1.1 Quad-copter’s Best Features
Following are some of the best features of the quad-copter.
1.1.1 Quad-copter incorporate features of pitched and co-axial
Copters are either pitched or coaxial while Quad-copters have the abilities of both. Pitched are agile while coaxial are more stable as they use two layers of rotors. Quad-copters are perfect blend of both. Gyro enhances stability.
Control of quad-copters by a joy stick on a remote transmitter. The receiver on quad-copter processes instructions. The signal combined with output from altitude sensor sets height of Quad-copter. The controller than provides signal to ESCs , which controls the motors.
The quadcopter has diverse aerodynamics for flight. Acc. to law of motion every action has an equal and opposite reaction. The four motors, two rotating clockwise and two rotating anti-clockwise negate the action of any force.
Figure CHAPTER 2?1 Aerodynamic of Quadcopter
1.2 Quadcopter applications
Quadcopters are not only the flying toys. They have many beneficial uses as well. Following are the ways in which quadcopter can be used.
University researchers use quadcopter as a research tool. Information related to robotics, flight control and real time systems can be gathered using quadcopters.
Apart from this quadcopters are agile and maneuverable. They can go into dangerous places from research work and data acquisition.
1.2.2 Commercial use and photography
Nowadays Quadcopters are used for aerial images and videos. Modern quadcopters are stabilized by 3-axis gyro technology, allowing to capture images without “jello” effect.
1.3 GPS Technology
GPS or global positioning system is a network of orbiting satellites that send precise information of their location in space back to earth. The signals are obtained by GPS receivers, such as navigation devices and are used to calculate exact position, speed, altitude and time at the vehicles location. The procedure uses the Doppler shift of the radio signals as the satellite passes overhead. (Similar Doppler shift accounts for the change in sound of a train whistle as a locomotive speeds by).
An inertial measurement unit is an electric device that measures and reports a body’s specific force, angular rate and sometimes the magnetic field. IMU’s are typically used to maneuver aircrafts, in UAVs and in space crafts including satellites and landers.
The IMU are of different types, some have accelerometer and gyroscope on single chip and some have magnetometer too. The IMU we used is MPU6050 which has accelerometer and gyroscope
Figure CHAPTER 2?2 Publication per year on IMU
1.4.2 Principle of IMU
IMU senses linear acceleration using accelerometer and angular velocity by gyroscope. Some also have a magnetometer which are used as a direction reference. Typical IMU has one accelerometer, one gyroscope and magnetometer per axis.
The properties and capabilities of an IMU are best understood with a basic array signal model. For simplicity, assume an array consisting of Ns accelerometer and N? gyroscope triads. Further, assume that the sensors are identical, their sensitivity axes aligned, and that they have an additive measurement error. The measurements of the ith accelerometer triad and jth gyroscope is modelled as
Figure CHAPTER 2?3 Forces sensed by accelerometer in IMU
A gyroscope is a spinning wheel or disk in which the axis of rotation is free to assume any orientation by itself. When rotating, the orientation of this axis is unaffected by tilting or rotation of the mounting, according to the conservation of the angular momentum. Because of this gyroscope are useful for measuring or maintaining orientation.
Gyroscopes based on other operating principles also exist, such as the electronic, microchip-packaged MEMS gyroscopes found in consumer electronics devices, solid-state ring lasers, fiber optic gyroscopes, and the extremely sensitive quantum gyroscope.
18.104.22.168 History of gyroscope
Figure CHAPTER 2?4 Gyroscope
In 1852, Foucault used it in an experiment involving the rotation of the Earth. It was Foucault who gave the device its modern name, in an experiment to see the Earth’s rotation (Greek gyros, circle or rotation), which was visible in the 8 to 10 minutes before friction slowed the spinning rotor. In the 1860s with the advent of electric motors , the continuous spinning of gyroscope became possible, this lead to the advent of a prototype, heading indicator, a more complex device known as gyrocompass.
In the first several decades of 20th century, unsuccessful attempts to use gyroscope as the basis of early black box navigation system were made. Similar principal was used for inertial navigation system of ballistic missiles.
An accelerometer is an electromechanical device that measures acceleration forces. These forces may be static, like the constant force of gravity pulling at our feet, or they could be dynamic – caused by moving or vibrating the accelerometer. There are many types of accelerometers that have been developed. The vast majority is based on piezoelectric crystals, but they are too big and clumsy. People tried to develop something smaller, that could increase applicability and started searching in the ?eld of microelectronics. They developed MEMS (micro electromechanical systems) accelerometers.
The ?rst micro machined accelerometer was designed in 1979 at Stanford University, but it took over 15 years before such devices became accepted mainstream products for large volume applications. In the 1990s MEMS accelerometers revolutionized the automotive-airbag system industry. Since then they have enabled unique features and applications ranging from hard-disk protection on laptops to game controllers. More recently, the same sensor-core technology has become available in fully integrated, full-featured devices suitable for industrial applications. Micro machined accelerometers are a highly enabling technology with a huge commercial potential. They provide lower power, compact and robust sensing. Multiple sensors are often combined to provide multi-axis sensing and more accurate data.
22.214.171.124 Principal / Working
Accelerometer measures proper acceleration which is the acceleration it experiences relative to free fall. An accelerometer at rest relative to the Earth’s surface will indicate approximately 1 g upwards, because any point on the Earth’s surface is accelerating upwards relative to the local inertial frame. To obtain the acceleration due to motion with respect to the Earth, this “gravity offset” must be subtracted and corrections made for effects caused by the Earth’s rotation relative to the inertial frame.
126.96.36.199 Types of Accelerometer
There are various ways to make an accelerometer. Two of them are described here.
i. Accelerometers having piezo-electric effect
ii. Accelerometer having capacitive effect
Accelerometers having piezo-electric effect contain microscopic crystal structures that get stressed by accelerative forces, which causes a voltage to be generated. Based on the generated voltage the acceleration is calculated.
Accelerometers having capacitive effect sense changes in capacitance and determine acceleration based on that change.