Automatic Gait Pattern Selection for Legged Robots

An important issue when synthesizing legged locomotion plans is the combinatorial complexity that arises from gait pattern selection. Though it can be defined manually, the gait pattern plays an important role in the feasibility and optimality of a motion with respect to a task. Replacing human intuition with an automatic and efficient approach for gait pattern selection would allow for more autonomous robots, responsive to task and environment changes. To this end, we propose the idea of building a map from task to gait pattern selection for given environment and performance objective. Indeed, we show that for a 2D half-cheetah model and a quadruped robot, a direct mapping between a given task and an optimal gait pattern can be established. We use supervised learning to capture the structure of this map in a form of gait regions. Furthermore, we propose to construct a warm-starting trajectory for each gait region. We empirically show that these warm-starting trajectories improve the convergence speed of our trajectory optimization problem up to 60 times when compared with random initial guesses. Finally, we conduct experimental trials on the ANYmal robot to validate our method.</p

Hexapod robot stability research

El trabajo consiste en una primera parte en la que se estudia analíticamente la composición del robot hexápodo, descomponiéndolo en sus diferentes componentes físicos así como una introducción a la estabilidad del robot, tipos de estabilidad y métodos para su análisis.Grado en Ingeniería en Electrónica Industrial y Automátic

Tractable POMDP-planning for robots with complex non-linear dynamics

Planning under partial observability is an essential capability of autonomous robots. While robots operate in the real world, they are inherently subject to various uncertainties such a control and sensing errors, and limited information regarding the operating environment.Conceptually these type of planning problems can be solved in a principled manner when framed as a Partially Observable Markov Decision Process (POMDP). POMDPs model the aforementioned uncertainties as conditional probability functions and estimate the state of the system as probability functions over the state space, called beliefs. Instead of computing the best strategy with respect to single states, POMDP solvers compute the best strategy with respect to beliefs. Solving a POMDP exactly is computationally intractable in general.However, in the past two decades we have seen tremendous progress in the development of approximately optimal solvers that trade optimality for computational tractability. Despite this progress, approximately solving POMDPs for systems with complex non-linear dynamics remains challenging. Most state-of-the-art solvers rely on a large number of expensive forward simulations of the system to find an approximate-optimal strategy. For systems with complex non-linear dynamics that admit no closed-form solution, this strategy can become prohibitively expensive. Another difficulty in applying POMDPs to physical robots with complex transition dynamics is the fact that almost all implementations of state-of-the-art on-line POMDP solvers restrict the user to specific data structures for the POMDP model, and the model has to be hard-coded within the solver implementation. This, in turn, severely hinders the process of applying POMDPs to physical robots.In this thesis we aim to make POMDPs more practical for realistic robotic motion planning tasks under partial observability. We show that systematic approximations of complex, non-linear transition dynamics can be used to design on-line POMDP solvers that are more efficient than current solvers. Furthermore, we propose a new software-framework that supports the user in modeling complex planning problems under uncertainty with minimal implementation effort

Robotics handbook. Version 1: For the interested party and professional

This publication covers several categories of information about robotics. The first section provides a brief overview of the field of Robotics. The next section provides a reasonably detailed look at the NASA Robotics program. The third section features a listing of companies and organization engaging in robotics or robotic-related activities; followed by a listing of associations involved in the field; followed by a listing of publications and periodicals which cover elements of robotics or related fields. The final section is an abbreviated abstract of referred journal material and other reference material relevant to the technology and science of robotics, including such allied fields as vision perception; three-space axis orientation and measurement systems and associated inertial reference technology and algorithms; and physical and mechanical science and technology related to robotics

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