Quadcopter are hitting news a lot these days is almost all application areas. Plus quadcopters are hot interest for hobbyists. A quadcopter is idealistically consists of four propellers connected with rotors and controller centrally. Flight control of a quadcopter is most important part in designing a quadcopter. In this article we have shown some latest innovations in flight controllers of miniature and customized quadcopter driving hottest trends…
Looking back 2 decade ago, designing a drone or UAV seems to be solely done by ISRO or aerodynamics experts. The components and tech asked by a drone is complicated enough to keep make the concepts fantasy. But today robotic kits are available in market to design and control your own drone. Equipped it with camera and you will get a personalized drone ready. A quadcopter is consists of a very simple framework and the major line of components are:
- Propellers or the blades in a very simple language. Normally drones are designed with 3 or 4 propellers, that tri-copters or quad-copters. Hex-copters are also available today. This article will focus flight control of quad-copters.
- Multi-rotors or motor connected with the propellers that control the total mechanics and balance of the quadcopter.
- Flight – controller or brain of the drone that controls speed and direction plus communicates with the pilot. This article will bring our more technologies and models in the module.
- Software to program, monitor and control the quadcopter. The software design is usually programmed or supplied with fight controller kit.
- Battery to supply power. Power is supplied by a high capacity lightweight battery. Li-Po batteries are best suited for this purpose. They can deliver high amount of current at short time which is required by the motors for the lift and have very small footprint.
With increasing intricacy it became difficult and distracting to control the rotational speeds and directions of three or more motors simultaneously with enough precision to balance a craft in the air. This is where flight controllers come into play. A flight controller (FC) is a small circuit board of varying complexity. Its function is to direct the RPM of each motor in response to input. A command from the pilot for the multi-rotor to move forward is fed into the flight controller, which determines how to manipulate the motors accordingly. The majority of flight controllers also employ sensors to supplement their calculations. These range from simple gyroscopes for orientation to barometers for automatically holding altitudes. GPS can also be used for auto-pilot or fail-safe purposes. With a proper flight controller setup, a pilot’s control inputs should correspond exactly to the behavior of the craft. Flight controllers are configurable and programmable, allowing for adjustments based on varying multi-rotor configurations. Gains or PIDs are used to tune the controller, yielding snappy, locked-in response. Many flight controllers allow for different flight modes, selectable using a transmitter switch. An example of a three-position setup might be a GPS lock mode, a self-leveling mode, and a manual mode. Different settings can be applied to each profile, achieving varying flight characteristics. While many flight controllers have similar hardware or sensors, they have very different software and calculation algorithms, which results in different flight characteristics, and user interface. That’s why the same quadcopter flies and feels differently with different flight controller installed.
One of the important concern is keeping small footprint and microprocessor based FC serve the purpose best way. Ideally a microcontroller with at least 4 digital IO/PWM to signal the motors via the electronic speed controllers (ESCs) should be considered while designing a quadcopter. The microcontroller should also have an interface like Inter-Integrated Circuit (I2 C) to connect to the IMU device so that the numbers of ports necessary to attach multiple sensor devices are reduced. Plus accelerometer is required to sense the orientation, position and velocity without the need for external reference. With an accelerometer alone, either a really “noisy” data output that is responsive, or a “clean” output that is sluggish is obtained.
Future small UAVs will require enhanced capabilities like seeing and avoiding obstacles, tolerating unpredicted flight conditions, interfacing with payload sensors, tracking moving targets, and cooperating with other manned and unmanned systems. Cross-platform commonality to simplify system integration and training of personnel is also desired. A small guidance, navigation, and control system has been developed and tested. It employs Field Programmable Gate Array (FPGA) and Digital Signal Processor (DSP) technology to satisfy the requirements for more advanced vehicle behavior in a small package. Having these two processors in the system enables custom vehicle interfacing and fast sequential processing of high-level control algorithms.
Architectural Advancements
While designing a quadcopter, the system is required to be designed for minimum size and weight necessarily to simplify structural requirements plus catering applications like surveillance or GPS etc. A system designed to meet the performance requirements of a larger platform should meet the size, weight, and power demands of smaller vehicles. The goal of this hardware design was to optimize the performance to size ratio for a widely applicable flight control system (good for a large class of vehicle size, including small), a system enabled by Micro Electro Mechanical Systems (MEMS) sensor and embedded processing technologies.
The Flight controller board for such architecture requires a microprocessor, a large FPGA, memory and interface headers on a single board. Additional processor boards or application-specific boards are added to the stack for increased performance. High-speed differential ports in the FPGA enable dedicated communication channels to other processor boards. The FPGA on the board performs low-level and parallel interface functions for external components. A fast, parallel data bus enables communication between the FPGA and the DSP, minimizing the amount of interruption to the DSP. Sensor data is preprocessed in the FPGA, bundled and transferred to the DSP through a set of First-In First-Out (FIFO) queues in the FPGA. Actuator commands are sent from the DSP to the appropriate servo driver component in the FPGA. The delegation of low-level interface tasks to components in the FPGA increases the overall efficiency of the system, allowing the DSP to dedicate its resources to high-level tasks and signal processing. Flight controller needs a set of sensors to control the system. A typical sensor board contains angular rate sensor (gyroscope) and accelerometers complete the inertial measurement unit set. The board contains few more voltage regulators and level converters for the input/output pins used to interface with servos/actuators and other components.
Pilot communicates with the drone with a operating system, that is a preemptive, real-time multitasking kernel setup to manage up to 64 separate tasks. This kernel includes basic operating system services such as semaphores, mutual exclusion semaphores, event flags, message mailboxes, message queues, task management, fixed size memory block management and time management functions. The execution times for most services in the operating system are both constant and deterministic and do not depend on the number of tasks running in the system. All software and FPGA configuration data are stored in non-volatile Flash memory. When power is supplied to the board, a small boot program is loaded and executed in the DSP. The software CPU on the FPGA initiates every flight control cycle by sending the most recent sensor data to the DSP, effectively becoming the system driver.
Efficient internal and external communication is essential in a multi-processor system. The DSP communicates with the FPGA. Multiple, parallel First-In First-Out (FIFO) components inside the FPGA enable direct communication with the DSP from dedicated hardware components in the FPGA, avoiding information bottlenecks and reducing time delays. The FIFOs also act as buffers between the different components, which helps ensure data integrity. The flexibility the FPGA allows for future addition of communication interface logic, image sensor interfaces, Ethernet, USB, and encryption or other protocols.
Go For The 1 Best For You!!!
A good pilot needs a good flight controller, but one FC isn’t always better than the other. Sometimes it depends on many factors, such as what type of flying you plan to do, and what kind of quadcopter you are flying with. For example some flight controllers are easier to setup, some are better with small size aircraft, while some can do GPS and some cannot. Also there are many clones on the market; they might appear to be similar and cheaper because of the low quality components they use. Some of the most popular FC kits globally available are:
