This post will outline the main components within a multirotor. Each component and element of a multirotor have to research and decide which solution I chose and why. There are several as outlined below:
This is the structure of the drone. It is what holds all the components together. I need to decide whenever or not to use an existing frame or to design my own. They vary a lot such as the amount of motor arms and battery capacity they can carry, materials and rigidity. They need to be light, strong and functional, they should be able to provide adequate mounting and vibration dampening for the components.
These provide the power for the multi rotor, they turn the propellers. Brushless DC motors can provide the necessary power, they will be controlled with electronic speed controllers (ESC’s) one for each motor. The ESC’s will be connected to the control unit and the batteries.
These provide the lift. They are attached directly to the motors. They will have to carefully be matched to the motor specifications and electronic speed controller ratings, which in turn will have to be matched to the battery and weight of the multirotor.
This is what provides electricity to power the system, most common power sources are batteries, however I will explore alternatives such as fuel cells. It must be light but also provide extreme amounts of energy to the multirotor so high energy density is paramount if I am going to get a decent flight time.
These are the eyes and ears of the drone. They sense the environment around it. Sensor examples include:
- Sonar (as seen above) which accurately gauges distance to obstacles such as the ground.
- Global Positioning System (GPS) which provides spacial location data to an accuracy of about a meter. GPS will be the primary guidance system for the drone.
- Magnetometers which are basically an electronic compass, these provide accurate angle data.
- Piezoelectric gyroscopes, these measure acceleration, which will provide angle and spacial data also.
- Barometers, these measure the pressure of the air, which can be used to calculate altitude.
Each sensor will be used in conjunction with each other. For example magnetometers will be used in conjunction with piezoelectric gyroscopes, some sensors multiple ones will be used and an average reading will be taken, in case one sensor is malfunctioning. This gives the drone redundancy. Sensors are very cheap these days with the advent of smart phones so this is now possible.
This is the brains of the drone. It will read the measurements from the sensors, the commands from the user (from the radio) and then it will then manage the Electric speed controllers and also the camera system/any peripherals attached to the drone. There is a selection of chips available that I could use, with relevant industry standard open sourced software respectively.
The data radio (in sets of two) will be used to upload commands and coordinate data to the drone. It can also be used for direct control via use of a joystick, however latency problems may prevent this, however I will test this. It also downloads information about the drone, such as battery levels, position data and raw sensor data.
This is a standard RC radio system, they are well proven and highly developed such as the 2.4ghz spread spectrum frequency hopping radios of today. They will be used to directly command the drone for manual control or to change the mode for example from manual to autonomous or different control modes. These may not be necessary however they are a good fall-back since they offer extremely low latency connections.
Video downlink radios:
In a pair these radios will send the video feed from the camera to a receiver on the ground station. Most likely an analogue system due to the complexities of transmitting digital video but digital will be explored.
Camera and gimbal:
The camera will record professional quality high definition video and photographs it will also send live video to the video transmitter. It will be attached to a gimbal system as shown below. The camera can also be used in conjunction with the sensor data such as the GPS to create for example accurate aerial maps or even 3d models of environments along with the obvious uses such as aerial video.
The camera gimbal will be used to isolate the camera from the movements of the body, remove vibrations and aim the camera. It will be powered by DC brushless motors and controlled via the control unit. This video demonstrates such a gimbal:
I will elaborate on each of these components further in the project as I design my drone.