UAV POWER LINE POSITION AND LOAD PARAMETER ESTIMATION

• US 20120016538A1
• Filed: 06/20/2011
• Published: 01/19/2012
• Est. Priority Date: 06/21/2010
• Status: Active Grant

• Current Assignee: Optimal Ranging Inc
• Original Assignee: Optimal Ranging Inc
• Inventors: Waite, James W., Gudmundsson, Thorkell, Gargov, Dimitar
• Granted Patent: US 9,037,314 B2
• Time in Patent Office: Days
• US Class Current: 701/3
• CPC Class Codes: B64U 2201/10 autonomous, i.e. by navigating independently from ground or air stations, e.g. by using inertial navigation systems [INS]
• CPC Class Codes: G01B 7/00 Measuring arrangements characterised by the use of electric or magnetic techniques
• CPC Class Codes: G01C 21/005 with correlation of navigation data from several sources, e.g. map or contour matching G01C21/30 takes precedence
• CPC Class Codes: G01C 21/20 Instruments for performing navigational calculations G01C21/24, G01C21/26 take precedence
• CPC Class Codes: G05D 1/10 Simultaneous control of position or course in three dimensions G05D1/12 takes precedence
• CPC Class Codes: G05D 1/101 specially adapted for aircraft

Abstract

A system and method for providing autonomous navigation for an Unmanned Air Vehicle (UAV) in the vicinity of power lines is presented. Autonomous navigation is achieved by measuring the magnitude and phase of the electromagnetic field at an unknown location within a space under excitation by a set of power cables of the power line with one or more orthogonal electromagnetic sensors formed on the UAV; modeling a set of expected complex electromagnetic strengths of the set of power cables at the currently estimated position and orientation of the UAV based on a model of the set of power cables; and estimating parameters related to a position and orientation of the UAV, and load parameters of each cable based on the residual error between the measured set of complex electromagnetic field values and the set of expected electromagnetic field values corresponding to a combined model of the set of power cables.

Claims

1. A method for providing autonomous navigation for an Unmanned Air Vehicle (UAV) in the vicinity of power lines, comprising:

measuring the magnitude and phase of the electromagnetic field at an unknown location within a space under excitation by a set of power cables of the power line with one or more orthogonal magnetic coil sensors formed on the UAV;

modeling a set of expected complex magnetic strengths of the set of power cables at the currently estimated position and orientation of the UAV based on a model of the set of power cables; and

estimating parameters related to a position and orientation of the UAV based on the residual error between the measured set of complex magnetic field values and the set of expected magnetic field values corresponding to a combined model of the set of power cables.

2. The method of claim 1, further including estimating the power grid synchronized load parameters of the power cables by

measuring the complex electric field values using one or more orthogonal electric field sensors on the UAV;

modeling a set of expected complex electric field strengths of the set of power cables at the current position and orientation of the UAV and the predicted position of the cables with respect to the UAV, for one or more of the electric field sensors, the set of expected electric field values corresponding to a model of the set of power cables; and

estimating the phase offset of the current flowing in each cable of the power line relative to the power grid phase reference, based on the residual error between the measured set of complex electric field values and the set of expected electric field values corresponding to a combined model of the set of power cables.

3. The method of claim 2 wherein the residual error between the measured set of complex electric field values and the set of expected electric field values corresponding to a combined model of the set of power cables is used to validate the cable position and electric load results of the magnetic field process.

5. The method of claim 3, wherein embedded 3-d features of a power line (towers, intersections, catenaries, and direction changes), are detected when there is reduced correspondence between a 2-d model and 3-d field measurements.

4. A method for estimating the elevation and offset of a UAV with respect to a set of power lines and the power grid synchronized load parameters of the individual power cables composing the set of power lines, comprising:

measuring the magnitude and phase of the magnetic field at a location within a space under excitation by a set of power cables composing a power line, using one or more orthogonal magnetic sensors on a UAV, the relative distance to the power lines being unknown; and

measuring the complex electric field values using one or more orthogonal electric field sensors from the UAV;

modeling a set of expected complex magnetic strengths of the set of power cables at the current position and orientation of the UAV, for one or more of the magnetic sensors, the set of expected magnetic field values corresponding to a model of the set of power cables; and

modeling a set of expected complex electric field strengths of the set of power cables at the current position and orientation of the UAV and the predicted position of the cables with respect to the UAV, for one or more of the electric field sensors, the set of expected electric field values corresponding to a model of the set of power cables; and

jointly estimating parameters related to the relative 3-d offsets of each cable to the UAV, the complex electric current in each cable, and the phase offset of the current flowing in each cable of the power line from the power grid phase reference, based on the residual error between the measured set of complex magnetic field values and the set of expected magnetic field values, and the residual error between the measured set of complex electric field values and the set of expected electric field values corresponding to a combined model of the set of power cables.

6. A navigation system for an Unmanned Air Vehicle (UAV), comprising:

a plurality of magnetic field detectors configured to measure the magnetic field magnitude and phase generated by aboveground power lines, the plurality of magnetic sensors being at arbitrary orientation to the target power lines but of known orientation in the UAV reference frame;

circuitry coupled to receive signals from the plurality of magnetic field sensors and provide quadrature signals indicating a set of measured complex magnetic field strengths related to each magnetic sensor;

a position and orientation autopilot for indicating a relative distance and orientation over ground of the UAV as it traverses a set of power lines;

a processor coupled to receive the complex magnetic field strength and the over-ground position and orientation, and calculate parameter values related to the positions of each cable composing the set of power lines and the magnitude and phase of the electric current flowing in each cable; and

the processor includes software for performing the following;

measuring the magnitude and phase of the magnetic field at a location within a space under excitation by a set of power cables composing a power line, using one or more orthogonal magnetic sensors on a UAV, the relative distance to the power lines being unknown; and

modeling a set of expected complex magnetic strengths of the set of power cables at the current position and orientation of the UAV, for one or more of the magnetic sensors, the set of expected magnetic field values corresponding to a model of the set of power cables; and

estimating parameters related to the relative distances of each cable to the UAV and complex electric current in each cable, based on the residual error between the measured set of complex magnetic field values and the set of expected magnetic field values corresponding to a combined model of the set of power cables.

7. The system of claim 6, wherein the load parameters relative to the power grid reference of overhead power cables composing a power line are estimated from a UAV flying near the lines, comprising:

a plurality of electric field detectors configured to measure the electric field magnitude and phase generated by aboveground power lines, the plurality of electric sensors being at arbitrary orientation to the target power lines but of known orientation in the UAV reference frame;

circuitry coupled to receive signals from the plurality of electric field sensors and provide quadrature signals indicating a set of measured complex electric field strengths related to each electric field sensor;

a processor coupled to receive the complex electric field strength and calculate the phase offset of the current flowing in each cable of the power line from the power grid phase reference; and

the processor includes software for performing the following;

measuring the complex electric field values using one or more orthogonal electric field sensors from the UAV;

modeling a set of expected complex electric field strengths of the set of power cables at the current position and orientation of the UAV and the predicted position of the cables with respect to the UAV, for one or more of the electric field sensors, the set of expected electric field values corresponding to a model of the set of power cables; and

estimating the phase offset of the current flowing in each cable of the power line from the power grid phase reference, based on the residual error between the measured set of complex electric field values and the set of expected electric field values corresponding to a combined model of the set of power cables.

8. The system of claim 7, wherein the residual error between the measured set of complex electric field values and the set of expected electric field values corresponding to a combined model of the set of power cables is used to validate the cable position and electric load results of the magnetic field process.