This project will develop a conceptual design for an unmanned aerial system-based laser scanner for aerial mapping that preserves the performance of larger systems flown on manned aircraft, but is small enough to be deployed on midsize unmanned aerial systems. This will enable more economical digital terrain mapping than manned systems. The overall approach to the design is to utilize state-of-the-art laser designs to create a highly compact laser transmitter and combine it with a nonmechanical beam scanner.
Physical Sciences Inc., Andover, MA 01810-1077
With the growth of oil and gas recovery from shale deposits, technologies for cost-effective aerial mapping and monitoring of topography around critical infrastructure, such as well pads, roads, and pipeline corridors, are of increasing importance for design, maintenance, and safety. Remote monitoring is needed to identify, in real-time, topographical changes arising from erosion, stream sedimentation, or other surface activities that require mitigation.
Airborne terrain mapping is one approach for providing the necessary topographical information. Digital terrain mapping from manned aircraft is routinely done using scanned laser range finders, i.e. airborne laser scanners (ALSs). Pulses from a high repetition rate laser are directed at the ground using a mechanical beam scanner and the round trip time is converted to altitude to create a terrain map. The cost of acquiring and operating these systems is substantial. A variety of airborne mappers for deployment on small manned aircraft are commercially available. Recently, nonscanned laser altimeters deployed on small Unmanned Aircraft Systems (UASs) have been demonstrated, including on a Manta UAS that successfully mapped glacial fields in the Arctic, and on a ScanEagle UAS. Small scanned ALS systems have been introduced for deployment on small rotary wing UASs. These particular ALS systems have limited measuring range (100 m typically), and these small UAS aircraft can carry payloads of ~kg size for only15 to 30 minutes, typically. An ALS payload capable of providing precise altitude measurements for terrain mapping and that is deployable on a midsize UAS having an endurance of several hours will create a system that offers a more economical mapping solution while providing the endurance, measurement range, and surface point density of larger systems deployed on manned aircraft. Such a capability will have high value for the gas and oil distribution industry by reducing site development and monitoring costs. Physical Sciences Inc. (PSI), in collaboration with Q-Peak and Leica Geosystems, proposes to develop a state-of-the-art compact sensor payload capable of precision digital terrain measurements that is compatible with the payload resources (10s kg) of midsize UASs.
The proposed sensor will enable a more economic method for terrain mapping of pipeline corridors and other gas and oil infrastructure sites through scanned laser range finding on small UAS aircraft. Such capability will help operators to better plan and monitor sites for economic design, maintenance, and safety.
The project will demonstrate the feasibility for precision laser-based terrain mapping from UASs and the feasibility for packaging the sensor in a manner consistent with the available payload resources for the target aircraft. The project will also provide a plan for a field demonstration of the sensor. The Phase II project will design, fabricate, and demonstrate the field prototype sensor aboard a target aircraft.
PSI and Leica Geosystems intend to commercialize this sensor payload. A compact, high measurement performance airborne laser sensor will be designed to be incorporated into existing UASs. Further development will result in even smaller payloads for smaller UAS compatibility.
A concept of operations was created in which the UAS flies at 800 m agl and has a large enough field-of-regard or swath so that the width of the corridor is covered in one pass. A design for a custom laser transmitter was created with the requisite pulse energy, pulse temporal width, and pulse repetition rate. A CAD model was created and thermal modeling of the laser was performed to ensure the thermal environment was properly controlled. A compact transceiver/scanner subsystem was created. These models were integrated with models for the system controller, IMU, and GPS components into a model of the payload for the SwissDrones SDO 50V2 helicopter. This payload model had been developed previously by Leica Geosystems for their RCD30 camera payload on the same aircraft. The integrated system SWaP was consistent with the payload resources; the integrated payload weighs 18.8 kg while the maximum total payload weight is 50 kg. The endurance of the aircraft with payload is ~ 50 minutes with the standard fuel load. As the UAS ALS payload plus standard fuel load together are ~20 kg lighter than the maximum payload allowance, the remainder of the allowance can be used to carry extra fuel and extend the mission duration. Plans for a Phase 1 program were developed in which an engineering prototype of the UAS ALS would be fabricated and demonstrated on a manned aircraft locally to PSI. This development strategy was chosen to allow the demonstration of the operation and capabilities of the UAS ALS payload during the Phase 2 program.
The project was selected to continue development of the scanner in Phase 2.
The team is reviewing and augmenting the transceiver design to incorporate functionality for transmission and reception of two laser beams. The team is ensuring payload mounting, weight, and balance are correct and are also working to create an aircraft power interface control document (ICD).