Multi-Collector Control for Workload Balancing in Wireless Sensor and Actuator Networks

한야민,변희정 대한임베디드공학회 2021 대한임베디드공학회논문지 Vol.16 No.3

The data gathering delay and the network lifetime are important indicators to measure the service quality of wireless sensor and actuator networks (WSANs). This study proposes a dynamically cluster head (CH) selection strategy and automatic scheduling scheme of collectors for prolonging the network lifetime and shorting data gathering delay in WSAN. First the monitoring region is equally divided into several subregions and each subregion dynamically selects a sensor node as CH. These can balance the energy consumption of sensor node thereby prolonging the network lifetime. Then a task allocation method based on genetic algorithm is proposed to uniformly assign tasks to actuators. Finally the trajectory of each actuator is optimized by ant colony optimization algorithm. Simulations are conducted to evaluate the effectiveness of the proposed method and the results show that the method performs better to extend network lifetime while also reducing data delay.

AUTOSAR 기반 공유자원이용 스케줄링 구조

최준열,조준형,최윤자 대한임베디드공학회 2018 대한임베디드공학회논문지 Vol.13 No.6

As a result of the technological advances in the E / E system, automotive system can provide advanced functions for safety and comfort. In addition, mechanical systems is changed to the electronic system. And the systems perform cooperative functions through communication. So the E / E system becomes more complicated as the size of the system increases. In order to secure the safety of complicated E / E system, ISO26262 standard require that Freedom from Interference and Sufficient Independence be met. In this paper, we propose a software scheduling method that can guarantee the independence between decomposed components after software decomposition and software development of ASIL D level EPB (Electronic Parking Brake) system

M&S기법을 활용한 선박용 지향성 요동보상장치 성능 분석

이성균,고진용,한용수,김창환 대한임베디드공학회 2018 대한임베디드공학회논문지 Vol.13 No.6

Recently, the tasks assigned to surface ship are becoming diverse and important. In this trend, shipboard directional pedestals are widely used for surveillance and electronic warfare because ships are always under angular motion such as rolling, pitching and yawing. To estimate the performance of pedestal, the motion responses of vessel as well as mechanical characteristics of pedestal should be considered. In this study, both the motion responses of vessel which the pedestal will be mounted and the behavior of 3-axis pedestal are considered. Numerical analysis based on potential theory is used to obtained motion characteristics of vessel and then 6-DOF motions of vessel are simulated under operational condition. 1st-order time delay model and LQR control algorithm are used for modeling of pedestal drive model and control model, respectively. By using coordinate transform, the angular motions which the pedestal should compensate are calculated from the vessel's angular motion. Through these M&S methodologies, time history of pedestal behavior and maximum angular error of each pedestal axis are obtained. Overall M&S results show that 3-axis pedestal compensate the angular motion induced by vessel, efficiently.

오프라인 우선 정책에 의한 멀티 디바이스의 실시간 데이터 동기화 구현

이대명,김은후,주문갑 대한임베디드공학회 2018 대한임베디드공학회논문지 Vol.13 No.6

Offline-first strategy is that it allows data to be saved while offline, and when connected online, data is synchronized to ensure that all devices have the same data. Multi-device is a term that shares data through synchronization on various platforms on Android, ios, etc. First, all of the data is stored in the local repository like SQLite and then on the server via HTTP communication. Then, the synchronization is completed by receiving the changed data from the server and storing it in the local repository at the time of the synchronization, and sending the changes to the server from the client. We proposed and implemented a database structure, APIs, and a illustrative application running on PC and Android phone.

제어흐름 에러 탐지를 위한 분리형 시그니처 모니터링 기법

최기호,박대진,조정훈,Choi, Kiho,Park, Daejin,Cho, Jeonghun 대한임베디드공학회 2018 대한임베디드공학회논문지 Vol.13 No.5

Control flow errors are caused by the vulnerability of memory and result in system failure. Signature-based control flow monitoring is a representative method for alleviating the problem. The method commonly consists of two routines; one routine is signature update and the other is signature verification. However, in the existing signature-based control flow monitoring, monitoring target application is tightly combined with the monitoring code, and the operation of monitoring in a single thread is the basic model. This makes the signature-based monitoring method difficult to expect performance improvement that can be taken in multi-thread and multi-core environments. In this paper, we propose a new signature-based control flow monitoring model that separates signature update and signature verification in thread level. The signature update is combined with application thread and signature verification runs on a separate monitor thread. In the proposed model, the application thread and the monitor thread are separated from each other, so that we can expect a performance improvement that can be taken in a multi-core and multi-thread environment.

연산 특성을 고려한 향상된 적응적 가비지 컬렉션 정책

박송화,이정훈,이원오,김현우,Park, Song-Hwa,Lee, Jung-Hoon,Lee, Won-Oh,Kim, Hyun-Woo 대한임베디드공학회 2018 대한임베디드공학회논문지 Vol.13 No.5

NAND flash memory has widely been used because of non-volatility, low power consumption and fast access time. However, it suffers from inability to provide update-in-place and the erase cycle is limited. The unit of read/write operation is a page and the unit of erase operation is a block. Moreover erase operation is slower than other operations. We proposed the Adaptive Garbage Collection (called "AGC") policy which focuses on not only reducing garbage collection process time for real-time guarantee but also wear-leveling for a flash memory lifetime. The AGC performs better than Cost-benefit policy and Greedy policy. But the AGC does not consider the operation characteristics. So we proposed the Advanced Adaptive Garbage Collection (called "A-AGC") policy which considers the page write operation count and block erase operation count. The A-AGC reduces the write operations by considering the data update frequency and update data size. Also, it reduces the erase operations by considering the file fragmentation. We implemented the A-AGC policy and measured the performance compared with the AGC policy. Simulation results show that the A-AGC policy performs better than AGC, specially for append operation.

DRAM&PCM 하이브리드 메모리 시스템을 위한 능동적 페이지 교체 정책

정보성,이정훈,Jung, Bo-Sung,Lee, Jung-Hoon 대한임베디드공학회 2018 대한임베디드공학회논문지 Vol.13 No.5

Phase Change Memory(PCM) with low power consumption and high integration attracts attention as a next generation nonvolatile memory replacing DRAM. However, there is a problem that PCM has long latency and high energy consumption due to the writing operation. The PCM & DRAM hybrid memory structure is a fruitful structure that can overcome the disadvantages of such PCM. However, the page replacement algorithm is important, because these structures use two memory of different characteristics. The purpose of this document is to effectively manage pages that can be referenced in memory, taking into account the characteristics of DRAM and PCM. In order to manage these pages, this paper proposes an page replacement algorithm based on frequently accessed and recently paged. According to our simulation, the proposed algorithm for the DRAM&PCM hybrid can reduce the energy-delay product by around 10%, compared with Clock-DWF and CLOCK-HM.

소형 지구 관측 위성용 플래시 기반 저장장치 설계 및 시험

백인철,박형식,황기선,Baek, Inchul,Park, Hyoungsic,Hwang, Kiseon 대한임베디드공학회 2018 대한임베디드공학회논문지 Vol.13 No.5

Recently, small satellite industries are rapidly changing. Demand for high performance small satellites is increasing with the expansion of Earth Observation Satellite market. A next-generation small satellites require a higher resolution image storage capacity than before. However, there is a problem that the HW configuration of the existing small satellite image storage device could not meet these requirements. The conventional data storing system uses SDRAM to store image data taken from satellites. When SDRAM is used in small satellite platform of a next generation, there is a problem that the cost of physical space is eight times higher and satellite price is two times higher than NAND Flash. Using the same satellite hardware configuration for next-generation satellites will increase the satellite volume to meet hardware requirements. Additional cost is required for structural design, environmental testing, and satellite launch due to increasing volume. Therefore, in order to construct a low-cost, high-efficiency system. This paper shows a next-generation solid state recorder unit (SSRU) using MRAM and NAND Flash instead of SDRAM. As a result of this research, next generation small satellite retain a storage size and weight and improves the data storage space by 15 times and the storage speed by 4.5 times compare to conventional design. Also reduced energy consumption by 96% compared to SDRAM based storage devices.

속도 명령 기반 PID 제어기를 이용한 멀티로터 무인항공기의 표적 자동 추종 시스템 구현

정현도,고선재,최병조 대한임베디드공학회 2018 대한임베디드공학회논문지 Vol.13 No.6

This paper presents an automatic target tracking flight system using a PID controller based on velocity command of a multirotor UAV. The automatic flight system includes marker based onboard target detection and an automatic velocity command generation replacing manual controller. A quad-rotor UAV is equipped with a camera and an image processing computer to detect the marker in real time and to estimate the relative distance from the target. The marker tracking system consists of PID controller and generates velocity command based on the relative distance. The generated velocity command is used as the input of the UAV's original flight controller. The operation of the proposed system was verified through actual flight tests using a marker on top of a moving vehicle and tracks it to successfully demonstrate its capability using a quad-rotor UAV.

낮은 쓰기 성능을 갖는 비휘발성 메인 메모리 시스템을 위한 성능 및 에너지 최적화 기법

정우순,이형규,Jung, Woo-Soon,Lee, Hyung-Gyu 대한임베디드공학회 2018 대한임베디드공학회논문지 Vol.13 No.5

Non-volatile RAM devices have been increasingly viewed as an alternative of DRAM main memory system. However some technologies including phase-change memory (PCM) are still suffering from relatively poor write performance as well as limited endurance. In this paper, we introduce a proactive last-level cache management to efficiently hide a low write performance of non-volatile main memory systems. The proposed method significantly reduces the cache miss penalty by proactively evicting the part of cachelines when the non-volatile main memory system is in idle state. Our trace-driven simulation demonstrates 24% performance enhancement, compared with a conventional LRU cache management, on the average.