Bong-Hwan Jeon

Discrete-time quasi-sliding mode control of an autonomous underwater vehicle

This paper presents a discrete-time quasi-sliding mode controller for an autonomous underwater vehicle (AUV) in the presence of parameter uncertainties and a long sampling interval. The AUV, named VORAM, is used as a model for the verification of the proposed control algorithm. Simulations of depth control and contouring control are performed for a numerical model of the AUV with full nonlinear equations of motion to verify the effectiveness of the proposed control schemes when the vehicle has a long sampling interval. By using the discrete-time quasi-sliding mode control law, experiments on depth control of the AUV are performed in a towing tank. The controller makes the system stable in the presence of system uncertainties and even external disturbances without any observer nor any predictor producing high rate estimates of vehicle states. As the sampling interval becomes large, the effectiveness of the proposed control law is more prominent when compared with the conventional sliding mode controller.

An integrated navigation system for autonomous underwater vehicles with two range sonars, inertial sensors and Doppler velocity log

This work presents an integrated navigation system for autonomous underwater vehicles with inertial and acoustic sensors. The integrated navigation system is based on a strap-down inertial measurement unit (IMU), where auxiliary navigation sensors are two range sonars, a Doppler velocity log (DVL), a magnetic compass and a depth sensor. The main idea of the paper is to improve the performance of the IMU-DVL navigation system by introducing additional range information. The range sonars can measure the distance and the incident angle from a reference transponder on an underwater station. The range sonars are modeled to improve the navigation algorithm, which could provide valuable information for the IMU-DVL navigation to reduce estimation error, especially when the DVL cannot detect the bottom reflection. Simulation was conducted with the 6-d.o.f. nonlinear numerical model of an AUV in lawn-mowing survey mode at tidal flow, where the bottom reflected DVL information is unavailable. Simulations illustrate the effectiveness of the integrated navigation system assisted by the additional range measurements.

Visual servoing for underwater docking of an autonomous underwater vehicle with one camera

Docking systems are required to increase the capability of autonomous underwater vehicles (AUVs) to recharge the batteries and to transmit data in real time in underwater. This paper presents a docking system for an AUV to dock into an underwater station with one camera installed at the nose center of the AUV. To make a visual servo controller, this paper presents an optimal control algorithm based on a state equation composed of the AUV dynamics and the optical flow equation. The control inputs of the AUV are generated with the projected target position on the CCD plane of the camera and with the AUVs motion. This paper introduces a test bed AUV for underwater docking developed in Korea Research Institute of Ships and Ocean Engineering (KRISO), KORDI of Korea. The AUV is propelled with one thruster and controlled with two horizontal planes and two vertical planes. Experiments will be performed in Ocean Engineering Basin of KRISO to demonstrate the effectiveness of the modeling and control law of the visual servoing AUV. The AUV identifies target position with processing the captured image of the lights mounted around the entrance of the dock. This paper also presents a strategy to identifier the target with lights arrays.

Multivariable optimal control of an autonomous underwater vehicle for steering and diving control in variable speed

This paper describes a multivariable optimal control for a Semi-Autonomous Underwater Vehicle (SAUV) developed in Korea Ocean Research and Development Institute (KORDI). The SAUV is a test-bed for evaluation of navigation algorithms and manipulator technologies for a mine disposal vehicle (MDV) in military use and for a light working underwater vehicle in scientific application. The vehicle was designed to control its cruising speed, heading and depth with 4 horizontal thrusters installed at the rear of the hull. The decoupled control methods are limited to be applied to the SAUV because the thrust forces are highly coupled with the surging, yawing, and pitching motion of the vehicle. The multivariable Linear Quadratic (LQ) control method is chosen to control steering and diving in variable speed motion automatically. This paper presents the results of tank-test with the controller and compares them with the simulation results to validate the performance.

A docking and control system for an autonomous underwater vehicle

Autonomous underwater vehicles are unmanned underwater vessels to investigate sea environments, oceanography and deep-sea resources autonomously. Docking systems are required to increase the capability of the AUVs to recharge the batteries and to transmit data in real time underwater. This paper presents a docking system for an AUV to dock into underwater station with a camera. To make a visual servo control system, this paper derives an optical flow model of a camera mounted on AUV, where a CCD camera is installed at the nose center of the AUV to monitor the docking condition. This paper combines the optical flow equation of the camera with the AUVs equation of motion, derives a state equation for the visual servoing AUV. This paper also proposes a MIMO controller minimizing a cost function. The control inputs of the AUV are automatically generated with the projected target position on the CCD plane and with the AUVs motion. To demonstrate the effectiveness of the modeling and the control law of the visual servoing AUV, simulations of docking the AUV to a target station are performed with the 6-dof nonlinear equations of REMUS of WHOI and a CCD camera.

Improvement on an inertial-Doppler navigation system of underwater vehicles using a complementary range sonar

This work presents an improvement of an inertial-Doppler underwater navigation system for unmanned underwater vehicles (UUV) using a complementary range sonar. The inertial-Doppler navigation system is generally based on an inertial measurement unit (IMU) and a Doppler velocity log (DVL) accompanying a magnetic compass and a depth sensor. Although conventional navigation systems update bias errors of the inertial sensors, scale effects of the DVL, the estimated position slowly drifts as time passes. This paper proposes a measurement model with additional range sonar to improve the performance of the IMU-DVL navigation system for underwater vehicles. The proposed navigation model based on inertial navigation systems includes the scale effects, the bias errors of the DVL, and the error model of the range sonar, where the order of the system states is 21. An extended Kalman filter was adopted to propagate the error covariance, updated the measurement errors and correct the state equation when the external measurements are available. Simulation conducted with the 6-d.o.f. equations of motion of an AUV in lawn-mowing survey mode illustrates the effectiveness of the IMU-DVL navigation system assisted by the additional range measurement.

System design of an ROV with manipulators and adaptive control of it

A remotely operated vehicle (ROV) equipped with two manipulators and an underwater stereo camera is being developed in KRISO (Korea Research Institute of Ships and Ocean Engineering) for seabed working. This paper describes the preliminary design of the ROV. An underwater stereo camera has been developed to enhance the working efficiency of the ROV with the manipulator in seabed operation. This paper presents the operational principle and the structure of the underwater stereo camera. The stereo camera consists of two CCD cameras and horizontally moving base, and it is embedded in a small pressure canister for underwater application. This paper also evaluates the implementation of an adaptive controller to the tracking control of the ROV/manipulator system.

Path tracking control for underactuated AUVs based on resolved motion acceleration control

In contrast with man-operating underwater vehicles, autonomous underwater vehicles (AUVs) should find a proper trajectory, control to follow the trajectory, avoid static or moving obstacles, and home safely to their mother ship or launching device by themselves. As a consequence, lots of newly introduced problems have to be solved compared to man-operating underwater vehicle case. In these works we focus on path following control problems. Most AUVs are usually designed to be under-actuated or non-holonomic constrained system. In this paper, we propose a method of resolved motion and acceleration control (RMAC) to solve the path following control problems of an underactuated AUV. Simulations were done to verify the effectiveness of the proposed control method for underactuated AUV and results are discussed.

Preliminary study on the inertial-Doppler localization of a deep-sea launcher hanging on a cable

This paper presents a localization method of a deep-sea launcher with a hybrid underwater navigation system. The under water navigation system mainly composed of an inertial measurement unit (IMU) and a Doppler velocity log (DVL). The implementation of DVL can improve the navigational performance of the IMU when an underwater vehicle works near sea bottom. A dynamic error model of a DVL-aided inertial navigation system is designed to implement an indirect feedback Kalman filter, and a measurement model is also designed. This paper demonstrates the enhanced performance of the DVL-aided hybrid navigation by conducting rotating arm test in ocean engineering basin at KRISO. The IMU and the DVL are embedded in a small fish attached at the rotating arm. Additional depth sensor and a magnetic compass are introduced in the measurement model. In addition, this paper also conducts a dead-reckoning navigation using the DVL and the magnetic compass. The dead-reckoning navigation system also shows better performance than the IMU-only navigation system.

System design and quasi-sliding mode control of an AUV for ocean research and monitoring

The VORAM (vehicle for ocean research and monitoring) autonomous underwater vehicle (AUV), is developed in KRISO (Korea Research Institute of Ships and Ocean engineering) for the observation and investigation of seabed. This paper describes the design and configuration of the AUV system and presents a discrete-time quasi-sliding mode controller with parameter uncertainties and long sampling interval. The proposed controller makes the system stable in the presence of system uncertainties and even external disturbances. Depth keeping control and contouring control are performed for a numerical model of the AUV with full nonlinear equations of motion to verify the effectiveness of the proposed control schemes when the vehicle has long sampling interval. The experimental results agree with the simulations. As sampling interval becomes large the effectiveness of the proposed control law is more prominent compared with the conventional sliding mode controller.