• Journal of Astronomy and Space Sciences
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• v.22 no.1
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• pp.47-58
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• 2005

This paper addresses development of the ultra-light analog sun sensors for small satellite applications. The sun sensor is suitable for attitude determination for small satellite because of its small, light, low-cost, and low power consumption characteristics. The sun sensor is designed, manufactured and characteristic-tested with the target requirements of ${\pm}60^{\circ}$ FOV (Field of View) and pointing accuracy of ${\pm}2^{\circ}$. Since the sun sensor has nonlinear characteristics between output measurement voltage and incident angle of sunlight, a higher order calibration equation is required for error correction. The error was calculated by using a polynomial calibration equation that was computed by the least square method obtained from the measured voltages vs. angles characteristics. Finally, the accuracies of 1-axis and 2-axes sun sensors, which consist of 2 detectors, are compared.

• Journal of Astronomy and Space Sciences
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• v.17 no.2
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• pp.267-276
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• 2000

PSS(Pyramidal type 2-axes Analog Sun Sensor) which will be used for KAISTSAT-4 is designed to be small, light, low in power consumptions, and adequate for small satellite attitude sensor. The PSS for the KAISTSAT-4 consists of the pyramidal structure, solar cells and amplifier. The pyramidal structure is suitable for the 2-axes sensing, Solar cells are made up of a rectangular shape of crystal silicon. The PSS measures the angle of incident light and initial satellite attitude measurement, and provides an alarm for the sunlight-sensitive payloads. This paper explains the PSS structure and the characteristic test result about the PSS with $\pm$$50^{\circ}$in FOV, less than $\pm$$3^{\circ}$in accuracy.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.2
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• pp.260-265
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• 2012

Satellite devices for fine attitude control of the Science & Technology Satellite-2 (STSAT-2). Based on the mission requirements of STSAT-2, the conventional analog-type sun sensors were found to be inadequate, motivating the development of a compact, fast and fine digital sun sensor (FDSS). The FDSS uses a CMOS image sensor and has an accuracy of less than 0.03degrees, an update rate of 5Hz and a weight of less than 800g. A pinhole-type aperture is substituted for the optical lens to minimize its weight. The target process speed is obtained by utilizing the Field Programmable Gate Array (FPGA), which acquires images from the CMOS sensor, and stores and processes the image data. The sensor accuracy is maintained by a rigorous centroid algorithm. This paper describes the FDSS designs, realizations, tests and calibration results.

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.5
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• pp.361-367
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• 2016

The intruder detection system using digital PIR sensor has the problem that it can't recognize human correctly. In this paper, we suggest a new intruder detection system based on analog PIR sensor to get around the drawbacks of the digital PIR sensor. The analog type PIR sensor emits the voltage output at various levels whereas the output of the digitial PIR sensor is binary. The signal captured using analog PIR sensor is sampled, and its frequency feature is extracted using FFT or MFCC. The extracted features are used for the input of neural networks. After neural network is trained using various human and pet's intrusion data, it is used for classifying human and pet in the intrusion situation.

• Solar Energy
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• v.18 no.3
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• pp.25-30
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• 1998

A sun tracking controller for PTC(parabolic trough concentrator) is a control system used to orient the concentrator toward the sun always, so that the maximum energy can be collected. The work presented here is a design and development of microprocessor based sun tracking control system for PTC. Sun tracking control system consists of a sun sensor and a single axis tracking control system. 80c196KC based control system consists of an analog input unit, 24V DC servomotor drive unit, I/O unit. Sun sensor has been constructed using photodiode and can detect the sun located within ${\pm}50^{\circ}$ measured from the sun sensor normal direction. The sun tracking system developed is being implemented and shows a good sun tracking performance.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1787-1790
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• 2005

We have developed satellite devices for fine attitude control of the Science & Technology Satellite-2 (STSAT-2) scheduled to be launched in 2007. The analog sun sensors which have been continuously developed since the 1990s are not adequate for satellites which require fine attitude control system. From the mission requirements of STSAT-2, a compact, fast and fine digital sensor was proposed. The test of the fine attitude determination for the pitch and roll axis, though the main mission of STSAT-2, will be performed by the newly developed FDSS. The FDSS use a CMOS image sensor and has an accuracy of less than 0.01degrees, an update rate of 20Hz and a weight of less than 800g. A pinhole-type aperture is substituted for the optical lens to minimize the weight while maintaining sensor accuracy by a rigorous centroid algorithm. The target process speed is obtained by utilizing the Field Programmable Gate Array (FPGA) in acquiring images from the CMOS sensor, and storing and processing the data. This paper also describes the analysis of the optical performance for the proper aperture selection and the most effective centroid algorithm.

• Journal of Astronomy and Space Sciences
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• v.13 no.2
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• pp.173-180
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• 1996

This paper briefly describes the KITSAT-1 and KITSAT-2 spacecrafts and presents the functions, calibration procedures and in-orbit results of the KITSAT-2 analog sun sensors have been flown as an experimental payload for the future mission. We have two constraints in their design: small size and very low power consumption due to the tight mass and power budget of the spacecraft. Two one-dimensional analog sun sensors are mounted on the top facet of the KITSAT-2 spaceraft. Each has $\pm$60 degrees of view angle and they cover 210 degree field of view in total as the 30 degree view angles are overlapped. Only the relative sun angle around the Z-axis (yaw-axis) and the spin rate of the spacecraft can be achieved as the one dimensional sun sensors are used and they are aligned with the Z-axis. The calibration formulae are obtained using the fifth order line fitting algorithm for each sun sensor on the ground and they are applied to the obtained in-orbit data. ASS-1 with silicon solar cells has maximum error of 1.5 degree and ASS-2 with silicon photocells manufactured at KAIST has maximum error of 0.5 degree except near 0 degree of sun ray incident anagle where random reflection of incident sun ray is maximum in orbit. The results are presented in chapter 4. The performance of each sun sensor and the possible mounting errors are stated in chapter 5.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.485-486
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• 2006

This paper proposes a novel low-cost CMOS temperature sensor for controlling the self-refresh period of a mobile DRAM. In this temperature sensor, ring oscillators composed of cascaded inverter stages are used to obtain the temperature of the chip. This method is highly area-efficient, simple and easy for IC implementation as compared to traditional temperature sensors based on analog bandgap reference circuits. The proposed CMOS temperature sensor was fabricated with 80 nm 3-metal DRAM process. It occupies a silicon area of only about less than $0.02\;mm^2$ at $10^{\circ}C$ resolution with under 5uW power consumption at 1 sample/s processing rate. This area is about 33% of conventional temperature sensor in mobile DRAM.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.444-447
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• 2004

SNR(Signal to Noise Ratio) is one of the most important performance for the electro-optical camera system. This paper shows not only the SNR analyses for the MSC system, which is the payload in the KOMPSAT2 satellite, but also the trials for its improvement in the electronics circuit design. The MSC deals with one panchromatic band and four multi-spectral bands. The SNR analyses are performed based on the MSC design for the each band and assuming that the defined radiance reached directly to the sensor entrance pupil. In the SNR calculation, shot noise, dark current noise, analog electronics noise and ADC quantization noise are considered as noise sources. In these noise sources, especially, the electronics noise depends on the camera electronics design. This paper shows the camera electronics design to increase SNR and its test results as well as the SNR analyses.

• Journal of Biosystems Engineering
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• v.35 no.6
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• pp.387-392
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• 2010

This study was performed to design and to construct a digital soil cone index(CI) measuring device replacing conventional analog type devices. The device developed in the study consisted of a load cell, a rotary encoder and a motor with a decelerator as its main parts. The cone speed was controlled lower than 3.0 m/s which keeps the standard suggested by the ASABE S313.3 specification. The experiment was conducted in a soil bin system as well as in various fields. The CI data measured by the developed device were compared with those by an existing measurement device(SC900, Spectrum, USA). Based on the experiments at various field conditions, the CI measuring characteristic of the device was quite similar to that of the conventional device within a acceptable $R^2$ range of more than 0.5(mean=0.76). It was concluded that the digital cone index measuring device was an effective and comprehensive sensor for measuring soil strength.