??Day 3: Advanced UAV Concepts and Hands-On Drone Assembly??

On the third day (24 July, 2024) of our workshop, we delved into advanced topics including mathematical modeling, sensors, and RC communication in UAVs, followed by a practical session in the UAV lab where we assembled our own drones.

Mathematical modelling of Flight Controller

Our day began with a enriching session by ????. ?????????? ???????? regarding mathematical modelling of Flight controller. Although, most flight controllers are pre modeled and made available, they can not be used for all use-cases. As such, one can model his/her own flight controller.

Learnings

Idealistic Body Assumption

To determine the required parameters, we start by considering an idealistic body. The modeling process involves building the solution in both the ground frame and the body frame.

Frame Transformations

A quadcopter UAV is depicted along with its vectors. For a given rotation of the UAV by angles θ, ?, and ψ in the ground frame, the corresponding rotations with respect to the body frame can be determined using simple projections. These projections help in transforming the coordinates from the ground frame to the body frame.

After determining the individual vectors, the equations for the UAV's motion are derived using Newton-Euler's theorem. This involves formulating the equations for both translational and rotational motions. Thus we obtain the equations in terms of angular velocity (of the rotors), moment of inertia, θ, ?, and ψ. The final result depends on the angular velocity. The same result can be obtained using Lagrange's equations too.

Sensors for navigation and stability

This session was headed by ????????. ??. ??. ?????????????? in which we got to know about the various sensors used on UAVs.

Learnings

Sensors play an integral role in any UAV. They guarantee the smooth flight and various features which can be used for analytics, vision etc. The most important sensors are as follows-

• Accelerometers : Accelerometers in UAVs measure acceleration and orientation, aiding in stability and precise control. They are crucial for navigation, often working alongside gyroscopes.
• Gyroscope: Gyroscopes in UAVs measure rotational movement, helping maintain and correct the vehicle's orientation. Gimbals in gyroscopes stabilize and isolate the gyroscope from external movements, ensuring accurate measurement of rotational motion. There are individual sensors, which calculate the change in orientation and then stabilize the device.

• Magnetometer: They are used to measure the Earth's magnetic field, providing accurate heading information.
• Barometer: Barometers are used to measure the pressure. When a barometer is placed above a UAV, it measures a higher pressure during ascent.
• GPS Sensor: GPS sensors are used to find out the current location of the vehicle. They use signals from satellites in the Global Positioning System to get the UAV's position and provide accurate location data.
• LIDAR: Light Detection and Ranging or LIDAR for short uses laser pulses to measure distances by detecting the time it takes for the light to return after hitting an object. In UAVs, it creates high-resolution 3D maps and models of the terrain and objects below.
• SONAR: They work on same principle as the LIDAR. In SONAR, sound waves are used instead of light. SONAR are better suited for water bodies as compared to their light based counterparts.

RC Communication & Protocols

This session focused on the Remote Control Communications and the protocols followed. It was a very informative session by Dr. Sanjeet Kumar.

Learnings

RC communication involves sending commands from a remote control to a device like a drone or car. Some common protocols are as follows-

• PWM (Pulse Width Modulation): Transmits control signals as pulse durations; used in servos and older systems.
• PPM (Pulse Position Modulation): Combines multiple control signals into one line, reducing wiring.
• SBUS: Sends multiple control signals over one digital line; reliable and fast.
• DSM/DSMX: Provides reliable, encrypted communication, used by Spektrum and others.
• Crossfire: Designed for long-range communication with drones, offering high reliability.
• MAVLink: Used mainly in drones for sending telemetry, control commands, and status updates. Works over Serial, UDP, and TCP.

UAV Lab

Last but not the least, UAV Lab proved to be the highlight of the day. We got together in a groups of 5 and assembled a quadcopter in X shape. It was my first ever experience of working with soldering equipment and drones, hence I truly enjoyed it a lot.

Overall, the day proved to be very fruitful. A huge thanks to BIT Mesra for this opportunity!!