Autonomous Collision Avoidance in Small Scale Vehicles

The undergraduate research performed in this study focused on autonomous collision avoidance in small scale vehicles. The goal of this study was to find equipment to build a fully autonomous small scale vehicle for use in different applications. Radio frequency communication, ultrasonic sensors, and single board computers were used to create an autonomous vehicle for multiple applications. Different communication protocols and sensors were investigated, and an explanation was specified concerning the hardware choice. The main communication protocol tested was Long Range Wide Area Network, and the main electronics tested and used were ultrasonic sensors, First Person View cameras, and the Arduino Mega 2560. Though the main communication protocol performed worse than anticipated, a different communication protocol was chosen and tested. The secondary communication protocol produced more promising results

Outdoor obstacle detection using ultrasonic sensors for an autonomous vehicle ensuring safe operations

Ultrasonic or sonar sensors are widely used for range finding for indoor and outdoor applications in robotics. However, for outdoors applications, they pose different environmental challenges. Ultrasonic sensor can be used both in air and underwater. It emits acoustic pulses in a cone shaped form in its surroundings and waits for the echoes from the objects nearby that lie within its working range. Ultrasonic sensors have convincing advantages over other sensors. However, sonar sensors have different practical limitations as well which need to be carefully dealt with while working with these sensors. Ultrasonic sensors have several applications in electronics and robotics including obstacle detection and avoidance, mapping and navigation, object recognition and identification. Ultrasonic sensors are widely used in automatic car parking systems in modern vehicles, where two to four sensors are mounted in rear bumper for detecting obstacles up to 2.5 meter and assisting the driver about the parallel parking. The thesis is mainly divided into two parts. In the first part, background studies and literature review is presented which describes sonar sensing principle, applications, advantages, limitations and outdoor sensing challenges. In the second part, a sonar system for obstacle detection for a mobile machine is implemented and its tests and results are discussed. The study indicates the testing of ultrasonic sensors for obstacles detection for an autonomous mobile vehicle outdoor. The sensors were tested both on static frame and on real machine detecting different obstacles from 60 cm up to five meters. The results are better when the object is in front or moving along the axis of the sensor. The sensors are connected in series and are in ranging mode all the time. The experimental results show that the environmental factors like, air turbulence and temperature change affect the speed of sound in air and measuring range. The ranging value is better indoors than the outdoors for same obstacles. However, the results are better on less windy day and also when the surface is strong reflector. It is noted that the results get improved when a cone made of paper or plastic is wrapped around the transducer. The sensor is protected with a water proof casing made of PVC plastic material and it is noted that the casing made of aluminum does not yield good results as compared with the plastic casing. The two or more sensors attached in line increase the covering area of the system

A Novel Approach To Intelligent Navigation Of A Mobile Robot In A Dynamic And Cluttered Indoor Environment

The need and rationale for improved solutions to indoor robot navigation is increasingly driven by the influx of domestic and industrial mobile robots into the market. This research has developed and implemented a novel navigation technique for a mobile robot operating in a cluttered and dynamic indoor environment. It divides the indoor navigation problem into three distinct but interrelated parts, namely, localization, mapping and path planning. The localization part has been addressed using dead-reckoning (odometry). A least squares numerical approach has been used to calibrate the odometer parameters to minimize the effect of systematic errors on the performance, and an intermittent resetting technique, which employs RFID tags placed at known locations in the indoor environment in conjunction with door-markers, has been developed and implemented to mitigate the errors remaining after the calibration. A mapping technique that employs a laser measurement sensor as the main exteroceptive sensor has been developed and implemented for building a binary occupancy grid map of the environment. A-r-Star pathfinder, a new path planning algorithm that is capable of high performance both in cluttered and sparse environments, has been developed and implemented. Its properties, challenges, and solutions to those challenges have also been highlighted in this research. An incremental version of the A-r-Star has been developed to handle dynamic environments. Simulation experiments highlighting properties and performance of the individual components have been developed and executed using MATLAB. A prototype world has been built using the WebotsTM robotic prototyping and 3-D simulation software. An integrated version of the system comprising the localization, mapping and path planning techniques has been executed in this prototype workspace to produce validation results

Advances in Sonar Technology

The demand to explore the largest and also one of the richest parts of our planet, the advances in signal processing promoted by an exponential growth in computation power and a thorough study of sound propagation in the underwater realm, have lead to remarkable advances in sonar technology in the last years.The work on hand is a sum of knowledge of several authors who contributed in various aspects of sonar technology. This book intends to give a broad overview of the advances in sonar technology of the last years that resulted from the research effort of the authors in both sonar systems and their applications. It is intended for scientist and engineers from a variety of backgrounds and even those that never had contact with sonar technology before will find an easy introduction with the topics and principles exposed here

Optical tracking control of a differentially-driven wheeled robot

Mobile robotics has become an increasingly ubiquitous technology in modern times. A typical example is the wheeled mobile robot (WMR). In order for a WMR to function effectively, it must demonstrate excellent tracking control and localisation capabilities. This is achieved by having accurate and responsive control algorithms as well as high-precision sensor systems. However, this often requires complicated algorithms and expensive equipment. This thesis proposes a system to show that good tracking performance can be achieved with moderately simple control algorithm and relatively inexpensive hardware. The platform used in this research was a differentially-driven wheeled robot constructed using the Lego MindstormsNXT system. Positional tracking was provided by two Avago optical laser sensors commonly found on the computer mouse. The main programming environments were MATLAB and Simulink, along with several other open-source applications. In the first part of the thesis, a PID-based system is presented along with the two control schemes. The first is a purely kinematic model and the second includes dynamic constraints. For both versions, a cascaded PID design was employed and settings were manually tuned. The final mathematical models were computationally simulated and their respective results were analysed and compared. Hardware validation was not conducted for this phase of the research as the simulation results suggested that the PID-based system may not produce the desired level of tracking performance. The second part of the thesis explores a model reference adaptive control system. Lyapunov's direct method was used to achieve stability and convergence in the system. In contrast to the PID-based model, a vastly more accurate geometric localisation technique was applied. The research identified a number of shortcomings in current geometric localisation methods and suggested ways to mitigate them. In addition, a novel approach for detecting faulty sensor readings was introduced in conjunction with the development of a semi-redundant system. The eventual theoretical model was tested using computer simulation, and the outcome was contrasted with the results of the PID-based system. This was followed by the construction of a prototype in order to verify the validity of the proposed model. Various configurations of the adaptive model were tested and compared: the two localisation methods, use of single and dual sensors, and application of semi-redundancy. The thesis concludes with the analysis of results of the prototype testing. The theoretical propositions in the thesis were shown to be amply validated. Suggestions for future research work are also presented

Codificación de emisiones ultrasónicas con secuencias complementarias para uso en exteriores

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