Shape-based compliance control for snake robots

I serpenti robot sono una classe di meccanismi iper-ridondanti che appartiene alla robotica modulare. Grazie alla loro forma snella ed allungata e all'alto grado di ridondanza possono muoversi in ambienti complessi con elevata agilità. L'abilità di spostarsi, manipolare e adattarsi efficientemente ad una grande varietà di terreni li rende ideali per diverse applicazioni, come ad esempio attività di ricerca e soccorso, ispezione o ricognizione. I robot serpenti si muovono nello spazio modificando la propria forma, senza necessità di ulteriori dispositivi quali ruote od arti. Tali deformazioni, che consistono in movimenti ondulatori ciclici che generano uno spostamento dell'intero meccanismo, vengono definiti andature. La maggior parte di esse sono ispirate al mondo naturale, come lo strisciamento, il movimento laterale o il movimento a concertina, mentre altre sono create per applicazioni specifiche, come il rotolamento o l'arrampicamento. Un serpente robot con molti gradi di libertà deve essere capace di coordinare i propri giunti e reagire ad ostacoli in tempo reale per riuscire a muoversi efficacemente in ambienti complessi o non strutturati. Inoltre, aumentare la semplicità e ridurre il numero di controllori necessari alla locomozione alleggerise una struttura di controllo che potrebbe richiedere complessità per ulteriori attività specifiche. L'obiettivo di questa tesi è ottenere un comportamento autonomo cedevole che si adatti alla conformazione dell'ambiente in cui il robot si sta spostando, accrescendo le capacità di locomozione del serpente robot. Sfruttando la cedevolezza intrinseca del serpente robot utilizzato in questo lavoro, il SEA Snake, e utilizzando un controllo che combina cedevolezza attiva ad una struttura di coordinazione che ammette una decentralizzazione variabile del robot, si dimostra come tre andature possano essere modificate per ottenere una locomozione efficiente in ambienti complessi non noti a priori o non modellabili

Planning and Control Strategies for Motion and Interaction of the Humanoid Robot COMAN+

Despite the majority of robotic platforms are still confined in controlled environments such as factories, thanks to the ever-increasing level of autonomy and the progress on human-robot interaction, robots are starting to be employed for different operations, expanding their focus from uniquely industrial to more diversified scenarios. Humanoid research seeks to obtain the versatility and dexterity of robots capable of mimicking human motion in any environment. With the aim of operating side-to-side with humans, they should be able to carry out complex tasks without posing a threat during operations. In this regard, locomotion, physical interaction with the environment and safety are three essential skills to develop for a biped. Concerning the higher behavioural level of a humanoid, this thesis addresses both ad-hoc movements generated for specific physical interaction tasks and cyclic movements for locomotion. While belonging to the same category and sharing some of the theoretical obstacles, these actions require different approaches: a general high-level task is composed of specific movements that depend on the environment and the nature of the task itself, while regular locomotion involves the generation of periodic trajectories of the limbs. Separate planning and control architectures targeting these aspects of biped motion are designed and developed both from a theoretical and a practical standpoint, demonstrating their efficacy on the new humanoid robot COMAN+, built at Istituto Italiano di Tecnologia. The problem of interaction has been tackled by mimicking the intrinsic elasticity of human muscles, integrating active compliant controllers. However, while state-of-the-art robots may be endowed with compliant architectures, not many can withstand potential system failures that could compromise the safety of a human interacting with the robot. This thesis proposes an implementation of such low-level controller that guarantees a fail-safe behaviour, removing the threat that a humanoid robot could pose if a system failure occurred

Multi-contact planning and control for humanoid robots: Design and validation of a complete framework

In this paper, we consider the problem of generating appropriate motions for a torque- controlled humanoid robot that is assigned a multi-contact loco-manipulation task, i.e., a task that requires the robot to move within the environment by repeatedly establishing and breaking multiple, non-coplanar contacts. To this end, we present a complete multi-contact planning and control framework for multi-limbed robotic systems, such as humanoids. The planning layer works offline and consists of two sequential modules: first, a stance planner computes a sequence of feasible contact combinations; then, a whole-body planner finds the sequence of collision-free humanoid motions that realize them while respecting the physical limitations of the robot. For the challenging problem posed by the first stage, we propose a novel randomized approach that does not require the specification of pre-designed potential contacts or any kind of pre-computation. The control layer produces online torque commands that enable the humanoid to execute the planned motions while guaranteeing closed-loop balance. It relies on two modules, i.e., the stance switching and reactive balancing module; their combined action allows it to withstand possible execution inaccuracies, external disturbances, and modeling uncertainties. Numerical and experimental results obtained on COMAN+, a torque-controlled humanoid robot designed at Istituto Italiano di Tecnologia, validate our framework for loco-manipulation tasks of different complexity

Omnidirectional Walking Pattern Generator Combining Virtual Constraints and Preview Control for Humanoid Robots

This paper presents a novel omnidirectional walking pattern generator for bipedal locomotion combining two structurally different approaches based on the virtual constraints and the preview control theories to generate a flexible gait that can be modified on-line. The proposed strategy synchronizes the displacement of the robot along the two planes of walking: the zero moment point based preview control is responsible for the lateral component of the gait, while the sagittal motion is generated by a more dynamical approach based on virtual constraints. The resulting algorithm is characterized by a low computational complexity and high flexibility, requisite for a successful deployment to humanoid robots operating in real world scenarios. This solution is motivated by observations in biomechanics showing how during a nominal gait the dynamic motion of the human walk is mainly generated along the sagittal plane. We describe the implementation of the algorithm and we detail the strategy chosen to enable omnidirectionality and on-line gait tuning. Finally, we validate our strategy through simulation experiments using the COMAN + platform, an adult size humanoid robot developed at Istituto Italiano di Tecnologia. Finally, the hybrid walking pattern generator is implemented on real hardware, demonstrating promising results: the WPG trajectories results in open-loop stable walking in the absence of external disturbances

On the Palatini formulation of general relativity

In questo lavoro presentiamo la formulazione di Palatini della Relatività Generale. Per fare ciò, discutiamo le nozioni di base della teoria delle varietà differenziabili e della geometria (pseudo-)Riemanniana. In particolare, ci concentriamo sui fibrati vettoriali e sul concetto di connessione. Quest'ultimo è analizzato sia nel caso particolare di una connessione affine, ovvero sul fibrato tangente ad una varietà, sia nel caso generale di una connessione su un fibrato vettoriale arbitrario. Mentre la geometria Riemanniana e la Relatività Generale sono state storicamente sviluppate attraverso il calcolo tensoriale, noi seguiamo l'approccio di cui Elie Cartan, nel XX secolo, fu pioniere. Questo approccio individua le forme differenziali come oggetti fondamentali della teoria e risulta fondamentale nella costruzione dell'azione di Palatini. Di conseguenza, dedichiamo ampio spazio alla descrizione della connessione come forma differenziale, insieme alle forme di curvatura e di torsione. Prima di introdurre il formalismo di Palatini, richiamiamo brevemente le idee fisiche che hanno ispirato la Relatività Generale, come il Principio di Equivalenza, e mostriamo come si possano estrapolare le equazioni di Einstein a partire dall'equazione di Poisson per il potenziale gravitazionale. Infine, utilizziamo il formalismo di Cartan per derivare l'azione di Palatini e mostriamo come dalla variazione di quest'ultima sia possibile ritrovare le equazioni di Einstein

Ascending aorta dilatation is associated to hard cardiovascular events, follow-up from multicentric ARGO-Perspective project

: Aortic root dilatation has been proposed as hypertension-mediated organ damage (HMOD). Nevertheless, the role of the aortic root dilatation as a possible additional HMOD is still unclear since studies conducted so far are quite heterogeneous regarding the type of population analyzed, the aortic tract considered, and the type of outcomes accounted for. The aim of the present study is to assess whether the presence of aortic dilatation is associated with strong cardiovascular (CV) events (MACE: heart failure, CV death, stroke, acute coronary syndrome, myocardial revascularization) in a population of patients affected by essential hypertension. Four hundred forty-five hypertensive patients from six Italian hospitals were recruited as part of ARGO-SIIA study1. For all centers, follow-up was obtained by re-contacting all patients by telephone and through the hospital's computer system. Aortic dilatation (AAD) was defined through absolute sex-specific thresholds as in previous studies (41 mm for males, 36 mm for females). Median follow-up was 60 months. AAD was found to be associated with the occurrence of MACE (HR = 4.07 [1.81-9.17], p < 0.001). This result was confirmed after correction for main demographic characteristics such as age, sex and BSA (HR = 2.91 [1.18-7.17], p = 0.020). At penalized Cox regression, age, left atrial dilatation, left ventricular hypertrophy and AAD were identified as best predictor of MACEs and AAD resulted a significant predictor of MACEs even after correction for these confounders (HR = 2.43 [1.02-5.78], p = 0.045). The presence of AAD was found to be associated with an increased risk of MACE independently of for major confounders, including established HMODs. AAD ascending aorta dilatation, LAe left atrial enlargement, LVH left ventricular hypertrophy, MACEs major adverse cardiovascular events, SIIA Società Italiana dell'Ipertensione Arteriosa (Italian Society for Arterial Hypertension)

The use of emergency laparoscopy for acute abdomen in the elderly: the FRAILESEL Italian Multicenter Prospective Cohort Study

As the world population is aging rapidly, emergency abdominal surgery for acute abdomen in the elderly represents a global issue, both in developed and developing countries. Data regarding all the elderly patients who underwent emergency abdominal surgery from January 2017 to December 2017 at 36 Italian surgical departments were analyzed with the aim to appraise the contemporary reality regarding the use of emergency laparoscopy for acute abdomen in the elderly. 1993 patients were enrolled. 1369 (68.7%) patients were operated with an open technique; whereas, 624 (31.3%) underwent a laparoscopic operation. The postoperative morbidity rate was 32.6%, with a statically significant difference between the open and the laparoscopic groups (36.2% versus 22.1%, p < 0.001). The reported mortality rate was 8.8%, with a statistically significant difference between the open and the laparoscopic groups (11.2% versus 2.2%, p < 0.001). Our results demonstrated that patients in the ASA II (58.1%), ASA III (68.7%) and ASA IV (88.5%) groups were operated with the traditional open technique in most of the cases. Only a small percentage of patients underwent laparoscopy for perforated gastro-duodenal ulcer repair (18.9%), adhesiolyses with/without small bowel resection (12.2%), and large bowel resection (10.7%). Conversion to open technique was associated with a higher mortality rate (11.1% versus 2.2%, p < 0.001) and overall morbidity (38.9% versus 22.1%, p = 0.001) compared with patients who did not undergo conversion. High creatinine (p < 0.001) and glycaemia (p = 0.006) levels, low hemoglobin levels (p < 0.001), oral anticoagulation therapy (p = 0.001), acute respiratory failure (p < 0.001), presence of malignancy (p = 0.001), SIRS (p < 0.001) and open surgical approach (p < 0.001) were associated with an increased risk of postoperative morbidity. Regardless of technical progress, elderly patients undergoing emergency surgery are at very high risk for in-hospital complications. A detailed analysis of complications and mortality in the present study showed that almost 9% of elderly patients died after surgery for acute abdomen, and over 32% developed complications