Desenvolvimento do planejador de trajetória e do sistema de controle em malha aberta de um manipulador robótico de geometria esférica, embarcados em uma plataforma FPGA

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia mecânica, 2012.Esse trabalho descreve o desenvolvimento e a implementação de um controlador de trajetória retilínea em um robô esférico de 5 graus de liberdade. Para tanto, foi desenvolvida uma arquitetura de controle em malha aberta embarcada em uma FPGA para os três primeiros graus de liberdade do manipulador. Nesse intuito, apresenta-se, nesse trabalho, a modelagem cinemática direta e inversa do manipulador, bem como seu Jacobiano. Essa modelagem permite o controle da trajetória do robô em um caminho retilíneo descrito em coordenadas cartesianas. Na implementação do controle embarcado na FPGA, foi utilizado o microprocessador NIOS II, da Altera. Esse é o responsável pelos cálculos de posicionamento e velocidade do manipulador durante sua movimentação. Também são explicitadas as interfaces de acionamento e controle de cada um dos eixos do manipulador e seus respectivos motores. São ainda apresentadas as experiências de validação dos algoritmos implementados, através de simulações computacionais, bem como a validação das equações utilizadas. Além disso, são apresentados os resultados de movimentação do manipulador, seguindo uma trajetória pré-estabelecida, buscando validar na prática o controle implementado. _______________________________________________________________________________________ ABSTRACTThis paper describes the development and implementation of a controller for straight path trajectory in a spherical robot of five degrees of freedom. To do that, an open loop control architecture (embedded in an FPGA) was developed, for the first three degrees of freedom of the manipulator. Therefore, the direct and inverse kinematic models of the manipulator as well as its Jacobian are presented in this work. This modeling allows us to control the trajectory of the robot in a straight path described in Cartesian coordinates. In the implementation of the embedded controller in the FPGA, we have used the NIOS II microprocessor, from Altera. This is responsible for calculating the position and speed of the manipulator during its motion. Also the interfaces with the controllers of each axis of the handler and their respective engines are specified. We also present experiments to validate the implemented algorithms through computer simulations, as well as the validation of the equations used. Finally, the results are presented of the manipulator motion, following a predetermined path, in order to validate the control implemented in practice

Evaluation of a low-cost multithreading approach solution for an embedded system based on Arduino with pseudo-threads

Although projects using Arduino boards are becoming more and more common due to their simplicity, low cost, and a variety of applications, Arduino boards consist of a simple processor that does not allow the execution of threads. This paper presents a study and evaluation of multithreading approaches on a single Arduino board. We present a group of existing software approaches for dealing with concurrent actions on Arduino. Among the solutions presented, we propose a case study using timed interrupts due to their simplicity. Although the case study provided requires dealing with many actions concurrently, including external actions, timed interrupts showed to be a robust solution to the problem. Furthermore, the evaluated approach presented great potential for being applied and implemented commercially at low cost.info:eu-repo/semantics/publishedVersio

230501

Cooperative Vehicular Platooning (Co-VP) is a paradigmatic example of a Cooperative Cyber-Physical System (Co-CPS), which holds the potential to vastly improve road safety by partially removing humans from the driving task. However, the challenges are substantial, as the domain involves several topics, such as control theory, communications, vehicle dynamics, security, and traffic engineering, that must be coupled to describe, develop and validate these systems of systems accurately. This work presents a comprehensive survey of significant and recent advances in Co-VP relevant fields. We start by overviewing the work on control strategies and underlying communication infrastructures, focusing on their interplay. We also address a fundamental concern by presenting a cyber-security overview regarding these systems. Furthermore, we present and compare the primary initiatives to test and validate those systems, including simulation tools, hardware-in-the-loop setups, and vehicular testbeds. Finally, we highlight a few open challenges in the Co-VP domain. This work aims to provide a fundamental overview of highly relevant works on Co-VP topics, particularly by exposing their inter-dependencies, facilitating a guide that will support further developments in this challenging field.info:eu-repo/semantics/publishedVersio

Improving the Performance of Cooperative Platooning with Restricted Message Trigger Thresholds

Cooperative Vehicular Platooning (Co-VP) is one of the most prominent and challenging applications of Intelligent Traffic Systems. To support such vehicular communications, the ETSI ITS G5 standard specifies event-based communication profiles, triggered by kinematic parameters such as speed. The standard defines a set of threshold values for such triggers but no careful assessment in realistic platooning scenarios has been done to confirm the suitability of such values. In this work, we investigate the safety and performance limitations of such parameters in a realistic platooning co-simulation environment. We then propose more conservative threshold values, that we formalize as a new profile, and evaluate their impact in the longitudinal and lateral behaviour of a vehicular platoon as it carries out complex driving scenarios. Furthermore, we analyze the overhead introduced in the network by applying the new threshold values. We conclude that a pro-active message transmission scheme leads to improved platoon performance for highway scenarios, notably an increase greater than 40% in the longitudinal performance of the platoon, while not incurring in a significant network overhead. The obtained results also demonstrated an improved platoon performance for semi-urban scenarios, including obstacles and curves, where the heading error decreases in 26%, with slight network overhead.info:eu-repo/semantics/publishedVersio

230504

The advancements in wireless communication technologies have enabled unprecedented pervasiveness and ubiquity of Cyber-Physical Systems (CPS). Such technologies can now empower true Systemsof-Systems, which cooperate to achieve more complex and efficient functionalities. However, for CPS applications to become a reality, safety and security must be guaranteed, particularly in critical systems, since they rely on open communication systems prone to intentional and non-intentional interferences. We propose designing a Wireless Safety and Security Layer (WSSL) architecture to be implemented in critical CPS applications to address these issues. WSSL increases the reliability of these critical communications by enabling the detection of communication errors. Furthermore, it increases the CPS security using a message signature process that uniquely identifies the sender. So, we present the WSSL architecture and its implementation over an MQTT protocol. We prove that WSSL does not significantly increase the system transmission costs and demonstrate its capability to ensure safety and security, allowing it to be used in any general or critical CPS.info:eu-repo/semantics/publishedVersio

230604

The flight and control capabilities of uncrewed aerial vehicles (UAVs) have increased significantly with recent research for civilian and commercial applications. As a result, these devices are becoming capable of flying ever greater distances, accomplishing flights beyond line of sight (BVLOS). However, given the need for safety guarantees, these flights are increasingly subject to regulations. Handover operations between controllers and the security of the exchanged data are a challenge for implementing these devices in various applications. This paper presents a secure handover architecture between control stations, using a Software in the Loop (SIL) model to validate the adopted strategies and mitigate the time between simulation and real systems implementations. This architecture is developed in two separate modules that perform the security and handover processes. Finally, we validate the proposed architecture with several drone flights on a virtual testbed.This work was partially supported by National Funds through FCT/MCTES (Portuguese Foundation for Science and Technology), within the CISTER Research Unit (UIDP/UIDB/04234/2020); and by FCT and the EU ECSEL JU under the H2020 Framework Programme, within project ECSEL/0010/2019, JU grant nr. 876019 (ADACORSA). The JU receives support from the European Union’s Horizon 2020 research and innovation programme and Germany, Netherlands, Austria, France, Sweden, Cyprus, Greece, Lithuania, Portugal, Italy, Finland, Turkey. The ECSEL JU and the European Commission are not responsible for the content on this paper or any use that may be made of the information it contains.info:eu-repo/semantics/publishedVersio

A Dynamic Mode Decomposition approach with Hankel blocks to forecast multi-channel temporal series

Forecasting is a task with many concerns, such as the size, quality, and behavior of the data, the computing power to do it, etc. This letter proposes the dynamic mode decomposition (DMD) as a tool to predict the annual air temperature and the sales of a stores’ chain. The DMD decomposes the data into its principal modes, which are estimated from a training data set. It is assumed that the data is generated by a linear time-invariant high order autonomous system. These modes are useful to find the way the system behaves and to predict its future states, without using all the available data, even in a noisy environment. The Hankel block allows the estimation of hidden oscillatory modes, by increasing the order of the underlying dynamical system. The proposed method was tested in a case study consisting of the long term prediction of the weekly sales of a chain of stores. The performance assessment was based on the best fit percentage index. The proposed method is compared with three neural network-based predictors.info:eu-repo/semantics/publishedVersio

An Integrated Lateral and Longitudinal Look Ahead Controller for Cooperative Vehicular Platooning

Cooperative Vehicular Platooning (CoVP), has been emerging as a challenging Intelligent Traffic Systems application, promising to bring-about several safety and societal benefits. Relying on V2V communications to control such cooperative and automated actions brings several advantages. In this work, we present a Look Ahead PID controller for CoVP that solely relies upon V2V communications, together with a method to reduce the disturbance propagation in the platoon. The platooning controller also implements a solution to solve the cutting corner problem, keeping the platooning alignment. We evaluate its performance and limitations in realistic simulation scenarios, analyzing the stability and lateral errors of the CoVP, proving that such V2V enabled solutions can be effectively implemented.This work was partially supported by National Funds through FCT/MCTES (Portuguese Foundation for Science and Technology), within the CISTER Research Unit (UIDB/04234/2020).info:eu-repo/semantics/publishedVersio

Multivariate time series clustering and forecasting for building energy analysis: Application to weather data quality control

In recent years, several tools for building energy analysis and simulation have been developed to assist in increasing building energy performance, harvesting its computing capabilities for a reliable and accurate energy performance prediction. To perform this analysis, energy tools typically require crucial data regarding the building's surrounding environment, which is acquired from neighbouring weather stations. However, these stations often experience hardware malfunctions, resulting in either erroneous or missing data. Traditionally, these values are rectified through empirical and geostatistical methods, which, while reflecting several decades of practice, may prove to be inadequate when considering a purely data-driven approach. To this end, the present study introduces a machine learning methodology proposing the application of regression algorithms to rectify the erroneous values in datasets, and the clustering of weather stations, based on their recorded climatic conditions, to enhance the regression models. A shape-based approach for clustering time series of different climatic parameters and weather stations is pursued, using the k-medoids algorithm alongside dynamic time warping as the similarity measure. Both Artificial Neural Networks (ANN) and Support Vector Regression (SVR) models are evaluated as exemplary regression algorithms, with different sets of predictors. Mean Squared Error is used as the performance metric. A data set of different climatic parameters from southeastern Brazil was used, with air temperature being chosen as the response variable, given its importance in energy consumption. Results indicate that a machine learning approach to the problem is indeed viable. ANN slightly outperforms SVR in the prediction of the studied weather variable.Building energy analysisThis work was partially financially supported by UID/ECI/04708/ 2019 – CONSTRUCT –Instituto de I&D em Estruturas e Construções and UIDB/04234/2020 – CISTER Research Unit, both funded by national funds through the FCT/MCTES (PIDDAC).info:eu-repo/semantics/publishedVersio