Applied Mechanics and Materials Vols. 479-480

Abstract: This study proposes an active islanding detection method for use of grid-connected inverter of renewable energy generation system (REGS). With a digital signal processor (DSP) integrated, the proposed method is capable of detecting the islanding fault of grid-connected inverters of REGS during the variable load conditions. To verify the effectiveness of the proposed method, the method was tested on a practical inverter of REGS, the field practical operations of the proposed method were studied in accordance with the conditions for the different loads and fault types. Test results are presented which show that the new proposed method is reliable, economical and easy for implementation.

Abstract: An accurate forecasting method for solar power generation of the photovoltaic (PV) system is urgent needed under the relevant issues associated with the high penetration of solar power in the electricity system. This paper presents a comparison of three forecasting approaches on short term solar power generation of PV system. Three forecasting methods, namely, persistence method, back propagation neural network method, and radial basis function (RBF) neural network method, are investigated. To demonstrate the performance of three methods, the methods are tested on the practical information of solar power generation of a PV system. The performance is evaluated based on two indexes, namely, maximum absolute percent error and mean absolute percent error.

Abstract: The penetration level of a PV system is often limited due to the violation of voltage variation introduced by the large intermittent power generation. This paper discusses the use of an active power curtailment strategy to reduce PV power injection during peak solar irradiation to prevent voltage violation so that the PV penetration level of a distribution feeder can be increased to fully utilize solar energy. When using the proposed voltage control scheme for limiting PV power injection into the study distribution feeder during high solar irradiation periods, the total power generation and total energy delivered by the PV system over a 1-year period are determined according to the annual duration of solar irradiation. With the proposed voltage control to perform the partial generation rejection of PV systems, the optimal installation capacity of PV systems can be determined by maximizing the net present value of the system so that better cost effectiveness of the PV project and better utilization of solar energy can be obtained.

Abstract: The subject of study in this work is a 135 Wp high concentration photovoltaic module with III-V solar cells. The module is currently installed in NPUST. Three equation forms for module temperature prediction were investigated. The simplest form predicts the module temperature quite well. Among these forms, the third form which takes into account the direct normal radiation yields the least error. The efficiency of the module was about 21% between 10:00 a.m. and 3:00 p.m. and the amount of power the module generates was linearly dependent on the electricity current.

Abstract: The present paper deals with the numerical study of energy absorption of reduction tubes using a die subject to axial impact load. Non-linear finite element software LS-DYNA is employed to analyze the deformation pattern and energy absorption characteristics. The tubes, with the bottom ends constrained axially, deformed in necking modes by the axially moving dies. The geometries of the tubes and the dies were varied to find out the influence of the geometry parameters. The strain rate effect of the material is considered and the Cowper-Symonds equation is applied in the plastic dynamic analysis.

Abstract: Since the Field Programmable Gate Arrays (FPGAs) with high density are available nowadays, systems with complex functions can be realized by FPGA in a single chip while they are usually traditionally implemented by several individual chips. In this research, the drives as well as motion controller are integrated and implemented on Altera Cyclone III FPGA. The system is also evaluated by applying it to a 3-axis motion platform driven by stepping motors. Finally, experimental results of current regulator and motion controller are shown to prove the validness.

Abstract: A stable direct adaptive CMAC PI controller for a class of uncertain nonlinear systems is investigated under the constrain that only the system output is available for measurement. First, a state observer is used to estimate unmeasured states of the systems. Then, the PI control structure is used for improving robustness in the closed-loop system and avoiding affection of uncertainties and external disturbances. The global asymptotic stability of the closed-loop system is guaranteed according to the Lyapunov stability criterion. To demonstrate the effectiveness of the proposed method, simulation results indicate that the proposed approach is capable of achieving a good trajectory following performance without the knowledge of plant parameters.

Abstract: Human-to-Humanoid motion imitation is an intuitive method to teach a humanoid robot how to act by human demonstration. For example, teaching a robot how to stand is simply showing the robot how a human stands. Much of previous work in motion imitation focuses on either upper-body or lower-body motion imitation. In this paper, we propose a novel approach to imitate human whole-body motion by a humanoid robot. The main problem of the proposed work is how to control robot balance and keep the robot motion as similar as taught human motion simultaneously. Thus, we propose a balance criterion to assess how well the root can balance and use the criterion and a genetic algorithm to search a sub-optimal solution, making the root balanced and its motion similar to human motion. We have validated the proposed work on an Aldebaran Robotics NAO robot with 25 degrees of freedom. The experimental results show that the root can imitate human postures and autonomously keep itself balanced.

Abstract: This paper proposes a novel hybrid antilock braking system (ABS) with the combination of auxiliary brake and a magnetorheological (MR) brake with multiple poles. The operation concept of this MR brake is different to conventional MR brake. Its output torque proves the ability to be used in motorcycle brake system. In concept, a fast-response MR brake replaces existed hydraulic brake system, or works as an auxiliary brake, the brake performance can be effectively improved and driving stability can be guaranteed. Simulation model of the MR brake has been built and its braking performance for using on a motorcycle was verified. After that, a motorcycle simulation software was employed to validate the hybrid ABS system under appropriated working condition. The results confirm its feasibility for actual application as a hybrid ABS system.

Abstract: In this paper, we simulate the effect of imposed external dead space by examining the optimized neural muscular drive and respiratory signals, including, airflow and lung volume profiles. To study the effect of external dead space loading, the measurement model by Gray is used and human respiratory control simulator based on an optimal respiratory control mechanism is implemented. The respiratory control simulations are performed with external dead space loading (0, 0.4 and 0.8 l) under rest and CO₂ inhalation of 3% to 7%. The waveshaping of both the imposed external dead space and CO₂ inhalation on the respiratory waveforms are studied.