Safe Trajectory Sampling in Model-Based Reinforcement Learning

Model-based reinforcement learning aims to learn a policy to solve a target task by leveraging a learned dynamics model. This approach, paired with principled handling of uncertainty allows for data-efficient policy learning in robotics. However, the physical environment has feasibility and safety constraints that need to be incorporated into the policy before it is safe to execute on a real robot. In this work, we study how to enforce the aforementioned constraints in the context of model-based reinforcement learning with probabilistic dynamics models. In particular, we investigate how trajectories sampled from the learned dynamics model can be used on a real robot, while fulfilling user-specified safety requirements. We present a model-based reinforcement learning approach using Gaussian processes where safety constraints are taken into account without simplifying Gaussian assumptions on the predictive state distributions. We evaluate the proposed approach on different continuous control tasks with varying complexity and demonstrate how our safe trajectory-sampling approach can be directly used on a real robot without violating safety constraints

Improving quality of life through the routine use of the patient concerns inventory for head and neck cancer patients: main results of a cluster preference randomised controlled trial

Funding: UK National Institute for Health Research (NIHR) under its Research for Patient Benefit (RfPB) Programme (Grant Reference Number PB-PG-0215-36047).Purpose The patient concerns inventory (PCI) is a prompt list allowing head and neck cancer (HNC) patients to discuss issues that otherwise might be overlooked. This trial evaluated the effectiveness of using the PCI at routine outpatient clinics for one year after treatment on health-related QOL (HRQOL). Methods   A pragmatic cluster preference randomised control trial with 15 consultants, 8 ‘using’ and 7 ‘not using’ the PCI intervention. Patients treated with curative intent (all sites, disease stages, treatments) were eligible. Results   Consultants saw a median (inter-quartile range) 16 (13–26) patients, with 140 PCI and 148 control patients. Of the pre-specified outcomes, the 12-month results for the mean University of Washington Quality of Life (UW-QOLv4) social-emotional subscale score suggested a small clinical effect of intervention of 4.6 units (95% CI 0.2, 9.0), p = 0.04 after full adjustment for pre-stated case-mix. Results for UW-QOLv4 overall quality of life being less than good at 12 months (primary outcome) also favoured the PCI with a risk ratio of 0.83 (95% CI 0.66, 1.06) and absolute risk 4.8% (− 2.9%, 12.9%) but without achieving statistical significance. Other non-a-priori analyses, including all 12 UWQOL domains and at consultant level also suggested better HRQOL with PCI. Consultation times were unaffected and the number of items selected decreased over time. Conclusion   This novel trial supports the integration of the PCI approach into routine consultations as a simple low-cost means of benefiting HNC patients. It adds to a growing body of evidence supporting the use of patient prompt lists more generally.Publisher PDFPeer reviewe

Observerless Scheme for Sensorless Speed Control of PMSM Using Direct Torque Control Method With LP Filter

In this study, direct torque control (DTC) of a permanent magnet synchronous motor is realized with a sensorless speed control technique without using an observer. Space vector pulse width modulation (SVPWM) technique is applied in order to determine the switching sequence of the voltage source inverter. Torque and flux, the main variables of the DTC, are estimated by using the mathematical model of the motor. Estimated torque and flux values are compared with their references in every control cycle. Then, according to the torque and flux demand, the voltage vector is constituted. In the proposed control scheme, speed is estimated by using flux calculations and a PI controller is used to process the torque and flux errors. Furthermore, a low-pass (LP) filter is implemented within the proposed system for voltage and current harmonics suppression. The results proved that proposed scheme for the DTC provides the speed control under various torque demands without employing a sensor. The proposed system performs very well for a sensorless operation and effectively eliminates the harmonics due to the LP filter

A prevalence study of restless legs syndrome in Turkish children and adolescents

Objective: To determine the prevalence of restless legs syndrome (RLS) in Turkish school children and adolescents during the past 12 months. Methods: A cross-sectional population study conducted in three primary and four high schools was randomly selected in the Umraniye district of Istanbul. In the first step, a 7-item questionnaire including pediatric diagnostic criteria of RLS proposed by the International Restless Legs Study Group was given to 4346 students aged from 10 to 19 years in the classroom. Candidates for definite RLS or probable RLS were selected by a face-to-face interview done by an expert. In the second step, a 58-item questionnaire was administered to the families of the selected subjects. The questionnaire aimed to survey family history, parent's awareness, and their behaviors for seeking treatment, as well as the differential diagnosis and comorbid disorders of RLS. Results: Definite RLS was diagnosed in 119 (2.74%) of the subjects and was more prevalent in females (3.42%) compared to males (2.04%) (p = 0.007). A family history of RLS was positive in 15.8% of the first-degree relatives of those 119 subjects. Less than half of the parents (45%) were aware of their children's symptoms and only 10.9% of these parents consulted medical centers. The most prevalent symptoms of sleep disturbances were restless sleep (28.6%) and daytime sleepiness (21%). Growing pains were reported in 54.5% of the 119 subjects with definite RLS. Symptoms of Attention-Deficit/Hyperactivity Disorder were found in 15.3% of the 119 subjects. Conclusions: RLS is prevalent in Turkish children and adolescents although family awareness of RLS is relatively low. (C) 2011 Elsevier B.V. All rights reserved