IoT-Enabled CRDS Sensor for UAV

The Challenge

An academic institution needed to commercialize an emerging Cavity Ringdown Spectroscopy (CRDS) methane sensor technology that was the subject of pure research.  Success of the project would be measured by the ability to demonstrate working sensors in geographically disparate portable, vehicle and Unmanned Aerial Vehicle (UAV) applications.  Key to success would be utilization of cellular-based internet of things (IoT) techniques to remotely publish data to Amazon Web Services (AWS).  Since the existing concept was built with laboratory equipment on an optical table, selecting, designing, and integrating electronic circuits capable of portable operation would be a significant challenge.

The Solution

TCB Engineers specified a National Instruments Single Board RIO system-on-module (sbRIO-9651 SOM) as the embedded controller primarily due to advantageous size, weight and power (SWaP) vs. computational capability, but also because the customer was already familiar with the LabVIEW RT-FPGA development system.  The sbRIO-9651 is based on the Xilinx Zync-7000 system-on-chip (SoC), a diverse product family that integrates a ARM Cortex-A9 CPU, FPGA and several peripherals on a single integrated circuit.  By basing the design on this powerful, scalable product, the customer has a multitude of options for increasing capability and pushing SWaP to extremes in future product iterations.

 

Phase I – Proof-of-Concept

A detailed systems design was performed and critical components were selected, including the sbRIO-9651 SOM Carrier Board from National Instruments. Evaluation boards from silicon vendors were integrated where available and various prototyping methods were utilized for those that were not.  LabVIEW embedded Realtime and FPGA software were developed to accomplish the system objectives and web-based techniques were developed for configuration and administration. The prototype was substituted into the academic system for comparison and results were highly favorable. The prototype measured approximately 12”x12” and operated from 12VDC at 8W, a SWaP reduction of 90%.

 

Phase II – Portable Validation Prototype

Electronics from the previous phase were augmented with a custom in-house power supply PCBA to facilitate safe, efficient operation and compliance with applicable SAE standards.  Packaging consisted of a modified NEMA IP67 enclosure, custom heatsink and vehicle mounting system.  A cellular gateway was integrated to provide the means for quasi real-time remote database insertion.  Thermal chamber testing was performed to verify reliable operation over -20 to +70C ambient and several thousand drive miles were logged with this assembly.  The system proved reliable, repeatable and accurate, allowing the customer to focus on complementary project contributions and further SWaP reductions through ancillary component optimization.

 

Phase III – SWaP Optimized UAV Payload

Electronics from the previous phase were tightly integrated by designing two custom PCBAs in-house.  Each is unique in that one contains predominantly low noise analog and the other an eight-layer digital carrier.  The assembly includes an on-board fiber-coupled distributed feedback (DFB) butterfly laser, associated thermoelectric (TEC) controller and precision programmable current source.  The board stack was housed in a custom carbon fiber and aluminum enclosure with IP67 sealing.

        

Several copies were made and used in various configurations, including in the research laboratory, mounted underwing on a UAV, and on the roof of a test vehicle.  The completed assembly measures approximately 10″L x 6″W x 3″H and weighs about three pounds.  Verified accuracy and repeatability of single-digit part-per-million was achieved across a wide temperature range, affording accurate measurement in outdoor applications.

          

 

Services Used

 

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