UAV Design Challenges: Game On

Amazon Prime Air—the company’s proposed package delivery service of the future, will deliver packages up to five pounds in 30 minutes or less using small drones. According to Amazon, the UAVs will fly under 400 ft. and take advantage of sophisticated “sense and avoid” technology, as well as a high degree of automation, to safely operate beyond the line of sight to distances of 10 miles or more.

Amazon’s announcements have encouraged others considering drones for this type of use, and many others.

According to market research conducted by the firm Tractica, drones are expected to grow in number from about 80,000 units today to nearly 2.7 million in 2025. They expect this surge in drone production and use could generate revenues of $8.2 billion annually.

For many design engineers, this is a whole new arena. Within it are components that make it go: highly engineered sensors that use wireless channels. Designers will test their innovation savvy by creating UAVs that meet the limitations of size, weight and power. Their efforts could mimic the ingenuity of Orville and Wilbur Wright as they pioneered flight, against the odds, over 100 years ago. However, design engineers face many challenges in the incorporation of sensors in UAV design.

SWAP: Size, Weight and Power

According to Raghvendra Cowlagi, assistant professor in the Aerospace Engineering Program at Worcester (MA) Polytechnic Institute, the main challenges are summarized in what is called SWAP: size, weight and power.

“Bulky sensors introduce undesirable aerodynamic drag,” he says. “Heavy sensors can cause undesirable shifts in center of gravity location, which in turn can cause instability during flight, and call for expensive design modifications to produce additional lift to sustain the heavy sensors, or reduce the amount of fuel [or] size of batteries that can be carried—and consequently reduce duration of flight. Similarly, sensor power requirements directly and adversely affect the UAV flight time, because all power supplies, either batteries or fossil fuel engines, must obviously be carried onboard.”

Dr. C. J. Reddy, vice president of Business Development for Electromagnetics at Altair, also sees SWAP as the pervasive challenge. “Most of the UAVs are usually much smaller than any other platform—fixed wing aircraft or rotorcrafts,” he says. “And also [the] size of UAVs are decreasing to make them more viable for commercial use. This limits the real estate on the UAV to place different sensors. Weight of the sensor contributes to fuel consumption and power requirement adds to the battery power and size of the battery onboard.”

Each UAV requires a multitude of sensors to provide operating feedback and collect in-flight data. Image courtesy of MEMSIC.

Another option is to build larger drones, such as the SB1 that SkyBridge UAS designed and is initially being used for precision agriculture applications. The SB1’s fuel-injected engine and on-board generator provides up to 60W of electrical power for avionics and sensors, according to the company. At the Siemens PLM Connection conference last month, SkyBridge COO Ian Henderson said the multi-spectral infra-red sensors used in precision ag only account for about 2 lbs. of payload, leaving an additional 20 lbs. of payload that can be used for other sensors. SkyBridge engineers used Siemens PLM Software’s Solid Edge to design the SB1 to accept pods of different sensors so it can be easily adapted for different uses.

Connectivity

Connectivity poses another set of challenges. The wireless channels by which UAVs operate can be a limiting factor when deploying them.

According to Derek Campbell, a senior applications engineer at Altair, wireless connectivity is rapidly expanding in both popularity and potential, and will be useful in connecting with UAVs and their sensors via antenna arrays.

“Incorporating antenna arrays on both ends of the wireless channel realizes this potential by facilitating beam steering and increased directivity. From an operations vantage point, these capabilities reduce transmit power, increase data rates and extend communication range,” says Campbell. “Antenna arrays also facilitate forming nulls toward antagonistic regions to hide information and thwart easily accessible jamming devices.”

Campbell adds that these performance characteristics of antenna arrays address several critically important challenges for UAV operation. Maintaining wireless communication channels over extended ranges that can potentially cross into antagonistic regions helps accomplish precise, adaptable mission objectives. In addition, efficiently utilizing power, a scarce commodity often drawn from solar panels, facilitates extended flight durations. Finally, the reduced transmit power also reduces the aircraft weight that can further extend flight duration.

Integration and High Performance

As a way to address various UAV operating requirements, some engineers may turn to higher levels of integration, notes Chris Winkler, senior product manager for Emerging Markets at MEMSIC in Andover, MA. MEMSIC provides component and systems solutions for a variety of advanced sensing applications.

“There are many performance benefits to integrating common circuits and sensors on monolithic ICs (integrated circuits),” he says. “For example, devices can often achieve better symmetry—not pulling units from different wafer lots, smaller parasitic effects on performance due to elimination of extra connections and wire bonds. There can also be optimization of trimming and calibration by devices being integrated and on-chip rather than discretely connected.”

Winkler adds that the greatest impact of integration comes from improved cost structures and reduced component size. The ability to shrink devices and place them into smaller form factors, with lower weight, is critical to SWAP and expanding their reach and growth.

According to Phil Solis, research director of Semiconductors and Strategic Technologies at ABI Research, sensor designs and overall UAV design will be ramping up to meet the demands of high performing UAVs. He predicts that you will see more semiconductor vendors doing what Qualcomm did – reworking smartphone-integrated platforms and sensor hubs to be used for UAVs as well as other robotic products.

“These markets are experiencing explosive growth with new applications rapidly appearing at a break-neck pace,” says Winkler. “Consider that drones and UAVs will replace many functions that humans perform today – and doing them more reliably and ideally more safely: Delivery of medical supplies, surveying and monitoring in remote hazardous locations and law enforcement to name a few.”

More Info

• ABI Research
• Altair
• Amazon
• MEMSIC
• Siemens PLM Software
• SkyBridge UAS
• Tractica
• Worcester Polytechnic Institute