From walking to running: robust and 3D humanoid gait generation via MPC

Humanoid robots are platforms that can succeed in tasks conceived for humans. From locomotion in unstructured environments, to driving cars, or working in industrial plants, these robots have a potential that is yet to be disclosed in systematic every-day-life applications. Such a perspective, however, is opposed by the need of solving complex engineering problems under the hardware and software point of view. In this thesis, we focus on the software side of the problem, and in particular on locomotion control. The operativity of a legged humanoid is subordinate to its capability of realizing a reliable locomotion. In many settings, perturbations may undermine the balance and make the robot fall. Moreover, complex and dynamic motions might be required by the context, as for instance it could be needed to start running or climbing stairs to achieve a certain location in the shortest time. We present gait generation schemes based on Model Predictive Control (MPC) that tackle both the problem of robustness and tridimensional dynamic motions. The proposed control schemes adopt the typical paradigm of centroidal MPC for reference motion generation, enforcing dynamic balance through the Zero Moment Point condition, plus a whole-body controller that maps the generated trajectories to joint commands. Each of the described predictive controllers also feature a so-called stability constraint, preventing the generation of diverging Center of Mass trajectories with respect to the Zero Moment Point. Robustness is addressed by modeling the humanoid as a Linear Inverted Pendulum and devising two types of strategies. For persistent perturbations, a way to use a disturbance observer and a technique for constraint tightening (to ensure robust constraint satisfaction) are presented. In the case of impulsive pushes instead, techniques for footstep and timing adaptation are introduced. The underlying approach is to interpret robustness as a MPC feasibility problem, thus aiming at ensuring the existence of a solution for the constrained optimization problem to be solved at each iteration in spite of the perturbations. This perspective allows to devise simple solutions to complex problems, favoring a reliable real-time implementation. For the tridimensional locomotion, on the other hand, the humanoid is modeled as a Variable Height Inverted Pendulum. Based on it, a two stage MPC is introduced with particular emphasis on the implementation of the stability constraint. The overall result is a gait generation scheme that allows the robot to overcome relatively complex environments constituted by a non-flat terrain, with also the capability of realizing running gaits. The proposed methods are validated in different settings: from conceptual simulations in Matlab to validations in the DART dynamic environment, up to experimental tests on the NAO and the OP3 platforms

Smell, smells and smelling in Victorian supernatural fiction of the fin de siècle

PhD ThesisMy PhD examines how writers at the fin de siècle responded to new understandings of smell, smells and smelling in their representations of the supernatural, demonstrating how those understandings were harnessed to nascent disciplines and technologies concerned with the limits and potential of the human subject. It recovers a lost history of smell and explains how shifts in the meaning of ‘smell’ (verb and noun) were witnessed and interrogated by writers in the period. Drawing attention to significant omissions from foundational accounts of olfaction in the nineteenth century, the thesis performs five key reclamatory readings to illuminate a number of supernatural stories. Firstly, it considers cross-channel influences on the articulation and reception of smell- description, drawing out a specifically British experience of scent that relates to the defaecalisation of the River Thames between 1858 and 1875. It then uncovers the origin, and demonstrates the literary manifestation, of analogies between music and scent. The thesis analyses how smells and noses in fin-de-siècle supernatural tales responded to new discursive possibilities afforded by late nineteenth-century developments in rhinoplasty, anaesthesia, nursing and Tractarian theology. The possible over-estimation of H. G. Wells’s reputation for early alignment with Darwinian theory is also considered through a recuperation of George William Piesse’s The Art of Perfumery (1855). Finally, it considers smellers and noses in Henry Rider Haggard’s She (1887), Richard Marsh’s The Beetle (1897), Bram Stoker’s Dracula (1897), Oscar Wilde’s The Picture of Dorian Gray (1891) and a range of prose fiction by Vernon Lee and Arthur Machen. Overall, it argues that in fin-de-siècle supernatural fiction the epistemology of smell, smells and smelling provided writers with new ways of testing, expanding and representing the boundaries of human identity

Texas Parks & Wildlife

Magazine discussing natural resources, parks, hunting and fishing, and other information related to the outdoors in Texas