Feedback Control Design for MARLO, a 3D-Bipedal Robot.

This work develops feedback controllers for bipedal walking in 3D on level ground, both in simulation and experimentally. MARLO is a new robot that has been designed for the study of 3D-bipedal locomotion, with the aim of combining energy efficiency, speed, and robustness with respect to natural terrain variations in a single platform. The robot is highly underactuated, having six actuators and, in single support, 13 degrees of freedom. Its sagittal plane dynamics are designed to embody the spring loaded inverted pendulum (SLIP), which has been shown to provide a dynamic model of the body center of mass during steady running gaits in a wide diversity of terrestrial animals. A detailed dynamic model is used to optimize walking gaits with respect to the cost of mechanical transport (cmt), a dimensionless measure of energetic efficiency. A feedback controller is designed that balances the robot during the quiet standing mode, and another feedback policy is developed such that the robot can take a transition step from quiet standing to walking. A feedback controller is designed that stabilizes steady-state 3D walking gaits, despite the high degree of underactuation of the robot. These controllers are combined through a state machine that handles switching among the three controllers controllers. In experiments on planarized (2D) and untethered (3D) versions of the robot with point feet and passive feet (prosthetic feet) walking over flat ground or on a ramp with a shallow slope, the adaptability of the designed controller to the environment (planar or untethered, flat ground or ramp), and to the morphology of the robot (point feet or passive feet), is demonstrated. In experiments on a planarized version of the robot with passive feet, the controller yielded stable walking after starting from quiet standing, autonomously and without any intervention from the operator. In experiments on an untethered (3D) version of the robot, the controller was able to balance the robot over flat ground or on a shallow ramp during the quiet standing mode. In addition, the controller yielded six-untethered ``human-like'' steps after starting from quiet standing, autonomously without any intervention from the operator.PhDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/102339/1/aramez_1.pd

Modular Hopping and Running via Parallel Composition

Though multi-functional robot hardware has been created, the complexity in its functionality has been constrained by a lack of algorithms that appropriately manage flexible and autonomous reconfiguration of interconnections to physical and behavioral components. Raibert pioneered a paradigm for the synthesis of planar hopping using a composition of ``parts\u27\u27: controlled vertical hopping, controlled forward speed, and controlled body attitude. Such reduced degree-of-freedom compositions also seem to appear in running animals across several orders of magnitude of scale. Dynamical systems theory can offer a formal representation of such reductions in terms of ``anchored templates,\u27\u27 respecting which Raibert\u27s empirical synthesis (and the animals\u27 empirical performance) can be posed as a parallel composition. However, the orthodox notion (attracting invariant submanifold with restriction dynamics conjugate to a template system) has only been formally synthesized in a few isolated instances in engineering (juggling, brachiating, hexapedal running robots, etc.) and formally observed in biology only in similarly limited contexts. In order to bring Raibert\u27s 1980\u27s work into the 21st century and out of the laboratory, we design a new family of one-, two-, and four-legged robots with high power density, transparency, and control bandwidth. On these platforms, we demonstrate a growing collection of $\{$body, behavior$\}$ pairs that successfully embody dynamical running / hopping ``gaits\u27\u27 specified using compositions of a few templates, with few parameters and a great deal of empirical robustness. We aim for and report substantial advances toward a formal notion of parallel composition---embodied behaviors that are correct by design even in the presence of nefarious coupling and perturbation---using a new analytical tool (hybrid dynamical averaging). With ideas of verifiable behavioral modularity and a firm understanding of the hardware tools required to implement them, we are closer to identifying the components required to flexibly program the exchange of work between machines and their environment. Knowing how to combine and sequence stable basins to solve arbitrarily complex tasks will result in improved foundations for robotics as it goes from ad-hoc practice to science (with predictive theories) in the next few decades

MUSME 2011 4 th International Symposium on Multibody Systems and Mechatronics

El libro de actas recoge las aportaciones de los autores a través de los correspondientes artículos a la Dinámica de Sistemas Multicuerpo y la Mecatrónica (Musme). Estas disciplinas se han convertido en una importante herramienta para diseñar máquinas, analizar prototipos virtuales y realizar análisis CAD sobre complejos sistemas mecánicos articulados multicuerpo. La dinámica de sistemas multicuerpo comprende un gran número de aspectos que incluyen la mecánica, dinámica estructural, matemáticas aplicadas, métodos de control, ciencia de los ordenadores y mecatrónica. Los artículos recogidos en el libro de actas están relacionados con alguno de los siguientes tópicos del congreso: Análisis y síntesis de mecanismos ; Diseño de algoritmos para sistemas mecatrónicos ; Procedimientos de simulación y resultados ; Prototipos y rendimiento ; Robots y micromáquinas ; Validaciones experimentales ; Teoría de simulación mecatrónica ; Sistemas mecatrónicos ; Control de sistemas mecatrónicosUniversitat Politècnica de València (2011). MUSME 2011 4 th International Symposium on Multibody Systems and Mechatronics. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/13224Archivo delegad

3D Modelling and design of a bioloid compliant quadruped leg

Dissertação de mestrado integrado em Engenharia BiomédicaIn the growing fields of rehabilitation robotics, prosthetics, and walking robots, the modeling of a real robot is a complex and passionate challenge. On the crossing point of mechanics, physics and computer-science, the development of a complete model involves multiple tasks ranging from the 3D modeling of the different body parts, the measure of the different physic properties, the understanding of the requirements for an accurate simulation, to the development of a robotic controller. In order to minimize large forces due to shocks, to safely interact with the user or the environment, and knowing the ability of passive elastic elements to store and release energy, compliant mechanisms are increasingly being applied in robots applications. This work aims to the elaboration of an accurate efficient three-dimensional model of the legs of the quadruped Bioloid robot and the development of a world showing the effect on WebotsTM simulation software developed by Cyberbotics Ltd. The goal was to design a segmented pantographic leg with compliant joints, in order to actively retract the collision and the impact of the quadruped legs with the ground during locomotion. Geometrical and mechanical limits have to be evaluated and considered for the modeling setup. Finally a controller based on the use of Central Pattern Generators was improved in order to adapt to the novel model and simple tests were performed in the WebotsTM, rendering a 3D model simulation for the different values of spring-damping coefficients at the legs knee joint. Through the a MATLAB® algorithm, the characterization of the joint angles during simulation was possible to be assessed.A modelação de um robot real é um desafio complexo e fascinante na crescente área da Robótica, que engloba desde robots de reabilitação, próteses a uma diversidade de outros dispositivos locomotores. No cruzamento da mecânica com a física e as ciências computacionais, o desenvolvimento de um modelo completo envolve várias tarefas que vão desde a modelação 3D das diferentes partes do corpo, a medição das propriedades físicos inerentes, a compreensão dos requisitos para uma simulação precisa bem como a aplicação de um controlador robótico. A fim de minimizar grandes forças devido a choques, interagir com segurança com o utilizador ou o ambiente e conhecendo a capacidade de armazenagem de energia por parte de elementos elásticos passivos, um sistema de amortecimento-mola demonstra ser uma aplicação de crescente interesse na Robótica. Este trabalho visa a elaboração de um modelo tridimensional eficiente e preciso das pernas do robô quadrúpede Bioloid a ser reproduzido num mundo no software WebotsTM desenvolvido pela Cyberbotics Ltd. O objectivo foi desenhar uma perna pantográfica segmentada tridimensional a ser aplicada em paralelo com um sistema de amortecimento-mola de forma a retrair activamente a colisão e o impacto das patas do quadrúpede com o solo durante a locomoção. Deste modo para uma configuração do modelo bem sucedida são tidos em conta limites geométricos e mecânicos. Por ultimo, o controlador com base no uso de ‘Central Pattern Generators’ foi melhorado a fim de se adaptar ao novo modelo e por conseguinte foram realizados testes simples usando o simulador WebotsTM. Nesta parte experimental é realizada a simulação do modelo permitindo avaliar o comportamento do modelo 3D para diferentes valores de coeficientes de mola e de amortecimento aplicados a nível do joelho da perna. Através de um algoritmo MATLAB® é possível caracterizar e analisar o comportamento doa ângulos das juntas durante a simulação

Design of a stylus with variable tip compliance

Humans are known to modulate the impedance properties of their fingers in order to physically interact with the environment. For instance, painting or palpating fragile objects require high compliance of the fingers, while writing and measuring entails high precision position control, for which the stiffness of the fingers is increased considerably. In this thesis, we present the design, modeling, implementation, characterization and user verification of a stylus with variable tip compliance. In particular, we propose a variable stiffness mechanism as a compliant stylus that features an adjustable tip stiffness such that users can modulate compliance as needed to match the requirements of the task they perform. The variable stiffness of the stylus tip is achieved through transverse stiffness variations of axially loaded beams around their critical buckling load. Integrating an axially loaded beam with a compliant transmission mechanism, the stylus tip stiffness can be modulated over a large range. In particular, very low stiffness levels can be rendered with high fidelity, without sacrificing the mechanical integrity and load bearing capacity of the stylus. Compliant transmission mechanism of the stylus is analyzed through pseudo rigid body modeling which is a convenient and efficient way of modeling flexible elements exhibiting non-linear characteristics under large deflections. Furthermore, a novel pseudo rigid body model for a fixed-guided buckling beam that captures the iii transverse stiffness variations around the first critical buckling load is proposed and verified. These models are integrated to derive a lumped parameter model of the compliant stylus with adjustable tip stiffness. The lumped parameter model due to pseudo rigid body modeling promotes ease of analysis for design, by hiding the underlying modeling complexities of continuum mechanics from the designer. We provide experimental characterization results detailing the range of stiffness modulation achieved with several prototypes and verifying the accuracy of the equivalent pseudo rigid body model. We also present a set of human subject experiments that provide evidence in establishing the efficacy of the modulated stylus stiffness on the human performance

Design and Implement Towards Enhanced Physical Interactive Performance Robot Bodies

In this thesis, it will introduce the design principle and implement details towards enhanced physical interactive performance robot bodies, which are more specically focused on under actuated principle robotic hands and articulated leg robots. Since they both signicantly function as the physical interactive robot bodies against external environment, while their current performance can hardly satisfy the requirement of undertaking missions in real application. Regarding to the enhanced physical interactive performances, my work will emphasis on the three following specific functionalities, high energy efficiency, high strength and physical sturdiness in both robotics actuation and mechanism. For achieving the aforementioned targets, multiple design methods have been applied, rstly the elastic energy storage elements and compliant actuation have been adopted in legged robots as Asymmetrical Compliant Actuation (ACA), implemented for not only single joint but also multiple joints as mono and biarticulation congurations in order to achieve higher energy effciency motion. Secondly the under actuated principle and modular nger design concept have been utilized on the development of robotic hands for enhancing the grasping strength and physical sturdiness meanwhile maintaining the manipulation dexterity. Lastly, a novel high payload active tuning Parallel Elastic Actuation (PEA) and Series Elastic Actuation (SEA) have been adopted on legged robots for augmenting energy eciency and physical sturdiness. My thesis contribution relies on the novel design and implement of robotics bodies for enhancing physical interactive performance and we experimentally veried the design effectiveness in specic designed scenario and practical applications

Kinematic arrangement optimization of a quadruped robot with genetic algorithms

Quadruped robots are capable of performing a multitude of tasks like walking, running carrying and jumping. As research on quadruped robots grows, so does the variety of the designs available. These designs are often inspired by nature and finalized around technical constraints that are different for each project. A load carrying robot design will take its inspiration from a mule, while a running robot will use a cheetah-like design. However, this technique might be too broad when approaching a designing process for a quadruped robot aimed to accomplish certain tasks with varying degrees of importance. In order to reach an efficient design with precise link lengths and joint positions, for some specific task at hand, a complex series of problems have to be solved. This thesis proposes to use genetic algorithms to handle the designing process. An approach that mimics the evolutionary process of living beings, genetic algorithms can be used to reach quadruped designs which are optimized for a given task. The task-specific nature of this process is expected to result in more efficient designs than simply mimicking 4 animal structures, since animals are evolved to be efficient in a bigger variety of tasks. To explore this, genetic algorithms are used to optimize the kinematic structure of quadruped robots designed for the tasks of vertical jumping and trotting. The robots are optimized for these two tasks separately and then together. Algorithm results are compared to a relatively more conventional quadruped design

ATRIAS 1.0 & 2.1 : enabling agile biped locomotion with a template-driven approach to robot design

Practical bipedal robots need to be simultaneously efficient, robust, and versatile machines, but designing robots dynamically capable of these demands has been a significant bottleneck. We designed ATRIAS to be a highly dynamic biped capable of both walking and running untethered in real environments. To meet these goals, ATRIAS is designed to approximate dynamically capable locomotion template, i.e. the spring-mass model. We enumerate the challenges of this template-driven design approach and our solutions to make ATRIAS a real-world-viable human-scale machine. We show that ATRIAS exhibits behaviors predicted by spring-mass models in fulfillment of our design approach. Particularly, ATRIAS reproduces the characteristic ground-reaction forces of human walking and running, a key dynamical feature of spring-mass locomotion. We also demonstrate ATRIAS' capacity to walk, hop on one leg, bound like a spring-mass hopper, and recover from an unseen plunge into a 6.5-inch-deep gravel pit. Further, by building efficient spring-mass dynamics into the mechanical system, ATRIAS, when pushed, walks several steps without its actuators replenishing lost mechanical energy. These combined hardware experiments validate ATRIAS' capability as a platform for spring-mass robot controllers and for agile and economical locomotion in general. This thesis is the combination of two journal papers that focus on the ATRIAS robot that focus on statements in the above paragraph. It also includes a summary of the objectives and considerations that went into the design, manufacture and testing phases of the robots. This includes the project deliverables and deadlines, methods for building these robots, control theory considerations for ATRIAS, engineering objectives and questions addressed by this work