AUTONOMOUS ROBO SEARCH VEHICLE
"Autonomous robo search vehicle with direction and image processing"- A project doing by Pratyush kotturu final year Electronics and instrumentation engineering -Sri sai jyothi engineering college.
Sunday, February 12, 2006
Saturday, February 11, 2006
Detailed Description About Video Cameras
The video camera is a kind of transducer, which produces electrical energy from light energy. I.e., the input to the video camera is light energy and this light energy is converted into electrical signals. Video converting the complete spectrum of visible light into electrical frequencies.
There are two basic types of video cameras: monochrome (Black and White) and color. Monochrome cameras are lower in price, but color is more realistic. Both have advantages and both are desirable. By using both types we can intersperse black and while pictures with color to produce special effects. But, as far as camera features are concerned, black and while cameras can have features found in the most expensive color cameras monochrome cameras require less light than color cameras and operate with battery power. They do not have as many adjustments as color cameras, hence they are easier to use.
The video camera not only converts the light reflected from a scene into an analogous video voltage, but it also supplies the necessary sync and blanking pulses to go along with it. In short, the video camera produces the equivalent of an NTSC (National Television Standards Committee) signal, the same sort of signal that is generated by a television broadcasting station.
There is one exception, though. At the TV broadcasting station the composite video signal is loaded on to a carrier wave so as to be able to cover the distance between the station and all the receivers tuned to it. The composite video signal, recorded on videotape by the VCR accompanying the camera, can be inserted into the in-home VCR for reproduction on the television screen. But that missing factor, the carrier wave, must be introduced. This is handled by the converter section of the VCR, supplying a carrier wave whose frequency is that of either channel 3 or channel 4. Thus the composite video signal, now complete with a carrier, can be sent into the TV receiver via its antenna terminals. All that is required of the TV set is that it’s tuner be adjusted to the frequency of the carrier that is, either the frequency of channel 3 or channel 4, whichever frequency is used by the converter
A video camera can be used indoors or out. For in-home use power for operating the camera can be obtained from the AC power line by using an adaptor or the battery pack, as an additional piece of equipment. The amount of power used by a camera is least when various camera functions are manually operated. It takes battery power to make use of cameras automatic features. Thus a camera could need 7.6 watts approximately with its auto focus in the manual position. The camera used in this project work is designed to operate 12V DC.
The trend in video camera design is to produce cameras that are as lightweight and as compact as possible. The camera used in this project work is known as Board camera and the weight of this camera is less than 200 grams. The details of the Board camera collected from Internet, the details along with the picture is as follows
The above is the photograph of the actual camera used in this project work .
We may find references to cameras as being all solid state, often neglecting to add that the camera does contain a camera tube, known as pickup tube. These tubes are identified by various names selected by camera manufactures, including Saticon, Newvicon, Plumbicon, Trinicon, Univicon, Viconf, and Vidicon. Unless the camera manufacturer has its own picture tube manufacturing division, it is quite likely that the various camera tube types are supplied by the same source.
As in motion picture film cameras, the optics represent the most important part of the camera and this includes the lens or the lens system and the viewfinder.
In a film camera focal length is the distance from the optical center of the lens to the film. In a video camera it is the distance between the optical center of the lens and the target area of the picture tube. A short focal length means light inside the camera, whether film or video, has a shorter distance to travel, and so less light is lost, hence the attractiveness of keeping the focal length as short as possible. Focal length is measured in millimeters (mm) and is supplied as a range.
The operating power requirements of a video camera are approximately 6 to 8.5 watts DC. This doesn’t sound like much and it is not if the camera is being used indoors and is connected to an outlet supplying 230 volts AC, changed to 12 volts DC by a converter. But it is another matter if the camera is being operated outdoors and must rely on batteries for power. Under such conditions a camera having the smallest power requirement would be the most desirable one if this were the only feature being considered.
The video camera used in our project work is arranged over a revolving disk, naturally 12V battery pack must be provided over the disk to drive the camera.
There are two types of lenses: fixed and adjustable. A fixed lens is so-named since its focal length cannot be changed. This is the type of lens used on inexpensive film cameras. Its angle of view is constant and if you want to get closer to a scene or farther away, you can only do so by moving the camera, probably by walking with it.
The zoom lens is an adjustable type. Since its focal length is variable you can use this lens to make the angle of view wider or narrower, with in the limits of the lens. This means you can make a scene seem to come closer or farther away without moving the camera physically but just by making a lens adjustment.
However, the fact that a lens is a zoom type does not automatically make it a better quality lens. Nor is the focal length determined by whether the camera is color or monochrome. Thus you might get a black-and-white camera having a zoom lens with a greater focal length range than a color camera.
The purpose of focusing is to get as clear and sharp an image as possible. In focusing the lens is adjusted for the best image clarity. The region behind and in front of the subject that is also in focus is called depth of focus or field of focus.
Focusing can be done manually, semi automatically, and completely automatically. There is also a type of focusing, known as macro focus, in which the subject is brought very close to the camera lens.
Manual focusing, also called mechanical focusing, is an arrangement in which a focusing control, mounted on the camera can be rotated clockwise or counter clockwise. It is supplied with distances marked on the control, which is a ring positioned near the lens. With manual focusing it is necessary to adjust the focusing ring to correspond to the distance from the subject to the lens.
In the auto focus mode simply point the camera at the subject and start shooting. The focus will be continuously adjusted as the subject-to-camera distance changes, as long as the subject remains in the center of the frame.
There are certain conditions under which auto focus does not work well. You may find it difficult to get proper focus with objects that reflect strong light, such as glass or metal or objects made of black wool or black velvet, or objects that coexist far and near. For such shooting conditions set the focus auto/manual control to its manual focusing position.
Auto focusing is easy and so there is a natural tendency to rely on it and to let the camera do all the work.
SEMI AUTOMATIC FOCUSING
With this system the camera focuses on the subject. But as the subject moves it is necessary to depress a focusing button to refocus. This becomes a series of focusing steps.
As a general rule as you increase the amount to light on the subject being video graphed, the quality of the picture recorded on the tape becomes better. This is not usually a problem outdoors, except when shooting around nightfall. In the home you may need floodlights, even with window shades pulled up. It may sound like disadvantages to need to use artificial lighting, but since you have control of the light, something you do not have outdoors, you can get some dramatic and unusual effects.
You will need to experiment with lighting and you may find it helpful to buy floodlights and reflectors similar to those used in photography consider also that lighting is often best when done from front and rear. And a caution: never point your camera directly at the light since this could damage the picture tube in the camera.
The lux is the international system unit of illumination and equals one lumen per square meter. The plural of this word is luxes or luces, but is commonly ignored. Thus, the singular form, lux, is now used with all numbers, such as 1 lux, 50 lux, etc., this is industry procedure and is followed in this report. The abbreviated symbol for lux is lx.
The sensitivity of a camera is expressed in lux units and may be indicated in the cameras spec sheet. For a camera using an f1.5 lens the sensitivity could 75 lux with the cameras sensitivity switch set in its high position.
Sensitivity figures are sometimes specified as a range. Thus a camera could have sensitivity from 75 lux to 100,000-lux illumination. The camera could also have a high gain switch to permit using the camera under low light conditions. The high gain switch can be activated to prevent underexposure. Some cameras also feature a back light control to be used when the overall brightness of the scene would otherwise cause the subject to be underexposed.
DETAILS ABOUT I R SENSOR
This documentation is intended to be used as a sensor selection reference during the design and planning of collision detection and avoidance systems. The documentation contains compendium of sensor technologies that can be used to enhance collision detection and avoidance in both permanent and temporary installations and facilities.
Before the IR sensor most important aspect to be discussed is Infrared (IR)Radiation. Infrared radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of microwave radiation. The name means “below red” (from the Latin infra, “below”),red being the color of visible light of longest wavelength. Infrared radiation spans three orders of magnitude and has a wavelengths between approximately 750nm and 1mm.
Different regions in the infrared
IR is often subdivided into:
near infrared NIR , IR-A DIN,0.75-1.4 µm in wavelength,defined by the water absorption,and commaonly used in fiber optic telecommunication because of low attenuation losses in the SiO2
short wavelength (shortwave)IR SWIR,IR-B DIN 1.4-3 µm,water absorption increases significantly at 1450 nm
mid wavelength IR MWIR,IR-C DIN,also intermediate-IR(IIR),3-8 µm
long wavelength IR LWIR,IR-c DIN,8-15 µm
far infrared FIR,15-1000 µm
However,these terms are not precise,and are used differently in various studies ie.e near (0.75-5 µm)/mid(5-30 µm)./long(30-1000 µm).Especially at the telecom-wavelengths the spectrum is further subdivided into individual bands, due to limitations of detectors,amplifiers and sources. Infrared radiation is often linked to heat,since objects at room temperature or above will emit radiation mostly concentrated in the mid-infrared band.
The performance of autonomous systems executing complex tasks or solving problems is highly dependent on their perception of the environment. This means that the more precisely the systems can recognize the environment, the more complex problems can be solved. These circumstances apply to almost all automation applications, where sensors detect the environment in order t allow actions in accordance with the current situation. Despite the advancement in vision systems,active infrared sensors, are still, and especially,being used in autonomous systems, because they require less computational power and entail lower costs. They consist o emitting and receiving elements , which , in most cases, are infrared LEDs and photodiodes or phototransistors.
While the emitter illuminates the surroundings,the receiver measures the amount of light returned by, e.g., being reflected by a nearby object this work focuses on the efficient and flexible simulation of various active sensor configurations and also shows how the results can be evaluated in order to improve the recognition abilities. Being able to predict what a certain sensor system can recognize is mandatory for the design of new systems for specific applications and can help in the analysis of limitations of existing systems in executing certain tasks. In this case,simulation can be a very efficient tool, as real measurements involving a variety of sensor configurations can be very costly and time consuming.
The integration of sensors and systems is a major design consideration and is best accomplished as part of an overall system/installation/facility security screen. Although sensors are designed primarily for either interior or exterior applications, many sensors can be used in both environments. Exterior detection sensors are used to detect unauthorized entry into clear areas or isolation zones that constitute the perimeter of a protected area, a building or a fixed site facility. Interior detection sensors are used to detect penetration into a structure, movement within a structure or to provide knowledge of intruder contact with a critical or sensitive item.
Six factors typically affect the Probability of Detection (Pd) of most area surveillance (volumetric) sensors, although to varying degrees. These are the:1) amount and pattern of emitted energy; 2) size of the object; 3) distance to the object; 4) speed of the object; 5) direction of movement and 6) reflection/absorption characteristics of the energy waves by the intruder and the environment (e.g. open area, shrubbery, or wooded). Theoretically, the more definitive the energy pattern, the better. Likewise, the larger the intruder/moving object the higher the probability of detection. Similarly, the shorter the distance from the sensor to the intruder/object, and the faster the movement of the intruder/object, the higher the probability of detection. A lateral movement that is fast typically has a higher probability of detection than a slow straight-on movement. Lastly, the greater the contrast between the intruder/moving object and the overall reflection/absorption characteristics of the environment (area under surveillance), the greater the probability of detection.
Exterior sensors detect intruders crossing a particular boundary or entering a protected zone. The sensors can be placed in clear zones, e.g. open fields, around buildings or along fence lines. Exterior sensors must be resilient enough not only to withstand outdoor weather conditions, such as extreme heat, cold, dust, rain, sleet and snow, but also reliable enough to detect intrusion during such harsh environmental conditions.
Exterior sensors have a lower probability of detecting intruders and a higher false alarm rate than their interior counterparts. This is due largely to many uncontrollable factors such as: wind, rain, ice, standing water, blowing debris, random animals and human activity, as well as other sources to include electronic interference. These factors often require the use of two or more sensors to ensure an effective intrusion detection screen.
Interior sensors are used to detect intrusion into a building or facility or a specified area inside a building or facility. Many of these sensors are designed for indoor use only, and should not be exposed to weather elements. Interior sensors perform one of three functions: (1) detection of an intruder approaching or penetrating a secured boundary, such as a door, wall, roof, floor, vent or window, (2) detection of an intruder moving within a secured area, such as a room or hallway and, (3) detection of an intruder moving, lifting, or touching a particular object. Interior sensors are also susceptible to false and nuisance alarms, however not to the extent of their exterior counterparts. This is due to the more controlled nature of the environment in which the sensors are employed.
With the advent of modern day electronics, the flexibility to integrate a variety of equipment and capabilities greatly enhances the potential to design an collision avoidence and detection system to meet specific needs. The main elements of an collision avoidence and detection system include: a) the collision Detection Sensor(s), b) the Alarm Processor, c) the detection/avoidence Monitoring Station, and d) the communications structure that connects these elements and connects the system to the reaction elements. However, all systems also include people and procedures, both of which are of equal and possibly greater importance than the individual technology aspects of the system. In order to effectively utilize an installed security system, personnel are required to operate, monitor and maintain the system, while an equally professional team is needed to assess and respond to possible collisions.Collisions detection sensors discussed in this Handbook have been designed to provide collision detection and include sensors for use in the ground, open areas, inside rooms and buildings, doors and windows. They can be used as standalone devices or in conjunction with other sensors to enhance the probability of detection. In the majority of applications, intrusion detection sensors are used in conjunction with a set of physical barriers and personnel/vehicles access control systems. Determining which sensor(s) are to be employed begins with a determination of what has to be protected, its current vulnerabilities, and the potential threat. All of these factors are elements of a Risk Assessment, which is the first set in the design process.
In the process of evaluating individual collision detection sensors, there are at least three performance characteristics which should be considered: Probability of Detection (PD), False Alarm Rate (FAR), and Vulnerability to Defeat (i.e. typical measures used to defeat or circumvent the sensor). A major goal of the security planner is to field an integrated collision Detection System (ICS), which exhibits a low FAR and a high PD and is not susceptible to defeat. Probability of Detection provides an indication of sensor performance in detecting movement within a zone covered by the sensor. Probability of detection involves not only the characteristics of the sensor, but also the environment, the method of installation and adjustment, and the assumed behavior of an intruder. False Alarm Rate indicates the expected rate of occurrence of alarms high is not attributable to intrusion activity. For purposes of this Handbook, "false alarms" and "nuisance alarms" are included under the overall term "False Alarm Rate", although technically, there is a distinction between the two terms. A nuisance alarm is an alarm event which the reason is known or suspected (e.g. animal movement/electric disturbance) was probably not caused by an intruder. A false alarm is an alarm when the cause is unknown and an collision is therefore possible, but a determination after the fact indicates no collision was attempted. However, since the cause of most alarms (both nuisance/false) usually cannot be assessed immediately, all must be responded to as if there is a valid intrusion attempt.
Vulnerability to Defeat is another measure of the effectiveness of sensors. Since there is presently no single sensor which can reliably detect all collisions, and still have an acceptably low FAR, the potential for "defeat" can be reduced by designing sensor coverage using multiple units of the same sensor, and/or including more than one type of sensor, to provide overlapping of the coverage area and mutual protection for each sensor.
From a technology perspective, the integration of sensors into a coherent security system has become relatively easy. Typically, most sensor systems have an alarm relay, from points a, b or c, and may have an additional relay to indicate a tamper condition. This relay is connected to field panels via four wires, two for the alarm relay and two for the tamper relay, or two wires, with a resistive network installed to differentiate between an alarm and tamper condition. Most monitoring systems will also provide a means of monitoring the status of the wiring to each device. This is called line supervision. This monitoring of the wiring provides the user with additional security by indicating if circuits have been cut or bypassed.
Additionally, different sensors can be integrated to reduce false alarm rates, and/or increase the probability of intrusion detection. Sensor alarm and tamper circuits can be joined together by installing a logic "and" circuit. This "and" system then requires multiple sensors to indicate an alarm condition prior to the field unit sending an alarm indication. Usage of the logic "and" circuit can reduce false alarm rates but it may decrease the probability of detection because two or more sensors are required to detect an alarm condition prior to initiating an alarm.
Communications between the front-end computer and the field elements (sensors, processors) usually employ a variety of standard communications protocols. RS-485, RS-232, Frequency Shift Keying (FSK), and Dual Tone Multi Frequency (DTMF) dial are the most common, although occasionally manufacturers will use their own proprietary communications protocol which can limit the option for future upgrades and additions. In order to reduce the tasks required to be handled by the computer, some systems require a preprocessing unit located between the computer and the field processing elements. This preprocessor acts as the communications coordinator to "talk" to the field elements thus relieving the computer of these responsibilities.
Regardless of how well designed and installed, all collision detection systems are vulnerable to power losses, and many do not have an automatic restart capability without human intervention. Potential intruders are aware of this vulnerability and may seek to "cut" power if they cannot circumvent the system via other means. It is critical that all elements of the system have power backups incorporated into the design and operation to guarantee uninterrupted integrity of the sensor field, alarm reporting, situation assessment, and response force reaction.
The costs of an Collision Detection System are easy to underestimate. Sensor manufacturers often quote a cost per meter, cost per protected volume, for the sensor system. Often this figure is representative of the hardware cost only, and does not include the costs of installation, any associated construction or maintenance. Normally, the costs associated with procuring the sensor components are outweighed by the costs associated with acquiring and installing the assessment and alarm reporting systems.
Most sensors have been designed with a specific application in mind. The environment categorizes these applications where they are most commonly employed. The two basic environments or categories are Exterior and Interior. Each of the two basic categories has a number of sub-sets, such as fence, door, window, hallway, and room. The first two of the following set of graphics show a "family tree" illustration of the sensors most applicable to the these two environments (exterior/interior). As mentioned previously, some of the technologies can be used in both environments and consequently are shown on both graphics.
BLOCKDIAGRAM AND ITS BRIEF DESCRIPTION - Part 3
The output of the video camera is fed to transmitter as modulating waves and these waves are super imposed over the carrier and transmitted as modulated waves. The carrier is designed for transmitting the picture details. At the receiving end, a small television set of 4” screen is used.
The transmitter circuit generates a continuous frequency of 100MHz approximately, which is used to form a permanent link between the transmitter and receiver, and this is known as carrier frequency. The output of video camera is fed to this carrier input as a modulating wave. This is a frequency modulated radio transmitter. The radiating power of the transmitter is less than 20 mw, so that the range between transmitter and receiver can be less than 25 feet. The detailed description is provided in the next chapter. For the demonstration purpose either black & white television set or computer is used, the block diagram of this simple TV along with its brief description is provided in this chapter. The details are as followed.
The block diagram of simplified block & white TV receiver shown below
In above block diagram, the receiving antenna intercepts radiated RF signals and the turner selects desired channels frequency band and converts it to common IF band of frequencies. The receiver employs two or three stages of IF amplifiers. The output from the last IF stage is de-modulated to recover the video signal. This signal that carries picture information is amplified and coupled to the picture tube, which converts the electrical signal back into picture elements of the same degree of black and white. The picture tube is very similar to the cathode-ray tube used in an oscilloscope. The glass envelope contains and electron-gun structure that produces a beam of electrons aimed at the fluorescent screen. When the electron beam strikes the screen. Light is emitted. A pair of deflecting coils mounted on the neck of picture tube in the same way as the beam of camera tube scans the target plate deflects the beam. The amplitudes of currents in the horizontal and vertical deflecting coils are so adjusted that the entire screen called raster, gets illuminated because of the fast rate of scanning.
The video signal is fed to the grid or cathode of picture tube. When the varying signal voltage makes the control grid less negative, the beam current is increased, making the spot of light on the screen brighter. More negative grid voltage reduces brightness. If the grid voltage is negative enough to cut-off the electron beam current at the picture tube, there will be no light. This state corresponds to black. Thus the video signal illuminates the fluorescent screen from white to black through various shades of grey depending on its amplitude at any instant. This corresponds to brightness changes encountered by the electron beam of the camera tube while scanning picture details element by element. The rate at which the spot of light moves is so fast that the eye is unable to follow it and so a complete picture is seen because of storage capability of the human eye.
The path of sound signals is common with the picture signal from antenna to video detector section of the receiver. Here the two signals are separated and fed to their respective channels. The frequency modulated audio signal is demodulated after at least one stage of amplification. The audio output from the FM detector is given due amplification before feeding it to the loudspeaker.
BLOCKDIAGRAM AND ITS BRIEF DESCRIPTION - Part 2
The main block in the Block diagram is Obstacle Sensing circuit Designed with IR Sensors. The obstacle sensing block is designed with LM567 IC, this is a tone decoder IC, also it generates tone frequency. For identifying the obstacles 3 sets of sensors are used with three different 567 IC’s, similarly for detecting the pit or valleys another set of sensors are used. All these four sets of sensors are arranged at front side of the vehicle. Each sensing block is designed with two IR LEDs , Namely transmitting LED and receiving LED. Both the sensors are arranged side by side with in half-inch distance. The tone generator part of the IC is configured as astable mode of operation, which produces a perfect square wave of 10 KHz approximately and it is amplified using a transistor. The amplified signal is radiated through the transmitting IR LED. The signal delivered by the IR LED transmits in a line like LASER beam, when ever this signal is interrupted by an object, the radiating signal will be spread in the air because of the object, this signal is tracked by the another IR LED which is called as optical signal sensor. On receipt of optical signal, the tone decoder part of the IC detects the signal through the optical sensor and generates a high signal for the micro controller. Like wise the controller is getting signals from the four sensing blocks, according to the received information from the sensors, the controller controls the stepper motors in all directions.
Especially the new era of Robotic field mainly deals with fuzzy logics and artificial intelligence. That means, these gadgets should be in a position to identify the obstacle before it and do some appropriate calculation to overturn. This project also uses this theory. The actual theory is “Collision avoidance theory”. This theory was developed by using range finding sensors. As this is a prototype we are least bother about the range . When object obstacles in that range the IR beam will be reflected back and the Receiver will detects it. Here the receiver is connected to microcontroller. Infrared reflex sensors are most typically used for distance measurements by transmitting a modulated infrared light pulse and measuring the intensity of the reflection from obstacles nearby. In practice, infrared sensors can only be used for detection of objects, not for range measurements.
The received information from the optical sensors fed to micro-controller, for storing as well as controlling stepper motors. Micro-controller unit is constructed with ATMEL 89C51 Micro-controller chip. The ATMEL AT89C51 is a low power, higher performance CMOS 8-bit microcomputer with 4K bytes of flash programmable and erasable read only memory (PEROM). Its high-density non-volatile memory compatible with standard MCS-51 instruction set makes it a powerful controller that provides highly flexible and cost effective solution to control applications.
Micro-controller works according to the program written in it. Most micro-controllers today are based on the Harward architecture, which clearly defined the four basic components required for an embedded system. These include a CPU core, memory for the program (ROM or Flash memory), memory for data (RAM), one or more timers (customisable ones and watchdog timers), as well as I/O lines to communicate with external peripherals and complementary resources — all this in a single integrated circuit. A microcontroller differs from a general-purpose CPU chip in that the former generally is quite easy to make into a working computer, with a minimum of external support chips. The idea is that the microcontroller will be placed in the device to control, hooked up to power and any information it needs, and that's that.
A traditional microprocessor won't allow you to do this. It requires all of these tasks to be handled by other chips. For example, some number of RAM memory chips must be added. The amount of memory provided is more flexible in the traditional approach, but at least a few external memory chips must be provided, and additionally requires that many connections must be made to pass the data back and forth to them.
For instance, a typical microcontroller will have a built in clock generator and a small amount of RAM and ROM (or EPROM or EEPROM), meaning that to make it work, all that is needed is some control software and a timing crystal (though some even have internal RC clocks). Micro-controllers will also usually have a variety of input/output devices, such as analog-to-digital converters, timers, UARTs or specialized serial communications interfaces like I²C, Serial Peripheral Interface and Controller Area Network. Often these integrated devices can be controlled by specialized processor instructions.
Originally, micro-controllers were only programmed in assembly language, or later in C code. Recent micro-controllers integrated with on-chip debug circuit accessed by In-circuit emulator via JTAG (Joint Text Action Group) enables a programmer to debug the software of an embedded system with a debugger.
More recently, however, some micro-controllers have begun to include a built-in high-level programming language interpreter for greater ease of use. BASIC is a common choice, and is used in the popular BASIC Stamp MCUs (Master Control Unit). Micro-controllers trade away speed and flexibility to gain ease of equipment design and low cost. There's only so much room on the chip to include functionality, so for every I/O device or memory increase the microcontroller includes, some other circuitry has to be removed. Finally, it must be mentioned that some microcontroller architectures are available from many different vendors in so many varieties that they could rightly belong to a category of their own. Chief among these are the 8051 family.
Stepper Motor Drive Circuit
The output of the microcontroller is used to drive the stepper motor through drive circuit, and the motor used in this project work is having four windings, therefore the controller drives the motor through four outputs. The stepper motor windings are energized one after another in a sequence according to the code produced by the controller through motor drive circuit. This motor rotates in step wise and the step angle is 1.80. The speed of the motor can be varied by varying the pulse rate. The pulses are produced by the controller can be controlled through the program by which motor speed can be varied. The stepper motor used in this project work is capable to drive up to 5kg load.
ABOUT STEPPER MOTOR
The stepper Motor used in this project work is indigenous one,which is an easy and reliable device to convert electrical energy into mechanical motion. It does not have the accuracy or the response speed of a DC motor. It is, however, utilized in many applications such as disk drives, printers, recorders, plotters, copiers, scanners, fax machines, robots, machine tools, automobiles, and medical equipment for its ease of use. Since each input change causes exactly one step rotation, a stepper motor may be operated in an open loop system. Typical step angles are 0.9o, 1.8o, 3.6o, 7.5o, 15o, and 30o.
Stepper motors are frequently applied to problems that require precision positioning without rotor position feedback. The most common stepper motors have multiple field windings and a permanent magnet rotor. The rotor is made to rotate by means of electronically commutating (switching) the current in the field windings. These motors are design to operate indefinitely with DC voltage applied to one or more fields in order to hold the rotor in a fixed position.
The rotor will rotate in discrete steps when the fields are energized in a specific sequence. Depending upon the sequence, the rotor may rotate clockwise (CW) or counter clockwise (CCW). Stepper motors are designed to rotate a fixed number of degrees with each step. A 1.8-degree stepper motor requires 200 steps for the rotor to make a full revolution.
Stepper motors have multiple stepping modes, full stepping, half-stepping and micro stepping. During full stepping, the rotor rotates the designed angular distance (1.8 degrees for example) each step. To rotate the motor, only four distinct input combinations or states are required to rotate the rotor. Repeating the sequence of states in the proper order results in what appears to be a continuously rotating rotor.
Half stepping is achieved on the same stepper motor by using an 8-state sequence. The rotor now rotates only half the designed angular rotation per half step. For a 1.8-degree stepper motor, the rotor will rotate 0.9 degrees for each half-step thus requiring 400 half steps for the rotor to make a full revolution. The chief advantage of half stepping is higher position control precision. Micro stepping requires extremely complex field current switching and allows an infinitely small rotation. Micro stepping is beyond the scope of this experiment. (For more information on stepper motor operations, read chapter – 11).
There are inherent problems with stepper motors that designers must be aware of to properly apply them. Due to rotor mass and finite energy in the field, stepper motors can only step so fast before the rotor will begin to skip steps and eventually stop completely. The primary cause of this high-speed stall is reduced field current at high speeds. This reduced field current is caused by back EMF generated by the turning rotor. One way to increase the top speed is to increase the field current at higher speeds. Elaborate field current control schemes have been devised to increase the current at high speeds without melting down the motor at slow speeds.
TRIGGER CIRCUIT BLOCK
This block is designed with 555 timer IC and an LDR is used as a light sensing device, the same is wired with timer IC. The idea of building this block is to energize the vehicle head-lamps automatically, whenever the natural light disappears. Two lamps are provided at the front side of the vehicle and these lamps energized through the relay contact.
The timer IC configured as Schmitt trigger mode of operation, triggers at 1/3Vcc. When the LDR is exposed to the light intensity, the resistance of the LDR will become less than 1K and makes the voltage at comparator input less than 1/3Vcc which in turn triggers the timer IC and generates a high signal at its output (Pin No.3). When the IC is triggered relay will be energized automatically, this relay contact is used to provide supply to the lamps. For this purpose normally closed contact is used, when the relay energized closed contact becomes open and breaks the supply to the lamps. When the natural light disappears, the resistance of the LDR will become more than 500K, which in turn comparator input voltage increases more 2/3Vcc, there by the relay remains in de-energized condition. When the relay remains in de-energized condition, normally closed contact remains in closed condition and provides supply to the lamps. Hence these lamps energized automatically when the natural light disappears.
Wednesday, February 08, 2006
4.BREIF DESCRIPTION ABOUT VARIOUS TYPES OF AUTONOMOUS VEHICLES
5.BLOCKDIAGRAM AND ITS BRIEF DESCRIPTION
7.CIRCUIT DIAGRAM WITH COMPONENT VALUES
8.DETAILS ABOUT IR SENSORS
9.DETAILED DESCRIPTION ABOUT VIDEO CAMERAS
10.DETAILS ABOUT MICROCONTROLLERS
11.DETAILED DESCRIPTION ABOUT STEPPER MOTORS
12.DETAILED DESCRIPTION ABOUT WIRELSS COMMUNICATION
16.CONCLUSIONS AND REFERENCES
Wednesday, January 04, 2006
BRIEF DESCRIPTION ABOUT VARIOUS TYPES OF AUTONOMOUS VEHICLES
Autonomous land vehicles have been an intense area of research and development for the last decades. An excellent introduction and summary of the state-of-the-art is given in this chapter. In this section we report on successful projects in application areas that relate to the proposed forest based system we are aiming at.
In our search for research related to our proposed development project, we found many research articles related to Ground Navigation Vehicles from the different people from all over the world, these valuable research articles are found in web sites. Only one project with similar goals has been found: The ROFOR project run by Anibal Ollero, University of Seville, Spain. Not much information are to be found on the project, which has been going on since 1997. The objective of the project is the design, development and implementation of a control system for a forest processor machine (felling, cutting and to heap up). The project also includes the design of the robot arm and vehicle control system. The latest information (http://www.esi.us.es/AICIA/2000/inge_e.html) to be found reports:
“In this project a forest processing machine has been partially automated. thus, autonomous and tele-operated functions have been combined in the control system. A distributed control system has been developed and implemented in the machine. The system can be implemented by using both cable and wireless communications between the operator cabin and a PLC in the processing unit. The tele-operation system integrates the joystick and other devices for machine operation, and a graphical interface for the visualization of the processing functions during operation. The system also includes functions for machine diagnosis, operator and machine production control, and communications with a control centre using GSM. The tasks during 2000 have been mainly devoted to debugging, integration of the system, and testing.”
Path tracking methods aim at keeping the vehicle approximately on a pre defined path, and bring it back to the path when unacceptable deviations occur. Various approaches for this task have been presented for AGV usage.
The main goal of the path tracking vehicle is to present a working solution for autonomous path tracking navigation, to be implemented in a vehicle for operation in forest terrains. The Autonomous Ground Vehicle (AGV) should operate in two modes: Path Recording, and Path Tracking. In the Path Recording mode, a human driver drives along the chosen path, recorded in the computer memory. In the Path Tracking mode, the computer assumes control over propulsion and steering. The vehicle then automatically travels along a memorized path. The operation has to account for unplanned deviations from the path, caused by imperfect sensing of position, and also by the vehicle sliding and jumping along the path. Another important part involves detection of new obstacles appearing on the path. In some cases the system should stop the vehicle and alert the human operator, who should be given the option of manually correcting the vehicle position, or giving the system the green light to go ahead along the original path.
A lot of research and development with autonomous vehicles for use in agriculture has been conducted the last decades. The primary agricultural activities addressed have been harvesting, mowing and applications of pesticides. O’Connor et al. at Stanford University developed a system for agricultural equipment that follows a preplanned path. A four-antenna system with Differential GPS (DGPS) provided a heading accuracy of 0.1 degrees and offset accuracy of 2.5 cm. A row-following system for harvesting in cauliflower fields was developed by Marchant et al. At Carnegie-Mellon Robotics Institute an autonomous vehicle for cutting forage using vision-based perception on the cut and uncut regions of crop was developed . The developed system used DGPS combined with wheel encoders and gyro data to compute estimates of both position and attitude. The vision sensing included functions for vehicle guidance (row-following), “end-of-row” detection, correction of illumination due to shadows and obstacle detection. An adaptive Fisher discriminant classifier was used to segment the images in cut/uncut regions by pixel wise classification based on RGB values. The obstacle detection was implemented with similar techniques where each pixel was classified as “normal” or “abnormal” relative to a training image. The probabilities for a pixel belonging to the probability distributions constructed from the training image were used to decide if the pixel belongs to an obstacle or not. Regions with a large number of such pixels were identified as obstacles. Three onboard computers were used, one for image analysis, one for control and one for task management. A pure pursuit algorithm is used for the path tracking task.
Automatic digging is an active field of research. One approach is to let a human operator select the digging point and to let the autonomous system take over to complete the dig. Another, more difficult, approach is to use active sensing and automatically select the dig point. Stentz et al. [Sten01] developed a fully autonomous 25-ton hydraulic excavator for loading a truck with soft material such as dirt. The machine uses laser rangefinders to recognize the truck, detect obstacles and controlling the digging and loading process. The scanners scan vertically and are mounted on a pan table swept left and right, thereby covering all space of interest. According to the authors, the excavator is a fully operational prototype but is “unlikely to appear commercially as such, at least not initially”. It does not work under all weather conditions. The system is able to detect most obstacles, but “could not be left alone to work a complete shift without incident”. One suggested way to use it commercially is to demand a human operator to remain on the machine to monitor for safety, but to let the computer take over the actual digging/loading. Alternatively, a remote operator could monitor the work, check plans for repositioning and manually make corrections when necessary.
Mining is an important application domain for autonomous off-road vehicles. Stentz et al. [StOl99] report on a development of two mining aids: a system to measure and control forward motion of a continuous miner, and a system to measure and control the machine’s heading. Both measures are important to ensure high cutting quality of the coal. The heading task is solved by Kalman fusion of a fiber-optic gyro with a laser/camera system. The motion is computed by correlating stereo images of the roof of the mine, taken with a short delay. A recent project, reported in [ACFR01], use a scanning laser to detect guideposts located on the side of the haul road. The system aims at determining safe manual driving control of large haulage vehicles.
The final target machine will be a standard forest machine, configured for the automatic computer control and for the need of sensors of various kinds. This is the most common approach to AGV design: simply automate an existing manual vehicle. To simplify things, many manufacturers provide an “automation option” on manual vehicles. E.g. Kalmar Industries (of Finland) who manufactures container straddle carriers and forestry logging equipment. Komatsu-Haulpack (large mining trucks and excavators) and Vost-alpine (underground mining equipment) also offer automation options for their products. However, in our case it will be necessary to install an automation interface since the plan is to use a standard forest machine from Partek Forest AB.
Some parts of the project can be run without access to a real forest machine. For this purpose a development robot should be purchased and installed in a “miniature forest” inside or outside the research premises. Some parts, such as cameras or laser detectors, have to be mounted on the real target machine that can provide a realistic environment for development and testing. Of course, the final complete system will be also installed on a real forest machine and tested under real conditions.
The project will benefit from an additional platform in development and testing, for the following reasons:
It will increase the productivity of the development work since a full sized forest machine will need considerably more effort to access and use.
The modifications of the forest machine are not trivial and can be performed in parallel with the development work.
A lot of hardware and software will have to be purchased, learned and tested as part of the project. This work is most efficiently done in-doors, but need a reasonably realistic substitute for the eventual target machine In addition to serving the goals of this project, a development robot will be useful since the research team will learn both hardware and software relevant for many future projects. The equipment can also be used for teaching robotics, aim at developing education in autonomous systems for off-road use. The approach with a small-scaled robot is encouraged in [HaCa01], and also considered as a better alternative than computer simulation. After developing and testing on a small-scale robot, the systems can be transferred to the target vehicle, requiring much less modification than a simulated counterpart.
Two main alternatives for a development robot exist: buying standard equipment or having a custom designed robot constructed and manufactured. The latter alternative has the advantage of providing a platform that can mimic certain characteristics of the real forest machine that can be of value for the development work. This would for example be the construction of the steering device. The controller for a vehicle with articulated joint steering will differ significantly from the controller in a vehicle with a differential drive or with Ackerman (“carlike”) steering. Other important characteristic that is lost in a standard robot is the size aspects. The placement of sensors such as cameras or laser range scanners affects the behavior of the autonomous vehicle to a large extent. However, even a custom designed robot will differ significantly from the final target machine. Extensive work will therefore have to be performed on the target machine, regardless of the choice of development robot. The advantage with buying a standard robot is first of all that it is available and works immediately (in a reasonably ideal world).
The search vehicle designed with stepper motors is quite suitable for the defense application. Generally these kinds of vehicles are used in jungles for searching the anti-social elements. The system can be called as autonomous, because the vehicle itself detecting objects and according to the position of the object the vehicle takes diversion either right turn or left turn automatically. Some times the vehicle travels in reverse direction also, this happens when the vehicle finds a huge objects like trees, rocks etc., infrared sensors are used and they are arranged at front side of the vehicle.
For this purpose three sets of sensors are fed and each set contains two IR sensors. Two sets of sensors are arranged at left and right sides of the vehicle and the third set is arranged at middle of the vehicle. From each set, IR signal is delivered through one sensor like a laser beam, whenever the object interrupts the beam, the signal is reflected and this reflected signal is detected by another sensor. The outputs of all the three sensors are fed to Micro-controller, and according to the interrupted signals received by the sensors, the controller circuit drives the stepper Motors. These Motors drives the vehicle in different directions. For example, whenever the right sensors are interrupted, the vehicle takes left turn and moves in forward direction. Similarly if the left sensor is interrupted, vehicle takes right turn. Whenever the middle sensor is interrupted, vehicle moves in reverse direction up to certain distance and takes right or left turn.
The vehicle is called as search vehicle, because this vehicle is equipped with wireless video camera for collecting and transmitting the video images to the nearest monitoring station. At the monitoring station a small television set is used, so that presence of a person in the forest can be identified at monitoring station
In addition to the above an LDR is also used as a light-sensing device, and it is interfaced with the trigger circuit. The idea of using this circuit is to energize the vehicle headlamps automatically whenever the natural light disappears, with the help of this auto lighting system, during the nighttime also images can be transmitted. The output of the trigger circuit is used to drive the relay and this relay contact is used to energize the headlamps. Provision is made such that during the day time these lights remains in off condition.
Autonomous robo search vehicle with direction and image mapping
The project mainly deas with collission detection theory.Mainly this theory was stated from carneige million university.this mainly stated with pit sensors and IR range finders.
This project contains 3 sets of IR range finders.they are placed in front of the vehicle,such that all the proximity spcae will be coverd and this states the entire vehicle is fullly accurate and precise
The synopsis will be shown in the next blog.....