupled to the first IMU and the second object coupled to the second IMU as the first and second objects are moved independently.

19. A method of initializing or resetting a tracking element, comprising:

moving a first IMU and a second IMU into a reproducible reference pose, wherein the actual pose of the first IMU and the second IMU are known when in the reproducible reference pose;

setting an initial tracked pose of the first IMU and the second IMU when the IMUs are in the reproducible reference pose, such that the tracked poses of the IMUs correspond with the actual poses;

tracking the first IMU and the second IMU based on the initial tracked poses; and

returning the first IMU and the second IMU to the reproducible reference pose to eliminate draft occurring between the actual poses and the tracked poses since the previous setting of the initial tracked pose in the reproducible reference pose.

20. The method of claim 19, wherein the first IMU comprises a first repeatable coupling mechanism and wherein the second IMU comprises a second repeatable coupling mechanism;

wherein the first repeatable coupling mechanism is configured to engage with the second repeatable coupling mechanism; and

wherein moving the first IMU and the second IMU into the reproducible comprises engaging the first repeatable coupling mechanism with the second repeatable coupling mechanism.

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:

initialize or reset, by an inertial tracking system, an initial pose of a first inertial measurement unit (IMU) and a second IMU while the first and second IMUs are temporarily mechanically coupled together in a reproducible reference pose, wherein the initial poses of the first IMU and second IMU are known and achieved when the IMUs are coupled together in the reproducible reference pose;

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

determine, by an inertial tracking system, a tracked pose of the second (IMU) relative to the first IMU wherein the second IMU is mounted to a second object; and

reset the initial pose of the first IMU and the second IMU, thereby eliminating drift caused over time between the tracked pose and the actual pose of the first IMU and second IMU, when the first IMU and the second IMU are returned to the reproducible reference pose.