UAV Flight Computer (RC, Drones, Airplanes)  - Page 1
Forum section: electronics / projects

author: Zarko
author_rank: Newbie
timestamp: December 29, 2016, 09:38:21 pm
content: Is there anyone designing flight computer for controlling UAV's, quadcopters, drones, airplanes?

author: raptor1956
author_rank: Frequent Contributor
timestamp: December 29, 2016, 11:36:53 pm
content: As best I can tell, outside of military projects the major innovators for UAV control are the Chinese. And, at the tp of the heap is DJI. Using redundant IMU's and high precision electronic compasses and gyros DJI is well ahead of the pack in drone tech. They have been busy the last couple years incorporating collision avoidance technology using stereo cameras and sonar and my guess is within a couple years we'll begin to see radar as well. You can buy the primary components that make up the flight control system from them including the up/down link with telemetry. This is a field where the Chinese have been the leaders since pretty much day one so it's not like they came along and undercut the west. My guess is that the Chinese will own 90% of the consumer and commercial drone market though the military market is a different story.Brian

author: hendorog
author_rank: Super Contributor
timestamp: December 29, 2016, 11:48:48 pm
content: This would be a good place to start:https://github.com/ArduPilot/ardupilotWith some effort something similar to a DJI could be put together yourself. Although achieving the level of 'slickness' they have reached would be very difficult - and it would no doubt cost more.

author: Zarko
author_rank: Newbie
timestamp: December 30, 2016, 10:51:25 am
content: For my master thesis I design this type of flight computer, similar to all others on the market but with one very important thing in mind, safety critical.I have very first prototype of HW and SW and get something working. Because the main point is safety critical system, probably my design should be similar to military designs but I cannot find much info on military designs to base my project. If someone have experience or some useful info, please share it.Brain in the system is RM48L952 combined with MPU9150 sensors, Code Composer Studio as IDE and C programming language.

author: rcairman
author_rank: Newbie
timestamp: December 30, 2016, 11:36:06 am
content: Zarko,Among a few unfinished attempts, I have designed 2 flight controllers that actually flew. The first one was simple in hardware (STM32F4 + MPU6050) and was used to work on the software, the second one was an overkill in terms of hardware (full isolation of power and communications, modular design, triple redundancy of sensors, high-quality sensors, CAN bus, wide input voltage range, etc). It was designed mainly for high reliability, immunity to strong electric and magnetic fields, modularity and accuracy. It was a modular design, meaning that there was a separate unit for INS, separate unit for GPS, magnetometer and barometer, separate unit for main flight controller and yet another unit for power management and motor/servo outputs. The idea was that parts of this system could be used independently, for example IMU/INS. I also did EMC testing and the whole system outperformed expectations (mostly thanks to metal shielding and isolation).The key to flight controller is software. Currently available hardware (sensors) are good enough. Even the cheapest gyros and accelerometers should get you flying if you have good software. With bad software, even the best sensors will be of no use.These days my approach to reliable flight controller would have been very different: there is a great amount of software work done in Ardupilot project. Ardupilot runs on Pixhawk platform which is good for basic flying but lacks in EMC, accuracy and reliability. One of the projects on my "to do" list is to make a very good hardware (based on what I did before) that will be compatible with Ardupilot code (minor modifications in low-level code required).As far as military systems go, there are some special MIL standards to follow. I tried looking into it, but the documents were either hard to find or hard to get through and I eventually decided to focus on engineering rather than fulfilling requirements, that may not be reasonable for this particular system.Things to consider when designing safe flight controller:- what happens if one of the modules (if modular) or components (if not modular) fails: does it bring down other parts of the system (for example by short circuiting power lines)- how to manage redundacy: there always has to be a joining point where redundant systems meet and information from one of them is delivered to servo/motor- how to manage EMC: shielding, isolation- how to manage vibrations (very important for every flight controller!)- how to manage temperature drifts and temperature compensation- how to communicate different modules- flight controller is as safe as it is aware: what happens if you loose GPS signal (jamming)?I did a lot of thinking on these topics and I believe I have an answer to every question, but I don't want to suggest anything just yet - my solution may not be perfect and you may come up with much better ideas.Moreover, if you plan to use this flight controller in more complex systems (for example drone with extra navigation features, cameras, advanced flight patterns), you need to decide which functions should be done by flight controller itself and which should be done somewhere else. I decided to keep flight controller as simple as possible and move all advanced stuff to onboard computer. If this computer fails, flight controller can still perform basic navigation and return home/land safely.

author: Zarko
author_rank: Newbie
timestamp: December 30, 2016, 01:28:56 pm
content: Thanks for the replay Jakub, I'm sure that I'm not alone in this type of design, but all available flight controllers on the market today are very far from safety critical system.We have similar points in our designs, and almost anyone have modular design at the beginning of the project (me also).I chose RM48 Herculles series microcontroller from TI because they are designed for safety critical applications implementing ARM Cortex R4 dual core in lockstep architecture. About the HW, for now I have 2 modules designed, total of 4 modules was the plan.First module is the flight controller with power supply and storage (uSD).Second module is the IO Board which contain input from RC receiver and output for motors and servos. Here all signals are isolated and power supply's for the outputs are switchable with current limit. Here is also Interface for sensors using I2C bus which is also isolated.Third module is planned to be Analog board which will make acquisition on all analog signals (voltages, currents, temperatures, etc) and pass to ADC inputs of the MCU. Analog board will be used mainly for monitoringFourth module is planned to be general purpose digital module for various stuff like OSD, gimbal controller, ...First prototypes are mainly for software development and testing. First flight on quadcopter was this month. PCB designs are for hand made PCB's, now I'm starting to design second prototype which I'm planing to do on 6 layer board in order to handle EMC and EMI more efficient.On software side, code is OS free and writed with a lot of defense mechanisms with handling multiple failures. This implementation is very time consuming and there is a lot of stuff to do. Some of software components are based on ardupilot, some on cleanflight but most of the implementation is mine. I know that SW is very important and more complicated part to design but HW is important also.I'll post the schematic soon

author: rcairman
author_rank: Newbie
timestamp: December 30, 2016, 01:46:27 pm
content: Don't force your way into 6 layer PCB if you don't need it, 4 layer PCB will be more than enough if you use external shielding. In my case I used 2 layer PCB, next version was planned with 4 layers but even 2 layer PCB survived +-8kV of EFT-B bursts (requirement was 2kV, the lab gave up at 8kV because lab equipment in the room started failing).PS. My motivation for EMC was the kind of job I did with drones: inspection of active 400kV power linesGood luck with your project, sounds nice!

author: getfast_kiran
author_rank: Regular Contributor
timestamp: March 16, 2017, 10:11:36 am
content: Hi,Could you please point me to any document that will help me design taking care about the EMC and EMI aspect.

author: rcairman
author_rank: Newbie
timestamp: March 29, 2017, 11:09:18 am
content: Hi,unfortunately I don't have a specific document on good EMC design practice. I followed my best knowledge and "a hunch". It is also good to look through other designs to get some ideas. If you use shielding you have to be careful with traces that go in and out. Take a close look at your ground planes to make sure you minimized current paths and that main current paths are well engineered (more than one via for starters)You can look at this:http://www.ti.com/lit/an/szza009/szza009.pdfalthough I have only briefly looked through it.

author: Jacon
author_rank: Regular Contributor
timestamp: March 29, 2017, 06:05:03 pm
content: How about this, Zarko :https://emlid.com/navio/They are working hard on it, according to steady email news stream...