• Journal of Institute of Control, Robotics and Systems
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• v.18 no.11
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• pp.1040-1044
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• 2012

We design a NCS (Networked Control System) where the communication between sensors and controllers takes place over a USN (Ubiquitous Sensor Network). In order to measure time delays between sensors and controllers in real time, we design an algorithm to measure RTT (Round Trip Time) between USN nodes, and implement it into TinyOS of USN. By using the measured time delays, we construct the Smith predictor to compensate the time delays between sensors and controllers in real-time. For the real time experiment, we simulate the dynamic plant model, controller, and USN interface using Real-Time Windows Target provided in MATLAB. The USN interface in the Simulink model consists of serial ports, which connect the plant output and controller with USN nodes. The experiment results show that the time delays between sensors and controllers are precisely measured in real time; the Smith predictor appropriately compensates the time delays; and the stability is achieved in the closed-loop of the NCS.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.11
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• pp.1136-1141
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• 2014

This paper proposes a new contact type ball tracking sensor to improve the control performance of a low cost ball-and-beam system. It is well-known that the impulsive measurement noise contained in ball position measurement is one of the factors which severely degrades the ball-and-beam control performance. The impulsive ball position measurement noises often appear under the sporadical ball floating on the beam. This fact motivates us to devise a simple analog preprocessing circuit to determine whether the ball loses the contact or not. Once the abnormal ball position measurement is detected, the design problem of the ball tracking sensor can be cast into the typical state estimation problem with missing data. In order to tackle the real-time implementation issue, a steady-state Kalman filter is applied to the problem. Through the experimental results, the usefulness of the proposed scheme is demonstrated.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.6
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• pp.579-583
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• 2012

The purpose of this paper is to suggest IDE (Incremental Displacement Estimation) algorithm for the previously proposed visually servoed paired structured light system. The system is composed of two sides facing with each other, each with one or two lasers with a 2-DOF manipulator, a camera, and a screen. The 6-DOF displacement between two sides can be estimated by calculating the positions of the projected laser beams and rotation angles of the manipulators. In the previous study, Newton-Raphson or EKF (Extended Kalman Filter) has been used as an estimation algorithm. Although the various experimental tests have validated the performance of the system and estimation algorithms, the computation time is relatively long since aforementioned algorithms are iterative methods. Therefore, in this paper, a non-iterative incremental displacement estimation algorithm which updates the previously estimated displacement with a difference of the previous and the current observed data is introduced. To verify the performance of the algorithm, experimental tests have been performed. The results show that the proposed non-iterative algorithm estimates the displacement with the same level of accuracy compared to the EKF with multiple iterations with significantly less computation time.

• Journal of Bio-Environment Control
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• v.12 no.2
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• pp.63-67
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• 2003

Cucumber fruits requires a lot of labor to harvest in time in Korea, since the fruits are cut and grabbed by hand. In this study, we developed an end-effector for robotic harvester of cucumber fruits. Its development involved the integration of an end-effector system with a PC compatible, DC motors, and a motor controller board. Software, written in Pic-basic, combined the functions of motor control with various circumstances. Cucumber's properties were measured and analyzed for precision of the end-effector. The results were similar to those of other vegetables. Properties including hardness of cucumber fruits were used as basic data for development of a harvester.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.6
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• pp.698-704
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• 1999

There are several types of defects of SMDs mounted on PCB, that is, missing components, misalignment, wrong parts and poor solder joints. This research study mainly focuses on measuring of deviation of SMD leads using the partial image of component, not using the full image. This processing based on the partial image has the advantage of the reduction in calculation time compared to the full image. Since position of lead is calculated with respect of the reduction in calculation time compared to the full image. Since position of lead is calculated with respect to pad, the accuracy of the system is not dependent on percise positioning stage. The grabbed image of gray scale is converted into binary format using a cutomatic threshold. After small fragments in the image is removed by a series of morphology operations such as opening and closing, the centroids of PCB pads and SMD leads is obtained together with labeling of blobs. Translational shift and rotationial angle of SMD are succedingly estimated using above information and chip data. The expression that can calculate the maximum deviation of leads with respect to PCB pads has been derived, and inferior mounting of SMD is judged by a given criterion. Some experiments have been executed to verify this measuring scheme.

• 제어로봇시스템학회:학술대회논문집
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• 1986.10a
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• pp.286-289
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• 1986

항법(navigation)은 기준좌표계에 대한 항체(vehicle)의 위치나 속도를 알아내기 위한 것으로 이를 위한 시스템이 관성항법장치(inertial navigation system-INS)이며 항법기능을 수행하기 위하여 항체에 놓여진 쎈서의 관성성질을 이용한다. INS는 specific force와 관성 각속도의 측정에서 얻은 데이타를 처리함으로 그 기능을 수행한다. 스트랩다운 INS(SINS)는 관성항법장치의 한 종류로 analytic INS라고도 하는데 기준좌표축을 유지하기 위하여 안정테이블을 사용하지 않고 쎈서들을 항체에 직접 부착시켜 초기상태와 현재상태와의 사이에 상대적인 회전방향을 해석적으로 계산한다. INS의 성능은 수많은 오차원(error source)의 함수로 주어지며 이 오차원 중에는 주위환경에 의한 것도 있고 INS 구성에 사용된 기구(instruments)와 관련된 것도 있다. INS 를 해석하는 목적은 항법의 정확도를 알아보는데 있으며 또한 각각의 오차원의 값을 추정하는 것도 부가적인 목적이 된다. 이러한 오차의 추정치는 사양(specification)을 모르는 부품의 성능을 식별하는데 사용될 수 있다. 따라서 INS를 해석함으로 INS를 구성하는 어떤 부품에 대한 성능이 어느정도 개선을 필요로 하는가 알 수 있다. 본 논문에서는 SINS의 오차원을 크게 고도계의 불확실성, 중력의 편향과 이상, 가속도계의 불확실성, 자이로의 불확실성의 네 그룹으로 나누어 상호분산해석(covariance analysis)방법으로 각 오차원이 시스템에 미치는 영향을 알아보았다.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.3
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• pp.218-223
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• 2007

The dissipation of high-power ultrasonic energy at the faces of the defect causes an increase in temperature. It is resulted from localized selective heating in the vicinity of cracks because of the friction effect. In this paper the measurement of size and direction of crack using UET(Ultrasound Excitation Thermography) is described. The ultrasonic pulse energy is injected into the sample in one side. The hot spot, which is a small area around the crack tip and heated up highly, is observed. The hot spot, which is estimated as the starting point of the crack, is seen in the nearest position from the ultrasonic excitation point. Another ultrasonic pulse energy is injected into the sample in the opposite side. The hot spot, the ending point of the crack, is seen in the closest distance from the injection point also. From the calculation of the coordinates of both the first hot spot and the second hot spot observed, the size and slope of the crack is estimated. In the experiment of STS fatigue crack specimen(thickness 14mm), the size and the direction of the crack was measured.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.1
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• pp.12-17
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• 2014

In this paper, we propose a controller capable of reducing the effect of measurement errors under AC and DC noise. Typically, the control system measures data through a sensor. If sensor noise is included in a controller via the feedback channel, the signal is distorted and the entire system cannot work normally. Therefore, some appropriate action to counter the measurement error effect is essential in the controller design. Our controller is equipped with a gain-scaling factor and a compensator to reduce the effect of measurement error in the feedback signal. Also, we use a switching control strategy to enhance the performance of the controller regarding convergence speed. Our proposed controller can therefore effectively reduce the AC and DC noise of the sensor. We analyze the proposed controller by Laplace transform technique and our control method is verified via MATLAB simulation.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.1
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• pp.37-45
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• 2002

A method of measuring the length of defects on the wall and restructuring the defect image is proposed based on the estimation algorithm of a camera orientation, which uses the declination angle of a laser slit beam. The estimation algorithm of the horizontally inclined angle of CCD camera adopts a 3-dimensional coordinate transformation of the image plane where both the laser beam and the original image of the defects exist. The estimation equation is obtained by using the information of the beam projected on the wall and the parameters of this equation are experimentally obtained. With this algorithm, the original image of the defect can be reconstructed as an image normal to the wall. From the result of a series of experiments, the measuring accuracy of the defect is measured within 0.5% error bound of real defect size under 30 degree of the horizontally inclined angle. The proposed algorithm provides the method of reconstructing the image taken at any arbitrary horizontally inclined angle as the image normal as the wall and thus, it enables the accurate measurement of the defect lengths by using a single camera and a laser slit beam.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.3
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• pp.208-219
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• 2002

A novel measurement method to obtain the 6-DOF motions of arbitrary rigid bodies is proposed in this paper. The method adopts a specially fabricated mirror called 3-facet mirror, which looks like a triangular pyramid haying an equilateral cross-sectional shape. The mirror is mounted on the objects to be measured, illuminated by a laser beam having circular profile, and reflects the laser beam in three different directions. Three PSDs(position sensitive detector) detect the three beams reflected by the mirror, respectively. From the signals of the PSDs, we can calculate the 3-dimensional position and orientation of the 3-facet mirror, and thus enabling us to determine the 3-dimensional position and orientation of the objects. In this paper, we model the relationship between the 3-dimensional position and orientation of an object in motion and the outputs of three PSDs. A series of experiments are performed to demonstrate the effectiveness and accuracy of the proposed method. The experimental results show that the proposed sensing system can be an effective means of obtaining 3-dimensional position and orientation of arbitrary objects and provide resonable measurement accuracy.