• Journal of Ocean Engineering and Technology
• /
• v.17 no.4
• /
• pp.66-72
• /
• 2003

This paper proposes an optimum, problematic design for structural and control systems, taking a 3-D truss structure as an example. The structure is subjected to initial static loads and time-varying disturbances. The structure is controlled by a state feedback H$_{\infty}$ controller which suppress the effects of disturbances. The design variables are the cross sectional areas of truss members. The structural objective function is the structural weight. For the control objective, we consider two types of performance indices, The first function represents the effect of the initial loads. The second function is the norm of the feedback gain, These objective functions are in conflict with each other but are transformed into one control objective by the weighting method. The structural objectives is treated as the constraint, By introducing the second control objective which considers the magnitude of the feedback gain, we can create a design to model errors.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2001.10a
• /
• pp.164-168
• /
• 2001

In this paper, we introduce a new sliding surface adaptable to arbitrary initial conditions. The surface is initially designed to pass given intial errors and subsequently moves towards a predetermined surface via rotating or/and shifting. We call it as a moving sliding surface (MSS) comparing with the conventional ones, for instances, employed by Slotine and Sastry. Using the MSS, it is shown that the tracking is much faster than conventional one without increasing the magnitude of discontinuous control gain. To demonstrate some advantages of the proposed method, we apply the MSS to the path tracking control of a two-degree-of-freedom robotic manipulator subjected to external disturbances.

• Journal of the Korean Society for Precision Engineering
• /
• v.13 no.5
• /
• pp.74-83
• /
• 1996

An iterative tuning technique is derived for PID controllers which are widely used in industries. The tuning algorithm is based upon a fuzzy indirect reasoning method and an iterative technique. The PID gains for the first tuning action are determined by a method which is modified from the Ziegler-Nichols step response method. The first PID gains are determined to obtain a control performance so close to a design performance that the following tuning process can be made effectively. The design paramaters are given as time-domain variables which human is familiar with. The results of simulation studies show that the proposed tuning method can produce an effective tuning for arbitrary design performances.

• Journal of the Korea Concrete Institute
• /
• v.15 no.2
• /
• pp.254-262
• /
• 2003

In this study, the results of applying cold weather concreting mixed with Accelerator for Freeze Protection(AFP) to full scale structures are presented. Since the determination of W/C and amount of AFP significantly have an effect on strength gain and protection of frost damage in early, a full investigation is needed to determine these values at stage of nux design. The flowability of fresh cold weather concreting with AFP was similar to the same W/C. Lower loss of workability and initial slump flow of concrete using superplasticizer of polycarboxylic ester than that of melamine sulphonate showed that polycarboxylic ester was more effective on elapsed time. Temperature histories of specimens located in insulation boxes at the site was similar to that of structures. Thus, it is cleared that simple adiabatic curing method is effective for evaluating in-place concrete strength than specimens cured by sealing method. The investigation results of development of compressive strength of cold weather concreting included AFP with curing methods by logistic curves indicated that AFP can be effective to gain strength at lower temperature than normal curing temperature. In field testing, vinyl sheets were placed over the concrete sections and AFP enabled concrete to gain $5N/{mm}^2$ to protect frost damage in early ages and specified compressive strength of concrete at 28 days under average temperature of $-2^{\circ}C$ (lowest temperature was $-12^{\circ}C$) during site application.