Modelling and Fast Terminal Sliding Mode Control for Mirror-based Pointing Systems

In this paper, we present a new discrete-time Fast Terminal Sliding Mode (FTSM) controller for mirror-based pointing systems. We first derive the decoupled model of those systems and then estimate the parameters using a nonlinear least-square identification method. Based on the derived model, we design a FTSM sliding manifold in the continuous domain. We then exploit the Euler discretization on the designed FTSM sliding surfaces to synthesize a discrete-time controller. Furthermore, we improve the transient dynamics of the sliding surface by adding a linear term. Finally, we prove the stability of the proposed controller based on the Sarpturk reaching condition. Extensive simulations, followed by comparisons with the Terminal Sliding Mode (TSM) and Model Predictive Control (MPC) have been carried out to evaluate the effectiveness of the proposed approach. A comparative study with data obtained from a real-time experiment was also conducted. The results indicate the advantage of the proposed method over the other techniques.Comment: In Proceedings of the 15th International Conference on Control, Automation, Robotics and Vision (ICARCV 2018

Impact analysis of actuator torque degradation on the IRB 120 robot performance using simscape-based model

Actuators in a robot system may become faulty during their life cycle. Locked joints, free-moving joints, and the loss of actuator torque are common faulty types of robot joints where the actuators fail. Locked and free-moving joint issues are addressed by many published articles, whereas the actuator torque loss still opens attractive investigation challenges. The objectives of this study are to classify the loss of robot actuator torque, named actuator torque degradation, into three different cases: Boundary degradation of torque, boundary degradation of torque rate, and proportional degradation of torque, and to analyze their impact on the performance of a typical 6-DOF robot (i.e., the IRB 120 robot). Typically, controllers of robots are not pre-designed specifically for anticipating these faults. To isolate and focus on the impact of only actuator torque degradation faults, all robot parameters are assumed to be known precisely, and a popular closed-loop controller is used to investigate the robot’s responses under these faults. By exploiting MATLAB-the reliable simulation environment, a simscape-based quasi-physical model of the robot is built and utilized instead of an actual expensive prototype. The simulation results indicate that the robot responses cannot follow the desired path properly in most fault cases

Automatic Crack Detection in Built Infrastructure Using Unmanned Aerial Vehicles

This paper addresses the problem of crack detection which is essential for health monitoring of built infrastructure. Our approach includes two stages, data collection using unmanned aerial vehicles (UAVs) and crack detection using histogram analysis. For the data collection, a 3D model of the structure is first created by using laser scanners. Based on the model, geometric properties are extracted to generate way points necessary for navigating the UAV to take images of the structure. Then, our next step is to stick together those obtained images from the overlapped field of view. The resulting image is then clustered by histogram analysis and peak detection. Potential cracks are finally identified by using locally adaptive thresholds. The whole process is automatically carried out so that the inspection time is significantly improved while safety hazards can be minimised. A prototypical system has been developed for evaluation and experimental results are included.Comment: In proceeding of The 34th International Symposium on Automation and Robotics in Construction (ISARC), pp. 823-829, Taipei, Taiwan, 201

DETERMINANTS OF THE INTENTION TO USE LOAN SHARKS OF STUDENTS: EMPIRICAL EVIDENCES FROM VIETNAMESE UNIVERSITIES

Based on the development of the Unified Theory of Acceptance and Use of Technology model (UTAUT), the authors measured the intention to use loan sharks for students in Vietnamese universities. The research utilizes both quantitative and qualitative methods with the primary data collected from students in Vietnamese universities. The results demonstrate that three main variables significantly impact on intention to use loan sharks, namely "Social Influence," "Financial Literacy," and "Expectancy Effort." In particular, the authors added the "Financial Literacy" element through the results of in-depth interviews. Besides, "Gender" and "Academic Year" also affect the relationship between three main variables and the intention to use loan sharks. Based on the research results, the authors propose several specific policy implications for authorities to eliminate loan sharks through social media and promote financial literacy in universities

Review paper: General overview of control problems in wind power plants

Wind power plants can be realized with different generator types using different control principles. The choice of the generator regardless of the control method, potentially destabilizes the grid, and can even lead to grid collapse. For independent grid (e.g. on islands) this risk is especially great. The report aimed at giving the reader a general overview of the control methods, and the developers a better  understanding of each generator type to get the right choice for their wind power project