• Journal of Institute of Control, Robotics and Systems
• /
• v.7 no.12
• /
• pp.1031-1035
• /
• 2001

In this paper, a robust recursive control approach for nonlinear system, which is based on Lyapunov stability, is proposed. The proposed method can apply to extended systems including cascaded systems and the stability is guaranteed in the sense of Lyapunov. The recursive design procedure so called “robust recursive control approach” is used to find a stabilizing robust controller and simultaneously estimate the uncertainty parameters. First, a nonlinear model with uncertainties whose bounds are unknown is derived. Then, unknown bounds of uncertainties are estimated. By using these estimates, the stabilizing robust controller is updated at each step. This approach is applied to the pitch autopilot design of a nonlinear missile system and simulation results indicate good performance.

• Proceedings of the KIEE Conference
• /
• 1998.11a
• /
• pp.326-328
• /
• 1998

This paper presents an optimal fuzzy power system stabilizer to damp out low frequency oscillation. The fuzzy logic controllers has been applied to a power system stabilizing controllers. But the design of a fuzzy logic power system stabilizer relies on empirical and heuristic knowledge of human experts as well as many trial-and-errors in general. This paper presents the optimal design method of the fuzzy logic stabilizer using the genetic algorithm, which is the optimization method based on the mechanics of natural selection and natural genetics. The proposed method tunes the parameters of the fuzzy logic stabilizer in order to minimize the consuming time during the design process. In this paper, the proposed method tunes the shape of membership function of the fuzzy variables. The proposed system is applied to the one-machine infinite-bus model of a power system. Through the case study, the efficiency of the fuzzy stabilizing controller tuned by genetic algorithm is verified.

• Journal of Institute of Control, Robotics and Systems
• /
• v.8 no.7
• /
• pp.547-555
• /
• 2002

This paper proposes a stabilizing controller for the multirate sampled-data systems, which have a periodic output measurement scheme, in case of the open-loop unstable plant. A sufficient condition for maintaining observability in the multirate sampled-data systems is derived and a design strategy for filtered disturbance rejection is proposed. We also propose a design method for the plant output estimator. It is shown that the proposed pre-stabilizing controllers can stabilize the plant through the simulations. The proposed controller has IMC structure, and can be decomposed into the pre-stabilizing controller, the plant output estimator, the filtered disturbance estimator and the inverse of the fast pre-stabilized plant model. We assume that the plant is open-loop unstable and the disturbance consists of a sum of finite number of sinusoids with different frequencies. Some examples are presented for illustrations.

• 제어로봇시스템학회:학술대회논문집
• /
• 1987.10b
• /
• pp.185-189
• /
• 1987

The controller with robustness described in this paper is designed for processes with variable time-delays. This adaptive mechanism includes servo and stabilizing compensators. In the proposed multivariable controller. knowledge of the system time-delay is not required.

• Journal of Ocean Engineering and Technology
• /
• v.23 no.2
• /
• pp.1-7
• /
• 2009

This paper presents a sliding mode controller based on Ackermann's formula and applies it to stabilizing a two-wheeled mobile inverted pendulum in equilibrium. The mobile inverted pendulum is a system with an inverted pendulum on a mobile cart. The dynamic modeling of the mobile inverted pendulum was established under the assumptions of a cart with no slip and a pendulum with only planar motion. The proposed sliding mode controller was based upon a class of nonlinear systems whose nonlinear part of the modeling can be linearly parameterized. The sliding surface was obtained in an explicit form using Ackermann's formula, and then a control law was designed from reachability conditions and made the sliding surface attractive to the equilibrium state of the mobile inverted pendulum. The proposed controller was implemented in a Microchip PIC16F877 micro-controller. The developed overall control system is described. The simulation and experimental results are presented to show the effectiveness of the modeling and controller.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.25 no.9
• /
• pp.1201-1208
• /
• 2001

Variable temperature anemometer(VTA) has greater sensitivity than a conventional constant temperature anemometer(CTA). In order to design a reliable VTA system, however, an elaborate photoconductive cell stabilizing circuit which plays a key role in setting wire-overheat ratio should be firstly developed. In this study, a stabilizing circuit which adopts proportional-integral analog controller was proposed and thoroughly tested for its accuracy and reproducibility. In contrast to the available circuit suggested by Takagi, the present circuit has characteristic that the resistance of a photoconductive cell increases with the increase of input voltage, which makes the current circuit very suitable for the design of VTA. Finally, VTA adopting stabilizing circuit was made and the enhanced sensitivity of the VTA was validated experimentally by comparing the calibration curves of VTA and CTA.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.2
• /
• pp.385-392
• /
• 1993

This paper presents a new stable composite control law for the flexible joint robot manipulators, which incorporate an additional stabilizing control law with the sliding property. The singularly perturbated models in this paper include inertia moments which are functions or the deformations of actuators as well as link positions. The values of renewedly defined fast controller variables are computer from the corrected reduced-order model without additional computational loads. Proposed schemes are compared with the conventional one. The simulations for 2 DOF flexible joint manipulator show that the proposed schemes are more stable than the conventional scheme, and especially effective for the manipulator with high joint-flexibilities.

• Journal of KSNVE
• /
• v.8 no.1
• /
• pp.195-203
• /
• 1998

The magnetic levitation system is utilized in the magnetic bearing of high-speed rotor because of little friction, no lubrication, no noise and so on. The magnetic levitation system need the feedback controller for the stabilization of system, and gap sensors are generally used to measure the gap. The use of sensor easily goes into troublesome caused by sensor failure discord between the measurement point and the control point etc. This paper presents the design of robust stabilizing contoller by $H_{\infty}$ control theory using the sensorless method proposed by authors in the magnetic levitation system. And we investigated both the validity of the designed controller and the usefulness of the sensorless magnetic levitation system through results of actual experiment.

• Journal of Institute of Control, Robotics and Systems
• /
• v.9 no.12
• /
• pp.977-983
• /
• 2003

An output feedback stabilizing controller far non-minimum phase nonlinear systems is presented. We first perform the standard input-output linearization of the system and then transform the zero dynamics into a special normal form in which the antistable part is not affected by the stable part and the antistable part is given in approximately linear form. Under the assumption that the nonlinear system satisfies the observability rank condition, we can design an observer f3r the extended system that is made of the augmentation of a chain of integrators. The proposed output feedback stabilizing controller can then be designed by combining the observer and the state feedback controller.

• Journal of Institute of Control, Robotics and Systems
• /
• v.8 no.11
• /
• pp.916-921
• /
• 2002

We presents a new method of constructing an equivalent T-S fuzzy model by using the sum of products of linearly independent scalar functions from nonlinear dynamics. This method exactly expresses nonlinear systems and automatically determines the number of rules. We design a stabilizing controller f3r ul inverted pendulum system by using the concep of parallel distributed compensation (PDC) and linear matrix inequalities (LMIs) based on the proposed T-S fuzzy modeling method. We show effectiveness of a systematically designed fuzzy controller based on the proposed T-S fuzzy modeling method through the simulation and experiment of an inverted pendulum system.