Weeding Out a Solution

A UAS is to be designed for precision crop-dusting. In the middle of the design process, the system is found to be overweight.

Two subsystems – 1) Guidance, Navigation & Control [flying correctly] and 2) Payload delivery [spraying correctly] have attempted to save costs by purchasing off-the-shelf hardware, rather than a custom design, resulting in both going over their originally allotted weight budgets. Each team has suggested that the OTHER team reduce weight to compensate.

The UAS will not be able to carry sufficient weight to spread the specified (Marketing has already talked this up to customers) amount of fertilizer over the specified area without cutting into the fuel margin. The safety engineers are uncomfortable with the idea of changing the fuel margin at all.

Write a response describing how you, as the Systems Engineer, would go about resolving this issue. Use your imagination, and try to capture what you would really do. Take into account and express in your writing the things you’ve learned so far in this module: What are your considerations? What are your priorities? What do you think about the future prospects for the “next generation, enhanced” version of the system as a result of your approach?

While it is important that the vehicle both fly correctly and spray correctly there needs to be a solution to the overweight dilemma.  Reducing the weight of unmanned aerial vehicles (UAVs) pays large dividends in their ability to carry more fuel, support more advanced payloads (radar, imaging, sensors, navigation and guidance, uplinks and downlinks), achieve longer flight times, and operate from shorter runways (Oliver, 2012).  Both teams have decided on using off-the-shelf (OTS) hardware which has resulted in an overweight situation.  The fixed factors are the fuel and the amount of fertilizer.  Therefore, the only manageable means of navigating this situation is to design custom lighter options for guidance, navigation & control, payload control, increase propeller lift capability, increase motor size, or utilize a lighter design structure for the entire craft.

In most design projects it comes down to two very important factors; time and money.  Therefore, I will begin this project by mandating that each team compile a report that specifies the time and money required to design a custom solution instead of the OTS version.  By forcing the teams to figure out a solution within the design parameters, it will encourage creativity and possibly flush out new ideas or theories that can lead to breakthrough solutions.  The best case scenario is that one or both teams find an easy solution to the weight problem by either slightly modifying the OTS version or designing a new version that is within cost, time, and weight parameters.   Reducing the weight of the electronics, and especially the power-supply subsystem, is a major area for potential improvement (Oliver, 2012).     

Meanwhile, I will consult the propulsion department and have that department begin an evaluation to determine if a different type of propeller is capable of carrying the weight with no negative fallout in regards to the fuel or time aloft considerations.  If the propulsion department cannot produce a better lifting mechanism I will suggest investigating a larger power source.  However, I will stress that the power source must not use any more fuel than what is currently allotted per the original design specifications.  

Lastly, consulting with the structure design engineers may result in some ideas that will result in a lower overall weight to the vehicle.  I will encourage they investigate other materials that may be more durable and lower weight.  However, the cost consideration along with ability to procure material will need to be considered as part of the overall project goals and objectives. 

Ultimately, both teams have failed to fully analyze the problem and create a solution within their parameters which is unacceptable for the success of the project.  They need to go back to the drawing board and come up with custom intelligent designs that meet the demands of the project, thus keeping the project on track.  However, if neither team is able to accomplish a better solution than the OTS, I have consulted with other departments that might be able to offer a solution to the overweight problem. 

REFERENCES

Oliver, S. (2012, August). Take A Multifaceted Power Approach To Reduce Your UAV’s Weight:  Electronic Design.  Retrieved from http://electronicdesign.com/power/take-multifaceted-power-approach-reduce-your-uav-s-weight