Applied Mechanics and Materials Vols. 764-765

Abstract: Signal blockage and reflections from buildings and other large, solid objects can lead to accuracy degradation. One of the merits of the Global Positioning System (GPS) vector tracking loop (VTL) architectures is that the tracking loop can be assisted in such degraded signal environments. This paper proposes the incorporation of the neural network (NN) into the VTL for improving the positioning quality. The NN is used to bridge the GPS signal and prevent the error growth due to signal outage from spreading into the entire tracking loop. The NNs are employed for predicting adequate numerical control oscillator (NCO) inputs, i.e., providing better prediction of residuals for the Doppler frequency and code phase in order to maintain regular operation of the navigation system. The NN-assisted VTL demonstrates the capability to ensure proper functioning of navigation system. Results show that the NN-assisted VTL can effectively provide improved performance during degraded signal environments such as GPS outages.

Abstract: In this paper, an unscented particles filter (UPF) based DLL tracking loop with multipath parameter estimation and mitigation capability is proposed for the Global Positioning System (GPS). The I (in-phase) and Q (quadrature) accumulator outputs from the GPS correlators are used as the observational measurements of UPF to estimate the multipath parameters such as amplitude, code delay, phase, and carrier Doppler. The particle filter (PF) possesses superior performance as compared to EKF and UKF as an alternative estimator for dealing with the nonlinear, non-Gaussian system. To handle the problem of heavy-tailed probability distribution, one of the strategies is to incorporate the UKF into the PF as the proposal distribution, leading to the unscented particle filter (UPF). The results show that the tracking loop using the proposed design can effectively estimate the multipath parameters and has demonstrated substantial estimation accuracy improvement as compared to that of the conventional EKF and UKF approaches.

Abstract: Although the vector tracking loop architectures provide several important advantages, they suffer some fundamental drawbacks. The most significant drawback is that failure of tracking in one channel may affect the entire system and lead to loss of lock on all satellites. The other drawback is that errors in the navigation solutions may degrade the accuracy of the tracking results. For robustness improvement of the vector tracking loop, the EKF based receiver autonomous integrity monitoring (RAIM) and fault detection and exclusion (FDE) algorithms are developed to prevent the error of one channel from spreading into the vector tracking loop. The RAIM is used to check the possible fault in the pseudorange and the pseudorange rate; the fault detection and exclusion mechanism is employed for excluding the abnormal satellite signal to prevent the failure of one channel from spreading into the entire tracking loop. The feasibility of the proposed method will be demonstrated. Performance assessment and evaluation for the proposed approach will be carried out.

Abstract: Breakages of solar cells mostly depend on the stresses induced in process, handling and transportation, and rely on the presence of defect such as micro-crack. Transporting vibration typically induces solar cell has crack propagation and performance degradation. In addition, the resonance frequency generated by test package during shipping excites the external force happened on packaged cells. This work aimed to evaluate the performance and defect coherently in solar cell caused by vibration during both truck and air transportation, and analyzed the electrical data (P_mpp, R_s, R_sh) and defects in detailed. Result showed the breakage rate due to broken cell is 2 % only, but degradation rate due to abnormal cell is accumulated to 6 %, which exposed the high potential failure for transporting cells. Consequently, this paper has proposed a comprehensive test method to alleviate the reliability obstacles of solar cells, and accelerate the development of cells protection design for transportation.

Abstract: In this paper, we propose a Smart-Home system with ZigBee Wireless Sensor Networks (WSNs) technology. The system provides automation system in the House. The monitor system uses Andriod NDK and SDK to write application interface for an Android embedded platform. In this system, we provide access control system to obtain sensor data and inquiry into node status. We use multi-channel architecture to reduce a hidden terminal problem and upgrade packet delivery ratio.

Abstract: This paper introduces an alignment method using machine vision feedback control method. A panel is placed on a XXY table and its posture is inspected by image sensors with a frame grabber. The alignment of the panel is corrected by adjusting its positions until the amount of misalignment converges into a small tolerance error. Two-phase control process is also derived with this image acquisition design. Applying this proposed control method, long distance moving requirement and better alignment precision performance request can be also guaranteed. Experimental results are shown to demonstrate the feasibility of this alignment control system.

Abstract: This paper presents sliding mode control (SMC) to aircraft automatic landing system (ALS), and uses genetic algorithm (GA), particle swarm optimization (PSO) and chaos particle swarm optimization (CPSO) to adjust controller parameters. When wind shear is encountered, the aircraft automatic landing system can not be used in such environment during serious wind speed changes. The proposed intelligent control scheme can help the pilots guide the aircraft to a safe landing in wind shear condition. PID control and cerebella model articulation controller (CMAC) are applied to the controller design.

Abstract: A relatively inexpensive and highly effective design for high precision chamber was developed but the control theory and optimized parameters were totally different from traditional methodologies. Among all kinds of quality programs, lean six sigma (LSS) is the most famous and widely-used method by manufacturing and service industries. The DMAIC (Define, Measure, Analyze, Improve and Control) methodology was used to figure out the key factors relative to high precision of relative humidity and improve the control parameters to meet the target. At the start, the baseline of Z bench was-0.24 and standard deviation was 1.62659. After lean six sigma project implemented, Z bench was up to 1.89 and standard deviation was down to 0.443986. This paper will address the critical process and analysis method for lean six sigma project, especially those for precise control of relative humidity.

Abstract: In this paper, a mechatronic motor-table system is realized to plan the minimum input electrical energy trajectory (MIEET) based on Hamiltonian function. In this system, the adaptive tracking controller is designed to track the MIEET to overcome the nonlinear friction and external disturbance. Moreover, trapezoidal trajectory (TT) and regulator control are compared with the MIEET by the adaptive tracking controller. Finally, it is concluded that the MIEET based on the adaptive tracking controller can obtain the minimum input electrical energy and robustness performance for the mechatronic motor table system.

Abstract: Micro-satellite has long-term in-orbit work in the harsh environment of space, the components such as actuators and sensors in the attitude control system continue to perform in-orbit control operations, therefore are prone to faults. In practical mission, such as formation flying, orbital transfer, de-tumbing and attitude control need to use thruster to control. As the thrust control is fail, the entire mission fails. In the paper, the two-stage unscented kalman filter is used to obtain the effectiveness factor value and system estimated states are obtained. Meanwhile, a robust thruster controller is designed with the estimated results to accomplish the joint design of Fault Detection and Diagnosis and Fault-Tolerant Control.