Ground Test

DP-5X prototype in 4DoF Test Stand

DP-5X prototype in 4DoF Test Stand

Ground testing at DPI is aggressive. Literally. Among the barrage of ground tests is DPI’s unique 4DoF (4 degrees of freedom) structure. This test stand grips the aircraft and, using a hydraulic brake system, shakes, rattles, and rolls the vehicle to isolate the axes and rigorously test the system. It’s as close to flying as you can get without leaving the ground. In fact, DPI is the only test facility in the world that does such extensive ground tests to significantly reduce risk.

That’s one of the reasons the DPI client list for UAV ground tests includes DARPA, Boeing, SAIC, the U.S. Army, and many other high profile designers and manufacturers of UAVs, systems, and subsystems.
DPI ground tests include:

  • Rotowhirl stand: Measures the performance of the rotor and blades as a unit.
  • Overspeed tests: These are safety tests.
  • Dynometer: Used to measure engine performance at RPM, in terms of RPM torque and horsepower, vibration levels, and fuel consumption.
  • Rotor and swash plate tests. DPI uses a load cell to measure the moments and forces produced by the rotor and swash plate. This information is then fed into a structural model of the airframe to identify issues and suggest potential solutions. We also measure the performance of the rotor head and blades early in the test process, and validate that performance against the design analysis.
  • Vibration test: DPI uses the vibration test to find the natural frequencies of components and the avionics structure. The tests are conducted on a rigid avionics rack vibration table. The table holds a non-rigid structure mounted on springs, and this floating spring structure includes electric motors that spin weights. During vibration tests, the weights and spinning rpms are varied to change and analyze the frequency and amplitude of the device under test.
  • Strap-down test: This is a shake-down strap-down test in which servos are excited to confirm appropriate rigging, the throttle governor is tested, and so on. The test delivers a vibration profile, records the electromagnetic (EM) noise on the power busses, and more.
  • Iron Bird test: Rotors often have significant torsional vibration that can affect performance. The Iron Bird test includes placing the drive system in a heavy, extremely rigid structure on the ground. The structure is used to measure the torque that is transmitted from the drive system to the rotors. That information is fed into a computer modeling program to quantify the vibrations and identify key points of potential strain.
  • Isolation: This isolation process is extensive, and is used to reduce risk during integration. In this process, we isolate the axes and test the system, introduce hardware (such as sensors), introduce software, integrate components (both hardware and software), and investigate failure modes and effects.
  • 4 Degrees of Freedom (4DoF) test: This test stand is unique in the world. It allows DPI to put the drive system into the fuselage, add the avionics, then grab the entire vehicle and “fly” it while it is anchored to the ground. The test stand allows extensive movement: The vehicle can pitch up and down 30 degrees, roll left and right plus or minus 30 degrees, yaw greater than 360 degrees, and heave 2.5 feet.
  • Break-in test: This is a 200-hour full drive system break-in test, which builds confidence in the overall system.

DPI: World Leader in UAV Testing

Rigorous testing for characterizing UAV systems and subsystems did not exist when DPI was founded back in 1992. In order to develop, test, and build reliable UAV, DPI also had to develop an extensive test infrastructure from the ground up.

With this test infrastructure, DPI can fully characterize and dynamically model the aerodynamic performance of the UAV, including all forces, moments, and inertias of rotorhead systems.

DPI is now the world leader in UAV testing. DPI provides these unique, world-class test services for UAV systems and subsystems designers and manufacturers, such as Boeing, SAIC, L3, HARRIS

Learn more: Contact DPI