Wook Chang

Magic wand: a hand-drawn gesture input device in 3-D space with inertial sensors

This paper presents a gesture input device, magic wand, with which a user can input gestures in 3-D space, inertial sensors embedded in it generate acceleration and angular velocity signals according to a users hand movement. A trajectory estimation algorithm is employed to convert them into a trajectory on 2-D plane. The recognition algorithm based on Bayesian networks finds the gesture model with the maximum likelihood from it. The recognition performance of the proposed system is quite promising; the writer-independent recognition rate was 99.2% on average for the database of 15 writers and 13 gesture classes.

Design of robust fuzzy-model-based controller with sliding mode control for SISO nonlinear systems

In this paper, we present the design of a new type of fuzzy controllers for controlling complex single-input-single-output systems by incorporating sliding mode control theory with fuzzy control technology. First, a fuzzy model of the given nonlinear system is constructed to represent the local dynamic behaviors of the given nonlinear system. A global controller is then constructed by combining all local state feedback controllers and a global supervisory sliding mode controller. Improved robustness and tracking performance are obtained by a seamless integration of fuzzy-model-based control and sliding mode control. In addition, stability of controlling the original underlying nonlinear systems is guaranteed owing to the robustness of the sliding mode control method to system parameter uncertainties. Two simulation examples are included to show the effectiveness and feasibility of the developed integrated controller.

Static output-feedback fuzzy controller for Chen's chaotic system with uncertainties

Static output-feedback stabilization of Chens chaotic system with uncertainties is studied from a fuzzy control approach. An uncertain Takagi-Sugeno (TS) fuzzy model for the uncertain Chens chaotic system is first constructed. Then, the uncertain TS fuzzy model is represented as a set of uncertain linear systems and a controller design algorithm is proposed. Specifically, a switching static output-feedback fuzzy-model-based controller is designed by solving some linear matrix inequalities (LMI), which are derived from the developed local representations. Simulation results have confirmed the effectiveness and feasibility of the proposed modeling and control methods.

Self-contained spatial input device for wearable computers

In this paper, we present a pen-shaped input device forwearable computers which reproduce and recognizethree-dimensional (3D) hand motions with no externalreferences. The input device is equipped with inertialsensors. The inertial sensors measure accelerations andangular velocities produced by a users handwritingmotion in 2D/3D spaces. The measurements fromgyroscopes are integrated once to produce the attitude ofthe system and are consequently used to remove theeffects of the gravity and the inclination of the system.The compensated acceleration measurements are doublyintegrated to yield the position of the system. Due to theintegration processes involved in reproducing thehandwriting trajectory, the accuracy of the positionmeasurement significantly deteriorates along with time.To reproduce handwriting trajectory of a stroke on asurface and even in the air, we propose algorithms tosegment a stroke, to compensate the integration errors,and to reconstruct 2D trajectory on the x-y plane from 3Dtrajectory in the air. Real experimental results areincluded to show the effectiveness and feasibility of theproposed algorithms. The proposed methods provide anew approach for implementing a small, user-friendlykeyboard alternative input device for wearable computers.

GA-based intelligent digital redesign of fuzzy-model-based controllers

Intelligent digital redesign involves converting a continuous-time fuzzy-model-based controller into an equivalent discrete-time counterpart for the digital control of continuous-time nonlinear systems by using the Takagi-Sugeno (TS) fuzzy models. In this paper, the authors present a new global state-matching intelligent digital redesign method for nonlinear systems by using genetic algorithms (GAs). More precisely, the intelligent digital redesign problem is converted to an equivalent optimization problem, and then GAs are adopted to find a solution. The search space, in which each problem variable is defined for GAs, are systematically obtained by the interval arithmetic operations. The proposed method results in global matching of the states of the analogously controlled system with those of the digitally controlled system while the conventional intelligent digital redesign method does not. The Chens chaotic system is used as an illustrative example to show the effectiveness and the feasibility of the developed method. The proposed method provides a new approach for the digital redesign of a class of fuzzy-model-based controllers.

Inertial sensor based recognition of 3-D character gestures with an ensemble classifiers

We present a 3-D input medium based on inertial sensors for on-line character recognition and an ensemble classification scheme for the recognition task. The system allows user to write a character in the air as a gesture, with a sensor-embedded device held in hand. The kinds of sensors used are 3-axis accelerometer and 3-axis gyroscope generating acceleration and angular velocity signals respectively. For character recognition, we used the technique of FDA (Fisher discriminant analysis). We tried different combinations of sensor signals to test the recognition performance. It is also possible to estimate a 2-D handwriting trajectory from the sensor signals. The best recognition rate of 93.23%, in case we use only raw sensor signals, was attained when all 6 sensor signals were combined. The recognition rate of 92.22% was reached if the estimated trajectory was used as input. Finally we tested the ensemble method and the generalization rate of 95.04% was attained on the ensemble recognizer consisting of 3 FDA recognizers based on acceleration-only, angular-velocity-only and handwriting trajectory respectively.

Recognition of Grip-Patterns by Using Capacitive Touch Sensors

A novel and intuitive way of accessing applications of mobile devices is presented. The key idea is to use grip-pattern, which is naturally produced when a user tries to use the mobile device, as a clue to determine an application to be launched. To this end, a capacitive touch sensor system is carefully designed and installed underneath the housing of the mobile device to capture the information of the users grip-pattern. The captured data is then recognized by a minimum distance classifier and a naive Bayes classifier. The recognition test is performed to validate the feasibility of the proposed user interface system

A novel hand gesture input device based on inertial sensing technique

In this paper, we present a novel gesture-based input device by using inertial sensing technique. The trajectories of users hand-drawn gestures in 3D space are captured and recognized by this device to fulfill user interaction task. The proposed device employs gyro-free inertial measurement unit (IMU) to track hand motions without requiring any external reference sensors or signals. Since the unbounded growing error of trajectory estimation, as a major drawback of IMU-based motion tracking technology, is carefully solved by using zero velocity compensation. Here, a deliberately-designed motion detection scheme is proposed to capture accurate hand motion period. Finally, the recognition algorithm based on Bayesian networks takes estimated trajectories and finds the corresponding gesture model with the maximum probability. Because the IMU provides outstanding capability of self-contained positioning, the proposed device is extraordinary simple and effective, comparing with the devices using other tracking technologies such as vision-based system. Experimental results also show its effectiveness and feasibility. Currently, after employing the trajectory estimation method provided in this paper, the recognition rate of 95.51% for 14 gestures has been achieved when this device is implemented as a TV remote controller. It can be used as a powerful, flexible interface for ubiquitous computing device.

Robust fuzzy-model-based controller for uncertain systems

This paper addresses the analysis and design of fuzzy control systems for a class of complex uncertain single input single output nonlinear systems. In the design procedure, we represent the nonlinear system using a Takagi-Sugeno fuzzy model and construct a global fuzzy logic controller by blending all local state feedback controllers with a sliding mode controller. Unlike the commonly used parallel distributed compensation technique, we can design a global stable fuzzy controller without finding a common Lyapunov function for all local control systems, and can obtain a good tracking performance. Furthermore, a stability analysis is carried out not for the fuzzy model but for a real nonlinear system with uncertainties. One simulation example is given to show the effectiveness and feasibility of the proposed fuzzy controller design method.

Output Feedback Fuzzy Control for Uncertain Nonlinear Systems

In this paper, a fuzzy control scheme, which employs the output feedback control approach, is suggested for the stabilization of nonlinear systems with uncertainties. The uncertain nonlinear system can be represented by uncertain Takagi-Sugeno (TS) fuzzy model structure, which is further rearranged to give a set of uncertain linear systems. A switching-type fuzzy-model-based controller, which utilizes the static output feedback control strategy, is designed based on this preliminary study. Theoretical analysis guarantees that under the control of the proposed technique, the uncertain nonlinear system is stabilizable by the switching-type static output-feedback fuzzy-model-based controller. Finally, two computer simulation examples are provided to show the effectiveness and feasibility of the developed controller design method.