Chintae Choi

Practical Nonsingular Terminal Sliding-Mode Control of Robot Manipulators for High-Accuracy Tracking Control

This paper presents a practical nonsingular terminal sliding-mode (TSM) tracking control design for robot manipulators using time-delay estimation (TDE). The proposed control assures fast convergence due to the nonlinear TSM, and requires no prior knowledge about the robot dynamics due to the TDE. Despite its model-free nature, the proposed control provides high-accuracy control and robustness against parameters variations. The simplicity, robustness, and fast convergence of the proposed control are verified through both 2-DOF planar robot simulations and 3-DOF PUMA-type robot experiments.

High-Accuracy Tracking Control of Robot Manipulators Using Time Delay Estimation and Terminal Sliding Mode

A time delay estimation based general framework for trajectory tracking control of robot manipulators is presented. The controller consists of three elements: a time-delay-estimation element that cancels continuous nonlinearities of robot dynamics, an injecting element that endows desired error dynamics, and a correcting element that suppresses residual time delay estimation error caused by discontinuous nonlinearities. Terminal sliding mode is used for the correcting element to pursue fast convergence of the time delay estimation error. Implementation of proposed control is easy because calculation of robot dynamics including friction is not required. Experimental results verify high-accuracy trajectory tracking of industrial robot manipulators.

High-accuracy trajectory tracking of industrial robot manipulators using time delay estimation and terminal sliding mode

A time delay estimation based general framework for trajectory tracking control of robot manipulators is presented. The controller consists of three elements: a time-delay-estimation element that cancels continuous nonlinearities of robot dynamics, an injecting element that endows desired error dynamics, and a correcting element that suppresses residual time delay estimation error caused by discontinuous nonlinearities. Terminal sliding mode is used for the correcting element to pursue fast convergence of the time delay estimation error. Implementation of proposed control is easy because calculation of robot dynamics including friction is not required. Experiment results verifies high-accuracy trajectory tracking of robot manipulators.

Development of Localization Sensor System for Intelligent Robots

A service robot can identify its own position relative to landmarks, the locations of which are known in advance. The main contribution of this research is that it gives various ways of making the self-localizing error smaller by referring to special landmarks which are developed as high gain reflection material and coded array associations. In this paper, the authors propose a set of indices to evaluate the accuracy of self-localizing methods using the selective reflection landmark and infrared projector, and the indices are derived from the sensitivity enhancement using 3D distortion calibration of camera. And then, the accurarcy of self-localizing a mobile robot with landmarks based on the indices is evaluated, and a rational way to minimize to reduce the computational cost of selecting the best self-localizing method. The simulation results show a high accuracy and a good performance.

Control Architecture Design for an Gas Cutting Robot

This paper describes preliminary results from using reactive control architecture, known as CAPSC (Control Architecture for Poor Strip Cutting), which is designed for a gas cutting robot in Gwangyang steelworks, South Korea. This gas cutting mobile robot, called APSCR (Autonomous Poor Strip Cutting Robot) is designed to identify the poor strips, move an initial cutting position, and start to cut over 60 m long poor strip every 9 m by using a gas cutting- torch. Since its working environment is extremely complex to robots functionalities and furthermore robot must deal with explosive tanks, APSCR requires more appropriate control architecture in order to provide the following criterions; safety and simplicity. One of the popular control architectures successfully applied to the service mobile robots, reactive control architecture, is employed as primary control such as navigation, obstacle detection, cutting and so on. Besides, walkthrough procedure for safety is implemented to supervise all possible risks to workers and robot for itself. The experimental results are provided to prove a reliability of the proposed architecture.

Automatic Coil-Handling Crane Control System

Lots of researches and applications on the automated overhead cranes in shops have been done for some decades, but a few successful results are reported. A more reasonable control system fit to requirements of manufacturing industries is suggested in the study. The controller was designed in the continuous time domain by loop-shaping method. Sway of the rope is suppressed by anti-sway control method. The sway angle of the rope is measured by a sway angle sensor which is mechanically in contact with the rope. The real-time control law is comprised of the position and the anti-sway controller. Some algorithms required for coil yard operation as well as main control algorithms such as reference position generation, position control and anti-sway control have been designed and fully tested on a crane in the steel-making works. The designed crane control system showed satisfactory performance on position control accuracy and anti-sway of rope. The maximum positional error is 20 mm and the maximum sway error is 0.07 degrees in the destination position.

Control Architecture Design and Localization for a Gas Cutting Robot

Conventional control architecture which has been employed in mobile robot control software is divided into two categories such as knowledge-based and behavior-based control architecture. Early implementation of control architecture was mainly focused on building for sensing the environment, modeling it, planning based on this perceived model and executing the planned action to achieve a certain task. This design approach is called sense-model-plan-act (SMPA) or knowledge-based. A mobile robot making use of a knowledge-based controller tries to achieve its goal by following closely the sense-modelplan-act procedure. SMPA controller also needs initial knowledge, required to model its task environment prior for the robots to executing the planned task. Hence, if the initial knowledge is suited to its working environment, the resulting tasks guarantee success. Although the resulting overall behavior is predictable, the controller often suffers from being slow and becomes complex as it deals with a dynamic environment because most of the controller processing time is consumed in building a model, doing general perception and planning. Therefore, it is suitable controller for robots to require high-level intelligence and work in static and predictable environment. Brooks proposed a radically different approach in the design of mobile robot control architecture to address the drawback of knowledge-based control architecture. This control architecture functions a horizontal computation scheme so that each behavior is a fixed action pattern with respect to the sensory information. When the mobile robot is confronted by a dynamic environment, a behavior-based robot can react fast because of the direct coupling between its behaviors and the sensed states. The robot controller can be built incrementally, thus making it highly modular and easy to construct. However, this reactive approach still suffers from planning the productive and efficient actions in an unstructured environment because they are only confined to reactions to sensors and the changing states of other modules. In this chapter, we address the functional safety problems potentially embedded in the control system of the developed mobile robot and introduce a concept of Autonomous Poor Strip Cutting Robot (APSCR) control architecture with a focus on safety in order to design the walkthrough procedure for each behavior. In section 2, we explain the working environment where the robot will be manually or autonomously operated. Section 3 explains the control architecture of APSCR. In section 4, we explain the localization system of APSCR. Finally, section 5 shows some experimental result and in section 6 conclusions will be lastly addressed.

Roll Replacing Robot Systems for Wire-rod Press Roll

This paper presents the development of roll replacement robot system for wire-rod press rolls. The roll replacement robot system consist of a palletized railway truck, a 6-DOF industrial robot manipulator, a roll changing tool and a hydraulic power system. Results of simulation and pilot experiment show the roll changing task can be successfully automated using proposed robot system.

Development of Automation Strapping Machine Using PET Band

We present an equipment development for PET banding header that complements the steel banding machine currently being installed in Pohang Steel Works, South Korea. The PET banding header was developed due to the damage done on the surface of the cold rolling products whilst being transported. Because the PET Banding Header was designed as a friction-binding technology against the existing heat binding technology, the intensity concentrated on the binding area was significantly improved and its efficiency was also increased because it was designed to be a wider range of the banding. In addition, for the cost-cutting of the new equipment in development, the PET Banding header allows for both the Steel Banding Machine and PET Banding Machine to be utilized together. As a result, being applied to the facilities in the field, we were able to reduce the facility investment, demonstrate the efficient facility maintenance, and more importantly, solve the complaints from the customers.

Integrated local path planning method

We describe an integrated local path planning method whereby a particle filter is used for computation of the steering direction based on the Vector Field Histogram. In the original VFH, a typical polar histogram contains peaks (i.e., sectors) with a high polar obstacle density (POD) and valleys (i.e., sectors) that contain low polar obstacle density. In order to determine a desired path allowable for the width of the vehicle, the valley below some threshold is selected for the traversable local path. In the proposed approach, the particle filter is used to select the widest valley without the predefined threshold over the polar histogram and the measurement model of the particle filter is used for the uncertainty of each cell in the VFH as well. Experimental results from a mobile robot traversing the obstacle courses demonstrate the proposed approach successfully selecting and driving the most traversable path.