Systems and methods for computing vertical position
Control systems and methods that provide a high degree of vertical measurement accuracy for a body in motion are disclosed. The systems employ an inertial sensor system for vertical measurement and a Global Navigation Satellite System that includes multipath reduction or attenuation to provide corrected vertical information for a moving body to the inertial sensor system. The combination of these systems enables the maintenance of an accurate vertical position for said body.
1. A method for determining vertical position comprising:
providing navigation-grade vertical acceleration information of a body in motion;
providing satellite-based vertical position information of the body in motion;
processing the vertical acceleration information of the body in motion to compute vertical position information;
determining the difference between said computed vertical position information and said satellite-based vertical position information; and
employing said difference in processing the vertical acceleration information of the body in motion.
2. The method of claim 1 , wherein the vertical position information of the body in motion comprises GNSS information.
3. The method of claim 2 , wherein the GNSS information comprises GPS information.
4. The method of claim 1 , further comprising compensating the computed vertical position information for latent vertical position information.
5. The method of claim 4 , further comprising subtracting the compensated computed vertical position information from said satellite based vertical position information and using a result of the subtraction to make the corrections during the processing of the vertical acceleration information.
6. The method of claim 1 , wherein processing the vertical acceleration information of the body in motion to compute vertical position information comprises performing at least one integration on the vertical acceleration information.
7. The method of claim 6 , wherein performing the at least one integration on the vertical acceleration information comprises integrating the vertical acceleration information to determine vertical velocity information.
8. The method of claim 7 , wherein performing the at least one integration on the vertical acceleration information further comprises integrating the vertical velocity information to determine the computed vertical position information.
9. The method of claim 1 , wherein the vertical acceleration information comprises at least one of inertial guidance information and odometry information.
10. The method of claim 9 , wherein the at least one of inertial guidance information and odometry information comprises information from an accelerometer triad and 2-axis tilt sensor.
11. A system for determining vertical position comprising:
a navigation-grade accelerometer for determining vertical acceleration information of a body in motion;
a processor for determining vertical position information from said vertical acceleration information;
a satellite navigation receiver for providing reference vertical position information of said body in motion, said receiver including an antenna connected to the satellite navigation receiver configured to randomize multi-path noise; and
a negative feedback loop, including a filter, whose input is the difference between the reference vertical position information and the determined vertical position information, and whose output is to said processor for determining corrected vertical position information.
12. A method for determining vertical position plus or minus 1 centimeter, 2-sigma, comprising:
determining a vertical reference position using a satellite navigation receiver;
performing a first integration of the output of a navigation-grade accelerometer with respect to time;
using said output of the first integration as the input to a second integration with respect to time to obtain inertial vertical position;
delaying said inertial navigation position to account for the latency associated with said global navigation system receiver;
subtracting the delayed inertial position from said vertical reference position; and
feeding back said difference, using negative feedback, to the acceleration and velocity integrators so as to reduce the errors introduced in the acceleration and velocity integrators from said accelerometer.
13. The method of claim 12 wherein said difference between the delayed inertial position and the vertical reference position is multiplied by a first constant and subtracting from the input of said second integration.
14. The method of claim 12 wherein said difference between the delayed inertial position and the vertical reference position is multiplied by a second constant.