• Journal of Institute of Control, Robotics and Systems
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• v.2 no.2
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• pp.88-95
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• 1996

It is inevitable for local systems to have deviations which represent interactions and modeling errors originated from the decomposition process of a large scale system. This paper presents a decentralized control scheme for interconnected systems using local linear models and a neuro-coordinator. In the proposed method, the local system is composed of a linear model and unknown deviations caused by linearizing the subsystems around operating points or by estimating parameters of the subsystems. Because the local system has unmeasurable deviations we define a local reference model which consists of a local linear model and a neural network to estimate the deviations indirectly. The reference model is reformed into a linear model which has no deviations through a transformation of input variables and we obtain an optimum feedback control law which minimizes a local performance index. Finally, we derive a decentralized feedback control law which consists of local linear states and neural network outputs. In the decentralized control, the neuro-coordinator generates a corrective control signal to cancel the effect of deviations through backpropagation learning with the errors obtained from the differences of the local system outputs and reference model outputs. Also, the stability of local system is proved by the degree of learning of the neural network under an assumption on a neural network learning index. It is shown by computer simulations that the proposed control scheme can be applied successfully to the control of a biased two-link planar robot manipulator.

• Journal of Digital Convergence
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• v.18 no.5
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• pp.17-23
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• 2020

With the advancement of AI technology, legal status and regulation issues for AI robots, and the necessity of a robot registration system are emerging. Since the shape and activity area of AI robots will no longer be limited to hardware in one country, the definition and regulation of AI robots should be expanded to a comprehensive concept including software, and information about them should be securely managed and shared by governments around the world. From this perspective, we extend 'AI robot' to the concept of Juridical AI encompassing hardware and software, and propose a method to operate the Juridical AI registration system using a permissioned blockchain called Juridical AI Chain. Since blockchain is an internationally distributed database, operating such AI registration system based on the blockchain will be a way to effectively cope with the global problems caused by the commercialization of AI robots.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.3
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• pp.292-299
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• 1999

DC motors are widely used in many industrial fields as the actuator of the robot and the driving power motors of the electrical vehicle, Usually in the sensors of DC motors such as the encoder the tachogenerator and the potentiometer etc. are applied, But usage of these sensors results in the increased price and operating cost such that the application of the motors are limitted. To solve this problem another method to construct low cost control system is investigates. In this paper a new speed control method for DC motor is proposed. This method uses motor parameters instead of using speed or position sensors. In this way the angular velocity is estimated by the measure-ment values of the armature voltage and current instead of measuring the sensor signal. This paper presents an alorithm for estimating the angular velocity of DC motor The effectiveness of the proposed method is verified by experimental results. Also the applicability of the proposed method is presented by applying to the velocity contol of a wheeled mobile robot.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.4
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• pp.227-235
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• 1993

In this paper, the development of a high performance flexible controller is described. The hardware of the controller, based on VME-bus, consists of four M68020 single-board computers (32-bit) with M68881 numerical coprocessors, two M68040 single board donputers, I/O devices (such as A/D and D/A converters, paraller I/O, encoder counters), and bus-to-bus adaptor. This software, written in C and based on X-window environment with Unix operating system, includes : text editor, compiler, downloader, and plotter running in a host computer for developing control program ; device drivers, scheduler, and mathemetical routines for the real time control purpose ; message passing, file server, source level debugger virtural terminal, etc. The hardware and software are structured so that the controller might have both flexibility and extensibility. In papallel to the controller, a three degrees of freedom kinematically redundant robot has been developed at the same time. The development of the same time. The development of the robot was undertaken in order to provide, on the one hand, a computationally intensive plant to which to apply the controller, and on the other hand a research tool in the field of kinematically redundant manipulator, which is, as such, an important area. By using the controller, dynamic control of the redundant manipulator was successfully experimented, showing the effectiveness and flexibility of the controller.

• Journal of Drive and Control
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• v.19 no.2
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• pp.1-10
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• 2022

Field robots operate in various areas, including construction, agriculture, forestry and manufacturing. Typical tasks of field robots used in various areas include excavation, flattening, and demolition. Such tasks are often accomplished in narrow alleys or indoors. In the case of field robots, there is a limit to working in a small space. Thus, to compensate for these shortcomings, many field robots equipped with Tiltrotators have recently been observed. The advantages of Tiltrotator are improved task efficiency and reduced operating time by reducing unnecessary behavior. We need simulation models that can improve the ability of new people to work and simulate tasks in advance. Thus, in this paper, we developed a simscape-based simulation model and modeling of 6DOF systems for field robots equipped with Tiltrotator. Dynamic modeling of field robot 3D models using Simcape multibody and hydraulic systems of field robots using Simcape Hydraulics were modeled. We applied a PID controller to create a control system that operates along the input angle. Simulation results show that errors occur when comparing input and output angles, but overall, they move along input angles.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.8
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• pp.709-717
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• 2013

This paper presents the development of a specialized underwater leg with a manipulator function(convertible-to-arm leg) for the seabed walking robot named CRABSTER200(CR200). The objective functions of the convertible-to-arm leg are to walk on the seabed and to work in underwater for precise seabed exploration and underwater tasks under coastal area with strong tidal current. In order to develop the leg, important design elements including the degree of freedom, dimensions, mass, motion range, joint structure/torque/angular-speed, pressure-resistance, watertight capability and cable protection are considered. The key elements of the convertible-to-arm leg are realized through concept/specific/mechanical design and implementation process with a suitable joint actuator/gear/controller selection procedure. In order to verify the performance of the manufactured convertible-to-arm leg, a 25bar pressure-resistant and watertight test using a high-pressure chamber and a joints operating test with posture control of the CR200 are performed. This paper describes the whole design, realization and verification process for implementation of the underwater convertible-to-arm leg.

• Special Issue of the Society of Naval Architects of Korea
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• 2006.09a
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• pp.112-121
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• 2006

The vertical displacement of a ship on the basis of the sea level is an important parameter for its stability and control. To indicate the displacement on operating conditions, "draft marks" are carved on the hull of the ship in various ways. One of the methods is welding. The position, shape and size of the marks are specified on the shipbuilding rules by classification societies to be checked by shipbuilders. In most cases, high-skilled workers do the welding along the drawing for the marks and welding bead becomes the marks. But the inaccuracies due to human errors and high labor cost increase the needs for automating the work process of the draft marks. In the preceding work, an indoor robot was developed for automatic marking system on flat surfaces and the work proved that the robot welding was more effective and accurate than manual welding. However, many parts of the hull structure constructed at the outdoor are cowed shapes, which is beyond the capability of the robot developed for the indoor works on the flat surface. The marking on the curved steel surface requiring the 25m elevations is one of the main challenges to the conventional robots. In the present paper, the robot capable of climbing vertical curved steel surfaces and performing the welding at the marked position by effectively solving the problems mentioned earlier is presented.

• International Journal of Advanced Culture Technology
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• v.7 no.4
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• pp.313-320
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• 2019

Nowadays, as the availability of tiny, low-cost microcomputer increases at a high level, mobile robots are experiencing remarkable enhancements in hardware design, software performance, and connectivity advancements. In order to control Turtlebot 2, several algorithms have been developed using the Robot Operating System(ROS). However, ROS requires to be run on a high-cost computer which increases the hardware cost and the power consumption to the robot. Therefore, design an algorithm based on low-cost hardware is the most innovative way to reduce the unnecessary costs of the hardware, to increase the performance, and to decrease the power consumed by the computer on the robot. In this paper, we present a path-finding algorithm for TurtleBot 2 based on low-cost hardware. We implemented the algorithm using Raspberry pi, Windows 10 IoT core, and RPLIDAR A2. Firstly, we used Raspberry pi as the alternative to the computer employed to handle ROS and to control the robot. Raspberry pi has the advantages of reducing the hardware cost and the energy consumed by the computer on the robot. Secondly, using RPLIDAR A2 and Windows 10 IoT core which is running on Raspberry pi, we implemented the path-finding algorithm which allows TurtleBot 2 to navigate from the starting point to the destination using the map of the area. In addition, we used C# and Universal Windows Platform to implement the proposed algorithm.

• Journal of Auto-vehicle Safety Association
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• v.13 no.4
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• pp.14-19
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• 2021

This paper presents LiDAR static obstacle map based vehicle dynamic state estimation algorithm for urban autonomous driving. In an autonomous driving, state estimation of host vehicle is important for accurate prediction of ego motion and perceived object. Therefore, in a situation in which noise exists in the control input of the vehicle, state estimation using sensor such as LiDAR and vision is required. However, it is difficult to obtain a measurement for the vehicle state because the recognition sensor of autonomous vehicle perceives including a dynamic object. The proposed algorithm consists of two parts. First, a Bayesian rule-based static obstacle map is constructed using continuous LiDAR point cloud input. Second, vehicle odometry during the time interval is calculated by matching the static obstacle map using Normal Distribution Transformation (NDT) method. And the velocity and yaw rate of vehicle are estimated based on the Extended Kalman Filter (EKF) using vehicle odometry as measurement. The proposed algorithm is implemented in the Linux Robot Operating System (ROS) environment, and is verified with data obtained from actual driving on urban roads. The test results show a more robust and accurate dynamic state estimation result when there is a bias in the chassis IMU sensor.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.5
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• pp.64-72
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• 2004

An extension of interaction matrix formulation to the problem of system and disturbance identification for a plant that is corrupted by both process and output disturbances is presented. The teaming control develops controllers that learn to improve their performance at executing a given task, based on experience performing this task. The simplest forms of loaming control are based on the same concept as integral control, but operating in the domain of the repetitions of the task. This paper studies the use of such controllers in a decentralized system, such as a robot moving on the vertical plane with the controller for each link acting independently. The basic result of the paper is to show that stability and iterative precision of the learning controllers for all subsystems when the coupling between subsystems is turned off, assures stability of the decentralized teaming in the coupled system, provided that the sample time in the digital teaming controller is sufficiently short. The methods of teaming system are shown up for the iterative precision of each link.