Balancing experiments on a torque-controlled humanoid with hierarchical inverse dynamics

Recently several hierarchical inverse dynamics controllers based on cascades of quadratic programs have been proposed for application on torque controlled robots. They have important theoretical benefits but have never been implemented on a torque controlled robot where model inaccuracies and real-time computation requirements can be problematic. In this contribution we present an experimental evaluation of these algorithms in the context of balance control for a humanoid robot. The presented experiments demonstrate the applicability of the approach under real robot conditions (i.e. model uncertainty, estimation errors, etc). We propose a simplification of the optimization problem that allows us to decrease computation time enough to implement it in a fast torque control loop. We implement a momentum-based balance controller which shows robust performance in face of unknown disturbances, even when the robot is standing on only one foot. In a second experiment, a tracking task is evaluated to demonstrate the performance of the controller with more complicated hierarchies. Our results show that hierarchical inverse dynamics controllers can be used for feedback control of humanoid robots and that momentum-based balance control can be efficiently implemented on a real robot.Comment: appears in IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 201

Rhenium(V)-Carbohydrate Complexes with Amino Acids

This thesis is about the coordination chemistry of rhenium(V) with small biomolecules. Such rhenium complexes may be of medical significance in the field of radiopharmacy, since radioactive isotopes such as 186Re or 188Re are used for the diagnosis or treatment of tumors. But fundamental research is still necessary for the attachment of radiometals to biologically active molecules. Most rhenium(V)-based radiopharmaceuticals lack stability (at physiological conditions) or selectivity (in terms of targeting cells, or in terms of preparing an exactly defined agent). In order to meet these requirements, a library of ligands was scanned to synthesize kinetically inert mixed-ligand rhenium(V) complexes. Most of the prepared complexes (22 out of 28) were built with tri- and bidentate chelating ligands (“3 + 2” approach). They were studied by means of single-crystal X-ray diffraction, NMR spectroscopy, mass spectrometry, elemental analysis and other methods. As tridentate chelators, nitrogen containing compounds such as diethylenetriamine, rac-2,3-diaminopropionic acid, L-histidine, L-carnosine and other ligands based on amino acids were used. As bidentate chelators, an oxygen donor library was used, covering simple diols such as ethanediol or anhydroerythritol, and more complex molecules such as nucleosides, pyranosides, mono- and disaccharides or glycoside antibiotics. The optimum was found for a compound derived from the reducing disaccharide D-isomaltose and the dipeptide L-carnosine. It was possible to transfer the synthesis from standard laboratory conditions (millimolar concentration range, methanol as solvent, alkaline pH) to labeling experiments with 188Re (nanomolar concentration range, water as solvent, physiological pH). With this work, the chemistry of coordination compounds with rhenium(V) is extended to physiological conditions and the synthesized compounds are promising candidates for prospective works in the field of radiopharmacy

PERIODIC TRENDS IN STRUCTURE FUNCTION RELATIONSHIP OF ORGANIC HETEROACENES

Our group has previously shown that small changes to molecular structure result in large changes to device properties and stability in organic electronic applications. By functionalizing aromatic heteroacenes with group 14 and group 16 elements, it is possible to control morphology and improve stability for a variety of applications such as thin film transistors and solar cells. Functionalization within the heteroacene core led to changes in electronic structure as observed by electrochemistry and light absorption. By substituting down the periodic table, the carbon heteroatom bond length increased, leading to subtle changes in crystal packing. Absorption maxima were red-­‐shifted and stability to light decreased. Substitution of group 14 elements to the solubilizing ethynyl groups attached to the heteroacene also had an effect on crystallization and stability. Substitution of silicon with carbon decreased solubility as well as stability to light. Substitution with germanium also decreased stability to light, but close contacts within the crystal structure and solubility in nonpolar organic solvents increased

LASER SPECTROSCOPY OF RADICALS CONTAINING GROUP IIIA AND VA ELEMENTS

Radicals are interesting to study because of importance in so many processes such as semiconductor growth or stellar evolution. Laser induced fluorescence (LIF) and wavelength resolved emission spectra of jet cooled HPS, HAsO, AsD2, H2PS, and F2BO have been measured using the pulsed discharge jet technique. Several bands in the à 1A′′ − X̃ 1A′ transition of HPS were observed and assigned with the help of ab initio calculations. The ab initio geometries showed that HPS does not follow Walsh’s predictions for the angle change upon electronic excitation; Walsh predicts an increase in HPS upon excitation while a decrease is calculated. Ab initio Walsh-style orbital angular correlation diagrams for both electronic states show a change in correlation for some orbitals upon electronic excitation, an effect that Walsh did not predict. The à 1A′′ − X̃ 1A′ transitions were measured in HAsO and DAsO for the first time. A molecular geometry was derived for each electronic state from experimental rotational constants. The experimental geometries prove that HAsO also violates Walsh’s rules for the same reason shown in HPS. The à 2A1 – X̃ 2B1 electronic transition of AsD2 and AsHD were measured. Vibrational levels observed in emission were fit to a local mode vibrational Hamiltonian. Using the previously reported rotational constants for AsH2 and those determined for AsD2 in this work, an improved estimate of the excited state geometry was obtained. The discovery of the B̃ 2A′ − X̃ 2A′ band system of H2PS is the first report of this molecule. Both D2PS and HDPS were also observed. Ab initio calculations helped assign the transition. H2PS is one of the few tetra-atomic or larger molecules that violates Kasha’s empirical rule due to the large separation between the B̃ and à states. Finally, laser induced fluorescence spectra of the F2BO radical was observed for the first time. Previous work showed two band systems with only a tentative assignment. The measured LIF spectra confirm the identity of the two band systems as the B̃ 2A1 – X̃ 2B2 and the B̃ 2A1 – à 2B1 transitions showing F2BO also violates Kasha’s rule

Momentum Control with Hierarchical Inverse Dynamics on a Torque-Controlled Humanoid

Hierarchical inverse dynamics based on cascades of quadratic programs have been proposed for the control of legged robots. They have important benefits but to the best of our knowledge have never been implemented on a torque controlled humanoid where model inaccuracies, sensor noise and real-time computation requirements can be problematic. Using a reformulation of existing algorithms, we propose a simplification of the problem that allows to achieve real-time control. Momentum-based control is integrated in the task hierarchy and a LQR design approach is used to compute the desired associated closed-loop behavior and improve performance. Extensive experiments on various balancing and tracking tasks show very robust performance in the face of unknown disturbances, even when the humanoid is standing on one foot. Our results demonstrate that hierarchical inverse dynamics together with momentum control can be efficiently used for feedback control under real robot conditions.Comment: 21 pages, 11 figures, 4 tables in Autonomous Robots (2015

Divided by Design

Low-income communities and communities of color have been and continue to be disproportionately harmed by our approach to transportation in the United States. This damage has come in many forms, but most egregiously through the manner in which the U.S. constructed of the Interstate Highway System. A growing understanding of this reality helped lead to the creation of new provisions and programs aimed at undoing some of this damage in the November 2021 infrastructure bill. But these steps were modest and policy interventions continue to focus largely on past harms or small, insufficient reforms, ultimately failing to grapple with the reality that the fundamental approach of our current transportation program creates and exacerbates inequities.Past decisions, including routing the Interstate Highway System through communities of color, dividing and often demolishing them in the process, still shape our built environment. And most importantly, the foundation of the modern transportation program was built on models, measures and standards that have their roots in this era. Without a fundamental change to the overall approach to transportation, today's leaders and transportation professionals, no matter their intent, will perpetuate and exacerbate the damage

Fibrations and Hasse diagrams for 6d SCFTs

We study the full moduli space of vacua of 6d worldvolume SCFTs on M5 branes probing an $A$-type singularity, focusing on the geometric incarnation of the discrete gauging mechanism which acts as a discrete quotient on the Higgs branch fibered over the tensor branch. We combine insights from brane constructions and magnetic quiver techniques, in which discrete gauging is implemented through the concept of decoration introduced in [arXiv:2202.01218]. We discover and characterize new transverse slices between phases of 6d SCFTs, identifying some of them with a family of isolated symplectic singularities recently discovered in [arXiv:2112.15494], and conjecturing the existence of two new isolated symplectic singularities