Method and apparatus for synchronizing multiple magnetic tracking systems

1. A system for allowing two magnetic tracking systems to operate in the same physical environment, comprising:

first and second magnetic tracking systems, each magnetic tracking system comprising;

one or more tracking devices, each tracking device containing a plurality of source magnetic coils configured to generate a magnetic field;

a receiver containing a plurality of sensor magnetic coils configured to sense the magnetic field and generate magnetic sensor data;

a communication link for communicating between the receiver and the one or more tracking devices, and between the first and second magnetic tracking systems, the communication link operating in a manner other than on the generated magnetic field;

a processor configured to:

determine from the communication link whether the magnetic tracking system is a first system of the first and second magnetic tracking systems to be active in the same physical environment;

when the magnetic tracking system is the first of the first and second magnetic tracking systems to be active in the same physical environment:

assign the magnetic tracking system a master identification;

generate and transmit a synchronization signal corresponding to a series of time slots;

sequentially instruct, using the communication link, the one or more tracking devices to each generate a magnetic field during a different time slot in the series of time slots; and

determine that the other of the first and second magnetic tracking systems has requested a slave identification, and assign the other of the first and second magnetic tracking systems a slave identification from which the other of the first and second magnetic tracking systems can determine further sequential time slots during which the one or more tracking devices in the other of the first and second magnetic tracking systems are to generate a magnetic field;

when the magnetic tracking system is not the first of the first and second magnetic tracking systems to be active in the same physical environment:

request, using the communication link, from the other of the first and second magnetic tracking systems a slave identification from which further time slots in the series of time slots for generating a magnetic field can be determined;

receive, using the communication link, from the other of the first and second magnetic tracking systems the synchronization signal; and

sequentially instruct, using the communication link, the one or more tracking devices to each generate a magnetic field during a different time slot in the series of time slots;

and

determine the position and orientation of the one or more tracking devices relative to the receiver from the magnetic sensor data.

2. The system of claim 1 wherein the processor configured to determine whether the magnetic tracking system is the first system of the first and second magnetic tracking systems to be active in the same physical environment by determining whether the other of the first and second magnetic tracking systems is communicating using the communication link.

3. The system of claim 1 wherein the receiver is further configured to be attached to the head of the user.

4. The system of claim 1 wherein the one or more tracking devices are further configured to be attached to limbs of the user.

5. The system of claim 1 wherein the one or more tracking devices are configured to be placed in a location in the same physical environment.

6. The system of claim 1 wherein the communication link is an infrared optical communication device.

7. The system of claim 1 wherein the communication link is a radio frequency communication device.

8. The system of claim 1 wherein the receiver is located in a headset configured to be attached to the user's head.

9. The system of claim 1 wherein each of the one or more tracking devices is located in a handset configured to be attached to a limb of the user.

10. The system of claim 1 wherein the processor is further configured to:

determine, when the magnetic tracking system has been assigned a slave identification, that the processor has not received a synchronization signal for a predetermined period of time;

assign the magnetic tracking system a master identification;

generate and transmit a synchronization signal corresponding to a series of time slots; and

sequentially instruct, using the communication link, the one or more tracking devices to each generate a magnetic field during a different time slot in the series of time slots.

11. The system of claim 1 wherein the processor configured to generate and transmit the synchronization signal is further configured to generate and transmit the synchronization signal at periodic intervals.

12. A method of allowing two magnetic tracking systems to operate in the same physical environment, each magnetic tracking system comprising one or more tracking devices, each tracking device containing a plurality of source magnetic coils configured to generate a magnetic field, a receiver containing a plurality of sensor magnetic coils configured to sense the magnetic field and generate magnetic sensor data, a communication link for communicating between the receiver and the one or more tracking devices, and between the first and second magnetic tracking systems, the communication link operating in a manner other than on the generated magnetic field, and a processor, the method comprising;

determining by the processor from the communication link whether the magnetic tracking system is a first system of the first and second magnetic tracking systems to be active in the same physical environment;

when the magnetic tracking system is the first of the first and second magnetic tracking systems to be active in the same physical environment:

assigning, by the processor, the magnetic tracking system a master identification;

generating and transmitting a synchronization signal corresponding to a series of time slots;

sequentially instructing, by the processor using the communication link, the one or more tracking devices to each generate a magnetic field during a different time slot in the series of time slots; and

determining by the processor that the other of the first and second magnetic tracking systems has requested a slave identification, and assign the other of the first and second magnetic tracking systems a slave identification from which the other of the first and second magnetic tracking systems can determine further sequential time slots during which the one or more tracking devices in the other of the first and second magnetic tracking systems are to generate a magnetic field;

when the magnetic tracking system is not the first of the first and second magnetic tracking systems to be active in the same physical environment:

requesting by the processor from the other of the first and second magnetic tracking systems a slave identification from which further sequential time slots for generating a magnetic field can be determined;

receiving, using the communication link, from the other of the first and second magnetic tracking systems the synchronization signal; and

instructing, by the processor using the communication link, the one or more tracking devices to sequentially generate a magnetic field during the determined further sequential time slots;

and

determining by the processor the position and orientation of the one or more tracking devices on the user relative to the receiver from the magnetic sensor data.

13. The method of claim 12 wherein determining by the processor whether the magnetic tracking system is the first system of the first and second magnetic tracking systems to be active in the same physical environment is done by determining whether the other of the first and second magnetic tracking systems is communicating using the communication link.

14. The method of claim 12 wherein the receiver is further configured to be attached to the head of the user.

15. The method of claim 12 wherein the one or more tracking devices are further configured to be attached to limbs of the user.

16. The method of claim 12 wherein the one or more tracking devices are further configured to be placed in a location in the same physical environment.

17. The method of claim 12 wherein the communication link is an infrared optical communication device.

18. The method of claim 12 wherein the communication link is a radio frequency communication device.

19. The method of claim 12 wherein the receiver is located in a headset configured to be attached to the head of the user.

20. The method of claim 12 wherein each of the one or more tracking devices is located in a handset configured to be attached to a limb of the user.

21. The method of claim 12 further comprising:

determining, when the magnetic tracking system has been assigned a slave identification, that the processor has not received a synchronization signal for a predetermined period of time:

assigning the magnetic tracking system a master identification;

generating and transmitting a synchronization signal corresponding to a series of time slots; and

sequentially instructing, using the communication link, the one or more tracking devices to each generate a magnetic field during a different time slot in the series of time slots.

22. The method of claim 12 , further comprising generating and transmitting, by the processor, the synchronization signal at periodic intervals.

23. A non-transitory computer readable storage medium having embodied thereon instructions for causing a computing device to execute a method of allowing two magnetic tracking systems to operate in the same physical environment, each magnetic tracking system comprising one or more tracking devices, each tracking device containing a plurality of source magnetic coils configured to generate a magnetic field, a receiver containing a plurality of sensor magnetic coils configured to sense the magnetic field and generate magnetic sensor data, a communication link for communicating between the receiver and the one or more tracking devices on the user, and between the first and second magnetic tracking systems, the communication link operating in a manner other than on the generated magnetic field, and a processor, the method comprising:

determining by the processor from the communication link whether the magnetic tracking system is a first system of the first and second magnetic tracking systems to be active in the same physical environment,

when the magnetic tracking system is the first of the first and second magnetic tracking systems to be active in the same physical environment:

assigning, by the processor, the magnetic tracking system a master identification;

generating and transmitting a synchronization signal corresponding to a series of time slots;

sequentially instructing, by the processor using the communication link, the one or more tracking devices to each generate a magnetic field during a different time slot in the series of time slots; and

determining by the processor that the other of the first and second magnetic tracking systems has requested a slave identification, and assign the other of the first and second magnetic tracking systems a slave identification from which the other of the first and second magnetic tracking systems can determine further sequential time slots during which the one or more tracking devices in the other of the first and second magnetic tracking systems are to generate a magnetic field; when the magnetic tracking system is not the first of the first and

second magnetic tracking systems to be active in the same physical environment:

requesting by the processor from the other of the first and second magnetic tracking systems a slave identification from which further sequential time slots for generating a magnetic field can be determined;

receiving, using the communication link, from the other of the first and second magnetic tracking systems the synchronization signal, and

instructing, by the processor using the communication link, the one or more tracking devices to sequentially generate a magnetic field during the determined further sequential time slots; and determining by the processor the position and orientation of the one or more tracking devices on the user relative to the receiver from the magnetic sensor data.