Automotive navigation system and method to utilize internal geometry of sensor position with respect to rear wheel axis

• US 9,026,263 B2
• Filed: 11/30/2011
• Issued: 05/05/2015
• Est. Priority Date: 11/30/2011
• Status: Active Grant

• Current Assignee: Alpine Electronics Incorporated (Alps Alpine Co., Ltd.)
• Original Assignee: Alpine Electronics Incorporated (Alps Alpine Co., Ltd.)
• Inventors: Hoshizaki, Takayuki
• Primary Examiner(s): Jabr, Fadey
• Assistant Examiner(s): Mahne, Kevin P
• Application Number:
  US13/307,399
• Publication Number:
  US 20130138264A1
• Time in Patent Office: 1,252 Days
• Field of Search: 342/357.23, 342/357.64, 342/357.31, 701/1, 701/25, 701/28, 701/301, 701/31.4, 701/36, 701/38, 701/41, 701/42, 701/46, 701/444, 701/469, 701/470, 701/472, 701/478.5, 701/480, 701/50, 701/500, 701/501, 701/507, 701/51, 701/510, 701/523, 701/532, 701/533, 701/70, 340/441, 340/932.2, 702/94, 702/95, 73/13.7, 731/46
• US Class Current: 701/1
• CPC Class Codes: B60G 17/019 characterised by the type of sensor or the arrangement thereof B60G17/01941 takes precedence
• CPC Class Codes: G01C 21/005 with correlation of navigation data from several sources, e.g. map or contour matching G01C21/30 takes precedence
• CPC Class Codes: G01C 21/12 executed aboard the object being navigated; Dead reckoning
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01C 21/1652 with ranging devices, e.g. LIDAR or RADAR
• CPC Class Codes: G01C 21/1656 with passive imaging devices, e.g. cameras
• CPC Class Codes: G01C 21/166 Mechanical, construction or arrangement details of inertial navigation systems
• CPC Class Codes: G01C 21/188 for accumulated errors, e.g. by coupling inertial systems with absolute positioning systems
• CPC Class Codes: G01C 21/26 specially adapted for navigation in a road network
• CPC Class Codes: G01C 21/28 with correlation of data from several navigational instruments

Abstract

A navigation system and method to utilize the internal geometry of the sensor position with respect to the vehicle'"'"'s rear-wheel axis for maintaining high positioning accuracy even when GPS signals are lost for a long period of time are disclosed. One aspect is to use an analytical condition derived from a vehicle'"'"'s mechanical condition so-called Ackermann Steering Geometry for enhancement in navigation accuracy. The analytical condition is a relationship between the vehicle'"'"'s lateral directional velocity, the distance of the sensor position with respect to the rear wheel axis, and the angular rate with respect to the vehicle'"'"'s z-axis. Another aspect is to incorporate the distance of the sensor position with respect to the rear wheel axis into the INS and Kalman filter'"'"'s states as an auxiliary parameter.

Claims

1. An integrated INS/GPS navigation system for a vehicle to track a position of the vehicle, comprising:

an inertial measurement unit (IMU) including micro-electro mechanical systems (MEMS) sensors configured to measure acceleration and angular rate of the vehicle;

an inertial navigation system (INS) configured to produce vehicle'"'"'s state estimates based on the acceleration and angular rate measurement from the IMU;

an auxiliary measurement (Aux) unit configured to produce auxiliary measurement data involving an analytical condition derived from a vehicle'"'"'s mechanical condition;

a global positioning system (GPS) unit configured to receive GPS satellite signals from a plurality of GPS satellites via a GPS antenna to produce GPS measurement outputs indicating an absolute position and velocity of the vehicle;

a Kalman filter which combines the state estimates of the INS, the auxiliary measurement data of the Aux unit, and the GPS measurement outputs of the GPS unit and performs a Kalman filter processing thereon; and

a display configured to visually produce the vehicle position derived from the position estimates by the INS and Kalman filter;

wherein the analytical condition incorporated in the Aux unit is represented by a first equation of “

0=v_by−

dω

_bz”

, where the first equation defines a relationship among “

V_by”

representing a vehicle'"'"'s lateral directional velocity, “

d”

representing a distance between the MEMS sensors and a vehicle'"'"'s rear wheel axis, and “

ω

_bz”

representing an angular rate with respect to a vehicle'"'"'s z-axis, and

wherein the distance “

d”

of the MEMS sensors from the rear wheel axis is incorporated into the state estimates of the INS and the Kalman filter processing as an auxiliary parameter so that the navigation system can automatically estimate the distance “

d”

between the MEMS sensors and the rear wheel axis by the Kalman filter processing based on the auxiliary measurement data “

z₁”

produced by the Aux unit as a second equation of “

z₁=v_by−

dω

_bz”

.

2. The integrated INS/GPS navigation system as defined in claim 1, wherein the Kalman filter continuously utilizes the analytical condition from the Aux unit as auxiliary measurement to calibrate the state estimates at a high frequency executed independently of the GPS measurement outputs.

3. The integrated INS/GPS navigation system as defined in claim 1, wherein the distance of the MEMS sensors from the rear wheel axis is set to zero by mounting the IMU at the point on the rear wheel axis thereby achieving the highest positioning accuracy.

4. The integrated INS/GPS navigation system as defined in claim 3, wherein the distance of the MEMS sensors from the rear wheel axis is set to zero by mounting the IMU at the bottom of a rear trunk of a vehicle which is approximately above the rear wheel axis for majority of vehicles.

5. The integrated INS/GPS navigation system as defined in claim 1, wherein the analytical condition is derived from a mechanical condition of the vehicle which is called Ackermann Steering Geometry.

6. The integrated INS/GPS navigation system as defined in claim 1, further comprising a navigation operation unit including a map database configured to implement an overall operation of the navigation system which specifies a destination, searches and calculates an optimum route to the destination, conducts the route guidance operation to the destination, wherein the navigation operation unit conducts a map matching process with respect to the position estimates from the INS and Kalman filter with position information retrieved from a map database.

7. The integrated INS/GPS navigation system as defined in claim 6, wherein the display shows a vehicle contour and navigation system'"'"'s position with proper geometry between the vehicle contour and navigation system'"'"'s position in which a distance between the navigation system and the rear wheel axis is automatically estimated, and wherein the navigation system'"'"'s estimated absolute position (latitude, longitude, (and altitude if necessary)) and position information from the map database are aligned by placing the GPS antenna right above the navigation system.

8. The integrated INS/GPS navigation system as defined in claim 7, wherein the display shows the vehicle contour, navigation system'"'"'s position with respect to the vehicle contour, and images of objects surrounding the vehicle, based on the map matching process of the navigation operation unit.

9. A computer-implemented method of an integrated INS/GPS navigation system for a vehicle to track a position of the vehicle, comprising the following steps of:

measuring acceleration and angular rate of the vehicle by using a processor in an inertial measurement unit (IMU) which includes micro-electro mechanical systems (MEMS) sensors;

producing vehicle'"'"'s state estimates by an inertial navigation system (INS) based on the acceleration and angular rate measurement from the IMU;

producing auxiliary measurement data involving an analytical condition derived from a vehicle'"'"'s mechanical condition by an auxiliary measurement (Aux) unit;

producing GPS measurement outputs indicating an absolute position and velocity of the vehicle by a global positioning system (GPS) unit which receives GPS satellite signals from a plurality of GPS satellites via a GPS antenna;

performing a Kalman filter processing by a Kalman filter on the state estimates of the INS, the auxiliary measurement data of the Aux unit, and the GPS measurement outputs of the GPS unit; and

displaying a vehicle position derived from the position estimates by the INS and Kalman filter;

wherein the analytical condition incorporated in the Aux unit is represented by a first equation of “

0=v_by−

dω

_bz”

, where the first equation defines a relationship among “

v_by”

representing a vehicle'"'"'s lateral directional velocity, “

d”

representing a distance between the MEMS sensors and a vehicle'"'"'s rear wheel axis, and “

ω

_bz”

representing an angular rate with respect to a vehicle'"'"'s zB axis, and

wherein the distance “

d”

of the MEMS sensors from the rear wheel axis is incorporated into the state estimates and the INS in the Kalman filter processing as an auxiliary parameter so that the navigation system can automatically estimate the distance “

d”

between the MEMS sensors and the rear wheel axis by the Kalman filter processing based on the auxiliary measurement data “

z₁”

produced by the Aux unit as a second equation of “

z₁=v_by−

dω

_bz”

.

10. The method of the integrated INS/GPS navigation system as defined in claim 9, wherein the Kalman filter continuously utilizes the analytical condition from the Aux unit as auxiliary measurement to calibrate the position estimates at a high frequency executed independently of the GPS measurement outputs.

11. The method of the integrated INS/GPS navigation system as defined in claim 9, wherein the distance of the MEMS sensors from the rear wheel axis is set to zero by mounting the IMU on the rear wheel axis thereby achieving the highest positioning accuracy.

12. The method of the integrated INS/GPS navigation system as defined in claim 11, wherein the distance of the MEMS sensors from the rear wheel axis is set to zero by mounting the IMU at the bottom of a rear trunk of a vehicle which is approximately above the rear wheel axis for majority of vehicles.

13. The method of the integrated INS/GPS navigation system as defined in claim 9, wherein the analytical condition is derived from a mechanical condition of the vehicle which is called Ackermann Steering Geometry.

14. The method of the integrated INS/GPS navigation system as defined in claim 9, further comprising a step of implementing an overall operation of the navigation system for specifying a destination, searching and calculating an optimum route to the destination, conducting the route guidance operation to the destination, wherein the overall operation includes a step of conducting a map matching process with respect to the position estimates from the INS and Kalman filter with position information retrieved from a map database.

15. The method of the integrated INS/GPS navigation system as defined in claim 14, wherein the display shows a vehicle contour and navigation system'"'"'s position with proper geometry between the vehicle contour and navigation system'"'"'s position in which a distance between the navigation system and the rear wheel axis is automatically estimated, and wherein the navigation system'"'"'s estimated absolute position (latitude, longitude, (and altitude if necessary)) and position information from the map database are aligned by placing the GPS antenna right above the navigation system.

16. The method of the integrated INS/GPS navigation system as defined in claim 15, wherein the display shows the vehicle contour, navigation system'"'"'s position with respect to the vehicle contour, and images of objects surrounding the vehicle, based on the map matching process.