• Title/Summary/Keyword: Optimal control problems

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A Study on the Posture Control of a Humanoid Robot (휴머노이드 로봇의 자세 제어에 관한 연구)

  • Kim Jin-Geol;Lee Bo-Hee;Kong Jung-Shik
    • Journal of Institute of Control, Robotics and Systems
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    • v.11 no.1
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    • pp.77-83
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    • 2005
  • This paper deals with determination of motions of a humanoid robot using genetic algorithm. A humanoid robot has some problems of the structural instability basically. So, we have to consider the stable walking gait in gait planning. Besides, it is important to make the smoothly optimal gait for saving the electric power. A mobile robot has a battery to move autonomously. But a humanoid robot needs more electric power in order to drive many joints. So, if movements of walking joints don't maintain optimally, it is difficult for a robot to have working time for a long time. Also, if a gait trajectory doesn't have optimal state, the expected life span of joints tends to be decreased. To solve these problems, the genetic algorithm is employed to guarantee the optimal gait trajectory. The fitness functions in a genetic algorithm are introduced to find out optimal trajectory, which enables the robot to have the less reduced jerk of joints and get smooth movement. With these all process accomplished by a PC-based program, the optimal solution could be obtained from the simulation. In addition, we discuss the design consideration for the joint motion and distributed computation of the humanoid, ISHURO, and suggest its result such as the structure of the network and a disturbance observer.

The optimal control for a nonlinear system using the feedback linearization (피드백 선형화를 이용한 비선형 시스템에 대한 최적 제어)

  • Lee, Jong-Yong;Lee, Won-Seok
    • Journal of the Institute of Electronics Engineers of Korea TE
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    • v.42 no.3
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    • pp.25-30
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    • 2005
  • Nonlinear optimal control problems lead to Hamilton-Tacobi equations which are not analytically solvable for most practical problems. This difficulty has led to the development of suboptimal nonlinear design techniques such as controller design based on feedback linearization(FL). In this paper, we present some simple examples where the optimal answer can be found for the optimal controller, FL controller and linear controller and determine its relative performance. As a result, we get the condition of a nonlinear system for the FL controller to an optimal design.

A method for deciding weighting matrices in a linear discrete time optimal regulator problems to locate all poles in the specified region

  • Shin, Jae-Woong;Shimemura, Etsujiro;Kawasaki, Naoya
    • 제어로봇시스템학회:학술대회논문집
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    • 1988.10b
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    • pp.729-733
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    • 1988
  • In this paper, a new procedure for selecting weighting matrices in linear discrete time quadratic optimal control problems (LQ-problem) is proposed. In LQ problems, the quadratic weighting matrices are usually decided on trial and error in order to get a good response. But using the proposed method, the quadratic weights are decided in such a way that all poles of the closed loop system are located in a desired area for good responses as well as for stability and values of the quadratic cost functional are kept less then a specified value. The closed loop systems constructed by this method have merits of LQ problems as well as those of pole assignment problems. Taking into consideration that little is known about the relationship among the quadratic weights, the poles and the values of cost functional, this procedure is also interesting from the theoretical point of view.

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Optimal Two Degrees-of-Freedom Based Neutral Point Potential Control for Three-Level Neutral Point Clamped Converters

  • Guan, Bo;Doki, Shinji
    • Journal of Power Electronics
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    • v.19 no.1
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    • pp.119-133
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    • 2019
  • Although the dual modulation wave method can solve the low-frequency neutral point potential (NPP) fluctuation problem for three-level neutral point clamped converters, it also increases the switching frequency and limits the zero-sequence voltage. That makes it harmful when dealing with the NPP drift problem if the converter suffers from a long dead time or asymmetric loads. By introducing two degrees of freedom (2-DOF), an NPP control based on a search optimization method can demonstrate its ability to cope with the above mentioned two types of NPP problems. However, the amount of calculations for obtaining an optimal 2-DOF is so large that the method cannot be applied to certain industrial applications with an inexpensive digital signal processor. In this paper, a novel optimal 2-DOF-based NPP control is proposed. The relationships between the NPP and the 2-DOF are analyzed and a method for directly determining the optimal 2-DOF is also discussed. Using a direct calculation method, the amount of calculations is significantly reduced. In addition, the proposed method is able to maintain the strongest control ability for the two types of NPP problems. Finally, some experimental results are given to confirm the validity and feasibility of the proposed method.

Decentralized Optimal Control of Distributed Parameter Systems (분포정수계의 분산형 최적제어에 관한 연구)

  • 안두수;이명규
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.39 no.10
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    • pp.1075-1085
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    • 1990
  • This paper presents a new method for the optimal control of the distributed parameter systems by a decentralized computational procedure. Approximate lumped parameter models are derived by using the Galerkin method employing the Legendre polynomials as the basis functions. The distributed parameter systems, however, are transformed into the large scale lumped parameter models. And thus, the decentralized control scheme is introduced to determine the optimal control inputs for the obtained lumped parameter models. In addition, an approach to block pulse functions is applied to solve the optimal control problems of the obtained lumped parameter models. The proposed method is simple and efficient in computation for the optimal control of distributed paramter systems. Illustrative examples given to demonstrate the validity of the presently proposed method.

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OPTIMAL CONTROL PROBLEMS FOR SEMILINEAR EVOLUTION EQUATIONS

  • Jeong, Jin-Mun;Kim, Jin-Ran;Roh, Hyun-Hee
    • Journal of the Korean Mathematical Society
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    • v.45 no.3
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    • pp.757-769
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    • 2008
  • This paper deals with the existence of optimal controls and maximal principles for semilinear evolution equations with the nonlinear term satisfying Lipschitz continuity. We also present the necessary conditions of optimality which are described by the adjoint state corresponding to the linear equations without a condition of differentiability for nonlinear term.

PARALLEL OPTIMAL CONTROL WITH MULTIPLE SHOOTING, CONSTRAINTS AGGREGATION AND ADJOINT METHODS

  • Jeon, Moon-Gu
    • Journal of applied mathematics & informatics
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    • v.19 no.1_2
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    • pp.215-229
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    • 2005
  • In this paper, constraint aggregation is combined with the adjoint and multiple shooting strategies for optimal control of differential algebraic equations (DAE) systems. The approach retains the inherent parallelism of the conventional multiple shooting method, while also being much more efficient for large scale problems. Constraint aggregation is employed to reduce the number of nonlinear continuity constraints in each multiple shooting interval, and its derivatives are computed by the adjoint DAE solver DASPKADJOINT together with ADIFOR and TAMC, the automatic differentiation software for forward and reverse mode, respectively. Numerical experiments demonstrate the effectiveness of the approach.

The Analysis of the optimal Control problem for the Singular System with the Generalized State Space Model (일반화된 상태모델로 주어진 싱귤라 시스템의 최적제어문제 해석)

  • Kwae-Hi lee
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.36 no.4
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    • pp.301-304
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    • 1987
  • The Optimal Control Problems for the singular system with the Generalized state space model are considered. It is shown that when the system is singular, the dimension can be reduced by coordinate transformation and the equivalent nonsingular system is got. After we have nonsingular system, the solution for the optimal control problem can be got by Riccati equation.

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Robust Control of an Anti-Lock Eddy Current Type Brake System (잠김 방지 기능을 가지는 비접촉식 와전류형 제동장치의 견실제어)

  • 이갑진;박기환
    • Journal of Institute of Control, Robotics and Systems
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    • v.4 no.4
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    • pp.525-533
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    • 1998
  • A conventional contact type brake system which uses a hydraulic system has mny Problems such as time delay response due to pressure build-up, brake pad wear due to contact movement, bulky size, and low braking performance in high speed region. As vehicle speed increases, a more powerful brake system is required to ensure vehicle safety and reliability. In this work, a contactless brake system of an eddy current type is proposed to overcome problems. Optimal torque control which minimizes a braking distance is investigated with a scaled-down model of an eddy current type brake. It is possible to realize optimal torque control when a maximum friction coefficient (or desired slip ratio) corresponding to road condition is maintained. Braking force analysis for a scaled-down model is done theoretically and experimentally compensated. To accomplish optimal torque control of an eddy current type brake system, a sliding mode control technique which is, one of the robust nonlinear control technique is developed. Robustness of the sliding mode controller is verified by investigating the braking performance when friction coefficient is varied. Simulation and experimental results will be presented to show that it has superior performance compared to the conventional method.

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Variance Reductin via Adaptive Control Variates(ACV) (Variance Reduction via Adaptive Control Variates (ACV))

  • Lee, Jae-Yeong
    • Journal of the Korea Society for Simulation
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    • v.5 no.1
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    • pp.91-106
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    • 1996
  • Control Variate (CV) is very useful technique for variance reduction in a wide class of queueing network simulations. However, the loss in variance reduction caused by the estimation of the optimum control coefficients is an increasing function of the number of control variables. Therefore, in some situations, it is required to select an optimal set of control variables to maximize the variance reduction . In this paper, we develop the Adaptive Control Variates (ACV) method which selects an optimal set of control variates during the simulation adatively. ACV is useful to maximize the simulation efficiency when we need iterated simulations to find an optimal solution. One such an example is the Simulated Annealing (SA) because, in SA algorithm, we have to repeat in calculating the objective function values at each temperature, The ACV can also be applied to the queueing network optimization problems to find an optimal input parameters (such as service rates) to maximize the throughput rate with a certain cost constraint.

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