• Journal of Astronomy and Space Sciences
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• v.13 no.2
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• pp.20-29
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• 1996

Provision of the electrical power generated from solar array is one of the most fundamental requirements for the spacecraft payloads. Power subsystem collects, regulates and distributes power to the experiment payloads and to the various spacecraft subsystem. In this paper, the analysis result of the KITSAT-1 WOD shows that the in-orbit operation of whole power system has been in good condition.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.9
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• pp.850-857
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• 2007

The design and analysis of satellite electrical power subsystem is an important driver for the mass, size, and capability of the satellite. In particular, satellite energy balance analysis is critical in determining the capabilities and limitations of the power subsystem and the success of satellite operations. This paper introduces a new energy balance analysis program for LEO satellite development and shows an example of test results using other LEO satellite design data. The test results show that the proposed energy balance program can be used the optimal sizing of satellite electrical power subsystem and the analytical prediction of the on-orbit energy balance during satellite mission operations.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.355-358
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• 1996

Electrical Power System (EPS) of Electric Vehicle which consists of batteries, motor and driving subsystem, has been modeled. A battery model is modeled with an electrical circuit representing a characteristics of real battery. Driving subsystem is modeled as three different level namely exact, average and functional models. Load profile includes road information, speed profile and EV mechanical parameters, which are incorporated into a reference torque in the driving subsystem model. A system model is integrated to simulate the performance of electric vehicle such as energy balance, battery status, and electrical stress of each subsystem.

• Journal of Power Electronics
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• v.6 no.2
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• pp.104-113
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• 2006

Satellites have provided the impetus for the orderly development of reliability engineering research and analysis because they tend to have complex systems and hence acute problems. They were instrumental in developing mathematical models for reliability, as well as design techniques to permit quantitative specification, prediction and measurement of reliability. Reliability engineering is based on implementing measures which insure an item will perform its mission successfully. The discipline of reliability engineering consists of two fundamental aspects; $(1^{st})$ paying attention to details, and $(2^{nd})$ handling uncertainties. This paper uses some of the basic concepts, formulas and examples of reliability theory in application. This paper emphasizes the practical reliability analysis of a Low Earth Orbit (LEO) Micro-satellite power subsystem. Approaches for specifying and allocating the reliability of each element of the power system so as to meet the overall power system reliability requirements, as well as to give detailed modeling and predicting of equipment/system reliability are introduced. The results are handled and analyzed to form the final reliability results for the satellite power system. The results show that the Electric Power Subsystem (EPS) reliability meets the requirements with quad microcontrollers (MC), two boards working as main and cold redundant while each board contains two MCs in a hot redundant.

• Journal of KSNVE
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• v.11 no.2
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• pp.257-264
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• 2001

In this research, piezoelectric smart structures are applied for SEA(Statistical Energy Analysis), which is well known approach for high frequency analysis. A new input power measurement based on piezoelectric electrical power measurement is proposed and compared with the conventional method in SEA. As an example, a simple aluminum beam on which piezoelectric actuator is attached is considered. By measuring the electrical impedance and electrical current of the piezoelectric actuator, the electrical power given on the actuator is found and this is In turn converted into the mechanical energy. From the measured value of the stored energy of the beam, the Internal loss factor is calculated and this value shows a good agreement with that given by the conventional method as well as the theoretical value. To compare the coupling loss factor, L-shape beam system which consists of a aluminum beam subsystem and a steel beam subsystem coupled by three pin is taken as second example. The input power and stored energy of each subsystem are found by the proposed approach. The coupling loss factor found by the electrical input power obtained from the piezoelectric actuator exhibits similar trend to the value found by the conventional method as well as the theoretical value. In conclusion, the use of SEA for high frequency application of piezoelectric smart structures is Possible. Especially, the input power that is essential for SEA can be found accurately by measuring the electrical input power of the piezoelectric actuator.

• KIPE Magazine
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• v.2 no.3
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• pp.5-11
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• 1997

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.8
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• pp.459-466
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• 2000

In this paper, we propose an attitude controller for an unstructured object using CMG(Control Moment of Gyro) subsystem, which has a stabilizer function. The CMG subsystem consists of one motor for spinning the wheel and the other motor for turning the outer gimbal. While the wheel of CMG subsystem is spinning at high speed, applying force to the spin axis of the wheel leads the torque about the vertical axis. We utilize the torque to control the attitude of object in this study. For the stabilizer function, in additiion, holding the load at the current position, the power applied to the gimbal motor of CMG will be cut, which result in the braking force to stop the load by gyro effect. However, due to the gear reduction connected to outer gimbal, slow load motion cannot generate the braking force. Thus, in this study, we are willing to make a holding force by applying control power to the gimbal motor from the signal of piezoelectric gyroscopic sensor that detected the angular velocity of the load. These two features are demonstrated in experiment, carrying a beam with crane. As a result, load was started to rotate by controlling gimbal positiion and was stopped by turning off the gimbal power. Moreover, slow movement of the load was also rejected by additional control with gyroscopic sensor.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.476-480
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• 2003

This paper presents an effective method to analyze the dynamic characteristics for the shilling transients of power transmission system using the multibody dynamics, which is composed of subsystem equation, subsystem assemble, and the self-determining technique for the system degree of freedom. Using the advantages of multibody dynamics, the proposed method can be used easily for mathematical models of mechanical systems, such as a power transmission, compared with newtonian method. With this theory, dynamic simulation program was developed. The program can be used to verify system performances, transient phenomena, and other dynamic problems. The simulation of a target system was presented, and its validity was attained by being compared with the previous analysis using newtonian method.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.6
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• pp.175-181
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• 2004

This paper presents the main method to analyze the dynamic characteristics of power transmission system using the multi-body dynamics, which is based on the concept of subsystem equation, subsystem assembling, and the self-determination technique for the system degree of freedom. We can model the mechanical components of power transmission system easily with the advantage of multi-body dynamics. Based on the theory, a dynamic simulation program was developed to analyze system performances, transient phenomena, and other dynamic problems. The driving performance of automatic transmission was simulated with using the multi-body dynamics and Newtonian method, and the validity of program was proved by comparing the two kinds of result.

• ETRI Journal
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• v.39 no.3
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• pp.428-436
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• 2017

State-of-the-art processors require increasingly complicated memory services for high performance and low power consumption. In particular, they request transfers within a burst in a wrap-around order to minimize the miss penalty of a cache. However, synchronous dynamic random access memories (SDRAMs) do not always generate transfers in the wrap-round order required by the processors. Thus, a memory subsystem rearranges the SDRAM transfers in the wrap-around order, but the rearrangement process may increase memory latency and waste the bandwidth of on-chip interconnects. In this paper, we present a memory subsystem that is effective for the wrapping bursts of a cache. The proposed memory subsystem makes SDRAMs generate transfers in an intermediate order, where the transfers are rearranged in the wrap-around order with minimal penalties. Then, the transfers are delivered with priority, depending on the program locality in space. Experimental results showed that the proposed memory subsystem minimizes the memory performance loss resulting from wrapping bursts and, thus, improves program execution time.