Doppler sensor for the derivation of torsional slip, friction and related parameters

1. A method for measuring properties of a travel vehicle relative to a travel surface, upon which the travel vehicle travels, comprising:

providing an incident light from a light source to the travel surface;

collecting light reflected from the travel surface;

determining a surface induced Doppler shift from the incident and collected light; and

determining at least a motion property of the travel vehicle based on the determined surface induced Doppler shift by determining a torsional slip of a rotating surface of a contact between the travel vehicle and the travel surface.

2. A method for measuring torsional slip, comprising:

measuring a tangential velocity of a surface rotating about an axis via a Doppler shifted return of a first laser beam;

measuring a translational velocity of the axis via a Doppler shifted return of a second laser beam; and

deriving a torsional slip of the rotating surface from the difference between the tangential velocity and the translational velocity.

3. A method as in claim 2 , wherein the rotating surface is a drive surface of a wheel mounted on an axle of a vehicle carriage, the axle being the axis.

4. A method as in claim 3 , wherein the wheel is a steel wheel of a locomotive.

5. method as in claim 3 , wherein the first and second laser beams are generated by respective optical units mounted on said vehicle carriage, the first laser beam being directed to a rotating side surface of the wheel and the second laser beam being directed to a surface being driven by said wheel.

6. A method as in claim 4 , wherein the first and second laser beams are generated by respective optical units mounted at trackside, the first laser beam being directed to a rotating side surface of the wheel and the second laser beam being directed to an axle mount of the wheel.

7. A method as in claim 5 , wherein the Doppler shifted return of the first laser beam is used to calculate the angular velocity of the wheel, and the tangential velocity is calculated from the angular velocity and a radius of the wheel.

8. A method as in claim 2 , further comprising extracting a measurement of a wheel diameter the torsional characteristics and velocity characteristics.

9. A method as in claim 2 , further comprising extracting a frictional value from the torsional slip of the rotating surface.

10. A method for measuring torsional slip, comprising:

using first and second laser beams to simultaneously generate respective first and second Doppler shifted return beams from a first surface rotating about an axis and from a second surface, wherein movement of the second surface corresponds to the translational velocity of the axis;

processing the respective Doppler shifted return beams to determine, respectively, a tangential velocity of the rotating surface and a translational velocity of the axis; and

deriving the torsional slip of the rotating surface from the difference between the tangential velocity and the translational velocity.

11. A method as in claim 10 , wherein the rotating surface is a side surface of a wheel mounted on an axle of a vehicle carriage, the axle being the axis.

12. A method as in claim 11 , wherein the wheel is a steel wheel of a locomotive.

13. A method as in claim 11 , wherein the first and second laser beams are generated by respective optical units mounted on the vehicle carriage, the first laser beam being directed to the side surface of the wheel and the second laser beam being directed to a surface being driven by the wheel.

14. A method as in claim 12 , wherein the first and second laser beams are generated by respective optical units mounted at trackside, the first laser beam being directed to the side surface of the wheel and the second laser beam being directed to an axle mount of the wheel.

15. A method as in claim 13 , wherein the Doppler shifted return of the first laser beam is used to calculate the angular velocity of the wheel, and the tangential velocity is calculated from the angular velocity and a radius of the wheel.

16. An apparatus for measuring torsional slip, comprising:

means for using a Doppler shifted return of a first laser beam to measure tangential velocity of a surface rotating about an axis;

means for using a Doppler shifted return of a second laser beam to measure translational velocity of the axis; and

means for deriving the torsional slip of the rotating surface from the difference between the tangential velocity and the translational velocity.

17. An apparatus as in claim 16 , wherein the rotating surface is a drive surface of a wheel mounted on an axle of a vehicle carriage, the axle being the axis.

18. An apparatus as in claim 17 , wherein said wheel is a steel wheel of a locomotive.

19. An apparatus as in claim 17 , wherein the first and second laser beams are generated by respective optical units mounted on said vehicle carriage, the first laser beam being directed to a rotating side surface of the wheel and the second laser beam being directed to a surface being driven by the wheel.

20. An apparatus as in claim 18 , wherein said first and second laser beams are generated by respective optical units mounted at trackside, said first laser beam being directed to a rotating side surface of said wheel and said second laser beam being directed to an axle mount of said wheel.

21. An apparatus as in claim 19 , wherein the Doppler shifted return of the first laser beam is used to calculate the angular velocity of the wheel, and the tangential velocity is calculated from the angular velocity and a radius of the wheel.

22. An apparatus as in claim 21 , wherein a spectral processor is used to determine velocity data from the Doppler shifted return of the first laser beam, and the velocity data from the spectral processor is used to calculate the angular velocity of the wheel.

23. An apparatus as in claim 17 , further comprising:

mean for using a Doppler shifted return of a third laser beam to measure tangential velocity of a second wheel mounted on the axis, wherein the first and third laser beams are generated by respective optical units mounted on the vehicle carriage, the first laser beam being directed to a rotating side surface of the wheel and the second laser beam being directed to a rotating side surface of the second wheel; and

means for deriving the relative torsional slip of the wheel and the second wheel from the respective tangential velocities of the wheel and the second wheel.