Applied Mechanics and Materials Vols. 284-287

Abstract: Achieving excellent tracking performance for a 2-DOF rehabilitation robot actuated by pneumatic artificial muscles (PAMs) is very difficult, due to the high nonlinearity and time-varying behavior associated with gas compression and the nonlinear elasticity of bladder containers. This paper proposes a Takagi-Sugeno (T-S) fuzzy model control to improve control performance and establish a 2nd order system model using a recursive least square method. The proposed approach decomposes the model of a nonlinear system into a set of linear subsystems. In this manner, the design of the controller in the T-S fuzzy model is capable of using simple linear control techniques to provide a systematic framework with which to design a state feedback controller. The analysis of stability is performed by using the Lyapunov direct method. We employed the powerful LMI Toolbox of MATLAB to solve linear matrix inequalities (LMIs) to determine controller gains. Experimental results verify that the proposed controller can achieve excellent tracking performance.

Abstract: This paper proposes an obstacle avoidance algorithm for unmanned vehicles in unknown environment by a single sensor. The scan system is composed of an ultrasonic sensor and a servo motor which rotates from 0 to 180 degrees to obtain the distance data, and the profile of the obstacle can be depicted by a histogram which we use to find out the boundary of the obstacle. In this avoidance algorithm we will use the danger zone concept to judge whether the obstacle will cause a possible collision. The danger zone concept surrounds the vehicle by a sphere and uses the relative velocity to calculate the area in which obstacles will collide with the vehicle within a pre-specified time period. Combining the profile of the boundary of the obstacle with the danger zone concept, we can determine the maneuvers to avoid collisions.

Abstract: Sensor nodes having the limited resource, energy efficiency is an important issue. Clustering on the sensor networks reduces the volume of inter-node communications and raises energy efficiency by transmitting the data collected from members by a cluster head to a sink node. But, due to radio frequency characteristics, interference and collision can occur between neighbor clusters, the resulted re-transmission is more energy consuming. The interference and collision occurred among adjacent clusters can be resolved by assigning non-overlapping channels among neighbor clusters. In this paper, we propose a channel reuse procedure which shows practical steps to assign dynamically channels among adjacent clusters in sensor networks. This method is expected to perform successfully the allocation process of non-overlapping channels for various cluster topologies.

Abstract: A simple, small-size, compact and high-sensitivity refractive-index sensor composed of a short no-core fiber (NCF) about 20 mm in length sandwiched between two pieces of single-mode fibers is proposed in this paper. The index measurement is experimentally demonstrated with the sensitivity of 7792.85 nm/ RIU in the range from 1.440 to 1.454 and 227.14 nm/ RIU in the range from 1.300 to 1.430. This sensing mechanism is based on the induced multi-mode interfering wavelength shift in the no-core fiber when the reflective index of the fiber outside is changed.

Abstract: This study presents an application of sensing technology in a teaching and learning environment. In a general instruction environment, most instructors teach and manage about thirty students in a classroom. However, a teacher cannot control the degree of concentration and learning status for each student simultaneously, which causes ineffective learning for some students. For this reason, this study utilizes a learning concentration detection system through a combination of sensor and context aware technology in the learning environment. This system includes a pressure detection sensor and facial detection sensor to detect facial expressions, eye activities and body movements. This system utilizes an artificial bee colony algorithm to optimize the system performance to help a teacher immediately understand the degree of concentration and learning status of students. Based on this, an instructor can give appropriate guidance to several unfocused students at the same time. The experimental results indicate that the proposed method improves the searching process and enables the system to achieve better performance.

Abstract: Many motion analysis systems which have been introduced in the past few years are currently receiving interests from researchers and developers due to their usefulness and wide application capability in the future. However, many of those systems meet with difficulties for the real applications because of high cost for the implementation and less accuracy. This paper introduces a new 3D motion analysis system which can be implemented at a lower cost and acceptable accuracy for various applications. The key component of our new system is the use of the MSK (Microsoft Kinect) sensor system which is equipped with both visual camera and infrared camera. It can provide the color image, the 3D depth image and the 3D skeleton data without wearing any marker device on the human body while it can provide acceptable accuracy in 3D motion trace at low cost. Our system can be exploited for a base framework for various 3D motion-based applications such as physical rehabilitation support, sport motion analysis and biomechanical applications.

Abstract: The Underwater Sensor Network (UWSN) could be recorded by hydrophones suspended in the channel as earthquake monitors by seismic events on or below the seafloor generated energy. In this paper, we present a novel position of sensor devices and routing protocol towards short for Sound Fixing and Ranging channel (SOFAR) for Sound Fixing and Ranging channel technologies, which could save transmission power. The sound speed also increases towards the warmer sea surface with temperature. Thus we use the oceanography to find more efficient ways of utilizing routing protocol and in to obtain more effective detection and identification capabilities for underwater sources. We present an adaptive location-based routing protocol which can overcome the location based UWSN without Global Positioning System (GPS) position. It reduced costs of deployment in long range propagation. The performances are measured according to the energy consumption per bit in which the result of simulator is better than other routing protocols such as FBR.

Abstract: Five novel ideas are proposed in this paper to integrate an active RFID tag with thermal convection angular accelerometer on a flexible substrate, thus the device is a wireless sensor. The first innovative idea is that this device is without any movable parts, so it is very reliable. The second new idea is that it is made on a flexible substrate, such as plastic or polyimide, thus it can save more power. The third new idea is that the xenon gas is applied in the chamber to conduct the heat instead of the traditional Carbon dioxide. CO2 can produce oxidation effect to the heater and thermal sensors, while the xenon not. The fourth new idea is to apply a hemi-spherical chamber; it is more streamline in nature with less drag effect to ease the fluid flow and yield quicker response. The fifth new idea and the most powerful one is that the angular accelerometer is integrated with an active RFID tag on the same flexible substrate, thus the device becomes a more useful wireless sensor. Note the linearity, sensitivity, and response times of step-input angular accelerations are better for the hemi-spherical chamber filled with Xe gas. The sensitivity is 71.4°C/(rad/s2) and the response time is 60μs.

Abstract: This paper presents the performance of an adaptive location estimator combining Kalman filtering (KF) scheme with vision-assisted scheme for wireless sensor networks. To improve the location accuracy, a KF tracking scheme is employed at a mobile terminal to track variations of the location estimate. In addition, with a vision-assisted calibration technique based on the normalized cross-correlation scheme, the proposed approach is an accuracy enhancement procedure that effectively removes system errors causing uncertainty in measuring a dynamic environment. Therefore, using the vision-assisted approach to estimate the locations of the reference nodes as landmarks, a KF-based scheme with the landmark information can calibrate the location estimation and improve the corner effect. The experimental results demonstrate that more than 60 percent of the location estimates computed from the proposed approach have error distances less than 1.4 meters in a ZigBee positioning platform. As compared with the non-tracking algorithm and non-vision-assisted approach, the proposed algorithm can achieve reasonably good performance.

Abstract: Wireless Sensor Networks are based on the ZigBee standard. ZigBee uses the IEEE 802.15.4 physical and MAC (medium access control) layers to provide standards-based reliable wireless data transfer. Also, ZigBee provides low-power wireless connectivity features. The features allow ZigBee-based products to be installed easily and cost-effectively. Thus, this technology has been attracting extensive research and development efforts to replace the traditional wired solutions for Building Automation Systems. However, wireless communications in indoor building environments are prone to be influenced by multiple concurrent factors, such as multi-path fading, channel contention, other radio interference, human activity and limited battery energy. Also, sensor detection is not fully reliable. Thus, system robustness is very concerning in these applications. In this paper, we propose a reliable wireless sensor network and an accurate occupancy detection mechanism. We implemented this system in an indoor building for the lighting control of public areas, including corridors, a coffee room and a washroom. The system framework was shown to be effective in terms of network communication reliability and sensor detection accuracy.