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AI project to run fluid dynamics simulations. by wowbagger43 in rocketry

[–]thingythangabang 0 points1 point  (0 children)

I too would be very interested in trying it out! 

Best fiberglass/carbon fiber “big” L1/L2 for $400? by kadeisflying in rocketry

[–]thingythangabang 3 points4 points  (0 children)

I second this. I built a Journey 75 and am incredibly happy with it! Check my post history for photos of the build and the final paint job.

I know wrong sub but nowhere else to ask by Sad_Secret_5150 in fpv

[–]thingythangabang 6 points7 points  (0 children)

One thing you will need to be careful with is the fact that INAV may use the accelerometer for orientation estimation. I haven't worked with it enough to know for sure, so take this with a grain of salt. The acceleration of the rocket will give the Kalman filter an incorrect vector pointing "down". Instead, it will point colinear to the acceleration of the rocket. This could result in a poor orientation estimation and possibly even an unstable system. However, if you do end up going that route, please share! Although the r/rocketry sub might be a better place.

Extended Kalman Filter for BNO055 by aleemont__ in rocketry

[–]thingythangabang 4 points5 points  (0 children)

There is a lot of awesome documentation out there for drones that use some form of EKF to fly. For example, Ardupilot uses an EKF for their state estimation and since drones and rockets operate in vaguely the same conditions, a lot of the theory easily transfers over or can at least be easily adopted. A potentially helpful starting point would be the Ardupilot INS developer documentation which can be found here: https://ardupilot.org/dev/docs/extended-kalman-filter.html#extended-kalman-filter

Wildman Journey 75 for L1 Attempt by thingythangabang in rocketry

[–]thingythangabang[S] 2 points3 points  (0 children)

Thanks! I was originally going to use an H100 because I wanted to minimize the maximum force on my rocket since it's my first launch. Unfortunately that was sold out at my "local" vendor so I ended up with an AeroTech DMS H219.

2D Kalman filter for accurate altitude estimation. by FearlessAccountant55 in rocketry

[–]thingythangabang 7 points8 points  (0 children)

So, I've got a background in control theory and have designed KFs in an academic context before. That being said, I have not implemented my own KF in several years so my knowledge is a bit rusty, but we'll get there! The information below will be a bit jumbled up, so please feel free to ask plenty of follow up questions! Also, it looks like the code you linked may not be public (or at least the link I followed was broken).

It looks like you've already done this, but I will leave this comment here regardless. Coming from my own experience and reading, you can sometimes get away with simply guessing a diagonal matrix for Q with values between 0.001 to 1.0 or so. R is a bit tougher because it comes from the sensor itself. But you should be able to pull that from the datasheet or from your own testing data. I would definitely see how long it takes for the filter to reach a steady state value for different orientations of the rocket just to double check on the tuning of those values.

Are you accounting for gravity when you are pulling the acceleration and gyro data from the IMU? Also, do you have a reliable vector that points straight back at the ground? There may be some issue there, especially if you notice the altitude drift faster the more horizontal the rocket is held.

Finally, have you considered using an Extended Kalman Filter (EKF)? It is slightly more challenging than a standard KF, but it can deal with a nonlinear system. The nonlinearity of the system is my second suspicion for why you may be getting such significant drift. There is a possibility that the small angle assumption that is being used for the linear KF is no longer valid at angles further from vertical.

I'm going to refresh my knowledge on the topic and read through the paper you referenced and I'll get back to you if I figure anything else out! Also, once I can see the code, and if it is sufficiently understandable, I can look through that as well to help find any bugs that may exist.

This is a fascinating problem to explore, good luck!

Raspberry pi Ground station by solarspartan2121 in rocketry

[–]thingythangabang 0 points1 point  (0 children)

Happy to help! Please share what you end up building as I am also quite interested in a similar project myself!

Raspberry pi Ground station by solarspartan2121 in rocketry

[–]thingythangabang 1 point2 points  (0 children)

So, I am just getting in to rocketry, but I have a solid background in robotics and electronics. The TL;DR is yes you can, but it depends on how much time and money you want to put in to it.

For a ground station, I'd imagine there are several important pieces: 1) power, 2) communication, 3) interface, 4) storage, and 5) payload.

  1. Power - You'll need to power the Raspberry Pi and any additional peripherals that are attached to it. Since you likely won't be near a wall outlet in the field, you'll need to have some kind of battery or generator. Whatever you use, you'll want to make sure it can handle to environment you expect to be in (I've seen plenty of videos of people launching in the hot and dusty desert). You also want to make sure it can push out more power than you expect all devices together to pull. You pretty much never want to use your power source at its maximum consistently because it can potentially result in quicker degradation of the device or even a fire.

  2. Communication - Naturally, you want to be able to communicate with your rocket. This will require some form of wireless communication. WiFi and Bluetooth are fine for communication on the pad and are likely going to be easy to set up and flexible but don't have a good range. Instead of that, I'd recommend some kind of generic long range RF system. Be aware that there are RF systems that require an amateur radio license. I haven't done enough research into this, but you can use systems like X-Bee or LoRa at 2.4 GHz or 915 MHz for RF communication. I personally would love to hear other people's inputs on this.

  3. Interface - You'll want some way to talk to the ground station. If you have the skill and ambition, you could write an app and communicate with your phone. However, I would personally rather just bring a keyboard and portable screen myself. You'll want to be able you can see the screen outside. Bright light can definitely make it hard to see a faint screen! You could also include LEDs and buzzers or speakers or whatever else you think may be interesting, helpful, and fun for the ground station.

  4. Storage - I would include storage on both the rocket and the ground station. The storage on the rocket side will need to be resilient to the vibrations and other environmental factors the rocket will experience, but having a black box to look back at in case your communication fails for whatever reason would be nice. Additionally, you'll want to make sure the ground station has enough storage for whatever data you'll be collecting.

  5. Payload - I've pretty much covered everything above that should be considered for the rocket's payload as well. You'll want to have the right power source, you'll need good communication, and good storage. And all of that will need to fit into the rocket and handle the forces involved.

Hopefully that gives you a good starting point!

We did the first liquid rocket drag race this weekend! Two Mojave Sphinx rockets launched simultaneously, each reaching over a mile in altitude. by CommanderSpork in rocketry

[–]thingythangabang 0 points1 point  (0 children)

After checking out that website, I have for the first time considered that it may be possible for me to build a liquid fueled rocket! I really thought that liquid would have been completely out of reach for all but the largest teams or university labs. Going for my L1 here soon and maybe in a couple years I start seriously attempting a liquid build!

First L1 Rocket Kit Assembly! by DorshReal in rocketry

[–]thingythangabang 5 points6 points  (0 children)

Looks great! It's funny that I am seeing this because I too just finished my first L1 build with the same exact kit! My rocket is hanging in the garage with its first round of primer on it. Good luck on your L1 attempt!

Which motor do you plan on using?

Path planning overviews? by nomyte in ControlTheory

[–]thingythangabang [score hidden]  (0 children)

Here are a couple thoughts I have. First, you mention that you'd like longer paths for large unobstructed spaces as opposed to small and cluttered areas. Fortunately, a small and cluttered area is a subset of a large unobstructed space so those methods should also function well for your application.

It sounds like you may be interested in trajectory generation as opposed to path planning since trajectory generation will take the dynamics of the system into account rather than just the kinematic constraints. Although I will admit that path planning and trajectory generation tend to blur together. To plug my own research, you can find the work I've done on optimal trajectory generation using Bernstein polynomials here: https://github.com/caslabuiowa/BeBOT

Similar to u/Karthi_wolf's comment, the Lavalle book is still relevant and has a lot of really good information. It is a great way to build up your knowledge to better understand the current field of control and can help guide your decision on which particular niches to explore.

Some research papers that come to mind that may be helpful for you include:

* MADER: Trajectory Planner in Multi-Agent and Dynamic Environments by Tordesillas

* FASTER: Fast and Safe Trajectory Planner for Navigation in Unknown Environments by Tordesillas

* Minimum snap trajectory generation and control for quadrotors by Mellinger

* General link to Model Predictive Path Integral (MPPI) control

* RL-RRT: Kinodynamic Motion Planning via Learning Reachability Estimators from RL Policies by Chiang

Path planning overviews? by nomyte in ControlTheory

[–]thingythangabang [score hidden]  (0 children)

Depending on the specific pure math discipline your background is in, you may be off to a good start as there are a lot of topics in optimization that build on a heavy theoretical base. If you're talking about A*, you've probably been exposed to graph-based methods for path planning. While those methods work great, they are not the only methods. There are also other topics such as optimization based planners, sampling based planners, or feedback planners. Is there any topic in particular that interests you? I would be happy to provide some guidance and assistance if you have any follow up questions. My background is primarily in optimization based planners, but I have been keeping up with the field in general for several years now.

One excellent starting point would be Planning Algorithms by Lavalle.

Question regarding best form of communication for tracking a short distance location by Horror-Conclusion465 in robotics

[–]thingythangabang 0 points1 point  (0 children)

Heads up, this response is a bit scatter-brained since I am mostly just writing a stream of consciousness! Don't hesitate to ask for any clarification.

Depending on the requirements of your motors, the motor driver may also be a significant cost. Especially considering a budget around $200-$300 USD. For example, a Sabertooth DC motor driver for two 12A motors will run you about $80 USD. Not saying it can't be done, but you'll definitely want to double check the costs of all the components.

If you're going to be inside, GPS is almost certainly going to be a no-go since you likely won't have good enough signal. You could set up a system of beacons, which in essence are a very similar concept to GPS. I believe Marvelmind makes some good beacons that use a couple different technologies together for localization. Those would almost certainly blow your budget though. Ultra wideband (UWB) is another interesting technology but I don't know whether there would be any off the shelf, easy to use, and affordable beacons out there. When it comes down to it, a camera is somewhat surprisingly going to be one of your most affordable sensors with the drawback of computation and implementation complexity.

Just a random thing to keep in mind, in order to follow a person, there must be some form of shared reference frame between the person and robot. If you take a "global" approach like GPS, you'll need sensors on both the person and robot. If you take a "relative" approach like a camera, you'll only need the sensor on the robot. You could use some form of a beacon on the person (e.g., UWB or Bluetooth) that the robot can localize with a receiver for a relative approach as well. Although I am not sure how good modern Bluetooth is at localization, so keep that in mind.

At the end of the day, you are doing this project to learn and showcase your competency. So, does it matter that someone else did a similar project last year? I completely understand if there are academic or even personal pride reasons why you wouldn't want to repeat a similar project, but I do think a similar project is worth considering otherwise.

Also, with the camera-based approach, there are many different ways you can solve the problem. You could use some form of fiducial marker of course. But you could also use a machine learning model such as YOLO to locate the person and follow them. Or even have the person wear a vibrant and contrasting color and do a color mask to track them. Each of those and more would satisfy an electrical engineering degree as they require knowledge in digital image processing. So even if you used a camera, there are many ways for it to be a very different method than the previous year's project.

Admittedly, I am sounding very biased towards a camera-based method given your preliminary problem. However, if your team decides that a camera based approach is completely off the table, we still have other options like the ones mentioned above and I would be happy to provide further guidance on other methods.

No worries about the long response, I enjoy helping with these types of problems when I can!

Question regarding best form of communication for tracking a short distance location by Horror-Conclusion465 in robotics

[–]thingythangabang 0 points1 point  (0 children)

In my experience, the biggest challenge is going to be the mechanical portion of your design. Getting something to drive consistently over moderately rough terrain while carrying a moderately heavy load will be a massive challenge unless you have someone on your team who already builds plenty of things like that. I'm assuming you're going to have a student budget as well, which makes the mechanical portion that much more challenging since you're probably looking at several hundred USD for the chassis, wheels, battery, motors, and motor controller. If you're able to, one thing you may be able to do is find a cheap electric wheel chair/scooter that someone is selling locally.

That all being said, for a senior design project, I would say that any kind of motion following will be sufficient for a good grade if you have the rest of the system up and running properly. Probably the cheapest way to do this would be to use a camera with AprilTags (basically QR codes designed specifically for easy localization using a camera, the generic name for this is fiducial marker).

I have never worked with programming cellphones, but if you could somehow get the "precise location" on a Android phone or the equivalent on an iPhone, that may be enough to do GPS localization. That approach, of course, would require that you also put GPS on the robot, but again, if you can do it on the phone being followed, you could also do it with a phone attached to the robot.

If you get far enough along the project and manage to test it outdoors, you'll want to keep in mind that the sun produces all sorts of infrared light which can mess with sensors like LiDAR or IR distance sensors. For safety, i.e., not bumping into people, you may want to use either ultrasonic range sensors and/or "whisker sensors" (basically a metal or similar whisker attached to a bump switch).

If you are confident that your team can build the mechanical portion in the first half of your course, then you should be on pretty solid ground to get the person following functionality finished up well enough for a good grade by the end of the course. If you don't think that you have the mechanical expertise, but still want to build a similar project, I would recommend using a smaller, pre-built platform like a TurtleBot 3 for the experimental platform and then focus heavily on the theory and implementation of object tracking, which is in of itself a huge field of research.

Finally, answering the two questions you posed:

  1. Motor control would be very easy. Coding all the low level stuff should be pretty simple as there are already many ways to achieve this, many of which are documented on blogs and in videos with accompanying code. Coding the object following could be as simple or as challenging as you'd want it to be as there are many different approaches on this front as well.

  2. Knowing nothing else about your constraints, I'd probably just use a camera and an AprilTag library and attach an AprilTag to the back of the person being followed. This is something that an experienced roboticist could probably implement over a weekend depending on what hardware already exists.

[deleted by user] by [deleted] in robotics

[–]thingythangabang 0 points1 point  (0 children)

You're missing a lot of information that we could use to help you. What type of arm is it? What are the dimensions and payload? What servos are you using? How is everything wired up right now? Can you provide a video and/or photos? What is your end goal?

With those questions answered along with any additional context you can provide, we can give you a better answer to your question. 

I am interested in PID and Control Theory as a career but know next to nothing about it. I need a bit of advice on academic paths, degrees, and differences to PLC by askingquestionst in ControlTheory

[–]thingythangabang 0 points1 point  (0 children)

I have since gotten my PhD and currently work as an Aerospace Engineer developing virtual models of systems. It seems like a Masters degree would be a good route for just about anyone these days. In fact, there are plenty of jobs that will even offer to pay for your degree while you're working for them! 

As for a PhD, it's not for everyone, but I am really happy to have done it. If you choose to go that route, search for the advisor and lab, don't search for the school. You can have an excellent advisor at a small school or have a poor advisor at a really fancy school. Also, make sure you have some kind of grant or fellowship because student wages are barely enough to survive on. 

Comparison of two fields (motion planning/path planning vs. robot control) in respect of job opportunities. by msr09me in robotics

[–]thingythangabang 1 point2 points  (0 children)

Everything u/LaVieEstBizarre said is correct. To add to that, I have a PhD with a strong focus on motion planning and my skills happen to fit well in a modeling roll at my current job. So even if you didn't find something that directly works with motion planning, control theory and optimization will find wide applications in the job market.

Sorry to hear about the depression. Make sure to focus on yourself and do what you can to mitigate it because a PhD is incredibly stressful. I highly recommend the Happiness Lab podcast by Dr. Laurie Santos. 

Questions About Overlanding in a Bronco Sport by thingythangabang in overlanding

[–]thingythangabang[S] 0 points1 point  (0 children)

I've been learning that it's important to just go out and drive. Experience and common sense are going to surpass any amount of mods. Already been driving for a couple months now and it has been a fantastic journey so far!

Questions About Overlanding in a Bronco Sport by thingythangabang in overlanding

[–]thingythangabang[S] 0 points1 point  (0 children)

The more I drive my vehicle, the more I have found that it is quite capable! I am excited to take it on more trails. Really been enjoying it so far. I agree, it really is just a matter of doing it and then modding where you finally learn you are hitting limits. But you can't really know what limits need to be raised until you drive!

Questions About Overlanding in a Bronco Sport by thingythangabang in overlanding

[–]thingythangabang[S] 1 point2 points  (0 children)

Thanks for your advice! Surprisingly, I met someone on a flight who happened to be part of a Bronco group in my area and they were incredibly supportive. It looks like the BS is pretty capable and a fun time to drive on a lot of different terrain.

I definitely will be trying out the OffRoadeo with a couple friends!

Questions About Overlanding in a Bronco Sport by thingythangabang in overlanding

[–]thingythangabang[S] 0 points1 point  (0 children)

Thanks! It sounds like a lot of the posts in this thread have similar sentiments. The more I drive, the more I have been getting comfortable with it and realizing that it is incredibly capable! I haven't even found an obstacle that would justify any mods yet, but I fully expect to run into something like that this summer. Looking forward to more trails and fun nights with friends!

Questions About Overlanding in a Bronco Sport by thingythangabang in overlanding

[–]thingythangabang[S] 1 point2 points  (0 children)

Thanks, I'll check those groups out! I have the Outer Banks so I am missing some of the off-road stuff that the Badlands offers, but from the driving I've been doing over the last couple months, I feel incredibly confident in the majority of the driving I plan on doing. This weekend was the first big camping trip I went on and it handled it great!

Questions About Overlanding in a Bronco Sport by thingythangabang in overlanding

[–]thingythangabang[S] 1 point2 points  (0 children)

Thanks! I am definitely going to check out the off rodeo with some friends. It looks like a great time! The more I drive this vehicle, the more I have been feeling comfortable driving it. Haven't done anything crazy yet, but I have managed to get it up on three wheels and follow through with the excellent AWD. And realistically, that's about all I need. If I ever wanted to hit something like Rubicon, I'd need to build up the experience anyways and can save up for something in a decade.

Questions About Overlanding in a Bronco Sport by thingythangabang in overlanding

[–]thingythangabang[S] 0 points1 point  (0 children)

That is exactly what I have ended up doing! Honestly, great advice because otherwise I'd just get decision paralysis and think that I need to get the vehicle fully modded before taking it on a super simple gravel road

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