• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37C no.12
• /
• pp.1289-1295
• /
• 2012

An adaptive digital predistortion (PD) technique is proposed for linearization of power amplifiers (PAs) in multiple-input multiple-output (MIMO) transmitters. We consider a PD structure equipped with only one combined feedback path while conventional systems have multiple feedback paths. Hence, the proposed structure is much simpler than that of multiple feedback paths. Based on the structure, a new PD algorithm is derived. The simulation results show that linearization performance of the proposed method is almost the same as the conventional multiple feedback technique while the former is much simpler to implement than the latter.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.3
• /
• pp.155-159
• /
• 2013

In this paper, a nonlinear matrix inequality problem and a nonlinear optimization problem are proposed for obtaining a structured static output feedback controller. The proposed nonlinear optimization problem has LMI (Linear Matrix Inequality) constraints and a nonlinear objective function. Using the conditional gradient method, the nonlinear optimization problem can be solved. A numerical example shows the effectiveness of the proposed approach.

• Journal of Ocean Engineering and Technology
• /
• v.19 no.5 s.66
• /
• pp.58-64
• /
• 2005

In this paper, a feedback linearizing anti-sway control law, using a 2-D model for container cranes, is investigated. The equations of motion are first derived from Lagrange's equation. Then, by substituting the sway dynamics into the trolley dynamics, a reduction of variables from three (trolley, hoist, sway) to two (trolley, hoist) is pursued. The anti-sway control law is designed based on the Lyapunov stability theorem. The proposed control law guarantees the uniform asymptotic stability of the closed-loop system. The simulation results of the derived control law, using MATLAB/Simulink, are compared with those of the sliding mode control law, noted in previous literature. Also, experimental results using a 3-D pilot crane are provided.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.20 no.6
• /
• pp.768-773
• /
• 2010

This paper presents the performance verification of the optimal state feedback controller via inverted pendulum systems. The proposed method generates the optimal control inputs satisfying both the constrained input and the performance specification. In addition, it reduces the steady-state error by adopting the integral control technique. In order to verify the performance of the proposed method, we apply both the proposed method and the general state feedback control to an inverted pendulum, CEM-IP-01 in the experiment.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.21 no.5
• /
• pp.40-46
• /
• 2013

Automatic swing door for an automotive application is considered. The equation of motion for a driver side swing door is introduced and gravity cancellation control scheme is adapted. The control scheme supposed to cancel the moment due to the tilt of the car. A speed control is suggested for door operation automation but the output of the speed control is not suppose to be precise as for the manufacturing system control. In the frame of the velocity control of the door, feedback linearization was applied for collision detection. The collision detection performance is satisfactory. The estimate of the magnitude of disturbance due to the collision is close to the actual magnitude of disturbance. Simulation study has been performed to gain insight into the system behavior. Also real test on the prototype hardware has been performed for verification purpose.

• Proceedings of the KIEE Conference
• /
• 2006.10c
• /
• pp.291-294
• /
• 2006

This paper presents a decentralized input-output feedback linearizing controller for a multi-machine power system. Firstly, the controller is designed using input-output feedback linearization for modified outputs. Then we present a guideline for selecting gains of the controller and parameters in the modified outputs. Simulations illustrate the effectiveness of the proposed control scheme and the selection guideline.

• Journal of Institute of Control, Robotics and Systems
• /
• v.13 no.1
• /
• pp.1-5
• /
• 2007

Many nonlinear controllers for the power system are based on nonlinear models involving the power angle as an element of the state, and therefore the reference value for the power angle is needed. As this reference value is not generally available, it is difficult to apply such nonlinear control methods in practice. To deal with this problem, we present an input-output feedback linearizing control scheme by selecting the output as a combination of the squared voltage and the relative frequency. It is shown that the internal dynamics are locally stable with controllable damping, and that the frequency remains bounded for all time. Simulations illustrate the effectiveness of the proposed method.

• Proceedings of the KIEE Conference
• /
• 1997.11a
• /
• pp.453-455
• /
• 1997

일반적으로 제철공정에서 각 공정사이의 철판의 속도와 장력은 브라이드롤을 이용하여 제어하는데 여기서 입력 측의 브라이드롤은 장력을 제어하고 출력 측의 브라이드롤은 공정의 속도를 제어한다. 이와 같은 방법은 시스템 기동의 순간을 포함하여 공정속도의 변경이 있을 경우 제철 공정 상에서는 특히 철판의 높은 탄성에 기인하여 시스템이 상당히 불안정하게 된다. 본 논문에서는 각 전동기가 정해진 역할에 따라 독립적으로 장력 혹은 공정속도를 제어하고 장력의 모델링에서 비선형의 요소를 되먹임하여 원래의 시스템을 선형화시켰고 이때 미분관측기를 이용하였다. 이 제어기의 장점은 무엇보다도 독립적인 역할의 분담으로 인해 다수의 전동기로 확장이 용이하도록 하는 것이다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2015.05a
• /
• pp.673-676
• /
• 2015

Digital Pre-Distortion (DPD) is a linearization technique for nonlinear power amplifiers (PAs) by implementing inverse function of the PA at baseband digital stage. To obtain proper DPD parameters, a feedback path is required to convert the PA output to a baseband signal, and a memory is also needed to store the feedback signals. DPD parameters are usually found by an adaptive algorithm from the feedback samples. However, for the adaptive algorithm to converge to a reliable solution, long feedback samples are required, which increases convergence time and hardware complexity. In this paper, we propose a DPD technique that requires relatively short feedback samples. From the observation that the convergence time of the adaptive algorithm highly depends on the initial condition, this paper iteratively utilizes the feedback samples while keeping and using the converged DPD parameters at the former iteration as the initial condition at the current iteration. Computer simulation results show that the proposed method performs better than the conventional technique while the former requires much shorter feedback samples than the latter.

• Journal of the Society of Naval Architects of Korea
• /
• v.45 no.5
• /
• pp.469-476
• /
• 2008

In this paper, it is shown that an input-output (I/O) feedback linearized controller can be designed rationally by utilizing the time-scale properties of heave and pitch for an underwater vehicle. It is assumed that the dynamics of the vehicle is restricted to the vertical plane. An output-feedback control is designed, which stabilizes steady cruising paths. It is shown that the vehicle dynamics with acceleration as output becomes minimum phase. The dynamics can be transformed into a reduced system through a kind of partial linearization and singular perturbation technique. The reduced system is not only minimum phase but also exactly I/O linearizable via feedback. The I/O dynamic characteristics of the heave and pitch modes can be made linear and decoupled. Furthermore it becomes independent of cruising condition such as vehicle velocity. This study may help for designing autopilot systems for underwater vehicles.