Method and system for positional measurement using ultrasonic sensing

• US 8,000,926 B2
• Filed: 04/20/2010
• Issued: 08/16/2011
• Est. Priority Date: 11/28/2005
• Status: Expired due to Fees

• Current Assignee: OrthoSensor, Inc (Stryker Corporation)
• Original Assignee: OrthoSensor, Inc (Stryker Corporation)
• Inventors: Roche, Martin, McIntosh, Jason, Boillot, Marc
• Primary Examiner(s): Dunn; Drew A
• Assistant Examiner(s): Henson; Mi'schita′
• Application Number:
  US12/764,072
• Publication Number:
  US 20100204955A1
• Time in Patent Office: 483 Days
• Field of Search: 702/66, 702/72, 702/159
• US Class Current: 702/159
• CPC Class Codes: A61B 2034/2063 Acoustic tracking systems, e.g. using ultrasound
• CPC Class Codes: A61B 2090/3925 ultrasonic
• CPC Class Codes: A61B 2090/3983 Reference marker arrangements for use with image guided surgery
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis

Abstract

A method for determining position and alignment is provided. The method includes monitoring a first and second sequence of ultrasonic signals transmitted from the first device to a second device, estimating a location of the first device from Time of Flight measurements of the ultrasonic signals at respective microphones on the second device, calculating a set of phase differences, weighting a difference of an expected location and estimated location of the first device with the set of phase differences to produce a relative displacement, and reporting a position of the first device based on the relative displacement.

Claims

1. A system for positional measurements, comprising:

an ultrasonic transmitter on a first device for transmitting at a first location a first sequence of ultrasonic signals through air;

a receiver on a second device for capturing the first sequence of ultrasonic signals and a second sequence of ultrasonic signals transmitted by the ultrasonic transmitter on the first device during movement to a second location;

a phase detector on the second device operatively coupled to the receiver for identifying a series of phase differences between the first sequence of ultrasonic signals and the second sequence of ultrasonic signals; and

a processor on the second device operatively coupled to the phase detector and a sensing unit comprising the receiver for updating an expected location of the first device using the series of phase differences, wherein the processor;

measures a first series of Time of Flights (TOF) between the transmitting of the first sequence of ultrasonic signals and the capturing of the second sequence of ultrasonic signals, and producing therefrom the expected location of the first device at the first location,

measures a second series of Time of Flights (TOF) between the transmitting of the first sequence of ultrasonic signals and the capturing of the second sequence of ultrasonic signals, and producing therefrom an estimated location of the first device at the second location,

determines a relative displacement of the first device by weighting a difference of the expected location and estimated location with the phase difference, and

reports a position of the first device in accordance with the relative displacement

wherein the estimated location is determined from the second series of Time of Flight (TOF) measurements, and the relative displacement is evaluated within an error region determined from a series of differential time of flight (dTOF) measurements.

2. The system of claim 1, wherein the processor applies a weighted average to a history of estimated locations for determining the expected location.

3. The method of claim 1, where the processor:

saves to memory three or more location points of the first device at different times; and

reports an alignment of the three or more points of the first device at different times.

4. The system of claim 1, wherein the processor reports an orientation of the first device at the position.

5. The system of claim 1, wherein the processor modifies a timing sequence of the ultrasonic signals transmitted from the first device based on a detected acceleration of the first device.

6. A system for positional measurements, comprising:

an ultrasonic transmitter on a first device for transmitting at a first location a first sequence of ultrasonic signals through air, and

a receiver on a second device for receiving the first sequence of ultrasonic signals and thereafter receiving a second sequence of ultrasonic signals transmitted by the ultrasonic transmitter on the first device;

a phase detector on the second device operatively coupled to the receiver for identifying a series of phase differences between the first sequence of ultrasonic signals and the second sequence of ultrasonic signals; and

a processor operatively coupled to the phase detector and a sensing unit comprising the receiver to;

measure a first series of Time of Flights (TOF) for the first sequence of received ultrasonic signals to produce an expected location of the first device at a first location,

measure a second series of Time of Flights (TOF) for the second sequence of received ultrasonic signals to produce an estimated location of the object at a second location,

apply a weighted difference of the expected location and the estimated location to the phase difference to produce a relative displacement,

update the expected location of the first device with the relative displacement, and

report the expected location of the first device

wherein the processor identifies the estimated location of the first device, and determines if the estimated location is within a region of relative displacement error of the expected location determined from differential time of flight (dTOF) measurements in view of the phase difference.

7. The input device of claim 6, wherein the processor determines the relative displacement of the object in view of the phase difference, the estimated location, and the expected location.

8. The input device of claim 6, wherein the processor

saves to memory three or more location points of the first device at different times;

and

reports an alignment of the three or more points of the first device at different times.

9. The input device of claim 6, wherein the processor reports an orientation of the first device at the expected location.

10. A method performed by a processor for resolving movement and position, the method comprising the steps of:

monitoring a movement of a first device from a first sequence of Time of Flight (TOF) measurements from ultrasonic signals transmitted from the first device to a second device that includes the processor to produce an expected location of the first device;

estimating a location of the first device to produce an estimated location from a second sequence of Time of Flight (TOF) measurements from ultrasonic signals transmitted from the first device to the second device;

calculating a set of phase differences between the first sequence of Time of Flight (TOF) measurements and the second sequence of Time of Flight (TOF) measurements;

weighting a difference of the expected location and estimated location with the set of phase differences to produce a relative displacement of the first device;

updating the expected location of the first device in view of the estimated location with the relative displacement; and

reporting a position of the first device at the expected location by

determining if the estimated location is within a region of the relative displacement of the expected location in view of the set of phase differences; and

,

if so, updating the expected location with a weighted difference of the estimated location and the relative displacement;

if not, updating the expected location with the relative displacement.

11. The method of claim 10 comprising:

saving to memory three or more location points of the first device at different times; and

reporting an alignment of the three or more points of the first device at different times.

12. The method of claim 10, comprising transmitting a plurality of ultrasonic signals from the first device at staggered time intervals to produce the sequence.

13. The method of claim 10, comprising transmitting a plurality of ultrasonic signals from the first device at a same time to produce the sequence.

14. The method of claim 10, further comprising performing a time weighted average of expected locations for updating the relative displacement.

15. The method of claim 14, further comprising modifying a timing sequence of the ultrasonic signals transmitted from the first device based on a detected acceleration of the first device.