Control Space Reduction and Real-Time Accurate Modeling of Continuum Manipulators Using Ritz and Ritz-Galerkin Methods

To address the challenges with real-time accurate modeling of multisegment continuum manipulators in the presence of significant external and body loads, we introduce a novel series solution for variable-curvature Cosserat rod static and Lagrangian dynamic methods. By combining a modified Lagrange polynomial series solution, based on experimental observations, with Ritz and Ritz-Galerkin methods, the infinite modeling state space of a continuum manipulator is minimized to geometrical position of a handful of physical points (in our case two). As a result, a unified easy to implement vector formalism is proposed for the nonlinear impedance and configuration control. We showed that by considering the mechanical effects of highly elastic axial deformation, the model accuracy is increased up to 6%. The proposed model predicts experimental results with 6%-8% (4-6 mm) mean error for the Ritz-Galerkin method in static cases and 16%-20% (12-14 mm) mean error for the Ritz method in dynamic cases, in planar and general three-dimensional motions. Comparing to five different models in the literature, our approximate solution is shown to be more accurate with the smallest possible number of modeling states and suitable for real-time modeling, observation, and control applications

Paradoxical Emboli Secondary to Hepatic Pathology: Common or Coincidental?

Paradoxical cerebral emboli from cardiac and pulmonary sources are well described in the peer-reviewed literature. We outline a case with a hepatic etiology and describe diagnostic and management options. Though this paper represents the first documentation of such, we believe that transpulmonary shunting with concurrent paradoxical cerebral microemboli is more prevalent than recognized. We introduce this case report to compel practitioners to consider paradoxical emboli in selected cirrhotic patients since it can often be difficult to elicit subtle neurologic changes on clinical examination of patients with end stage liver disease

Impacts of removing badgers on localised counts of hedgehogs

This is the final version of the article. Available from Public Library of Science via the DOI in this record.Experimental evidence of the interactions among mammalian predators that eat or compete with one another is rare, due to the ethical and logistical challenges of managing wild populations in a controlled and replicated way. Here, we report on the opportunistic use of a replicated and controlled culling experiment (the Randomised Badger Culling Trial) to investigate the relationship between two sympatric predators: European badgers Meles meles and western European hedgehogs Erinaceus europaeus. In areas of preferred habitat (amenity grassland), counts of hedgehogs more than doubled over a 5-year period from the start of badger culling (from 0.9 ha-1 pre-cull to 2.4 ha-1 post-cull), whereas hedgehog counts did not change where there was no badger culling (0.3-0.3 hedgehogs ha-1). This trial provides experimental evidence for mesopredator release as an outcome of management of a top predator.The study was funded by the United Kingdom Government’s Department for Environment, Food and Rural Affairs (http://www.defra.gov.uk). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Modelling the Interplay between Lifestyle Factors and Genetic Predisposition on Markers of Type 2 Diabetes Mellitus Risk

The risk of developing type 2 diabetes mellitus (T2DM) is determined by a complex interplay involving lifestyle factors and genetic predisposition. Despite this, many studies do not consider the relative contributions of this complex array of factors to identify relationships which are important in progression or prevention of complex diseases. We aimed to describe the integrated effect of a number of lifestyle changes (weight, diet and physical activity) in the context of genetic susceptibility, on changes in glycaemic traits in overweight or obese participants following 12-months of a weight management programme. A sample of 353 participants from a behavioural weight management intervention were included in this study. A graphical Markov model was used to describe the impact of the intervention, by dividing the effects into various pathways comprising changes in proportion of dietary saturated fat, physical activity and weight loss, and a genetic predisposition score (T2DM-GPS), on changes in insulin sensitivity (HOMA-IR), insulin secretion (HOMA-B) and short and long term glycaemia (glucose and HbA1c). We demonstrated the use of graphical Markov modelling to identify the importance and interrelationships of a number of possible variables changed as a result of a lifestyle intervention, whilst considering fixed factors such as genetic predisposition, on changes in traits. Paths which led to weight loss and change in dietary saturated fat were important factors in the change of all glycaemic traits, whereas the T2DM-GPS only made a significant direct contribution to changes in HOMA-IR and plasma glucose after considering the effects of lifestyle factors. This analysis shows that modifiable factors relating to body weight, diet, and physical activity are more likely to impact on glycaemic traits than genetic predisposition during a behavioural intervention

Stiffness Imaging With a Continuum Appendage: Real-Time Shape and Tip Force Estimation From Base Load Readings

In this paper, we propose benefiting from load readings at the base of a continuum appendage for real-time forward integration of Cosserat rod model with application in configuration and tip load estimation. The application of this method is successfully tested for stiffness imaging of a soft tissue, using a 3-DOF hydraulically actuated braided continuum appendage. Multiple probing runs with different actuation pressures are used for mapping the tissue surface shape and directional linear stiffness, as well as detecting non-homogeneous regions, e.g. a hard nodule embedded in a soft silicon tissue phantom. Readings from a 6-axis force sensor at the tip is used for comparison and verification. As a result, the tip force is estimated with 0.016-0.037 N (7-20%) mean error in the probing and 0.02-0.1 N (6-12%) in the indentation direction, 0.17 mm (14%) mean error is achieved in estimating the surface profile, and 3.4-15 [N/m] (10-16%) mean error is observed in evaluating tissue directional stiffness, depending on the appendage actuation. We observed that if the appendage bends against the slider motion (toward the probing direction), it provides better horizontal stiffness estimation and better estimation in the perpendicular direction is achieved when it bends toward the slider motion (against the probing direction). In comparison with a rigid probe, ≈ 10 times smaller stiffness and ≈ 7 times larger mean standard deviation values were observed, suggesting the importance of a probe stiffness in estimation the tissue stiffness

UHRF: spectral resolution to the limit

Until recently the study of cool clouds of interstellar matter had been limited by the relatively low spectral resolutions provided by existing spectrographs. The Ultra-High-Resolution Facility (UHRF) recently commissioned at the Anglo-Australian Telescope has changed dramatically this panorama by delivering for the first time resolutions approaching one million, near the diffraction limit of the largest echelle gratings available. The instrument shares the east coude room with the University College London Echelle Spectrograph, in what is now one of the most powerful spectrographic installations worldwide. This contribution describes the characteristics of the UHRF, including its design, manufacture, testing, and commissioning. The UHRF incorporates a novel image slicer (described elsewhere in these proceedings), which allows ultra-high-resolution observations on faint objects. Astrophysical results from the first observing runs are presented to demonstrate the UHRF performance in both resolution and throughput

Three-Dimensional-Printable Thermoactive Helical Interface With Decentralized Morphological Stiffness Control for Continuum Manipulators

We present a three-dimensional (3-D)-printable thermoactive scale jamming interface as a new way to control a continuum manipulator dexterity by taking inspiration from the helical arrangement of fish scales. A highly articulated helical interface is 3-D-printed with thermoactive functionally graded joints using a conventional 3-D printing device that utilizes UV curable acrylic plastic and hydroxylated wax as the primary and supporting material. The joint compliance is controlled by regulating wax temperature in phase transition. Empirical feed-forward control relations are identified through comprehensive study of the wax melting profile and actuation scenarios for different shaft designs to achieve desirable repeatability and response time. A decentralized control approach is employed by relating the mathematical terms of the Cosserat beam method to their morphological counterparts in which the manipulator local anisotropic stiffness is controlled based on the local stress and strain information. As a result, a minimalistic central controller is designed in which the joints' thermomechanical states are observed using a morphological observer, an external fully monitored replica of the observed system with the same inputs. Preliminary results for passive shape adaptation, geometrical disturbance rejection, and task space anisotropic stiffness control are reported by integrating the interface on a continuum manipulator

TMTDyn: A Matlab package for modeling and control of hybrid rigid-continuum robots based on discretized lumped systems and reduced-order models

A reliable, accurate, and yet simple dynamic model is important to analyzing, designing, and controlling hybrid rigid–continuum robots. Such models should be fast, as simple as possible, and user-friendly to be widely accepted by the ever-growing robotics research community. In this study, we introduce two new modeling methods for continuum manipulators: a general reduced-order model (ROM) and a discretized model with absolute states and Euler–Bernoulli beam segments (EBA). In addition, a new formulation is presented for a recently introduced discretized model based on Euler–Bernoulli beam segments and relative states (EBR). We implement these models in a Matlab software package, named TMTDyn, to develop a modeling tool for hybrid rigid–continuum systems. The package features a new high-level language (HLL) text-based interface, a CAD-file import module, automatic formation of the system equation of motion (EOM) for different modeling and control tasks, implementing Matlab C-mex functionality for improved performance, and modules for static and linear modal analysis of a hybrid system. The underlying theory and software package are validated for modeling experimental results for (i) dynamics of a continuum appendage, and (ii) general deformation of a fabric sleeve worn by a rigid link pendulum. A comparison shows higher simulation accuracy (8–14% normalized error) and numerical robustness of the ROM model for a system with a small number of states, and computational efficiency of the EBA model with near real-time performances that makes it suitable for large systems. The challenges and necessary modules to further automate the design and analysis of hybrid systems with a large number of states are briefly discussed