Michelle Easter 'Mechatronics: Unconventional Pathways and Aerospace Applications



that's okay okay so my name is Michelle Easter I'm a mechatronics engineer at the Jet Propulsion lab I love my job is fantastic I've been there for three years so far and I'm specifically in the payload and small spacecraft mechanical engineering section in the mechanical engineering division I'll talk about that a little bit more later and more specifically the things that I'm going to talk about is kind of a mixed bag I want to talk about actuators and their role in aerospace and some of my experience with that and then I'm going to talk about dual Drive actuators specifically which are actuators that I'm building right now for a couple different missions their heritage the history and a little bit about the harmonic drives that go inside of them just because not everybody knows about them and I think they're super cool and then also some future JPL mechanism design challenges so at JPL we tackle some of the most interesting and difficult and never been solved before challenges and it's really rewarding to work on those so just some overview and then I want to talk a little bit about how I entered the world of mechatronics and how maybe you guys can too okay so I've only been in three years at JPL but I've worked on a lot of different projects because I have an interdisciplinary background and more of a hands-on kind of background as well so in the prototyping world I've worked on some gravitational offloading prototypes for a project that's called the planetary landing testbed its facilities that we develop at JPL in order to test our flight hardware on the ground I'm also right now I'm working on a project called pin optics which is a really exciting open-source Hardware project that is doing a global search for exoplanets by encouraging people to build robotic telescopes using DSLR cameras so asked me later about that if you guys are interested a little teaser also I've done some research and testing kind of stuff last year I got to work on the Europa Lander sampling system which was really cool and also I've done some characterization through cold testing of harmonic drives for the Mars 2020 robotic arm and more recently I've worked on some flight design and development including some conceptual design from our sample return which I'm going to get put back on this year CubeSat mission called tempest II which was an earth observing satellite CubeSat mission in central six which I'm working on now and Europa clipper which I just said you're working on as well they keep us very busy thank you okay so I know it's a mixed audience so bear with me I'm gonna try to be broad with my discussion so I work primarily right now on building actuators and actuators are any mechanisms that provide energy to operate another mechanism or system so the simplest example is like a motor a motor is an actuator and it can operate another system and they can get more complicated than that so actuators are important for a space we need to be able to launch stuff in a space it has to start small because it's expensive to launch things and so we have a lot of deployments this is an example it's not a JPL project but I think it's really cool it's a flexible solar panel deployment for the ISS and so this is a great example of how you can start out with a super small volume and then expand it to something really big and in the case of solar panels where they have a really low efficiency you need a big surface area so you really want to be able to make it super compact and then you want to increase the volume so actuators come in handy for that another really cool JPL project I see Allison getting excited back there is starshade so I got to work a very small amount just creating like a little mechanical fixture for aligning some of the petals onto this and a test phase but I just love this animation it's so cool starshade is a project that's going to be looking for exoplanets and it operates based on the principle where if you block out blinding incident light from a star distant away you could actually see the planets orbiting around it so it allow you to see more exoplanets around more distant stars and from a deployment standpoint you see there's two stages of deployment first the petals unfurl and the entire truss expands radially so it's two stages of deployment so it starts out really small and then the overall size ends up being about the size of a baseball diamond so getting that into a super compact form factor is really challenging and actually at JPL they work with origami experts in order to come up with this kind of design from an actuator standpoint I like it a lot because you actually only need one actuator for each stage of deployment so two actuators can create that kind of volume expansion it's really freaking cool and Allisyn raise your hand back there allison is a year-round intern working on that project right now so if you want to ambush her with questions later I encourage that okay so there's other applications for actuators this is the artist concept of the satellite that I'm working on right now which is called Sentinel 6 another intern back there was Morgan raise your hand that's my internet work right now feel free to ambush her later and tell me how she does please so this is an artist concept for the Sentinel 6 signal 6 satellite I mean I'm working on a microwave radiometer which is indicated there by the arrow and more specifically I'm working on the Supplemental calibration system which is a subsystem on the radiometer that helps to eliminate signal drift in the radiometer readings and the instrument itself will measure ocean topography levels on the earth so we're looking for a changing sea level rises so earth science ok so this is a very old original version of the actuator that I get to build right now it's a heritage device it's called the dual drive actuator it was originally invented by Doug Packard who is a freakin wizard we actually have him come in about one day a week he's like 85 years old and he's so smart it's really awesome because it's a single fault tolerant redundant actuator and that means that there are two mechanically independent drive systems within one actuator so two independent systems with one common output and that's really great because for mission-critical deployments or emotions that if we don't have those reliably the entire spacecraft will be worthless we want to make sure we have redundancy so if one system fails the other can still up and so just to point out here back here right here is where the drive electronics are in case we have commutation electronics that are mounted to the back of the motor right here and then this is a gearbox case and then these are two sets of harmonic drives and I'm gonna take a minute to talk about harmonics because they're really cool and I'm assuming raise your hand if you've heard of harmonic drives oh this is the best audience okay you guys are really smart so bear with me don't ask me complicated questions please okay harmonic drives are really awesome they're super compact low to no backlash drive systems they utilize the flexibility of metal to get big torque out outputs in a compact form factor so this is kind of an example of the way they work what you have is the driving input is called the wave generator it's represented by this green animated part right here and it's an ellipse as you can see and this red piece here is called a flex spline and it's a flexible piece of steel that's really thin and then the outer piece is a circular spline and what you get through the elliptical shape is if you'll notice you get a constant really strong press at the gear mesh and so that's how you get your zero to no backlash and because basically the teeth are pressing into each other and the metal is actually straining you get this added torque output from the strain energy contribution between the metals hence the name strain weight appearing so they're great and we use them for all kinds of robotic applications and industry uses them as well so these are our harmonics these are my babies on the left side you can see these are pancake style harmonics they're not commonly used but because we're building heritage actuators that were designed in the 80s we stick with what works it's the NASA way we know it works so we stay with it so this is what it looks like assembled and this is actually a picture right after we took them out of the oven in the cleanroom from making them clean and so you can see them disassembled these two parts are two circular splines the next went up you can see little ball bearings around the outside that's the wave generator and it custom ball bearings that fit around the outside and the top layer those are the flex lines so the cool thing about pancake style harmonics is the way that you get the output motion is one of your splines is called the static spline it's actually what you hardened mountain to your house and it doesn't move hence static spline the other spline is called the dynamic spline so it moves dynamic and so basically what you have is one spline you hardman into and then you drive the way it generated and the flex spline has a couple less teeth than the static circular spline so as the wave generator turns and that flex blowing turns you have a relative difference in motion because of the different number of teeth and so while the static splines stays still that an annex flying has the same number of teeth as the Flex blind and moves at the same rate in the opposite direction because it has less teeth so come bother me later if you didn't catch that and I'll explain it again but it's super cool and just to show you the scale look how small this thing is that's the Flex flying on the right side and the teeth are so tiny they're like paper thin and it still boggles my mind that they can transmit such high torques given the fact that they're so small and this is actually like I think it's a 10x zoom picture at harmonic Drive of the inspection of the final teeth of one of my Flex plans and so they're like perfect it's really impressive the way that they can machine these parts these are some shots from me fit checking all of my mechanical parts came in with dimensional discrepancies which was exciting in the wrong way and so I spent many an hour sitting down in mechanical inspection assembling things by hand to make sure that all the fits would be just right so this is some photo and video that I took to prove to my instrument manager that I was doing a good job and so this is a media bin assembly so I think Morgan's been there for these parts so on the left side we our testing the fit of the driveshaft and so the beauty of the redundancy is all in the mechanical interfaces which I can't show you details just frustrating but they're really cool you have to trust me but basically one system is driven by a central driveshaft and right there we had just finished installing it and that gear gets driven by a motor that plugs into the back there it's not shown yet and this is what we look like when we're almost fully assembled so this is a cool video to me because actually you can if you look closely you can see the elliptical shape of the wave generator so I'm actually rotating it from behind and you can kind of see that it's not a circle and you can watch it and you can actually see that while the wave generator is moving counterclockwise here this is the static spline of the second system which is being driven by the output of the first system and it's rotating in the opposite direction because of the difference in number of teeth between the statics part of a dynamic spline which this that explained is mounted soon so this is where my actuator will live on our instrument that's the actuator you see the two brushless motor assemblies here and in that mirror right there is actually what we're driving so in a subsystem that my actuator is working on basically we rotate this big mirror and it goes back and forth between looking at Earth and at cold space and then a warm target and between those three positions and we can tell we're always looking at okay so the dual Drive has been on lots of missions and we keep building it because it's really reliable and performs well and the first mission which actually it was invented for was Galileo Galileo was launched in 89 the dual drive was invented before I was born a little bit and Galileo was really awesome because it launched the first Jupiter probe it was the first to orbit Jupiter and it traveled almost three billion miles which is crazy I lived 14 years so it's really reliable and so Galileo was the reason that we found out that like volcanic and also that Europa is oceanic so we learned a lot from Galileo so this is a simple schematic of Galileo and the places that the dual-drive came in handy were for the high-gain antenna deployment which is a mission-critical function if the high-gain antenna which is the one that communicates back to earth doesn't deploy then we're in big trouble so that's why we need redundancy for deployment of something like that the other one was for the nutation damper and that was for basically damping the deployment of the science boom and lastly the probe relay antenna so there was pointing of the actual probe really antenna that communicated directly with the jupiter probe to communicate back to the satellite and that was controlled by a joule drive as well so I love this this is design news from 1983 and they have a feature on the dual drive actuator the Galileo deployment and one of the things that I haven't mentioned that I think is super cool about this actuator is that Doug Packard also invented the brushless DC motor when he invented this actuator he invented it for this actuator yeah just like and if you talk to him about this he's like oh yeah I told them they could do it without those brushes you know like I'm like wait what yeah so it's really impressive I actually have a hard copy of this magazine at my desk it's one of my nerd trophies amazing invention okay so another really obviously important mission from JPL was Cassini which we'll hear a lot more about later and there was a couple tool drives that were really important on Cassini as well so Cassini a couple fun facts I was launched in 97 so about a decade later it was the first to orbit Saturn and it traveled even further than Cassini or I'm sorry than Galileo at about five million miles of 20 years which is a crazy lifespan longer than some of the people in this room I'm sure are old and it was massive it was 12,000 pounds satellite which is crazy huge so this is a schematic of the different subsystems of Cassini and the places where dual drives lived we're right here which was the main engine assembly cover and for that when they were working on Cassini they got knee-deep into the bill then they realized that they were gonna have problems with micro meteorites basically bombarding the thrusters and potentially damaging it so they developed these deployable covers that would cover the main engine assembly when needed and then move out of the way when it was time to fire the thrusters and so this was another mission-critical motion that required redundancy hence the dual drive the other subsystem was the articulated reaction wheel mechanism and reaction wheels are used for pointing for spacecraft and so if we wanted to steer this sucker we better rely on it being able to do what we want it to do hence another dual Drive so this is actually a picture of the larger version of the heritage dual drive so the first one that I showed you guys before was a size 14 this is the size 20 it's bigger and a higher torque rating and there's actually a clutch on the output and this was the actual model that was used to drive the main engine assembly covers and this is also the model that I get to build for clipper super stick without the clutch other implementations for the dual Drive have been for several shuttle missions because since shuttle missions involve human spaceflight they require triple redundancy and so this amazing genius wizard woman Laurie Sheree she who works with us at JPL actually delivered a try drive which was a dual Drive driven by a dual drive wheel drive inception for the shuttle mission so that they could have dual redundancy okay so there's a lot of really awesome future mechanisms that we get to work on at JPL so when I mentioned earlier is Europa clipper so I'm delivering that larger dual drive that I showed you guys just a minute ago for the deployment of the ice mag beam the ice mag is a really awesome magnetometer instrument that's going on clipper clippered clipper is going to orbit Jupiter and specifically focus on studying Europa and in case you guys don't know we have tons of evidence convincing us that there are saltwater oceans under the thick icy shell of Europa and so we have a lot of optimism that they could potentially host life since it's warm in salt water so ice mag will be determining the ocean depths salinity and also the ice shell thickness around the outer layer of Europa and also be able to identify plume activity in Europa okay so this is super different route but I'm equally excited about it so I've gotten to do some conceptual development for the Mars sample return missions Mars sample return is a really awesome series of missions that JPL is working on so I'm sure you guys have heard of curiosity the rover so we're working on building another Rover it's called Mars 2020 and so that's represented kind of here and basically the concept for Mars sample return is the Mars 2020 launches lands on Mars it has a really Road sampling system that packages samples and deposits them across the surface of Mars a future mission that we're working on is going to be a fetching Rover and it's going to be in charge of fetching these samples that have been deposited and packaging them up into an orbiting sample capsule we call it the of the acronyms keep popping into my head I'm trying to push them out so the fetching rover then goes to another future mission which is called the MAV the Mars ascent vehicle Mars ascent vehicle is in charge of taking these package samples and then launching them into Martian orbit so now imagine you have this capsule that's filled with these samples of Mars rocks and it's orbiting around Mars then the next mission is the Mars rocks our OCS which I need to learn that acronym but basically it's an instrument on a Mars orbiting satellite that is then in charge of intercepting that sample pod in orbit capturing it doing a process that's called breaking the chain so giving us a less than one in a million chance of any potential contact between any Martian particle and earth breaking the chain and then taking that capsule and launching it back to earth and crash-landing in the Utah desert so that we can retrieve it and study the samples here on earth with a much larger set of scientific facilities that we have here so this is a really exciting set of missions that's going to take us through the next couple of decades at JPL and as soon as I finish delivering my son well six dual drives I get to work on mechanisms for rocks so I'm like trying to hurry up and deliver this another set of really awesome mechanisms is coming up for the Europa Lander development so Europa Lander is a really crazy amazing challenge there's huge thermal and radiation challenges with Europa it's really far away from the Sun so it's super cold there's no atmosphere and there's tons of radiation and for a potential landowner we have to design mechanisms that can deal with the fact that there's really small amounts of gravity barely any atmosphere to help use our speed when we try to land and approach Europa potential high magnetic fields also unknown terrain the closest up image that we have of the Europa and surface is like kilometers or something I think don't quote me on that but we don't have any kind of surface level details so landing on this surface is a really big challenge in and of itself so there's a whole landing mechanism team that's working on super cold temperature landing mechanisms for variable topography and chemical compositions big challenge and then the sampling system which I got to work on a little bit last year has a whole other set of challenges because you need to sample into any surface that's cryogenically frozen that could be sulfuric acid and it might be like giant sulfuric acid ice daggers and you're trying to sample into it while not changing its temperature so as to not disturb it so we have a lot of really cool mechatronic research and flight applications that are coming up so this is actually I just throw this in there because I had to this is a chamber that I helped get on lab for testing for Europa Lander sampling system last year right before we had a little shelving incident because of the budget so one day it'll see its day and have some awesome hardware and they're testing with it okay so that's me obviously so just the switch gears um I want to close by talking a little bit about how I actually got into mechatronics I haven't always been along the direct path to be an engineer and so I'm hoping that if anybody in here is not an engineer that they might be inspired to try so I actually grew up on a farm in a really small town we didn't have a physics teacher and I didn't know what an engineer was I never heard of it and I like building things because I grew up on a farm but I didn't really have the educational background or any kind of role models or anything to look up to and also after I graduated high school I actually got into fashion I spent several years after I graduated working as a fashion model which was really fun because I like shoes a lot and I like traveling and I like people like working in teams I like creative people which is why I like engineering a lot I just didn't know at the time so after several years of working as a model I finally kind of came to realize that I was a little bit intellectually under simulated and I was actually a nerd which I truly am and I decided to try to go back to college so that was really hard because I was like an adult at the time and I had no background I didn't even know how to go to college or whatever so I just did my best and basically my approach that I took was I'm just gonna do my best and I'm gonna build stuff and eventually I'll get there and so these were a couple of the first projects that got me a lot of momentum that allowed me to enter a world like JP oh that's my dog one of the first projects that told me that hey I could actually maybe be a good engineer was when I built a dog house for my dog I did woodworking and my dad had a sawmill and so that felt kind of natural and I just measured my dog and I like to sketched it out I want to you know make a house that looks like you know him with a crown he'll stand in the doorway and I envisioned this whole thing and I had a lot of fun out there like cutting up wood and making my thing and when I got to the roof I decided you know I'm living in New York it's so hot it's the summer it's humid I need to give him ventilation and so I started like kind of poking around on the internet and I wasn't used to Google because I was like pre Google era from high school but I was like just trying to see what's out there and I found a bay and I found that on eBay you can buy like lots of chipped solar cells and they have reduced efficiency but that's okay because actually there's an equation that can tell you the surface area that you need given a reduce efficiency of a solar cell and the power requirements of this little fan that I found that I wanted to use and said and so I'm like poking around and all of a sudden one day it dawned on me like what am i doing nobody's helping me and I'm having fun and this is like really awesome but I bet you if I got like an actual education I could probably build some cool stuff maybe I don't know right so I tried it and I enrolled in college I fought super hard I had to retake my SATs at the age of 27 to compete with all those super nerd eighteen-year-old kids which was awkward but I did it and I finally got accepted to transfer into an engineering school and once I got into engineering school then I was full steam ahead I ended up getting an internship opportunity at Princeton University doing physics which is cool but I wanted to build stuff so I convinced my physics professor that I was working for to let me build the mechatronics system that would partially automate his laser experiment and he let me do it yes it was awesome and that was basically me teaching myself how to build a mechatronics system to partially automated laser experiment I had just gotten the building blocks of computer science just enough to teach myself enough with MATLAB to do image processing to be able to identify laser and track it right it's just a community array and I just got enough CAD experience and design mechanisms and build the system that I needed to model in CAD and it was a great learning experience and the biggest thing that I learned from that experience is that I know that if I don't know something I can always learn it and I built a lot of confidence in that and so that system actually is what attracted the attention of JPL which led to them hiring me before my senior year in college which was unbelievable so now I get to build awesome stuff all the time that's me and a lot of buried in parts and I highly encourage anybody who's interested in mechanisms or curious or anything to teach yourself there's tons of resources out there and you'll blow yourself away with what you're capable of so anybody has any questions please I'll be happy to answer you [Applause]

7 Comments

  1. qwaqwa1960 said:

    The harmonic drive reminds me of the crazy piezo-sleeve screws drives used on auto-focus lenses…

    May 22, 2019
    Reply
  2. Cyber Cat said:

    Is the video framerate unstable/stuttery or is it just me that's noticing that?

    May 22, 2019
    Reply
  3. BrainLubeOnline.com said:

    Awesome.

    May 22, 2019
    Reply
  4. Peter Mortensen said:

    That was an amazing story!

    May 22, 2019
    Reply
  5. HerrHeisenheim said:

    Never heard of these harmonic drives, really interesting. I'm wondering if it's possible to make one "cheaply" for small projects using an SLA 3D printer and different grade of resins to provide the flexibility of the inner ring. Definitely gonna try, I was looking for a high-reduction and no-backlash drive for long-exposure night sky photography.

    May 22, 2019
    Reply
  6. klasop said:

    I'm in love. _

    May 22, 2019
    Reply
  7. carlos avila said:

    Michelle Easter ♥♥♥♥

    May 22, 2019
    Reply

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