Inside Ingenuity with AeroVironment Part II: Challenges Overcome

Inside Ingenuity with AeroVironment Part II: Challenges Overcome

Early rotor take a look at on the Mars floor. Photo courtesy of NASA/JPL-Caltech/ASU.

As of Friday, April 30 (native time), the Ingenuity Mars Helicopter had accomplished its fourth profitable flight, exceeding expectations and transferring from being a technical to an operational demonstrator.

In Part One of “Inside Ingenuity with AeroVironment—Designing It,” key personnel from the corporate talked about designing and creating Ingenuity’s airframe and a few of its main subsystems, together with its rotor blades and hub and management mechanism {hardware}. They additionally mentioned how AeroVironment labored with JPL, Lockheed Martin and others to combine its work right into a car able to reaching and working on Mars.

Now, in Part Two—”Challenges Overcome”—the engineering workforce recollects surmounting obstacles so Ingenuity and its 4-foot rotor blades might grasp the ultra-thin environment of the pink planet.

Comments have been edited and reordered for readability. 

Jeremy Tyler [senior aeromechanical engineer, with AeroVironment for 14 years, significant mechanical design work for most of the metal and plastic components: servos, linkages, swashplates, landing gear, hinges, springs, latches]

Thermal growth was an enormous problem. The working temperatures on Mars are extraordinarily chilly, typically, however they’re additionally very broadly various—it may very well be unfavourable 100 Celsius, or it may very well be optimistic 20 Celsius.

But even that isn’t the total vary. Every part of the helicopter needed to be utterly disinfected. For easy issues, we might wipe them down or soak them in alcohol. But there have been quite a lot of elements that wasn’t appropriate for; for instance, partially assembled buildings, that could be broken by alcohol, during which case we needed to bake them in an oven. And so we had very excessive temperatures that the issues needed to survive, whereas additionally having the ability to face up to the low temperatures of service. And so it was a unbelievable vary of necessities.

Also, a big portion of the aim of the Perseverance mission is to search for indicators of previous life. And that is in all probability essentially the most essential Mars mission to this point when it comes to organic cleanliness when it arrives. So, that was an enormous hurdle—each part needed to be designed to be washable; each captured house on each captured part needed to be accessible, such that it may very well be completely disinfected. Even from the mechanical design, we needed to determine in disinfecting—an enormous problem.

Matt Keennon [AeroVironment technical lead for rotor system development and an AeroVironment principal electrical engineer. Joined AV in 1996 and has worked mostly on micro-nano UAVs]

And that is our first house venture. So we had so as to add all this into our plans and our budgets. It was an enormous deal: they got here out with their gloves and petri dishes and swabs. And they had been inspecting us and taking samples from our work areas. It was intense.

Keeping it clear, with Ben Pipenberg, Ingenuity engineering lead, and Sara Langberg, AeroVironment aeromechanical engineer. Photo courtesy of AeroVironment.

Systems Challenges

Ben Pipenberg [AeroVironment engineering lead on the program; senior aeromechanical engineer; joined AV in 2014; worked on sub-scale and larger demonstrators and the final build]

JPL dealt with just about the entire avionics growth, the entire modeling and simulation, the entire sensors. They had been trying to leverage a number of COTS {hardware}. The Bosch [IMU] sensor is a business off the shelf unit, the LiDAR system, the little cameras—each the return to earth and the GNC [guidance, navigation and control] digicam. Numerous the navigation processing was completed on a Snapdragon, which is just a little business avionics board.

[But] there was a number of customized design that went into making all of that work, and it’s all being interfaced into a number of customized boards that JPL developed.

Numerous the options you’ll be able to see on the helicopter had been straight a results of GNC necessities. For instance, flying in a Martian environment, there’s very low damping; you’re primarily flying a gyroscope. And so, quite than having an enormous rotor system, like what you’d usually have on a helicopter right here on Earth, we made a really, very stiff rotor system. And with a counter-rotating, coaxial helicopter like this, your internet angular momentum is due to this fact zero.

Making the rotor system actually inflexible considerably simplifies how one can management that helicopter. And so, a number of what you see on the helicopter when it comes to even the rotor blade form, very excessive taper, comparatively thick for the way low the Reynolds Number is on these rotor blades—that’s all for structural causes. And that actually defines a number of the rationale that the helicopter seems to be and is constructed the way in which that it’s. So despite the fact that we didn’t work on the GNC aspect, we needed to account for that in nearly the entire design features simply to make it controllable. And it was a really, very shut collaboration between the GNC people and the mechanical people.

Chinese Weights and Tennis Racquets

Sara Langberg [aeromechanical engineer; joined the program in 2016; started with testing, especially on the blades; moved into mechanical design and fabrication, especially composites. Also swashplate geometry and building loads models for the blades and how that interacts with the servos, plus landing gear system in general]

One of the opposite issues that happens once we’re spinning at such a excessive RPM is completely different hundreds dominate than there could be on Earth. So the blades are topic to 3 hundreds. There’s the aerodynamic load and an inertial load of the blade via its rotations. But there’s additionally the propeller second, which known as “the tennis racquet impact.” It’s the tendency of the blades at an angle to attempt to flatten themselves as they spin, and that’s resulting from having an off-axis middle of gravity like we do.

On Earth, that’s a comparatively small problem, and doesn’t usually must be accounted for. But as a result of we’re spinning 5 to 10 instances sooner on Mars, this impact actually dominates. In order to get the servo hundreds down and into a spread the place we are able to get good servo response, we added these counterweights, referred to as Chinese weights, to the rotor. If you have a look at the blades, there’s a hole carbon fiber cone on every of the blades and a tungsten ball within the tip that acts as a counterweight. That counteracts the propeller second impact, and it doesn’t attempt to flatten itself fairly a lot. They’re optimized to scale back the servo hundreds essentially the most at a hover situation.

Ben Pipenberg [We discovered the need] within the design course of on the primary full-sized helicopter. So that may have been like again in 2015. But there was one thing that AeroVironment had found with the excessive altitude airplanes on these propellers, as a result of these had been floor adjustable fastened pitch. They relied on primarily clamping the foundation of the propeller blades previous to takeoff. You set the pitch, you clamp the foundation of the blade take off, after which they might land after flying at excessive altitude, and so they’d all have de-pitched themselves.

And so, one of many actually senior scientists right here introduced up that that is in all probability going to be an issue. And yeah, it’s an issue.

Matt Keennon: And it’s not solely the rotation of the whole blade, however the blades are literally twisted. And they’re really attempting to untwist and develop into flat. So it’s not solely grabbing or counterweighting the entire blade, however it’s really making the blade torsionally stiff sufficient. And that was one other driver that fed into the mechanical design of the blades, which once more, comes from our excessive altitude plane propeller designs.

We don’t need to add mass to the blade, however we are able to’t have them untwisting, we are able to’t have them unfeathering. So issues upon issues would crop up, after which we’ve got to resolve them in ingenious, light-weight, intelligent methods. Our background doing these different bizarre, light-weight, small plane, even just like the Hummingbird, helped us take into consideration these items another way and clear up them.

Jeremy Tyler: So, on prime of all that, the rotor blades are very extremely cambered, is a really extremely cambered airfoil, which is sort of uncommon for a rotorcraft, or at the least for a cyclic pitch rotorcraft.

Matt Keennon: It’s inherently unstable. It can’t fly for a half-second with out making selections primarily based on the IMU and driving the management system. We’ve tried flying such a helicopter with no management system. It goes dangerous rapidly. It’s simply the configuration of a coaxial helicopter.

Jeremy Tyler: The coaxial router system has no gyroscopic damping by any means. So with no digital controller, with no gyro-based autopilot, it’s completely uncontrollable. It’s very similar to a quadrotor could be with out avionics system.

With all these aerodynamic a great deal of flying and camber and twist, nonetheless the inertial hundreds had been dominant. And so Sara’s evaluation, designing these counterweights to ideally steadiness the inertial hundreds to the aerodynamic hundreds, allow us to actually optimize the servo weight and actually decrease the scale and energy that was wanted for these servos to get the bandwidth that was required from the GMC people at JPL.

Part 3: The Meaning of Ingenuity will seem later this week.

AeroVironment president & CEO Wahid Nawabi, up shut with Ingenuity. Photo courtesy of AeroVironment.