System and method to determine low-speed and stationary state of a rail vehicle

1. A system for determining a stationary state of a rail vehicle on a track, comprising:

a first radar mounted at an end of the rail vehicle, wherein the first radar measures a first velocity of the rail vehicle;

a second radar mounted at another end of the rail vehicle, wherein the second radar measures a second velocity of the rail vehicle;

a wheel mounted speed sensor mounted on the rail vehicle, wherein the wheel mounted sensor measures a third velocity of the rail vehicle;

a series of fixed reflective track features along the track; and

a processing unit, communicably connected with the speed sensor, the first radar and the second radar;

wherein the processing unit is configured to receive data from the first radar corresponding to a first distance to one of the fixed reflective track features to determine a first displacement and to receive data from the second radar corresponding to a second distance to another one of the fixed reflective track features to determine a second displacement;

and wherein the processing unit is configured to determine the rail vehicle is in a stationary state responsive to the first velocity, and the second velocity and third velocity being less than a predetermined threshold velocity and the first displacement and the second displacement being less than a predetermined threshold displacement.

2. The system of claim 1 , wherein the first radar and the second radar use a range-to-target measurement technology to measure vehicle motion at low speed.

3. The system of claim 1 , wherein the reflective elements are one or more of at least a portion of a track, a signal post, a metal beam, a switch element.

4. The system of claim 1 , wherein the system is configured to determine a low-speed condition.

5. The system of claim 1 , wherein the first radar and the second radar each have a field of view that includes a distance of three meters.

6. The system of claim 1 , wherein the first radar and the second radar each have a field of view that includes a distance of fifty meters.

7. The system of claim 1 , wherein the first radar and the second radar are configured to measure relative, with respect to the reflective elements, radial speed of the vehicle.

8. The system of claim 7 , wherein the first radar and the second radar are configured to use Doppler frequency shift to measure relative radial speed.

9. The system of claim 1 , wherein the first radar and the second radar are configured to measure radial range between the radar and the reflective element.

10. The system of claim 1 , wherein the first radar and the second radar are configured to use round trip time of flight to measure the radial range.

11. A method of detecting a stationary state of a rail vehicle on a track comprising the steps of:

detecting fixed metallic reflective track features along the track using radar signals; and

determining a first velocity of the rail vehicle using a first radar;

determining a second velocity of the rail vehicle using a second radar;

determining a third velocity of the rail vehicle using a wheel mounted speed sensor;

determining a first displacement using the first radar to measure a first distance to a fixed metallic track feature;

determining a second displacement using a second radar to measure a second distance to another fixed metallic track feature;

determining the rail vehicle is in a stationary state responsive to the first velocity, and the second velocity and third velocity being less than a predetermined threshold velocity and the first displacement and the second displacement being less than a predetermined threshold displacement.

12. The method of claim 11 , wherein the first radar and the second radar use a range-to-target measurement technology to measure vehicle motion at low speed.

13. The method of claim 11 , further including the step of detecting the speed of the vehicle using an inertial speed sensor, wherein the inertial speed sensor is an inertial measurement unit.

14. The method of claim 11 , wherein the first radar and the second radar are frequency modulated continuous wave radars.

15. The method of claim 12 wherein the first radar is mounted at one end of the vehicle and the second radar is mounted at the other end of the vehicle.

16. The method of claim 11 , wherein the reflective elements are one or more of at least a portion of a track, a signal post, a metal beam, a switch element.

17. A method of determining a stationary state of a rail vehicle on a track, comprising the steps of:

measuring a first velocity and a first displacement of the rail vehicle using a first radar by detecting fixed metallic reflective track features;

measuring a second velocity and a second displacement of the rail vehicle using a second radar by detecting fixed metallic reflective track features;

measuring a third velocity using a wheel mounted speed sensor; and

determining the rail vehicle is in a stationary state responsive to the first velocity, and the second velocity and third velocity being less than a predetermined threshold velocity and the first displacement and the second displacement being less than a predetermined threshold displacement.

18. The method of claim 17 , further comprising measuring an acceleration of the rail vehicle using an inertial measurement unit and determining the rail vehicle is in a non-stationary state responsive to the acceleration being greater than a predetermined threshold acceleration.

19. The method of claim 17 , further comprising determining a rail vehicle is in a non-stationary state responsive to the first velocity or the second velocity being greater than a predetermined threshold velocity.

20. The method of claim 17 , further comprising determining a rail vehicle is in a non-stationary state responsive to the first displacement or the second displacement being greater than a predetermined threshold displacement.