Hyunuk Ha

A Control of Mobile Inverted Pendulum using Single Accelerometer

This paper proposes a single accelerometer sensor control algorithm to mobile inverted pendulum, generally called `Segway`, and evaluates the performance of this system comparing to the conventional ones. The commercialized `Prototype Segway-PT` is initially considered as a next-generation transport vehicle. However, this robot is operated by three gyroscopes and two accelerometers to control the posture and speed, and it requires the complex signal processing for fusing the two sets of data. As the result of this, the growth rate of market size of `Segway` is slow because of its high price mainly. In this paper, the mobile inverted pendulum is operated by a single accelerometer to simplify the control system to lower the price. Low pass filter is one of the good sensors to reducing the variation of an accelerometer, but it has time delay. This time delay disturbs real-time mobile inverted pendulum control. Like this, other various algorithms are used for this system, but each one has its own weak point. So this paper proposes a new filtering method, median filter and EKF. Median filter is used to image processing to reject impulse elements like salt and pepper noise. As the major performance evaluation parameter for the accelerometer, the high-frequency to low frequency ratio from FFT (Fast Fourier Transform) is used. Effectiveness of the proposed algorithms has been verified through the real experiments and the results are demonstrated.

Fault Detection on Transmission Lines Using a Microphone Array and an Infrared Thermal Imaging Camera

This paper proposes a hierarchical fault detection method for transmission lines using a microphone array to detect the location of a fault and thermal imaging and charge coupled device (CCD) cameras to verify the fault and store the image, respectively. There are partial arc discharges on faulty insulators which generate specific patterns of sound. By detecting these patterns using the microphone array, the location of the faulty insulator can be estimated. A sixth-order bandpass filter and an autocorrelation scheme were applied to remove the noise signals caused by the wind, bird chirpings, or other external influences. When a mobile robot carries the thermal CCD cameras to the possible location of the fault, the faulty insulators or power transmission wires can be detected by the thermal images. The CCD camera then captures an image of the faulty insulator for the record. This detection scheme has been proved to be effective through experimentation. As a result of this research, it will be possible to use a mobile robot with integrated sensors to detect faulty insulators instead of using a human being.

Fuzzy Finite-Time Dynamic Surface Control for Nonlinear Large-Scale Systems

In this paper, a new finite-time dynamic surface control (DSC) method is proposed to enhance the convergence rate and robustness of a DSC system on the basis of the traditional infinite-time stability viewpoint for application to nonlinear large-scale systems. By defining a novel recursive finite-time virtual error variable, a virtual controlled stabilizing functions are derived, and the finite-time control performance is ensured by means of the finite-time-based Lyapunov stability theorem. An adaptive fuzzy logic system is adopted to approximate the unknown functions. The applicability of the proposed control strategy is verified by simulation and an experiment for a mobile manipulator and an articulated manipulator.

Optimal Trajectory Planning for Cooperative Control of Dual-arm Robot

This paper proposes a cooperative control algorithm for a dual-arms robot which is carrying an object to the desired location. When the dual-arms robot is carrying an object from the start to the goal point, the optimal path in terms of safety, energy, and time needs to be selected among the numerous possible paths. In order to quantify the carrying efficiency of dual-arms, DAMM (Dual Arm Manipulability Measure) has been defined and applied for the decision of the optimal path. The DAMM is defined as the intersection of the manipulability ellipsoids of the dual-arms, while the manipulability measure indicates a relationship between the joint velocity and the Cartesian velocity for each arm. The cost function for achieving the optimal path is defined as the summation of the distance to the goal and inverse of this DAMM, which aims to generate the efficient motion to the goal. It is confirmed that the optimal path planning keeps higher manipulability through the short distance path by using computer simulation. To show the effectiveness of this cooperative control algorithm experimentally, a 5-DOF dual-arm robot with distributed controllers for synchronization control has been developed and used for the experiments.

Object Tracking of the Mobile Robot Using the Stereo Camera

This paper proposes a visual servoing algorism for the object tracking by a mobile robot with the stereo camera. The mobile robot performs an object recognition and object tracking using the SIFT and CAMSHIFT algorism for the visual servoing. The CAMSHIFT algorism has been used to obtain the three-dimensional position and orientation of the mobile robot. With the visual servoing, a stable balance control has been realized by a control system which calculates a desired angle of the center of gravity whose location depends on variations of link rotation angles of the manipulator. To demonstrate the control performance of the visual servoing, real experiments ware performed using the mobile manipulator system developed for this research.

Bad insulator detection algorithm using microphone array

The paper proposes a new error detection algorithm of bad insulator, a part of high voltage equipment. Hierarchical fault detection method for the high voltage equipment using a microphone array to detect the location of faulty insulator and the thermal image camera to verify the fault and stores the image, respectively. There are partial arc discharges on the faulty insulators, which generate specific patterns of sound and spectrum. Detecting the signal using the microphone array, the location of the faulty insulator can be estimated. The 6th band-pass filter and auto-correlation scheme was applied to remove noise signal from wind or external influence. When the mobile robot carries the thermal cameras to the possible place of the fault insulator, the faulty insulators or power transmission wires can be detected by the thermal images, which are caused by the aging or natural erosion. Finally, the CCD camera captures the image of the faulty insulator for the record. The detection scheme of a fault location using the microphone array and the thermal images has been proved to be effective through the real experiments. As a result of this research, it becomes possible to use a mobile robot with the integrated sensors to detect the fault insulators instead of a human being.

Robust non-model-based sliding mode control for robot manipulator with unknown deadzone and disturbance using preselected tracking performance

This paper presents a non-model-based finite-time sliding mode control (SMC) scheme for unknown deadzone and disturbance of the robotic manipulator. A finite-time SMC (FSMC) is designed to obtain faster error convergence than the conventional infinite-time based SMC. In addition, simpler controller structure is built by using feed-forwarding upper bound coefficients of each manipulator dynamic parameters instead of model-based control or adaptive observer to estimate unknown manipulator parameters. Finally, by adding preselected constraint control term to a FSMC to compensate unknown deadzone and disturbance and uncertainties, a robust control scheme can be designed without depending deadzone and disturbance estimations. Simulation and experimental evaluations highlight the efficacy of the proposed control scheme for an articulated robotic manipulator.

An approach for controlling the communication signal flow in three-mobile robot system based on wireless communication

With the development of cooperative robotic applications, variable kinds of communication method between robots are applied. The quality of communication has directly affect to the movement of each mobile robot in system. This paper proposes an approach to control the communication between 3 mobile robots by using wireless communication. In this paper, we focus on three main parts. In the first part, the brief introduction about multi-mobile robot system and communication will be discussed. The next part is about detail information of hardware specialization and kinematics module. Finally, the third part will describe the architecture of communication system based on Transmission Control Protocol (TCP)/ Internet Protocol (IP) algorithm for server - client, which is developed by socket programming, and also the approach to control the signal flow of the system which consisted of 3 mobile robots.