??Day 2: Diving Deeper into UAV Mechanics and Design ??

After an enriching first day that laid the groundwork with fundamental concepts and hands-on sessions, we delved deeper into the intricacies of UAV design and operation on Day 2 (23th July, 24) . Our day was divided into theoretical and practical sessions.

Flight Dynamics of UAV

Our first session for the day was headed by Dr. Priyank Kumar who introduced us to the UAV aerodynamics. We were introduced to basic working principles of UAV. Some of the elementary terms were -

• Thrust: The force that propels the UAV forward
• Drag: The resistance force that opposes the UAV's motion through the air.
• Lift: The force that holds the UAV in the air, counteracting its weight.
• Weight: The force due to gravity pulling the UAV downward.

Key Learnings of this Session-

• Principle of Aerodynamic Lift: In case of aero foil/blade the air above the wing travels a longer path and at a higher velocity, resulting in lower pressure, while the air below the wing travels a shorter path and at a lower velocity, resulting in higher pressure. This pressure difference generates lift, allowing the airplane to rise. This principle highlights the correlation between airflow velocity, pressure, and the generation of lift, which is fundamental to the principles of flight.

F = Constant x ρ x V2

• Navier-Stokes Equation: A set of partial differential equations that describe the motion of viscous fluid substances such as liquids and gases. Upon solving them, we obtain contain diagrams for pressure and velocity.
• Throttle/Hover: If all four propellers run at the speed that balances the drone's weight, it will hover. If they run faster, the drone will ascend; if slower, it will descend.

Preliminary Design of UAVs

Flight Dynamics of UAV was followed by "Preliminary Design of UAVs" taught by Prof. Abhishek. This session focused on the design of UAVs at the core level. It involved various processes and steps to obtain the best case scenario for designing a UAV.

The basic steps involved in the same were-

1. Mission Requirements: Requirements such as payload, flight time, travel distance have to be predetermined
2. Initial Input Parameters: The initial input parameters such as number of rotors have to be decided
3. Initial Weight Guess: With the inputs in place, an initial calculation is done to approximate the total vehicle weight
4. Power Calculation: Power calculation is done using various formulas such as the Helicopter theory. More specific formulas can be used as per the case. Power of the rotor = 1.15× (Thrust)3∕2?/ √(ρ × A)
5. Derived Parameters: The energy, capacity, KV extra are determined
6. Weight Estimation: With the new parameters in place the new weight is determined and compared with the initial weight guess. If they do not match, estimation and calculations are done again.

Preliminary design of a UAV is a crucial process and can have significant effects on the efficiency, costs and weight of the vehicle.

Department of Space Engineering and Rocketry's Aerodynamics

Next, we visited the Rocketry and Aerodynamics department. We were shown the basics of Rocket fuels, which are mainly divided into 3 types-

• Solid fuels: Solid rocket fuels are easiest to design and are easy to handle, but they have inflexible thrust control, as the oxidation is non-stop and doesn't have control mechanism.
• Liquid fuels: The thrust control is more efficient in this case. The cons lie in the fact that liquid fuels require complex plumbing and have to be maintained at a certain temperature
• Hybrid fuels: These involve a combination of solid and liquid. A lot of research is being done to utilize hybrid fuels more

We were also introduced to different machinery used in mixing and creation of various fuels along with research and experimentation. Later, we were shown the high velocity wind tunnels which are used to test the UAVs/rockets at different wind speeds.

UAV Lab

Drone FPV simulator

A drone FPV (First Person View) simulator is a software application designed to simulate the experience of flying a drone with an FPV camera setup. A simulation software called LiftOff was used. We got to try controlling a drone. It was certainly a hard task to control a drone.

Brushless DC motor

We were introduced to the working principal of the brushless DC motors which are used in drones by Dr. K. Mahto. The motor's work on the principal of electromagnetic induction due to a current carrying wire. Multiple electromagnets are used to rotate the central electromagnet, which then produces rotational motion. Multiple copper coils are wound around soft-iron cores to create electro magnets, which are then arranged in a circular manner. The current in the coils are switched on or off systematically depending on the position of the of the motor.

This system involves the use of FETs, diodes, resistors etc. to implement the DC motor.

Thrust demonstration

We were shown a "jugaad" motor, propellor, ESC and battery setup which demonstrated the thrust applied due to the propellor's rotation.

Case1: A propellor of 16 inch was used. The voltage was gradually increased, which lead to increase in RPM of the rotor. The thrust was measured using a device.

Case2: A propellor of 15 inch was used. The thrust measure was approximately 100g less as compared to Case1.

This simple demonstration helped us understand the correlation of thrust and propellor length, thrust and voltage. The lack of thrust in Case2 can be compensated with a higher voltage battery.

The overall day went great and we gained a lot of knowledge about the actual core concepts of drone design and aerodynamics. Even though my brain did get overloaded with a lot of information today, it was worthwhile. Really looking forward to the sessions ahead.