• Title/Summary/Keyword: Suboptimal

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Study on optimal steering control of an unmanned cart (無人 搬送車의 最適 操向制御)

  • 김옥현;정성종
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.11 no.1
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    • pp.19-25
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    • 1987
  • An optimal control procedure is presented for steering of an unmanned cart which has two motored wheels on its left and right side. Steering, running and stopping are enabled by controlling the motor speed independently. An optimal proportional-plus-integral control is employed to eliminate steady state error which is sustained by a simple proportional control for tracking a circular arc path. A simple and readily-implemented suboptimal control is also examined. The suboptimal control gives comparable performance and therefore provides an effective approach for industrial application of the unmanned cart. Effects of design parameters of unmanned cart such as forward velocity, wheel radius and position of sensor are investigated. It is shown that within the practicable values of the parameters the controlled performance improves rapidly with increase of those parameters then the improvement becomes negligible, which suggests base values over which the parameters should be taken.

(J,J')-lossless factorization and $H^{\infty}$ control in discrete-time systems (이산시간 시스템에서 (J,J')-lossless 분해와 $H^{\infty}$ 제어)

  • 정은태;이재명;박홍배
    • Journal of the Korean Institute of Telematics and Electronics B
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    • v.31B no.5
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    • pp.65-72
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    • 1994
  • We resolve the suboptimal $\infty$ control problem using (J,J')-lossless coprime factorization by transforming the linear fractional transformation (LFT) into chain scattering description (CSD) in discrete-time systems. The condition transformed LFT into CSD is that the inverse matrix of $P_{21}$ of standard plant exists. But, this paper presents the method of transforming LFT into CSD for 4-block problem in case that the inverse matrix of $P_{21}$ of standard plant does not exist and parameterization of the all suboptimal $\infty$T controllers using (J,J')-lossless coprime factorization. It is shown that this method can resolve the suboptimal $\infty$ control problem solving only two Riccati equations in discrete-time systems.

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Suboptimal Adaptive Handover Method Considering Uplink and Downlink Signals (상.하향 링크 신호를 고려한 준 최적의 적응적 하드 핸드오버 기법)

  • Cho, Young-Bo;Han, Seung-Youp;Bang, Keuk-Joon;Hong, Dae-Sik
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.12C
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    • pp.1273-1279
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    • 2006
  • In this paper, we address the design of adaptive handover schemes based on the signal strength measurement for cellular communications systems. Conventional handover algorithms, which are based only on the downlink measurement, cannot guarantee the required uplink quality because uplink channel can differ greatly from downlink channel quality. Therefore, we proposes a new suboptimal adaptive handover algorithm that considers both the uplink and downlink channel quality in order to achieve the best cell selection gains when there is a wide difference between the uplink and downlink signal quality. Simulation results show that the proposed scheme achieves better performance compared to conventional handover schemes.

Suboptimal Homing Guidance Law by Synthesis of the Aided Loop for Impact Angle Constraint (충돌각 구속조건을 위한 보조루프 합성을 통한 준최적 호밍 유도법칙)

  • Lee, Jin-Ik
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.35 no.11
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    • pp.1006-1012
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    • 2007
  • In this paper, a suboptimal homing guidance law for the homing missiles with an impact angle constraint is presented. Unlike general LQ optimal control, the aided loop ensuring some degrees of freedom for the constraint is introduced. Then an optimal feedback loop in consideration of the aided loop is designed by using Schwartz inequality. The aided loop is synthesized with the optimal control to produce the guidance command. Furthermore, to investigate the characteristics of the guidance law we carry out the comparative studies with other guidance laws. The results of the various computer simulations show the good performance of the proposed law.

Parallel Code Acquisition Techniques in Chip-Asynchronous DS/SS System (직접 수열 대역 확산 통신에서 비동기 위상 서명 수열의 병렬 부호 획득 기법)

  • 오미정;윤석호;송익호;배진수
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.27 no.7A
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    • pp.635-640
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    • 2002
  • We investigate optimal and suboptimal decision rules for parallel code acquisition in chip asynchronous direct-sequence spread-spectrum systems. The conventional decision rule for parallel acquisition is to choose the largest correlator output of a receiver. However, such a scheme is optimum only for chip synchronous models. In this paper, an optimal decision rule is derived based on the maximum-likehood criterion for chip asynchronous models. A simpler suboptimal decision rule is also discussed. The performance of the optimum and suboptimum decision rules is compared to that of the conventional decision rule. Numerical results show that, for chip asynchronous models, both the optimal and suboptimal decision rules outperform the conventional decision rule.

Performance of Two-User Two-Way Amplify-and-Forward Relaying Systems with Scheduling

  • Fang, Zhaoxi;Li, Guosheng;Li, Jun
    • ETRI Journal
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    • v.33 no.5
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    • pp.689-694
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    • 2011
  • In this paper, we study scheduling schemes for two-user two-way wireless relaying systems. Two transmission modes are considered: point-to-point direct transmission and two-way amplify-and-forward relaying. An optimal scheduling scheme that opportunistically selects the best transmission mode for each user is proposed to minimize the sum bit error rate (BER). The performance lower bound of the optimal scheduling scheme is analyzed, and closed-form expression of the lower-bound BER is derived. However, for optimal scheduling, the scheduler requires the knowledge of channel state information (CSI) of all links. To reduce the feedback information of CSI, we also propose a suboptimal scheduling scheme that selects the transmission mode using only the CSI of two direct links. Simulation results show that there are 4 dB to 8 dB gains for the proposed optimal and suboptimal schemes over the fixed direct transmission and fixed two-way relayed transmission scheme. The performance gap between the optimal and suboptimal scheduling schemes is small, which implies a good trade-off between implementation complexity and system performance.

Suboptimal Adaptive Filters for Stochastic Systems with Multisensor Environment

  • Shin, Vladimir;Ahn, Jun-Il
    • 제어로봇시스템학회:학술대회논문집
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    • 2004.08a
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    • pp.2045-2050
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    • 2004
  • An optimal combination of arbitrary number correlated estimates is derived. In particular, for two estimates this combination represents the well-known Millman and Bar-Shalom-Campo formulae for uncorrelated and correlated estimation errors, respectively. This new result is applied to the various estimation problems as least-squares estimation, Kalman filtering, and adaptive filtering. The new approximate adaptive filter with a parallel structure is proposed. It is shown that this filter is very effective for multisensor systems containing different types of sensors. Examples demonstrating the accuracy of the proposed filter are given.

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(Suboptimal Detection Thresholds for Tracking in Clutter) (클러터 환경에서의 표적 추적을 위한 준최적의 검출 문턱값)

  • Jeong, Yeong-Heon;Sin, Han-Seop
    • Journal of the Institute of Electronics Engineers of Korea SC
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    • v.39 no.2
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    • pp.176-181
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    • 2002
  • In this paper, we consider the optimal control of detection threshold to minimize the conditional expectation of mean-square state estimation error for a probabilistic data association (PDA) filter. Earlier works on this problem involved the cumbersome graphical optimization algorithm or time-consuming numerical optimization algorithm. Using the numerical approximation of information reduction factor, we obtained the suboptimal detection threshold in a closed-form. This results are very useful for real- time implementation.

Approximate Dynamic Programming-Based Dynamic Portfolio Optimization for Constrained Index Tracking

  • Park, Jooyoung;Yang, Dongsu;Park, Kyungwook
    • International Journal of Fuzzy Logic and Intelligent Systems
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    • v.13 no.1
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    • pp.19-30
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    • 2013
  • Recently, the constrained index tracking problem, in which the task of trading a set of stocks is performed so as to closely follow an index value under some constraints, has often been considered as an important application domain for control theory. Because this problem can be conveniently viewed and formulated as an optimal decision-making problem in a highly uncertain and stochastic environment, approaches based on stochastic optimal control methods are particularly pertinent. Since stochastic optimal control problems cannot be solved exactly except in very simple cases, approximations are required in most practical problems to obtain good suboptimal policies. In this paper, we present a procedure for finding a suboptimal solution to the constrained index tracking problem based on approximate dynamic programming. Illustrative simulation results show that this procedure works well when applied to a set of real financial market data.

A Simple LQ Suboptimal Control Scheme for a DC-DC Step-Down Converter Based on Approximate Affine Discretization of Continuous-Time PWM Linear Systems (연속시간 PWM 선형 시스템의 근사 어파인 이산화를 통한 DC-DC 강압 컨버터의 간단한 LQ 준최적 제어 기법)

  • Lee, Jae-Young;Park, Jin-Bae;Choi, Yoon-Ho
    • Proceedings of the KIEE Conference
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    • 2011.07a
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    • pp.1872-1873
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    • 2011
  • This paper presents a discrete-time approximate linear model of the continuous-time pulse-width-modulated linear system, and then, by employing the resultant model, a simple LQ suboptimal control scheme is proposed for a DC-DC step-down buck converter. The proposed scheme effectively regulates the output voltage to the desired level, which is also verified by the numerical simulation.

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