• 제어로봇시스템학회논문지
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• 제22권6호
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• pp.411-416
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• 2016

This paper presents the design methodology of an unknown input observer for Lipschitz nonlinear systems with unknown inputs in the framework of convex optimization. We use an unknown input observer (UIO) to consider both nonlinearity and disturbance. By deriving a sufficient condition for exponential stability in the linear matrix inequality (LMI) form, existence of a stabilizing observer gain matrix of UIO will be assured by checking whether the quadratic stability margin of the error dynamics is greater than the Lipschitz constant or not. If quadratic stability margin is less than a Lipschitz constant, the coordinate transformation may be used to reduce the Lipschitz constant in the new coordinates. Furthermore, to reduce the maximum singular value of the observer gain matrix elements, an object function to minimize it will be optimally designed by modifying its magnitude so that amplification of sensor measurement noise is minimized via multi-objective optimization algorithm. The performance of UIO is compared to a nonlinear observer (Luenberger-like) with an application to a flexible joint robot system considering a change of load and disturbance. Finally, it is validated via simulations that the estimated angular position and velocity provide true values even in the presence of unknown inputs.

• 전기학회논문지
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• 제64권3호
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• pp.451-457
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• 2015

In this paper, we consider the observer design problem that truly reflects the nonlinear stiffness of the manipulators. The two key ideas of our design are that (a) estimation error dynamics of the manipulator equipped with accelerometer dose not dependent on nonlinearities at the link part, when the measured signals are the motor position and the output of the accelerometer and (b) the nonlinear stiffness is indeed a Lipschitz function. In order to effectively compensate the nonlinear stiffness, the gain of the proposed observer is carefully chosen from the ARE(algebraic Riccati equations) which depend on Lipschitz constant. Comparative simulation result verifies the effectiveness of the proposed solution.

• 한국인터넷방송통신학회논문지
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• 제18권4호
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• pp.111-116
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• 2018

본 논문에서는 관절 각도계를 사용하여 관절가동범위의 측정하던 것을 각도계를 사용하지 않고 플렉서블 센서를 이용하여 측정하고 측정된 값을 스마트 디바이스와 연동하여 실시간 모니터링이 가능하게 하였다. 현재의 관절가동 범위 측정은 관절 각도기를 활용하여 사람이 직접 측정하고 있다. 이러한 방법은 측정하는 사람의 측정 방법과 위치에 따른 오류로 일관성 있는 측정이 어려워 오차가 발생할 수 있다. 그래서 측정해야 할 관절에 센서를 부착하여 관절의 운동 범위를 측정하였다. 측정을 위한 센서는 플랙서블 형태로 관절의 움직임에 따라 변화되는 저항 값을 측정하는 센서로서 센싱 된 값을 ROM 센서노드를 통하여 무선으로 스마트 디바이스로 전송될 수 있도록 하였다. 개발 된 ROM 측정 장치는 일반적인 관절 각도기를 활용한 측정보다 일관성 있는 측정이 이루어 질 수 있고 스마트 디바이스와 연동하여 실시간 모니터링 함으로써 관절의 움직임에 따른 신속한 진단으로 환자의 빠른 치료와 재활의료 발전에 도움이 될 것이다.

• 한국기계가공학회지
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• 제21권9호
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• pp.63-70
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• 2022

Laser welding has attracted great attention as a tool used to join electrical steel coils. In this study, laser butt welding for electrical steel coil joining was conducted using the Taguchi method. It was found that structural defects such as void sand cracks were not produced in welds. This indicated that the performance of laser welding in electrical steel was excellent. According to the Taguchi analysis, the total welding quality index (TWQI) considering the bead height and roughness and tensile strength of the weld joint was almost evenly affected by laser power, welding speed, and focal position. The optimum welding conditions to maximize the TWQI were a laser power of 1220W, welding speed of 90 mm/s, and a focal position of 1mm. The regress model predicting the TWQI was also developed using the surface response method. We found that the model predicts measured values with an average error of 16.36%.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.505-507
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• 2004

This paper presents a measurement of ZMP using FSR sensors, and then the ZMP control with measured ZMP on single leg. ZMP is mostly used as standard evaluation of stability of a humanoid robot. The ISHURO has 5 sensors which are mounted at each corner and center of a sole. ZMP is computed using a model of a humanoid robot and information from the joint encoders. And we may able to use measurement data from FSR sensors at the robot feet. IP(Integration Proportional) control algorithm is applied to position control of ZMP that is an error of desired ZMP between measured ZMP.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.331-336
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• 1995

In this past decade, industrial robot have substituted human workers successfully in certain areas, however, the applications are limited due to the shortcoming in their mechanism and control strategies. Many researchers, therefore, have focused on improving the mechanical and sensory capabilities. Developing mult-degree-of-freedom end effectors, in other words robot hands, is one of the topics that researchers have begun to improve the limitation. A set of direct drive type servo-pneumatic finger joint has been developed for a dexterous robot hand. To control the pneumatic finger joints, a prototype 4/3-way proportional control valve has been designed and tested as a preliminary, research for the control of the pneumatic finger joints. A series of experiments have been conducted to verify the performance characteristics of the valve and the conventional proportional error contral with minor-loop compensation has been used to control the anguar position of the finger joints.

• Journal of information and communication convergence engineering
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• 제9권2호
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• pp.155-160
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• 2011

In distributed source localization where sensors transmit measurements to a fusion node, we address the sensor selection problem where the goal is to find the best set of sensors that maximizes localization accuracy when quantization of sensor measurements is taken into account. Since sensor selection depends heavily upon rate assigned to each sensor, joint optimization of rate allocation and sensor selection is required to achieve the best solution. We show that this task could be accomplished by solving the problem of allocating rates to each sensor so as to minimize the error in estimating the position of a source. Then we solve this rate allocation problem by using the generalized BFOS algorithm. Our experiments demonstrate that the best set of sensors obtained from the proposed sensor selection algorithm leads to significant improvements in localization performance with respect to the set of sensors determined from a sensor selection process based on unquantized measurements.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1999년도 제14차 학술회의논문집
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• pp.21-24
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• 1999

There-have been many control strategies for the enact joint position tracking of flexible manipulators, but direct cartesian space tracking control methods an not developed well. In this paper, we propose a PD control method based on the cartesian error in the end point trajectory tracking. the proposed controller is composed of PD control combined with nonlinear saturation term hut has a very simple form. the effect of this term is continuous suppression of vibration which is induced by the coupling of rigid motion. This control works both on the regulation and on the tracking cases. The performance and validity of this control method is shown by simulation examples.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.1234-1236
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• 1996

In this paper, the trajectory needed to be tracked by the manipulator was defined in a new plot differently from conventional methods. And the trajectory provides Solution directly related to coordinates of output variables from the plant. So, it overcomes nonlinearity between joint and Cartesian coordinates in movement mode and it makes use of inverse Kinematics unnecessary, which was obstacle for real-time control. The 2-axis SCARA robot was modelled and simulation was performed to validate in this paper. And it proved this has better performance in rapidity and decrease of position-error, compared to the conventional FLCs.

• 로봇학회논문지
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• 제17권1호
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• pp.58-67
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• 2022

In this paper, we propose an approach resolving inaccuracy of the low-cost redundant manipulator workspace with low encoder and low stiffness. When the manipulators are manufactured with low-cost encoders and low-cost links, the robots can run into workspace inaccuracy issues. Furthermore, trajectory generation based on conventional forward/inverse kinematics without taking into account inaccuracy issues will introduce the risk of end-effector fluctuations. Hence, we propose an optimization for the trajectory generation method based on the DDPG (Deep Deterministic Policy Gradient) algorithm for the low-cost redundant manipulators reaching the target position in Euclidean space. We designed the DDPG algorithm minimizing the distance along with the jacobian condition number. The training environment is selected with an error rate of randomly generated joint spaces in a simulator that implemented real-world physics, the test environment is a real robotic experiment and demonstrated our approach.