System and method to supervise vehicle positioning integrity
A system and method of supervising vehicle positioning of a vehicle along a guideway where the vehicle comprising a supervisory controller, at least two controllers communicatively connected with the supervisory controller, an inertial measurement unit (IMU) and a speed measurement sensor includes receiving, by the controllers, speed measurements from the speed measurement sensor and motion measurements from the inertial measurement unit. The two controllers each estimate the along-track position of the vehicle using a track constrained UKF function based on the received speed measurements and motion measurements. The system executes protection level and protection level supervision functions on the supervisory controller to validate the along-track position estimates. The protection level supervision function uses a Stanford diagram verification technique.
1 . A method of supervising positioning of a vehicle along a guideway, comprising a supervisory controller, first and second controllers communicatively connected with the supervisory controller, a first inertial measurement unit communicatively connected with the first controller, and a second inertial measurement unit communicatively connected with the second controller, a first speed measurement sensor communicatively connected with the first controller and a second speed measurement sensor communicatively connected with the second controller, the method comprising:
receiving, by the first controller, first speed measurements from the first speed measurement sensor, first motion measurements from the first inertial measurement unit, first position data and first-position precision data from a localization sensor and support points from a database;
receiving, by the second controller, second speed measurements from the second speed measurement sensor, second motion measurements from the second inertial measurement unit, second-position data and second position precision data from the localization sensor and the support points from the database;
estimating, by the first controller, first along-track vehicle positions using first track constrained unscented Kalman filter functions based on the first received speed measurements, first motion measurements, the first-position data, the first-position precision data, and the support points;
estimating, by the second controller, second along-track vehicle positions using second track constrained unscented Kalman filter functions based on the second received speed measurements, second motion measurements, the second-position data, the second position precision data, and the support points;
executing protection level and protection level supervision functions on the supervisory controller to validate the first along-track position estimates and second along-track position estimates using a Stanford diagram verification technique and affinity between multiple along-track vehicle position estimates, wherein the first controller and the second controller are executed on computing platforms having a different safety integrity level (SIL) level than the supervisory controller, and the first along-track vehicle position estimates and the second along-track vehicle position estimates are time-stamped; and
operating the vehicle using the first along-track position estimate if the first and second along-track position estimates are validated.
2 . The method of claim 1 , wherein the unscented Kalman filter function estimates the first and the second along-track vehicle positions based on a position determination from a localization sensor.
3 . The method of claim 1 , wherein the unscented Kalman filter function estimates the first and the second along-track vehicle positions of based on support points from a database.
4 . The method of claim 1 , wherein the protection level function is based on an alarm limit value.
5 . The method of claim 1 , wherein the protection level function is based on an integrity risk value.
6 . The method of claim 1 , wherein the first and the second along-track position estimates are averaged to compute an acceptable reference position estimate.
7 . A system of supervising vehicle positioning of a vehicle along a guideway, the system comprising:
a supervisory controller, first and second controllers communicatively connected with the supervisory controller, a first inertial measurement unit communicatively connected with the first controller, and a second inertial measurement unit communicatively connected with the second controller, a first speed measurement sensor communicatively connected with the first controller and a second speed measurement sensor communicatively connected with the second controller,
wherein the first controller is configured to receive first speed measurements from the first speed measurement sensor, first motion measurements of the vehicle from the first inertial measurement unit, first position data and first position precision data from a localization sensor and support points from a database;
wherein the second controller is configured to receive second speed measurements from the second speed measurement sensor, second motion measurements of the vehicle from the second inertial measurement unit, the second position data and the second position precision data from the localization sensor and the support points from the database;
wherein the first controller is configured to estimate a first along-track vehicle position using track constrained unscented Kalman filter functions based on the received first speed measurements, first motion measurements, the first position data, the first position precision data, and the support points and wherein the second controller is configured to estimate a second along-track vehicle position using track constrained unscented Kalman filter functions based on the received second speed measurements, second motion measurements, the second position data, the second position precision data, and the support points;
wherein the supervisory controller is configured to execute protection level and protection level supervision functions on the supervisory controller, the protection level being verified by a Stanford diagram verification technique and the protection level being supervised by affinity between the first and the second along-track vehicle position estimates, and
wherein the first controller and the second controller are executed on computing platforms having a different safety integrity level (SIL) level than the supervisory controller, and the first along-track vehicle position estimates and the second along-track vehicle position estimates are time-stamped.
8 . The system of claim 7 , wherein the supervisory controller is executed on a SIL 4 computing platform.
9 . The system of claim 7 , wherein the first and the second controllers are executed on a SIL 0 computing platform.
10 . The system of claim 7 , wherein the first and the second inertial measurement units provide 3-D acceleration (specific force) and 3-D angular rate measurements.
11 . The system of claim 7 , wherein the first and the second speed measurement sensors are radar.
12 . The system of claim 7 , further comprising a localization sensor communicably connected to the first and second controllers providing position and position precision to the first and second controllers.
13 . The system of claim 7 , further comprising a database communicably connected to the first and the second controllers, providing support points for the unscented Kalman filter functions.
14 . The system of claim 7 , further comprising at least two supervisory controllers wherein output of the two supervisory controllers are compared.
15 . A method of supervising positioning of a vehicle along a guideway, comprising a safety integrity level (SIL) 4 computing platform executing a supervisory controller and a first controller communicatively connected with a first inertial measurement unit and a first speed measurement sensor and a second controller communicatively connected with a second inertial measurement unit and a second speed measurement sensor, the method comprising: determining, using the first controller, a first speed and a first motion direction of the vehicle;
determining, using the second controller, a second speed and a second motion direction of the vehicle;
estimating, using a first controller, a first along-track vehicle position using a track constrained unscented Kalman filter functions based on the determined first speed and first motion direction, first motion measurements from the first inertial measurement unit, and position data and position precision data from a localization sensor and support points from a database;
estimating, using a second controller, a second along-track vehicle position using a track constrained unscented Kalman filter functions based on the determined second speed and second motion direction, second motion measurements from the second inertial measurement unit, and the position data and the position precision data from a localization sensor and support points from a database;
executing protection level functions to generate protection level values and protection level supervision functions to evaluate protection level values on the supervisory controller using Stanford diagram verification technique and affinity between the first and the second along-track vehicle position estimates and validating the first and the second along-track vehicle position estimates, wherein the first controller and the second controller are executed on computing platforms having a different SIL level than the supervisory controller, and the first along-track vehicle position estimates and the second along-track vehicle position estimates are time-stamped; and
operating the vehicle using the first along-track position estimate if the first and the second along-track position estimates are validated.
16 . The method of claim 15 , wherein the unscented Kalman filter function estimates the first and the second along-track vehicle positions based on a position determination from a localization sensor.
17 . The method of claim 15 , wherein the unscented Kalman filter function estimates the first and the second along-track vehicle positions based on support points from a database.
18 . The method of claim 15 , wherein the protection level values are based on an alarm limit value.
19 . The method of claim 15 , wherein the protection level values are based on an integrity risk value.
20 . The method of claim 15 , wherein the protection level values are evaluated by comparison to an alarm limit and position uncertainty.