Multi-Robot Transfer Learning: A Dynamical System Perspective

Multi-robot transfer learning allows a robot to use data generated by a second, similar robot to improve its own behavior. The potential advantages are reducing the time of training and the unavoidable risks that exist during the training phase. Transfer learning algorithms aim to find an optimal transfer map between different robots. In this paper, we investigate, through a theoretical study of single-input single-output (SISO) systems, the properties of such optimal transfer maps. We first show that the optimal transfer learning map is, in general, a dynamic system. The main contribution of the paper is to provide an algorithm for determining the properties of this optimal dynamic map including its order and regressors (i.e., the variables it depends on). The proposed algorithm does not require detailed knowledge of the robots' dynamics, but relies on basic system properties easily obtainable through simple experimental tests. We validate the proposed algorithm experimentally through an example of transfer learning between two different quadrotor platforms. Experimental results show that an optimal dynamic map, with correct properties obtained from our proposed algorithm, achieves 60-70% reduction of transfer learning error compared to the cases when the data is directly transferred or transferred using an optimal static map.Comment: 7 pages, 6 figures, accepted at the 2017 IEEE/RSJ International Conference on Intelligent Robots and System

On the Construction of Safe Controllable Regions for Affine Systems with Applications to Robotics

This paper studies the problem of constructing in-block controllable (IBC) regions for affine systems. That is, we are concerned with constructing regions in the state space of affine systems such that all the states in the interior of the region are mutually accessible through the region's interior by applying uniformly bounded inputs. We first show that existing results for checking in-block controllability on given polytopic regions cannot be easily extended to address the question of constructing IBC regions. We then explore the geometry of the problem to provide a computationally efficient algorithm for constructing IBC regions. We also prove the soundness of the algorithm. We then use the proposed algorithm to construct safe speed profiles for different robotic systems, including fully-actuated robots, ground robots modeled as unicycles with acceleration limits, and unmanned aerial vehicles (UAVs). Finally, we present several experimental results on UAVs to verify the effectiveness of the proposed algorithm. For instance, we use the proposed algorithm for real-time collision avoidance for UAVs.Comment: 17 pages, 18 figures, under review for publication in Automatic

Predicting the behavior of a drilled shaft wall retaining highly expansive soil

A full scale drilled shaft retaining wall was constructed in the highly expansive soil of Manor, Texas, to advance our understanding of the behavior of walls in highly expansive soils. The wall was monitored for a total period of four years; during the monitored period the state of Texas experienced severe drought conditions and the retained soil was inundated via a manmade pond. The monitored wall did not experience a point of fixity, instead, the wall experienced global movement towards the excavated side. Analytical predictions of the wall during short-term and long-term conditions miss-predicted the deflection and bending moment profiles, and could not estimate the wall behavior during transition state towards the long-term conditions. The Reese wall was simulated in a numerical model using the Finite Element method. A framework is developed in this study that can describe the swelling behavior of soil. The framework relies on two soil properties, first, a relationship between effective degree of saturation and effective stress, second, a relationship between stiffness, effective stress and voids ratio. Comparison between measured and predicted deflection and bending moment profiles showed that the proposed framework could result in reasonable deflection and bending moment predictions during dry and inundated saturation conditions. The predicted short-term deflection and bending moment profiles best matched the measured profiles when a constitutive model that accounts for small strain stiffness nonlinearity was adopted. The numerical model was used to segregate the superimposed wall deflection profile obtained during long-term conditions. The study concluded that the short-term conditions accounts for 20%, dissipation of the excess pore-pressures accounts for 30%, the additional hydrostatic pressures accounts for 10%, saturation change related factors accounts for 15%, and change in soil properties on the excavation side accounts for 25% of the total deflection. Parametric analyses concluded that the short -term and long-term behaviors of the Reese wall are not very sensitive to building stiffer and deeper walls . The long-term behavior of the Reese wall is sensitive to construction season, the hardening properties of soil, and the relationship between effective stresses and effective degree of saturation .Civil, Architectural, and Environmental Engineerin

Kedudukan murtad dan penyebaran agama bukan Islam menurut perspektif undang-undang di Malaysia: satu analisa isu dan cabaran = (The legal position of apostasy and spreading of non-Islamic teachings in Malaysia:analysis and challenges)

Umat Islam di Malaysia pada hari ini berhadapan dengan cabaran yang amat besar berikutan masyarakat digemparkan dengan dakwaan isu murtad yang semakin berleluasa. Isu murtad dilihat menjadi lebih serius berikutan kenyataan yang dibuat oleh Mufti Perak pada suatu ketika dahulu yang mendedahkan bahawa kajian oleh sekumpulan Melayu profesional mendapati seramai lebih 100,000 umat Islam di Malaysia telah pun bertukar agama. Pendedahan demi pendedahan telah dilakukan dan terkini, isu murtad telah beralih kepada isu baru berhubung agenda pengembangan agama bukan Islam kepada orang-orang Islam susulan kejadian pemeriksaan Jabatan Agama Islam Selangor ke atas sebuah gereja di Damansara Utama, Petaling Jaya pada 3 Ogos 2011, ketika umat Islam sedang mengerjakan ibadah puasa di bulan Ramadhan. Walaupun Malaysia telah dilabelkan sebagai sebuah negara Islam yang makmur dan stabil dari sudut ekonomi, politik dan sosialnya, namun isu murtad yang timbul mampu memberi kesan terhadap kemakmuran dan kestabilan yang sedang dinikmati oleh umat Islam sekiranya perkara tersebut tidak dibendung dari peringkat awal.Isu murtad dan kebebasan beragama bukanlah isu remeh dalam konteks negara yang meletakkan Islam sebagai agama Persekutuan. Justeru itu, penulisan ini mengupas dan membincangkan isu murtad dan penyebaran agama selain Islam di Malaysia dengan memfokuskan perbincangan menerusi perspektif undang-undang

Homeostatic model assessment of insulin resistance as a predictor of metabolic syndrome: Consequences of obesity in children and adolescents

AbstractBackgroundObesity and/or insulin resistance have gained increasing attention as the core manifestations of metabolic syndrome.ObjectiveTo evaluate insulin resistance according to homeostasis model assessment of insulin resistance index HOMA-IR in obese children and adolescents with or without metabolic syndrome at risk of type 2 diabetes mellitus.Design and subjects60 obese children and adolescents were recruited, metabolic syndrome was diagnosed according to the modified WHO criteria adapted for children and adolescents. Insulin resistance was calculated using the HOMA-IR.ResultsMetabolic syndrome (MS) was found in 42 subjects (70%), using modified WHO guidelines for diagnosing MS. On comparing MS-related parameters between the groups with (MS+) and without metabolic syndrome (MS−), median body mass index, waist circumference, waist/height ratio, and blood pressure, total cholesterol and triglyceride were significantly higher in the MS+group. Basal insulin level as well as HOMA-IR was also significantly different between MS+ and MS-groups. The presence of insulin resistance according to HOMA-IR was identified in 53% of obese children and adolescents. This HOMA-IR age and sex limit was exceeded by 70% children in the MS+group, but only by 43% children in the MS-group (p<0.001). HOMA-IR was positively correlated with the majority of anthropometric and biochemical parameters. The correlation was strongest with body mass index, waist circumference and diastolic blood pressure.ConclusionsHOMA-IR might be a reliable surrogate measure of insulin resistance and a strong predictor of type 2 diabetes in obese adolescents allowing the development of preventive measures and treatment when needed

Fabrication of μ-pH Biosensor for Implantable Medical Devices and Applications in Detecting Post-Operative Complications

The monitoring of the pH milieu inside the body is critical to the functions associated with implantable medical devices. By monitoring the variation of pH in real-time inside the body, we are capable of identifying the body’s response to the implant, the probability of infection, calibrating sensors and monitoring complications such as internal bleeding or anastomotic leakage. In this work, a pH sensor is presented consisting of a working electrode, a counter electrode and reference Ag/AgCl fabricated to allow the signals to be collected and compared to a reference value. For the working electrode, we chose Polyaniline (PANI) as the sensing material. Upon exposure to different pH solutions, PANI (the active sensing material) acts as an ion-selective membrane, the concentration gradient of ions across the membrane generates a potential difference that can be measured. We first fabricate microscale interdigitated electrodes by photolithography, e-beam deposition, etching, and liftoff. Then we coated a conducting hydronium-sensitive layer of PANI or PU by electropolymerization onto the active electrode. Then we placed the second electrode into a solution of KCl to apply a thin layer of AgCl on the Ag electrode, creating the Ag/AgCl reference electrode. The potential for the polymerization to provide the most stable active layer and the Nernstian potential was optimized. Moreover, the porosity of the active layers has been modified to allow the highest concentration of hydronium ions to diffuse to the electrodes, maximizing the signal stability. This bio-compatible electrodeposited polymer layer also protects the electrode from cellular attacks and biofouling. The fabricated device was used to monitor changes in pH in biological fluids such as gastric juice, simulated blood, and peritoneal fluid. The device was capable of monitoring changes in pH with a Nernstian potential of 68mV/pH. In addition, the active layer demonstrated an active lifetime of five weeks where the electrodes were capable of collecting data continuously during the active period