2003-2004 Rochester Institute of Technology
Micro Air Vehicle Team


Research and Analysis

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Needs Assessment · Concept Development/Feasibility · Design Objectives and Criteria · Research And Analysis
Preliminary Design/Prototype · Flight Testing · Final Design


Research and Analysis

Airframe - Airfoil

The three selected airfoils, MH45, S5010 and S5020, were analyzed using three areas of aerodynamic research: experimental, theoretical and computational simulation. Published lift and drag data on the S5010 and MH45 airfoils existed at a Reynolds number of approximately 100,000, but no reliable data could be found for the S5020 airfoil. Computational simulation proved unsuccessful, so a student designed and fabricated balance was used to gather 3-D data on the airfoil.


Mechanical Balance


The three airfoils were also analyzed using two analytical methods, thin airfoil theory and an airfoil analysis package XFOIL. Some of the results from the XFOIL analysis, along with published data and RIT wind tunnel data are shown in the following plot.

The MH45 has very radical stall characteristics and the major drawback to the S5020 is the lack of experimental data, so the S5010 was utilized in our design.


Planform Analysis

After reviewing literature to determine the best planform shape for a low aspect ratio flying wing configuration MAV, it was concluded that a modified inverse Zimmerman planform would be utilized.


Initial RIT MAV prototype planform

Additionally, several MAV designs with planforms based on the inverse Zimmerman have been successful in the past:

Stability and Performance Analysis

Using the gathered airfoil data and aerodynamic performance equations, asignificant performance evaluation was performed in MATLAB to predict the flight behavior of the MAV. Two of the more important plots resulting from this analysis are seen below.

A stability analysis was also performed, but the results were considered questionable due to orginally questionable pitching moment data. Because of this, stability would be ensured through thorough flight-testing and accurate cg-placement.




Propulsion

The electric motor/propeller combination is pursued as the propulsion option to be integrated into the MAV. Experimental testing was completed to determine the specific electric motor and propeller to be used.

The two commercial propellers were tested with four different tip shapes: No change, A (Both Edges Rounded), B (Leading Edge Rounded), C (Elliptical). Each was tested with a Maxon Motor RE16. This motor was powerful enough to allow each of the propellers to be characterized at typical flight performance. Thrust and output rotational speed were measured for each propeller.


U-80

EP-0320

Testing narrowed propeller choice to:

  • EP-0320
  • EP-0320B
  • U80
  • U80B

Each of these propellers were then tested with two motor selections, the Maxon Motor RE10 and DC5-2.4. The propellers were tested at three sizes; 70mm, 75mm, and 80mm. For each of these tests the motor voltage and current was recorded along with the thrust and rotational speed. The plot below shows the propeller performance of the top four motor - propeller combinations.

 


Electronics

Testing was performed on the video sub-system to determine electrical characteristics and range performance. It was found that the system draws less current than specified (197mA vs. 230mA). The fixed voltage regulator circuit itself draws an additional 9.8mA under a no-load condition. The regulator circuit will draw an additional 1mA for every 100mA sourced. Due to concerns of the stability of solder tabs on the lithium-ion batteries and hoping to be able to recreate consistent test conditions, a testing pod was created using Styrofoam to keep components stable during testing. Concerns remained about fragility of the solder tabs as some batteries were destroyed when the tabs came off the cell. To address this issue, battery 'packs' were created to stabilize the tabs and provide a more solid connection point. Another concern was the use of a television/VCR combo at the receiving station. This television would not accept signals of less than a preset strength and was generally unreliable. A lab monitor was acquired to improve reception of the image and show images of less than perfect quality. The final round of video testing was performed to assess the impact of the new acquisitions and actions. Results reached their best performance to date, a 457 meter range was realized with no degradation of signal quality.


Video system testbed

Control system testbed


Before attempting to test the control system response from a great distance, another testing platform was created to house the receiver unit, speed controller, and one servo securely. Results were in line with specifications. A range of approximately 805 meters was achieved with preservation of discrete servo motion. The unit became non-functional at a distance of approximately 1100 meters away from the control unit. Current use statistics for the receiver and servo units are as follows. The receiver draws 18.4mA in a static condition with no servo motion. Current peaked at approximately 190mA when the servo is induced to operate at full speed.

GPS System

The final selection for the GPS receiver was the Sarantel SmartAntenna because it was extremely lightweight, has a fast refresh rate, was within the budget, and has an omni-directional antenna. The final selection for the video overlay board was the BlackBox Camera Company's STVPROJ-G because it was the only one of the three overlay boards that operated at 5V.

The Sarantel SmartAntenna was chosen as the GPS receiver for the MAV. The GPS data will be interfaced with the STVPROJ-G video overlay board seen below. The video overlay board will intercept the video signal from the camera, overlay the GPS data on the signal, and then the modified video signal will be transmitted to the ground.


Sarantel GPS Antenna

Video overlay board

While testing the integration of the receiver and the overlay board, it was discovered that the overlay board has an RS-232 interface and the receiver has a 3.3V CMOS interface. To fix this problem a MAX232 transceiver chip was purchased. The MAX232 converts the TTL/CMOS voltage levels to the RS-232 voltage levels and vice versa. With the RS-232 transceiver chip the GPS receiver was successfully integrated with the video overlay board and the data was displayed on the TV.


Launcher

A table/ground based launcher concept was pursued for launching the MAV. Of the available methods of powering the launcher, a constant force spring was deemed most predictable and reliable. An analysis was performed using basic dimensions needed for the launcher to arrive at the amount of force necessary.


Simplified launcher schematic and constant force spring


Launcher calculations


Copyright · 2004
RIT Kate Gleason College of Engineering and the RIT MAV Team.