Achieving broad access to satellite control research with zero robotics

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2013.This thesis was scanned as part of an electronic thesis pilot project.Cataloged from PDF version of thesis.Includes bibliographical references (p. 307-313).Since operations began in 2006, the SPHERES facility, including three satellites aboard the International Space Station (ISS), has demonstrated many future satellite technologies in a true microgravity environment and established a model for developing successful ISS payloads. In 2009, the Zero Robotics program began with the goal of leveraging the resources of SPHERES as a tool for Science, Technology, Engineering, and Math education through a unique student robotics competition. Since the first iteration with two teams, the program has grown over four years into an international tournament involving more than two thousand student competitors and has given hundreds of students the experience of running experiments on the ISS. Zero Robotics tournaments involve an annually updated challenge motivated by a space theme and designed to match the hardware constraints of the SPHERES facility. The tournament proceeds in several phases of increasing difficulty, including a multi-week collaboration period where geographically separated teams work together through the provided tools to write software for SPHERES. Students initially compete in a virtual, online simulation environment, then transition to hardware for the final live championship round aboard the ISS. Along the way, the online platform ensures compatibility with the satellite hardware and provides feedback in the form of 3D simulation animations. During each competition phase, a continuous scoring system allows competitors to incrementally explore new strategies while striving for a seat in the championship. This thesis will present the design of the Zero Robotics competition and supporting online environment and tools that enable users from around the world to successfully write computer programs for satellites. The central contribution is a framework for building virtual platforms that serve as surrogates for limited availability hardware facilities. The framework includes the elaboration of the core principles behind the design of Zero Robotics along with examples and lessons from the implementation of the competition. The virtual platform concept is further extended with a web-based architecture for writing, compiling, simulating, and analyzing programs for a dynamic robot. A standalone and key enabling component of the architecture is a pattern for building fast, high fidelity, web-based simulations. For control of the robots, an easy to use programming interface for controlling 6 degree-of-freedom (6DOF) satellites is presented, along with a lightweight supervisory control law to prevent collisions between satellites without user action. This work also contributes a new form of student robotics competition, including the unique features of model-based online simulation, programming, 6DOF dynamics, a multi-week team collaboration phase, and the chance to test satellites aboard the ISS. Scoring during the competition is made possible by possible by a game-agnostic scoring algorithm, which has been demonstrated during a tournament season and improved for responsiveness. Lastly, future directions are suggested for improving the tournament including a detailed initial exploration of creating open-ended Monte Carlo analysis tools.by Jacob G. Katz.Ph.D

Completing Cooperative Task by Utilizing EEG-based Brain Computer Interface

We sought to design a cooperative brain computer interface (BCI), wherein multiple users contribute brain activities that are decoded towards a common goal. We used a base design involving collection of electroencephalographic (EEG) brain activity from a low-cost consumer system (the Muse Headband), then classified the ensuing signals into different mental states as either relaxed or focused. The goal of the cooperative BCI was to have two subjects drive a cursor on the screen to some acceptance range given a prescribed path. Each subject was responsible for controlling either the direction or the displacement of the ball. EEG patterns for the respective mental states were recognized and investigated through power spectral density estimation techniques. For the classification of patterns, we deployed linear discriminant analysis and support vector machine techniques on the gamma and alpha band limited EEG power. Our design yielded an average error rate of 14 percent and an average information transfer rate of 0.8 bit/s, despite the noisy data and limited array of EEG electrodes. With sufficient training for each subject, the cursor was successfully driven to the acceptance range. Our results establish the feasibility of cooperative BCI using relatively modest hardware

A Hybrid Controller for Stability Robustness, Performance Robustness, and Disturbance Attenuation of a Maglev System

Devices using magnetic levitation (maglev) offer the potential for friction-free, high-speed, and high-precision operation. Applications include frictionless bearings, high-speed ground transportation systems, wafer distribution systems, high-precision positioning stages, and vibration isolation tables. Maglev systems rely on feedback controllers to maintain stable levitation. Designing such feedback controllers is challenging since mathematically the electromagnetic force is nonlinear and there is no local minimum point on the levitating force function. As a result, maglev systems are open-loop unstable. Additionally, maglev systems experience disturbances and system parameter variations (uncertainties) during operation. A successful controller design for maglev system guarantees stability during levitating despite system nonlinearity, and desirable system performance despite disturbances and system uncertainties. This research investigates five controllers that can achieve stable levitation: PD, PID, lead, model reference control, and LQR/LQG. It proposes an acceleration feedback controller (AFC) design that attenuates disturbance on a maglev system with a PD controller. This research proposes three robust controllers, QFT, Hinf , and QFT/Hinf , followed by a novel AFC-enhanced QFT/Hinf (AQH) controller. The AQH controller allows system robustness and disturbance attenuation to be achieved in one controller design. The controller designs are validated through simulations and experiments. In this research, the disturbances are represented by force disturbances on the levitated object, and the system uncertainties are represented by parameter variations. The experiments are conducted on a 1 DOF maglev testbed, with system performance including stability, disturbance rejection, and robustness being evaluated. Experiments show that the tested controllers can maintain stable levitation. Disturbance attenuation is achieved with the AFC. The robust controllers, QFT, Hinf , QFT/ Hinf, and AQH successfully guarantee system robustness. In addition, AQH controller provides the maglev system with a disturbance attenuation feature. The contributions of this research are the design and implementation of the acceleration feedback controller, the QFT/ Hinf , and the AQH controller. Disturbance attenuation and system robustness are achieved with these controllers. The controllers developed in this research are applicable to similar maglev systems

Project Pele: Humanoid Robotic Programming - A Study in Artificial Intelligence

In the ever changing world of technology, the humanoid robot has been a constant member of science fiction culture. Our project goal was to develop a humanoid robot capable of independently displaying effective soccer skills. We divided the tasks into two teams; one designed a ball kicking robot program while the other designed a path tracking robot program. After each group completed their four major objectives, we had created a superior program than its predecessors. Using our optimized code as a foundation, another group can further develop these robot programs to demonstrate even more humanlike soccer skills

Project Pele: Humanoid Robotic Programming A Study in Artificial Intelligence

In the ever changing world of technology, the humanoid robot has been a constant member of science fiction culture. Our project goal was to develop a humanoid robot capable of independently displaying effective soccer skills. We divided the tasks into two teams; one designed a ball kicking robot program while the other designed a path tracking robot program. After each group completed their four major objectives, we had created a superior program than its predecessors. Using our optimized code as a foundation, another group can further develop these robot programs to demonstrate even more humanlike soccer skills

Project Pele: Humanoid Robotic Programming -A Study in Artificial Intelligence

In the ever changing world of technology, the humanoid robot has been a constant member of science fiction culture. Our project goal was to develop a humanoid robot capable of independently displaying effective soccer skills. We divided the tasks into two teams; one designed a ball kicking robot program while the other designed a path tracking robot program. After each group completed their four major objectives, we had created a superior program than its predecessors. Using our optimized code as a foundation, another group can further develop these robot programs to demonstrate even more humanlike soccer skills

Low Complexity Image Recognition Algorithms for Handheld devices

Content Based Image Retrieval (CBIR) has gained a lot of interest over the last two decades. The need to search and retrieve images from databases, based on information (“features”) extracted from the image itself, is becoming increasingly important. CBIR can be useful for handheld image recognition devices in which the image to be recognized is acquired with a camera, and thus there is no additional metadata associated to it. However, most CBIR systems require large computations, preventing their use in handheld devices. In this PhD work, we have developed low-complexity algorithms for content based image retrieval in handheld devices for camera acquired images. Two novel algorithms, ‘Color Density Circular Crop’ (CDCC) and ‘DCT-Phase Match’ (DCTPM), to perform image retrieval along with a two-stage image retrieval algorithm that combines CDCC and DCTPM, to achieve the low complexity required in handheld devices are presented. The image recognition algorithms run on a handheld device over a large database with fast retrieval time besides having high accuracy, precision and robustness to environment variations. Three algorithms for Rotation, Scale, and Translation (RST) compensation for images were also developed in this PhD work to be used in conjunction with the two-stage image retrieval algorithm. The developed algorithms are implemented, using a commercial fixed-point Digital Signal Processor (DSP), into a device, called ‘PictoBar’, in the domain of Alternative and Augmentative Communication (AAC). The PictoBar is intended to be used in the field of electronic aid for disabled people, in areas like speech rehabilitation therapy, education etc. The PictoBar is able to recognize pictograms and pictures contained in a database. Once an image is found in the database, a corresponding associated speech message is played. A methodology for optimal implementation and systematic testing of the developed image retrieval algorithms on a fixed point DSP is also established as part of this PhD work

Digital implementation of an upstream DOCSIS QAM modulator and channel emulator

The concept of cable television, originally called community antenna television (CATV), began in the 1940's. The information and services provided by cable operators have changed drastically since the early days. Cable service providers are no longer simply providing their customers with broadcast television but are providing a multi-purpose, two-way link to the digital world. Custom programming, telephone service, radio, and high-speed internet access are just a few of the services offered by cable service providers in the 21st century. At the dawn of the internet the dominant mode of access was through telephone lines. Despite advances in dial-up modem technology, the telephone system was unable to keep pace with the demand for data throughput. In the late 1990's an industry consortium known as Cable Television Laboratories, Inc. developed a standard protocol for providing high-speed internet access through the existing CATV infrastructure. This protocol is known as Data Over Cable Service Interface Specification (DOCSIS) and it helped to usher in the era of the information superhighway. CATV systems use different parts of the radio frequency (RF) spectrum for communication to and from the user. The downstream portion (data destined for the user) consumes the bulk of the spectrum and is located at relatively high frequencies. The upstream portion (data destined to the network from the user) of the spectrum is smaller and located at the low end of the spectrum. This lower frequency region of the RF spectrum is particularly prone to impairments such as micro-reflections, which can be viewed as a type of multipath interference. Upstream data transfer in the presence of these impairments is therefore problematic and requires complex signal correction algorithms to be employed in the receiver. The quality of a receiver is largely determined by how well it mitigates the signal impairments introduced by the channel. For this reason, engineers developing a receiver require a piece of equipment that can emulate the channel impairments in any permutation in order to test their receiver. The conventional test methodology uses a hardware RF channel emulator connected between the transmitter and the receiver under test. This method not only requires an expensive RF channel emulator, but a functioning analog front-end as well. Of these two problems, the expense of the hardware emulator is likely less important than the delay in development caused by waiting for a functional analog front-end. Receiver design is an iterative, time consuming process that requires the receiver's digital signal processing (DSP) algorithms be tested as early as possible to reduce the time-to-market. This thesis presents a digital implementation of a DOCSIS-compliant channel emulator whereby cable micro-reflections and thermal noise at the analog front-end of the receiver are modelled digitally at baseband. The channel emulator and the modulator are integrated into a single hardware structure to produce a compact circuit that, during receiver testing, resides inside the same field programmable gate array (FPGA) as the receiver. This approach removes the dependence on the analog front-end allowing it to be developed concurrently with the receiver's DSP circuits, thus reducing the time-to-market. The approach taken in this thesis produces a fully programmable channel emulator that can be loaded onto FPGAs as needed by engineers working independently on different receiver designs. The channel emulator uses 3 independent data streams to produce a 3-channel signal, whereby a main channel with micro-reflections is flanked on either side by adjacent channels. Thermal noise normally generated by the receiver's analog front-end is emulated and injected into the signal. The resulting structure utilizes 43 dedicated multipliers and 401.125 KB of RAM, and achieves a modulation error ratio (MER) of 55.29 dB

Three Essays in Comparative Political Economy

This thesis consists of three chapters. The first two chapters offer game theoretical models for different linkages between political parties and the citizens: programmatic linkage and clientelistic linkage. Empirical implications of these models are discussed using real world data on Turkey and USA through statistical analysis and simulation. The last chapter steps back from the specific strategies of political agents to examine in a more general context the concepts of institutional maintenance and institutional change