• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2002년도 춘계학술대회 논문집
• /
• pp.190-198
• /
• 2002

In switched reluctance motor(SRM) drive, it is necessary to synchronize the stator phase excitation with the rotor position. Therefore the rotor position information is an essential. Usually optical encoders or resolvers are used to provide the rotor position information. These sensors are expensive and are not suitable for high speed operation. In general, the accuracy of the switching angles is dependent upon the resolution of the encoder and the sampling period of the microprocessor. But the region of high speed, switching angles are fluctuated back and forth from the preset values, witch are cause by the sampling period of the microprocessor. Therefore, the low cost linear encoder suitable for the practical and stable SRM drive is proposed and the control algorithm to provide the switching signals using the simple digital logic circuit is also presented in this paper It is verified from the experiments that the proposed encoder and logic controller can be a powerful candidate for the practical low cost SRM drive.

• Journal of Positioning, Navigation, and Timing
• /
• 제8권4호
• /
• pp.193-200
• /
• 2019

The auto-encoder network which is a good candidate to handle the modeling of the signal strength attenuation is designed for denoising and compensating the distortion of the received data. It provides a non-linear mapping function by iteratively learning the encoder and the decoder. The encoder is the non-linear mapping function, and the decoder demands accurate data reconstruction from the representation generated by the encoder. In addition, the adaptive network width which supports the automatic generation of new hidden nodes and pruning of inconsequential nodes is also implemented in the proposed algorithm for increasing the efficiency of the algorithm. Simulation results show that the proposed method can improve the neural network training surface to achieve the highest possible accuracy of the signal modeling compared with the conventional modeling method.

• 제어로봇시스템학회논문지
• /
• 제7권2호
• /
• pp.117-124
• /
• 2001

In a SRM drive, the on/off angles of each phase switch should be accurately controlled in order to control to torque and speed in a stable way, The accuracy of the switching angles is dependent upon the resolution of the encoder and the sampling period of the microprocessor. However, as the speed increase, the amount of the switching angle deviation from the preset values is also increased by the sampling period of the microprocessor. Therefore, a low cost encoder suitable for a practical and stable SRM drive is proposed and the control algorithm to provide the switching signals using the simple digital logic circuit is also presented in this paper. It is verified from the experiments that the proposed encoder and logic controller can be a powerful candidate a the practical low cost SRM drive.

• International Journal of Precision Engineering and Manufacturing
• /
• 제2권1호
• /
• pp.33-42
• /
• 2001

In switched reluctance motor(SRM) deives, the turn-on and turn-off angles of each phase switch should be accurately controlled for accuracy and efficiency. The accuracy of the switching angles is mainly dependent upon the resolution of the encoder and the sampling period of the microprocessor, that are used to provide the information of the rotor position and to implement a control algorithm of the SRM, respectively. Thus, the higher the speed of the SRM is increased, the larger the amount of the switching angle deviations are from preset turn-on and turn-off angles. Consequently, the motor can not be driven stably high speed region. There fore, a simples and low cost encoder suitable for the practical and stable SRM drive is proposed and the control algorithm to provide the switching signals using a simple digital logic circuit is also presented for a wide speed range operation.

• 한국컴퓨터정보학회논문지
• /
• 제28권2호
• /
• pp.9-17
• /
• 2023

본 논문에서는 베어링의 결함 진단을 위한 단일 클래스 분류의 진동 이상 탐지 시스템을 제안한다. 베어링 고장으로 인해 발생하는 경제적 및 시간적 손실을 줄이기 위해 정확한 결함 진단시스템은 필수적이며 문제 해결을 위해 딥러닝 기반의 결함 진단 시스템들이 널리 연구되고 있다. 그러나 딥러닝 학습을 위한 실제 데이터 채집 환경에서 비정상 데이터 확보에 어려움이 있으며 이는 데이터 편향을 초래한다. 이에 정상 데이터만 활용하는 단일 클래스 분류 방법을 활용한다. 일반적인 방법으로는 AutoEncoder를 통한 압축과 복원 과정을 학습하여 진동 데이터의 특성을 추출한다. 추출된 특성으로 단일 클래스 분류기를 학습하여 이상 탐지를 실시한다. 하지만 이와 같은 방법은 진동 데이터의 주파수 특성을 고려하지 않아서 진동 데이터의 특성을 효율적 추출할 수 없다. 이러한 문제를 해결하기 위해 진동 데이터의 주파수 특성을 고려한 AutoEncoder 모델을 제안한다. 분류 성능은 accuracy 0.910, precision 1.0, recall 0.820, f1-score 0.901이 나왔다. 주파수 특성을 고려한 네트워크 설계로 기존 방법들보다 우수한 성능을 확인하였다.

• 한국정밀공학회지
• /
• 제25권8호
• /
• pp.29-36
• /
• 2008

An optical rotary encoder is easy to implement for automation system applications. In particular, the output of the encoder has a digital form pulse, which is also easy to be connected to a popular digital controller. By using an incremental encoder and a counting device, it is easy to measure angular displacement, as the number of the output pulses is proportional to the rotational displacement. This method can only detect the angular placement once a pulse signal comes out of the encoder. The angular displacement detection period is strongly subject to the change of the angular displacement in case of ultimate low velocity range. They have ultimate long detection period or cannot even detect angular displacement at near zero velocity. This paper proposes an algorithm for detecting angular displacement by using a dual encoder system with two encoders of normal resolution. The angular displacement detecting algorithm is able to keep detection period moderately at near zero velocity and even detect constant angular displacement within nominal period. It is useful for motion control applications in case of changing rotational direction at which there occurs zero velocity. In this paper, various experimental results are shown for the angular displacement detection algorithm.

• 한국멀티미디어학회논문지
• /
• 제22권11호
• /
• pp.1251-1258
• /
• 2019

Intelligent tutoring system enables users to effectively learn by utilizing various artificial intelligence techniques. For instance, it can recommend a proper curriculum or learning method to individual users based on their learning history. To do this effectively, user's characteristics need to be analyzed and classified based on various aspects such as interest, learning ability, and personality. Even though data labeled by the characteristics are required for more accurate classification, it is not easy to acquire enough amount of labeled data due to the labeling cost. On the other hand, unlabeled data should not need labeling process to make a large number of unlabeled data be collected and utilized. In this paper, we propose a semi-supervised learning method based on feedback variational auto-encoder(FVAE), which uses both labeled data and unlabeled data. FVAE is a variation of variational auto-encoder(VAE), where a multi-layer perceptron is added for giving feedback. Using unlabeled data, we train FVAE and fetch the encoder of FVAE. And then, we extract features from labeled data by using the encoder and train classifiers with the extracted features. In the experiments, we proved that FVAE-based semi-supervised learning was superior to VAE-based method in terms with accuracy and F1 score.

• 융합신호처리학회 학술대회논문집
• /
• 한국신호처리시스템학회 2000년도 추계종합학술대회논문집
• /
• pp.145-148
• /
• 2000

Position-determining capacity is a very important condition in equipments for manufacturing semi-conductor or various instruments to measure physical displacement quantities of a moving object in submicron such as a distance of movement, direction, etc. and the accuracy of total system is influenced by detecting accuracy of these equipments. Therefore in this paper we have optically made up laser linear encoder based on optical diffraction principle to measure these displacement quantities and have processed optical signal using hardware-setup. In consequence we had acquired displacement for movement of scale using a diffraction grating by the accuracy of 0.5${\mu}{\textrm}{m}$ and had digitalized moving quantities of scale.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2003년도 ICCAS
• /
• pp.1216-1219
• /
• 2003

The position control is very important in semiconductor manufacturing devices, precision machining tools, precision measuring instruments, etc. The accuracy of measurement for the distance in these devices affect on the performance of the whole devices. Therefore, in those precision instruments, a sensing device that can measure the distance of movement with high-precision resolution is required. In this paper, a novel hybrid (digital and analog) type encoder is proposed. It is shown that from several experiments, a high-resolution angular position measurement device can be designed with a low cost incremental encoder and a DSP controller.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2011년도 전력전자학술대회
• /
• pp.312-313
• /
• 2011

Recently, many industrial electric vehicles have been developed using various ac-motor drive technologies including field oriented vector control. Generally, a magnetic encoder is installed to have resistance to vibration and dust, and it is cost-effective. However, it is difficult to get an accurate rotor speed for high performance of vector control, because a resolution of the magnetic encoder is low and its phase accuracy is poor. In order to overcome this hardware problem, this study proposes a speed measurement algorithm using moving window for low-resolution magnetic encoder. This algorithm is experimentally tested and successfully applied to traction application of industrial electric vehicle.