• Current Research on Agriculture and Life Sciences
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• v.32 no.3
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• pp.159-163
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• 2014

Agricultural unmanned helicopters have become a new paradigm for aerial application. Yet, such agricultural helicopters require easy and affordable attitude control systems. Therefore, this study presents an affordable attitude measurement system using a DCM (direction cosine matrix) algorithm that would be applied to agricultural unmanned helicopters. An IMU using a low-cost MEMS and an algorithm to estimate the attitude of the helicopter were applied in a gimbals structure to evaluate the accuracy of the attitude measurements. The estimation errors in the attitude were determined in comparison with the true angles determined by absolute position encoders. The DCM algorithm and sensors showed an accuracy of about 1.1% for the roll and pitch angle estimation. However, the accuracy of the yaw angle estimation at 3.7% was relatively larger. Such errors may be due to the magnetic field of the stepping motor and encoder system. Notwithstanding, since the intrinsic behavior of the agricultural helicopter remains steady, the determination of attitude would be reliable and practical.

• Transactions on Control, Automation and Systems Engineering
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• v.4 no.3
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• pp.231-238
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• 2002

In this paper, we present a new approach to autopilot design for skid-to-turn missiles which may have severe aerodynamic cross-couplings and nonlinearities with angle of attack. The model of missile motion is derived in the maneuver plane and, based on that model, pitch, yaw, and roll autopilot are designed. They are composed of a nonlinear term which compensates for the aerodynamic couplings and nonlinearities and a linear controller driven by the measured outputs of missile accelerations and angular rates. Besides the outputs, further information such as Mach number, dynamic pressure, total angle of attack, and bank angle is required. With the proposed autopilot and simple estimators of bank angle and total angle of attack, it is shown by computer simulations that the induced moments and some aerodynamic nonlinearities are properly compensated and that the performance is superior to that of the conventional ones.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.10
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• pp.1022-1028
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• 2008

This article presents an omni-tread snake robot that designed to locomote on narrow space and rough terrain. The omni-tread snake robot comprises three segment, which are linked to each other by 2 degrees of freedom joints for the pitch and yaw motion. Moving tracks on all four sides of each segment guarantee propulsion even when the robot rolls over. The 2 DOF joint are actuated by 2 servo motors which produce sufficient torque to lift the one leading or trailing segments up and overcome obstacles. This paper applies articulated steering technique to get omni-tread snake robot's kinematics model.

• International Journal of Automotive Technology
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• v.8 no.4
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• pp.445-453
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• 2007

This paper presents a robust controller design approach for improving vehicle dynamic roll motion performance and guaranteeing the closed-loop system stability in spite of vehicle parameter variations resulting from aging elements, loading patterns, and driving conditions, etc. The designed controller is linear parameter-varying (LPV) in terms of the time-varying parameters; its control objective is to minimise the $H_{\infty}$ performance from the steering input to the roll angle while satisfying the closed-loop pole placement constraint such that the optimal dynamic roll motion performance is achieved and robust stability is guaranteed. The sufficient conditions for designing such a controller are given as a finite number of linear matrix inequalities (LMIs). Numerical simulation using the three-degree-of-freedom (3-DOF) yaw-roll vehicle model is presented. It shows that the designed controller can effectively improve the vehicle dynamic roll angle response during J-turn or fishhook maneuver when the vehicle's forward velocity and the roll stiffness are varied significantly.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.601-604
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• 1994

This paper describes an effective method to estimate a position of an automous vehicle equipped with a single CCD-camera along indoor passageways. Using the sequential image data from the self-movement of the vehicle, the position is estimated by integrating the approximated motion parameters. The detection of the yaw angle that is one of the motion parameter is difficult in general, e.g. slip or error for noise, therefore the different detection is presented, which is, without shaft encoders, based on a projection function for 2D-image data and a cross-correlation function so as to be robust for noise. The approximated geometric function to estimate the position is used to reduce the computational effort. To verify the effectiveness of the method, the analysis and the computational results are shown through the simulations. Furthermore, the experimental results by using the test vehicle for the real indoor passageway are shown.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.30-35
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• 2010

The railway vehicle is a multi-body system running on the track which consists of carbody, bogie and wheelset, each of components is connected with rigid mass, spring and damper. each of components has translation motions of longitudinal (X axis), lateral(Y axis) and vertical(Z axis) direction, and rotation motions of X, Y, Z axis which are named Rolling, Pitching and Yawing. The vibration mode of railway vehicle is difficult to find the characteristics of motion during the operation on the track because these happen to independence or duplication motion caused by vehicle, wheel/rail and track irregularity etc. This paper presents the result of ramp test to show the bounce, roll, pitch and yaw mode frequency of the railway vehicle.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.4
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• pp.26-31
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• 2008

A precision four-degree-of-freedom measurement system has been developed for simultaneous measurement of four motion errors of a linear stage, which include straightness and angular errors, The system employs a retro-reflector to detect the straightness errors and a plane mirror to detect the angular errors. A common-path compensation method for laser beam drift is put forward, and the experimental results show that the influences of beam drift on four motion errors can be reduced simultaneously. In comparison with the API 5D laser measuring system, the accuracy for straightness measurement is about ${\pm}1.5{\mu}m$ within the measuring range of ${\pm}650{\mu}m$, and the accuracy for pitch and yaw measurements is about ${\pm}1.5$ arc-seconds within the range of ${\pm}600$ arc-seconds.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.222-227
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• 2001

The time simulation of slow drift motions of moored FPSO in waves is presented. The equation of motion based on Cummin's theory of impulse responses are employed, and are consisted of horizonal plane -surge, sway and yaw. The added mass coefficients, wave damping coefficients, first order wave exciting forces and the second order wave drift forces involved in the equations are obtained from a three-dimensional panel method in the frequency domain. The mooring lines are modeled quasistatically as catenary for chains and touchdown. As for numerical example, time domain analyses are carried out for a box-type FPSO in long crest irregular wave condition.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.6
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• pp.66-71
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• 2007

Development of a locomotive mechanism for the capsule type endoscopes will largely enhance their ability to diagnose disease of digestive organs. As a part of it, there should be provided a detection device of their position in human organs for the purpose of observation and motion control. In this paper, a permanent magnet outside human body was employed to project magnetic field on a capsule type endoscope, while its position dependent flux density was measured by three hall-effect sensors which were orthogonally installed inside the capsule. In order to detect the 2-D position data of the capsule with three hall-effect sensors including the roll, pitch and yaw angle, the permanent magnet was extra translated during the measurement. In this way, the 2-D coordinates and three rotation angles of a capsule endoscope on the same motion plane with the permanent magnet could be detected. The working principle and performance test results of the capsule position detection device were introduced in this paper showing that they could be also applied to 6-DOF position detection.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.9
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• pp.124-129
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• 1997

The purpose of this study is to predict the stability and frequency response of multipurpose vehicle. The vehicle model has seven degrees of freedom. The motion equations are derived by using Lagrangian equation and linearized. The positions of eigenvalues of model which are dominated by lateral velocity, yaw rate, roll rate of sprung mass are used to predict the stability of motion. The resonse of sprung mass to steering wheel is simulated in time domain. It is predicted that the roll response of sprung mass would rather be improved by modifying the position of eigenvalues. The responses of sprung mass to steering wheel are also simulated in frequency domain. The magnitude and phase plots of gains are evaluated in driver's steering input frequency range.