정지 속도 검출 가능한 이중 증분 엔코더 센서 알고리즘 개발

이세한(Se-Han Lee),김병창(Byoung-Chang Kim) 제어로봇시스템학회 2009 제어·로봇·시스템학회 논문지 Vol.15 No.1

The output of the encoder is a digital pulse, which is also easy to be connected to a digital controller. There are various angular velocity detecting methods of M, T, and M/T. Each of them has its own properties. There is a common limitation that the angular velocity detection period is strongly dependent on the destination velocity magnitude in case of ultimate low range. They have ultimately long detection period or cannot even detect angular velocity at near zero velocity. This paper proposes a zero velocity detectable sensor algorithm with the dual encoder system. The sensor algorithm is able to keep detection period moderately at near zero velocity and even detect zero velocity within nominal period. It is useful for detecting velocity in case of changing rotational direction at which there occurs zero velocity. In this paper, various experimental results are shown for the algorithm validity.

Investigating the temperature from friction stir in the SPIF process via an infrared imager

Khompee Limpadapun,Ramil Kesvarakul 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.3

Single point incremental forming (SPIF) is a highly flexible forming process for sheet metal. It has low production costs be-cause the process does not use a die. It is suitable for prototyping and made-to-order production. Currently, the SPIF process employs the concept of heat to increase formability. The idea is to generate heat from friction caused by sliding the tool against the workpiece, called “friction stir". This research proposed to study the behavior of temperature that occurs when affected by the tool rotation speed and the feed rate, which are both variables affecting friction stir. This research adopted the method of detecting temperature with infrared cameras and online recording data. The camera sensor received data as 8-bit images containing data from 0 to 255. The value of each position represented the temperature level. In this research, the mini-mum-maximum temperature range was set at 80-300 degrees Celsius for forming the hot dipped zinc coat roll steel sheet at a thickness of 0.2 mm using the SPIF process. The variable parameters were the tool rotation speed and feed rate. The tool rotation speed was categorized as high and used no sliding friction with feed rates of 500, 1000, 1500 mm/min. Concerning the results analysis, this study used the relationships between tool rotational speed and feed rate, shown as relative sliding velocity. The results showed with significance that the increase of the maximum temperature in the process corresponded to an increase in relative sliding velocity using a tool rotational speed and feed rate with no relative sliding velocity. The process temperature was close to room temperature. Relative sliding velocity at approximately 6000 and 10000 mm/min caused a maximum temperature of approximately 160-180 and 200-250 degrees Celsius, respectively. Another issue found in the experiment was that not turning the tool reduced the formability of the process.

Attitude Determination Algorithm based on Relative Quaternion Geometry of Velocity Incremental Vectors for Cost Efficient AHRS Design

Byungjin Lee,Young Jae Lee,Sangkyung Sung 한국항공우주학회 2018 International Journal of Aeronautical and Space Sc Vol.19 No.2

A novel attitude determination method is investigated that is computationally efficient and implementable in low cost sensor and embedded platform. Recent result on attitude reference system design is adapted to further develop a three-dimensional attitude determination algorithm through the relative velocity incremental measurements. For this, velocity incremental vectors, computed respectively from INS and GPS with different update rate, are compared to generate filter measurement for attitude estimation. In the quaternion-based Kalman filter configuration, an Euler-like attitude perturbation angle is uniquely introduced for reducing filter states and simplifying propagation processes. Furthermore, assuming a small angle approximation between attitude update periods, it is shown that the reduced order filter greatly simplifies the propagation processes. For performance verification, both simulation and experimental studies are completed. A low cost MEMS IMU and GPS receiver are employed for system integration, and comparison with the true trajectory or a high-grade navigation system demonstrates the performance of the proposed algorithm.

Attitude Determination Algorithm based on Relative Quaternion Geometry of Velocity Incremental Vectors for Cost Efficient AHRS Design

Lee, Byungjin,Lee, Young Jae,Sung, Sangkyung The Korean Society for Aeronautical Space Sciences 2018 International Journal of Aeronautical and Space Sc Vol.19 No.2

A novel attitude determination method is investigated that is computationally efficient and implementable in low cost sensor and embedded platform. Recent result on attitude reference system design is adapted to further develop a three-dimensional attitude determination algorithm through the relative velocity incremental measurements. For this, velocity incremental vectors, computed respectively from INS and GPS with different update rate, are compared to generate filter measurement for attitude estimation. In the quaternion-based Kalman filter configuration, an Euler-like attitude perturbation angle is uniquely introduced for reducing filter states and simplifying propagation processes. Furthermore, assuming a small angle approximation between attitude update periods, it is shown that the reduced order filter greatly simplifies the propagation processes. For performance verification, both simulation and experimental studies are completed. A low cost MEMS IMU and GPS receiver are employed for system integration, and comparison with the true trajectory or a high-grade navigation system demonstrates the performance of the proposed algorithm.

Development of non-destructive testing method to evaluate the bond quality of reinforced concrete beam

Muhammad Saleem,Abdulmalik Mohammed Almakhayitah 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.74 No.3

Non-destructive tests are commonly used in construction industry to access the quality and strength of concrete. However, till date there is no non-destructive testing method that can be adopted to evaluate the bond condition of reinforced concrete beams. In this regard, the presented research work details the use of ultra-sonic pulse velocity test method to evaluate the bond condition of reinforced concrete beam. A detailed experimental research was conducted by testing four identical reinforced concrete beam samples. The samples were loaded in equal increments till failure and ultra-sonic pulse velocity readings were recorded along the length of the beam element. It was observed from experimentation that as the cracks developed in the sample, the ultra-sonic wave velocity reduced for the same path length. This reduction in wave velocity was used to identify the initiation, development and propagation of internal micro-cracks along the length of reinforcement. Using the developed experimental methodology, researchers were able to identify weak spots in bond along the length of the specimen. The proposed method can be adopted by engineers to access the quality of bond for steel reinforcement in beam members. This allows engineers to carryout localized repairs thereby resulting in reduction of time, cost and labor needed for strengthening. Furthermore, the methodology to apply the proposed technique in real-world along with various challenges associated with its application have also been highlighted.

폭발챔버에서 전파하는 화염의 국부 거동

박달재 ( Dal Jae Park ),이영순 ( Young Soon Lee ) 한국안전학회(구-한국산업안전학회) 2011 한국안전학회지 Vol.26 No.2

다중 장애물을 가지는 폭발챔버에서 전파하는 화염과 국부 장애물의 상관관계를 조사하기 위하여 실험적 연구를 수행하였다. 폭발챔버 높이 235 mm, 단면적 1,000×950mm2, 벤트면적 1,000×320mm2를 가지는 폭발챔버를 제작하였으며, 30% blockage ratio를 가지는 장애물을 챔버내에 설치하였다. 전파하는 화염과 장애물의 상관관계를 조사하기 위해 고속카메라를 사용하였다. 고속카메라로 얻어진 화염 이미지로부터 장애물 주위의 국부 화염전파 거동은 2가지 다른 방법, 즉 전파하는 화염전면(flame front)의 각 pixel point에서 산정된 평균 화염전파속도와 연소면적 증가(incremental burnt area)/화염전면 길이(flame front length) 관점에서 분석하였다. 분석결과, 2가지 방법으로 얻은 결과는 거의 일치하는 경향을 나타났으며, 전파하는 화염이 장애물의 전면과 상호 작용할 때 화염속도는 급격히 증가하다가 장애물의 후단면에서 약간 감소하고, 화염이 장애물 후단에서 재결합될 때 다시 급격히 증가하였다. Experimental studies were carried out in an explosion chamber to investigate the influences of multiple cylinder obstacles on local flame propagation. The chamber dimension is 235 mm in height with a 1,000×950mm2 rectangular cross section and a large vent area of 1,000×320mm2. Multiple cylinder bars with obstruction ratio of 30% were used. In order to examine the interaction between the propagating flames and the obstacles, temporally resolved flame front images were recorded by a high speed video camera. The propagation behaviour of local flame fronts around the left obstacle was analyzed in terms of two different methods such as the incremental burnt area divided by the flame front length and the average of the local propagation velocity determined at each point along the flame front. It was found that two methods give good consistency.

궤도결정 결과를 이용한 매뉴버 측정 평가

황유라(Yoola Hwang),이병선(Byoung-Sun Lee) 한국항공우주학회 2017 한국항공우주학회 학술발표회 논문집 Vol.2017 No.11

Design Study of a Korean Mars Mission

Lee, Eun-Seok,Chang, Keun-Shik,Park, Chul The Korean Society for Aeronautical and Space Scie 2004 International Journal of Aeronautical and Space Sc Vol.5 No.2

In this paper we carried out a design study for an unmanned Mars missionsuitable for Republic of Korea. The mission will use a KSLV series launch system,which is to place a one tonne payload into the LEO. We calculated the velocityincrements(AV) required for departure from Earth and insertion into the orbitaround Mars based on the mission opportunity data provided by NASA. Two typesof Mars modules - entry type and orbiter type - were considered in this studyWe calculated the mass of TPS(therma1 protection system) for the entry tvpe Marsmodule based on the heat transfer rate and heat load from the Mars atmosphere tothe surface of the TPS. The heat transfer rate and heat load were obtained throughan entry trajectory calculation. For the orbiter type Mars module, we calcuIated themass breakdown of the additional spacecraft which is to insert the Mars moduleinto the orbit around Mars. Other mass items were determined by proportioningfrom the existing Mars modules. This paper finally proposes the payload capacitiesfor each types of Mars modules.

Design Study of a Korean Mars Mission

Eun-Seok Lee,Keun-Shik Chang,Chul Park 한국항공우주학회 2004 International Journal of Aeronautical and Space Sc Vol.5 No.2

In this paper we carried out a design study for an unmanned Mars mission suitable for Republic of Korea. The mission will use a KSLV series launch system, which is to place a one tonne payload into the LEO. We calculated the velocity incrementst(ΔV) required for departure from Earth and insertion into the orbit around Mars based on the mission opportunity data provided by NASA. Two types of Mars modules - entry type and orbiter type - were considered in this study. We calculated the mass of TPS(thermal protection system) for the entry type Mars module based on the heat transfer rate and heat load from the Mars atmosphere to the surface of the TPS. The heat transfer rate and heat load were obtained through an entry trajectory calculation. For the orbiter type Mars module, we calculated the mass breakdown of the additional spacecraft which is to insert the Mars module into the orbit around Mars. Other mass items were determined by proportioning from the existing Mars modules. This paper finally proposes the payload capacities for each types of Mars modules.

Performance assessment of electrically driven pump-fed LOX/kerosene cycle rocket engine: Comparison with gas generator cycle

Kwak, Hyun-Duck,Kwon, Sejin,Choi, Chang-Ho Elsevier 2018 AEROSPACE SCIENCE AND TECHNOLOGY Vol.77 No.-

<P><B>Abstract</B></P> <P>An electrically driven pump-fed cycle for rocket engine is proposed and a viability of the proposed cycle is assessed compared to a gas generator cycle. The maximum possible thrust level is determined considering the technological maturity of the electric motor. Four types of battery cells were assessed in a screening test for the proposed cycle and the necessity of regenerative cooling for the battery pack is shown. The mass expressions of the proposed cycle and gas generator cycle are derived in terms of pump power and burning time. The basic features are demonstrated with respect to combustion chamber pressure, burning time, and thrust level. The results show that it is favorable to maintain a lower combustion chamber pressure, a longer burning time, and a higher thrust level to remedy the payload penalty incurred when the gas generator cycle is not used. In addition to focusing on the battery pack, the regenerative cooling effect on the battery pack mass is discussed. Further, the impact of optimal battery cell discharge time on the payload is explained. To estimate the payload for the proposed cycle quantitatively, hypothetical low earth orbit (LEO) and KSLV-II sun synchronous orbit (SSO) mission cases are used. In the analysis of the hypothetical LEO mission, it is found that the proposed cycle payloads are only 2.1% to 3.5% lower than those of the gas generator cycle when the combustion chamber pressure is 3.0 MPaA. For the KSLV-II SSO mission, the cargo payload is increased by 3.7% compared to that of gas generator cycle if the proposed cycle is employed for the third-stage engine.</P>