• 제어로봇시스템학회논문지
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• 제12권3호
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• pp.248-254
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• 2006

It is necessary to improve the exactness and adaptation of the working environment for the intelligent robot system. The vision sensor have been studied for a long time at this points. However, it has many processes and difficulties for the real usages. This paper proposes a visual servoing in the virtual environment to support OLP(Off-Line-Programming) path compensation and supplement the problem of complexity of the old kinematical calibration. Initial robot path could be compensated by pixel differences between real and virtual image. This method removes the varies calibrations and 3D reconstruction process in real working space. To show the validity of the proposed approach, virtual space servoing with stereo camera is carried out with WTK and openGL library for a KUKA-6R manipulator and updated real robot path.

• 한국공작기계학회논문집
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• 제15권4호
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• pp.44-48
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• 2006

Recently, demand the ultra precision product which is increasing rapidly is used extensively frontier industry field such as semi-conductor, computer, aerospace, precision machine. Ultra precision processing is the portion that is very needed to NT in the field of mechanical engineering. The latest date, together with radical advancement of electronic and photonics industry, necessity of ultra precision processing is on the increase for the manufacture of various kernel parts those are connected with these industrial fields. Specially, require motion accuracy of high resolution of nm order in stroke of hundreds millimeters according as diameter of processing object great and processing accuracy rises. In this case ,the response speed absolute delay because inertial mass of moving part is very large. Therefore, real time motion error compensation becomes very hardly. In this paper, we used ultra precision cutting unit(UPCU) to cope such problem. a UPCU is designed and tested to obtain sub-micrometer from accuracy in diamond turning of flat surfaces. The thermal growth spindle error is compensated for real time using a UPCU driven by piezoelectric actuator along with a laser encoder displacement sensor.

• 대한의용생체공학회:의공학회지
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• 제28권2호
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• pp.294-299
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• 2007

For efficient and accurate diagnosis of ultrasound images, appropriate time gain compensation(TGC) and dynamic range(DR) control of ultrasound echo signals are important. TGC is used for compensating the attenuation of ultrasound echo signals along the depth, and DR controls the image contrast. In recent ultrasound systems, these two factors are automatically set by a system and/or manually adjusted by an operator to obtain the desired image quality on the screen. In this paper, we propose an algorithm to find the optimized parameter values far TGC and DR automatically. In TGC optimization, we determine the degree of attenuation compensation along the depth by dividing an image into vertical strips and reliably estimating the attenuation characteristic of ultrasound signals. For DR optimization, we define a novel cost function by properly using the characteristics of ultrasound images. We obtain experimental results by applying the proposed algorithm to a real ultrasound(US) imaging system. The results verify that the proposed algorithm automatically sets values of TGC and DR in real-time such that the subjective quality of the enhanced ultrasound images may be sufficiently high for efficient and accurate diagnosis.

• Smart Structures and Systems
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• 제25권6호
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• pp.719-732
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• 2020

Real-time hybrid simulation (RTHS) which combines physical experiment with numerical simulation is an advanced method to investigate dynamic responses of structures subjected to earthquake excitation. The desired displacement computed from the numerical substructure is applied to the experimental substructure by a servo-hydraulic actuator in real time. However, the magnitude decay and phase delay resulted from the dynamics of the servo-hydraulic system affect the accuracy and stability of a RTHS. In this study, a robust stability analysis procedure for a general single-degree-of-freedom structure is proposed which considers the uncertainty of servo-hydraulic system dynamics. For discussion purposes, the experimental substructure is a portion of the entire structure in terms of a ratio of stiffness, mass, and damping, respectively. The dynamics of the servo-hydraulic system is represented by a multiplicative uncertainty model which is based on a nominal system and a weight function. The nominal system can be obtained by conducting system identification prior to the RTHS. A first-order weight function formulation is proposed which needs to cover the worst possible uncertainty envelope over the frequency range of interest. Then, the Nyquist plot of the perturbed system is adopted to determine the robust stability margin of the RTHS. In addition, three common delay compensation methods are applied to the RTHS loop to investigate the effect of delay compensation on the robust stability. Numerical simulation and experimental validation results indicate that the proposed procedure is able to obtain a robust stability margin in terms of mass, damping, and stiffness ratio which provides a simple and conservative approach to assess the stability of a RTHS before it is conducted.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.195-198
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• 1997

This paper proposes the effective compensation method of the rotor time constant of induction motor. An indirect vector control method is highly dependent on the motor parameters. To solve the problem of performance degradation due to parameter variation in an indirect vector control of induction motor, we compensate the rotor time constant by current error feedback. The proposed method is a simple on-line rotor time constant compensation method using the information from terminal voltages and currents. As the current error, difference between current command and estimated current, approaches to zero, the value of rotor time constant in an indirect vector controller follows the real value of induction motor. This scheme is valid transient region as well as steady state region regardless of low or high speed. This method is verified by computer simulation. For this, we constructed the simulation model of induction motor, indirect vector controller and current regulated PWM (CRPWM) voltage source inverter (VSI) using SIMULINK in MATLAB.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 V
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• pp.2645-2648
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• 2003

In this paper, real-time and reconfiguable hardware filter for face recognition is proposed and implemented on FPGA chip using verilog-HDL. In general, face recognition is considerably difficult because it is influenced by noises or the variation of illumination. Some of the commonly used filters such s histogram equalization filter, contrast stretching filter for image enhancement and illumination compensation filter are proposed for realizing more effective illumination compensation. The filter proposed in this paper was designed and verified by debugging and simulating on hardware. Experimental results show that the proposed filter system can generate selective set of real-time reconfiguable hardware filters suitable for face recognition in various situation.

• 한국컴퓨터그래픽스학회논문지
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• 제6권3호
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• pp.35-40
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• 2000

There are two problems in H.26X compression technique. One is compressing time in encoding process and the other is degradation of the decoded video quality due to high compression rate. For transferring moving pictures in real-time, it is required to adopt massively high compression. In this case, there are a lot of losses of an original video data and that results in degradation of quality. Especially degradation called by blocking artifact may be produced. The blocking artifact effect is produced by DCT-based coding techniques because they operate without considering correlation between pixels in block boundaries. So it represents discontinuity between adjacent blocks. This paper describes methods of quality compensation for H.26x decoded data and enhancing encoding speed for real-time operation. Our goal of the quality compensation is not to make the decoded video identical to a original video but to make it perceived better through human eyes. We suggest an algorithm that reduces block artifact and clears decoded video in decoder. To enhance encoding speed, we adopt new four-step search algorithm. As shown in the experimental result, the quality compensation provides better video quality because of reducing blocking artifact. And then new four-step search algorithm with $MMX^{TM}$ implementation improves encoding speed from 2.5 fps to 17 fps.

• 한국정보통신학회논문지
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• 제12권3호
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• pp.527-533
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• 2008

움직임 보상은 고화질의 실시간 비디오 응용에 있어서 언제나 주된 병목을 초래한다. 따라서 실시간 비디오 응용에서는 움직임 보상을 수행하는 고속의 전용 하드웨어를 필요로 한다. 여러 동영상 부호화 방식에서 영상프레임은 픽셀의 블록으로 분할된다. 일반적으로 움직임 보상은 이전 프레임으로부터 움직임을 추정하여 현재의 블록을 예측하게 된다. 움직임 보상에 사용되는 화소 정밀도가 높을수록 보다. 좋은 성능을 갖지만 연산량은 증가하게 된다. 본 논문에서는 1/4 화소 정밀도를 지원하는 H.264/AVC 부호화기에 적합한 움직임 보상기의 아키텍처를 연구하였다. 설계된 움직임 보상기는 전치 배열과 휘도 6-tap 필터 3개를 사용하여 높은 하드웨어 이용률을 갖게 하였으며 내부 메모리의 크기를 감소시켰다. VHDL을 사용하여 기술하였으며, Xilinx ISE툴을 사용하여 합성하고, Modelsim_6.1i를 사용하여 검증하였다. 설계된 움직임 보상기는 단지 3개의 6-tap 필터만을 사용하면서 매크로블록 당 640 클럭 사이클에 수행하였다. 본 논문에서 제안하는 움직임 보상기는 실시간 비디오 처리를 요구하는 분야에 응용 가능할 것으로 사료된다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 춘계학술대회 논문집
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• pp.148-153
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• 1998

In order to control thermal deformation of machine origin of machine tools due to internal and external heat sources, the real-time compensation system has been developed. First, GMDH models were constructed to estimate thermal deformation of machine origin for a vertical machining center through the measurement of deformation data and temperature data of specific points on the machine tool. Thermocouples and gap sensors are used respectively for measurement. These models are nonlinear equations with high-order polynomials and implemented in a multilayered perceptron type network structure. Secondly, work origin shift method were developed by implementing digital I/O interface board between CNC controller and IBM-PC. The work origin shift method is to shift the work origin by the compensation amounts which is calculated by pre-established GMDH model. From the experimental result, thermal deformation of machine origin was reduced to below $\pm$5${\mu}{\textrm}{m}$.

• International journal of advanced smart convergence
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• 제5권1호
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• pp.34-46
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• 2016

Networked Control System (NCS) has evolved in the past decade through the advances in communication technology. The problems involved in NCS are broadly classified into two categories namely network issues due to network and control performance due to system network. The network problems are related to bandwidth allocation, scheduling and network security, and the control problems deal with stability analysis and delay compensation. Various delays with variable length occur due to sharing a common network medium. Though most delays are very less and mostly neglected, the network induced delay is significant. It occurs when sensors, actuators, and controllers exchange data packet across the communication network. Networked induced delay arises from sensor to controller and controller to actuator. This paper presents an adaptive delay compensation process for efficient control. Though Smith predictor has been commonly used as dead time compensators, it is not adaptive to match with the stochastic behavior of network characteristics. Time delay adaptive compensation gives an effective control to solve dead time, and creates a virtual environment using the plant model and computed delay which is used to compensate the effect of delay. This approach is simulated using TrueTime simulator that is a Matlab Simulink based simulator facilitates co-simulation of controller task execution in real-time kernels, network transmissions and continuous plant dynamics for NCS. The simulation result is analyzed, and it is confirmed that this control provides good performance.