Compensating for model uncertainty in the control of cooperative field robots

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002.Includes bibliographical references (p. 113-123).Current control and planning algorithms are largely unsuitable for mobile robots in unstructured field environment due to uncertainties in the environment, task, robot models and sensors. A key problem is that it is often difficult to directly measure key information required for the control of interacting cooperative mobile robots. The objective of this research is to develop algorithms that can compensate for these uncertainties and limitations. The proposed approach is to develop physics-based information gathering models that fuse available sensor data with predictive models that can be used in lieu of missing sensory information. First, the dynamic parameters of the physical models of mobile field robots may not be well known. A new information-based performance metric for on-line dynamic parameter identification of a multi-body system is presented. The metric is used in an algorithm to optimally regulate the external excitation required by the dynamic system identification process. Next, an algorithm based on iterative sensor planning and sensor redundancy is presented to enable field robots to efficiently build 3D models of their environment. The algorithm uses the measured scene information to find new camera poses based on information content. Next, an algorithm is presented to enable field robots to efficiently position their cameras with respect to the task/target. The algorithm uses the environment model, the task/target model, the measured scene information and camera models to find optimum camera poses for vision guided tasks. Finally, the above algorithms are combined to compensate for uncertainties in the environment, task, robot models and sensors. This is applied to a cooperative robot assembly task in an unstructured environment.(cont.) Simulations and experimental results are presented that demonstrate the effectiveness of the above algorithms on a cooperative robot test-bed.by Vivek Anand Sujan.Ph.D

The sensor based manipulation of irregularly shaped objects with special application to the semiconductor industry

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1998.Includes bibliographical references (leaves 91-94).by Vivek Anand Sujan.S.M

A NEW TECHNIQUE IN MOBILE ROBOT SIMULTANEOUS LOCALIZATION AND MAPPING

ABSTRACT In field or indoor environments it is usually not possible to provide service robots with detailed a priori environment and task models. In such environments, robots will need to create a dimensionally accurate geometric model by moving around and scanning the surroundings with their sensors, while minimizing the complexity of the required sensing hardware. In this work, an iterative algorithm is proposed to plan the visual exploration strategy of service robots, enabling them to efficiently build a graph model of their environment without the need of costly sensors. In this algorithm, the information content present in sub-regions of a 2-D panoramic image of the environment is determined from the robot's current location using a single camera fixed on the mobile robot. Using a metric based on Shannon's information theory, the algorithm determines, from the 2-D image, potential locations of nodes from which to further image the environment. Using a feature tracking process, the algorithm helps navigate the robot to each new node, where the imaging process is repeated. A Mellin transform and tracking process is used to guide the robot back to a previous node. This imaging, evaluation, branching and retracing its steps continues until the robot has mapped the environment to a pre-specified level of detail. The effectiveness of this algorithm is verified experimentally through the exploration of an indoor environment by a single mobile robot agent using a limited sensor suite. KEYWORDS: Service robots, visual mapping, selflocalization, information theory, Mellin transform. RESUMO Usualmente não é possível fornecer a priori a robôs móveis autônomos um mapa detalhado de seu ambiente de trabalho. Nestes casos, o robô precisa criar um modelo geométrico preciso movendo-se pelo ambiente e utilizando seus sensores. Neste trabalho, um algoritmo iterativo é proposto para planejar a estratégia de exploração de robôs móveis autôno-mos, permitindo-os construir de forma eficiente um modelo do ambiente em forma de grafo sem a necessidade de sensores de alto custo. Neste algoritmo, o conteúdo de informação presente em sub-regiões de uma imagem panorâmica 2-D do ambiente é determinada a partir da posição atual do robô usando uma única câmera fixada em sua estrutura. Usando uma métrica baseada na teoria da informação de Shannon, o algoritmo determina, a partir da imagem 2-D, localizações potenciais para novos nós do grafo, a partir dos quais serão tomadas novas imagens panorâmicas para prosseguir com a exploração. Uma transformada de Mellin é usada para guiar o robô de volta a um nó previamente explorado. Este processo continua até que todo o ambiente tenha sido explorado em um nível de detalhes pré-especificado. A eficácia do algoritmo é verificada experimentalmente através da exploração de um ambiente interno por um agente robótico móvel dispondo apenas de um conjunto limitado de sensores. PALAVRAS-CHAVE: Robôs móveis, mapeamento visual, auto-localização, teoria da informação, transformada de Mellin

Minimal information for studies of extracellular vesicles (MISEV2023): From basic to advanced approaches

Extracellular vesicles (EVs), through their complex cargo, can reflect the state of their cell of origin and change the functions and phenotypes of other cells. These features indicate strong biomarker and therapeutic potential and have generated broad interest, as evidenced by the steady year-on-year increase in the numbers of scientific publications about EVs. Important advances have been made in EV metrology and in understanding and applying EV biology. However, hurdles remain to realising the potential of EVs in domains ranging from basic biology to clinical applications due to challenges in EV nomenclature, separation from non-vesicular extracellular particles, characterisation and functional studies. To address the challenges and opportunities in this rapidly evolving field, the International Society for Extracellular Vesicles (ISEV) updates its 'Minimal Information for Studies of Extracellular Vesicles', which was first published in 2014 and then in 2018 as MISEV2014 and MISEV2018, respectively. The goal of the current document, MISEV2023, is to provide researchers with an updated snapshot of available approaches and their advantages and limitations for production, separation and characterisation of EVs from multiple sources, including cell culture, body fluids and solid tissues. In addition to presenting the latest state of the art in basic principles of EV research, this document also covers advanced techniques and approaches that are currently expanding the boundaries of the field. MISEV2023 also includes new sections on EV release and uptake and a brief discussion of in vivo approaches to study EVs. Compiling feedback from ISEV expert task forces and more than 1000 researchers, this document conveys the current state of EV research to facilitate robust scientific discoveries and move the field forward even more rapidly

IMPROVING THE POSITIONING ACCURACY OF ROBOTIC MANIPULATORS SUBJECT TO BASE OSCILLATIONS

Abstract. Several robotic system applications require manipulators to carry heavy payloads while operating from moving vehicles. These manipulators are mounted on moving/compliant bases, introducing additional degrees of freedom that are not actuated, increasing the complexity of the dynamic modeling and control. In this paper, a control strategy to improve the performance of mobile robotic manipulators is presented. In the proposed architecture, a joint level controller needs to be designed to account for gravity, base motions, and manipulator joint friction. This is achieved by combining two methods: (i) a linear feed-forward dynamic disturbance compensation (DDC) method, which combines a dynamic model of the physical system with sensory feedback of the base oscillations to compensate for inertial effects; and (ii) Base Sensor Control, which compensates for nonlinear joint characteristics such as high joint friction. To evaluate the performance of the control architecture, a 3 DOF planar mobile manipulator is simulated including base oscillations, several payload weights, and Coulomb and viscous joint friction effects

INVERSE KINEMATICS OF A BINARY FLEXIBLE MANIPULATOR USING GENETIC ALGORITHMS

Abstract. This work presents an approach to calculate the inverse kinematics of a binary flexible manipulator. Binary manipulators are systems consisting of several actuators, each of them with only two potential states. By combining the binary state of each actuator, desired positions and trajectories can be obtained. A large number of actuators is desired to increase the number of end-effector positions and orientations attainable by the robot, approaching the performance of a continuous system. The main advantages of these redundant systems are ease of control and robustness to actuator failure. The studied manipulator structure is made of a polymer-reinforced elastomer, very flexible and lightweight, consisting of several independently pressurized chambers. Each chamber has only two states, pressurized or not, causing the manipulator structure to deform in a well-known direction. By leaving open or closed the valves of each chamber, the end-effector position and orientation can be controlled. However, to obtain the required inverse kinematics of a system consisting of m actuators, 2 m states would need to be evaluated through an exhaustive search. To avoid this computational burden, genetic algorithms are used in this work to obtain the required combination of valve states required to position the manipulator end-effector. Simulation results demonstrate the efficiency of the algorithm

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field