Hardware Design and Testing of SUPERball, A Modular Tensegrity Robot

We are developing a system of modular, autonomous "tensegrity end-caps" to enable the rapid exploration of untethered tensegrity robot morphologies and functions. By adopting a self-contained modular approach, different end-caps with various capabilities (such as peak torques, or motor speeds), can be easily combined into new tensegrity robots composed of rods, cables, and actuators of different scale (such as in length, mass, peak loads, etc). As a first step in developing this concept, we are in the process of designing and testing the end-caps for SUPERball (Spherical Underactuated Planetary Exploration Robot), a project at the Dynamic Tensegrity Robotics Lab (DTRL) within NASA Ames's Intelligent Robotics Group. This work discusses the evolving design concepts and test results that have gone into the structural, mechanical, and sensing aspects of SUPERball. This representative tensegrity end-cap design supports robust and repeatable untethered mobility tests of the SUPERball, while providing high force, high displacement actuation, with a low-friction, compliant cabling system

Proposed exergetic based leak detection and diagnosis methodology for automotive carbon dioxide air conditioning systems

Due to the overwhelming concern of global warming and ozone depletion, the replacement of many currently used refrigerants is a pressing matter within all sectors of refrigeration. Presently, the hydroflourocarbon (HFC) 134a, the working fluid of automotive air conditioning (AC) systems, greatly contributes to global warming as the result of system leakage. Both chemical and natural refrigerant losses impose threats to the environment and human health as well as reduce operational efficiency which increases energy consumption. If no action is taken to replace the chemical refrigerants, then it is proposed that the emissions from fluorinated gasses would increase from 65.2 million tons of carbon dioxide (the value found in 1995) to 98 million tons by 2010 [EurActiv.com 2004]. Natural refrigerants have gained worldwide attention as the logical replacement for chemical refrigerants. Carbon dioxide (CO2) is the natural refrigerant receiving the most attention due to its abundance in nature. When deciding to replace a refrigerant worldwide, many factors are taken under consideration. The benefits and necessary changes that occur when using CO2 as the working fluid are explored. One important aspect of using CO2 as a replacement refrigerant in automotive AC systems lies in diagnosing refrigerant leakage within a faulty system. A reliable and easy to use refrigerant leakage detection and diagnosis system is a necessity for automotive mechanics. In current research at RIT, advanced thermodynamics is being used to develop a fault detection and diagnosis system specifically for the future CO2 automotive AC systems. A simulation of the automotive air conditioning system using the software program Engineering Equation Solver (EES) is developed to simulate normal and faulty operation of the AC system. The model incorporates an exergetic analysis which combines the conservation of mass and conservation of energy laws with the second law of Thermodynamics. Fundamental laws of thermodynamics are used to verify data provided by past work [McEnaney 1999] obtained during normal operation. Using the EES model, refrigerant losses are simulated throughout the system one at a time at locations prone to leakage and the model produces a faulty operating data library. Analyzing the simulated fault data for possible trends or patterns is done in order to detect future system faults and to diagnose the faults accordingly. Trends are produced from the faulty data and are shown in graphical form. It is possible to detect and diagnose leaks by looking at the trends for a component where leaks are not even occurring

Nonlinear Control Strategies for Outdoor Aerial Manipulators

In this thesis, the design, validation and implementation of nonlinear control strategies for aerial manipulators {i.e. aerial robots equipped with manipulators{ is studied, with special emphasis on the internal coupling of the system and its resilience against external disturbances. For the rst, di erent decentralised control strategies {i.e. using di erent control typologies for each one of the subsystems{ that indirectly take into account this coupling have been analysed. As a result, a nonlinear strategy composed of two controllers is proposed. A higher priority is given to the manipulation accuracy, relaxing the platform tracking, and hence obtaining a solution improving the manipulation capabilities with the surrounding environment. To validate these results, thorough stability and robustness analyses are provided, both theoretically and in simulation. On the other hand, a signi cant e ort has been devoted to improving the response and applicability of robot manipulators used in ight via control. In particular, the design of controllers for lightweight exible manipulators {that reduce the consequences of incidents involving unforeseen contacts{ is analysed. Although their inherent nature perfectly ts for aerial manipulation applications, the added exibility produces unwanted behaviours, such as second-order modes and uncertainties. To cope with them, an adaptable position nonlinear control strategy is proposed. To validate this contribution, the stability of the approach is studied in theory and its capabilities are proven in several experimental scenarios. In these, the robustness of the solution against unforeseen impacts and contact with uncharacterised interfaces is demonstrated. Subsequently, this strategy has been enriched with {multiaxis{ force control capabilities thanks to the inclusion of an outer control loop modifying the manipulator reference. Accordingly, this additional applicationfocused capability is added to the controlled system without loosing the modulated response of the inner-loop position strategy. It is also worth noting that, thanks to the cascade-like nature of the modi cation, the transition between position and force control modes is inherently smooth and automatic. The stability of this expanded strategy has been theoretically analysed and the results validated in a set of experimental scenarios. To validate the rst nonlinear approach with realistic outdoor simulations before its implementation, a computational uid dynamics analysis has been performed to obtain an explicit model of the aerodynamic forces and torques applied to the blunt-body of the aerial platform in ight. The results of this study have been compared to the most common alternative nowadays, being highlighted that the proposed model signi cantly surpasses this option in terms of accuracy. Moreover, it is worth underscoring that this characterisation could be also employed in the future to develop control solutions with enhanced rejection capabilities against wind conditions. Finally, as the focus of this thesis is on the use of novel control strategies on real aerial manipulation outdoors to improve their accuracy while performing complex tasks, a modular autopilot solution to be able to implement them has been also developed. This general-purpose autopilot allows the implementation of new algorithms, and facilitates their theory-to-experimentation transition. Taking into account this perspective, the proposed tool employs the simple and widely-known MAS interface and the highly reliable PX4 autopilot as backup, thus providing a redundant approach to handle unexpected incidents in ight.En esta tesis se ha estudiado el diseño, validación e implementación de estrategias de control no lineales para robots manipuladores aéreos –esto es, robots aéreos equipados con un sistema de manipulación robótica–, dándose especial énfasis a las interacciones internas del sistema y a su resiliencia frente a efectos externos. Para lo primero, se han analizado diferentes estrategias de control descentralizado –es decir, que usan tipologías de control diferentes para cada uno de los subsistemas–, pero que tienen indirectamente en consideración la interacción entre manipulación y vuelo. Como resultado de esta línea, se propone una estretegia de control conformada por dos controladores. Estos se coordinan de tal forma que se le da prioridad a la manipulación sobre el seguimiento de posiciones del vehículo, produciéndose un sistema de control que mejora la precisión de las interacciones entre el sistema manipulador y el entorno. Para validar estos resultados, se ha analizado su estabilidad y robustez tanto teóricamente como mediante simulaciones numéricas. Por otro lado, se ha buscado mejorar la respuesta y aplicabilidad de los manipuladores que se usan en vuelo mediante su control. Dentro de esta tendencia, la tesis se ha centrado en el diseño de controladores para manipuladores ligeros flexibles, ya que estos permiten reducir el peso del sistema completo y reducen el riesgo de incidentes debidos a contactos inesperados. Sin embargo, la flexibilidad de estos produce comportamientos indeseados durante la operación, como la aparición de modos de segundo orden y cierta incentidumbre en su comportamiento. Para reducir su impacto en la precisión de las tareas de manipulación, se ha desarrollado un controlador no lineal adaptable. Para validar estos resultados, se ha analizado la estabilidad del sistema teóricamente y se han desarrollado una serie de experimentos. En ellos, se ha comprobado su robustez ante impactos inesperados y contactos con elementos no caracterizados. Posteriormente, esta estrategia para manipuladores flexibles ha sido ampliada al añadir un bucle externo que posibilita el control en fuerzas en varias direcciones. Esto permite, mediante un único controlador, mantener la suave respuesta de la estrategia. Además cabe destacar que, al contar esta estrategia con un diseño en cascade, la transición entre los segmentos de desplazamiento del brazo y de aplicación de fuerzas es fluida y automática. La estabilidad de esta estrategia ampliada ha sido analizada teóricamente y los resultados han sido validados experimentalmente. Para validar la primera estrategia mediante simulaciones que representen fielmente las condiciones en exteriores antes de su implementación, ha sido necesario realizar un estudio mediante mecánica de fluidos computacional para obtener un modelo explícito de las fuerzas y momentos aerodinámicos a los que se efrenta la plataforma en vuelo. Los resultados de este estudio han sido comparados con la alternativa más empleada actualmente, mostrándose que los avances del método propuesto son sustanciales. Asimismo, es importante destacar que esta caracterización podría también usarse en el futuro para desarrollar controladores con una respuesta mejorada ante perturbaciones aerodinámicas, como en el caso de volar con viento. Finalmente, al ser esta una tesis centrada en las estrategias de control novedosas en sistemas reales para la mejora de su rendimiento en misiones complejas, se ha desarrollado un autopiloto modular fácilmente modificable para implementarlas. Este permite validar experimentalmente nuevos algoritmos y facilita la transición entre teoría y práctica. Para ello, esta herramienta se basa en una interfaz sencilla ampliamente conocida por los investigadores de robótica, Simulink®, y cuenta con un autopiloto de respaldo, PX4, para enfrentarse a los incidentes inesperados que pudieran surgir en vuelo

Low cost attitude control system scanwheel development

In order to satisfy a growing demand for low cost attitude control systems for small spacecraft, development of low cost scanning horizon sensor coupled to a low cost/low power consumption Reaction Wheel Assembly was initiated. This report addresses the details of the versatile design resulting from this effort. Tradeoff analyses for each of the major components are included, as well as test data from an engineering prototype of the hardware

Motor Control Systems Analysis, Design, and Optimization Strategies for a Lightweight Excavation Robot

This thesis entails motor control system analysis, design, and optimization for the University of Arkansas NASA Robotic Mining Competition robot. The open-loop system is to be modeled and simulated in order to achieve a desired rapid, yet smooth response to a change in input. The initial goal of this work is to find a repeatable, generalized step-by-step process that can be used to tune the gains of a PID controller for multiple different operating points. Then, sensors are to be modeled onto the robot within a feedback loop to develop an error signal and to make the control system self-corrective to account for slippage upon the Martian terrain with unknown soil parameters. Then, the closed loop system will be simulated again subject to an input disturbance that would account for the undulations and inconsistencies of the Martian terrain. Using the analysis techniques established in the first two phases of this thesis, methods of immediate optimization with regards to motor output performance and wheel slip correction are presented for the purpose of implementation upon the next iteration of the robot build. This work also presents a general algorithm for robot autonomy in competition runs, which comes along with specific sensor configuration and pseudocode for the basic commands that the algorithm is built upon. Future work for the analysis and design phases of this work would involve several iterations of custom motor control boards to be manufactured and tested on the robot build to verify the proposed generalized process of the PID tuning method. Future work for the automation phase of this work would involve the construction of a practice pit for the robot to build upon the primary automation strategy presented in the latter sections of this thesis

Ergonomic workplace design in an assembly line

The thesis presents the importance of ergonomics in industry. Enhanced productivity, higher-quality output, lower injury and absence rates, increased job satisfaction, and optimization of places are all strongly correlated with better ergonomics. Ergonomics is often overlooked in favour of other requirements, such as engineering, economics, or place availability. However, the benefits of investing in ergonomics for the business have been thoroughly proved over time, though. Moreover, regulations require a minimum of ergonomic quality in all workplaces. Therefore, the ergonomics should be included in the design phase of any workplace to be considered throughout the process and save redesign costs. On the other hand, it is advisable to analyse the current workplaces to make sure that productions are efficient, and they are compliant as well. The thesis will develop this case. A practical application of the ergonomics improvement in a workstation of a production line is carried out to meet the ergonomic requirements. The current ergonomics are evaluated from a recreation of the workstation in the laboratory. The worker's movement data is collected through a sensor suit of Xsens in a pilot test, and a software simulation is used to recreate the operator in his working environment and analyse his ergonomics. Finally, solutions are proposed to adapt the spaces with minimum investmen

Design, Development, and Characterization of a Low Velocity Impact System

This paper introduces low-velocity impacts (LVI), presents a concept for evaluating them, tests various materials for proof-of-concept, and discusses how the machine could be used in future university projects as well as how it could be improved. The paper begins by defining low-velocity impacts and describing the factors that influence them. The second topic is the iterative design process involved with making an impact machine so that accurate results can be obtained. In the third section, some of the challenges and opportunities associated with the concept of low velocity impacts with a variety of tests conducted on the machine and with different materials. A summary of the design and results of the study is presented at the end of the paper, followed by some suggestions for further research and improvements that could be made

Automatic Pill Dispenser and Reminder

The Automatic Pill Dispenser is a device which dispenses medications and reminds users when and which one to take, helping with medication adherence. Ideally, this machine will hold four different types of medications, which will be dispensed into a portable device, which the user can take with them throughout the day. When it is time, an integrated app will notify the user when they should take a specific pill. The main focus of work this year is to improve and refine the progress made from the previous group, while meeting the requirements of the design specifications. This year, the group is focused on making the Automatic Pill Dispenser more user friendly by creating a smart phone app which connects with the device and serves as the main operator. The portable device in which the pills are dispensed to is redesigned from the previous group, and is able to be used with the smart phone app. The device has also been made faster, which was accomplished by cutting out redundant sections and optimizing different aspects of the code, decreasing the overall dispensing time