AUAV EZI-NAV
Do you want to fly small UAV’s without mortgaging your house?
Then here is something to make you sit up and take notice.
By Bob Young Silvertone Electronics, Sydney, Australia
During a recent trip to the U.S. I had the good fortune to visit the AUAV (Autonomous Unmanned Air Vehicles) facility in Palmetto, Florida and was given the opportunity to examine and test fly the AUAV Ezi-Nav autopilot system.
A.U.A.V. is instrumental in the development of small to medium size UAV's and autonomous flight control systems (autopilots) for the control and navigation of UAV aircraft.
Dave Jones the CEO of AUAV has made quite a name for himself as a driving force in the small and inexpensive UAV field. Dave has successfully undertaken many and varied UAV tasks from self-funded autonomous distance flights to commercial surveys for local government departments and Universities.
Fig 1. AUAU Mobile Flight Control Center /
Fig 2. View inside the control van
Perhaps the most impressive aspect of the AUAV operation is the amount of self-funded R&D that has resulted in completely novel system reaching production in such a short space of time. Here is an indication of the driving force of the CEO of AUAV.
AUAV has developed from scratch such systems as a complete DSS radio link that is available on 900 MHz or 2.4GHz.
The complete Ezi-Nav system including a mobile command center with original data display software and featuring such novel ideas as a gyro controlled, constant rate of turn GPS steering module, GPS controlled altitude hold and an integrated IR optical attitude control system (FMA) as well as developing and building numerous airframes of original design. (Figure 9)
All in a ridiculously short space of time when judged by normal R&D standards.
The quality of the results obtained from routine survey flights speak for themselves as the two photographs below illustrate with startling clarity.
Fig 3. Lost model discovered in a pond on a routine survey mission. /
Fig 4. Another shot showing the excellent photo quality obtained by AUAV aircraft.
However I digress, as the main task here is to examine the Ezi-Nav autonomous Flight control system.
The AUAV Ezi-Nav is an inexpensive modular navigation, control and telemetry system designed for small to medium, low cost UAVs. This type of UAV is ideal for commercial applications such as agricultural and mineral survey as well as many research and development applications.
The low cost makes possible the use of the Ezi-Nav in expendable UAVs and the modular design allows development to proceed at a minimum of cost with future expansion available when required.
A.U.A.V. has also created a series of autonomous aircraft to fit the needs of universities and the research industry. The systems that A.U.A.V.has developed are low cost and very reliable due to the "keep it simple" process. A complete turnkey UAV system from A.U.A.V. allows the program manager to concentrate more on the payload and experiments rather then spending their valuable time designing the airframe and flight control systems. An extremely important consideration for program managers.
Ezi-Nav Development
Dave, a long time R/C pilot and electronics engineer with many years experience in research and development, had long sensed the need for a simple low cost autonomous navigation system for small UAVs that exceeded the capabilities of existing systems.
Dave felt that an easy to install, set-up and operate unit would make life much less complicated for anyone called upon to develop a small UAV.
The design criteria of the Ezi-Nav system was as follows:
(1) (1) Self-contained modular design which includes the R/C receiver with all interconnections done with plug-in PCBs (modules) and all contained in a single enclosure, thereby eliminating the dreaded wiring entanglements (Figure 5- 6).
(2) (2) Simple set-up using auto calibration to maintain a pre-programmed 15o per second rate of turn. Variable stability augmentation and altitude hold gain, controlled in flight via the control transmitter to simplify control dynamics and trimming.
(3) (3) Colour coded input and output connections. ie. GPS data via Green connectors; Telemetry output via Yellow connectors; Battery power via Red connectors.
(4) (4) All servo connectors are labeled to respective servos. ie Aileron, Elevator, Throttle, Rudder, etc.
(5) (5) Inbuilt Roll/Pitch stability augmentation by Infra-Red Optical sensor. GPS navigation with Gyro controlled rate of turn to maintain a 15o per second turn rate. GPS Altitude hold.
(6) (6) Telemetry data consists of 4 switched (Logic Hi-Lo) input channels and 8 x 0-5V analogue input channels (One dedicated to flight battery voltage); GPS data. (GGA, RMC, RMB); Servo Position Data, Auto-Pilot Enable/Disable status and stability augmentation gain settings (Roll/Pitch and Altitude Hold).
Fig 5. “Rats Nest” wiring tangle in typical small UAV using standard components. /
Fig 6. . View showing the simplicity of the Ezi-Nav installation. Note the lack of wiring entanglement. Fabulous!
After installing, setting-up and flying the Ezi-Nav I can confidently state that Dave has achieved these goals admirably. Interestingly, some of the above features have never been offered in any small UAV navigation system.
Fig 7. Complete Ezi-Nav with insert showing plug-In modular configuration /
Fig 8. Ezi-Nav with Futaba 9C PCM transmitter showing relative sizes
Installation and Test Flying
After screwing the lid on a freshly completed and tested Ezi-Nav unit and a brief thirty-minute installation (Figure 6) and set-up in one of Dave’s many Single Boom Pusher aircraft, the Ezi-Nav was ready to take to the field. (Figure 9)
Fig 9. A section of the AUAV test flying fleet
Upon arriving at the field assembling and fueling the aeroplane, we powered up the GPS and acquired the satellites. We then entered one waypoint for the center of the runway. The single waypoint test is a very stringent test for system accuracy and aircraft dynamics. We then booted up the Ezi-Nav and R/C flight control after a 10 second auto-calibration sequence we acquired the downlink telemetry data on the laptop virtual cockpit software (Figure 4). We were then ready to fly.
I then took off and climbed to 400 feet AGL and trimmed the aircraft for level flight and headed out on a heading that took me downwind and heading away from the target waypoint.
At about 600 meters downrange I engaged the Ezi-Nav and Dave said “Just hold the transmitter in your hand and stand back here at the waypoint and watch what happens now”
Right on cue the aircraft begun a 180o left turn at 15o per second and then flew straight back to the target waypoint. Standing on the waypoint the UAV passed directly over my head and then began to orbit around the target waypoint at a steady 15o per second.
I repeated this from the four quadrants of the compass with the same results. I noticed that on the Easterly inbound track with a southerly crosswind that the UAV was crabbing to correct for cross track error and still arrived directly overhead at the target waypoint.
Dave held the transmitter and watched the aircraft fly while I walked across to the laptop and looked at the Altitude Hold performance with the autopilot still activated, the Ezi-Nav held altitude at 400 feet and the Altimeter held steady at that altitude with only minor variations over an extended period.
The altitude, speed, heading bearing to waypoint and moving map display data for the Ezi-Nav is derived from the GPS data and transmitted to the virtual cockpit via the DSS telemetry down link transmitter. (Figure 10)
An interesting feature of the virtual cockpit display is the modular nature of the screen layout. Each individual instrument is one complete window, which has all of the attributes of a normal window. Each may be open, closed, resized and repositioned on the computer screen as dictated by the mission requirements. (Figure 11)
Fig 10. Ground Station flight instruments and mapping display. /
Fig 11. View showing small instrument windows being repositioned to make up a custom cockpit layout.
Summary
To sum up, the Ezi-Nav is an outstanding low cost and simple to operate unit ideal for the uses it was conceived for.
To quote Dave, “Don't let the simple look of the Ezi-Nav system fool you”.
It is a fully integrated digital autopilot and ground station system that can be used to operate Unmanned Aerial Vehicles (UAVs) with wingspans of 1 meter and up. There’s no calibration required and it weighs less than a pound including the R/C receiver, GPS receiver and DSS telemetry transmitter!
Fig 12. Homecoming! Another successful mission.
Well done Dave! And thank you for one of the most outstanding visits in a 50-year long career of interesting facility visits.
For more information on the Ezi-Nav system or any of the other products produced by AUAV please visit their web site at http://www.auav.net/