Using Encoders to Measure the Speed, Rotation, and Direction of the 4-Wheel Robot - Research Paper Example

1 Introduction Robotics is a science that combines engineering design, manufacture and applications and restructuring. The aspects of this science major are programming, mechanics, and electronics. Robotics was adopted in the early learning of many Western countries, which was not the case in Arab countries as robots are used in competitions. This resulted in me trying to enlighten the community about this powerful technology. As a machine, a robot has the potential of making decisions but the difference is that they have intelligent behavior unlike other machines. It is a machine capable of mechanical movement that is automatically set by software and can do various tasks in an orderly fashion by sensing their surroundings. This makes robots to be used in many different fields such as heavy industries, scientific exploration, medicine and others, because of their ability to perform tasks that may be viewed as difficult, hazardous, or tedious for human beings with high accuracy and speed. الاستماع قراءة صوتية للكلمات   القاموس - عرض القاموس المفصل 1.1 Aim The aim of the project is to use encoders to measure the speed, rotation, and direction of the 4-wheel robot design by attaching modifying its design. This robot will react with the surrounding to avoid any collision with obstacles. 1.2 Objectives The main objectives of this project are: To develop a 4wheel robot using microcontroller and infrared sensor To design a 4 wheel Robot platform with an ability to measure the rotation of the robot and direction to finish the project work on time 1.3 Knowledge for the basis of the project The project is based on the following premise Computer program such us ISIS or c programming Embedded system Modeling system and design Sensors condition Computer interfacing Feedback control Actuators and power electronics Signal condition Hardware interfacing 2. Summary of background (Work & research already done) 2.1 Digital Encoders An optical encoder can be defined as an electro-mechanical device that has a capacity to convert the movement of mechanical parts into digital signals. There are many different types but the most common is the Rotary encoders. They are used in multiple domains that require position measurements. Optical encoders are generally accurate because of their sensitivity, which is sometimes affected by certain environmental conditions. 2.1.1 Operation Optical encoders operate using light since they consist of a disk fitted on a rotating shaft. The disk has transparent and opaque sectors, and with a light source focuses on the disk. When the disc rotates, the light passes through these sectors, creating a pattern that is read by a sensor on the opposite side of the light source. The sensor then decodes the resulting pattern, translating the mechanical movement into digital signals. 2.1.2 Types Rotary optical encoders come in two main types: Absolute encoders Incremental encoders. The difference between is the disk movement and how the movement is interpreted. 2.1.3Incremental Encoders Incremental encoders, also called relative encoders, feature a disk that has transparent and opaque sections that are equally distributed. Incremental encoders measure the movement by counting the number of alternations of transparent and opaque sectors that pass in front of the sensor. They are not as accurate as absolute encoders are, as a simple misreading error or interference can cause a miscount and render a wrong result. 2.1.4 Absolute Encoders Absolute encoders use a disk that has a unique pattern. These encoders are the most accurate, and because they calculate the result based on a combination of physical disk reading and code interpretation, the result will be accurate even in the event of some small interference. The rotation of the disk translates into a code, named the gray code. 2.2Advantages, Disadvantages and Advances of Digital encoder 2.2.1Advantages Digital There is a choice between incremental or absolute encoder output Fast 2.2.2Disadvantages Fairly complex with sensitive digital parts Can be harmed by contamination Prone to mechanical failures 2.2.3 Advances Incandescent indicator lights replaced by long-life LED’s Glass disks replaced by steel and plastic disks Durability of encoder electronics. 2.3 Dc motor Mechanical energy is converted into electric energy by an electric motor and a dynamo converts mechanical energy into electric energy. Household appliances have electric motors fitted in them. Most electric motors work by electromagnetism, but motors based on other electro mechanical phenomena, such as electrostatic forces and the piezoelectric effect, also exist. Most magnetic motors are rotary, but linear motors also exist. 2.4 Pulse width modulation The pulse-width modulation method produces an analogue output by setting the duty cycle of the pulse signal. The duty cycle is the percentage of the time t-high of the output waveform to the period of the output waveform. The produced analogue voltage is proportional to the duty cycle. Therefore, any analogue voltage level can be produced by setting an appropriate duty cycle. The PWM is able to adjust the speed of the motor by adjusting the duty cycle and hence the voltage supplied to the motor. 2.5 Microcontroller A microcontroller is a computer designed specifically to perform certain tasks. It uses memory to store the programmed commands, to the implementation of these commands such as operating, and fire, timing, counting, arithmetic and other operations. Some of the devices with embedded microcontrollers include mobile phones and electronic household appliances. Properties microcontroller Most important of these properties are: 1 – it is usually found inside another device. 2 – They work for specific tasks. What is in microcontroller Contains a slide microcontroller as shown in the image data processor, RAM and ROM memory, ports of Input and Output (I / O interfaces), timers and other systems such as transformers representative values to digital (ADC). CPU This is the heart of microcontroller and varies according to the user as well as the device manufacturer for example; data processor used in the mobile device is different from that used in a microwave oven. Memory it is divided into RAM and ROM. The RAM is used to store information and range in size between 25 bytes and 4 KB by microcontroller. The ROM ranges in size from 512 bytes and 4096 bytes have sizes up to 128 KB in some microcontrollers. Ports, entrances, and exits. These ports run the LED lights and relays. The number differs according to the microprocessor. Serial port Serial port allows the exchange of information between microcontroller and other devices such as computers and other microcontroller. Provisional Allows microcontroller to do tasks for specific periods of time Analog-to-digital converter It translates the information is within the Authority representative (Analog) to digital form (Digital) so that microcontroller of understanding and responding to them. Work in progress The work in progress is a comparison of different types of shaft encoders. As shown in table 1: Shaft Encoder Type of the Component Lynx motion Quadrature Motors Encoder Cytron Incremental Rotary Encoder Bourns EN Optical Encoder Ease of use Easy hard easy Frequency 15khz 100khz Pulse 480 pulse 500 pulse 400 pulse Cost $ 24.95 $133.36 $37.73 installation Direct Install Using coupling Using coupling Table 1 The table shows three types of shaft encoders for the project. The product that will be preferred is the one that has lower costs and has a relatively ease of use. CONNECTING TO MECHANISM An encoder is a high accuracy instrument that requires care when installing. This encoder can be connected to rotating shafting of motor using elastic shaft coupling. 3 The specification for any hardware, software or other artifact you intend to produce Hardware General 3.1 The Shaft Encoders The speed and direction of each motor is measured by two encoders that are mounted on the back ends of the motors. 3.2 The Shaft Encoder - What is it? The encoder is a sensor attached to a rotating object (such as a wheel or motor) to measure rotation. By measuring rotation your robot can do things such as determine displacement, velocity, acceleration, or the angle of a rotating sensor A typical encoder uses optical sensor(s), a moving mechanical component, and a special reflector to provide a series of electrical pulses to your microcontroller. These pulses can be used as part of a PID feedback control system to determine translation distance, rotational velocity, and/or angle of a moving robot. Specification GHM-04 motor RPM under load = 7500 rpm   - Encoder = 120 cycles per revolution   - Encoder = 480 quadrature counts per revolution   - Frequency = 15 kHz and 30 kHz   - 3428 quadrature counts per inch with a 2.5" tire Soft ware Embedded system The ability to organize and process information is the key to success in the modern age. Computers are designed to handle and process large amounts of information quickly and efficiently, but they cannot do anything until someone tells them what to do. C is designed as a bridge between the programmer and the raw computer. The idea is to let the programmer organize a program in a way that he can easily understand. The compiler then translates the language into something that the machine can use. It is one of the most widely used languages in the world and is stable. C is a highly portable language oriented towards the architecture of today's computers. C is a programming language that allows a software engineer to communicate efficiently with a computer. It is a highly flexible and adaptable language and since its creation, it has been used for a wide variety of programs including firmware for microcontrollers, operating systems, applications, and graphics programming. C's design has significant advantages: Source code is highly portable Machine code is efficient It compliant for all systems. Risk and contingency plans There some of the risk may accurse during the work with their contingency plans. Types of risk May accurse % Contingence plan Health problem 10 Bring evidence paper from hospitals Computer broken 10 Save the Works in flash Memory Flash memory broken or lost 20 Have a margine for the Works Lab availability 20 Find the time availability of the lab Have to go to UAE 5 Take the laptop and save programme that relative to my project Miss some information 10 Writ everything in note book especially for project. 10 Incompatibility from materials 20 Looking carefully at the characteristics Delivery delays 10 Have a Security margin Table 2 http://docs-europe.origin.electrocomponents.com/webdocs/0dc2/0900766b80dc2460.pdf http://uk.rs-online.com/web/search/searchBrowseAction.html?method=retrieveTfg&binCount=43&Ne=4294957561&Ntt=shaft+encoder&Ntk=I18NAll&Nr=AND%28avl%3Auk%2CsearchDiscon_uk%3AN%29&Ntx=mode%2Bmatchallpartial&N=4294561806&Nty=1 http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6928471 Read More