Trends in the control of hexapod robots: a survey

The static stability of hexapods motivates their design for tasks in which stable locomotion is required, such as navigation across complex environments. This task is of high interest due to the possibility of replacing human beings in exploration, surveillance and rescue missions. For this application, the control system must adapt the actuation of the limbs according to their surroundings to ensure that the hexapod does not tumble during locomotion. The most traditional approach considers their limbs as robotic manipulators and relies on mechanical models to actuate them. However, the increasing interest in model-free models for the control of these systems has led to the design of novel solutions. Through a systematic literature review, this paper intends to overview the trends in this field of research and determine in which stage the design of autonomous and adaptable controllers for hexapods is.The first author received funding through a doctoral scholarship from the Portuguese Foundation for Science and Technology (FCT) (Grant No. SFRH/BD/145818/2019), with funds from the Portuguese Ministry of Science, Technology and Higher Education and the European Social Fund through the Programa Operacional Regional Norte. This work has been supported by the FCT national funds, under the national support to R&D units grant, through the reference project UIDB/04436/2020 and UIDP/04436/2020

Locomation strategies for amphibious robots-a review

In the past two decades, unmanned amphibious robots have proven the most promising and efficient systems ranging from scientific, military, and commercial applications. The applications like monitoring, surveillance, reconnaissance, and military combat operations require platforms to maneuver on challenging, complex, rugged terrains and diverse environments. The recent technological advancements and development in aquatic robotics and mobile robotics have facilitated a more agile, robust, and efficient amphibious robots maneuvering in multiple environments and various terrain profiles. Amphibious robot locomotion inspired by nature, such as amphibians, offers augmented flexibility, improved adaptability, and higher mobility over terrestrial, aquatic, and aerial mediums. In this review, amphibious robots' locomotion mechanism designed and developed previously are consolidated, systematically The review also analyzes the literature on amphibious robot highlighting the limitations, open research areas, recent key development in this research field. Further development and contributions to amphibious robot locomotion, actuation, and control can be utilized to perform specific missions in sophisticated environments, where tasks are unsafe or hardly feasible for the divers or traditional aquatic and terrestrial robots

Real-time system architecture design practices

International audienceIn this paper we give an overview of both hardware and software architectures of real time systems used in devices for various purposes-from lab bench contraptions to cars. The goal of the paper is to reveal separate classes of such architectures as well as to define preconditions for choosing a particular architecture

ArtPlanner: Robust Legged Robot Navigation in the Field

Due to the highly complex environment present during the DARPA Subterranean Challenge, all six funded teams relied on legged robots as part of their robotic team. Their unique locomotion skills of being able to step over obstacles require special considerations for navigation planning. In this work, we present and examine ArtPlanner, the navigation planner used by team CERBERUS during the Finals. It is based on a sampling-based method that determines valid poses with a reachability abstraction and uses learned foothold scores to restrict areas considered safe for stepping. The resulting planning graph is assigned learned motion costs by a neural network trained in simulation to minimize traversal time and limit the risk of failure. Our method achieves real-time performance with a bounded computation time. We present extensive experimental results gathered during the Finals event of the DARPA Subterranean Challenge, where this method contributed to team CERBERUS winning the competition. It powered navigation of four ANYmal quadrupeds for 90 minutes of autonomous operation without a single planning or locomotion failure

Dinâmica de um robô móvel hexápode: controlo e otimização

Dissertação de mestrado integrado em Engenharia MecânicaO interesse no desenvolvimento de robôs móveis autónomos tem vindo a aumentar, principalmente para a execução de tarefas de forma autónoma em ambientes considerados perigosos para o ser humano. Para o deslocamento em ambientes complexos, os robôs hexápodes apresentam uma boa solução devido ao seu elevado número de marchas estáveis com potencial para se adaptarem a qualquer topologia de terreno. Outra característica que motiva o seu desenvolvimento é a sua elevada estabilidade corporal, que é considerada uma prioridade para a navegação nestes cenários. O principal objetivo desta dissertação é gerar uma locomoção trípode para um robô hexápode em plano regular, de forma a que este seja capaz de alterar a sua trajetória para ultrapassar obstáculos autonomamente, utilizando a formulação dinâmica das suas pernas para o controlo da sua atuação. O trabalho é realizado em ambiente virtual, usando um modelo robótico desenvolvido pelo Laboratório de Automação e Robótica (LAR). Após revisão bibliográfica dos conceitos relevantes para a execução deste trabalho, realiza-se a análise cinemática e estática da perna robótica para formular a atuação correta das juntas em relação ao apoio do pé e estudar os esforços estáticos a que o mecanismo está sujeito nestas condições. Com o objetivo de otimizar o modelo estudado, propõe-se um novo desenho para o apoio da perna, para inserir um sensor de força, e ainda se analisa uma possível redução de massa para os componentes da tíbia e o fémur, reduzindo o binário necessário para os seus atuadores. De seguida, elabora-se a arquitetura de controlo do robô, usando a formulação de Newton-Euler das pernas para verificar o efeito das forças e momentos externos na atuação do sistema. A geração de trajetórias e a tomada de decisão para contorno de obstáculos são também implementadas em Python. Para testar o sistema de controlo idealizado, recorre-se ao programa de simulação robótica CoppeliaSim e ao ROS (Robot Operating System) para transporte de informação. Nesta simulação é possível compreender a viabilidade do sistema através da análise da estabilidade da locomoção.The interest in the development of autonomous mobile robots has been increasing, mainly for the execution of autonomous tasks in environments considered dangerous for human beings. For navigating across complex environments, hexapod robots provide a good solution due to their high number of stable gaits which can be adapted to any terrain topology. Another characteristic that motivates their design is their inherent body stability, which is prioritized for walking in these scenarios. The main objective of this dissertation is to generate a tripod locomotion for a hexapod robot walk across a regular plane which allows the change of the robot’s trajectory to autonomously overcome obstacles, using the dynamic formulation of its limbs to control its efficiency. The work is carried out in a virtual environment, using a robotic model designed by the Automation and Robotics Laboratory (LAR). After the bibliographic review of the concepts considered relevant for the execution of this work, the kinematic and static analyses of the robotic leg are performed to formulate the correct actuation of the joints considering the desired position of the foot-tip, and to study the static efforts which the mechanism is subjected in these conditions. To optimize the model studied, a new design is proposed for the leg support to insert a force sensor, and a possible reduction in the mass of the components of the tibia and femur is also analyzed, reducing the torque required for the actuators. Following this train of thought, the robot's control architecture is elaborated, using the Newton-Euler formulation of the legs to verify the impact of the external forces and moments on the system's efficiency. The generation of trajectories and decision-making for surmounting obstacles are also implemented in Python. To test the idealized control system, the CoppeliaSim robotic simulation program and the ROS (Robot Operating System) are used to transport information. In this simulation, it is possible to understand the reliability of the system through the analysis of the locomotion stability

Bio-Inspired Robotics

Modern robotic technologies have enabled robots to operate in a variety of unstructured and dynamically-changing environments, in addition to traditional structured environments. Robots have, thus, become an important element in our everyday lives. One key approach to develop such intelligent and autonomous robots is to draw inspiration from biological systems. Biological structure, mechanisms, and underlying principles have the potential to provide new ideas to support the improvement of conventional robotic designs and control. Such biological principles usually originate from animal or even plant models, for robots, which can sense, think, walk, swim, crawl, jump or even fly. Thus, it is believed that these bio-inspired methods are becoming increasingly important in the face of complex applications. Bio-inspired robotics is leading to the study of innovative structures and computing with sensory–motor coordination and learning to achieve intelligence, flexibility, stability, and adaptation for emergent robotic applications, such as manipulation, learning, and control. This Special Issue invites original papers of innovative ideas and concepts, new discoveries and improvements, and novel applications and business models relevant to the selected topics of ``Bio-Inspired Robotics''. Bio-Inspired Robotics is a broad topic and an ongoing expanding field. This Special Issue collates 30 papers that address some of the important challenges and opportunities in this broad and expanding field

Controlo da locomoção e previsão de eficiência de um robô hexápode recorrendo a aprendizagem supervisionada

Dissertação de estrado integrado em Engenharia MecânicaO crescente interesse no campo da robótica móvel tem levado a um aumento na investigação e desenvolvimento de robôs móveis autónomos, especialmente para realizar tarefas perigosas para os seres humanos. Para se deslocarem em ambientes complexos, os robôs hexápodes são uma boa escolha devido à sua capacidade de se adaptarem a diferentes tipos de terreno graças ao seu elevado número de marchas. Além disso, a estabilidade corporal dos robôs hexápodes é considerada uma prioridade para a navegação em ambientes desafiantes. A dissertação enquadra-se no projeto “ATHENA” (All-Terrain Hexapod for Environment Navigation Adaptability) e tem o intuito de desenvolver um modelo de um robô hexápode, tal como o seu controlo para locomoção em diferentes tipos de marcha. Ademais, procura-se também nesta dissertação a previsão da eficiência da marcha em diferentes topologias de terreno, recorrendo a técnicas de aprendizagem supervisionada para prever qual a marcha mais adequada em cada um. Após uma introdução ao tema, é realizada uma revisão dos principais conceitos para o desenvolvimento do projeto. Posteriormente, é abordado o desenvolvimento do protótipo do robô hexápode, englobando a seleção de todo o hardware utilizado e o desenvolvimento dos diferentes componentes do modelo físico final. Concluída a parte relativa ao protótipo, é feita uma abordagem à cinemática e controlo do robô, onde se aborda a cinemática direta e cinemática inversa da perna, assim como curvas de Bézier para definição da trajetória do pé. Ainda nesta secção, é apresentada a aplicação dos conceitos no robô de forma a permitir a locomoção do mesmo em diferentes tipos de marcha, utilizando para o efeito Arduíno e a linguagem de programação Python. De seguida, é feita a avaliação das diferentes marchas em diferentes tipos de terreno, recorrendo à utilização de um IMU e de visão por computador para recolha de dados propriocetivos e dados exterocetivos, utilizados posteriormente num algoritmo de aprendizagem supervisionada para perceber qual a marcha mais adequada para cada topologia. Por fim, é feita uma avaliação final de todo o trabalho desenvolvido.The growing interest in the field of mobile robotics has led to an increase in research and development of autonomous mobile robots, particularly for performing tasks that are dangerous for humans. For movement in complex environments, hexapod robots are a good choice due to their ability to adapt to different types of terrain thanks to their high number of stable gait. In addition, the body stability of hexapod robots is considered a priority for navigation in challenging environments The dissertation is part of the "ATHENA" (All-Terrain Hexapod for Environment Navigation Adaptability) project and aims to develop a model of a hexapod robot, as well as its control for movement in different types of gait. In addition, this dissertation also aims to predict the efficiency of gait in different types of terrain, using supervised learning techniques to predict the most appropriate gait in each one. After an introduction to the topic, a review of the main concepts for the development of the project is carried out. Subsequently, the development of the hexapod robot prototype is addressed, including the selection of all the hardware used and the development of the different components of the final physical model. Once the prototype section is completed, an approach to the kinematics and control of the robot is made, where the direct kinematics and inverse kinematics of the leg are addressed, as well as Bézier curves for defining the foot trajectory. In this section, the application of the concepts on the robot is also presented in order to allow its movement in different types of gait, using Arduino and the Python programming language. Next, the evaluation of the different gaits on different types of terrain is made, using an IMU and computer vision for proprioceptive and exteroceptive data collection, which are subsequently used in a supervised learning algorithm to understand the most appropriate gait for each typology. Finally, a final evaluation of all the work developed is made

From locomotion to cognition: Bridging the gap between reactive and cognitive behavior in a quadruped robot

The cognitivistic paradigm, which states that cognition is a result of computation with symbols that represent the world, has been challenged by many. The opponents have primarily criticized the detachment from direct interaction with the world and pointed to some fundamental problems (for instance the symbol grounding problem). Instead, they emphasized the constitutive role of embodied interaction with the environment. This has motivated the advancement of synthetic methodologies: the phenomenon of interest (cognition) can be studied by building and investigating whole brain-body-environment systems. Our work is centered around a compliant quadruped robot equipped with a multimodal sensory set. In a series of case studies, we investigate the structure of the sensorimotor space that the application of different actions in different environments by the robot brings about. Then, we study how the agent can autonomously abstract the regularities that are induced by the different conditions and use them to improve its behavior. The agent is engaged in path integration, terrain discrimination and gait adaptation, and moving target following tasks. The nature of the tasks forces the robot to leave the ``here-and-now'' time scale of simple reactive stimulus-response behaviors and to learn from its experience, thus creating a ``minimally cognitive'' setting. Solutions to these problems are developed by the agent in a bottom-up fashion. The complete scenarios are then used to illuminate the concepts that are believed to lie at the basis of cognition: sensorimotor contingencies, body schema, and forward internal models. Finally, we discuss how the presented solutions are relevant for applications in robotics, in particular in the area of autonomous model acquisition and adaptation, and, in mobile robots, in dead reckoning and traversability detection