Dual-mode model predictive control of an omnidirectional wheeled inverted pendulum

This article describes the position and heading control of a novel form of omnidirectional wheeled inverted pendulum platform known as a Collinear Mecanum Drive. This concept uses four collinear Mecanum wheels to balance in a similar manner to a typical two-wheeled inverted pendulum, whilst also being able to simultaneously translate directly along its balance axis. Control is performed using a constrained time-optimal infinite horizon model predictive controller, with feasibility maintained across the full reference input set. Explored in this article is the derivation of the system dynamics model and controller, a systematic approach to selection of controller parameters and analysis of their effect on control performance and complexity, and an evaluation of the controller's efficacy in both simulation and on a real-world experimental prototype for simple and complex trajectories

Velocity constrained trajectory generation for a collinear Mecanum wheeled robot

While much research has been conducted into the generation of smooth trajectories for underactuated unstable aerial vehicles such as quadrotors, less attention has been paid to the application of the same techniques to ground based omnidirectional dynamically balancing robots. These systems have more control authority over their linear accelerations than aerial vehicles, meaning trajectory smoothness is less of a critical design parameter. However, when operating in indoor environments these systems must often adhere to relatively low velocity constraints, resulting in very conservative trajectories when enforced using existing trajectory optimisation methods. This paper makes two contributions; this gap is bridged by the extension of these existing methods to create a fast velocity constrained trajectory planner, with trajectory timing characteristics derived from the optimal minimum-time solution of a simplified acceleration and velocity constrained model. Next, a differentially flat model of an omnidirectional balancing robot utilizing a collinear Mecanum drive is derived, which is used to allow an experimental prototype of this configuration to smoothly follow these velocity constrained trajectories

Design and control of a novel omnidirectional dynamically balancing platform for remote inspection of confined and cluttered environments

Remote inspection is a long standing field of interest for robotics researchers, in which robots are used to undertake inspection tasks in environments too hazardous or inaccessible to be directly entered by a human. Recent advances in gridscale battery storage have created a new set of unique hazardous indoor spaces with characteristics unsuitable for the deployment of existing teleoperated inspection robots. This paper outlines the problems encountered in these new environments, analyses existing approaches to robotic platform design, and proposes a better suited novel platform design, based on a dynamically balancing arrangement of Mecanum wheels. Its inverse kinematic and dynamics models are developed, a proof of concept prototype is constructed, and a constrained predictive controller is derived from the developed model. Experimental results demonstrate the efficacy of this new concept

The Value of Rare Genetic Variation in the Prediction of Common Obesity in European Ancestry Populations

Polygenic risk scores (PRSs) aggregate the effects of genetic variants across the genome and are used to predict risk of complex diseases, such as obesity. Current PRSs only include common variants (minor allele frequency (MAF) ≥1%), whereas the contribution of rare variants in PRSs to predict disease remains unknown. Here, we examine whether augmenting the standard common variant PRS (PRScommon) with a rare variant PRS (PRSrare) improves prediction of obesity. We used genome-wide genotyped and imputed data on 451,145 European-ancestry participants of the UK Biobank, as well as whole exome sequencing (WES) data on 184,385 participants. We performed single variant analyses (for both common and rare variants) and gene-based analyses (for rare variants) for association with BMI (kg/m2), obesity (BMI ≥ 30 kg/m2), and extreme obesity (BMI ≥ 40 kg/m2). We built PRSscommon and PRSsrare using a range of methods (Clumping+Thresholding [C+T], PRS-CS, lassosum, gene-burden test). We selected the best-performing PRSs and assessed their performance in 36,757 European-ancestry unrelated participants with whole genome sequencing (WGS) data from the Trans-Omics for Precision Medicine (TOPMed) program. The best-performing PRScommon explained 10.1% of variation in BMI, and 18.3% and 22.5% of the susceptibility to obesity and extreme obesity, respectively, whereas the best-performing PRSrare explained 1.49%, and 2.97% and 3.68%, respectively. The PRSrare was associated with an increased risk of obesity and extreme obesity (ORobesity = 1.37 per SDPRS, Pobesity = 1.7x10-85; ORextremeobesity = 1.55 per SDPRS, Pextremeobesity = 3.8x10-40), which was attenuated, after adjusting for PRScommon (ORobesity = 1.08 per SDPRS, Pobesity = 9.8x10-6; ORextremeobesity= 1.09 per SDPRS, Pextremeobesity = 0.02). When PRSrare and PRScommon are combined, the increase in explained variance attributed to PRSrare was small (incremental Nagelkerke R2 = 0.24% for obesity and 0.51% for extreme obesity). Consistently, combining PRSrare to PRScommon provided little improvement to the prediction of obesity (PRSrare AUC = 0.591; PRScommon AUC = 0.708; PRScombined AUC = 0.710). In summary, while rare variants show convincing association with BMI, obesity and extreme obesity, the PRSrare provides limited improvement over PRScommon in the prediction of obesity risk, based on these large populations

Rare genetic variants explain missing heritability in smoking

Common genetic variants explain less variation in complex phenotypes than inferred from family-based studies, and there is a debate on the source of this ‘missing heritability’. We investigated the contribution of rare genetic variants to tobacco use with whole-genome sequences from up to 26,257 unrelated individuals of European ancestries and 11,743 individuals of African ancestries. Across four smoking traits, single-nucleotide-polymorphism-based heritability (hSNP2) was estimated from 0.13 to 0.28 (s.e., 0.10–0.13) in European ancestries, with 35–74% of it attributable to rare variants with minor allele frequencies between 0.01% and 1%. These heritability estimates are 1.5–4 times higher than past estimates based on common variants alone and accounted for 60% to 100% of our pedigree-based estimates of narrow-sense heritability (hped2, 0.18–0.34). In the African ancestry samples, hSNP2 was estimated from 0.03 to 0.33 (s.e., 0.09–0.14) across the four smoking traits. These results suggest that rare variants are important contributors to the heritability of smoking

Genetic determinants of telomere length from 109,122 ancestrally diverse whole-genome sequences in TOPMed

Genetic studies on telomere length are important for understanding age-related diseases. Prior GWASs for leukocyte TL have been limited to European and Asian populations. Here, we report the first sequencing-based association study for TL across ancestrally diverse individuals (European, African, Asian, and Hispanic/Latino) from the NHLBI Trans-Omics for Precision Medicine (TOPMed) program. We used whole-genome sequencing (WGS) of whole blood for variant genotype calling and the bioinformatic estimation of telomere length in n = 109,122 individuals. We identified 59 sentinel variants (p < 5 × 10−9) in 36 loci associated with telomere length, including 20 newly associated loci (13 were replicated in external datasets). There was little evidence of effect size heterogeneity across populations. Fine-mapping at OBFC1 indicated that the independent signals colocalized with cell-type-specific eQTLs for OBFC1 (STN1). Using a multi-variant gene-based approach, we identified two genes newly implicated in telomere length, DCLRE1B (SNM1B) and PARN. In PheWAS, we demonstrated that our TL polygenic trait scores (PTSs) were associated with an increased risk of cancer-related phenotypes

Ultrasonic stess monitoring in underground mining

Stress changes induced in a large (40 × 40 × 120 m) underground support pillar by mining development have been monitored over a period of 2 yr in the 1100 copper orebody at Mt Isa Mine, Australia, using an ultrasonic stress monitoring device (USMD). Results are compared with estimates from in situ absolute stress measurements and with continuous strain recordings at a nearby site. Sensitivity to deviatoric stress changes of 0.01 MPa has been achieved. Propagation of stress relief cycles through the pillar were observed, and a number of creep events were documented. Many events of potential interest detechable in continuous strain measurements were examined in the stress domain. The large increases in vertical stress field expected as the pillar was progressively isolated did not occur since the pillar yielded by shear on pre-existing fractures. Most of the deformation of the pillar which was observed in strain records occurred without significant stress change demonstrating the need for simultaneous stress and strain data. Stress relief events propagate slowly through a rock mass on time scales of several days

Piezomagnetic monitoring in the South Pacific region

Data from an array of piezomagnetic stations in the South Pacific Islands indicate that noise limitations on piezomagnetic stress monitoring reported for California (Mueller and Johnston, 1981;Johnstonet al., 1984) are probably pessimistic since they seem to include significant diurnal residual. Raw station differences could be significant at the 1.0 nT level out to distances of several hundred kilometres. Two large earthquakes have occurred within the network, and no coseismic anomalies were observed. However, changes in observed magnetic field for several stations within 200 km of the earthquakes indicate that stress propagation effects are observable prior to the events, and that these effects dominate the simple elastic effects previously investigated which accompany the stress drops for moderate to large earthquakes

Simultaneous monitoring of stress and strain in massive rock

Continuous measurements of ultrasonic pulse transit times over 10 m baselines between fixed points in each of three mutually perpendicular directions are made routinely in solid rock. The most significant current experiment is in a large underground support pillar (30 m×30 m×200 m high) 700 m below ground level in an active mine. Velocity measurements to a precision of 2 parts in 106 allow stress changes of order 1 kPa to be monitored, and compared with simultaneous strain measurements (for which a capacitance strain sensor is used) to examine the mechanisms of large scale stress relief processes. Characteristic stress relief cycles (of magnitude 200-3000 kPa) are found to migrate through the pillar as impressed loads are accommodated by the rock mass