Path Planning Strategy For Line Follower Computer Science Essay

Path Planning Strategy For Line Follower Computer Science Essay This paper presents the development of a line follower wheeled mobile robot. In this project, ARM cortex-3 based microcontroller is chosen as the main controller to react towards the data received from infrared line sensors to give fast, smooth, accurate and safe movement in partially structured environment. A dynamic PID control algorithm has been proposed to improve the navigation reliability of the wheeled mobile robot which uses differential drive locomotion system. The experimental results show that the dynamic PID algorithm can be performed under the system real-time requirements. Keywords embedded system, wheeled mobile robot, PID control algorithm. Introduction Embedded system includes many areas of knowledge, microcontroller hardware and software, interfacing technologies, automatic control theory, and sensor technologies etc. To speed up the learning process and motivate students to learn actively, the project-based learning approach may be applied in the embedded system design laboratory [1-4]. The low-cost wheeled mobile robot building, which is proposed in this paper, serves as a good example on which students can learn embedded system design skills. It covers not only common embedded system peripherals, but also energy control and real-time control firmware implementation. The process of the construction of wheeled mobile robot can give students the idea that hardware circuits and software algorithms are both mandatory for a successful embedded system design. The competition between student groups in the racing contest can also encourage them to explore in depth the skills acquired in this laboratory as well as give them lots of fun [ 5-7]. The remainder of this paper is organized as follows: The line follower robot structure and architecture issues and challenges along with their technical issues and problems are discussed in section 2. Programming details will be explained in section 3. Section 4 describes the integration of the complete system. LÄ ±ne follower wheeled MobÄ ±le Robot structure Generally, the line follower robot is one of the self-acting wheeled mobile mechanisms that follow a line drawn on the floor. The route can be a visible black line on a white surface or vice versa. The simple operations of the wheeled mobile line follower robot are shown below. Taking the line position data with optical sensors attached at the front end of the mobile robot. Most are using more than a few numbers of IR photo-reflectors. Therefore, the line sensing procedure needs high resolution and high robustness. Steering the wheeled mobile robot to track the line with any direction-finding mechanism. This is just a servo maneuver; actually, any phase recompense will be required to become stable following motion by applying digital PID filter or any similar servo algorithm. Monitoring the speed according to the path complaint. The speed is restricted during passing a turn due to the friction of the tire with the floor. From actually building the robot platform, to setting up, programming, and hardware or software fine tuning, everything needs to be taken into account when building a differential wheeled mobile robot. A mobile robot can be considered fundamentally as a combination of five main portions and subsystems. Chassis and body. Sensors and signal processing circuits. Microcontroller and interface circuits. Motor drivers Actuators (Motors and wheels) The Chassis and Body The Chassis would be the first part of a robots body. It is designed to handle all of the other components, transmission mechanisms, electronics and battery. It needs to be sufficiently large and provide adequate fixtures to furnish all necessary parts, as well as sturdy enough to cope with the weight of the parts along with additional loads which can appear in dynamic conditions such as vibrations, shocks or chassis torsion and actuators torque. There are some good materials for designing robots such as plastic, aluminum and carbon-composites. We must pay attention to the resistance, weight and mechanical ability for choosing one of them. In the designed robot, printed circuit board (PCB) has been used for chassis because of its lightweight and being strong enough for robot project. All components can be installed on the PCB to minimize the weight. It is noted that the performance is much more valuable than other issues. Sensors and Signal Processing Circuit Line follower robot uses Infrared Ray (IR) sensors to find the path and direction. IR sensors include an infrared transmitter and infrared receiver pair. IR sensors are often used to identify white and black surfaces. White surfaces effectively reflect well, but black surfaces reflect poorly. Hence, the distance between sensors and ground surface is important, and it is more valuable that how we put sensors near to each other. The distance between sensors and ground surface must be 2 to 10 mm, and the distance between each sensor is dependent on the line width. In the designed robot, we have used eight sensors, and they have a suitable distance between each other. If the line width is narrow, the distance between sensors must be reduced; otherwise, while curving the line, the robot will not be turned on time. Generally, the received signals from the sensors are analog and must be converted to the digital form. Therefore, the designed signal processing circuit can send the sensors signals to the microcontroller directly. Microcontroller We have used the TI Stellaris microcontroller LM3S811 in robot project. The LM3S811 microcontroller has a Reduced Instruction Set Coding (RISC) core. Internal oscillators, timers, UART, USB, SPI, pull-up resistors, pulse width modulation, ADC, analog comparator and watch-dog timers are some of the features [8]. With on-chip in-system programmable Flash and SRAM, the LM3S811 is a perfect choice in order to optimize cost. Motor Drivers A well-known and suitable motor driver is IC L298 which can be used to control two motors. It is a high voltage, high-current dual full-bridge driver designed to accept standard TTL logic levels and drive inductive loads such as DC and stepping motors [9]. Two enable inputs are provided to enable or disable the device independently of the input signals. L298 has 2 amperes per channel current capacity and it can support up to 45 volts for outputting. Moreover, L298 works well up to 16 volts without any heat sink. The Actuators (Motors and Wheels) There are many kinds of motors and wheels. Our choice depends on the robot function, power, speed, and precision. Actually, it is better to use gearbox motors instead of common DC motors because it has gears and an axle and its speed does not change towards the top of a hill or downhill. Motors are rated to operate at 1700 rpm at 7 volt nominal voltage. It is better to use wheels for line follower robots, instead of a tank system. We can use three wheels. Two of them are joined to the motors and installed at the rear of the robot and the other wheel is free and installed in front of the robot as a passive caster. To get better maneuver, robot uses two motors and two wheels on the rear and a free wheel on the front. The power supply is 7.6 V with a regulator. The designed robot has eight infrared sensors on the front bottom for detecting the line. Arm based microcontroller Stellaris and driver L298 were used to control direction and speed of motors. General view of the line follower robot that we built is shown in Fig. 1. The robot is controlled by the microcontroller. It performs the change in the motor direction by sending an appropriate signal to the driver IC according to the received signals from the sensors. Real Time Task Scheduling We built a light-weighted and high-speed robot because points are awarded based upon the distance covered and the speed of the overall robot. Therefore, we used two high speed motors and a highly sensitive signal conditioning circuit. The body weight and wheels radius have effects on the speed, too. The weight of the designed robot is around 300 gr. and it could be lighter. The photograph of the top and bottom views of the designed robot is shown in Fig. 1. The microcontroller sends instructions to the driver after processing the data received from sensors. The driver powers the motors according to the inputs. Actually the driver supplies positive voltage to one of the motor pins and negative voltage to the other. There are five states of movement: To move forward; both of the motors are turned on and rotate forward simultaneously. To move left; the right motor is turned on and the left motor is turned off. To move right; the left motor is turned on and the right motor is turned off. To move left fast; the right motor rotates forward and the left motor rotates backward. To move right fast; the left motor rotates forward and the right motor rotates backward. Most embedded system applications need to react to the inputs or environment changes in real time, which means that the accuracy of computations is as important as their timelines. Furthermore, digital control algorithms need a fixed sampling time interval for measuring inputs and delivering output commands. Therefore, the idea of applying interrupts for task scheduling is introduced in this work. IMAG0388 (a) IMAG0392 (b) Figure 1 Images show (a) top, (b) bottom views of the built line follower robot. The Quadratic Line-Detection Algorithm A better way of detecting the line position, compared to the other simple line-following robots, by using a quadratic interpolation technique is introduced. Eight reflective optical sensors were used, and the coordinate of the leftmost sensor was 0. To find out the correct position of the black line, we had to locate three consecutive sensors with higher output readings than the other five sensors as shown in Fig. 2. Assume that the coordinates of these 3 sensors are x1, x1+1, and x1+2, and the true shape of the sensor output values are in the range of [x1, x1+2] which can be approximated by a quadratic curve. One can then find the following relationships between the coordinates of the sensors and the output values: (1) (2) (3) The coordinate value, at which the output value of the quadratic curve is the maximum, is considered as the true position of the line. By using the basic calculus, one would know that the coordinate value is: (4) (5) (6) It is assumed that the coordinate for the center position of the line-following robot is 0. Therefore, the error e between the line position and the center position of the robot is e â‚ ¬Ã‚ ½Ã¢â€š ¬Ã‚  0â‚ ¬Ã‚ ­Ã¢â€š ¬Ã‚  x â‚ ¬Ã‚ ½Ã¢â€š ¬Ã‚  Ã¢â€š ¬Ã‚ ­x (7) Figure 2 The line detection algorithm via quadratic interpolation. PID Tracking Control Algorithm The popular proportional-integral-derivative (PID) controller was introduced in this project to make the robot follow the racing track. The error between the center of the sensors and the track to be followed was then processed by the PID controller to generate velocity commands for the right and left wheels. First, the controller calculates the current position and then calculates the error established on the current situation. It will then send commands the motors to give a rigid turn, if the error is extraordinary or a minor turn, if the error is small. Basically, the amount of the turn given will be proportional to the error. Of course this is a consequence of the proportional control. Even after this, if the error does not decline approximately to zero, the controller will then growth the degree of the turn further and further over time till the robot centers over the line. This is the result of the integral control. In the process of centering over the line, the robot may overshoot the target position and move to the other side of the line where the above process is followed again. Thus, the robot may keep oscillating about the line in order to center over the line. To reduce the oscillating effect over time, the derivative control is used. The proportional term is only a gain ampli fier, and the derivative term is applied in order to improve the response to disturbance, and also to compensate for phase lag at the controlled object. Pseudo Code for the PID Controller; Kp = 10 Ki = 1 Kd = 100 offset = 45 ! Initialize the variables Tp = 50 integral = 0 ! the place where integral value will be stored lastError = 0 ! place where last error value will be stored derivative = 0 ! place where derivative value will be stored Loop forever LightValue = read sensors ! read sensors. error = -x ! calculate the error using equation (7). integral = integral + error ! calculate the integral derivative = error lastError ! calculate the derivative Turn = Kp*error + Ki*integral + Kd*derivative powerA = Tp + Turn ! power level for motor A powerB = Tp Turn ! power level for motor B MOTOR A direction=forward power=PowerA MOTOR B direction=forward power=PowerB lastError = error ! save the current error end loop forever ! do it again. PID controller requires the Kp, Ki and Kd factors to be set to match wheeled line follower robots characteristics and these values depends on robot structures, actuators, sensors and other electronic components characteristics. There is no equation given in the literature to calculate Kp, Ki and Kd factors. It requires experimental trial and error technique until you get the favorite behavior. We defined these factors according to following guidelines; Start with low speed and setting values of Kp, Ki and Kd to 0. Then, try setting Kp to a value of 1 and observe the robot. The goal is to get the robot to follow the line even if it is extremely wobbly. If the robot overshoots and misses the line, decrease the value of Kp. If the robot cannot navigate a turn or seems listless, increment the Kp value with small steps. Once the mobile robot is able to follow the path, set Kd value to 1 and then try growing this value until you see less shake. Once the robot is fairly stable at following the line, assign a value of .5 to 1.0 to Ki. If the Ki value is extraordinary, the robot will shake left and right rapidly. If it is too low, you wont see any perceivable alteration. Since integral is increasing, the Ki value has a substantial impact. You may continue to retuning process with adjusting Ki by .01 increments. Once the mobile robot is tracking the line with reasonable accuracy, you can increase the speed and see if it is still able to track the line. Speed disturbs the PID controller and will require rearranging as the speed fluctuations. Results And Discusion A line following robot is programed with simple (on/off) control as a comparison purpose in evaluating the performance of the dynamic algorithm controlled robot. The results of the experiment are summarized in Table-1. From the data in the table, it can be observed that dynamic PID algorithm controlled robot has better performance in every criteria listed in the table compared to simple (on/off) control robot. The dynamic algorithm controlled robot has higher velocity, consumes less time to complete one whole circuit, tracks the line smoother and has lower tendency to astray from line compared to uncontrolled robot. Therefore this system can be used in training undergraduate students on dynamic PID algorithm control system, its application and implementation in the real world and the advantages that it offers. Fig. 3 shows the designed robot during race pits test. Figure 3 The designed robot on the race pits. Table 1- Experimental result for Line Following Robot. Criteria Dynamic PID algorithm Simple (on/off) Time to complete one whole circuit 47.6s 71.4s Line tracking Smooth Not so smooth Velocity 0.2m/s 0.14m/s Tendency to astray from line Low High Conclusion The designed wheeled line follower mobile robot has eight infrared sensors on the bottom for detecting the line. The controller board includes Stellaris LM3S811 micro-controller and the motor driver L298 which were used to control the direction and the speed of motors. The proposed dynamic PID algorithm derives the line follower locomotion by adequately combining the information from sensor module. Experimental results show that the proposed algorithm can successfully achieve target following in various scenarios, including straight line and circular motion, sharp-turn motion and S-shape line tracking. We are working currently to develop a more sophisticated algorithm which can perform faster line tracking with less energy consumption.

Savage Inequalities by Jonathan Kozol :: Education Poverty Public Schools

Savage Inequalities, written by Jonathan Kozol, shows his two-year investigation into the neighborhoods and schools of the privileged and disadvantaged. Kozol shows disparities in educational expenditures between suburban and urban schools. He also shows how this matter affects children that have few or no books at all and are located in bad neighborhoods. You can draw conclusions about the urban schools in comparison to the suburban ones and it would be completely correct. The differences between a quality education and different races are analyzed. Kozol even goes as far as suggesting that suburban schools have better use for their money because the children's futures are more secure in a suburban setting. He thinks that each child should receive as much as they need in order to be equal with everyone else. If children in Detroit have greater needs than a student in Ann Arbor, then the students in Detroit should receive a greater amount of money. My perception was changed completely after reading this book, I never knew that so many schools were situated in the ghettos and were so badly overcrowded or only had two toilets working for about 1000 students, and no toilet paper. What really upsets me is the fact that within the exact same city limits, there are schools situated in the suburbs which average 20 per classroom and have enough supplies and computers for every child to receive one as their own. Of course the majority of these suburban schools are dominantly white and the urban schools hold the minorities. The dropout rates that are listed in the book are ridiculous. Most of the children drop out in secondary school and never receive a proper education because of the lack of supplies or lack of teachers' interests. The majority of the kids are black or Hispanic in the poor schools and the suburban schools hold the upper-class white children and the occasional Asian or Japanese children who are in the gifted classe s. The small population of blacks and Hispanics that go to the schools are placed into the "special" classrooms and their "mental retardations" can be blamed for their placements. The majority of these students are not mental and they belonged in a regular classroom among whites and Asians. Kozol argues that the system is separate and unequal and he builds upon his hypothesis until it becomes credible.

Hartmann’s Ego Development and Adaptation Essay

Heinz Hartmann’s Ego Development and Adaptation was a more comprehensive development of Sigmund Freud’s theory of Psychoanalysis. In the theory Freud divided the human mind into the id, ego and superego with each part having a specific function. The id was the internal instinctive drive for satisfaction of basic human needs and desires. The ego developed in a person to counter the id and its basic drive. The ego in some quarters is known as pride since it separated man from animal by controlling unbridled instinctive behavior. The superego constituted the conscience of the person and helped to balance the id and the ego, allowing either to operate only as necessary to satisfy basic human desires while maintaining the dignity of the individual (Hartmann, 1958). This paper is a summary of Hartmann’s theory on Ego Development and Adaptation. Ego Development and Adaptation Like Freud, Hartmann believed that the ego developed as a result of human interaction with the environment. This environment provided external stimuli such as rebuke by parents and mistakes such as falling down a slippery floor that shaped the way a person interacted with his environment after the experience (Hartmann, 1958). However, he went further to assiduously study ego functions hence coming up with a general psychology and a clinical instrument to evaluate the functioning of an individual and formulate therapeutic interventions. He believed that the ego was not formed just by external influences but also has innate capacities such as perception, attention, memory, concentration, motor coordination, and language. Under what he termed an average expectable environment these capacities developed independently of libidinal and aggressive drives; consequently they were not products of frustration and conflict (Hartmann, 1958). Nevertheless, he agreed that the human condition was inextricably embroiled in conflict thus some of the functions were shaped and conditioned by such conflicts. Aggressive and libidinal drives therefore helped shape these functions in the face of the conflicts (Hartmann, 1958). Conclusion So according to Hartmann the duty of the psychoanalyst is to neutralize the impulses shaped by conflict so as to expand conflict free functions. Only in this way can the psychoanalyst help facilitate the proper adaptation of the individual to his environment (Hartmann, 1958).

Teen Pregnancy Is An Epidemic - Free Essay Example

Sample details Pages: 4 Words: 1275 Downloads: 5 Date added: 2019/04/05 Category Society Essay Level High school Tags: Teenage Pregnancy Essay Did you like this example? In recent years a total of 22.3 per 1,000 women between the ages of fifteen and nineteen became pregnant in America (Source 1). This continues to still a be a large amount of teenagers that become pregnant each year but the percentages have fallen by eight percent since 2014. Teenage pregnancy is still a serious concern in american society. Don’t waste time! Our writers will create an original "Teen Pregnancy Is An Epidemic" essay for you Create order Over nine percent of the teenage girls living in american get pregnant between the ages of fifteen and seventeen. Between 1991 and 2016 the rate of teen births has decreased by sixty-seven percent nationwide. Teenage pregnancy most definitely comes with a high cost with having to deal with doctor bills and all of the short term and long term effects that come along with teenage pregnancy. Teenage pregnancy is a term that continues to gain more and more attention across American society. As a matter of fact, the issue that society refers to as teenage pregnancy did not always exist in American culture (Source 2). In earlier times most people where married before they had kids, it was considered a sin if they became pregnant before marriage. In the mid 1950s teen pregnancy reached its peak by about one out of ten teenage girls got pregnant between the ages of fifteen and nineteen. This is still a very serious problem in todays society, but since the past two decades the rates of teenage pregnancy have been steadily declining. For years teenage pregnancy rates have been higher in southern industrialized areas (Source 3). There is no exact explanation for why these rates are higher in the south, but one contributing factor could be that there is much more poverty and they do not bring much attention to the resources that can prevent teenage pregnancy. In 2016 there were 20.3 births for every one thousand adolescent females from the ages fifteen to nineteen (Source 4). These numbers are still extremely high but for some odd reason african americans and latino rates are much higher than any other racial group of people in America. Ever since teenage pregnancy has became a concern in society there are always the long lasting effects that follow right behind it. There are many effects that come along with teenage pregnancy. Most teenagers lack the skills and knowledge that it takes to be a mother. Most teenage moms dont complete higher levels of education (Source 5). Teenage mothers are more likely to dropout of high school before even getting their diploma. This is because most of the time they are bullied and or made fun of for the poor decision they made. Some teenage mothers will even experience poverty and a complex array of social factors (Source 6). Most teen moms do not have the education nor ability to maintain a full time job and the ability to take care of there infant at the same time. The chances of a teen mom being economically successful are extremely low. Therefore, it is common for them to struggle for awhile if not the rest of their life while raising their child. Most of the time having a baby as a teenager will occasionally put the mother at increased risk for postpartum depression (Source 7). Teen moms are twice as lik ely to get postpartum depression than older adults. This is a disorder the mothers could experience during or after her pregnancy. A few of the causes of this disorder are sadness, anxiety and occasional suicidal thoughts. There are times when uncertainty about the future will arise when a teenage girl is pregnant (Source 7). Occasionally a teenage parent may feel that they do not have the ability or knowledge it takes to be a successful parent. They may come across some fears about how the baby will affect their future dreams and goals. Teenage moms dont just experience these effects but they also experience several problems and occasional compilations that come along with the pregnancy. There are many problems and occasional complications that come along with the teenage pregnancy. It is extremely important that a pregnant mother is to seek adequate medical care during her pregnancy because if not it can often result in moderate or severe complications (Source 8). The most commonly experienced complications during the pregnancy include anemia, toxemia and premature birth. Toxemia is a very serious condition where you experience abnormal swelling in your body that can eventually affect the unborn baby. Teenagers who become pregnant at a young age have a much higher risk of preterm birth, which often goes along with low birth weight (Source 9). It is very important that a pregnant mother consumes the right amount of nutrients that is needed for the baby to grow properly and to help prevent preterm birth. If the baby happens to be born earlier than expected it raises the risk of death or a serious disability. If a baby is born with a low birth weight, which is common w hen dealing with teenage pregnancy, it makes it difficult for the infant to gain weight and can also cause they baby to face serious health risks. Teenage mothers are also at a higher risk of pregnancy-induced hypertension (PIH). It can prevent the placenta from receiving enough blood which can result in low birth weight (Source 10). Pregnancy-induced hypertension is a pregnancy complication that is often caused by elevated blood pressure that can sometimes result in swelling which is due to protein in the urine. There are many negative side effects when it comes to dealing with this specific complication such as temporary kidney failure, blood clotting, liver problems and premature birth. Teenage mothers dont just face some of these complications but they also have to face what the society thinks of them. Teenage pregnancy does not just come along with several problems but it also affects american society. In most developing nations, governments plan welfare schemes to take good care of teenage mothers and their children, which results in a loss in government revenue (Source 11). The U.S. government spends about seven billion dollars in helping to fund teenage pregnancies each year. The government will somewhat help to provide money for public assistance, child health care, and foster care by not making the teenage mother pay taxes. Due to the government doing this they will face a large amount of revenue loss. Almost all teenage mothers lack the acquiring basic education qualifications, which leads them to a more poorly paid job which increases the risk of destitution in the society (Source 11). In most situations like this the father usually abdondes the teenage mother, leaving her with the sole responsibility. This normally leaves the mother living the rest of her life in povert y and running on the risk of imminent destitution. Almost eighty percent of all teenage mothers solely rely on the social welfare of government schemes designed by the nation. The rate in literacy continues to drop in society when teenagers get pregnant (Souce 12). When most teenagers get pregnant they make the choice to drop out of school or to take a temporary break on their education. This affects the society as a whole due to literacy rates dropping. As teenage pregnancy continues to affect american society the outlook on the future is getting better and better each year. In America slightly less than one in ten teenage girls become pregnant each year. The term teenage pregnancy still continues to be a nationwide problem in the american society. Although, the rates of teenage pregnancy are continuing to decrease year by year. Teenage girls still need to understand the consequences of becoming pregnant at such a young age. Becoming pregnant at a young age doesnt just leave the teenager at a higher risk of complications but at poverty and lack of responsibility.