| Judul | Abstract | Halaman |
|---|
| Model and Controller Order Reduction for Infinite Dimensional Systems | This paper presents a reduced order model problem using reciprocal transformation and balanced truncation followed by low order controller design of infinite dimensional systems. The class of systems considered is that of an exponentially stable state linear systems (A, B, C), where operator A has a bounded inverse, and the operator B and C are of finite-rank and bounded. We can connect the system (A, B, C) with its reciprocal system via the solutions of the Lyapunov equations. The realization of the reciprocal system is reduced by balanced truncation. This result is further translated using reciprocal transformation as the reduced -order model for the systems (A, B, C). Then the low order controller is designed based on the reduced order model. The numerical examples are studied using simulations of Euler-Bernoulli beam to show the closed-loop performance. | 1-16 |
| Adaptive Control with Approximated Policy Search Approach | Most of existing adaptive control schemes are designed to minimize error between plant state and goal state despite the fact that executing actions that are predicted to result in smaller errors only can mislead to non-goal states. We develop an adaptive control scheme that involves manipulating a controller of a general type to improve its performance as measured by an evaluation function. The developed method is closely related to a theory of Reinforcement Learning (RL) but imposes a practical assumption made for faster learning. We assume that a value function of RL can be approximated by a function of Euclidean distance from a goal state and an action executed at the state. And, we propose to use it for the gradient search as an evaluation function. Simulation results provided through application of the proposed scheme to a pole -balancing problem using a linear state feedback controller and fuzzy controller verify the scheme’s efficacy. | 17-38 |
| Fabrication of Microporous Water Filter Using Titanium Dioxide Particles, Silica Particles, and Polyethylene Glycol | We report the fabrication of microporous filter for use in filtering both inorganic and organic substances from liquid materials. Titania (TiO 2) anatase was used as the main material for this filter. Polyethylene glycol (PEG) with average molecular weight of 20,000 was also used as additive to control the formation of pores, especially pore sizes. The mixture of titania and PEG was pressed into cylindrical tablet shape at room temperature and then simply heated inside a furnace up to temperature where the PEG decomposed into gas to leave only connected titania particles. The use of titania as base material for the filter allows the organic substances that trapped inside the filter pores to be easily removed by heating up the used filter at above decomposition temperature of the trapped organics. We also made other filter by adding small amount of silica (SiO2) particles to reduce the size of the pores as well as to improve the mechanical strength. We observed that filters containing silica particles, with smaller in size compared to titania, resulted in better mechanical strength, smaller in pore sizes and better filtering results in term of turbidity and dissolved oxygen (DO) content. This method is potential for development of larger scale and cheaper water filters for use in various applications. | 39-52 |
| Analysis and Minimization of Output Current Ripple of Multiphase Carrier-Based PWM Inverters | Analysis and minimization of output current ripple of multiphase carrier-based PWM inverters are presented in this paper. Analytical expression of rms value of output current ripple of multiphase PWM inverters as a function of the reference signal is first derived. Based on this expression, it is shown that a pure sinusoidal signal is the optimum reference signal that results in minimum output current ripple. Different to three-phase PWM inverters, injection of harmonics into the sinusoidal reference signal is neither necessary nor useful. The rms values of output current ripple of 5-, 7-, and 9-phase PWM inverters under various reference signals are compared. Experimental results are included to show the validity of the analysis method. | 53-64 |
| Geochemical Tracer in Coral as a Sea Surface Temperature Proxy: Records from Jukung Coral | Sr/Ca has been analyzed from coral core from the Seribu Islands reef complex i.e Jukung Island. SST from ERSST dataset and air temperature measured at Jakarta is used for Sr/Ca calibration. The results show that Jukung Island coral Sr/Ca correlates better with SST than with air temperature. A comparison between the Sr/Ca records with the Nino 3.4 index shows that Jukung coral sites indicate warming sea surface temperatures during the beginning of El Nino events followed by cooling temperatures at the end of El Nino years. | 65-72 |
| Tolerance Stack Analysis in Francis Turbine Design | The tolerance stacking problem arises in the context of assemblies from interchangeable parts because of the inability to produce or to join parts exactly according to nominal dimensions. Either the relevant part’s dimension varies around some nominal values from part to part or the act of assembly that leads to variation. For example, as runner of Francis turbine is joined with turbine shaft via mechanical lock, there is not only variation in the diameter of runner and the concentricity between the runner hole and turbine shaft, but also the variation in concentricity between the outer parts of runner to runner hole. Thus, there is the possibility that the assembly of such interacting parts won’t function or won’t come together as planned. Research in this area has been conducted and 2 mini hydro Francis turbines (800 kW and 910 kW) have been designed and manufactured for San Sarino and Sawi Dago 2 in Central Sulawesi. Experiences in analyzing the tolerance stacks have been documented. In this paper it will be demonstrated how the requirements of assembling performance are derived to be the designed tolerances of each interacting | 73-90 |
| Closed Form Solution of Synchoronous Machine Short Circuit Transients | This paper presents the closed form solution of the synchronous machine transients undergoing short circuit. That analytic formulation has been derived based on linearity and balanced conditions of the fault. Even though restrictive, the proposed method will serve somehow or other as a new resource for EMTP productivity. Indisputably superior, the closed-form formulation has some features inimitable by discretization such as continuity, accuracy and absolute numerical stability. Moreover, it enables us to calculate states at one specific instant independent of previous states or a snapshot, which any discretization methods cannot do. | 91-102 |
