Pouring by Feel: An Analysis of Tactile and Proprioceptive Sensing for Accurate Pouring

As service robots begin to be deployed to assist humans, it is important for them to be able to perform a skill as ubiquitous as pouring. Specifically, we focus on the task of pouring an exact amount of water without any environmental instrumentation, that is, using only the robot's own sensors to perform this task in a general way robustly. In our approach we use a simple PID controller which uses the measured change in weight of the held container to supervise the pour. Unlike previous methods which use specialized force-torque sensors at the robot wrist, we use our robot joint torque sensors and investigate the added benefit of tactile sensors at the fingertips. We train three estimators from data which regress the poured weight out of the source container and show that we can accurately pour within 10 ml of the target on average while being robust enough to pour at novel locations and with different grasps on the source container

Data-driven Tactile Sensing using Spatially Overlapping Signals

Providing robots with distributed, robust and accurate tactile feedback is a fundamental problem in robotics because of the large number of tasks that require physical interaction with objects. Tactile sensors can provide robots with information about the location of each point of contact with the manipulated object, an estimation of the contact forces applied (normal and shear) and even slip detection. Despite significant advances in touch and force transduction, tactile sensing is still far from ubiquitous in robotic manipulation. Existing methods for building touch sensors have proven difficult to integrate into robot fingers due to multiple challenges, including difficulty in covering multicurved surfaces, high wire count, or packaging constrains preventing their use in dexterous hands. In this dissertation, we focus on the development of soft tactile systems that can be deployed over complex, three-dimensional surfaces with a low wire count and using easily accessible manufacturing methods. To this effect, we present a general methodology called spatially overlapping signals. The key idea behind our method is to embed multiple sensing terminals in a volume of soft material which can be deployed over arbitrary, non-developable surfaces. Unlike a traditional taxel, these sensing terminals are not capable of measuring strain on their own. Instead, we take measurements across pairs of sensing terminals. Applying strain in the receptive field of this terminal pair should measurably affect the signal associated with it. As we embed multiple sensing terminals in this soft material, a significant overlap of these receptive fields occurs across the whole active sensing area, providing us with a very rich dataset characterizing the contact event. The use of an all-pairs approach, where all possible combinations of sensing terminals pairs are used, maximizes the number of signals extracted while reducing the total number of wires for the overall sensor, which in turn facilitates its integration. Building an analytical model for how this rich signal set relates to various contacts events can be very challenging. Further, any such model would depend on knowing the exact locations of the terminals in the sensor, thus requiring very precise manufacturing. Instead, we build forward models of our sensors from data. We collect training data using a dataset of controlled indentations of known characteristics, directly learning the mapping between our signals and the variables characterizing a contact event. This approach allows for accessible, cheap manufacturing while enabling extensive coverage of curved surfaces. The concept of spatially overlapping signals can be realized using various transduction methods; we demonstrate sensors using piezoresistance, pressure transducers and optics. With piezoresistivity we measure resistance values across various electrodes embedded in a carbon nanotubes infused elastomer to determine the location of touch. Using commercially available pressure transducers embedded in various configurations inside a soft volume of rubber, we show its possible to localize contacts across a curved surface. Finally, using optics, we measure light transport between LEDs and photodiodes inside a clear elastomer which makes up our sensor. Our optical sensors are able to detect both the location and depth of an indentation very accurately on both planar and multicurved surfaces. Our Distributed Interleaved Signals for Contact via Optics or D.I.S.C.O Finger is the culmination of this methodology: a fully integrated, sensorized robot finger, with a low wire count and designed for easy integration into dexterous manipulators. Our DISCO Finger can generally determine contact location with sub-millimeter accuracy, and contact force to within 10% (and often with 5%) of the true value without the need for analytical models. While our data-driven method requires training data representative of the final operational conditions that the system will encounter, we show our finger can be robust to novel contact scenarios where the shape of the indenter has not been seen during training. Moreover, the forward model that predicts contact locations and applied normal force can be transfered to new fingers with minimal loss of performance, eliminating the need to collect training data for each individual finger. We believe that rich tactile information, in a highly functional form with limited blind spots and a simple integration path into complete systems, like we demonstrate in this dissertation, will prove to be an important enabler for data-driven complex robotic motor skills, such as dexterous manipulation

VFAS-Grasp: Closed Loop Grasping with Visual Feedback and Adaptive Sampling

We consider the problem of closed-loop robotic grasping and present a novel planner which uses Visual Feedback and an uncertainty-aware Adaptive Sampling strategy (VFAS) to close the loop. At each iteration, our method VFAS-Grasp builds a set of candidate grasps by generating random perturbations of a seed grasp. The candidates are then scored using a novel metric which combines a learned grasp-quality estimator, the uncertainty in the estimate and the distance from the seed proposal to promote temporal consistency. Additionally, we present two mechanisms to improve the efficiency of our sampling strategy: We dynamically scale the sampling region size and number of samples in it based on past grasp scores. We also leverage a motion vector field estimator to shift the center of our sampling region. We demonstrate that our algorithm can run in real time (20 Hz) and is capable of improving grasp performance for static scenes by refining the initial grasp proposal. We also show that it can enable grasping of slow moving objects, such as those encountered during human to robot handover

Developing a 3-DOF Compliant Perching Arm for a Free-Flying Robot on the International Space Station

This paper presents the design and control of the 3-DOF compliant perching arm for the free-flying Astrobee robots that will operate inside the International Space Station (ISS). The robots are intended to serve as a flexible platform for future guest scientists to use for zero-gravity robotics research - thus, the arm is designed to support manipulation research. It provides a 1-DOF underactuated tendon-driven gripper capable of enveloping a range of objects of different shapes and sizes. Co-located RGB camera and LIDAR sensors provide perception. The Astrobee robots will be capable of grasping each other in flight, to simulate orbital capture scenarios. The arm's end-effector module is swappable on-orbit, allowing guest scientists to add upgraded grippers, or even additional arm degrees of freedom. The design of the arm balances research capabilities with Astrobee's operational need to perch on ISS handrails to reduce power consumption. Basic arm functioning and grip strength were evaluated using an integrated Astrobee prototype riding on a low-friction air bearing

Leishmania Mitochondrial Peroxiredoxin Plays a Crucial Peroxidase-Unrelated Role during Infection: Insight into Its Novel Chaperone Activity

Two-cysteine peroxiredoxins are ubiquitous peroxidases that play various functions in cells. In Leishmania and related trypanosomatids, which lack catalase and selenium-glutathione peroxidases, the discovery of this family of enzymes provided the molecular basis for peroxide removal in these organisms. In this report the functional relevance of one of such enzymes, the mitochondrial 2-Cys peroxiredoxin (mTXNPx), was investigated along the Leishmania infantum life cycle. mTXNPx null mutants (mtxnpx−) produced by a gene replacement strategy, while indistinguishable from wild type promastigotes, were found unable to thrive in a murine model of infection. Unexpectedly, however, the avirulent phenotype of mtxnpx− was not due to lack of the peroxidase activity of mTXNPx as these behaved like controls when exposed to oxidants added exogenously or generated by macrophages during phagocytosis ex vivo. In line with this, mtxnpx− were also avirulent when inoculated into murine hosts unable to mount an effective oxidative phagocyte response (B6.p47phox−/− and B6.RAG2−/− IFN-γ−/− mice). Definitive conclusion that the peroxidase activity of mTXNPx is not required for parasite survival in mice was obtained by showing that a peroxidase-inactive version of this protein was competent in rescuing the non-infective phenotype of mtxnpx−. A novel function is thus proposed for mTXNPx, that of a molecular chaperone, which may explain the impaired infectivity of the null mutants. This premise is based on the observation that the enzyme is able to suppress the thermal aggregation of citrate synthase in vitro. Also, mtxnpx− were more sensitive than controls to a temperature shift from 25°C to 37°C, a phenotype reminiscent of organisms lacking specific chaperone genes. Collectively, the findings reported here change the paradigm which regards all trypanosomatid 2-Cys peroxiredoxins as peroxide-eliminating devices. Moreover, they demonstrate, for the first time, that these 2-Cys peroxiredoxins can be determinant for pathogenicity independently of their peroxidase activity

Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study

Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research