Joon-Young Kim

Controller design for an autonomous underwater vehicle using nonlinear observers

The depth and heading control of an autonomous underwater vehicle (AUV) are considered to follow the predetermined depth and heading angle. The proposed control algorithm was based on a sliding mode control, using estimated hydrodynamic coefficients. The hydrodynamic coefficients were estimated employing conventional nonlinear observer techniques, such as sliding mode observer and extended Kalman filter. Using the estimated coefficients, a sliding mode controller was constructed for a combined diving and steering maneuver. The simulated results of the proposed control system were compared with those of a control system that employed true coefficients. This paper demonstrated the proposed control system, and discusses the mechanisms that make the system stable and accurately follow the desired depth and heading angle in the presence of parameter uncertainty.

Study on underwater wireless communication system using LED

In this paper, a new variable-focus LED light device is developed for underwater communication. Usually used as an underwater lighting fixture, the LED light device in this study is utilized as an underwater communication device (UCD) by controlling the distance between light source and lens when communication is needed. A transmission and a receiving part of LED light for communication using photoelectric sensor and Fresnel lens are also developed. The communication system was tested in fresh water and sea water to verify its communication performance; results of which are presented in this study.

Design of Fuzzy PD Depth Controller for an AUV

This paper presents a design of fuzzy PD depth controller for the autonomous underwater vehicle entitled KAUV-1. The vehicle is shaped like a torpedo with light weight and small size and used for marine exploration and monitoring. The KAUV-1 has a unique ducted propeller located at aft end with yawing actuation acting as a rudder. For depth control, the KAUV-1 uses a mass shifter mechanism to change its center of gravity, consequently, can control pitch angle and depth of the vehicle. A design of classical PD depth controller for the KAUV-1 was presented and analyzed. However, it has inherent drawback of gains, which is their values are fixed. Meanwhile, in different operation modes, vehicle dynamics might have different effects on the behavior of the vehicle. In this reason, control gains need to be appropriately changed according to vehicle operating states for better performance. This paper presents a self-tuning gain for depth controller using the fuzzy logic method which is based on the classical PD controller. The self-tuning gains are outputs of fuzzy logic blocks. The performance of the self-tuning gain controller is simulated using Matlab/Simulink and is compared with that of the classical PD controller.

Development of Rotational Motion Estimation System for a UUV/USV based on TMS320F28335 microprocessor

For the accurate estimation of the position and orientation of a UUV (unmanned underwater vehicle), a low-cost AHRS (attitude heading reference system) was developed using a low-cost IMU (inertial measurement unit) sensor which provides information on the 3D acceleration, 3D turning rate and 3D earth-magnetic field data in the object coordinate system. The main hardware system is composed of an IMU sensor (ADIS16405) and TMS320F28335, which is coded with an extended kalman filter algorithm with a 50-Hz sampling frequency. Through an experimental gimbal device, good estimation performance for the pitch, roll, and yaw angles of the developed AHRS was verified by comparing to those of a commercial AHRS called the MTi system. The experimental results are here presented and analyzed.

On-line minimum-time trajectory planning for industrial manipulators

In this paper, a method for the on-line minimum-time trajectory planning for industrial manipulators was proposed assuming that the path is specified and the maximum allowable actuator torques are limited. The typical on-line trajectory planning strategy in industry is to find polynomials that follow the given path while satisfying the kinematic constraints. Although this traditional method is widely used in industry, it has a major shortcoming, which is, by using the constant kinematic constraints that neglect the manipulator dynamics, it lowers the global efficiency of the manipulators dynamic capability. We demonstrated that this existing shortcoming of the traditional method could be overcome considerably by taking the manipulator dynamics into consideration. In the proposed method, the dynamic calculation was performed only at certain points on the given path, which is effectively utilized to determine the kinematic constraints. The experimental results implied that this method could improve the traditional trajectory planning method for industrial manipulators.

Design and Control of 6 D.O.F(Degrees of Freedom) Hovering AUV

In this paper, a study of a new hovering six dof underwater robot with redundant horizontal thrusters, titled HAUV (hovering AUV), is presented. The results of study on the structure design, deployment of thrusters, and development of the developed control system of the AUV was presented. For the HAUV structure, a structure design and an analysis of the thrusting system was performed. For navigation, a sensor fusion board which can proceed various sensor signals to identify correct positions and speeds was developed and a total control system including EKF (Extended Kalman Filter) was designed. Rolling, pitching and depth control tests of the HAUV have been performed, and relatively small angle error and depth tracking error results were shown.

Development of Hovering AUV Test-bed for Underwater Explorations and Operations

This paper describes the design and control of a hovering AUV test-bed and analyzes the dynamic performance of the vehicle using simulation programs. The main purpose of this vehicle is to carry out fundamental tests of its station keeping, attitude control, and desired position tracking. Its configuration is similar to the general appearance of an ROV for underwater operations, and its dimensions are 0.75 m × 0.5 m × 0.5 m. It has four 450-W thrusters for longitudinal/lateral/vertical propulsion and is equipped with a pressure sensor for measuring the water depth and a magnetic compass for measuring its heading angle. The navigation of the vehicle is controlled by an onboard Pentium III-class computer, which runs with the help of the Windows XP operating system. This provides an appropriate environment for developing the various algorithms needed for developing and advancing a hovering AUV.

Development and Experiment of a Hovering AUV Tested-bed for Underwater Exploration

This paper describes the design and development of a hovering AUV constructed at Cheju National University and analyses the dynamic performance of the vehicle using simulation program. The main purpose of this AUV is to carry out fundamental tests on its station keeping, attitude control, and desired position tracking. Its configuration is similar to the general ROV appearance for underwater works and its dimensions are 0.75 m times 0.5 m times 0.5 m. It has 4 thrusters of 450 watts for longitudinal/lateral/vertical propulsion and is equipped with a pressure sensor for measuring water depth and a magnetic compass for measuring heading angle. The navigation of the vehicle is controlled by an on-board Pentium III-class computer, which runs with the help of the Windows XP operating system. These give us an ideal environment for developing various algorithms needed for developing and advancing hovering AUV.

A study on an up-milling rock crushing tool operation of an underwater tracked vehicle

In this article, we develop the analysis of a new underwater tracked vehicle with rock crushing tool, working under the water. To design the capacity of the underwater tracked vehicle actuator and the rock crushing tool actuator, we analyze the interaction forces and torque between the rock and the rock crushing tool. Since experiments on the underwater tracked vehicle with a rock crushing tool are very difficult, costly, time-consuming, we first perform a mathematical modeling of the underwater tracked vehicle with the rock crushing tool. We analyze the mechanics of the underwater tracked vehicle system that is affected by the forces and moments of the underwater rock crushing, where the force and torque on the rock crushing tool are based on the analysis of the mechanics of an individual cutter tool. We derive a mathematical expression for the forces and moments of the combined system on the underwater tracked vehicle and the rock crushing tool for rock crushing. For this, we study the parameters that affect the mechanics of the underwater tracked vehicle system with the rock crushing tool. To apply the rock crushing tool to underwater rock excavation, we also study the hydrostatic effects to the combined underwater tracked vehicle system with the rock crushing tool. To design the capacity of the actuator of the developing underwater tracked vehicle and the rock crushing tool, we analyze the required tractive or down thrust forces, and the torque to the rotor carriage caused by the cutting system. In addition, we analyze the energy and the power for the rock crushing tool actuator related to the tool characteristics. To support the validity of the analyses, we use the derived equations to perform a number of numerical simulations.

Redundancy analysis and motion control using ZMP equation for underwater vehicle-manipulator systems

The underwater vehicle-manipulator system (UVMS) is basically a redundant system. Hence, this redundant system can have various combinations of joint velocities that do not affect the given velocity profile of an end-effector and this may induce a self-motion of a vehicle. In the current paper, the performance index based on the concept of Zero Moment Point(ZMP) is proposed to enhance the stability of the redundant UVMS while the specified task is performed by using the underwater manipulator. In order to generate the joint angle trajectories of the manipulator, a redundancy resolution is performed to minimize the distance between the position of ZMP and the mass center of the underwater vehicle, which means the propulsion energy for controlling the vehicles motion can be reduced. To control the motion of the system with uncertainties, a controller based on the sliding mode theory has been designed. Finally, an example simulation of a simple UVMS is conducted to show the performance of the designed robust controller.