• Journal of Sensor Science and Technology
• /
• v.29 no.5
• /
• pp.348-353
• /
• 2020

This paper presents an adaptive method to avoid obstacles in various environmental settings, using a two-dimensional (2D) LiDAR sensor for mobile robots. While the conventional reaction based smooth nearness diagram (SND) algorithms use a fixed safety distance criterion, the proposed algorithm autonomously changes the safety criterion considering the obstacle density around a robot. The fixed safety criterion for the whole SND obstacle avoidance process can induce inefficient motion controls in terms of the travel distance and action smoothness. We applied a multinomial logistic regression algorithm, softmax regression, to classify 2D LiDAR point clouds into seven obstacle structure classes. The trained model was used to recognize a current obstacle density situation using newly obtained 2D LiDAR data. Through the classification, the robot adaptively modifies the safety distance criterion according to the change in its environment. We experimentally verified that the motion controls generated by the proposed adaptive algorithm were smoother and more efficient compared to those of the conventional SND algorithms.

• Journal of Welding and Joining
• /
• v.33 no.3
• /
• pp.12-18
• /
• 2015

The ultimate goal of developing body is revealed the "lightweight" at latest EuroCarBody conference 2012 and the most core technology is joining process to make lightweight car body design. Accordingly, in this study, the car body assembly line for the assembly process applies to any introduction, particularly in the assembly of aluminum alloy and composite materials applied by the process for the introductory approached. Process were largely classified by welding (laser, arc, resistance, and friction stir welding), bonding (epoxy bonding) and mechanical fastening (FDS, SPR, Bolting and clinching). Applications for each process issues in the case and the applicable award was presented, based on the absolute strength of the test specimens and joining characteristics for comparative analysis were summarized. Finally, through this paper, we would tried to establish the characteristics of the joint for lightweight structure.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.11 no.5
• /
• pp.367-372
• /
• 2001

This paper proposes a hierachically structured navigation algorithm for multiple mobile robots under unknown dynamic environment. The proposed algorithm consists of three basic parts as follows. The first part based on the fuzzy rule generates the turning angle and moving distance of the robot for goal approach without obstacles. In the second part, using both fuzzy and neural network, the angle and distance of the robot to avoid collision with dynamic and static obstacles are obtained. The final adjustment of the weighting factor based on fuzzy rule for moving and avoiding distance of the robots is provided in the third stage. Some simulation results show the effectiveness of the proposed algorithm.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.8 no.2
• /
• pp.50-59
• /
• 1998

This paper presents stabilization and adaptive control of flexible single link robot manipulator system by self-recurrent neural networks that is one of the neural networks and is effective in nonlinear control. The architecture of neural networks is a modified model of self-recurrent structure which has a hidden layer. The self-recurrent neural networks can be used to approximate any continuous function to any desired degree of accuracy and the weights are updated by feedback-error learning algorithm. When a flexible manipulator is rotated by a motor through the fixed end, transverse vibration may occur. The motor toroque should be controlled in such a way that the motor rotates by a specified angle, while simultaneously stabilizing vibration of the flexible manipuators so that it is arresed as soon as possible at the end of rotation. Accurate vibration control of lightweight manipulator during the large changes in configuration common to robotic tasks requires dynamic models that describe both the rigid body motions, as well as the flexural vibrations. Therefore, a dynamic models for a flexible single link robot manipulator is derived, and then a comparative analysis was made with linear controller through an simulation and experiment. The results are proesented to illustrate thd advantages and imporved performance of the proposed adaptive control ove the conventional linear controller.

• Journal of Institute of Control, Robotics and Systems
• /
• v.20 no.9
• /
• pp.936-941
• /
• 2014

Walking mechanisms are very important for legged robots to ensure their stable locomotion. In this research, Klann-linkage is suggested as a walking mechanism for a water-running robot and is optimized using level average analysis. The structure of the Klann-linkage is introduced first and design variables for the Klann-linkage are identified considering the kinematic task of the walking mechanism. Next, the design problem is formulated as a path generation optimization problem. Specifically, the desired path for the foot-pad is defined and the objective function is defined as the structural error between the desired and the generated paths. A process for solving the optimization problem is suggested utilizing the sensitivity analysis of the design variables. As a result, optimized lengths of Klann-linkage are obtained and the optimum trajectory is obtained. It is found that the optimized trajectory improves the cost function by about 62% from the initial one. It is expected that the results from this research can be used as a good example for designing legged robots.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.27 no.10
• /
• pp.53-59
• /
• 1990

In the control of robot manipulators, this paper presents a design of a new variable structure model following controller(VSMFC) using computed torque method (CTM). A sufficient condition for the existence of a sliding mode is derived by Lyapunov function. The reference model is a double integrators and the acceleration input consists of a proportional-derivative controller for the purpose of the stabilization of system and the desired performance. The proposed control scheme which consists of upper bounded and estimated value of each term of the manipulator of matrix inversion. Therefore the simulation results show that this controller is improved to the convergence of desired trajectories.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.04a
• /
• pp.478-482
• /
• 1996

This paper presents a new approach to the design of adaptive control system using DSPs(TMS320C50) for robotic manipulators to achieve trajectorytracking angles. Digital signal processors are used in implementing real time adaptive control algorithms to provide motion for robotic manipulators. In the proposed scheme, adapation laws are derived from the improved second stability analysis based on the indirect adaptive control theory.l The proposed control scheme is simple in structure, fast in computation, an suitable for implementation of real-time control. Moreover, this scheme does not requre an accurate dynamic modeling, nor values of manipulator paramenters and payload Performance of the adaptive controller is illustrated by exeperimental results for a SCARA robot.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.13 no.2
• /
• pp.117-123
• /
• 2014

In order to provide a mobile robot with omnidirectionality, various types of omnidirectional wheels have been developed. This paper deals with an improved design and structural analysis of a Mecanum wheel, which is the type of omnidirectional wheels most commonly used in industrial fields. A geometric formulation for manufacturingthe Mecanum wheel is presented and two types of Mecanum wheels are designed and fabricated in this research. While conventional assembled-type Mecanum wheels have a complicated structure and the high possibility of mutual interference between sub-components, a unified type of Mecanum wheel reduces the number of sub-components and increases the degree of structural rigidity. The stress and strain properties of the two designs are compared to confirm the quantitative improvement of the new design by a commercial structural analysis tool. The analysis results show that the unified type of Mecanum wheel has properties superior to the assembled type of Mecanum wheel in terms of its ability to reduce interference.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.38 no.6
• /
• pp.28-36
• /
• 2001

A robust adaptive sliding mode robot control algorithm is derived, which consists of a feed-forward compensation part and discontinuous control part. The unknown parameters is categorized into two groups, with group containing the parameters estimated on-line, and group containing the parameters not estimated on-line. Then a sliding control term is incorporated into the torque input in order to account for the effects of uncertainties on the parameters not estimated on-line and of disturbances. Moreover, the algorithm is computationally simple, due to an effective exploitation of the structure of manipulator dynamics. It is shown that, despite the existence of the parameter uncertainty and external disturbances, the controller is globally asymptotically stable and guarantees zero tracking errors.

• Journal of the Korean Society of Industry Convergence
• /
• v.18 no.3
• /
• pp.139-149
• /
• 2015

In this paper, we describe a new approach to perform real-time implementation of an robust controller for robotic manipulator based on digital signal processors in this paper. The Texas Instruments DSPs chips are used in implementing real-time adaptive control algorithms to provide enhanced motion control performance for dual-arm robotic manipulators. In the proposed scheme, adaptation laws are derived from model reference adaptive control principle based on the improved direct Lyapunov method. The proposed adaptive controller consists of an adaptive feed-forward and feedback controller and time-varying auxiliary controller elements. The proposed control scheme is simple in structure, fast in computation, and suitable for real-time control. Moreover, this scheme does not require any accurate dynamic modeling, nor values of manipulator parameters and payload. Performance of the proposed adaptive controller is illustrated by simulation and experimental results for robot manipulator consisting of dual arm with eight degrees of freedom at the joint space and cartesian space.