System and method for sensing position of a vehicle

1. A system for determining the position of a vehicle which moves responsive to an inverter having a 360 degree electrical cycle, said system comprising:

a guideway comprising a linear synchronous motor excited by said inverter;

a vehicle adapted to move with respect to said guideway and the linear synchronous motor thereof;

a reflective pattern disposed along said guideway;

a light source coupled to said vehicle, said light source adapted to direct light toward said reflective pattern;

a light sensor coupled to said vehicle, said light sensor adapted to sense the light from said light source which is reflected from said reflective pattern and to output a plurality of pulses corresponding to movement of said vehicle with respect to said reflective pattern; and

a circuit cooperating with said light sensor, said circuit adapted to determine the position of said vehicle from said pulses, said position corresponding to the 360 degree electrical cycle of said inverter.

2. The system of claim 1 wherein said circuit is further adapted to determine the velocity of said vehicle from said pulses.

3. The system of claim 1 wherein said vehicle is a maglev vehicle.

4. The system of claim 1 wherein said vehicle has a direction of motion with respect to said guideway; wherein said reflective pattern includes an alternating pattern of reflective segments and substantially non-reflective segments; and wherein each of said reflective segments and said substantially non-reflective segments have a common dimension along said direction of motion.

5. The system of claim 4 wherein a position of the 360 degree electrical cycle of said inverter corresponds to one of said substantially non-reflective segments; wherein said one of said substantially non-reflective segments has a reflective sub-segment disposed between two substantially non-reflective sub-segments; and wherein said circuit is further adapted to reset said position to zero based upon one of said pulses corresponding to said reflective sub-segment, said one of said pulses having a smaller pulse width than the pulse width of the others of said pulses.

6. The system of claim 1 wherein said reflective pattern includes a repetitive pattern having a length which corresponds to the 360 degree electrical cycle of said inverter.

7. The system of claim 6 wherein said length is about 432 mm.

8. The system of claim 7 wherein said vehicle has a direction of motion with respect to said guideway; wherein said reflective pattern includes an alternating pattern of twelve reflective segments and twelve substantially non-reflective segments; and wherein each of said reflective segments and said substantially non-reflective segments has a common dimension of about 18 mm along said direction of motion, said common dimension representing 15 degrees of the 360 degree electrical cycle of said inverter.

9. The system of claim 8 wherein a position of the 360 degree electrical cycle of said inverter corresponds to one of said twelve substantially non-reflective segments; wherein said one of said twelve substantially non-reflective segments has a reflective sub-segment disposed between two substantially non-reflective sub-segments; and wherein said circuit is further adapted to reset said position to zero based upon one of said pulses corresponding to said reflective sub-segment, said one of said pulses having a smaller pulse width than the pulse width of the others of said pulses.

10. The system of claim 1 wherein said vehicle has a direction of motion with respect to said guideway; and wherein said reflective pattern includes a width of about 100 mm, said width being normal to said direction of motion.

11. The system of claim 1 wherein said guideway includes a wayside location; wherein said circuit comprises a modulator and a radio transmitter at said vehicle, and a radio receiver, a demodulator and a processor at said wayside location; wherein said modulator converts said pulses to a frequency-shift keying signal; wherein said radio transmitter transmits said frequency-shift keying signal to said radio receiver; wherein said radio receiver receives said transmitted frequency-shift keying signal and outputs a received frequency-shift keying signal to said demodulator; wherein said demodulator outputs a plurality of pulses to said processor; and wherein said processor accumulates the pulses from said demodulator to determine said position corresponding to the 360 degree electrical cycle of said inverter.

12. The system of claim 1 wherein said vehicle is a maglev vehicle including a permanent magnet array; and wherein said light source and said light sensor are coupled to the permanent magnet array of said maglev vehicle.

13. The system of claim 12 wherein said reflective pattern is disposed on an optical tape; wherein said guideway includes a Litz wire support track; and wherein said optical tape is coupled to said Litz wire support track.

14. A method for determining the position of a vehicle which moves responsive to an inverter having a 360 degree electrical cycle, said method comprising:

employing a guideway comprising a linear synchronous motor excited by said inverter;

moving a vehicle with respect to said guideway and the linear synchronous motor thereof;

disposing a reflective pattern along said guideway;

directing a light from said vehicle toward said reflective pattern;

reflecting said light from said reflective pattern;

sensing the reflected light and outputting a plurality of pulses corresponding to movement of said vehicle with respect to said reflective pattern;

determining the position of said vehicle from said pulses, said position corresponding to the 360 degree electrical cycle of said inverter; and

employing said position by an inverter control system for said inverter.

15. The method of claim 14 further comprising

employing a wayside control location associated with said guideway; and

wirelessly transmitting said pulses to said wayside control location.

16. The method of claim 15 further comprising

wirelessly receiving the transmitted pulses as received pulses at said wayside control location; and

accumulating the received pulses to determine said position corresponding to the 360 degree electrical cycle of said inverter.

17. The method of claim 16 further comprising

including said position in a serial message; and

transmitting said serial message to the inverter control system for said inverter.

18. The method of claim 16 further comprising

triggering an interrupt at a processor with each of said received pulses; and

updating an accumulator by said processor responsive to said interrupt.

19. The method of claim 18 further comprising

measuring a time duration of one of said received pulses; and

determining the speed of said vehicle from said time duration.

20. The method of claim 14 further comprising

employing a direction of motion of said vehicle with respect to said guideway;

disposing an alternating pattern of reflective segments and substantially non-reflective segments on said reflective pattern;

employing a common dimension for each of said reflective segments and said substantially non-reflective segments along said direction of motion;

employing a position of the 360 degree electrical cycle of said inverter corresponding to one of said substantially non-reflective segments;

employing said one of said substantially non-reflective segments having a reflective sub-segment disposed between two substantially non-reflective sub-segments; and

resetting said position of said vehicle to zero based upon one of said pulses corresponding to said reflective sub-segment, said one of said pulses having a smaller pulse width than the pulse width of the others of said pulses.