"Editor's note" no function is rapid proliferation is to a large extent thanks to the open source development of the flight control, plaguing the critical equipment for autopilot of unmanned aerial vehicle development. So, what is open source flight control? And how to develop it? This paper by two professors in the unmanned aerial vehicle design Institute of Beihang University wrote in robots, Lei feng edited excerpts of which part, share them with flight control technology and open source story.
Drone aircraft flying over the complex products, the four-rotor aircraft with its simple structure, easy to use, low cost and other advantages, first came into the public eye. However, this type of aircraft for flight control requirements are the highest, it stimulated the emergence of a large number of open source flight control based on MEMS sensor.
How to define open source
Open source (Open Source) first applied the concept of open source software and open source Foundation (Open Source Initiative) use it to describe those software source code can be used by the public, and the use of this software, modification and distribution are not subject to license restrictions.
Each open source projects have their own forum, managed by a team or individual, the forum regularly releases open-source code, and interested programmers can download the code and modify it, and then upload their results, managers from a large number of changes improve the program, and once again select the appropriate code in the new version. And so to form a "joint development and shared" a virtuous circle.
The development of open source software combined with hardware, open source hardware. Hardware and software differences between the physical resources should be committed to creating real goods.
Therefore, the production of open source hardware (OSHW) license under the heading (product) of people and companies have an obligation to clear the product is not in the original approval before production, sales and licensing, and does not use any of the original trademarks. Hardware-specific format of the source code can be used by other persons, in order to modify it. In parallel with the implementation of free and open source hardware design of hardware knowledge sharing and encourage open communication and trade.
Open source hardware (OSHW) definition 1.0 is defined by the software based on the open source definition. The definition is by Bruce Perens as the Debian free software guidelines and Debian developers created.
Open source flight control is what?
Understand the concept of open source hardware, open source is easier to understand the concept of flight control. So-called open source flight control is based on automatic flight controls on the ideological basis for the open source project (Open Source Auto Pilot), containing both open source software and open source hardware and software control hardware is included in the firmware and the ground station software in two parts. Fans can not only participate in software research and development, can also participate in research and development of hardware, you can not only purchase hardware to develop software, also can make the hardware, which will allow more people to enjoy the results of project development.
Open source projects using commercial, so each open source control project will be given an official legal term to define developers and users ' rights, different flight control on the legal definition of open source is different.
Open source development of the flight control
Open source development of the flight control can be divided into three generations:
The first generation open source flight control system using Arduino or other similar open source electronics platform based, extended connection variety of MEMS sensors, unmanned aerial vehicle flew smoothly, and its main feature is a modular and scalable capacity.
Second generation open source flight control system with its own open source hardware, development environments and communities, using integrated hardware architecture, all 10DOF sensors, the master microcontroller, and even GPS devices such as fully integrated on a circuit board, to improve reliability.
It uses a three-axis digital MEMS sensor AHRS (IMU); can independently control aircraft en route, and can add the radio station to communicate with ground stations, initially with complete autopilot functions. This type of flight control can support wide variety of unmanned devices, including fixed-wing aircraft, rotary-wing aircraft, helicopters and vehicles, and have a variety of flight patterns, including flying manually, semi-autonomous flight and fully autonomous flight. Second generation flight control features high integration and high reliability, which is close to standard commercial autopilot.
Third-generation open source flight control system will be in software innovation and artificial intelligence. It joins the cluster fly, image recognition, autonomous obstacle avoidance, advanced flight capabilities such as automatic tracking flight, machine vision, clustering, development platform in the direction of the course.
You shouldn't miss the open source flight control legends
Arduino flight control
To talk about the open source development of the flight control from famous Arduino open source hardware projects to speak of.
Arduino is the first open source flight control, comprising Massimo Banzi, David Cuartielles, Tom Igoe, and Gianluca Martino, and David Mellis and Nicholas Zambetti in 2005 in Italy work interaction design Institute to develop together. Arduino company first developed for electronic enthusiasts to build a flexible open source hardware platforms and development environments, users can obtain from the Arduino website hardware design documentation, circuit boards and components to meet your design needs.
Arduino can the Arduino IDE and its supporting software to view the source code and upload your own code written, Arduino IDE uses the Arduino language is based on c and C++ language, is easy to grasp, and the Arduino IDE available in Windows, Macintosh OSX and Linux running on the three major operating systems.
As the platform is gradually being accepted by enthusiasts, features an endless stream of electronic expansion modules, MEMS sensor is one of the most complex is the integration of flight controllers. For better flight control design source, Arduino company decided to open its flight control source code, they opened the open source development of the flight control. Famous open source flight control WMC and APM are direct derivatives of the Arduino flight control, still using the Arduino development environment for development.
APM control
APM (ArduPilotMega) is a community in 2007 by DIY UAV (DIY Drones) introduction of fly control products, is now the most mature open source hardware projects. APM is based on the open source Arduino platform for multiple hardware improves, including accelerometers, gyroscopes and magnetometers combination inertial measurement unit (IMU). Because APM better customizability, APM's global spread quickly within the RC airplane enthusiast. Mission Planner through open source software, developers can configure APM settings, accept and display sensor data, use the Google map features such as automatic driving, but the Mission Planner only supports Windows operating system.
APM flight control has now become open source flight control maturity benchmarking to support rotary wing, fixed wing, helicopter and unmanned equipment such as unmanned vehicle. Multiple rotor, APM four, six or eight axis flight control supports a variety of products, and connect the external GPS sensor can be augmented later, and completed their own landing, autonomous flight, go home, fixed-height, location and other flight mode. APM can connect external Ultrasonic sensors and optical flow sensor, high in an indoor setting, and flyover.
The PX4 and PIXHawk
The PX4 is an open source hardware and software project (compliance with the BSD Protocol), intended for academics, hobby and industry groups to provide a low-cost, high-performance advanced autopilot.
This project stems from the Federal Polytechnic of Zurich University's computer vision geometry laboratory, automatic control of autonomous systems laboratory and the laboratory of PIXHawk project. PX4FMU autopilot module runs an efficient real-time operating system (RTOS), Nuttx provides a portable operating system interface (POSIX) type of environment. For example, printf (), pthreads, and/dev/ttyS1, and open (), write, and poll (), ioctl () and so on. Software you can use USB bootloader update.
PX4 MAVLink communications with ground stations, QGroundControl compatible ground stations and Mission Planner, all open source software with BSD agreement.
APM jointly by the 3DR group and the PX4 PIXHawk flight control was introduced in 2014, PX4 flight control upgrades, with the PX4 and APM two sets of firmware and the appropriate ground station software. The flight control is hardware specifications, the highest in the world, fly control products, but also amateur the hottest product in the hands. Vans cases
PIXHawk 168MHz operating frequency, and groundbreaking uses integrated hardware floating point arithmetic of core Cortex-M4 as the main control chip, built-in two sets of MEMS gyroscope and accelerometer sensors, complementary correction, built-in three-axis magnetic sensor and can add-a three-axis magnetic sensor and two GPS sensor can be prepared by one of the add-in, when a failure in the automatic switch.
Core based on its high speed operation and floating-point arithmetic, PIXHawk uses the most advanced algorithm for high, can only pressure altimeter aircraft height fixed at 1 metres or less. It supports almost all type of rotor, even including the three rotors and H4 irregular product structure. It has a variety of aircraft flight patterns to support autonomous route, key points around the mouse, guide, "FollowMe", on flights and other senior flight pattern, and are able to independently adjust parameter.
PIXHawk flight control open very well, hundreds of parameters were open to player adjustments, underlying pattern of simple fly after debugging. PIXHawk integrates a variety of map, fans can choose according to the situation on the ground.
OpenPilot and Taulabs
OpenPilot was launched in 2009 by the OpenPilot community of the autopilot project, aimed at providing the community with low cost but powerful stable of autopilot. The project consists of two components, including OpenPilot, autopilot and its support of the software. Among them, the autopilot firmware by c language, while the station is written in C++, and available in Windows, Macintosh OSX and Linux running on the three major operating systems.
OpenPilot is the biggest characteristic of the hardware architecture is very simple, since it now has many hardware designs will be able to see the difference. Official flight control hardware includes CC, CC3D, ATOM and the Revolution and the Revolution Nano etc, derived hardware includes a Sparky, Quanton, REVOMINI, etc, even directly using the STM32 development board extension of FlyingF3, FlyingF4, DescoveryF4, CC3D is 300mm wheelbase across machines and mini indoor RC airplane the preferred flight control, and DiscoveryF4 been studied extensively for lovers of flight control, Quanton has become the preferred hardware Taulabs. Vans case
Here we talk about Openpilot's most popular hardware CC3D.
This control board using only a 72MHz 32-bit STM32 MCU and MPU6000 will be able to complete the four-wing, fixed-wing and helicopter attitude control (note that the hardware is available three-freedom attitude control, rather than augmentation), PCB size of 35mmx35mm.
Different from all open source flight control, it does not require GPS integration or magnetic field sensor into the amendments, will be able to maintain attitude control for a long time. All the features above all use a firmware, can be changed by setting the aircraft type, flight mode, supports PTZ functions such as augmentation.
The compiled firmware required capacity of only about 100KB, code amazing efficiency, all flight control programmers learning model. Its ground station software is integrated with a complete map, or real-time status monitoring aircraft through the radio.
TauLabs flight control is the derivative of OpenPilot flight control. Current most popular hardware called Quanton TauLabs, the former OpenPilot flight control team members to complete.
It inherits the characteristics of OpenPilot is simple and efficient, and extend the barometric altimeter and tri-axial magnetic sensors, upgrading the master microcontroller to Cortex-M4 core with hardware floating point arithmetic. The flight control is the first open source flight control supports automatic scheduling products, with model identification algorithm in flight attitude PID control parameters self-tuning. TauLabs can complete many advanced flying mode, connect an external GPS can make the rotors have set higher, location, home and other functions. Flight control is integrated with the map, and the interface is very friendly, use initialize Wizard mode, can be simple to use for beginners.
Multi Wii Copter (MWC)
Multi Wii Copter (MWC) flight control is a typical Arduino-derived product, is designed for development of rotor low-cost flight control, it had to retain the integrity Arduino IDE development and Arduino upgrade and the methods used. Due to the low cost, simple structure, more mature firmware, so the flight control has a lot of fans at home and abroad. In addition to supporting common other than four, six or eight rotors, the flight control is characterized by many strange aircraft types are supported, three rotors, such as avatar vehicles (BIcopter avatar style), Y4-rotor (as opposed for two axis), make the development of the flight control interest is strong, easy to gain your love.
KKMulti Copter
KK flight control is derived from Korea flew an open source project, was also the first widely accepted by rotary-wing flight control, early on in the open source development of the flight control, the flight control turned to the entire four-rotor is a shock.
The flight control only uses three low-cost single-axis gyro, combined with a simple four-channel radio control device, you can control the common three, four or six rotary-wing aircraft, and supporting "cross"-type, x-type, h type and opposed a variety of layouts. The flight control with three adjustable resistance adjusting sensitivity as a method of scheduling, retained the characteristics of early models of a gyroscope. As rotary-wing flight control starting an important witness, this "antique" classic flight control level, still has a lot of players.
Paparazzi(PPZ)
Paparazzi (PPZ) is a hardware and software open source project, which began in 2003, development objective is to create a flexible and powerful open source control project. PPZ feature is that the open source flight control solutions in addition to common flight control hardware and flight software and ground software, also contain station hardware, including modems, antennas and other equipment. Functionally speaking, PPZ has been close to a small unmanned aircraft system.
Another feature of this open source project is using Ubuntu operating system, it will be under ground station software, and development environment integrated with the system, officially called a Live CD. A CD jiafei control hardware to complete all the work from development to use.
PPZ the hardware version is by far the most popular Paparazzi (PPZ) Lisa/M v2.0. The hardware has a lot of extension interface, and use a separate IMU sensors that can be extended. It is also very popular in the early open source flight control practices, so you can DIY your desktop computer, the IMU escalating hardware with the sensor upgrade.
Autoquad flight control and ESC32 electronic speed control
Autoquad flight control from Germany as an early open source flight control, Autoquad function is very powerful, but limited to the sensor, it is forced into a mass of MEMS sensors.
So-called analog sensors are sensors inside the chip does not have an integrated digital to analog converter (ADC) and the core operations, and micro-machined sensors directly changed by zooming in and hardware filtering in the form of voltage output, need to master AD single-chip data acquisition.
Because the sensor at different temperatures, the output value is affected, brought trouble to the calibration simulation of MEMS sensors. A lot of players when you use this control for the first time, have to use refrigerators to the sensor calibration, while some manufacturers in order to ensure the stability of bulk products, heating the circuit board only on the aircraft so that they maintain a constant temperature.
However, this calibration method for some hardcore brings extra fun, a lot of people happy. For most ordinary lovers, this is a problem in a lot of work. With the popularity of with factory-calibrated digital sensors, Autoquad, as the accumulation of history, has completed its mission.
However, another branch of the open source project ESC32 electronic speed control is gradual acceptance by the players. The ESC was the first electric with digital control interface, players can use serial ports, I2C interface and CAN interface to control the speed of the motor, this information faster than traditional PWM interface many times. Common PWM waveform update speed is 400 times per second, digital interface speed can reach millions of updates. Especially for multi-rotor aircraft dynamics are sensitive to changes in such communication is necessary. The ESC also supports speed closed loop, and detailed scheduling for the motor, which are traditional RC airplane electric adjustment can not be compared.
Of course, Autoquad is in progress, it released new flight control product Autoquad M4, the master microcontroller and sensor has been fully upgraded, using common STM32F4 and digital sensors. But the face of PIXHawk, APM has matured over the years advanced flight control products, has evolved from its predecessor become a rising star.
So, open source flight control to a large extent contributed to the four-rotor aircraft of such products into the homes of ordinary people, the development of drone technology, and can even help you to complete the dream of flying.
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