Non-linear control law for articulated serial manipulators: Simulation augmented with hardware implementation

The performance of a robotic arm includes accuracy, repeatability and reliability to accomplish a task. These parameters, in turn, are function of associated control law. Multi-Degree Of Freedom (DOF) robotic arms, because of their inherent highly non-linear dynamics, demand sophisticated control laws. Trivial control strategies fail to cope with disturbances and uncertainties that are common in today's plants. This paper presents the design, simulation and physical implementation of a non-linear control technique Variable Structure Control (VSC) for a 6 DOF arm. Based on the derived dynamic model of the arm and designed control law, simulations have been conducted in MATLAB/Simulink. The controller parameters have been tuned for optimal response. Various desired trajectories characterize the tracking performance of the control law. The simulation results have been then validated by implementing the law on a customdeveloped novel AUTonomous Articulated Robotic Educational Platform (AUTAREP). Coupling effects between various joints of the robot have also been investigated. Results of this research find potential in industrial control of robotic manipulators to perform complex tasks

Chattering Free Sliding Mode Control and State Dependent Kalman Filter Design for Underground Gasification Energy Conversion Process

The fluctuations in the heating value of an underground coal gasification (UCG) process limit its application in electricity generation, where a desired composition of the combustible gases is required to operate gas turbines efficiently. This shortcoming can be addressed by designing a robust control scheme for the process. In the current research work, a model-based, chattering-free sliding mode control (CFSMC) algorithm is developed to maintain a desired heating value trajectory of the syngas mixture. Besides robustness, CFSMC yields reduced chattering due to continuous control law, and the tracking error also converges in finite time. To estimate the unmeasurable states required for the controller synthesis, a state-dependent Kalman filter (SDKF) based on the quasi-linear decomposition of the nonlinear model is employed. The simulation results demonstrate that despite the external disturbance and measurement noise, the control methodology yields good tracking performance. A comparative analysis is also made between CFSMC, a conventional SMC, and an already designed dynamic integral SMC (DISMC), which shows that CFSMC yields (Formula presented.) and (Formula presented.) improvement in the root mean squared tracking error with respect to SMC and DISMC, respectively. Moreover, CFSMC consumes (Formula presented.) and (Formula presented.) less control energy as compared to SMC and DISMC, respectively

Almond protects the liver in coronary artery disease: A randomized controlled clinical trial

Objective: To compare the effect of Pakistani and American almonds on serum concentration of liver enzymes in coronary artery disease patients.Methods: The randomised controlled trial was conducted at the Cardiology Clinics of Aga Khan University Hospital, Karachi, from February to July, 2012, and comprised patients who were randomised into intervention PA and AA groups and the control NI groups. Subjects in the intervention groups were provided Pakistani and American varieties of almonds 10g/day respectively with instructions to soak them overnight, remove the skin and eat them before breakfast for 12 weeks. The control group underwent no intervention. Serum concentrations of aspartate transaminase, Alanine transaminase and gamma-glutamyl transferase were analysed and compared.Results: Of the 150 subjects, 110(73.3%) completed the study. Of them, there were 38(34.5%) in PA group, 41(37.3%) in AA, and 31(28.2%) in the NI group. Dietary almonds significantly reduced serum concentrations of aspartate transaminase, alanine transaminase and gamma-glutamyl transferase in the two intervention groups compared to the controls group (pConclusions: A low dose of almonds was found to be an effective strategy to protect the liver

Modelling and robust controller design for an underactuated self-balancing robot with uncertain parameter estimation

A comprehensive literature review of self-balancing robot (SBR) provides an insight to the strengths and limitations of the available control techniques for different applications. Most of the researchers have not included the payload and its variations in their investigations. To address this problem comprehensively, it was realized that a rigorous mathematical model of the SBR will help to design an effective control for the targeted system. A robust control for a two-wheeled SBR with unknown payload parameters is considered in these investigations. Although, its mechanical design has the advantage of additional maneuverability, however, the robot's stability is affected by changes in the rider's mass and height, which affect the robot's center of gravity (COG). Conventionally, variations in these parameters impact the performance of the controller that are designed with the assumption to operate under nominal values of the rider's mass and height. The proposed solution includes an extended Kalman filter (EKF) based sliding mode controller (SMC) with an extensive mathematical model describing the dynamics of the robot itself and the payload. The rider's mass and height are estimated using EKF and this information is used to improve the control of SBR. Significance of the proposed method is demonstrated by comparing simulation results with the conventional SMC under different scenarios as well as with other techniques in literature. The proposed method shows zero steady state error and no overshoot. Performance of the conventional SMC is improved with controller parameter estimation. Moreover, the stability issue in the reaching phase of the controller is also solved with the availability of parameter estimates. The proposed method is suitable for a wide range of indoor applications with no disturbance. This investigation provides a comprehensive comparison of available techniques to contextualize the proposed method within the scope of self-balancing robots for indoor applications

Model predictive control of consensus-based energy management system for DC microgrid

The increasing deployment and exploitation of distributed renewable energy source (DRES) units and battery energy storage systems (BESS) in DC microgrids lead to a promising research field currently. Individual DRES and BESS controllers can operate as grid-forming (GFM) or grid-feeding (GFE) units independently, depending on the microgrid operational requirements. In standalone mode, at least one controller should operate as a GFM unit. In grid-connected mode, all the controllers may operate as GFE units. This article proposes a consensus-based energy management system based upon Model Predictive Control (MPC) for DRES and BESS individual controllers to operate in both configurations (GFM or GFE). Energy management system determines the mode of power flow based on the amount of generated power, load power, solar irradiance, wind speed, rated power of every DG, and state of charge (SOC) of BESS. Based on selection of power flow mode, the role of DRES and BESS individual controllers to operate as GFM or GFE units, is decided. MPC hybrid cost function with auto-tuning weighing factors will enable DRES and BESS converters to switch between GFM and GFE. In this paper, a single hybrid cost function has been proposed for both GFM and GFE. The performance of the proposed energy management system has been validated on an EU low voltage benchmark DC microgrid by MATLAB/SIMULINK simulation and also compared with Proportional Integral (PI) & Sliding Mode Control (SMC) technique. It has been noted that as compared to PI & SMC, MPC technique exhibits settling time of less than 1µsec and 5% overshoot

UAV-assisted Cluster-head Selection Mechanism for Wireless Sensor Network Applications

The use of unmanned aerial vehicles (UAVs) is gaining popularity in many applications, i.e. data collection, surveillance, wireless sensor networks (WSNs) etc. In the WSN domain, the UAVs are used to create a more flexible data-gathering platform. This integration maximizes the lifetime of a WSN by optimizing the energy budget. In this paper, we have utilized these benefits of UAVs and have proposed an optimum cluster head (CH) selection strategy to maximize the lifetime of WSNs. The proposed method uses the average residual energy, the channel condition and the Euclidean distance of each sensor node (SN) with a UAV to nominate a group of CHs. Based on the initial analytical analysis, the proposed scheme maximizes the lifetime of a WSN by a fair amount in comparison to the state-of-the-art methods

Dual antenna coupling manipulation for low SAR smartphone terminals in talk position

A rigorous analysis of the concept of coupling manipulation utilizing two antennas suited to modern smartphone devices in talk position for voice calls is presented. By using the optimum relative phase between the elements, they can substantially reduce the specific absorption rate (SAR) but still maintain efficiency due to the splitting of power between them and by exploiting a suitable level of inter element coupling. The same antenna elements can still be used for multiple input multiple output (MIMO) when not in talk position without heavily degrading their fundamental capacity limit but this is of secondary importance. The concept could be applied to frequency ranges used in mobile communications from 1.8 to 6 GHz where the ground plane has sufficient form factor. Extensive simulations using two planar inverted-F antennas (PIFAs) operating at 2.4 GHz are carried out to demonstrate conceptually how two antennas can be optimized to reduce SAR by over 50% compared to a single antenna element. SAR reduction is maintained regardless of the user’s head composition and how they are handling the device in talk position. Antenna prototypes are measured and compared to verify the capacity when the handset is used away from the body with two MIMO terminal antennas

Modeling and computed torque control of a 6 degree of freedom robotic arm

This paper presents modelling and control design of ED 7220C - a vertical articulated serial arm having 5 revolute joints with 6 Degree Of Freedom. Both the direct and inverse kinematic models have been developed. For analysis of forces and to facilitate the controller design, svstem dvnamics have been formulated. A non-linear control technique, Computed Torque Control (CTC) has been presented. The algorithm, implemented in MATLAB/Simulink, utilizes the derived dynamics as well as linear control techniques. Simulation results dearly demonstrate the efficacy of the presented approach in terms of traiectory tracking Various responses of the arm joints have been recorded to characterize the performance of the control algorithm. The research finds its applications in simulation of advance nonlinear and robust control techniques as well as their implementation on the physical platform. © 2014 IEEE

An Empirical Study of Food Safety, Food Handling, and Food Poisoning Awareness Among Foreign Students in Penang, Malaysia

These foreign students are highly concerned with food safety and food handling knowledge as they are presumably involved in perilous eating behaviours, which exposes them to the risk of foodborne diseases. The present cross-sectional study aimed to evaluate the awareness and practices regarding food safety and food handling among the foreign students of Universiti Sains Malaysia (USM), Penang. A self-administered questionnaire was used to collect demographic information and to assess awareness of food safety and food handling among foreign students. Questionnaires were distributed into five sections that concealed key food safety apprehensions. A total of 328 students received the questionnaires, and 203 (61.89%) responded. Cleanliness of eating tables, food temperature, smoke-free environment and food handler appearance are the key food safety considerations for the respondents. The results showed that a high percentage of male respondents (57.98%) experienced food poisoning, and considered food from restaurants is the cause of foodborne diseases. Respondents have utmost awareness about the cleanliness of utensils and kitchen surfaces, hand hygiene, and preclusion of cross-contamination, however, described a poor knowledge concerning the temperature and heat treatment of the food. Good understanding regarding food poisoning symptoms was observed among the respondents, especially in a female group. The outcome revealed that foreign students, irrespective of gender, demonstrated comparable food safety and food handling knowledge. The study laid emphasis on education and training as an optimum way to foster awareness and encourage students’ food safety knowledge and practices