Method for determining states of a system using an estimation filter

• US 10,088,319 B2
• Filed: 03/23/2016
• Issued: 10/02/2018
• Est. Priority Date: 05/08/2015
• Status: Active Grant

• Current Assignee: Northrop Grumman Litef Gmbh (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Litef Gmbh (Northrop Grumman Corporation)
• Inventors: Herberth, Uwe, Martin, Tim
• Primary Examiner(s): Figueroa, Jaime
• Application Number:
  US15/572,566
• Publication Number:
  US 20180128619A1
• Time in Patent Office: 923 Days
• Field of Search: 701 1, 701 23
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01C 21/20 Instruments for performing navigational calculations G01C21/24, G01C21/26 take precedence
• CPC Class Codes: G01C 21/3605 Destination input or retrieval
• CPC Class Codes: G01D 1/14 giving a distribution function of a value, i.e. number of times the value comes within specified ranges of amplitude
• CPC Class Codes: G01S 19/49 whereby the further system is an inertial position system, e.g. loosely-coupled

Abstract

Method for determining states of a system by means of an estimation filter, in which first state values are determined by calculating a mean value of a probability distribution for the states, in which a probability for deviation for the case that the first state values deviate from the actual states of the system is calculated, and in which the states of the system are measured as state data. In the method the first state values are corrected by means of the state data then, if the probability for deviation is larger than a threshold.

Claims

1. A method for determining states of a system by means of an estimation filter, comprising:

determining of first state values by calculating mean values of respective probability distributions for each of the states by the estimation filter;

calculating a probability for deviation in the case that the first state values deviate from the actual states of the system by the estimation filter;

measuring the states of the system as state data; and

then, if the probability for deviation is greater than a threshold, correcting the first state values by means of the state data.

2. The method according to claim 1, wherein

the first state values are determined in a first time increment;

then, if the probability for deviation is equal or smaller than the threshold, second state values are determined based on the first state values in a second time increment following the first time increment; and

then, if the probability for deviation is greater than the threshold, the second state values are determined in the second time increment based on the corrected first state values.

3. The method according to claim 1, wherein

the estimation filter is a Kalman filter;

the states of the system determine a position of an object;

the state values are position values, which indicate the position; and

the measured state data are position data.

4. The method according to claim 3, wherein

the position data comprise an absolute position of the object and relative position changes of the object;

the relative position changes are used to determine the mean value of the probability distribution for the position; and

the absolute position is used to correct position values.

5. The method according to claim 3, wherein

the position data are measured by means of a satellite navigation system and a linear acceleration sensor and/or rotation rate sensor.

6. The method according to claim 3, wherein

a micro electro-mechanical sensor (MEMS), a fiber optic sensor, or a ring laser gyroscope are used for measuring the position data.

7. The method according to claim 1, wherein the probability for deviation is determined based on a covariance matrix of the probability distribution.

8. The method according to claim 1, wherein the probability for deviation is determined based on at least one residuum.

9. A device for determining a position of an object, comprising

a measurement unit suited to measure position data;

and

a calculation unit having an estimation filter that is suited to

determine first position values by calculating mean values of respective probability distributions for the position by the estimation filter;

calculate a probability for deviation in the case that the first position values deviate from the actual position of the object by the estimation filter; and

then, if the probability for deviation is greater than a threshold, correct the first position values by means of the position data.

10. The device according to claim 9, wherein

the measurement unit comprises a satellite navigation system and a linear acceleration sensor and/or rotation rate sensor;

the linear acceleration sensor and/or rotation rate sensor is suited to measure relative position changes that are used to determine the mean value of the probability distribution for the position; and

wherein

the satellite navigation system is suited to measure an absolute position that is used to correct position values.

11. An unmanned aerial vehicle comprising a device according to claim 9.