Presented by:- Suman Kumar

Hornet-1

Dynamics of Drone

INTRODUCTION :

• Quad-rotor helicopters are emerging as a popular unmanned aerial vehicle configuration because of their simple construction, easy maintenance and high payload capacity.

• A quad-rotor is and under-actuated mechanical system with six degrees of freedom and four lift-generating propellers arranged in cross configuration.

• Manoeuvres are executed by varying the speed of the propellers, which causes moments that affect attitude control; and by varying thrust, which affects altitude control. this makes stabilization challenging.

• dronEPIC is a pioneer in research, development, production and operation of cost effective, compact and user friendly Unmanned Aerial Vehicles (UAVs) in India.

• dronEPIC was founded by NIT Jalandhar students in 2012. It was incubated at Mechatronics Laboratory and SAE workshop of NIT Jalandhar.

• It is driven by highly motivated students from various fields and backgrounds such as computer science, electronics and mechanical engineering.

Unmanned Arial Vehical (UAV)

• The UAV is an acronym for Unmanned Aerial Vehicle, which is an aircraft with no pilot on board.

• UAVs can be remote controlled aircraft or can fly autonomously based on pre-programmed flight plans .

• An unmanned aerial vehicle (UAV), commonly known as a drone.

Key Features of Drone

• Payload

• Flight time

• Stability

• Agility

• Maneuverability

• Wind resistance

• Safety

• Portability

• A quadcopter is an underactuated machine which has 6 degrees of freedom which has to be controlled by 4 independent inputs.

• Four different inputs are the four independent angular velocities of motors.

• Six degrees of freedom include three translational along three axis as well as three rotational about all three axis.

Kinematics of Drone

•Pitch (Elevator)

•Roll (Ailerons)

•Yaw (Rudder)

•Hover (Throttle)

Controls

Pitch: It’s the rotation of the multi-rotor about Y-axis.

• Pitch Angle (θ): It’s the angle through which the craft is tilted forward or backward.

• The pitch is produced by varying the rpm of the adjacent motors situated at front/back of the craft.

Roll : It’s the rotation of the multi-rotor about X-axis.

• Roll Angle (ɸ): It’s the angle through which the craft is tilted sideways (left/right).

• The roll is produced by varying the rpm of the adjacent motors situated on the same side of the craft.

Yaw: It’s the rotation of the multi-rotor about Z-axis.

• Yaw Angle (ᴪ): It’s the angle through which the craft is rotated clockwise/anticlockwise.

• The yaw is produced by varying the rpm of the opposite motors.

• Each motor spins in opposite manner than its neighbour.

LINE DIAGRAM WITH CONVENTIONS USED

-y

+y

+x-xl

C

1

2

3

4

Front

Back

Front

Right

Left

+x+

y

+z

+𝜓

+𝜙+𝜃

Throttle: To control the altitude of the multi-rotor

• Hover: To make the multi-rotor stand at a constant altitude.

• Hovering is the state of motion where the resultant force acts along z axis . Equal variations in motor rpm will change the altitude .

• Pitching and rolling states are made use of in order to achieve the translatory motion along x and y axis.

• One thing to be noticed in this case is that the loss of altitude due to the decreased vertical thrust component. Also we have to take the aerodynamic drag into considerations in calculations regarding the motion.

• Following sensors are used in achieving above states of motions with more accuracy.1. Accelerometer

2. Gyroscopic sensor

3. Barometric sensor

4. GPS sensor

Gyroscopic sensor

Accelerometer

Free Body Diagram of Quadcopter

(Forces shown in this fig. is in the body frame)

PHYSICS OF THE QUADCOPTER

MOTORS

• The torque (τ) relation of brushless DC motors used in quadcopter relates input current (I) and no load current (Io) using torque proportionality constant.

• Also the voltage across the motor is equal to the sum of internal resistive losses and back-EMF.

• This helps us in finding out the power of the quadcopter.

• From further simplifying by assuming negligible internal resistance of motor and no-load current, we obtain the final equation for power.

• Thrust produced by one motor

• T= kωk=constant; ω =rpm of motor (in radian per sec)

• Total thrust produced by 4 motors= k(ω1

2+ω22+ω3

2+ω42)

TORQUES

• The total torque acting on the quadcopter about z axis can be divided to drag torque plus the inertial torque. Consider the drag force acting throughout the propeller blade to be acting at the tip and the inertial torque is neglecting because we consider the hovering state of the quadcopter for the sake of simplification. Therefore,

where A is the cross sectional area of the blade at the tip and CD is the drag constant.

• Therefore, all three equations responsible for pitch can be represented as a matrix as follows. Also note that in order to avoid the effect of yaw, adjacent propellers are kept in opposite sense as shown in the diagram. All the counter-clockwise torques are takes as positive torques.

• Factors such as rotational drag forces, blade flapping and surrounding air velocity are neglected in order to simplify the problem.

Aerodynamics Effect

1. How thrust is generated:

By each motor, T=ρctAωm2R2

ρ: Air Density

Ct : Thrust Coefficient

A : Rotor Disk Area

R : Blade Radius

ω : RPM of Motor

Introduction :

• A propeller is a type of fan that transmits power by converting rotational motion into thrust.

• Propeller dynamics can be modelled by both Bernoulli’s Principle and Newton’s Third Law.

Specification Of PropellerThe Propellers are mainly specified by the following :

i) Pitch

ii) Diameter (or Length)

• For example:

If propeller is rated as 1045 (10X4.5), it means Diameter of propeller is 10 inches and pitch is 4.5 inches.

Pitch :

Pitch is defined as "the distance a propeller would move in one revolution if it were moving through a soft solid, like a screw through wood."

• For example, a 21-pitch propeller would move forward 21 inches in one revolution.

• A higher pitch will deliver greater top speeds, but slower acceleration.

Diameter :

Diameter is the distance across the circle made by the blade tips.

• In general, "Diameter is determined primarily by the rpm at which the propeller will be turning and the amount of power that will be delivered to the propeller.“

• The higher the Kv of the motors, the smaller the props need to be. Smaller props allow for greater speeds, but reduced efficiency.

Types Of Propellers:

1.) Standard Propeller

2.) APC Propeller

3.) APC W Propeller

4.) Bambula Propeller

5.) MenZ Propeller

It is very important that both, pitch and diameter, are properly calculated.

If for any given the pitch is too big, the propeller becomes heavy and demands more power than the Motor can reach and vice versa, if the pitch is too small then we have a light propeller that wouldn't absorb the motor's full power.

SELECTION OF PROPELLER :