Jongbae Lee

Adaptive Model Reference Control Based on Takagi-Sugeno Fuzzy Models With Applications to Flexible Joint Manipulators

The control scheme using fuzzy modeling and Parallel Distributed Compensation (PDC) concept is proposed to provide asymptotic tracking of a reference signal for the flexible joint manipulators with uncertain parameters. From Lyapunov stability analysis and simulation results, the developed control law and adaptive law guarantee the boundedness of all signals in the closed-loop multi-input/multi-output system. In addition, the plant state tracks the state of the reference model asymptotically with time for any bounded reference input signal.

Characterization of ZnO/DLC/Si SAW devices using FCVA-produced DLC films

Surface acoustic wave (SAW) filters were fabricated using a multilayer structure of ZnO/diamond-like carbon (DLC)/Si and frequency response characteristics were analyzed. DLC films were deposited with varying preparation conditions (substrate bias, deposition time, and N/sub 2/ doping flow rate). The sp/sup 3/ fraction, thickness, surface roughness, and resistivity of DLC films were measured as a function of deposition conditions. The center frequency of SAW devices with DLC-buffer was measured to be about 575 MHz, which was much higher than that (340 MHz) of ZnO/Si(100) SAW devices. The variation of center frequencies of DLC-buffer SAW devices showed almost the same trend as that of sp/sup 3/ fractions of DLC films. By decreasing the thickness of DLC buffer layers, higher electro-mechanical coupling coefficient (K/sub eff//sup 2/), lower insertion loss (IL), and larger side-lobe rejection (SLR) levels were obtained.

Development of ethernet based tele-operation systems using haptic devices

In this paper, we investigate the issues for the design and implementation of tele-operated force-feedback system via Ethernet. Here, the 2-DOF haptic device and the X-Y stage are employed as a master controller and a slave system, respectively. In this master-slave system, the force feedback algorithm, the modeling of virtual environments and the control method of X-Y stage with linear motors are proposed. In our research, the Ethernet network is used for data communication between the master and slave controllers. We construct virtual environment of the real wall from the force-feedback in controlling the X-Y stage and getting the force applied by the 2-DOF haptic device.

Nonlinear Observer Based Flux Estimation of Induction Motors

This paper, in order to estimate the flux of induction motors, presents an observer design methodology for MIMO nonlinear systems. The proposed observer improves the transient performance of the high gain observer and guarantees the global exponential convergence to zero of the flux estimation error of induction motors

Digital stabilization of fuzzy systems with network-delay

This paper presents the design methodology of digital fuzzy controller (DFC) for the systems with time-delay. We propose the fuzzy feedback controller whose output is delayed with unit sampling period and prediction. The analysis and the design problem considering time-delay become easy because the proposed controller is synchronized with the sampling time. The stabilization problem of the digital fuzzy system with time-delay is solved by linear matrix inequality (LMI) theory. Convex optimization techniques are utilized to solve the stable feedback gains and a common Lyapunov function for the designed fuzzy control system. To show the effectiveness of the proposed control scheme, the network control example is presented.

Design and Implementation of Force-feedback System via Ethernet

In this paper, we investigate the issues for the design and implementation of tele-operated force-feedback system via Ethernet. Here, the 2-DOF haptic device and the x-y stage are employed as master controller and slave system respectively. In this master-slave system, the force feedback algorithm, the modeling of virtual environments and the control method of x-y stage with linear motors are proposed. In this paper, Ethernet network is used for data communication between master and slave. We construct virtual environment of the real wall from the force-feedback in controlling the x-y stage and getting the force applied by the 2-DOF haptic device.

Design and Implementation of Tele-operation system based on the Haptic Interface

In this paper, we investigate the issues on the design and implementation of tele-operation system based on the haptic interface. The 3-DOF haptic device and the x-y-z stage are employed as master controller and slave system respectively. In this master-slave system, the force feedback algorithm, the modeling of virtual environments and the control method of x-y-z stage are presented. In this paper, Internet network is used for data communication between master and slave. We construct virtual environment of the real convex surface from the force-feedback in controlling the X-Y-Z stage and getting the force applied by the 3-DOF haptic device