• Journal of Advanced Marine Engineering and Technology
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• v.32 no.7
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• pp.1068-1079
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• 2008

Tilt and heading angles information of a remotely operated vehicle (ROV) are very important in underwater navigation. This paper presents a low.cost tilt and heading estimation system. Three single.axis rate gyros, a tri-axis accelerometer, and a tri-axis magnetometer are used. Output signals coming from these sensors are fused by two Kalman filters. The first Kalman filter is used to estimate roll and pitch angles and the other is for heading angle estimation. By using this method, we have obtained tilt (roll and pitch angles) and heading information which are reliable over long period of time. Results from experiments have shown the performance of the presented system.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.15-16
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• 2012

The estimation of crack damages is studied using the radio frequency system and tilt switch sensors in RC beams. If load is received on the center of the flexible specimen, sensor housing using cement mortar of the flexible specimen will be destroyed, and these are become to send signals of damages at the radio frequency system connected with tilt switch sensors. This study is fundamental research for the estimation of the damage using tilt switch sensors in RC beams.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.11
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• pp.966-972
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• 2013

Measurement or estimation of tilt angle is necessary for balancing robot such as Segway which is considered as a next generation transportation vehicle. However, it requires high-cost accurate sensors to hold balancing during stationary and moving situations. In this paper, a tilt angle estimation of a plane rotating in a vertical plane using low-cost sensors. Estimation using a set of 2-axis orthogonal accelerometers along with an inaccurate rate gyro has been considered. Feasibility and performance of the proposed technique has been verified through some experimental results.

• IEMEK Journal of Embedded Systems and Applications
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• v.17 no.3
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• pp.149-155
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• 2022

This paper proposes a method for estimating the road surface condition and tilt angle using an inertial measurement unit (IMU) to improve the safety in the use of mobility aids for the elderly. The measurements of the accelerometers of the IMU usually include the accelerations caused by not only the gravitational force but also linear and rotational motions. Thus, the gravitational accelerations are first extracted using several physical constraints and then incorporated into the Kalman filter to estimate the tilt angle. In addition, because the magnitudes of the accelerations produced by the rotational motions (roll and pitch motions) vary with the road surface condition, a criterion based on such accelerations is presented to classify the condition of the road surface. The obtained road surface condition and tilt angle are finally combined to provide the safety information (e.g., safe, warning, and danger) for the user to improve the walking safety. Experiments were carried out and the results showed that the proposed method can provide the condition of the road surface, the tilt of the road surface, and the safety information correctly.

• Smart Structures and Systems
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• v.15 no.2
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• pp.489-503
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• 2015

Response estimation at unmeasured locations using the limited number of measurements is an attractive topic in the field of structural health monitoring (SHM). Because of increasing complexity and size of civil engineering structures, measuring all structural responses from the entire body is intractable for the SHM purpose; the response estimation can be an effective and practical alternative. This paper investigates a response estimation technique based on the Kalman state estimator to combine multi-sensor data under non-zero mean input excitations. The Kalman state estimator, constructed based on the finite element (FE) model of a structure, can efficiently fuse different types of data of acceleration, strain, and tilt responses, minimizing the intrinsic measurement noise. This study focuses on the effects of (a) FE model error and (b) combinations of multi-sensor data on the estimation accuracy in the case of non-zero mean input excitations. The FE model error is purposefully introduced for more realistic performance evaluation of the response estimation using the Kalman state estimator. In addition, four types of measurement combinations are explored in the response estimation: strain only, acceleration only, acceleration and strain, and acceleration and tilt. The performance of the response estimation approach is verified by numerical and experimental tests on a simply-supported beam, showing that it can successfully estimate strain responses at unmeasured locations with the highest performance in the combination of acceleration and tilt.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.404-408
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• 2009

Gas pipelines in bridges, roads and subway construction sections can undergo abrupt stress and vibration changes. To protect human life from any gas leakage accidents induced by the abrupt stress and vibration, the gas pipeline system needs to be continuously monitored. The estimation method of pipeline stress using MEMS wireless tilt sensor has been developed and its validity has been evaluated using a lab test bench.

• Journal of Korean Physical Therapy Science
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• v.18 no.4
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• pp.73-79
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• 2011

Purpose : This study is to know how position change in high-heels affects sacral tilt angle. 15 healthy women aged 21.87(standard deviation=3.54) were tested. Method : Lumbar and sacral tilt angle was measured by radiography barefooted, and after 15 mins of application time, they were measured in the same way in high-heels. Result : There was not notable difference in lumbar lordosis, lumbosacral angle, and sacral tilt angle. However, there was differences in change degree, which was measured by estimation data of [post-pre)/pre]${\times}$100. Conclusion : There was no notable difference in lumbar lordosis, lumbosacral angle, and sacral tilt angle, but as there were differences in change degree, research about how women's lumbar change when heel height increases is needed.

• Journal of Aerospace System Engineering
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• v.3 no.2
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• pp.12-19
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• 2009

The research for the fatigue analysis is regarded greatly as important in aerospace field. Moreover, a study on the fatigue characteristic is very actively progressing. In this study, the fatigue life estimation was performed for Flaperon Joint which has FCL(fatigue critical location) of tilt-rotor UAV. The Flaperon Joint should be taken the various loads by several missions profiles of UAV. The fatigue load spectrum of Flaperon Joint is generated by the standard mission segment for the tilt-rotor UAV, and this spectrum is used for the fatigue test and analysis. The in-house fatigue analysis program is applied to calculate the fatigue life based on Stress-Life(S-N) method. The S-N curve is generated from the S-N data of Mil-Handbook by second order polynomial regression method. Moreover, the coefficient of determination is used to ensure how accuracy it has. In addition, the Goodman equation is used to consider the mean stress effect for evaluating more accurate fatigue life. Finally, the result of fatigue analysis is verified by comparing with the fatigue test result for the Flaperon Joint.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.6
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• pp.546-551
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• 2011

Tilt sensor is required to control the attitude of the biped robot when it walks on an uneven terrain. Vision sensor, which is used for recognizing human or detecting obstacles, can be used as a tilt angle sensor by comparing current image and reference image. However, vision sensor alone has a lot of technological limitations to control biped robot such as low sampling frequency and estimation time delay. In order to verify limitations of vision sensor, experimental setup of an inverted pendulum, which represents pitch motion of the walking or running robot, is used and it is proved that only vision sensor cannot control an inverted pendulum mainly because of the time delay. In this paper, to overcome limitations of vision sensor, Kalman filter for the multi-rate sensor fusion algorithm is applied with low-quality gyro sensor. It solves limitations of the vision sensor as well as eliminates drift of gyro sensor. Through the experiment of an inverted pendulum control, it is found that the tilt estimation performance of fusion sensor is greatly improved enough to control the attitude of an inverted pendulum.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.3
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• pp.605-613
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• 2009

In this paper, we studied for the real-time azimuthal measurement of HMD (Head Mounted Display) to control the tele-operated vision system on the mobile robot. In the preexistence tele-operated vision system, a joystick was used to control the pan-tilt unit of the remote camera system. To give the sense of presence to the tele-operator, we used a HMD to display the remote scene, measured the rotation angle of the HMD on a real time basis, and transmitted the measured rotation angles to the mobile robot controller to synchronize the pan-tilt angles of remote camera with the HMD. In this paper, we suggest an algorithm for the real-time estimation of the HMD rotation angles using feature points extraction from pc-camera image. The simple experiment is conducted to demonstrate the feasibility.