Bridging Vision and Dynamic Legged Locomotion

Legged robots have demonstrated remarkable advances regarding robustness and versatility in the past decades. The questions that need to be addressed in this field are increasingly focusing on reasoning about the environment and autonomy rather than locomotion only. To answer some of these questions visual information is essential. If a robot has information about the terrain it can plan and take preventive actions against potential risks. However, building a model of the terrain is often computationally costly, mainly because of the dense nature of visual data. On top of the mapping problem, robots need feasible body trajectories and contact sequences to traverse the terrain safely, which may also require heavy computations. This computational cost has limited the use of visual feedback to contexts that guarantee (quasi-) static stability, or resort to planning schemes where contact sequences and body trajectories are computed before starting to execute motions. In this thesis we propose a set of algorithms that reduces the gap between visual processing and dynamic locomotion. We use machine learning to speed up visual data processing and model predictive control to achieve locomotion robustness. In particular, we devise a novel foothold adaptation strategy that uses a map of the terrain built from on-board vision sensors. This map is sent to a foothold classifier based on a convolutional neural network that allows the robot to adjust the landing position of the feet in a fast and continuous fashion. We then use the convolutional neural network-based classifier to provide safe future contact sequences to a model predictive controller that optimizes target ground reaction forces in order to track a desired center of mass trajectory. We perform simulations and experiments on the hydraulic quadruped robots HyQ and HyQReal. For all experiments the contact sequences, the foothold adaptations, the control inputs and the map are computed and processed entirely on-board. The various tests show that the robot is able to leverage the visual terrain information to handle complex scenarios in a safe, robust and reliable manner

Fast and Continuous Foothold Adaptation for Dynamic Locomotion through CNNs

Legged robots can outperform wheeled machines for most navigation tasks across unknown and rough terrains. For such tasks, visual feedback is a fundamental asset to provide robots with terrain-awareness. However, robust dynamic locomotion on difficult terrains with real-time performance guarantees remains a challenge. We present here a real-time, dynamic foothold adaptation strategy based on visual feedback. Our method adjusts the landing position of the feet in a fully reactive manner, using only on-board computers and sensors. The correction is computed and executed continuously along the swing phase trajectory of each leg. To efficiently adapt the landing position, we implement a self-supervised foothold classifier based on a Convolutional Neural Network (CNN). Our method results in an up to 200 times faster computation with respect to the full-blown heuristics. Our goal is to react to visual stimuli from the environment, bridging the gap between blind reactive locomotion and purely vision-based planning strategies. We assess the performance of our method on the dynamic quadruped robot HyQ, executing static and dynamic gaits (at speeds up to 0.5 m/s) in both simulated and real scenarios; the benefit of safe foothold adaptation is clearly demonstrated by the overall robot behavior.Comment: 9 pages, 11 figures. Accepted to RA-L + ICRA 2019, January 201

Potential energy surface and spectroscopy of clusters of rare-gas atoms with cyclopropane

Analytical empirical potential energy surfaces describing the van der Waals interaction between rare-gas atoms and cyclopropane are presented. The functional form is based on pairwise Lennard-Jones-type potentials which have been widely used to describe rare-gas-benzene complexes, also studied in this work in order to check our theoretical method and for comparison. The parameters have been chosen in order to accurately fit the high resolution microwave spectra recently reported by Xu and Jäger [J. Chem. Phys. 106, 7968 (1997)]. The observed splitting in the microwave spectra of Ne-cyclopropane, associated with rotational tunneling, is well reproduced. Moreover, such tunneling is also important for complexes of Ar and Kr in excited van der Waals states. These phenomena involve a high delocalization of the wave functions and, therefore, intermolecular spectroscopy techniques would provide a good check of the potential energy surface over a broad region of the configuration space. © 1998 American Institute of Physics.This work has been supported by Consejería de Educación, Cultura y Deportes del Gobierno de Canarias under Grant No. PI 2/95, DGYCIT (Spain) under Grant No. PB95- 0071, and by the European TMR network Contract No. ERBFMRX-CT96-0088.Peer Reviewe

Model Predictive Control With Environment Adaptation for Legged Locomotion

Re-planning in legged locomotion is crucial to track the desired user velocity while adapting to the terrain and rejecting external disturbances. In this work, we propose and test in experiments a real-time Nonlinear Model Predictive Control (NMPC) tailored to a legged robot for achieving dynamic locomotion on a variety of terrains. We introduce a mobility-based criterion to define an NMPC cost that enhances the locomotion of quadruped robots while maximizing leg mobility and improves adaptation to the terrain features. Our NMPC is based on the real-time iteration scheme that allows us to re-plan online at $25\,\mathrm{Hz}$ with a prediction horizon of $2$ seconds. We use the single rigid body dynamic model defined in the center of mass frame in order to increase the computational efficiency. In simulations, the NMPC is tested to traverse a set of pallets of different sizes, to walk into a V-shaped chimney,and to locomote over rough terrain. In real experiments, we demonstrate the effectiveness of our NMPC with the mobility feature that allowed IIT's $87\, \mathrm{kg}$ quadruped robot HyQ to achieve an omni-directional walk on flat terrain, to traverse a static pallet, and to adapt to a repositioned pallet during a walk.Comment: Video available on: https://youtu.be/r0-KIiw0eW

A wave packet Golden Rule treatment of vibrational predissociation

The time-dependent wave packet technique is applied to the Golden Rule treatment of vibrational predissociation. The wave packet at time zero is taken as the product of the quasibound wave function and the coupling inducing predissociation. The rate for vibrational predissociation can then be obtained by Fourier transform into the energy domain of the time-dependent wave packet autocorrelation function. The method has been applied to a model triatomic van der Waals molecule. It is shown that when the bound-state components of the wave packet are projected out, the time-dependent version of the Golden Rule approximation provides an alternative efficient technique to treat intramolecular decay. © 1991 American Institute of Physics.Peer Reviewe

Functional Measurement of Special Education Teachers' and Students' Expectations Toward Job Training for Persons with Intellectual Disability

Persons with intellectual disability (PWID) have fewer opportunities for enrolment in school programs and post-school employment than do their peers with typical development. Evidence suggests that attitude toward PWID is a main factor in either promoting or limiting better life conditions for this population. In this paper, the goal was to determine the cognitive information integration rules underlying the expectations of 174 special education teachers and students with regard to job training for PWID. In order to accomplish this goal, four factors (Gender, Severity of disability, Type of task, and Emotional traits) were orthogonally combined to implement a cognitive algebra study design. We obtained 48 experimental conditions, with each one presented as a scenario describing a PWID in a work training situation. Participants read these scenarios and were asked to judge the probability of the success of PWID with regard to learning the skills needed to complete the required work. Patterns of response allowed us to identify low, moderate, and high viewpoints with regard to participants' judgments of predicted success. Personal factors (Emotional traits and Severity of disability) and the Type of task factor were considered the most important in influencing the participants' judgment. These factors seemed to be integrated in a complex systematic cognitive pattern. Implications from this type of result with regard to PWID and work training are discussed in this paper

Exact and quantum chemistry-like calculations in helium doped clusters: The He2Br2(X) example

7 pages, 2 figures, 2 tables.-- Issue title: "Proceedings from the Eleventh European Workshop on Quantum Systems in Chemistry and Physics", edited by Oleg Vasyutinskii, Jean Maruani, Piotr Piecuch, Gerardo Delgado-Barrio, Stephen Wilson.A quantum chemistry-like approach has been recently developed in our group to deal with HeN-BC doped helium clusters, where the BC dopant is a conventional diatomic molecule. The central idea is to consider the He atoms as electrons while the B and C atoms play the role of the nuclei in standard electronic structure calculations. The procedure provides energies and wavefunctions allowing to perform spectral simulations and, hence, making feasible to do proper comparisons with current experiments. However, because of the large difference of masses of He and electrons, and also to the replacement of Coulomb potentials by molecular interactions, it is worthy to assess to what extent the approximations involved in this model (decoupling of orbital angular momenta of the He atoms from the BC rotation and adiabatic separation of the BC stretch versus the He motions) lead to accurate results. In this work we address these issues on the 4He2-Br2(X) system, containing a couple of bosonic He atoms for which variational calculations can be performed.Funded by DGICYT Spanish grants (FIS2004-02461, CTQ2004-02415/BQU) and Spanish "Ramón y Cajal" Programme, Ministerio de Educación y Ciencia; Grant Number: PDRyC-2003-001015, PDRyC-2006-001017.Peer reviewe

Infrared spectrum of H 5 + and D 5 +: The simplest shared-proton model

We present a two-dimensional collinear, adiabatic model to describe the motion of a proton in between two hydrogen molecules which adjust their elongation to trace a minimum-energy path. Together with bound states, the predissociative, vibrationally excited states involved in the electric dipole transitions are characterized. The main qualitative features of the infrared spectra of H5 + and its deuterated variant are discussed, and the effect of the temperature of the clusters is analyzedThis work has been supported by the Consolider-Ingenio 2010 Programme CSD2009-00038 (MICINN), MICINN Grant No. FIS2010-18132, and CAM Grant No. S-2009/MAT/1467. P.B. acknowledges support from the “Fundación Ramón Areces.” The aid of COST Action CM1002 (CODECS) is also appreciate

Exact, Born–Oppenheimer, and quantum-chemistry-like calculations in helium clusters doped with light molecules: The He2N2(X) system

9 pages, 2 figures, 4 tables.-- PACS nrs.: 34.20.-b; 31.50.-x; 31.15.A-; 33.15.Mt; 33.20.Vq; 36.40.-c.Helium clusters doped with diatomic molecules, He(N)–BC, have been recently studied by means of a quantum-chemistry-like approach. The model treats He atoms as “electrons” and dopants as “nuclei” in standard electronic structure calculations. Due to the large mass difference between He atoms and electrons, and to the replacement of Coulomb interactions by intermolecular potentials, it is worth assessing up to what extent are the approximations involved in this model, i.e., decoupling of the BC rotation from the He-atom orbital angular momenta and Born–Oppenheimer separation of the BC stretch versus the He motions, accurate enough. These issues have been previously tackled elsewhere for the 4He2–Br2(X) system, which contains a heavy dopant [Roncero et al., Int. J. Quantum Chem. 107, 2756 (2007)]. Here, we consider a similar cluster but with a much lighter dopant such as N2(X). Although the model does not provide the correct energy levels for the cluster, positions and intensities of the main detectable lines of the vibrotational Raman spectrum at low temperature are accurately reproduced.This work has been partially supported by the DGICYT Spanish Grant Nos. FIS2007-62006 and CTQ2004-02415/BQU. M.P.de L.-C. acknowledges the support of a MEC-CSIC Spanish Grant No. 2007501004. The calculations presented here were performed at Centro de Cálculo of IMAFF (CSIC).Peer reviewe

Cognitive Algebra Underlying Special Education Teachers' and Psychology Students' Attitudes Towards School Inclusion of People with Intellectual Disability

Attitudes towards regular school inclusion of people with intellectual disabilities (ID) are affected by factors such as disability severity, educational level, and teacher experience. Nevertheless, the ways that teachers integrate these factors to form inclusion judgments remains unclear. The current paper explores what systematic cognitive algebra rules are used to cognitively integrate this set of inclusion factors by special education teachers and psychology students. To do so, 469 special education teachers and psychology students were asked to take part in two experimental cognitive algebra studies. In each study, participants had to read a set of school inclusion scenarios and rate the probability that a scenario actor with ID could be successfully integrated into a regular school program. To this purpose, factor effects on successful school inclusion and ID related to individuality, situational aspects, and contextual considerations (e.g., school environment, grade level taught) were explored. Results suggested that participants showed attitudes to school inclusion ranking from light to moderate positive values. Situational factors, as well as context factors, were judged to be more significant than other factors in elementary education. These factors were integrated by following a cognitive summative rule. Overall, judgment for successful school inclusion follows a summative rule to integrate sources of information. This rule is maintained irrespective of the disability under consideration. However, valuation of each source of information does depend on the type of the current study sample. Implications of these results for inclusion of people with disabilities in regular schools are discussed in this paper