Project Summary:   

        During the previous semesters, the Raptor 60, remote control helicopter has been studied by several project groups in order to design a vibration-isolated avionics box.  This avionics box will be used to protect sensitive electronic equipment such as inertia/GPS navigation and vibration measurement systems mounted onto the helicopter for the future goal of making the RC helicopter completely autonomous.  A previous group was able to mount the equipment to the helicopter, but equipment failure occurred during a flight test due to the harsh vibration environment. In addition, another group was able to design a vibration-isolated avionics box; however, their design was never flight tested. 

Project Goal:

        The goal of this project is to verify that the current vibration-isolation system has the capabilities to isolate the high vibrations created by the helicopter’s tail rotor, engine, and main rotor. This verification will determine the effectiveness of the system, via a flight test, on isolating the inertia/GPS navigation and vibration measurement devices mounted on board. If this current design fails, then a more effective vibration-isolation system will be designed. 

 

Drawing:

Figure 1 - Assembly Drawing of Vibration Isolated Avionics Box

Pictures:

Figure 2 - Side View of RC Helicopter with Isolation System Attached

 

Results:

        Overall, the testing phase, both bench and flight testing showed very positive results.  Bench testing was used to verify that the isolation system was functioning correctly. It also allowed us to understand how the overall system is affected by its different parts, such as mass placement, the actual avionics box lid and plate bending modes. The flight test was used to verify that the isolation system was capable of isolating the equipment to be contained inside the avionics box.  Through analysis of G forces and input frequencies we were able to determine that the system was achieving its goals of less than 0.5 Gs of acceleration for equipment inside of the avionics box.

        Included below is a sample of the data taken during the flight test for the z axis.  This axis experienced greater amplitudes of Gs than both the x and the y axis.  As can be seen by the two figures below, there is a great reduction in amplitude of G forces from the hard mounted accelerometer to the isolated accelerometer ( i.e. put in the vibration isolated avionics box).  The hard mounted accelerometer showed accelerations of between 8 and 15 times the normal force of gravity, whereas, the isolated accelerometer only saw around a 0.3 to 0.8 increase in the force of gravity during the same flight test.  While the isolated data did at times surpass the 0.5 G limit, it was for only milliseconds at a time.

Figure 3 - G Forces Experienced by Accelerometer in RC Helicopter at Low Flight Speeds

 

 

Figure 4 - G Forces Experienced by Accelerometer in Isolated Avionics Box in RC Helicopter at Low Flight Speeds

 

Group Members:

Jeff Hibshman -  (Bookkeeper)

Jeff is a Mechanical Engineer in his 8th semester here at Penn State University Campus.  Planned graduation is in December of    2004 with a B.S. in Mechanical Engineering with a focus in Engineering Mechanics and Structures.  After graduation from Penn State, he will be working with NASA at the Kennedy Space Center in Cape Canaveral, Florida.

jmh423@psu.edu