Jae Weon Choi

Localization of a mobile robot using the image of a moving object

This paper proposes a new approach for determining the location of a mobile robot using the image of a moving object. This scheme combines data from the observed position, using dead-reckoning sensors, and the estimated position, using images of moving objects captured by a fixed camera to determine the location of a mobile robot. Using the a priori known path of a moving object and a perspective camera model, the geometric constraint equations that represent the relation between image frame coordinates for a moving object and the estimated robots position are derived. Since the equations are based on estimated position, measurement error may exist. However, the proposed method utilizes the error between the observed and estimated image coordinates to localize the mobile robot, and the Kalman filtering scheme is used for the estimation of the mobile robot location. The proposed approach is applied for a moving object on the wall to show the reduction of uncertainty in the determining of mobile robot location.

Localization of a mobile robot using images of a moving target

In this paper, the localization of a mobile robot using images of a moving target is introduced. Typical objects are stored in the database for the localization of the mobile robot. With a fixed camera, a perspective camera model and a given object database, an image frame can provide the pose (distance and orientation) of the object with respect to the camera. Utilizing the consecutive image frames and motion estimation technology, the relative pose of the object with respect to the camera can be obtained accurately; and during the process, calibration of camera with respect to the world frame, i.e. localization of a mobile robot, is gradually performed. This localization scheme is demonstrated by the experiments.

Distributed single target tracking in underwater wireless sensor networks

The growing interests in underwater wireless sensor networks(UWSNs) for a wide variety of purposes from Tsunami monitoring to commercial oilfield exploration projects have been encouraging. This paper deals with the problem of accurately tracking a single target moving through UWSNs employing acoustic sensors. This paper addresses the issues of estimating the target position, improving energy efficiency by applying a Kalman filter in a distributed architecture. Each underwater wireless sensor nodes composing the UWSNs is battery-powered, so the energy conservation problem is a critical issue. This paper provides an algorithm which increases energy efficiency of each sensor through a wake-up/sleep(WuS) and a valid measurement selecting(VMS) scheme. Simulation results illustrate the performance of the tracking filter according to the sensor node displacement and sensor detecting area.

Decoupling and tracking control using eigenstructure assignment for linear time-varying systems

This work is concerned with the assignment of a desired PD-eigenstructure for linear time-varying systems. Despite its well-known limitations, gain scheduling control appeared to be a focus of the research efforts. Scheduling of frozen-time, frozen-state controllers for fast time-varying dynamics is known to be mathematically fallacious, and practically hazardous. Therefore, recent research efforts are being directed towards applying time-varying controllers. In this paper, (a) we introduce a differential algebraic eigenvalue theory for linear time-varying systems, and then (b) a novel decoupling and tracking control scheme is proposed by using the PD-eigenstructure assignment scheme via a differential Sylvester equation and a Command Generator Tracker for linear time-varying systems. The PD-eigenstructure assignment is utilized as a regulator. A feedforward gain for tracking control is computed by using the command generator tracker. The whole design procedure of the proposed PD-eigenstructure assignment scheme is systematic in nature. The scheme could be used to determine stability of linear time-varying systems easily as well as to provide a new horizon of designing controllers for the linear time-varying systems. The presented method is illustrated by numerical examples.

ToA based sensor localization in underwater wireless sensor networks

Currently several kinds of sensor localization methods have been developed for terrestrial wireless sensor networks. In this paper, in order to extend the field to underwater environments, we study sensor localization technique for underwater wireless sensor networks(UWSNs). In underwater environments, radio frequency(RF) signal is not suitable for underwater usage because of extremely limited propagation. Because of that reason UWSNs should be constituted with acoustic modems. So we need a new localization algorithm to determine each sensors position. First of all we study the localization techniques for terrestrial environments where we investigate possible methods to underwater environment. And then we present the appropriate algorithm in the underwater usage. Finally we, evaluate the underwater based localization algorithm using computer based different conditions among communication range of sensor node, the nodes number and position of reference node.

A relative navigation system for vehicle platooning

The paper is concerned with a relative navigation system. The previous reported relative navigation system designed for formation flight is applied to vehicle platooning. This system is based on both GPS (Global Positioning System) and millimeter-wave radar. This approach includes a federated Kalman filter. The longitudinal controller based on estimates controls a vehicle in a platoon to maintain the desired spacing. Vehicle platooning problem on the highway are presented to illustrate the proposed relative navigation system.

Left eigenstructure assignment via Sylvester equation

An effective and disturbance suppressible controller can be designed by assigning a left eigenstructure (eigenvalues/left eigenvectors) of a system. In this note, a novel left eigenstructure assignment scheme via Sylvester equation is proposed. The biorthogonality property between the right and left modal matrices of a system is utilized to develop the scheme.

Attitude controller design for a launch vehicle with fuel-slosh

Todays space vehicle structures are composed of large quantities of liquid fuel. Fuel-slosh occurs when fuel in a partially filled tank sloshes around inside the tank in response to vehicle acceleration. Fuel-slosh can be a severe problem in space vehicle stability and control if the fuel modes of motion couple significantly with the space vehicles normal modes of motion. We propose a determination method for sloshing parameters. The proposed method is represented in a geometric sense. Also, we design an attitude controller for a launch vehicle with fuel-slosh. A PD controller and a slosh filter are designed for the purpose. The performance of the attitude controller is evaluated via computer simulations.

Remote-controlled platoon merging via coder-estimator sequence algorithm for a communication network

In this paper, a platoon-merging control system is considered as a remotely located system with a state represented by a stochastic process. In this system, it is common to encounter situations where a single decision maker controls a large number of subsystems, and observation and control signals are sent over a communication channel with finite capacity and significant transmission delays. Unlike a classical estimation problem where the observation is a continuous process corrupted by additive noise, there is a constraint that the observation must be coded and transmitted over a digital communication channel with finite capacity. A recursive coder-estimator sequence is a state estimation scheme based on observations transmitted with finite communication capacity constraint. In this paper, we introduce a stochastic model for the lead vehicle in a platoon of vehicles in a lane considering the angle between the road surface and a horizontal plane as a stochastic process. In order to merge two platoons, the lead vehicle of the following platoon is controlled by a remote control station. Using the coder-estimator sequence, the remote control station designs the feedback controller. The simulation results show that the inter-vehicle distance and the deviation from the desired inter-vehicle distance are well regulated.

Continuous-time deadbeat fault detection and isolation filter design

A deadbeat (finite-time settling) fault detection and isolation (FDI) filter for a continuous-time invariant system is proposed in order to detect and isolate corrupted faults in a pre-defined finite time by introducing intentional delays in residuals. Conventional FDI algorithms have relied on asymptotically converging residuals to detect and isolate faults; while the proposed deadbeat FDI filter relies on residuals, which converge in a pre-determined finite-time. It is shown that both the effect of the initial state estimation error and fault responses converge in the pre-defined finite-time.