• Journal of Advanced Research in Ocean Engineering
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• v.3 no.3
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• pp.136-148
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• 2017

The paper presents dual arm ROV manipulation using deep reinforcement learning. The purpose of this underwater manipulator is to investigate and excavate natural resources in ocean, finding lost aircraft blackboxes and for performing other extremely dangerous tasks without endangering humans. This research work emphasizes on a self-learning approach using Deep Reinforcement Learning (DRL). DRL technique allows ROV to learn the policy of performing manipulation task directly, from raw image data. Our proposed architecture maps the visual inputs (images) to control actions (output) and get reward after each action, which allows an agent to learn manipulation skill through trial and error method. We have trained our network in simulation. The raw images and rewards are directly provided by our simple Lua simulator. Our simulator achieve accuracy by considering underwater dynamic environmental conditions. Major goal of this research is to provide a smart self-learning way to achieve manipulation in highly dynamic underwater environment. The results showed that a dual robotic arm trained for a 3DOF movement successfully achieved target reaching task in a 2D space by considering real environmental factor.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.623-629
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• 2002

The spectrum of impulse response signal from an impulse hammer testing is widely used to obtain frequency response function(FRF) of the structure. However the FRFs obtained from impact hammer testing have not only leakage errors but also finite record length errors when the record length for the signal processing is not sufficiently long. The errors cannot be removed with the conventional signal analyzer which treats the signals as if they are always steady and periodic. Since the response signals generated by the impact hammer are transient and have damping, they are undoubtedly non-periodic. It is inevitable that the signals be acquired for limited recording time, which causes the finite record length error and the leakage error. In this paper, the errors in the frequency response function of multi degree of freedom system are formulated theoretically. And the method to remove these errors is also suggested. This method is based on the optimization technique. A numerical example of 3-dof model shows the validity of the proposed method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.10
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• pp.792-798
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• 2002

The spectrum of impulse response signal from an impulse hammer testing is widely used to obtain frequency response function (FRF) of the structure. However the FRFs obtained from impact hammer testing have not only leakage errors but also finite record length errors when the record length for the signal processing is not sufficiently long. The errors cannot be removed with the conventional signal analyzer which treats the signals as if they are always steady and periodic. Since the response signals generated by the impact hammer are transient and have damping, they are undoubtedly non-periodic. It is inevitable that the signals be acquired for limited recording time, which causes the finite record length error and the leakage error. In this paper, the errors in the frequency response function of multi degree of freedom system are formulated theoretically. And the method to remove these errors is also suggested. This method is based on the optimization technique. A numerical example of 3-dof model shows the validity of the proposed method.

• Journal of Power Electronics
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• v.3 no.2
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• pp.115-123
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• 2003

This paper presents analysis, design and simulation for the indirect field orientation control (IFOC) of induction machine drive system. The dynamic performance of the IFOC under nominal and detuned parameters of the induction machine is established. A conventional proportional plus integral-derivative (PI-D) two-degree-of-freedom controller (2DOFC) is designed and analysed for an ideal IFOC induction machine drive at nominal parameters with the desired dynamic response. Varying the induction machine parameters causes a degredation in the dynamic response for disturbance rejection and tracking performance with PI-D 2DOF speed controller. Therefore, conventional controllers can nut meet a wide range of speed tracking performance under parameter variations. To achieve high- dynamic performance, a proposed robust fuzzy logic controllers (RFLC) for d-axis rotor flux, d-q axis stator currents and rotor speed have been designed and analysed. These controllers provide robust tracking and disturbance rejection performance when detuning occurres and improve the dynamic behavior. The proposed REL controllers provide a fast and accurate dynamic response in tracking and disturbance rejection characteristics under parameter variations. Computer simulation results demonstrate the effectiveness of the proposed REL controllers and a robust performance is obtained fur IFOC induction machine drive system.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2631-2633
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• 2004

This paper describes the construction of a half sphere screen driving tilting simulator that can perform six degree-of-freedom( DOF) motions simmulator to a tilting train. The mathematical equations of Tilting Train dynamics are first derived from the 6-DOF bicycle model and incorporated with the bogie. carbody, and suspension subsystems. The equations of motion are then programmed by visual C++ code. To achieve the simulator functions. a motion platform that is constructed by six electric-driven actuators is designed. and its kinetics/inverse kinetics analysis is also conducted. Driver operation signals such as carbady angle, accelerator. and tilting positions are measured to trigger the Tilting dynamics calculation and further actuate the cylinders by the motion platform control program. In addition. a digital PID controller is added to achieve the stable and accurate displacements of the motion platform. The experiments prove that the designed simulator is adequate in performing some special rail mad driving situations discussed in this paper.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.5
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• pp.1-9
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• 2011

Nowadays it is necessary to replace electrical wires with another intelligent connection method because the consumers, who have much experience with mobile smart devices, are expecting easier and smarter connectivity in their home electronics such as wireless linking. In this paper a bidirectional CEC control scheme is newly proposed to expand the controllability from one to two way in a millimeter band image transmission system because two degree of freedom controllability presents more intelligent convenience in HDMI interface systems. Experimental study shows the feasibility of the proposed system as an advanced image transmission solution in millimeter band including an intelligent 2 DOF CEC interface with the performance result of 3.0 Gbps transmission band for 1080p full-HD image steaming.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2000.05a
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• pp.138-141
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• 2000

공정제어시스템을 위한 제어기로써 현재까지는 PID 제어기가 보편화되어 적용되어 왔으나 비선형 시스템이나 복잡한 시스템 제어를 위해서는 목표치 추종특성이 우수하며 환경이나 공정 파라미터변화에 둔감하여 외란에 대한 영향이 적은 제어기가 요구된다. PID 제어기로는 이러한 목적을 달성하는 데에 한계가 있기 때문에 이를 해결하기 위한 연구들이 활발히 수행되어 목표치 추종성능과 외란 억제를 동시에 만족토록 하는 다양한 2자유도 PID 제어시스템들이 제안되었고, 본 연구에서는 먼저 현재까지 제안된 2자유도 PID 제어시스템들 중 제어성능이 가장 우수한 것으로 나타난 목표치 필터형 2자유도 PID 제어시스템(Target Value Filter Type 2-DOF PID Control System: 이하 TVF-2DOF) [2]보다 우수한 2자유도PID 제어시스템을 제안하고, 이를 바탕으로 2자유도 선행필터(Pre-Filter)부분에 지능제어기법의 하나인 퍼지로직을 적용함으로써 PID 제어기의 장점과 퍼지로직의 장점을 동시에 활용하는 지능형 튜닝(Tuning)기법에 관한 연구를 수행하였고, 지능형 시스템이 2자유도 PID 제어시스템들보다 목표치 추종 성능 및 외란억제효과가 우수하다는 사실을 컴퓨터 시뮬레이션을 통해 입증하였다. 시스템으로는 유량 제어 밸브가 사용되었다.

• The Journal of Korea Robotics Society
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• v.9 no.1
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• pp.11-19
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• 2014

In this paper, an external torque estimation problem in one-degree-of-freedom (1-DOF) flexible-joint robot equipped with a joint-torque sensor is revisited. Since a sensor torque from the joint-torque sensor is distorted by two dynamics having a spring connection, i.e., motor dynamics and link dynamics of a flexible-joint robot, a model-based estimation, rather than a simple linear spring model, should be required to extract external torques accurately. In this paper, an external torque estimation algorithm for a 1-DOF flexible-joint robot is proposed. This algorithm estimates both an actuating motor torque from the motor dynamics and an external link torque from the link dynamics simultaneously by utilizing the flexible-joint robot model and the Kalman filter estimation based on random-walk model. The basic structure of the proposed algorithm is explained, and the performance is investigated through a custom-designed experimental testbed for a vertical situation under gravity.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.565-570
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• 2011

In this paper, the analytical tuning rules of the proportional-integral-derivative (PID) controller have been derived for a broad class of stable, integrating, and unstable processes without time delay. On the basis of the renowned internal model control (IMC) design principles and the two-degree-of-freedom (2DOF) control structure, the proposed method can be effectively used for obtaining the enhanced performances of both the disturbance rejection as well as the set-point tracking problems, since the design scheme is simple, straightforward, and can be easily implemented in the process industry. Several processes without time delay are employed to demonstrate the improved closed-loop performance of the proposed controller design in compared with the other well-known design methods in terms of the same degree of robustness.

• International Journal of Aeronautical and Space Sciences
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• v.14 no.2
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• pp.152-161
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• 2013

This paper presents a control effectiveness analysis of the hawkmoth Manduca sexta. A multibody dynamic model of the insect that considers the time-varying inertia of two flapping wings is established, based on measurement data from the real hawkmoth. A six-degree-of-freedom (6-DOF) multibody flight dynamics simulation environment is used to analyze the effectiveness of the control variables defined in a wing kinematics function. The aerodynamics from complex wing flapping motions is estimated by a blade element approach, including translational and rotational force coefficients derived from relevant experimental studies. Control characteristics of flight dynamics with respect to the changes of three angular degrees of freedom (stroke positional, feathering, and deviation angle) of the wing kinematics are investigated. Results show that the symmetric (asymmetric) wing kinematics change of each wing only affects the longitudinal (lateral) flight forces and moments, which implies that the longitudinal and lateral flight controls are decoupled. However, there are coupling effects within each plane of motion. In the longitudinal plane, pitch and forward/backward motion controls are coupled; in the lateral plane, roll and side-translation motion controls are coupled.