Infrastructure and Equipment
UAV Test Bed
The WVU Phastball aircraft was designed to be a modular and low-cost platform that can support a wide range of flight research topics. The Phastball design, has a 2.4 meter wingspan and a 2.2 meter total length. The typical take-off weight is 10.5 kg with a 3.2 kg payload capacity. The Phastball has shown to be a low-cost, low-maintenance, easy-to-operate, multi-functional, and highly effective research tool. More than 200 flight test experiments were performed using four of the aircraft in recent years, for a variety of research projects.
The WVU fifth generation (Gen-V) UAV avionics system performs data acquisition,signal conditioning and distribution, GPS/ inertial navigation system sensor fusion, flight control, command signal distribution, failure emulation, aircraft health monitoring, and fail-safe functions. The computer integrates and distributes control commands from five different sources: R/C safety pilot, research pilot, on-board flight control system, on-board failure emulation system, and on-board excitation system (OBES). The integrated control commands are then forwarded to nine independent actuators for aircraft control. The Gen-V avionic system also incorporates several design features, such as hardware redundancies on critical components, to improve the safety of the research aircraft under sub-system failure conditions.
Ground Control Station
A mobile ground control station (M-GCS), as shown in Fig. 12, was recently developed at WVU. The main purpose of the M-GCS, conceptually modeled after the GCS of the NASA Langley Airstar research program, is to enable high-precision validation of experimental flight control laws. The WVU M-GCS is based on the dual operational concept of a safety pilot and a research pilot. The responsibilities of the safety pilot are limited to the take and landing phases of the UAV platform. Once airborne, the control of the UAV is shifted to the research pilot, who is tasked with flying the UAV. The M-GCS also houses an engineering station with a flight engineer who operates in a totally independent fashion from the research pilot.
The M-GCS computer collects the downlink telemetry data, nose-camera video, weather information, GPS time/position measurements, voice communication, as well as inputs from the R/C pilot, research pilot, and flight engineers. For the research pilot station, three displays are provided including an X-Plane®-based synthetic-vision primary flight display overlapped with a heads-up display that shows the flight parameters and mission constraints, a flight instrumentation display with a navigation window, and the real-time flight video transmitted from the aircraft nose camera. The research pilot commands the aircraft through a set of joystick, rudder pedals, and throttle handles. The precision and the high-precision repetitiveness of the test maneuvers is insured through the use on an OBES in the flight computer, allowing to inject pre-programmed specific maneuvers. The flight engineer has access to all available flight data and can change the aircraft operational mode and inject/remove failures with or without notifying the research pilot.
WVU has a full line of wind tunnels capable of providing sub-, super-, and hypersonic-test conditions. The tunnels are equipped with a full line of analog and digital sensors and measurement devices. Flow field quantification includes optical and thermal methods, and model force and balance quantification includes a range of strain gage and pressure-based methods. A brief overview is as follows:
- Hypersonic WT: Mmax= 6.0 (sustained)
- Supersonic WTs
- Indraft WT: 6”x6” TS, Mmax= 1.7 (sustained)
- Blowdown WT: 4”x4” TS, Mmax= 2.35 (burst)
- Subsonic WTs
- Closed-Loop WT: 3’x4’ TS, qmax = 8.5 inH2O (130 mph), TF = 1.08, TI <0.1%
- Environmental WT: 4’x4’ open jet TS, qmax = 2.8 inH2O (75 mph), TI<2%
- Reedsville Large-Scale WT (Eiffel-type): 16’x16’ TS, qmax = 0.6 inH2O (35 mph)
- Low Turbulence WT (Eiffel-type): 6”x6” TS, qmax = 2.5 inH2O (71 mph), TI<0.015%
- Demo Tunnel WT (Eiffel-type): 12” round TS, qmax = 2.0 inH2O (64 mph)
Test equipment includes stereoscopic particle image velocimetry system, laser Doppler velocimetry, hot wire anemometry system, multiple three- and six-component internal and external strain gage model balances, full-volume traverse system, and electronic support umbilical for Large-Scale WT.
It is important to note that many of the WVU wind tunnels open opportunities for a broad range of research. For example, the hypersonic wind tunnel is a likely candidate for use in picosatellite ground testing due to its unique ability to achieve extremely low ambient pressures while simultaneously being able to run at extremely high temperatures. The Reedsville large-scale tunnel is an excellent candidate for tethered and untethered free-flight testing of scale UAV and MAV models. The environmental wind tunnel can provide another free-flight test facility for MAV-sized UAVs, and can also be used in low and high ambient temperature as well as aerosol-rich test environments.
The WVU environmental wind tunnel features a subsonic open-loop design. The wind tunnel has a square cross section with dimensions of 16 feet x 16 feet. The tunnel was originally designed to study exhaust plume dispersion from vehicles and other ambient mixing problems. With that in mind, the test section length (115 feet) was set to achieve at least a two second residence time of the plume at a wind speed of 35 mph within the tunnel. The open circuit configuration of the wind tunnel guarantees no re-entrainment of the diluted plume exiting the tunnel.Figure 1: Exterior view of the Wind Tunnel Facility
Given the cross-sectional size and overall length, this environmental tunnel is also well suited for MAV free-flight experiments as well as live-bird flights.Figure 2: Sampling probe system inside the wind tunnel
The wind tunnel is equipped with a 10 ft propeller, comprised of carbon-fiber blades with adjustable pitch, and coupled to a 2200 Hp diesel engine capable of producing wind speeds up to 80 mph. Further, the wind tunnel inlet section is equipped with honeycomb screens to limit the turbulence intensity within the test section to less than 1%. A platform, which traverses the length of the tunnel is located above the ceiling of the tunnel and houses a suite of gaseous and particulate matter sampling instruments. The overhead platform is coupled to a two-axis sample extraction probe that can move precisely across the cross section of the tunnel to sample gases and accurately characterize the diluting plume in a three-dimensional matrix. The tip of the probe is equipped with a hot-wire anemometer, humidity, temperature and barometric pressure sensors in order to continuously monitor flow parameters. Figure 2 shows the sampling probe inside the wind tunnel.
Flight Testing Facility
The WVU team operates the Jackson’s Mill flight-testing facility, as shown in Fig.14. This is a University-owned property with a 1,000 meter runway in a remote rural area, which is ideally suited for UAV flight testing activities. A FAA certificate of authorization has been issued for flying Phastball aircraft at this airfield.
Additionally, an indoor flight testing facility with an eight-camera Vicon motion capture system is available for indoor flying, sensor calibration, and hardware-in-the-loop simulation.