Message formatting system to improve GPS and IMU positional reporting for a vehicle

• US 20080154501A1
• Filed: 12/21/2006
• Published: 06/26/2008
• Est. Priority Date: 12/21/2006
• Status: Active Grant

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Meyer, Steven J.
• Granted Patent: US 8,352,184 B2
• Time in Patent Office: Days
• US Class Current: 701/213
• CPC Class Codes: G01S 19/49 whereby the further system is an inertial position system, e.g. loosely-coupled
• CPC Class Codes: G01S 5/0018 Transmission from mobile station to base station

Abstract

The invention generally relates to a system for generating and transmitting a telemetry formatted message containing raw Global Positioning System (GPS) information, processed Inertial Measurement Unit (IMU) information corresponding to the position and attitude of a high speed vehicle in motion. This telemetry formatted message is received on the ground and used to improve Kalman filter operation. In particular, the telemetry formatted message is used as an input to a ground based Kalman filter that is set to track and predict the trajectory of the high speed vehicle. The telemetry formatted message content improves the overall operation of the Kalman filter by preventing Kalman filter resets that occur when a bit error is encountered in the IMU data and improves the time correlation of high data rate IMU information and low data rate GPS information, both necessary for accurate tracking of the high speed vehicle.

Claims

1. A telemetry message formatting system for producing correlated positional information comprising:

(a) a global positioning system sensor unit for generating a data stream of sensor unit information corresponding to a position for a vehicle in motion;

(b) an inertial measurement unit for generating inertial measurement unit information corresponding to an attitude for said vehicle in motion;

(c) a data formatting processor having a first input for receiving said sensor unit information, a second input for receiving said inertial measurement unit information and an output port connected to the input of a telemetry processor;

(d) an interface circuit having a plurality of input ports connected to said inertial measurement unit and an output port connected to a third input of said data formatting processor;

(e) a clock circuit for generating a stable clock, said clock circuit connected to a fourth input of said data formatting processor input;

(f) a flash memory controller having a clock input for receiving said stable clock, a communications port for receiving control signals from said data formatting processor and status information from a flash memory device;

(g) a differential buffer circuit located within said data formatting processor, said differential buffer circuit having an input port for receiving externally generated event markers and an output connected to said telemetry processor;

(h) a power conditioner having an input for receiving an external power waveform from said vehicle in motion, said power conditioner providing internal power waveforms compatible with said global positioning system sensor unit, with said inertial measurement unit, with said data formatting processor, with said interface circuit, with said clock circuit, with said flash memory controller, with said flash memory device and with said differential buffer circuit;

(i) a variable frequency signal generated by said global positioning system sensor unit wherein said data formatting processor has a fifth input to receive said variable frequency signal; and

(j) a time space position information unit message generated by said data formatting processor wherein said time space position information unit message includes global positioning system sensor unit positional information correlated in time with said inertial measurement unit attitude information, wherein said data formatting processor transmits said time space position information unit message to said telemetry processor.

2. The telemetry message formatting system of claim 1, wherein said data formatting processor is a programmable logic device having a plurality of universal asynchronous receiver transmitter ports, a plurality of parallel input output ports, an internal random access memory, an internal read only memory, a plurality of interrupt request ports and a soft core processor.

3. The telemetry message formatting system of claim 1, wherein said interface circuit is further comprised of an analog to digital converter for converting analog signals received from said inertial measurement unit to a digital signal transmitted to said data formatting processor.

4. The telemetry message formatting system of claim 1, wherein said time space position information unit message is further comprised of a plurality of fields, wherein a first field contains a status word, a second field contains said data stream of sensor unit information time correlated with said inertial measurement unit information residing in a third field.

5. The telemetry message formatting system of claim 1, wherein said variable frequency signal is in the range of 1000 Hertz to 2000 Hertz.

6. The telemetry message formatting system of claim 1, wherein said time space position information unit message is compatible with a packet telemetry system.

7. A telemetry message formatting system for producing correlated positional information comprising:

(a) means for generating a serial data stream of information corresponding to a position for a vehicle in motion using information obtained from global positioning satellites;

(b) means for generating attitude information corresponding to the motion of said vehicle in motion;

(c) data formatting processing means for receiving said serial data stream of information and for receiving said attitude information, said data formatting processing means having an output connected to the input of a telemetry processing means;

(d) electronic interface means for receiving the analog signal output from said means for generating attitude information, said electronic interface means having a digital signal output connected to said data formatting processing means;

(e) timing synchronization means connected to said data formatting processing means and connected to telemetry message formatting system components to facilitate the coordination of time critical operations;

(f) controller means for reading applications software from a flash memory means and writing said applications software to a memory internal to said data formatting processing means;

(g) buffer means for receiving event markers generated by devices which are external to said telemetry message formatting system, said buffer means having an output connected to said telemetry processing means;

(h) power conditioning means for converting voltage waveforms generated by said vehicle to voltage waveforms compatible with said means for generating said serial data stream, with said means for generating said attitude information, with said data formatting processing means, with said electronic interface means, with said timing synchronization means, with said controller means and with said buffer means;

(i) a variable timing frequency signal generated by said means for generating said serial data stream, wherein said means for generating said serial data stream is connected to an input of said data formatting processing means;

(j) a message structure means containing positional information corresponding to said vehicle in motion wherein said message structure means is generated by said data formatting processing means for output to said telemetry processing means.

8. The telemetry message formatting system of claim 7, wherein said data formatting processing means is a programmable processing means having a plurality of universal asynchronous receiver transmitter means, a plurality of parallel input outputs, an internal random access memory means, an internal read only memory means, and a plurality of interrupt request means, each of which is connected to central processing means internal to said programmable processing means.

9. The telemetry message formatting system of claim 7, wherein said electronic interface means is further comprised of an input for receiving high data rate analog signals from said means for generating said attitude information and having a digital output connected to said data formatting processing means.

10. The telemetry message formatting system of claim 7, wherein said message structure means is further comprised of a telemetry message formatting system status word resident in a first field and a second field representing said means for generating said serial data stream which is time correlated with data generated by said means for generating said attitude information resident in a third field.

11. The telemetry message formatting system of claim 7, wherein said timing synchronization means operates in a range of 1000 Hertz to 2000 Hertz.

12. The telemetry message formatting system of claim 7, wherein said message structure means is compatible with a packet telemetry system.

13. A telemetry message formatting system for producing correlated positional information comprising:

(a) a sensor unit for producing a data stream of information relative to an instantaneous position for a vehicle in motion derived from GPS information obtained from global positioning satellites;

(b) an inertial measurement unit attached to said vehicle in motion, said inertial measurement unit producing attitude information corresponding to instantaneous angular and linear accelerations of said vehicle in motion;

(c) a data formatting logic device for storing and processing said data stream of information, for storing and processing said attitude information, and for time correlating said data stream of information with said attitude information, said data formatting logic device having an output connecting said data formatting logic device to a telemetry processor;

(d) an electronic interface for converting analog signals received from said inertial measurement unit to a digital word supplied to said data formatting logic device;

(e) a variable frequency signal output by said sensor unit for time tagging said attitude information sent to said data formatting logic device from said inertial measurement unit;

(f) a flash memory controller for reading applications software from a flash memory and writing said applications software to a random access memory which is internal to said data formatting logic device;

(g) a differential buffer circuit having an input for receiving and buffering an event marker, said differential buffer having an output connecting said differential buffer circuit to said telemetry processor;

(h) a system clock for providing synchronization of time critical operations within said telemetry message formatting system;

(i) a power conditioner for converting vehicle power waveforms to a plurality of power waveforms to operate said sensor unit, said inertial measurement unit, said data formatting processing logic device, said electronic interface, said system clock, said flash memory controller and said differential buffer circuit; and

(j) a time space position information unit message generated by said data formatting logic device, wherein said time space position information unit message includes a plurality of data structures containing said data stream of information time correlated with said attitude information.

14. The telemetry message formatting system of claim 13, wherein said data formatting logic device is a programmable system on a chip having a plurality of universal asynchronous receiver transmitter circuits, a plurality of parallel input output circuits, said internal random access memory, an internal read only memory, a plurality of interrupt request circuits each of which are connected to a central processing unit.

15. The telemetry message formatting system of claim 13, wherein said electronic interface circuit is further comprised of a sample and hold input circuit for receiving high data rate analog signals from said inertial measurement unit, said sample and hold circuit having a digital signal output to provide error free inertial measurement data to said data formatting logic device.

16. The telemetry message formatting system of claim 13, wherein said time space position information unit message is further comprised of a first data structure containing status of electronic components within said telemetry message formatting system, a second data structure containing said data stream of information time correlated with said attitude information residing in a third data structure.

17. The telemetry message formatting system of claim 13, wherein said variable timing frequency is in a range of 1000 Hertz to 2000 Hertz.

18. The telemetry message formatting system of claim 13, wherein said data formatting logic device mathematically integrates high data rate inertial measurement unit messages to obtain error free medium data rate inertial measurement unit messages.

19. The telemetry message formatting system of claim 13, wherein said time space position information unit message is compatible with a packet telemetry system.