Applied Mechanics and Materials Vols. 479-480

Abstract: An intelligent gripper is designed with embedded distributed control structure for overcoming the uncertainty of grasped object mass and soft/hard features. An efficient model-free intelligent fuzzy sliding mode control strategy is employed to design the position and force controllers of gripper, respectively. Experimental results of pick-and-place soft and hard objects with grasping force auto-tuning and anti-slip control strategy are shown by pictures to verify this distributed system performance. The position and force tracking errors are less than 1 mm and 0.1 N, respectively.

Abstract: A laboratory-based sensor network testbed for Smart Grid was developed at the Smart Grid and High Power System Laboratory of The University of Hong Kong. The setup is featured by a scaled transmission-line model, visualization of sensor measurement, optical communication network, and integration with global positioning system (GPS). The transmission-line model consists of a power cable and towers in which various types of sensors including magnetic sensors, infrared sensors, strain gauges, and accelerometers are installed to monitor the condition of the transmission line and the transmission towers. Magnetic sensors and infrared sensor are employed as advanced sensors which can provide more accurate and comprehensive information of the transmission line. The sensor data is transferred to the computer for analysis and visualization. Graphical user interface (GUI) was designed in LabVIEW to integrate the data acquisition and display of measurement results including cable position, inclination and vibration of the tower, frequency and waveform of the cable current. The host computer also forms an IP network with five remote computers, via optical fiber and optical interface card, for testing various communication protocols. The topology and connectivity of the network is graphically displayed. The sensor network is integrated with GPS and can perform synchronized measurement with the GPS timing. This sensor network testbed provides a platform for the implementation testing, experimentation, and feasibility evaluation of new sensor applications under test in Smart Grid.

Abstract: The center of mass of the micro-satellite can offset due to fuel consumption in the course of propulsion, with the interference of external orbital environment such as gravity gradient torque and solar radiation torque. If the structural shape is discoid and asymmetrical, the attitude control may be difficult. The only solution is to design a robust controller, so that the attitude pointing of the satellite can meet the mission requirements with the interference of internal parameter perturbation and external disturbance. This study applied the robust control theory control law in the design of Formosat-3 propulsion mode attitude control, and carried out cross validation of the feasibility of the controller by time domain and frequency domain stability analyses. This study used controller as the experimental result. The time domain performance indexes (e.g., rise time, maximum overshoot and stabilization time) of the designed controller were consistent with the robust stability margin of stable performance index of frequency domain. Meanwhile, in order to reduce the weight and manufacturing cost of satellite, in the design of satellite attitude angular rate determination, the project used unscented kalman filter (UKF) algorithm, coarse sun sensor (CSS) and earth horizon sensor (EHS) as measurement components to obtain the satellite attitude without rate gyro. The research method and procedures in this study are applicable to any shaped and asymmetrical satellites with large mass variation and without angular rate sensor. The attitude sensors include three-axis magnetometer, horizon sensor, CSS as the analytic platform for stability of attitude control.

Abstract: In recent years, Wireless Sensor Network (WSN) is one important type of mobile network that consists of many sensor nodes (SNs). The power consumption rate and bandwidth of each SN becomes an important issue and needs to be addressed. For increasing the reliability of WSN, this paper proposed a power-aware mechanism to select a stable manager from SNs by fuzzy based inference systems based on the factors of speed, power and location. Further, our mechanism can trigger a mobile agent to distribute the managerial workload.

Abstract: A Wireless Sensor Network (WSN) consists of spatially distributed autonomous devices which use sensor nodes (SNs) to monitor physical or environmental conditions cooperatively. However, the SN is limited by the energy resource, the memory, the computation, the communication capability, etc. Therefore, the hierarchical clustering topology has been proposed to prolong the lifetime of WSNs by decreasing the energy consumption of SNs. Unfortunately, the network topology is still unstable due to the workload of the cluster managers is overloading. However, in this study, a Centre Clustering Mechanism (CCM) underlying the center-based WSN is proposed to improve the stability of network topology, assists SN within the working area, and takes advantage of message exchange.

Abstract: The article designs a seven joints robot arm using PC-based controller. The system architecture of the robot arm contains seven DC servomotors, seven driver devices and a NI motion control card. The robot arm uses proximity sensors to locate the limit position, and programs motion trajectories to finish assigned tasks. We tune the parameters of the PID controller for the robot arm, and get the nice response to control the robot arm moving to the assigned position. The user interface is developed to control each DC servomotor using Visual Basic. The paper computes the kinematic equations of the seven joints robot arm, and calculates the motion displacement of each joint using inverse kinematic equation. The controller of the robot arm can implement precision point to point motion trajectories, and programs the motion paths on the user interface. In the experimental result, users can program the word type in the user interface. The robot arm catches the pin to write the word in the plane.

Abstract: The article programs the shortest motion paths of the multiple mobile robots to be applied in the Chinese chess game, and presents the movement scenario of the chess using mobile robots on the grid based chessboard platform. Users play the chess game using the mouse to obey the evaluation algorithm on the user interface. The user interface programs the motion paths that are the shortest displacement using enhance A* searching algorithm and solves the collision problem of the programmed motion paths for the assigned chesses to and reprogram the new motion paths using enhance A* searching algorithm, too. The supervised computer controls mobile robots according to the programmed motion paths of the assigned chess moving on the platform via wireless RF interface. In the experimental results, we use simulation method to search the motion paths of the assigned chesses on the user interface, and implement the simulation results on the chessboard platform using mobile robots. Mobile robots move on the platform according to the programmed motion paths from the start points to the target points and avoid the collision points.

Abstract: In this paper, we propose a cyclostationarity-based spectrum sensing scheme for dynamic traffic circumstances. First, we model the spectrum sensing problem in dynamic traffic circumstances as a binary hypothesis testing problem where primary users (PUs) might randomly depart or arrive during the sensing period. Then, we develop a generalized likelihood ratio (GLR) and derive a test statistic via the GLR, which is based on the cyclostationarity of the PU signals. Numerical results confirm that the proposed scheme offers a better spectrum sensing performance than the conventional scheme based on energy detection for dynamic traffic circumstances.

Abstract: This paper addresses the problem of how to make efficient energy consumption on routing communications among the set of wireless sensor nodes deployed randomly in a large-scale manner. Tree-based routing topology is considered in the study with regarding to its simplicity of routing process. To minimize the energy dissipation of tree-routing, centralized coordination schemes are usually used to construct an optimal tree routing topology. In this paper, a distributed-based tree routing protocol is proposed not only to improve the scalability of the centralized tree routing schemes but also handle the balance consumption among the sensor nodes. With computer simulation, the effectiveness of the proposed routing scheme is verified and shown to be useful in large-scale wireless sensor networks.

Abstract: In this paper, we aim to improve theenergy efficiency via a Clustering Algorithm based on Social Insect Colonies (CASIC), inorder to extend the lifetime of Wireless Sensor Networks(WSNs). We propose a CASIC with Sub-clusters (CASIC-S) for reducing the energyconsumption of sensor nodes within the concentric layer during transmission orreception. We also investigate the CASIC-S scheme with different numbers ofnodes in our simulations. The simulation results show that our proposed scheme performs better in terms of first node death and the number of nodes alive.