Train navigator with integral constrained GPS solution and track database compensation
The present invention provides a new set of algorithmic solutions to accommodate track inaccuracy information in track databases. Navigation and measurement aiding processes are defined by a stochastic mode relative to a moving rail frame defined so that it is aligned with the heading of the compensated track database at the current along track-position. Filtering generates long and short wavelength track alignment disturbances commensurate with track grade to compensate for track database errors; a stochastic error model is defined as the difference between the deterministic implementation and the actual stochastic processes Bayesian estimation of the error variables is implemented via a digital Kalman filter with the navigation, database, and measurement errors removed by subtracting the filter estimates.
1. A method for navigation in a system including railway track having a plurality of track irregularity classes with a quantitative value associated with each class and a railway vehicle for movement along the railway track having a navigation system for determining railway vehicle position along the railway track, the navigation system including a database having at least a geometric track model contained therein, the navigation system also including inertial components for measuring heading and variations thereof and acceleration and variations thereof and a satellite responsive GPS for providing geopositional data, comprising the steps of:
establishing an a-priori stochastic model of actual navigation errors and an a-priori stochastic model of a measurement aiding process;
effecting a Kalman type filtering of error variables to create estimated track database errors constrained by the track irregularity class; and
implementing substantially real-time feedback of estimated track database errors for correcting the geometric track model contained in the database for subsequent use for navigation upon the railway track.
2. The method of claim 1 , wherein said second-mentioned step includes providing, as an input thereto, a satellite-based GPS measurement related to a current position of the railway vehicle on the railway track.
3. A method for rail track database compensation in a system including railway track having a plurality of track irregularity classes with a quantitative value associated with each class and a railway vehicle for movement along the railway track having a navigation system for determining railway vehicle position along the railway track, the navigation system including a database having at least a geometric track model contained therein, the navigation system also including inertial components for measuring heading and variations thereof and acceleration and variations thereof and a satellite responsive GPS for providing geo-positional data, comprising the steps of:
establishing an a-priori stochastic model of actual navigation errors and an a-priori stochastic model of a measurement aiding process;
effecting a Kalman type filtering of error variables to create estimated track database errors constrained by the track irregularity class; and
implementing substantially real-time feedback of estimated track database errors for correcting the geometric track model contained in the database for subsequent use for navigation upon the railway track.
4. The method of claim 3 , wherein said second-mentioned step includes providing, as an input thereto, a satellite-based GPS measurement related to a current position of the railway vehicle on the railway track.
5. A method of simultaneous navigation and rail track database correction in a system including railway track having a plurality of track irregularity classes with a quantitative value associated with each class and a railway vehicle for movement along the railway track having a navigation system for determining railway vehicle position along the railway track, the navigation system including a rail track database having at least a geometric track model contained therein, the navigation system also including inertial components for measuring heading and variations thereof and acceleration and variations thereof and a satellite responsive GPS for providing geo-positional data, comprising the steps of:
establishing an a-priori stochastic model of actual navigation errors and an a-priori stochastic model of a measurement aiding process;
effecting a Kalman type filtering of error variables to create estimated track database errors constrained by the track irregularity class; and
implementing substantially real-time feedback of estimated track database errors previously presented for navigation upon the railway track.
6. The method of claim 5 , wherein said second-mentioned step includes providing, as an input thereto, a satellite-based GPS measurement related to a current position of the railway vehicle on the railway track.