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154 lines
6.8 KiB
Markdown
154 lines
6.8 KiB
Markdown
SOFTWARE ENGINEERING DEPARTMENT
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SITUATION REPORT 3
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Implementing a Parachute Launching System using Pixhawk
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Luís Jesus
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October, 2022
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Summary
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=======
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With this report, I want to introduce a way to implement our Parachute
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Recovery System that will guarantee that the rocket lands on the ground
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successfully. This implementation was suggested by Professor Anuj Regmi
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(SYSTEC). Even though there are not rocketry implementations of its
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suggestion (besides BPS.space) in which we can rely on, it is relevant
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to search how it could be done and some of its constraints.
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As concluded in the previous meeting, designing our own board computer
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"from scratch\" is actually very risky and may lead to difficult
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challenges that we may not be able to solve "in-time\", which means that
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we must choose a more reliable path, at least for now. The suggestion
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was to use a Pixhawk Autopilot Board - Pixhawk \[[full specifications'
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sheet
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here](https://docs.px4.io/main/en/flight_controller/pixhawk4.html)\] -
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and ArduPilot as the controller/receiver of this board (it is tipically
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the software used along with Pixhawk).
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If we move on to this solution, that means that a great part of the plan
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made by the Electrical Engineering Department will have to be discarded,
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as Pixhawk4 has in-built sensors and they won't have to face the
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expected assembly and testing procedure that was initially designed.
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Introduction
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============
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Ardupilot is a open source autopilot system that supports many vehicle
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types, such as multi-copters, traditional helicopters, fixed wing
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aircraft, etc. However, there is not much information about its
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implementation in rockets, and the only example we have is
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[BPS.SPACE](https://bps.space/), from which we don't have many
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information.
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Considering this, we know that this implementation would need some
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adjustments to fit in the rocketry field.
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Mission Planner is part of ArduPilot and it has the interface that
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allows us to follow the vehicle during its flight. However, if we look
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to the picture bellow, we can also see that there is not compatibility
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with a rocket-type vehicle. A amateur SpaceX inspired rocket ([see
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here](https://hackaday.io/project/174329-spacex-inspired-edf-rocket))
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actually implemented Pixhawk running with ArduPilot V4.0.4 configured as
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a single-copter, however, the mentioned project is very different. It's
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not a real rocket; it \"flies\" like a drone, it does not reach high
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altitude, it is remote controlled, etc. The analysis about the
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requirements to make a Pixhawk based board fit a rocket model is in
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charge of our team member João Gil, though.
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Considering this, there is not information about parachute deployment
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using Pixhawk + Ardupilot on rocketry, but we can see a more \"typical\"
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case (for example, how it is used in drones).
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Parachute Deployment System
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===========================
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As a baseline requirement to implement this, we have, of course, a
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complete parachute mechanism like [SkyCat](https://www.skycat.pro/shop/)
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or [CAD Drones](http://store.caddrones.com/products) but adapted, in
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this case, to fit our own vehicle that is way larger than the vehicles
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Ardupilot is meant for. This study is certainly under the analysis of
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another department, as it is not related to software.
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The release of the parachute is actually a mechanical \"phenomenon\" and
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that made the interpretation of the documentation a little bit hard.
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Maybe we need the help of a member of the Electrical and Mechanical
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Departments to help us understanding what is actually happening during
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the deployment of the parachute.
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The parachute release mechanism can be triggered from either a Relay or
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a PWM (Pulse-width modulation) signal. If a Relay pin is used, the
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parachute release has to be activated on a high level and RELAY\_DEFAULT
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has to be OFF or No Change, in order to avoid triggering the release
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during initialization. For more information about this and other
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parameters, see [Complete Parameter
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List](https://ardupilot.org/plane/docs/parameters.html#relay-default)
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(we need the help of other departments to better understand them).
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We may want the parachute to deploy automatically or manually, but in
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our case, it's just going to be automatic because the Ground Station is
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not sending any kind of signals/data/information to the rocket, it will
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only work as a receiver.
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In the [official documentation of
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ArduPilot](https://ardupilot.org/copter/docs/common-parachute.html), it
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is referred that the configuration is made via Mission Planner and we
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have a bunch of parameters to deal with according to our needs and
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specificities. There is some information about the PINs configuration,
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however, I did not understand how our rocket is in terms of mechanical
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components in order to make a detailed report about the implementation
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of this functionality. Considering this noticeable trouble on
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understanding other technical information in the documentation, we may
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need to establish a very close relationship with other departments
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because there are many subjects crossing our theoretical implementation.
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This terms and configurations are important to discuss with other
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departments:
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Apart from this, there is a project called
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[ArduRocket](https://diydrones.com/forum/topics/ardurocket?xg_source=activity)
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that seems to be a modified version of ArduPilot but it is quite old
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(check [GitHub repository](https://github.com/stew-lilley/ArduRocket)).
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Veredict
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========
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There is basically no information about Pixhawk + Ardupilot usage in
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rocketry, but only about their typical implementations in other
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vehicles. This means that there is a need to study the best way to make
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this type of implementation compatible.
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For this, it seems that the help and monitoring of other departments
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(Electrical and/or Mechanical ?) is crucial to understand the viability
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of the implementation. Invictus is being designed to reach an apogee of
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3000 meters and it uses hybrid-propulsion; it seems quite complex when
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compared to those simple vehicles supported by ArduPilot which means
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that there is a big analysis of viability to be made by a competent
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department before any kind of analysis of implementation.
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Apart from this, if the transposition of this technology to our rocket
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is achievable and viable, there is the official documentation mentioned
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in this report about the setup of the parachute deployment system, that
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has to be analyzed carefully not only by our department, but
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fundamentally with the help of the Mechanical Engineering Department and
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Electrical Engineering Department.
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References
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==========
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\[1\] [ArduPilot](https://ardupilot.org/);
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\[2\] [ArduRocket (DIY DRONES
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Forum](https://diydrones.com/forum/topics/ardurocket?xg_source=activity);
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\[3\] [ArduRocket GitHub
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repository](https://github.com/stew-lilley/ArduRocket);
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\[4\]
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[Hackaday](https://hackaday.io/project/174329-spacex-inspired-edf-rocket).
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