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Mechanical Engineering

Mechanical Engineering

posted 3 weeks 19 hours ago
(1)

Alternator or Synchronous Generator

Definition of Alternator

The definition of alternator is hidden in the name of this machine itself. An alternator is such a machine which produces alternation electricity. It is a kind of generators which converts mechanical energy into alternating electrical energy. It is also known as synchronous generator.

History of Alternator

Michael Faraday and Hippolyte Pixii gave the very first concept of alternator. Michael Faraday designed a rotating rectangular turn of conductor inside a magnetic field to produce alternating electric current in the external static circuit. After that in the year of 1886 J.E.H. Gordon, designed and produced first prototype of useful model. After that Lord Kelvin and Sebastian Ferranti designed a model of 100 to 300 Hz synchronous generator. Nikola Tesla in 1891, designed a commercially useful 15 KHz generator. After this year, poly phase alternators were come into picture which can deliver electric currents of multiple phases.

Use of Alternator

The power for electrical system of modern vehicles produces from alternator. In previous days, DC generators or dynamos were used for this purpose but after development of alternator, the dc dynamos are replaced by more robust and light weight alternator. Although the electrical system of motor vehicles generally requires direct electric current but still an alternator along with diode rectifier instead of a DC generator is better choice as the complicated commutation is absent here. This special type of generator which is used in vehicle is known as automotive alternator.

Another use of alternator is in diesel electric locomotive. Actually the engine of this locomotive is nothing but an alternator driven by diesel engine. The alternating electric current produced by this generator is converted to DC by integrated silicon diode rectifiers to feed all the dc traction motors. And these dc traction motors drive the wheel of the locomotive.

This machine is also used in marine similar to diesel electric locomotive. The synchronous generator used in marine is specially designed with appropriate adaptations to the salt-water environment. The typical output level of marine alternator is about 12 or 24 volt. In large marine, more than one units are used to provide large power. In this marine system the power produced by alternator is first rectified then used for charging the engine starter battery and auxiliary supply battery of marine.

Types of Alternator

Alternators or synchronous generators can be classified in may ways depending upon their application and design.
According to application these machines are classified as-

Automotive type - used in modern automobile.

Diesel electric locomotive type - used in diesel electric multiple unit.

Marine type - used in marine.

Brush less type - used in electrical power generation plant as main source of power.

Radio alternators - used for low brand radio frequency transmission.

These ac generators can be divided in many ways but we will discuss now two main types of alternator categorized according to their design. These are-

Salient pole type
It is used as low and medium speed alternator. It has a large number of projecting poles having their cores bolted or dovetailed onto a heavy magnetic wheel of cast iron or steel of good magnetic quality. Such generators are characterized by their large diameters and short axial lengths. These generator are look like big wheel. These are mainly used for low speed turbine such as in hydral power plant.

Smooth cylindrical type
It is used for steam turbine driven alternator. The rotor of this generator rotates in very high speed. The rotor consists of a smooth solid forged steel cylinder having a number of slots milled out at intervals along the outer periphery for accommodation of field coils. These rotors are designed mostly for 2 pole or 4 pole turbo generator running at 36000 rpm or 1800 rpm respectively.








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Mechanical Engineering

posted 3 weeks 19 hours ago
Introduction:
                Transmission is the mechanism which is used to transfer the power developed by engine to the wheels of an automobile.  The transmission system of an automobile includes clutch, gear box, propeller shaft axle and wheels, etc.

The term ‘Transmission’ is used for a device which is located between clutch and propeller shaft. It may be a gear box, an over drive or a torque converter, etc.

Clutch:
           

Clutch is used to engage or disengage the engine to the transmission or gear box.

When the clutch is in engaged position, the engine power or rotary motion of engine crankshaft is transmitted to gear box and then to wheels.

 When clutch is disengaged, the engine power does not reach to gear box (and to wheels) although engine is running.

Clutch is also used to allow shifting or changing of gears when vehicle is running.

 For shifting gears, clutch is first disengaged then gear is shifted and then clutch is engaged.

Clutch has to be disengaged to stop the vehicle and also at the time of idling.



Principle of the clutch:

                It operates on the principle of friction.

When two surfaces are brought in contact and are held against each other due to friction between them, they can be used to transmit power.

If one is rotated, then other also rotates.

 One surface is connected to engine and other to the transmission system of automobile

 Thus, clutch is nothing but a combination of two friction surfaces.

 


 

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Mechanical Engineering

posted 1 year 2 weeks ago
What is a drone and how do drones work is answered here in very easy to understand language. Drone technology is constantly evolving as new innovation and big investment is bringing more advanced drones to the market every few months.
 
In this article, I will discuss UAV technology on one of the most popular drones on the market which has plenty of top drone technology.  Most drones will have very similar systems incorporated.
 
Unmanned aerial vehicle technology and science in the widest aspect covers everything from the aerodynamics of the drone, materials in the manufacture of the physical UAV, to the circuit boards, chipset and software which are the brains of the drone.
 
One of the most popular drones on the market is the Phantom 2 Vision+.  While slightly old now, it uses plenty of advanced technology and it is very popular with professional cinematographers.  This UAV is ideal to explain drone technology because it has everything in one package.  It includes the UAV, gimbal and camera and uses some of the top drone technology on the market today.
 
In only a few months since writing this article, some new and highly advanced drones such as the DJI Phantom 3, Phantom 4 and Inspire 1 have come to the market. Please read about these latest drones and innovations in our drone reviews section.
 
How Drones Work
 
A typical unmanned aircraft is made of light composite materials to reduce weight and increase maneuverability. This composite material strength allows military drones to cruise at extremely high altitudes. Drones are equipped with different state of the art technology such as infra-red cameras(military UAV), GPS and laser (military UAV). Drones can be controlled by remote control system or a ground cockpit. Drones come in a wide variety of sizes, with the large drone mostly used for military purposes such as the Predator drone, other smaller drones which can be launched by hand, to other unmanned aircraft which require short runways. An unmanned aerial vehicle system has two parts, the drone itself and the control system.  
 
The nose of the unmanned aerial vehicle is where all the sensors and navigational systems are present. The rest of the body is complete innovation since there is no loss for space to accommodate humans and also light weight. The engineering materials used to build the drone are highly complex composites which can absorb vibration which decreases the noise produced.
 
What Is A Drone – UAV Technology
 
Below we examine the science and drone technology behind the DJI Phantom 2 Vision+ UAV.  Another terrific article is a drone components overview.  This gives you a breakdown of the individual components seen in most drones.
 
Radar Positioning & Return Home
 
The flight radar displays the current position and location  of the drone in relation to the pilot.
Exceeding the control range of the remote control will trigger ‘Return-to-Home’, meaning the UAV will automatically fly back to its takeoff point and land safely.
Gyro Stabilization, IMU And Flight Controllers
 
Gyro stabilization technology is one of the components which gives the drone it’s smooth flight capabilities. The gyroscope needs to work almost instantly to the forces moving against the drone.  The gyroscope provides essential navigational information to the central flight controller.
 
The inertial measurement unit (IMU) works by detecting the current rate of acceleration using one or more accelerometers. The IMU detects changes in rotational attributes like pitch, roll and yaw using one or more gyroscopes.  Some IMU include a magnetometer to assist with calibration against orientation drift.
 
The Gyroscope is a component of the IMU and the IMU is an essential component of the drones flight controller. The flight controller is the central brain of the drone.
 
Here is a terrific article which covers gyro stabilization and IMU technology in drones.
 
Onscreen Real-Time Flight Parameters
 
Keep track of current flight telemetry and see what your drone sees on your mobile device.
 
No Fly Zone Drone Technology
 
In order to increase flight safety and prevent accidental flights in restricted areas, the new firmware for the Phantom UAV series includes a “No Fly Zone feature”.  These no fly zones have been divided into two categories: A and B.
 
GPS Ready To Fly Mode Drone Technology
 
When the compass s is calibrated, the drone then seeks the location of GPS satellites. When more than 6 are found, it allows the drone to fly in “Ready To Fly” Mode.
 
Internal Compass & Failsafe Function
 
Allows the UAV and remote control system to know exactly it’s flight location.  Calibration of the Compass is required to set a home point.  The home point is the location where the drone will return to in case of loss of signal between the drone and the remote control system.  This is also know as “fail-safe function”.
 
FPV (First Person View) Drone Technology
 
What FPV means is “First Person View” which means a video camera is mounted on the unmanned aerial vehicle and broadcasts the live video to the pilot on the ground so the pilot is flying the aircraft as if he/she was on-board the aircraft instead of looking at the craft from the pilot’s actual ground position.
 
FPV allows the unmanned aircraft to fly much higher and further than you can from the looking at the aircraft from the ground.  FPV control allows for more precise flying around obstacles especially with unmanned aerial vehicles which can easily fly indoors and through forests via FPV where you would not be able to see obstacles from a fixed position.
 
Firmware And Flight Assistant Port
 
The flight control system communicates with a PC Assistant through a Micro-USB cable. This allows configuration of the UAV and upgrade the firmware.
 
A very simple description of a drone is that it is a flying computer with a camera attached. Drones have firmware which can be updated to fix bugs and add new features.
 
LED Flight Indicators
 
These are found at the front and the rear of the drone. The front LEDs are for indicating where the nose of the drone is. The rear LEDs flight indicators light up to show the drones current flight status when the flight battery is turned on.
 
UAV Remote Control System
 
This is the wireless communication device using the 5.8 GHz frequency band. The drone and the remote control system should already be paired when it leaves the factory.
 
UAV Remote Control Receiver 
 
The location of the 5.8 GHz receiver technology link button is under the UAV.
 
Range Extender UAV Technology
 
This is a wireless communication device which operates within the 2.4 GHz frequency. It is used to extend the range of communication between the smartphone or tablet and the drone in an open unobstructed area.  Transmission distance can reach up to 700 meters. Each range extender has a unique MAC address and network name (SSID).
 
Some of the latest drones out of the box can fly using  range to a distance of up to 3.1 miles (5km).  Products such as FPV range extenders are very popular which can push the distance even further.
 
Smartphone App Featuring Ground Station Function
 
Smartphone App from Google Play or the Apple Store. The app allows for full control of the drone. There is a specific feature called ground station function on the Phantom 2 Vision+ quadcopter.  This allows for flight missions by placing location waypoints and setting waypoint altitude and overall speed.  The UAV should the be able to execute the flight mission automatically.
 
High Performance Camera
 
The Phantom 2 Vision+ carries an extremely high quality camera and a removable 4GB micro SD card. It shoots full HD video at 1080p/30 frames per second and 720p/60 frames per second, giving you crystal clear video and the option for slow motion shots.
 
The latest drones from DJI, Walkera, Yuneec and many other manufacturers now include cameras which can shoot film in 4k video and can take 12 megapixel stills.  The latest DJI Zenmuse Z3 is an integrated aerial zoom camera and is optimized for still photography.  The Zenmuse has a 7x zoom lens which is a first in aerial cameras.
 
Many of the earlier drones used cameras which were not fully suitable for aerial filming.  Many of these aerial videos had barrel distortion because of the wide angle lens.  The latest drones such as DJI Inspire 1, Phantom 3 Professional and Phantom 4 have a camera which is specifically designed for aerial filming and photography.
 
Gimbals & Tilt Control
 
The gimbal allows you to tilt the camera while in flight, creating unique angles.  It uses a 3 axial stabilized gimbal and has 2 working modes. Non-FPV mode and FPV mode.
 
Practically all the latest drones have integrated gimbals and cameras.  The leader in gimbal technology is DJI with their Zenmuse range.
 
Drones With Sensors
 
Multispectral, Lidar, Photogrammetry and Thermal sensors are now being used on drones to provide 3D models of buildings and landscape; Digital Elevation Maps (DEMS) of land, and provide precision data on the health of crops, flowers, fauna, shrubs and trees.
 
Anti-Drop Kit
 
Helps to keep the stabilizer and camera connected to the unmanned aircraft.
 
Video Editing Software
 
Having an excellent quality video software is essential for post processing. Adobe DNG raw means that all the original image information is retained for later processing. An Adobe lens profile for barrel distortion removal is available for the DJI Phantom 2 Vision+ camera.
 
Operating Systems In Drone Technology
 
Some unmanned aircraft use MS Windows operating systems.  However more and more UAV innovators are now using different versions of Linux.  The Linux Foundation recently launched the Dronecode project. The Dronecode Project is an open source, collaborative project that brings together existing and future open source unmanned aerial vehicle projects under a nonprofit structure governed by The Linux Foundation. The result will be a common, shared open source platform for Unmanned Aerial Vehicles (UAV).
 
Drones in some ways are flying computers.  With an operating system, flight controllers, main boards with programmable code, they can also be hacked into.  Like a computer, you can also protect your drone from hackers.
 
Latest Innovative Technological Drones
 
The latest advanced drones with patented technologies are the following;
 
  • DJI Phantom 4 – with “Vision” collision avoidance technology. Multi purpose drone including aerial filming, photography and photogrammetry.
  • DJI Inspire 1 – Patented design and motors.  Multi purpose drone with gimbals for professional aerial filming, photography, photogrammetry, multispectral and thermal imaging.
  • Yuneec Typhoon H Pro – uses the patented Intel “Realsense” collision avoidance technology. Great for professional aerial photography and filming
  • 3DR Solo –  multi purpose drone and can be used for professional aerial photography, filming, photogrammetry and thermal imaging.
  • Intelligent Flight Systems
All these latest drones have intelligent flight controllers and modes such as Follow Me, Active Tracking, Waypoints, Return To Home and many others.

 

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