“Designing unmanned aerial vehicles has many technical challenges, on the fluid dynamics side as well as the software control side,” remarked Swaminathan Subbiah, the vice president of corporate product and market strategy at ANSYS. In my last blog, I talked about unmanned aerial vehicles (UAVs) and their use in reconnaissance in the military and commercial applications in industry. I also touched on how ANSYS software solved some engineering problems of UAVs. To find out how ANSYS was involved, I interviewed Suti Wirogo, the senior technical account manager, and Rob Harwood, the aerospace and defense Industry marketing director, both at ANSYS. We all sat down one rainy Friday afternoon to discuss the challenges of UAVs and how ANSYS can help to solve the devices’ engineering challengers.
Unmanned aerial vehicles design difference
With UAVs, there are no pilots, so the design and control systems will be very different from manned aircraft. “ANSYS fluid dynamics solutions can help you understand the aerodynamics of that system, so you can get it stable and do the maneuvers you want it to,” explained Rob. “Structurally, a UAV has to be light, because we want it to stay up there a long time and not burn up fuel. And it must be strong enough to withstand turbulence, landing and possible combat.” The way to analyze these factors is with structural analysis. Another issue is that the wings have to be very long and slender. Yet when air runs along a long, thin wing, it deforms the shape — which, in turn, makes the air perform differently. Consequently, that causes a lot of structural effects. “If you just look at the structural side, or just the fluid dynamics, you won’t capture the entire effect. So you need to be able to do multiphysics analysis, where you capture different effects in the same simulation,” Rob added.
UAVs are smart devices, so they contain many lines of control code that oversee their actions and allow them to interact with the environment. Concerning testing this embedded software, the recently acquired software Esterel plays a key role in the development of autonomous aircraft. In the future, if we want UAVs to fly for long periods of time without a human in the loop, we have to be sure that the devices inherently know what to do. UAVs currently still have humans directing them –– giving them objectives and coordinates to fly to, or actually flying the drone from a base location. Rob explained, “If there’s even a small glitch in the program, you don’t want a UAV to be flying over Afghanistan and keep going and end up in Iran, like the Sentinel did.”
Therefore to make sure the software knows what to do, Rob described Esterel software, which “tests to a very high degree whether or not your code is error free.” Esterel simulates certain conditions, such as a command, to make sure that the embedded software knows what to do. “If you think of how many millions of lines of code are embedded in UAV software, Esterel is especially important in simulating code to test the embedded software,” Rob added. With autonomous aircraft, the software control has to be able to respond to conditions and immediately issue commands. For example, if a plane is flying over mountains, and a gust of wind destabilizes the plane, the UAV’s software must react and tell the drone what to do so that it stabilizes itself. Esterel tools play a role here by simulating that gust of wind. With simulation, you can model all these effects without having to build countless prototype models. Therefore, as Rob said, “When you do try to fly the thing for the first time, you have a good degree of confidence it will work.”
So how are UAVs affecting warfare today? In truth, the answer is the reverse: drones are being made in response to how warfare is changing. Visualizing war, I imagine tanks lined up on either side of a line, mirroring each other with equivalent firepower. That symmetry is now asymmetric, where on one side there’s all the technology, and on the other side, a few guys with explosive devices. Yet the latter side can do considerable damage. UAVs were developed to fight terrorism. They can provide constant surveillance to pick up people’s behaviors or patterns. It was a UAV drone that monitored the compound where Osama bin Laden was believed to be; and later an attack was issued that resulted in his death. UAVs are important for reconnaissance, by flying longer hours and providing constant watch. By taking pilots out of the equation, UAVs also reduce the risk of missions and casualties.
Throughout the development of these drones, ANSYS contributed toward UAV design with its structural, aerodynamic, and embedded software simulation. Looking toward the future, UAVs will get only more and more fine-tuned with the help of ANSYS. They will eventually spread beyond the military, expanding to more commercial purposes. For now though, “from a military perspective, Pandora’s box is open,” said Rob. “These things are going to proliferate like crazy.”