Positioning system for aerial non-destructive inspection

A method for operating an unmanned aerial vehicle, comprising:

• (a) controlling an unmanned aerial vehicle to hover at a location separated from a structure;
• (b) directing first and second laser pointers pivotably mounted on-board the unmanned aerial vehicle in parallel toward a surface of the structure, the respective pivot axes of the first and second laser pointers being separated by a fixed distance;
• (c) using the mutually parallel first and second laser pointers to transmit mutually parallel laser beams onto first and second spots respectively while the unmanned aerial vehicle is hovering at the location;
• (d) using a camera on-board the unmanned aerial vehicle at a first time to capture a first image of a portion of the surface of the structure that includes the first and second spots;
• (e) pivoting the first and second laser pointers by a predefined angle while the unmanned aerial vehicle is hovering so that the first and second laser pointers are no longer parallel;
• (f) using the pivoted first and second laser pointers to transmit non-parallel laser beams onto respective third and fourth spots on the surface of the structure while the unmanned aerial vehicle is hovering at the location;
• (g) using the camera at a second time to capture a second image of the portion of the surface of the structure that includes the third and fourth spots;
• and
• (h) processing the first and second images to calculate a first separation distance separating the unmanned aerial vehicle from the structure based on the positions of the third and fourth spots in the images, the predefined angle and the fixed distance separating the pivot axes of the laser pointers.

A method for sizing a feature of a structure using an unmanned aerial vehicle comprising a pan-tilt mechanism that supports a camera and a laser range meter and an inertial measurement unit, the method comprising:

• (a) controlling the unmanned aerial vehicle to fly toward and then hover at a first location which is separated from a structure to be inspected;
• (b) aiming the laser range meter at a first point corresponding to a first visible feature on a surface of the structure while the unmanned aerial vehicle is hovering at the first location and acquiring a first distance measurement;
• (c) using the pan-tilt mechanism to measure the respective pan and tilt angles of the laser range meter when the laser range meter is aimed at the first point;
• (d) converting the distance and angle measurements acquired in steps (b) and (c) into a first vector representing the location of the first point in the frame of reference of the unmanned aerial vehicle at the first location;
• (e) aiming the laser range meter at a second point corresponding to a second visible feature on the surface of the structure while the unmanned aerial vehicle is hovering at a second location and acquiring a second distance measurement;
• (f) using the pan-tilt mechanism to measure the respective pan and tilt angles of the laser range meter when the laser range meter is aimed at the second point;
• (g) converting the distance and angle measurements acquired in steps (e) and (f) into a second vector representing the location of the second point in the frame of reference of the unmanned aerial vehicle at the second location;
• (h) using an inertial measurement unit to measure acceleration and rotational rate of the unmanned aerial vehicle during flight from the first location to the second location;
• (i) generating a transformation matrix representing a position difference and an orientation difference between the first and second locations of the unmanned aerial vehicle based on information acquired in step (h);
• (j) multiplying the second vector by the transformation matrix to form a third vector representing the location of the second point in the frame of reference of the unmanned aerial vehicle at the first location;
• and
• (k) calculating a distance between the first and second points using the first and third vectors.

An unmanned aerial vehicle comprising:

• a frame;
• a plurality of rotors rotatably mounted to the frame;
• a plurality of motors respectively coupled to drive rotation of the rotors of the plurality of rotors;
• a motor controller for controlling operation of the plurality of motors;
• a pan-tilt mechanism mounted to the frame;
• a camera mounted to the pan-tilt mechanism;
• a laser range meter mounted to the pan-tilt mechanism;
• a computer system configured to send commands to the motor controller, control operation of the pan-tilt mechanism, and selectively activate the camera and the laser range meter;
• an inertial measurement unit mounted to the frame and configured to send linear acceleration and rotation rate data to the computer system;
• and
• a transceiver configured to enable communication between the computer system and a control station,
• wherein the computer system is further configured to:
• receive image data from the camera, pan and tilt angle data from the pan-tilt mechanism, distance data from the laser range meter, and linear acceleration and rotation rate data from the inertial measurement unit;
• determine a first location of the unmanned vehicle relative to a structure;
• and
• send a first command to the motor controller to fly the unmanned aerial vehicle from the first location to a second location whereat the camera is separated from a surface of the structure by a goal offset.

An unmanned aerial vehicle comprising:

• a frame;
• a plurality of rotors rotatably mounted to the frame;
• a plurality of motors respectively coupled to drive rotation of the rotors of the plurality of rotors;
• a motor controller for controlling operation of the plurality of motors;
• a camera;
• first, second and third laser pointers;
• a computer system configured to send commands to the motor controller and selectively activate the camera and the first through third laser pointers;
• and a transceiver configured to enable communication between the computer system and a control station, wherein the first and second laser pointers are fixed to the frame in a mutually parallel relationship, and the third laser pointer is pivotably coupled to the frame.