Observer-based output-feedback control to eliminate torsional drill-string vibrations

Torsional stick-slip vibrations decrease the performance and reliability of drilling systems used for the exploration of energy and mineral resources. In this work, we present the design of a nonlinear observer-based output-feedback control strategy to eliminate these vibrations. We apply the controller to a drill-string model based on a real-life rig. Conditions, guaranteeing asymptotic stability of the desired equilibrium, corresponding to nominal drilling operation, are presented. The proposed control strategy has a significant advantage over existing vibration control systems in current drilling rigs as it only requires surface measurements instead of expensive down-hole measurements and can handle multiple modes of torsional vibration. Case study results using the proposed control strategy show that stick-slip oscillations can indeed be eliminated in realistic drilling scenarios

Stability of networked control systems with large delays

Abstract — We consider the stabilization problem for Net-worked Control Systems (NCSs) with uncertain, time-varying network-induced delays and a bounded number of subsequent packet dropouts. A discrete-time model, describing a NCS with packet dropouts and time-varying delays, that can be both smaller and larger than the sampling interval, is presented. Based on this NCS model sufficient LMI conditions are pro-posed for the stability analysis and controller synthesis problem for two different controllers, i.e. a feedback controller that depends on both the state and the past control inputs and a state-feedback controller. The applicability of both controllers is compared. Moreover, the stability and controller synthesis LMIs allow for a performance analysis in terms of a lower bound for the transient decay rate of the response. The results are illustrated by application to a typical motion control example. I

Playing for cognition: investigating the feasibility and user experience of a virtual reality serious game for cognitive assessment in children with congenital heart disease

Background In order to facilitate the development and implementation of innovative technology in clinical practice, it is important to understand the user experience of end-users. Virtual Reality (VR) offers the possibility to assess cognitive functioning in a dynamic environment that simulates real-world situations. The purpose of this cross-sectional study was to investigate the feasibility of a VR Serious Game for cognitive assessment in school-aged children with congenital heart disease (CHD). The sub-aims were two-fold: (1) to objectively evaluate the feasibility of the VR Serious Game in children with CHD in comparison to typically developing (TD) children and (2) to explore the user experience of both groups following their interaction with the VR Serious Game. Results A total of 101 children participated in this study; 98 children were included in the final analysis (CHD: n = 54; TD: n = 47). The VR Serious Game appeared feasible for both children with CHD and TD children, with 88% children completing the innovative VR assessment without encountering any issues. There were no discernible differences in completion rates between groups. Children with CHD reported significantly lower scores than TD children on three user experience scales: Engagement, Flow and Presence. Nonetheless, the scores for Engagement and Flow were still considered "moderate to good". Both groups reported minimal adverse physiological reactions. Conclusions The findings suggested that the VR Serious Game was feasible for children with CHD and that the user experience was positive. Future research should investigate the effectiveness of the VR Serious Game compared with a conventional or digital neuropsychological assessment, prioritising the development of novel outcome measures that can better estimate and explain the impact of cognitive impairment on daily functioning

Stability analysis of networked control systems using a switched linear systems approach.

Abstract. In this paper, we study the stability of Networked Control Systems (NCSs) that are subject to time-varying transmission intervals and communication constraints in the sense that, per transmission, only one node can access the network and send its information. The order in which nodes send their information is dictated by a network protocol, such as the well-known Round Robin (RR) or Try-Once-Discard (TOD) protocol. Focussing on linear plants and linear continuous-time or discrete-time controllers, we model the NCS with time-varying transmission intervals as a discrete-time switched linear uncertain system. We obtain bounds for the allowable range of transmission intervals in terms of both minimal and maximal allowable transmission intervals. Hereto, a new convex overapproximation of the uncertain switched system is proposed, using a polytopic system with norm-bounded uncertainty, and new stability results for this class of hybrid systems are developed. On the benchmark example of a batch reactor, we explicitly exploit the linearity of the system, leading to a significant reduction in conservatism with respect to the existing approaches

Being Transparent About Brilliant Failures:An Attempt to Use Real-World Data in a Disease Model for Patients with Castration-Resistant Prostate Cancer

Background: Real-world disease models spanning multiple treatment lines can provide insight into the (cost) effectiveness of treatment sequences in clinical practice. Objective: Our objective was to explore whether a disease model based solely on real-world data (RWD) could be used to estimate the effectiveness of treatments for patients with castration-resistant prostate cancer (CRPC) that could then be suitably used in a cost-effectiveness analysis. Methods: We developed a patient-level simulation model using patient-level data from the Dutch CAPRI registry as input parameters. Time to event (TTE) and overall survival (OS) were estimated with multivariate regression models, and type of event (i.e., next treatment or death) was estimated with multivariate logistic regression models. To test internal validity, TTE and OS from the simulation model were compared with the observed outcomes in the registry. Results: Although patient characteristics and survival outcomes of the simulated data were comparable to those in the observed data (median OS 20.6 vs. 19.8 months, respectively), the disease model was less accurate in estimating differences between treatments (median OS simulated vs. observed population: 18.6 vs. 17.9 [abiraterone acetate plus prednisone], 24.0 vs. 25.0 [enzalutamide], 20.2 vs. 18.7 [docetaxel], and 20.0 vs. 23.8 months [radium-223]). Conclusions: Overall, the disease model accurately approximated the observed data in the total CRPC population. However, the disease model was unable to predict differences in survival between treatments due to unobserved differences. Therefore, the model is not suitable for cost-effectiveness analysis of CRPC treatment. Using a combination of RWD and data from randomised controlled trials to estimate treatment effectiveness may improve the model

Efficacy of serology driven “test and treat strategy” for eradication of H. pylori in patients with rheumatic disease in the Netherlands

The treatment of choice of H. pylori infections is a 7-day triple-therapy with a proton pump inhibitor (PPI) plus amoxicillin and either clarithromycin or metronidazole, depending on local antibiotic resistance rates. The data on efficacy of eradication therapy in a group of rheumatology patients on long-term NSAID therapy are reported here. This study was part of a nationwide, multicenter RCT that took place in 2000–2002 in the Netherlands. Patients who tested positive for H. pylori IgG antibodies were included and randomly assigned to either eradication PPI-triple therapy or placebo. After completion, follow-up at 3 months was done by endoscopy and biopsies were sent for culture and histology. In the eradication group 13% (20/152, 95% CI 9–20%) and in the placebo group 79% (123/155, 95% CI 72–85%) of the patients were H. pylori positive by histology or culture. H. pylori was successfully eradicated in 91% of the patients who were fully compliant to therapy, compared to 50% of those who were not (difference of 41%; 95% CI 18–63%). Resistance percentages found in isolates of the placebo group were: 4% to clarithromycin, 19% to metronidazole, 1% to amoxicillin and 2% to tetracycline

Real-world Outcomes of Sequential Androgen-receptor Targeting Therapies with or Without Interposed Life-prolonging Drugs in Metastatic Castration-resistant Prostate Cancer:Results from the Dutch Castration-resistant Prostate Cancer Registry

BACKGROUND: Cross resistance between androgen-receptor targeting therapies (ARTs) (abiraterone acetate plus prednisone [ABI+P] or enzalutamide [ENZ]) for treatment of metastatic castration-resistant prostate cancer (mCRPC) may affect responses to second ART (ART2). OBJECTIVE: To establish treatment duration and prostate-specific antigen (PSA) response of ART2 in real-world mCRPC patients treated with or without other life-prolonging drugs (LPDs; ie, docetaxel, cabazitaxel, or radium-223) between ART1 and ART2. DESIGN, SETTING, AND PARTICIPANTS: Castration-resistant prostate cancer patients, diagnosed between 2010 and 2016 were retrospectively registered in Castration-resistant Prostate Cancer Registry (CAPRI). Patients treated with both ARTs were clustered into two subgroups: ART1>ART2 or ART1>LPD>ART2. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Outcomes were ≥50% PSA response and treatment duration of ART2. Descriptive statistics and binary logistic regression after multiple imputations were performed. RESULTS AND LIMITATIONS: A total of 273 patients were included with a median follow-up of 8.4 mo from ART2. Patients with ART1>ART2 were older and had favourable prognostic characteristics at ART2 baseline compared with patients with ART1>LPD>ART2. No differences between ART1>ART2 and ART1>LPD>ART2 were found in PSA response and treatment duration. Multivariate analysis suggested that PSA response of ART2 was less likely in patients with visceral metastases (odds ratio [OR] 0.143, p=0.04) and more likely in patients with a relatively longer duration of androgen-deprivation treatment (OR 1.028, p=0.01) and with ABI + P before ENZ (OR 3.192, p=0.02). A major limitation of this study was missing data, a common problem in retrospective observational research. CONCLUSIONS: The effect of ART2 seems to be low, with a low PSA response rate and a short treatment duration irrespective of interposed chemotherapy or radium-223, especially in patients with short time on castration, visceral disease, and ENZ before ABI+P. PATIENT SUMMARY: We observed no differences in outcomes of patients treated with sequential abiraterone acetate plus prednisone (ABI+P) and enzalutamide (ENZ) with or without interposed chemotherapy or radium-223. In general, outcomes were lower than those in randomised trials, questioning the additional effect of second treatment with ABI+P or ENZ in daily practice

Differences in Trial and Real-world Populations in the Dutch Castration-resistant Prostate Cancer Registry

__Background:__ Trials in castration-resistant prostate cancer (CRPC) treatment have shown improved outcomes, including survival. However, as trial populations are selected, results may not be representative for the real-world population. The aim of this study was to assess the differences between patients treated in a clinical trial versus standard care during the course of CRPC in a real-world CRPC population. __Design, setting, and participants:__ Castration-resistant Prostate Cancer Registry is a population-based, observational, retrospective registry. CRPC patients from 20 hospitals in the Netherlands have been included from 2010 to 2013. __Outcome measurements and statistical analysis:__ Baseline characteristics, systemic treatment, and overall survival were the main outcomes. Descriptive statistics, multivariate Cox regression, and multiple imputations with the Monte Carlo Markov Chain method were used. __Results and limitations:__ In total, 1524 patients were enrolled of which 203 patients had participated in trials at any time. The median follow-up period was 23 mo. Patients in the trial group were significantly younger and had less comorbidities. Docetaxel treatment was more freque