• Journal of Ocean Engineering and Technology
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• v.11 no.3
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• pp.170-179
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• 1997

This paper presents a hybrid navigation system for AUV to locate its position precisely in rough sea. The tracking system is composed of various sensors such as an inclinometer, a tri-axis magnetometer, a flow meter, and a super short baseline(SSBL) acoustic position tracking system. Due to the inaccuracy of the attitude sensors, the heading sensor and the flowmeter, the predicted position slowly drifts and the estimation error of position becomes larger. On the other hand, the measured position is liable to change abruptly due to the corrupted data of the SSBL system in the case of low signal to noise ratio or large ship motions. By introducing a sensor fusion technique with the position data of the SSBL system and those of the attitude heading flowmeter reference system (AHFRS), the hybrid navigation system updates the three-dimensional position robustly. A Kalman filter algorithm is derived on the basis of the error models for the flowmeter dynamics with the use of the external measurement from the SSBL. A failure detection algorithm decides the confidence degree of external measurement signals by using a fuzzy inference. Simulation is included to demonstrate the validity of the hybrid navigation system.

• International Journal of Highway Engineering
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• v.15 no.1
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• pp.155-161
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• 2013

PURPOSES: This study is to develop a road traffic sign recognition and automatic positioning for road facility management. METHODS: In this study, we installed the GPS, IMU, DMI, camera, laser sensor on the van and surveyed the car position, fore-sight image, point cloud of traffic signs. To insert automatic position of traffic sign, the automatic traffic sign recognition S/W developed and it can log the traffic sign type and approximate position, this study suggests a methodology to transform the laser point-cloud to the map coordinate system with the 3D axis rotation algorithm. RESULTS: Result show that on a clear day, traffic sign recognition ratio is 92.98%, and on cloudy day recognition ratio is 80.58%. To insert exact traffic sign position. This study examined the point difference with the road surveying results. The result RMSE is 0.227m and average is 1.51m which is the GPS positioning error. Including these error we can insert the traffic sign position within 1.51m CONCLUSIONS: As a result of this study, we can automatically survey the traffic sign type, position data of the traffic sign position error and analysis the road safety, speed limit consistency, which can be used in traffic sign DB.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.2
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• pp.127-134
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• 2021

This study presents an overhang-type rail traction system using dual brushless AC (BLAC) motors with hall sensors. For an accurate position and moving length control of the designed rail traction system, instantaneous position controller using speed reference model and modified disturbance observer for BLAC motor with hall sensor are proposed. The presented speed reference model is designed to satisfy the required performance of 200 mm/s with proper acceleration and deceleration slopes to reduce mechanical vibration. Through the instantaneous speed reference model, instantaneous position and speed errors can be compensated together. Furthermore, the modified disturbance observer for BLAC motors with low-resolution hall sensors can improve the torque and speed control performance. The proposed disturbance observer is based on an actual motor speed. However, the feedback speed information of the hall sensor is not enough for use in the low-speed region. The practical adopted disturbance observer uses an activation speed band to the actual torque controller of the designed rail traction system. The proposed position control scheme is verified by the MATLAB-Simulink model and a practical manufactured traction system. In the computer simulation and experiments, the proposed position control scheme shows advanced control performance.

• The Journal of Advanced Prosthodontics
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• v.16 no.4
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• pp.221-230
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• 2024

PURPOSE. This in vitro study was conducted to investigate the accuracy of intraoral scanner (IOS) for recording maximal intercuspal position (MIP) and border positions of the mandible. MATERIALS AND METHODS. Maxillary and mandibular master casts were articulated in MIP, protrusive, and lateral interocclusal position sequentially on a semi-adjustable articulator. For each articulation relation, sites of occlusal contacts (SOCs) and sites of clearance (SCs) were identified on the master casts with articulating paper (reference sites). IOS was used to take full arch scans and nine virtual interocclusal records (VIRs) for virtual articulation of models. Virtual SOCs and SCs were detected with 3D processing software and compared to those identified with the articulating paper. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for each articulation relation. RESULTS. For MIP, IOS showed adequate sensitivity and NPV of 100%, and specificity and a PPV of 99%. For protrusive position, the IOS showed a sensitivity and a NPV of 100%, a high PPV of 86%, and a specificity of 83%. For lateral positions, the specificity and the PPV were high (93% and 79%, respectively), but the sensitivity and the NPV were below the clinically acceptable limits (28% and 56%, respectively). CONCLUSION. IOS displayed clinically acceptable accuracy for recording MIP and protrusive border mandibular position. However, IOS had less accuracy for lateral border mandibular position.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1796-1799
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• 1997

This thersis presents precise position control emthods of a 3-PRPS in-parallel manipulator for industrial applications such as assembly of highly integrated semiconductors and microsurgery. Since real-time ontrol is one of the most important issues required for industrial application, the experimental hardware is set up with a VME based DSP controller. In the 3-PRPS parallel mainpulator, structurally existing frictiion at three horizontal links considerably degrades the precise position control. In order to compensate the friction of the horizontal links in the joint space, a disturbance compensation usign disturbance and velocity observers has been proposed and investigated. We analyzed the decision method of eigenvalues of the disturbance observer and the effects of the control resulted form tehsystem model errors. Through a series of simulations and experiments, we see that the methods is capable of compensating variations of the robot parameters such as inertia and damping as well as the joint friction. Experiments show that the disturbance compensation method usign disturbance and velocity observer is very effective to compensate the friction. Compared with conventional PID position control, it decreased position errors ina circular motion by approximately 70%.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.22 no.4
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• pp.411-419
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• 2000

Purpose: This study was aimed at analysis of the changes in the condyle position in subjects with mandibular setback osteotomies Method: Twenty patients were evaluated retrospectively for their changes in the condyle position who underwent surgical mandibular setback using bilateral sagittal split osteotomies with a manual condyle repositioning technique and rigid fixation. The cephalometric and panoramic analysis was performed preoperatively, 1 week, 6 months, and 1 year postoperatively. And postoperative noise, temporomandibular joint pain, and mouth opening were clinically examined 2 months, 4 months, 6 months, 8 months, 10 months, and 12 months postoperatively. Result: The condyles rotated posteriorly and laterally immediately after surgery, and they returned to the preoperative position during follow-up period but it is not significant. The statistical analysis (Paired t-test) showed no significant effects in postsurgical stability. The changes in the condyle position didn't have a significant harmful influence on temporomandibular joint disorder. Conclusion: A careful surgical mandibular setback using manual condyle repositioning and fixation technique will move condyle minimally and that will decrease the relapse and temporomandibular joint disorder.

• Proceedings of the Korea Contents Association Conference
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• 2006.11a
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• pp.788-791
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• 2006

The perception of English labial consonants was investigated via experiment where 40 Korean EFL learners identified nonwords with the target labial consonants [p, b, f, v] in 4 different prosodic locations. The results showed that there was a strong positional effect since the accuracy rates of the four target consonants differed by position. Specifically, the average accuracy rate for the target consonants was higher in the stressed intervocalic position and initial onset position than in the unstressed intervocalic position and final coda position. Further, the accuracy rate for [f] is was high in all prosodic locations except the unstressed intervocalic position. This is unexpected in markedness theory given that fricatives are assumed to be more difficult to learn than stops.

• Journal of Sensor Science and Technology
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• v.28 no.6
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• pp.414-419
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• 2019

An ultrasonic based magnetostrictive position sensor (MPS) provides an indication of real target position. It determines the real target position by multiplying the propagation speed of ultrasonic wave and the time-of-flight between the receiving signals; one is the initial signal by an excitation current and the other is the reflection signal by the ultrasonic wave. The propagation speed of the ultrasonic wave depends on the temperature of the waveguide. Hence, the change of the propagation speed in various environments is a critical factor in terms of the positioning accuracy in the MPS. This means that the influence of the changes in the waveguide temperature needs to be compensated. In this paper, we presents a novel way to improve the positioning accuracy of MPSs using temperature compensation for waveguide. The proposed method used the inherent measurement blind area for the structure of the MPS, which can simultaneously measure the position of the moving target and the temperature of the waveguide without any additional devices. The average positional error was approximately -23.9 mm and -1.9 mm before and after compensation, respectively. It was confirmed that the positioning accuracy was improved by approximately 93%.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.680-684
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• 1996

Welding systems cannot adapt to changes in the joint geometry which may occur due to a variety of reason. Automatic seam tracking technigue is essential to adjust the welding torch position in real time as it moves along the seam. Automatic tracking system must keep the welding speed constant unrelation to the change of the welding path. Therefore, the information from the laser displacement sensor must be converted into the input to operate the X-Y table and to rotate the desired torch position by proposed algorithm. In this research, laser displacement sensor is used as a seam finder in the automatic tracking system. X-Y moving table manipulated by ac servo motor controls the position and velocity of the torch-and-sensor part. DC motor controls the position and velocity of the torch. X-Y table controls the position of sensor and relative position of torch is controlled by dc motor which is mounted at sensor-and-torch part. Sensor is always ahead of torch to preview the weld line. From the experimental results, we could see the possiblity that the laser displacement sensor can be used as a seam finder in welding process and that the seam tracking system controlled by proposed algorithm is well done.

• Journal of Positioning, Navigation, and Timing
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• v.9 no.2
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• pp.117-124
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• 2020

In this paper, the symmetric position drift of the integration approach in pedestrian dead reckoning (PDR) system with dual foot-mounted IMU is analyzed. The PDR system that uses the inertial sensor attached to the shoe is called the IA-based PDR system. Since this system is designed based on the inertial navigation system (INS), it has the same characteristics as the error of the INS, then zero-velocity update (ZUPT) is used to correct this error. However, an error that cannot be compensated perfectly by ZUPT exists, and the trend of the position error is the symmetric direction along the side of the shoe(left, right foot) with the IMU attached. The symmetric position error along the side of the shoe gradually increases with walking. In this paper, we analyze the causes of symmetric position drift and show the results. It suggests the possibility of factors other than the error factors that are generally considered in the PDR system based on the integration approach.