Cheolkeun Ha

Control of a Quadrotor Using a Smart Self-Tuning Fuzzy PID Controller

This paper deals with the modelling, simulation-based controller design and path planning of a four rotor helicopter known as a quadrotor. All the drags, aerodynamic, coriolis and gyroscopic effect are neglected. A Newton-Euler formulation is used to derive the mathematical model. A smart self-tuning fuzzy PID controller based on an EKF algorithm is proposed for the attitude and position control of the quadrotor. The PID gains are tuned using a self-tuning fuzzy algorithm. The self-tuning of fuzzy parameters is achieved based on an EKF algorithm. A smart selection technique and exclusive tuning of active fuzzy parameters is proposed to reduce the computational time. Dijkstras algorithm is used for path planning in a closed and known environment filled with obstacles and/or boundaries. The Dijkstra algorithm helps avoid obstacle and find the shortest route from a given initial position to the final position.

Modeling and control of quadrotor MAV using vision-based measurement

In this paper we review the mathematics model of quadrotor using Lagranges equation. We propose a vision-based measurement to stabilize this model. A dual camera method is used for estimating the pose of the quadrotor; positions and attitudes of the quadrotor MAV. One of these cameras is located on-board the quadrotor MAV, and the orther is located on the ground. The control system is developed in Matlab/Simulink. In this paper, we consider a linear controller for our purpose. Linear Quadratic tracking controller with integral action, and Optimal Linear Quadratic Gaussian (LQG) control with integral action are designed for stabilization of the attitude of the quadrotor MAV. Moreover, some measurement noises will be considered in the controller design, too. Finally, this paper will demonstrate how well this control works for a certain flight mission: quadrotor MAV on the ground, and then starting hover, sideway move and keeping the position with a pointing to a certain object fixed in space.

Multiple Model Adaptive Control Scheme for Nonlinear Reconfigurable System

In this study, adaptive control methodology using multiple models is proposed to design a reconfigurable controller for nonlinear systems. An adaptive model and fixed parameter models are used for mode switching, and a re-initialized adaptive model is considered. The conventional mode switching method based on multiple model adaptive control does not guarantee the stability of the closed-loop system. To improve the adaptiveness of a nonlinear system while maintaining the stability, mode switching scheme is modified and a new decision logic is considered. In the mode switching control scheme, forgetting factor and adaptive time concepts are introduced based on the selected model for reconfiguration. An error threshold value is used in the decision logic. Numerical simulation results for a nonlinear discrete-time system verify the effectiveness of the proposed method

Fuzzy Vector Field Orientation Feedback Control-Based Slip Compensation for Trajectory Tracking Control of a Four Track Wheel Skid-Steered Mobile Robot

Skid-steered mobile robots have been widely used in exploring unknown environments and in military applications. In this paper, the tuning fuzzy Vector Field Orientation (FVFO) feedback control method is proposed for a four track wheel skid-steered mobile robot (4-TW SSMR) using flexible fuzzy logic control (FLC). The extended Kalman filter is utilized to estimate the positions, velocities and orientation angles, which are used for feedback control signals in the FVFO method, based on the AHRS kinematic motion model and velocity constraints. In addition, in light of the wheel slip and the braking ability of the robot, we propose a new method for estimating online wheel slip parameters based on a discrete Kalman filter to compensate for the velocity constraints. As demonstrated by our experimental results, the advantages of the combination of the proposed FVFO and wheel slip estimation methods overcome the limitations of the others in the trajectory tracking control problem for a 4-TW SSMR.

Slippage Estimation Using Sensor Fusion

In this paper, a non-contact slippage estimation approach using sensor fusion is proposed. The sensor consists of a charge-coupled device (CCD) camera and structured light emitter. The slip margin is obtained by estimating very small displacement of the grasped object in consecutive frames sequence captured by CCD camera. In experiments, we apply our approach on a slip-margin feedback control gripper system. The three degree of freedom (DOF) gripper consisting of a CCD camera, structured light and force sensor grasps a target object. The incipient slippage occurs on the contact surface between grip fingers and grasping object when the object is pressed and slid, is estimated by proposed approach. Then, the grip force is immediately controlled by a direct feedback of the estimated slip margin. Consequently, the force is adaptively maintained in order to prevent the object from damage. The proposed approach validity is confirmed by results of experiments.

A General Contact Force Analysis of an Under-actuated Finger in Robot Hand Grasping

This paper develops a mathematical analysis of contact forces for the under-actuated finger in a general under-actuated robotic hand during grasping. The concept of under-actuation in robotic grasping with fewer actuators than degrees of freedom (DOF), through the use of springs and mechanical limits, allows the hand to adjust itself to an irregularly shaped object without complex control strategies and sensors. Here the main concern is the contact forces, which are important elements in grasping tasks, based on the proposed mathematical analysis of their distributions of the n-DOF under-actuated finger. The simulation results, along with the 3-DOF finger from the ADAMS model, show the effectiveness of the mathematical analysis method, while comparing them with the measured results. The system can find magnitudes of the contact forces at the contact positions between the phalanges and the object.

Trajectory Estimation of a Tracked Mobile Robot Using the Sigma-Point Kalman Filter with an IMU and Optical Encoder

Trajectory estimations of tracked mobile robots have been widely used to explore unknown environments and in military applications. In this paper, we estimate the precise trajectory of a tracked skid-steered mobile robot that contains an inertial measurement unit (IMU) and an optical encoder. For a systematic estimation, we implement a sigma-point Kalman filter (SPKF), which produces more accurate trajectory information, is easier to calculate, and requires no analytic derivations or Jacobians. The proposed SPKF compensates for the limitations of the IMU and encoder in trajectory estimation problems, as observed from our experimental results.

Development of Reliability Block Diagram Analysis Tool for H/W Redundancy Structure based on Unit Module

A flight control system for high reliability consists of complicated redundant structures. This redundancy can improve fault tolerant characteristics of system. So, a system manager is able to choose a suitable structure using analyzed quantitative data of various redundant structures. In this paper, we analyzed redundant characteristics and reliability. We defined necessary mathematical model for analysis tool. Then we compose a reliability block diagram analysis tool applying such defined analysis model using Simulink blocks. Finally we verified the analysis tool using a commercial tool.

NONLINEAR RECONFIGURABLE FLIGHT CONTROL SYSTEM USING MULTIPLE MODEL ADAPTIVE CONTROL

Abstract In this study, adaptive control methodology using multiple models is proposed to design a reconfigurable controller for nonlinear systems. An adaptive model and fixed parameter models are used for mode switching, and a re-initialized adaptive model is considered. The conventional mode switching method based on multiple model adaptive control does not guarantee the stability of the closed-loop system. To improve the adaptiveness of a nonlinear system while maintaining the stability, mode switching scheme is modified and a new decision logic is considered. In the mode switching control scheme, forgetting factor and adaptive time concepts are introduced based on the selected model for reconfiguration. An error threshold value is used in the decision logic. Numerical simulation is performed for a nonlinear discrete-time MIMO aircraft system to verify the effectiveness of the proposed method.

A Real-Time Bilateral Teleoperation Control System over Imperfect Network

Functionality and performance of modern machines are directly affected by the implementation of real-time control systems. Especially in networked teleoperation applications, force feedback control and networked control are two of the most important factors and determine the performance of the whole system. In force feedback control, generally it is necessary but difficult and expensive to attach sensors (force/torque/pressure sensors) to detect the environment information in order to drive properly the feedback force. In networked control, there always exist inevitable random time-varying delays and packet losses, which may degrade the system performance and, even worse, cause the system instability. Therefore in this chapter, a study on a real-time bilateral teleoperation control system (BTCS) over an imperfect network is discussed. First, current technologies for teleoperation as well as bilateral teleoperation control systems are briefly reviewed. Second, an advanced concept for designing a bilateral teleoperation networked control (BTNCS) system is proposed and the working principle is clearly explained. Third, an approach to develop a force-sensorless feedback control (FSFC) is proposed to simplify the sensor requirement in designing the BTNCS while the correct sense of interaction between the slave and environment can be ensured. Forth, a robust adaptive networked control (RANC) -based master controller is introduced to deal with control of the slave over the network containing both time delays and information loss. Case studies are carried out to evaluate the applicability of the suggested methodology.