projdesc

2.0 PROJECT DESCRIPTION AND OBJECTIVES

This section presents a project description of the hummingbird research as well the objectives of Ultra Flite and IMB. Section 2.1 describes in detail the progress, results, and suggestions of the previous research team on hummingbird aerodynamics. Finally, this section is concluded by listing the goals and progress of the research of Ultra Flite. 2.1 Previous Research In the Fall of 1997, Alex Meyer and Stephen Serniak, of IMB, became the first group in ASE 363 Q to study the motion of hummingbird wings in hovering flight. As a result, a significant portion of their research is derived from background information and theory relevant to their project. IMB had four main goals in their study of hummingbird characteristics for adaptation to micro air vehicles. First, they wanted to develop a comprehensive dynamic model of the hummingbird in hovering flight. This included filming the bird in hovering flight in order to analyze the geometric locations of various points on the wings, body, and tail. Second, Meyer and Serniak wanted to create an I-DEAS model that could be used in future analysis, as well as to outline their progress and results over the course of the project for future groups. After obtaining the data from filming and from the model, the third goal of IMB was to relate their results to MAV technology. Finally, the team’s fourth goal was to conduct an aeroelastic analysis using MSC/NASTRAN.

IMB began their research by looking at possible applications of micro air vehicle technology. The four applications which appeal most to military and commercial sponsors are battlefield assessment, chemical leak sites, fire fighting, and target applications. The U.S. Navy expressed interest in developing small, unmanned vehicles to serve in reconnaissance missions hazardous for pilots. Another possible application of MAVs is the assessment of chemical leak zones without risk of exposure for people involved. By using an infrared sensor, MAVs could be used to locate people in burning buildings. This could keep firefighters safely away from danger. Finally, the MAV could be used as a prospective target designator for planning military strikes.

IMB’s next task was an evaluation of the choice of hummingbird for an MAV model. They concluded that hummingbirds possess many capabilities that make them a perfect candidate for an MAV model. Hummingbirds are able to maintain hovering flight, are very small in size, and are very quiet. This allows hummingbird-like MAVs to be used in small places as well as in covert missions. The hummingbird’s unmatched maneuverability and its ability to instantly transition between flight modes are the reasons why the hummingbird was chosen to be modeled and applied to man-made mechanical systems.

The next phase of the project included filming the hummingbird in hovering flight. IMB first researched an investigation by Bret W. Tobalske and Kenneth P. Dial on how birds, that differ in structural characteristics, change their wing and body movements while flying at a range of speeds. The birds were placed in a variable-speed wind tunnel and videotaped. Lateral views of the bird were obtained through the side of the flight chamber, and dorsal views were reflected from a mirror mounted at a nominal 45º angle to the top of the chamber. Strips of red tape were attached to identical points on the body of the birds in order to provide for anatomical references in later analysis. IMB opted for a similar setup to that of Tobalske and Dial, which is shown in Figure 2.1.

Figure 2.1: Fall 1997 Test Setup Model Environment [3]

A clear glass box was used to contain the hummingbird, Bob, so there was no obstruction during filming. White paper was used around the box to produce a greater contrast between the bird and the background when viewing the videotape. A high-speed video camera, belonging to the Department of Mechanical Engineering at The University of Texas at Austin, was used to film the hummingbird in hovering flight.

The camera has the capability to record at up to 2000 frames per second. In order to store footage, the data had to be sent to a VHS video recorder. The VHS video was converted to digital format using Apple Video Player. From the original movie file, a program named Sparkle created a Quick Time movie that was used to cut the film into a series of single image files that could be analyzed. Next, the movies were cut into a series of PICT files. Four images were chosen by IMB to be filtered and used in order to determine various points along the wing and body of the bird. The group wanted to verify the difference in size between the image of the bird and the actual bird to see if the modeling process would be valid. Problems quickly surfaced due to the lack of contrast between the bird’s body and wing. Furthermore, the bird was not correctly oriented during filming. Lacking a clearly defined picture of the bird’s wing, Meyer and Serniak concluded that an accurate characterization of the geometry of the wing during flight would be unobtainable. Consequently, the two used Adobe Photoshop 4.0 to place points around the hummingbird image for analysis. Figure 2.2 shows the points that were created to determine the geometry of the hummingbird. After the coordinates of the images were recorded, IMB input the data into an Excel file. The averaged points for the top and side views were plotted in a Microsoft Excel Spreadsheet in order to produce Figure 2.3 and 2.4.

Figure 2.2: Image of Hummingbird Ready for Point Determination [3]

Figure 2.3: Excel Graph of Averaged Top View Points [3]

Figure 2.4: Excel Graph of Averaged Side View Points [3] Moreover, the node coordinates were entered into a finite-element program in order to create a finite-element model using SDRC’s I-DEAS modeling package. The team created two independent, two-dimensional cross sections of the bird. Figure 2.5 shows the side view of the model, and Figure 2.6 on the next page shows the top view of the model.

Figure 2.5: Side View of I-DEAS Model of the Hummingbird [3] They concluded from the side view that the two cross-sections were not properly aligned with the axes, and therefore the model was useless for obtaining data about the bird’s flight.

Figure 2.6: Top View of I-DEAS Model of Hummingbird [3] As the first team to study hummingbirds in hovering flight, IMB concludes their report by recommending areas of continuing research. Their first recommendation is to build a stable mirror assembly to ensure that proper orientation is maintained throughout the filming process. On the following page, Figure 2.7 shows a three-view of the proposed mirror assembly. The assembly would consist of a mirror and two pieces of wood cut at 45º angles. The side pieces of wood would add strength and support to the mirror assembly. IMB also recommends greater access to the video camera in order to increase the filming time. They suggest refilming the hummingbird in order to get better images of the bird in hovering flight. This could be done in two ways.

Figure 2.7: Multiple Views of Proposed Mirror Assembly First, lights placed inside the glass test assembly box could provide more contrast between the body and the wing of the bird during flight. Second, recording to the VCR using a Super-Video cable would reduce the resolution loss that occurs when transitioning from digital to analog format.

IMB accomplished filming the hummingbird, and they also provided a good foundation for future groups to follow by offering recommendations. They also began to analyze the geometric locations of various points on the wings, body, and tail, but they ran into difficulties since the image of the bird was not properly aligned. They created an initial I-DEAS model although it will not be used for future analysis. The group did not have enough time to relate their results to MAV technology or to conduct an aeroelastic analysis using MSC/NASTRAN.

2.2 Continued Research Ultra Flite consists of a Project Manager, George Chi, and two Project Engineers, Erol Cagatay and Jenna Harsch. The co-sponsors of the project are Dr. Peng Chai and Dr. Ronald Stearman along with the guidance of Tifenn Boisard. This project stems from a proposal for creating a micro air vehicle introduced by DARPA. The project is a continuation of last semester’s Study of Hummingbird Aerodynamics by Alex Meyer and Stephen Serniak of IMB [3]. IMB was the first group in ASE 363 Q at The University of Texas at Austin to study the motion of the hummingbird’s wings in flight. Along with their progress and results, Meyer and Serniak documented recommendations for future groups to follow. Ultra Flite implemented IMB’s recommendations as well as continued with new research for their own analysis.

The first objective, a recommendation from IMB, was to refilm the hummingbird. Better resolution and accuracy of the video was needed for future analysis of the hummingbird. The first step in refilming the bird was to coordinate the three departments involved in the experiment: Aerospace Engineering, Mechanical Engineering, and Zoology. The Department of Mechanical Engineering provided use of their high-speed video camera. The hummingbirds and test assembly are located in the Zoology Department, and the engineers are from the Aerospace Engineering Department. Ultra Flite built a mirror assembly that is properly aligned at a 45º angle with the horizontal. This allowed correct positioning and no movement during the testing process as in last semester’s project. The correct alignment of the mirror allowed for consistent results between filming sessions. Also, better lighting allowed for improved contrast between the bird and the background in the footage of the film. This provided a picture more suitable for the analysis of the hummingbird’s wing characteristics.

The second objective of Ultra Flite was to construct a space-frame model of the hummingbird. A step towards this objective was accomplished by using a CT-Scanner from the Geology Department to three-dimensionally model a preserved hummingbird body. The CT-Scanner uses x-rays that slice the specimen for analysis at certain thicknesses while simultaneously rotating it to get a three-dimensional model. This model can then be used to complete the third objective which was to use NASTRAN to analyze the space-frame model. An aeroelastic analysis can be done to the three-dimensional hummingbird model in order to study the unsteady loading on the bird during hovering flight. Finally, Ultra Flite wanted to relate their results from the filming and the aeroelastic analysis of the model to MAV technology. This would have allowed for the ultimate goal: constructing a robotic hummingbird.

After the midterm presentation and report, Ultra Flite restructured its previous four objectives for this semester. Due to time constraints and the degree of difficulty, Ultra Flite and their sponsors, Dr. Stearman and Tifenn Boisard, discontinued the aeroelastic analysis of the hummingbird. Also, more emphasis was placed on conducting and post image processing of the CT Scan. Also, since the aeroelastic analysis was postponed, these results cannot be related to MAV technology. Ultra Flite did, however, do extensive research on MAV applications.