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

• US 8,352,184 B2
• Filed: 12/21/2006
• Issued: 01/08/2013
• 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.
• Primary Examiner(s): Cheung, Mary
• Assistant Examiner(s): Edwards, Jerrah
• Application Number:
  US11/650,756
• Publication Number:
  US 20080154501A1
• Time in Patent Office: 2,210 Days
• Field of Search: 701/1, 701/14, 701/200, 701/213, 701/220, 701/221, 342/357.12, 342/357.14
• US Class Current: 701/518
• 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, and to generate a variable frequency signal occurring every GPS epoch and correlated to GPS time;

(b) an inertial measurement unit for generating inertial measurement unit information at a first rate corresponding to an attitude for said vehicle in motion, wherein said inertial measurement unit information comprises a plurality of inertial measurement unit signals at said first rate;

(c) a programmable logic device having a first input for receiving said sensor unit information, a second input for receiving said inertial measurement unit information at said first rate, wherein said programmable logic is adapted to execute instructions that, when executed, cause said programmable logic to;

time tag each of said plurality of inertial measurement unit signals at said first rate using said variable frequency signal;

generate a processed inertial measurement unit message stream, wherein said inertial measurement unit message stream is formed of a plurality of processed inertial measurement unit messages at a second rate, wherein said second rate is slower than said first rate, wherein each of said plurality of processed inertial measurement unit messages is formed by integrating a plurality of successive of said plurality of inertial measurement unit signals at said first rate;

generate a TUMS message stream formed of a plurality of TUMS messages, wherein each of said plurality of TUMS messages is generated at a then-current GPS epoch by combining a plurality of said plurality of processed inertial measurement unit messages at said second rate that have been generated since a last GPS epoch with said data stream of sensor unit formation at said current GPS epoch;

(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 signal, 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 signal, 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 ground receiving station;

(j) a kalman filter associated with said ground receiving station;

(k) a receiving telemetry antenna associated with said ground receiving station;

(l) a transmitting telemetry antenna associated with said telemetry processor; and

(m) a telemetry processor adapted to combine said TUMS message stream with an event marker, wherein said event marker is an event record time tagged with GPS time and related to state change of said vehicle in motion.

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) a sensor unit adapted to generate a data stream of information relative to an instantaneous position for a vehicle in motion derived from GPS information obtained from global positioning satellites, and to generate a variable frequency signal correlated to GPS time at a plurality of GPS epochs;

(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, said attitude information comprises a plurality of inertial measurement unit signals at a first rate;

(c) a data formatting logic device adapted to;

time tag each of said plurality of inertial measurement unit signals at said first rate using said variable frequency signal;

generate a processed inertial measurement unit message stream, wherein said inertial measurement unit message stream is formed of a plurality of processed inertial measurement unit messages at a second rate, wherein said second rate is slower than said first rate, wherein each of said plurality of processed inertial measurement unit messages is formed by integrating a plurality of successive of said plurality of inertial measurement unit signals at said first rate; and

generate a TUMS message stream formed of a plurality of TUMS messages, wherein each of said plurality of TUMS messages is generated at a then-current of said plurality of GPS epochs by combining a plurality of said plurality of processed inertial measurement unit messages at said second rate that have been generated since a last of said plurality of GPS epochs with said data stream of sensor unit formation at said then-current of said plurality of GPS epochs;

(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 ground receiving station;

(k) a kalman filter associated with said ground receiving station;

(l) a receiving telemetry antenna associated with said ground receiving station;

(m) a transmitting telemetry antenna associated with said telemetry processor; and

(n) a telemetry processor adapted to combine said TUMS message stream with an event marker, wherein said event marker is an event record time tagged with GPS time and related to state change of said vehicle in motion.

8. The telemetry message formatting system of claim 7, 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.

9. The telemetry message formatting system of claim 7, 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.

10. The telemetry message formatting system of claim 7, 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.

11. The telemetry message formatting system of claim 7, wherein said variable timing frequency is in a range of 1000 Hertz to 2000 Hertz.

12. The telemetry message formatting system of claim 7, 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.

13. The telemetry message formatting system of claim 7, wherein said time space position information unit message is compatible with a packet telemetry system.