Lab 4: Unmanned Aerial Systems Mission Planning

Introduction

Unmanned Aerial Systems (UAS) is a technology that the professor, Joe Hupy, knows quite a lot about. Because this is a quickly growing industry, he was eager to have us conduct a lab on the importance of mission planning for various projects and to learn the logistics of flying a simulator unmanned aerial vehicle (UAV).

For this lab, we were given the task of logging two hours on the simulator. Thirty minutes for four different platforms, or vehicles. Two of these had to be fixed wing and two had to be multi-rotor. A fixed wing is like a standard airplane, whereas a multi-rotor is more like a helicopter with multiple rotors (see figures 4 and 5). This variety was set to give the students an array of flying experience to determine which platforms should be used in future flight missions as well as getting a handle on flying them for the future UAV course offered next fall.

The UAVs typically have a computer programmed into them which serves as the 'auto pilot'. That being said, in no way should you rely on that to keep the UAV safe from harm. Endless issues could occur that would require the user of the remote to be needed including a change in wind conditions, computer programming error, unaccounted for trees or buildings, or a motor burning out. Typically, someone setting out on a UAV mission should have at least one other person with them, but it is best when there are three people in total: one to run the computer, another to serve as the remote user, and a third which serves as a spotter. In addition to the UAV's ability to be controlled by computer and remote control (see figure 1), a number of add ons can be attached to the vehicle. This includes, but is not limited to cameras, thermal imagery, remote sensing, and moisture sensors.

Figure 1. Remote controller for RealFlight flight simulator.

The flight simulator program (RealFlight 7.5) is designed to reduce the number of user/ environmental errors once out in the field.   The simulation allows the 'flier' to change various conditions (updrafts, wind speed) as well as the vehicle (anything from a blimp to a fighter jet) and flying location (a swamp, carnival, or flight school just to name a few). In addition, the flier can view the simulation in multiple modes such as on-flight, trailing (see figure 2), and ground view (see figure 3). While on-flight is the most fun, we were strongly encouraged to view it mostly in ground view, considering that none of us would ever experience actually flying on an unmanned vehicle.



Figure 2. A 'trailing' view in the RealFlight simulator.

Figure 3. Screenshot of the Aerial Field and its on screen virtual goggle view with the capabilities to see the angle and navigational direction of the UAV, and distance from the RC home base as well as the battery level.

There are a couple of main reasons why someone would want to use UAVs including its relatively small cost compared to a manned airplane or helicopter. In addition, because of its small size, it can get much closer to the desired location, thus giving a much higher resolution of imagery.

Methods

In order to get a bearing on the handling of the UAVs, the class needed to individually spend at least two hours using the flight simulator. In this time, a log was to be kept in order to get a better sense of how various vehicles operate in different conditions. In the log there were different sections which allowed the individual to look back and analyze how different conditions make it easier or more difficult to operate a vehicle. In addition, after the simulations were completed, the individual had a much better understanding of how the different platforms operated, which mission they would be the most successful in, as well as understand where their skill level was at for various platforms.

Two of the fixed wing UAVs were the Slinger and Yak-54 (see figure 4). The Slinger was a more difficult vehicle to run in my opinion because of its take off which seemed more temperamental due to the nature of manually having to angle it before launching it. If the start off was not solid, there was no easy way to correct it. The Yak-54 was easier in that it was more stable in the take off and while it was in the air. Because of the nature of the vehicle, it could travel at 70 miles per hour, which made it difficult to control closer to the ground without nose diving. However, when it was higher in the atmosphere, it was smooth sailing.

Figure 4. Fixed wing UAV, similar to the Yak-56 used in this lab.

The two multi-rotor UAVs that were flown were the Hexacopter 780 (6 motors) and the Octocopter 1000 (8 motors) (see figure 5). Both were quite easy to fly, but there were a couple of slight differences. The Octocopter did a lot better in windy conditions than the Hexacopter, but it was more difficult to move the Octocopter around. The Hexacopter would be better in tight fitting spaces with low wind conditions, say a more rural setting, whereas the Octocopter would be better in an open field. For both of these UAVs, the reason for crashing was that the battery died. The Octocopter seemed to last longer (17 minutes airtime) whereas the Hexacopter only lasted 13 minutes. This was surprising because the battery life should be shorter on a UAV with more rotors. This could be potentially due to different weather or platform conditions.

Figure 5. Multi-rotor UAV. The two multi-rotor UAVs that were used in this lab were the Octocopter and Hexacopter. 

Here is the flight log that recorded the flight logistics for all of the platforms (see figure 6).

Figure 6. Flight log.

In addition to using the flight simulator, the class was given the task of building off the knowledge received in the simulation by applying it to two flight mission scenarios. The response to these scenarios were to be written as if the audience was the client. Here is one of the missions:

' A power line company spends lots of money on a helicopter company monitoring and fixing problems on their line. One of the biggest costs is the helicopter having to fly up to these things just to see if there is a problem with the tower. Another issue is the cost of just figuring how to get the things from the closest airport'

Dear Client: As was brought up in your concern with using a manned helicopter, it is difficult and costly to figure out the logistics of using a vehicle of that size. By utilizing a UAV, the need to use an airport to launch the vehicle would be eliminated. In addition, because the UAV is much smaller and unmanned, it is quite versatile and it will be significantly cheaper than using a helicopter. In order to keep the power lines, tower, and UAV safe, it is recommended that you use a multi-rotor vehicle due to its capability to hover and thus take detailed pictures of the tower. So you are aware, the more rotors there are on a UAV, the shorter the time it can stay charged, but according to your description, a greater lift from the rotors will provide you with a UAV that can take off very close to the site. In addition, more check ups on the tower can be utilized with the UAV because of the much lower cost in operation, thus allowing a higher customer satisfaction in the ability for the power lines to be working at a higher rate of success.

To be able to fully utilize the capabilities of the UAV for your project, I suggest using an ultraviolet (UV) detector, which would be able to detect the inconsistencies and wiring issues on your tower system. IHS Engineering 360 has what you are looking for, and here is more information regarding its uses and benefits.

This is scenario number two: 'A pineapple plantation has about 8000 acres, and they want you to give them an idea of where they have vegetation that is not healthy, as well as help them out with when might be a good time to harvest.'

Dear Client: Unlike using a manned helicopter to do the imaging for your field, a UAV would be able to provide you with high quality photographs and GPS coordinates that would allow you to see the when harvesting would be appropriate. Because UAVs are inherently cheaper to fly than a manned vehicle, you could fly a UAV more often to benefit the health of the crops as well as be able to monitor their growth. For your needs, I would use a fixed wing vehicle that would allow for long flight times (about an hour) as well as an easy ability to fly in a straight pattern to accurately cover your entire field.

Here is a scholarly report about Rice Crop Monitoring with Unmanned Helicopter Remote Sensing Images. This will give you an idea of how to read remote sensing data for your field. AIRSAR (Airborne Synthetic Aperture Radar) would be a good option to measure biomass of your pineapples. The Gimbal, which is a support that allows for angle rotation of on-flight devices, would be perfect for viewing the field with multiple angles, thus giving a better idea of crop conditions (see figure 7).

Figure 7. Gimbal attached to a DSLR camera which allows the camera's angle to be mechanically changed during flight.  

In addition, using an NDVI, or Normalized Difference Vegetation Index, will provide imagery which will easily determine the health of the pineapples (see figure 8).

Figure 8. NDVI imagery of fields. The green is healthy vegetation, yellow is dry or dormant plants, and brown is plowed fields or bare ground. This imagery would give a detailed view of the moisture content of the plants. 

Discussion

If I were to use more time for using the flight simulator I would definitely use it on the fixed wing vehicles. I found that they could be taken much easier windy conditions, and unlike the multi-rotor, it is much harder to stabilize for longer periods of time. However, using the simulator with the multi-rotor made it somewhat difficult to detect where the camera was facing from the ground level. I believe with more practice, this will get easier.

During the simulations, there was often an obstructed view of the UAV due to buildings, trees and land forms, and the sheer distance that was often between the ground view and the vehicle. This all played a part in the success of each flight. Most often I kept the view in ground mode to replicate a real life situation, but sometimes it was necessary to put the simulator in first person mode to track where the UAV was. A big help was the virtual goggle view that showed the direction of 'home', and its distance, as well as a few other helpful pieces of information (see figure 3). This setting was vital when using the Hexacopter 780 because the 60 mile per hour winds carried away the UAV without any hope of bringing it back.

The flying styles between the multi-rotor and the fixed wing UAVs were difficult to get used to. Whereas the multi-rotor UAV could be held steady by basically using the pitch (right joystick)(see Figure 1), the fixed wing's pitch joystick had to be flicked downward in order to stay in flight.

Conclusion

At the start of this lab, I had absolutely no idea of how UAS worked in the slightest. On the day that we had a trial run in class to test it out, I failed miserably at keeping the UAV in the air for more than 30 seconds. Since having two hours of flight under my belt I really feel like I have more of a handle on it. I realized that multi-rotor UAVs are much easier for me to control, yet they are better for covering smaller areas with a need for hovering abilities. I am really glad to have had this lab to better understand this up and coming technology that allows better and cheaper mapping of a multitude of scenarios.