Fast Manipulability Maximization Using Continuous-Time Trajectory Optimization

A significant challenge in manipulation motion planning is to ensure agility in the face of unpredictable changes during task execution. This requires the identification and possible modification of suitable joint-space trajectories, since the joint velocities required to achieve a specific endeffector motion vary with manipulator configuration. For a given manipulator configuration, the joint space-to-task space velocity mapping is characterized by a quantity known as the manipulability index. In contrast to previous control-based approaches, we examine the maximization of manipulability during planning as a way of achieving adaptable and safe joint space-to-task space motion mappings in various scenarios. By representing the manipulator trajectory as a continuous-time Gaussian process (GP), we are able to leverage recent advances in trajectory optimization to maximize the manipulability index during trajectory generation. Moreover, the sparsity of our chosen representation reduces the typically large computational cost associated with maximizing manipulability when additional constraints exist. Results from simulation studies and experiments with a real manipulator demonstrate increases in manipulability, while maintaining smooth trajectories with more dexterous (and therefore more agile) arm configurations.Comment: In Proceedings of the IEEE International Conference on Intelligent Robots and Systems (IROS'19), Macau, China, Nov. 4-8, 201

Learning from Guided Play: Improving Exploration for Adversarial Imitation Learning with Simple Auxiliary Tasks

Adversarial imitation learning (AIL) has become a popular alternative to supervised imitation learning that reduces the distribution shift suffered by the latter. However, AIL requires effective exploration during an online reinforcement learning phase. In this work, we show that the standard, naive approach to exploration can manifest as a suboptimal local maximum if a policy learned with AIL sufficiently matches the expert distribution without fully learning the desired task. This can be particularly catastrophic for manipulation tasks, where the difference between an expert and a non-expert state-action pair is often subtle. We present Learning from Guided Play (LfGP), a framework in which we leverage expert demonstrations of multiple exploratory, auxiliary tasks in addition to a main task. The addition of these auxiliary tasks forces the agent to explore states and actions that standard AIL may learn to ignore. Additionally, this particular formulation allows for the reusability of expert data between main tasks. Our experimental results in a challenging multitask robotic manipulation domain indicate that LfGP significantly outperforms both AIL and behaviour cloning, while also being more expert sample efficient than these baselines. To explain this performance gap, we provide further analysis of a toy problem that highlights the coupling between a local maximum and poor exploration, and also visualize the differences between the learned models from AIL and LfGP.Comment: In IEEE Robotics and Automation Letters (RA-L) and presented at the IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS'23), Detroit, MI, USA, Oct. 1-5, 2023. arXiv admin note: substantial text overlap with arXiv:2112.0893

Learning Sequential Latent Variable Models from Multimodal Time Series Data

Sequential modelling of high-dimensional data is an important problem that appears in many domains including model-based reinforcement learning and dynamics identification for control. Latent variable models applied to sequential data (i.e., latent dynamics models) have been shown to be a particularly effective probabilistic approach to solve this problem, especially when dealing with images. However, in many application areas (e.g., robotics), information from multiple sensing modalities is available -- existing latent dynamics methods have not yet been extended to effectively make use of such multimodal sequential data. Multimodal sensor streams can be correlated in a useful manner and often contain complementary information across modalities. In this work, we present a self-supervised generative modelling framework to jointly learn a probabilistic latent state representation of multimodal data and the respective dynamics. Using synthetic and real-world datasets from a multimodal robotic planar pushing task, we demonstrate that our approach leads to significant improvements in prediction and representation quality. Furthermore, we compare to the common learning baseline of concatenating each modality in the latent space and show that our principled probabilistic formulation performs better. Finally, despite being fully self-supervised, we demonstrate that our method is nearly as effective as an existing supervised approach that relies on ground truth labels.Comment: In: Petrovic, I., Menegatti, E., Markovi\'c, I. (eds) Intelligent Autonomous Systems 17. IAS 2022. Lecture Notes in Networks and Systems, vol 577. Springer, Cha

Revision of the " Chloritisdelibrata (Benson, 1836)" group (Gastropoda, Stylommatophora, Camaenidae).

Chloritisdelibrata (Benson, 1836), known from northeastern India, was believed to have three varietal forms, sometimes mentioned as subspecies: C.delibratavar.khasiensis (Nevill, 1877) and C.delibratavar.fasciata (Godwin-Austen, 1875) from the Khasi Hills, India, and C.delibratavar.procumbens (Gould, 1844) from Dawei in Myanmar. The reproductive anatomy of the latter form is known and does not match with those of any continental camaenid genera, but does with that of the newly examined Chloritisplatytropis Möllendorff, 1894 from Thailand. The latter species is conchologically similar to Bouchetcamaenahuberi Thach, 2018 (synonym of Helixfouresi Morlet, 1886), which is the type species of the genus Bouchetcamaena Thach, 2018. Thus, Bouchetcamaena can provisionally host the entire Chloritisdelibrata -group with the exception of var. fasciata, which is transferred to Burmochloritis Godwin-Austen, 1920 due to the multiple reddish bands on its shell. The examination of shells deposited in the Natural History Museum, London revealed that seven morphologically distinguishable forms are present, which are accepted here as representing distinct species. Four new species are described from India: Bouchetcamaenafoveata Páll-Gergely sp. nov., B.fusca Páll-Gergely sp. nov., B.raripila Páll-Gergely sp. nov., and B.subdelibrata Páll-Gergely sp. nov

Self-Calibration of Mobile Manipulator Kinematic and Sensor Extrinsic Parameters Through Contact-Based Interaction

We present a novel approach for mobile manipulator self-calibration using contact information. Our method, based on point cloud registration, is applied to estimate the extrinsic transform between a fixed vision sensor mounted on a mobile base and an end effector. Beyond sensor calibration, we demonstrate that the method can be extended to include manipulator kinematic model parameters, which involves a non-rigid registration process. Our procedure uses on-board sensing exclusively and does not rely on any external measurement devices, fiducial markers, or calibration rigs. Further, it is fully automatic in the general case. We experimentally validate the proposed method on a custom mobile manipulator platform, and demonstrate centimetre-level post-calibration accuracy in positioning of the end effector using visual guidance only. We also discuss the stability properties of the registration algorithm, in order to determine the conditions under which calibration is possible.Comment: In Proceedings of the IEEE International Conference on Robotics and Automation (ICRA'18), Brisbane, Australia, May 21-25, 201

Systematics of the family Plectopylidae in Vietnam with additional information on Chinese taxa (Gastropoda, Pulmonata, Stylommatophora)

Vietnamese species from the family Plectopylidae are revised based on the type specimens of all known taxa, more than 600 historical non-type museum lots, and almost 200 newly-collected samples. Altogether more than 7000 specimens were investigated. The revision has revealed that species diversity of the Vietnamese Plectopylidae was previously overestimated. Overall, thirteen species names (anterides Gude, 1909, bavayi Gude, 1901, congesta Gude, 1898, fallax Gude, 1909, gouldingi Gude, 1909, hirsuta Möllendorff, 1901, jovia Mabille, 1887, moellendorffi Gude, 1901, persimilis Gude, 1901, pilsbryana Gude, 1901, soror Gude, 1908, tenuis Gude, 1901, verecunda Gude, 1909) were synonymised with other species. In addition to these, Gudeodiscus hemmeni sp. n. and G. messageri raheemi ssp. n. are described from north-western Vietnam. Sixteen species and two subspecies are recognized from Vietnam. The reproductive anatomy of eight taxa is described. Based on anatomical information, Halongella gen. n. is erected to include Plectopylis schlumbergeri and P. fruhstorferi. Additionally, the genus Gudeodiscus is subdivided into two subgenera (Gudeodiscus and Veludiscus subgen. n.) on the basis of the morphology of the reproductive anatomy and the radula. The Chinese G. phlyarius werneri Páll-Gergely, 2013 is moved to synonymy of G. phlyarius. A spermatophore was found in the organ situated next to the gametolytic sac in one specimen. This suggests that this organ in the Plectopylidae is a diverticulum. Statistically significant evidence is presented for the presence of calcareous hook-like granules inside the penis being associated with the absence of embryos in the uterus in four genera. This suggests that these probably play a role in mating periods before disappearing when embryos develop. Sicradiscus mansuyi is reported from China for the first time.ArticleZOOKEYS. (473):1-118 (2015)journal articl

Anti-cholinergic burden and patient related clinical outcomes in an emergency general surgical setting

We acknowledge the support of the National Institute for Health Research (NIHR) Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King’s College London (BC).Peer reviewedPublisher PD

FMALE score: combining practical risk scales to improve preoperative predictive accuracy in emergency general surgery: a multi-centre prospective cohort study

Our increasingly aging population is associated with older people being admitted to surgical wards at a rate surpassing population growth. 1 Although frailty is not exclusive to older adults, its prevalence is positively associated with age. 2 Hewitt et al. observed frailty to independently predict increased length of hospital stay (LOS), 30-day and 90-day mortality for adults aged ≥65 years admitted to emergency general surgery (EGS). 3 Recent evidence has shown that the association between frailty and poor outcomes, is not limited to older adults, but extends to all adult EGS patients. 4 Although risk stratification tools have been derived for EGS patients, none have included a measure for frailty. 5 Previously, Ablett et al. suggested the MALE score to identify older patients at risk of poorer outcomes who may benefit from comprehensive geriatric assessment based on four characteristics obtained at the point of care: Male, Anaemic, Low albumin, and age Eight-five and over. 6 We aimed to investigate whether the accuracy of MALE score could be augmented, through incorporating physical frailty defined by the Clinical Frailty Scale (CFS), and applied to all EGS adults

SHARP risk score: a predictor of poor outcomes in adults admitted for emergency general surgery: a prospective cohort study

Purpose Post-operative complications following emergency abdominal surgery are associated with significant morbidity and mortality. Despite the knowledge of prognostic factors associated with poor surgical outcomes; few have described risks of poor outcomes based on admission information in acute surgical setting. We aimed to derive a simple, point-of-care risk scale that predicts adults with increased risk of poor outcomes. Methods We used data from an international multi-centre prospective cohort study. The effect of characteristics; age, hypoalbuminaemia, anaemia, renal insufficiency and polypharmacy on 90-day mortality was examined using fully adjusted multivariable models. For our secondary outcome we aimed to test whether these characteristics could be combined to predict poor outcomes in adults undergoing emergency general surgery. Subsequently, the impact of incremental increase in derived SHARP score on outcomes was assessed. Results The cohort consisted of 419 adult patients between the ages of 16–94 years (median 52; IQR(39) consecutively admitted to five emergency general surgical units across the United Kingdom and one in Ghent, Belgium. In fully adjusted models the aforementioned characteristics; were associated with 90-day mortality. SHARP score was associated with higher odds of mortality in adults who underwent emergency general surgery, with a SHARP score of five also being associated with an increased length of hospital stay. Conclusions SHARP risk score is a simple prognostic tool, using point-of-care information to predict poor outcomes in patients undergoing emergency general surgery. This information may be used to improve management plans and aid clinicians in delivering more person-centred care. Further validation studies are required to prove its utility