• Title, Summary, Keyword: Sliding velocity

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A Study on the Sliding Mode Control of Nonlinear Systems (비선형 시스템의 슬라이딩 보드 제어에 관한 연구)

  • 이태봉;박윤열;한상수
    • Journal of the Korean Institute of Telematics and Electronics B
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    • v.31B no.5
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    • pp.58-64
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    • 1994
  • In this paper, a robust control scheme of a nonlinear system with norm bounded uncertainty is studied. The proposed algorithm is based on variable structure systems (VSS) theory. the sliding mode which is robust to plant uncertainty and disturbances is obtained by regulating a sliding surface equation. This VSS control law can improve the robustness of control systems by adjusting the minimum reaching velocity in a reaching phase. A numerical example is given to verify the effectiveness of the control law.

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Sliding Mode Controller Design for Biped Robot (이족보행로봇을 위한 슬라이딩 제어기 설계)

  • Park, In-Gyu;Kim, Jin-Geol;Kim, Ki-Sik
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.5
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    • pp.137-146
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    • 2001
  • A robust controller with the sliding mode is proposed for stable dynamic walking of the biped robot in this paper. For the robot system to be controlled, which is modeled as 14 DOF rigid bodies by the method of multi-body dynamics, the joint angle trajectories are determined by the velocity transformation matrix. Also Hertz force model and Hysteresis damping element are utilized for the ground reaction and impact forces during the contact with the ground. The biped robot system becomes unstable since those forces contain highly confused noise components and some discontinuity, and modeling uncertainties such as parameter inaccuracies. The sliding mode control is applied to solve above problems. Under the assumption of the bounded estimation errors on the unknown parameters, the proposed controller provides a successful way to achieve the stability and good performance in spite of the presence of modeling imprecisions of uncertainties.

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Robust Control of Biped Robot Using Sliding Mode Controller (슬라이딩 모드 제어기를 이용한 이족로봇의 강건제어)

  • Park, In-Gyu;Kim, Jin-Geol
    • Proceedings of the KSME Conference
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    • pp.576-583
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    • 2000
  • A robust position control using a sliding mode controller is adopted for the stable dynamic walking of the biped. For the biped robot that is modeled with 14 degrees of freedom rigid bodies using the method of the multibody dynamics, the joint angles for simulation are obtained by the velocity transformation matrix using the given Cartesian foot and trunk trajectories. Hertz force model and Hysteresis damping element which is used in explanation of the energy dissipation during contact with ground are used for modeling of the ground reactions during the simulation. By the obtained that forces which contains highly confused noise elements and the system modeling uncertainties of various kinds such as unmodeled dynamics and parameter inaccuracies, the biped system will be unstable. For that problems, we are adopting a nonlinear robust control using a sliding mode controller. Under the assumption that the esimation error on the unknown parameters is bounded by a given function, that controller provides a successful way to preserve stability and achieve good performance, despite the presence of strong modeling imprecisions or uncertainties.

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Friction Characteristics of DLC and WC/C (DLC와 WC/C의 마찰특성)

  • Kim, Dong-Wook;Kim, Kyung-Woong
    • Tribology and Lubricants
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    • v.27 no.6
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    • pp.308-313
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    • 2011
  • In this study, friction tests were performed in order to investigate the effect of sliding velocity and normal load on the friction characteristics of DLC (a-C:H) and WC/C (a-C:H:W) using a ball-on-disk type friction tester. DLC and WC/C were deposited on AISI 52100 steel balls. Friction tests against carburized SCM 415 Cr-Mo steel disks were carried out under various sliding velocity (0.1, 0.78, 1.56, 3.13, 6.25, 12.5, 25, 50 and 100 mm/s) and normal load (2.4, 4.8 and 9.6 N) conditions while the relative humidity was 20~40 % R.H. and air temperature was $16{\sim}24^{\circ}C$. As results, kinetic friction coefficients of DLC and WC/C were obtained under each test condition. The results show that the kinetic friction coefficients of DLC and WC/C generally increase with the increase in sliding velocity. And, under the same sliding velocity condition, the kinetic friction coefficients are almost constant regardless of normal load. In addition, the kinetic friction coefficients of DLC are lower than those of WC/C under the same test conditions.

The Effect of Finished Surface Orientation on Friction Characteristics in Boudary Lubrication (경계윤활에서의 가공방향에 대한 마찰특성의 연구)

  • 유응대;김태완;구영필;조용주
    • Tribology and Lubricants
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    • v.18 no.3
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    • pp.211-218
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    • 2002
  • The effect of characteristic of surface roughness and roughness patterns on friction was studied experimentally in boundary lubrication with reciprocating tribometer. Roughness was changed from Ra=0.2($\mu\textrm{m}$)to Ra=1.2($\mu\textrm{m}$). Three roughness pattern-transverse, oblique, longitudinal- were tested for various load and velocity. The experimental results show that the scuffing resistance of surfaces with transversal roughness pattern is higher than that of surface with longitudinal and obliq pattern. under the conditions of the roughness values of Ra=0.2, 0.5,1.0 and 1.2. surfacer roughness (Ra) was decreased with the normal load increased before scuffing occurred. oblique pattern and longitudinal pattern with Ra=0.2 and Ra=1.0 was higher scuffing load under low sliding velocity, but with Ra=0.5 was higher scuffing load under high sliding velocity.

TRACKING CONTROL DESIGN USING SLIDING MODE TECHNIQUES FOR SATELLITE FORMATION FLYING

  • Lim, Hyung-Chul;Bang, Hyo-Choong;Park, Kwan-Dong;Park, Pil-Ho
    • Journal of Astronomy and Space Sciences
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    • v.20 no.4
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    • pp.365-374
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    • 2003
  • Satellite formation flying is currently an active area of research in the aerospace engineering. So it has been researched by various authors. In this study, a tracking controller using sliding mode techniques was designed to control a satellite for the satellite formation flying. In general, Hill's equations are used to describe the relative motion of the follower satellite with respect to the leader satellite. However the modified Hill's equations considering the $J_2$ perturbation were used for the design of sliding mode controller. The extended Kalman filter was applied to estimate the state vector based on the measurements of relative distance and velocity between two satellites. The simulation results show that the follower satellite tracks the desired trajectory well by thruster operations based on the sliding mode control law.

FRICTION CHARACTERISTICS OF A PAPER-BASED FRICTION MATERIAL

  • Gao, H.;Barber, G.-C.;Chu, H.
    • International Journal of Automotive Technology
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    • v.3 no.4
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    • pp.171-176
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    • 2002
  • A bench test set-up is employed to simulate the friction characteristics of a paper-based friction material operating against a steel plate. Dry friction tests are run as well as tests with transmission fluids. Glazed friction material produces a negative coefficient of friction versus sliding velocity (f-v) curve for both dry friction and lubrication with transmission fluids. At low sliding speeds, the coefficient of friction when operating in transmission fluids for glazed friction materials is greater than that under dry friction. An appreciable negative f-v slope occurs at low sliding speeds for glazed friction materials when running with the transmission fluid. The friction material after running in produces a constant f-v curve under dry friction and a negative slope when lubricated with transmission fluid. At low sliding speeds, the coefficient of friction of the run-in friction material is lower than that of the glazed wet material. On the other hand, the run-in friction material has a larger friction coefficient than does the glazed friction material at higher sliding speeds.

A Study on the Wear Characteristics and the Mechanism of KP-4M Steel for Plastic Molding (플라스틱성형용 KP-4M강의 마멸특성 및 이의 기구에 관한 연구)

  • 박흥식;전태옥;김동호
    • Tribology and Lubricants
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    • v.12 no.1
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    • pp.22-28
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    • 1996
  • This study was undertaken to investigate the dry wear characteristics and mechanism of KP-4M steel for plastic molding against SKD 61 hardened by heat treatment. The wear test was carried out under different conditions such as sliding speed, contact pressure, sliding distance, with frictional tester of pin on disc type. The wear loss on variation of sliding speed was little in lower speed range below 0.5 m/sec and in higher speed range above 1.5 m/sec,'but wear loss was high in intermediate speed range. The critical sliding speed, which showed the maximum value of specific wear rate, became lower with increased contact pressure. Increasing the contact pressure, the critical sliding distance Lcr which the wear mechanism changes from severe wear to mild wear was increased due to the decrease of oxidation reaction velocity. Through this study we suggested a model of generation and elimination process of wear debris of KP-4M steel for plastic molding.

Control of Two-Wheeled Welding Mobile Robot For Tracking a Smooth Curved Welding Path (완만한 곡선경로 추적용 이륜 용접이동로봇의 제어)

  • Ngo Manh Dung;Phuong Nguyen Thanh;Kim Hak-Kyeong;Kim Sang-Bong
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • pp.85-86
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    • 2006
  • In this paper, a nonlinear controller based on adaptive sliding-mode method which has a sliding surface vector including new boundary function is proposed and applied to a two-wheeled voiding mobile robot (WMR). This controller makes the welding point of WMR achieve tracking a reference point which is moving on a smooth curved welding path with a desired constant velocity. The mobile robot is considered in view of a kinematic model and a dynamic model in Cartesian coordinates. The proposed controller can overcome uncertainties and external disturbances by adaptive sliding-mode technique. To design the controller, the tracking error vector is defined, and then the new sliding is proposed to guarantee that the error vector converges to zero asymptotically. The stability of the dynamic system will be shown through the Lyapunov method. The simulations is shown to prove the effectiveness of the proposed controller.

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The Analysis for Surface Hardening by Repeated Sliding Contact (반복 미끄럼 접촉에 의한 표면층의 경화에 대한 해석)

  • 박준목;김석삼
    • Tribology and Lubricants
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    • v.13 no.4
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    • pp.71-78
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    • 1997
  • Wear is affected by numerous factors-contact load, sliding velocity and distance, friction coefficient, material properties and environmental conditions. Among these wear factors, surface hardness is one of very important factors to determine wear. But surface hardness is varied by work hardening during repeated sliding contact. In this reason wear rate is increased or decreased with varying surface hardness, and transition of wear mechanism is happened. In this study, the surface hardening by accumulating residual stress was analyzed by considering the repeated sliding Hertzian contact model. The results showed that surface hardness was increased with increasing contact load, friction coefficient and contact number. And the depth of hardening layer, plastic layer and elastic layer depended upon contact load and number, but they didn't depend upon friction coefficient. The predicted surface hardness was about 1.5-1.8 times as hard as the material.