![]() There are quite a few of algorithms to deduce a path from such a map. A point cloud map is a map of points where each point correspond to a point in 3D space. The rate of this scan can be as high as 20 milliseconds per sensor.Based on these range information, we can generate a two-dimensional (2D) map of the surrounding environment. This expander will help us address only one of the ToF sensors at a time without creating any conflict.Once powered up and configured correctly with the main CrazyFlie deck, the firmware will drive each of these ToF sensors to capture range Information in the surrounding environment. This is ideal for us as we're only using 13 of them. This expander can support upto 16 channels. As a workaround, we are using an I2C bus expander - PCA9555. When the master device calls this address, which slave is going to answer? That's right! It will create a conflict because all the slave ToF devices has the same address. Each of these sensors share the same I2C address (which is 0x29). These sensors are from STMicroelectronics and they can measure accurately up to 4 meters at a rate of 50 Hz. When called upon, only the respective slave should answer.In this design, we have thirteen (13) VL53L1X Time-of-Flight (ToF) sensors mounted around the deck facing different orientations covering 360 degree view. Each slave has a device ID (7 or 10 bits long), master uses to address them. In our case, CrazyFlie main board will be the "master" and all other decks will be "slave"s. I2C protocol uses two wires known as SDA (Data) and SCL (Clock) to communicate back and forth between a main device called master and a second device/sensor called slave. These decks communicate with the main PCB using I2C protocol. They have couple of such decks on their official website for various sensing and actuation functions such as RGB LED deck, micro SD Card deck, wireless charging deck etc. Finally this work was published in Australasian Conference on Robotics and Automation (ACRA 2020).How does it work?CrazyFlie drone platform can support multiple expansion decks. We had to go a bit further upgrading the stock firmware to support this new obstacle avoidance deck. But we couldn't find such a device to match the requirements in the market.Luckily, CrazyFlie support custom decks and we could make one ourselves. ![]() This LiDAR implementation will help us generate a map of the surrounding environment. The only viable alternative is to build a type of a miniaturised Light Detection And Ranging (LiDAR) on top of the drone which is light-weight and doesn't consume much energy. In order to expand the flight time, cameras is not even an option. ![]() Obviously the human controller/pilot will not have a clear line of sight with the drone almost all the time due to safety reasons. How can one navigate this tiny drone, without having to constantly see it?I had this research problem at hand to design a micro aerial vehicle that can navigate itself inside a collapsed building. Otherwise the drone might crash into a wall or an obstacle.If someone plugs in a small camera to capture the view to navigate, the battery would drain faster and the drone would not be able to fly any longer. If it were to fly, the pilot needs to have a clear line of sight with the drone. However, the stock drone platform does not have any obstacle sensing ability around it. The more power it uses or heavier it is, shorter the flight time. ![]() This deck can be used to detect obstacles around the CrazyFlie drone and help navigation much easier without relying on a line of sight view with the drone.CrazyFlie runs on a small Li-Ion battery that accounts for a maximum 7 minutes flight time with minimum payload. It includes the main deck PCB and PCBs for Time-of-Flight sensors. It being an open source platform with both the hardware and firmware resources available freely online in GitHub repositories, users are given an opportunity to design a "deck", which is a pluggable expansion board on top of the main drone platform PCB.What is this about?This hardware design is a PCB for such a custom deck with exact dimensions to match CrazyFlie 2.x drones. This drone platform is widely used among the robotics research community for micro UAVs and swarm robots. Crazyflie is a lightweight micro aerial vehicle or in simple terms, a mini drone from a company called Bitcraze. ![]()
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