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VisNav Sensor Systems

The Texas A&M team has engaged in significant sensor and sensor fusion research over the past few years [patents and publications].   One focus of our sensors and sensor fusion work has been to address the demands of real-time, high resolution, and high reliability systems; we seek optimal integrated designs of advanced sensors, fusion algorithms, and computing architectures to solve particular set of problems. The integration of sensor design, sensor fusion algorithms and advanced computing results in a class of embedded systems we refer to as smart sensors. VisNav, our vision based navigation sensor suite has a special mention among our sensor results. StarNav, one of Texas A&M's other navigation solution is described here >>

VisNav came in to being, with a primary objective of enabling (anticipating a worst case scenario) a single sensor to provide full 6 degree of freedom relative navigation of two air vehicles – with sufficient precision and bandwidth to enable the challenging goal of fully autonomous air refueling.   A second objective was to achieve an extremely robust navigation solution.  We have fully achieved these goals in ground demonstrations, and the flight experiment program is presently mid-stream.  We mention that the small mass (<1 kg) and low power (< 20 watts) of this modular sensor design allows obvious paths to dual and higher parallel redundancy architectures.

air to air refueling using VISNAV sensors

Fig A. High precision air to air refueling demonstrations using VISNAV sensor suite.


Autonomous Air refueling Schematic

Fig B. Autonomous aerial refueling using Visnav Sensors : Concept


VisNav Concept Schematic

Fig C. Schematic depicting the VisNav Concept


Autonomous aerial refueling for UAVs is considered a breakthrough enabling technology that will enable 24/7 duration and open entirely new CONOPs for ISR and tactical applications of UAVs. In point of fact, autonomous aerial re-fueling and the resulting near-infinite persistence/robustness of ISR, communications, and other critical functions are believed to be the keys to realizing the vision of UAVs having ubiquitous and highly constructive roles in future combat systems.  Future research on mission design and control of UAVs needs to be fully informed by this capability; entirely new scenarios are feasible.

VisNav - Hardware

Fig D. Hardware features and details of the VisNav sensor suite for autonomous air refuelling

With reference to Figure D, the VisNav sensor has an analog IR focal plane detector (a position sensitive photodetector) that centroids incident energy. The rise time of this detector is about 1 micro-second, allowing the use of structured IR energy to discriminate active beacons in the presence of random environmental sources. The VisNav concept is to place 4 or more (8, typically) beacons at known locations on the tanker aircraft (4 are relatively widely spaced on the wing and horizontal stabilizer of the tanker, while 4 are placed much closer together on re-fueling drogue).  These beacons are eyesafe IR LEDs that emit individually commanded waveforms of IR energy, with a typical main waveform frequency of 40KHZ.



Flight Test Demonstration Program :

To validate and demonstrate the Autonomous Air Refueling System (AARS), composed of the VisNav relative navigation sensor, and the Reference Observer Tracking Controller (ROTC) control laws, both developed by our team, we conducted the following flight test program.  The program is being conducted from 3 April 2006 – 31 October 2007 at the Flight Mechanics Laboratory, under sponsorship from FRL/MN and Boeing, under sub-contract to StarVision Technologies.  Fight testing of the first vehicle began in June 2006, and is still proceeding.  To date, more than 10 validation and verification flights of the tanker and receiver have been conducted.  The first air-to-air docking of the tanker aircraft and the receiver aircraft, without human supervision or intervention, is scheduled for 2nd Quarter 2007.


Visnav Flight Test 2006-07

UAV Proximity GNC using VisNav: Experimental Demonstrations, 2006.


  1. J. L. Junkins, H. Schaub, D. Hughes, “Noncontact Position and Orientation Measurement System and Method,” U.S. Patent No. 6,266,142 B1, July 24, 2001.
  2. Garcia, F. L., Jr., Junkins J.L., and Valasek, J., "Method and Apparatus for Hookup of unmanned/Manned Multi-purpose (HUM) Air Vechicles," U.S. Patent No. 7,152,828.

Publications :

  1. Singla, P. and Junkins, J. L., Adaptive Multiresolution Modeling, Estimation and Control of High Dimensioned Nonlinear Systems, CRC Press, to appear 2007.
  2. Crassidis, J. L.. and Junkins, J. L., Optimal Estimation of Dynamic Systems, 591 pp., CRC Press, Boca Raton, FL., 2004..
  3. Doebbler, James, Monda, Mark, Valasek, John, and Schaub, Hanspeter, "Boom and Receptacle Autonomous Air Refueling Using a Visual Pressure Snake Optical Sensor," -to appear, Journal of Guidance Control and Dynamics.
  4. S. G. Kim, J. L. Crassidis, Y. Cheng, A. M. Fosbury, and John L. Junkins, "Kalman filtering for relative spacecraft attitude and position estimation," Journal of Guidance Control and Dynamics, 30:133–143, January 2007.
  5. Tandale, Monish D., Bowers, Roshawn, and Valasek, John, “Robust Trajectory Tracking Controller for Vision Based Autonomous Aerial Refueling of Unmanned Aircraft,” Journal of Guidance, Control, and Dynamics, Voume 29, Number 4, July-August, 2006, pp. 846-857.
  6. Valasek, J., Gunnam, K., Kimmett, J., Tandale, M. D., Junkins, J. L., and Hughes, D., “Vision-Based Sensor and Navigation System for Autonomous Air Refueling,” The Journal of Guidance Control and Dynamics, Vol. 28, April 2005, pp. 979–989.
  7. Gunnam, K., Hughes, D., Junkins, J. L., and Khetarnaraz, N., “A Vision Based DSP Embedded Navigation Sensor,” IEEE Journal of Sensors, Vol. 2, October 2002, pp. 428–442.
  8. Suman Chakravorty and John L. Junkins. "Intelligent path planning in unknown environments with vision like sensors," Automatica, NA:–, January Under review.
  9. Chakravorty, S. and Junkins, J. L., “Intelligent Exploration of Unknown Environments with Vision Like Sensors,” International Conference on Advanced Intelligent Mechatronics, Monterey, California, 24-28 July 2005.
  10. Singla, P., Subbarao, K., Hughes, D., and Junkins, J. L., “Structured Model Reference Adaptive Control For Vision Based Spacecraft Rendezvous And Docking,” 13th Annual AAS/AIAA Space Flight Mechanics Meeting, Ponce, Puerto Rico, 9-13, February 2003.
  11. Gunnam, K., Hughes, D., Junkins, J. L., and Khetarnaraz, N., “A Vision Based DSP Embedded Navigation Sensor,” International Conference on Signal Processing, ICSP, 2002, Beijing, China, Vol. 2, August, 26-30, 2002.
  12. Kimmett, Jennifer, Valasek, John, and Junkins, John L., “Vision Based Controller for Autonomous Aerial Refueling,” CCA02-CCAREG-1126, Proceedings of the IEEE Control Systems Society Conference on Control Applications, Glasgow, Scotland, 18-20 September 2002.
  13. Kimmett, Jennifer, Valasek, John, and Junkins, John L., “Autonomous Aerial Refueling Utilizing a Vision Based Navigation System ,” AIAA-2002-4469, Proceedings of the AIAA Guidance Navigation and Control Conference, Monterey, California, 5-8 August 2002.
  14. Valasek, John, Kimmett, Jennifer, Hughes, Declan, Gunnam, Kiran, and Junkins, John L., "Vision Based Sensor and Navigation System for Autonomous Aerial Refueling," AIAA-2002-3441, 1st AIAA Unmanned Aerospace Vehicles, Systems, Technologies, and Operations Conference, Portsmouth, VA, 20-22 May 2002.
  15. Valasek, John and Junkins, John L., “Intelligent Control Systems and Vision Based Navigation to Enable Autonomous Aerial Refueling of UAVs,” 04-012, Proceedings of the 27th Annual American Astronautical Society Guidance and Control Conference, Breckenridge, CO, 4-8 February 2004
  16. Valasek, John, "High Fidelity Flight Simulation of Autonomous Air Refueling Using a Vision Based Sensor," Final Technical Report, StarVision Technologies Incorporated, December 2004.
  17. Valasek, John, Junkins, John, Lund, David W., and Ward, Donald T., "Autonomous Aerial Refueling Demonstration: Phase 0," Final Technical Report, 32525-20270 AE, 30 June 2004.
  18. John L. Junkins, Majji, M.and Davis, J., J., "Hierarchical Multi-rate Measurement Fusion for Estimation of Dynamical Systems," Preprint, NA:–, Under review.




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