• Title/Summary/Keyword: Precision Position Control

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Precise position control of piezoelectric actuators considering input frequency variance (입력주파수 변화특성을 고려한 압전구동기의 정밀위치제어)

  • 송재욱;김호상;이효정
    • 제어로봇시스템학회:학술대회논문집
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    • 1996.10b
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    • pp.1052-1055
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    • 1996
  • Piezoelectric actuator is widely used in precision positioning applications due to its excellent positioning resolution. However, serious hysteresis nonlinearity of the actuator deteriorates its precise positioning capability. Evenworse, its hysteresis nonlinearity changes as the actuator input frequency varies. In this study, a simple feedforward scheme is proposed and tested through experiments for precision position control when the variance of the system input frequency is significant.

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Position Control of Ultra-Precision Machine Tool Postusing Piezoelectric Material) (압전재료를 이용한 초정밀 가공기용 공구위치제어)

  • 김태형
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 1996.10a
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    • pp.28-33
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    • 1996
  • This paper presents a position control of ultra-precision machine tool post using piezoelectric material. A stack-type piezoelectric actuator is employed in a hinge-type tool holder. An assumed linear transfer function of the practical nonlinear plant is established through the comparison of transfer functions and step responses in the experiments and the simulations. Several types of feedforward/feedback controllers are designed via computer simulations using the assumed linear transfer function, The position tracking control experiments are undertaken to show the control efficiency of each controller.

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Study on the Effective Operating Method of on-off Valves for a Pneumatic Servo System (개폐식 밸브를 사용한 공기압 서보 시스템의 효율적 밸브 개폐 방법에 관한 연구)

  • 황웅태;최서호;이정오
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.1
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    • pp.109-116
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    • 1998
  • This paper is concerned with effective operating method of pneumatic on-off valves for improving position control accuracy, valve life-time and position settling time using modified pulse width modulation with dead-zone (MPWMD). The pneumatic system using on-off valves has advantage of simple construction and low cost compared with a system with servo-valves. The performance of the proposed control method is investigated experimentally for the position control of a pneumatic cylinder using on-off valves. Experimental results show that the proposed algorithm for valve operation can be used to obtain fast and accurate position control compared to the conventional PWMD algorithm. It is also shown that the use of the proposed MPWMD algorithm for the position control significantly reduces the number of valve switching and noise.

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Hybrid Position/Force Control of 3 DOF Robot (3자유도 로봇의 하이브리드 위치/힘 제어)

  • 양선호;박태욱;양현석
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.04a
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    • pp.772-776
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    • 1997
  • For a robot to perfom more versatile tasks, it is invitable for the robot's end-effector to come into contact with its environment. In thos case, to achieve better performance, it is necessary to properly control the contact force between the robot and the environment. In thos work, hybrid control theory is studied and is verified through experiment using a 3 DOF robot. In the experiment, two position/force controllers are used. Fist, proportional-integral-derivative controller is used as the controller for both position and force. Second, computed-torque method is used as the position controller, and proportional-integral-derivative controller is used as the force controller. For a proper modeling used in computed-torque method, the friction torque is measured by experiment, and compensation method is studied. The hybrid control method used in this experiment effectively control the contact force between the end-effector and the environment for various types of jobs.

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Disturbance Observer and Error Model-based Control of Ball Screw Drives

  • Cho, Chang-Nho;Lee, Chang-Hyuk;Kim, Hong-Ju
    • Journal of the Korean Society of Industry Convergence
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    • v.22 no.4
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    • pp.435-445
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    • 2019
  • Ball screw drives are widely used in industry, and many studies have been devoted on precise, fast and robust control of ball screw drives. In this study, a novel position control algorithm for ball screw drives is proposed, which consist of a PD controller, a friction feedforward and a disturbance observer. The dynamics and the position error of such controller are analyzed to establish an error model, which can be used to predict the resulting position error of the given desired trajectory. Using the proposed error model, the desired trajectory can be modified so that the predicted position error can be compensated in a feedforward manner. The proposed algorithm does not require the model of the system for the error prediction, and thus can be easily applied to conventional control systems. The performance of the system is verified through simulations and experiments.

A Study on Adaptive Load Torque Observer for Robust Precision Position Control of BLDC Motor (적응제어형 외란 관측기를 이요한 BLDC 전동기의 정밀위치제어에 대한 연구)

  • 고종선;윤성구
    • Proceedings of the KIPE Conference
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    • 1999.07a
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    • pp.4-9
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    • 1999
  • A new control method for precision robust position control of a brushless DC (BLDC) motor using asymptotically stable adaptive load torque observer is presented in the paper. Precision position control is obtained for the BLDC motor system approximately linearized using the field-orientation method Recently, many of these drive systems use BLDC motors to avoid backlashe. However, the disadvantages of the motor are high cost and complex control because of nonlinear characteristics. Also, the load torque disturbance directly affects the motor shaft. The application of the load torque observer is published in [1] using fixed gain. However, the motor flux linkage is not exactly known for a load torque observer. There is the problem of uncertainty to obtain very high precision position control. Therefore a model reference adaptive observer is considered to overcome the problem of unknown parameter and torque disturbance in this paper. The system stability analysis is carried out using Lyapunov stability theorem. As a result, asymptotically stable observe gain can be obtained without affecting the overall system response. The load disturbance detected by the asymptotically stable adaptive observer is compensated by feedforwarding the equivalent current which gives fast response. The experimenta results are presented in the paper.

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A Study on the Position Detection for the Linear Pulse Motor (Linear Pulse Motor의 위치검출에 관한 연구)

  • Shin, C.S.;Kim, N.H.;Lee, H.K.;Kim, Y.S.;Roh, C.J.
    • Proceedings of the KIEE Conference
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    • 1995.07b
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    • pp.735-737
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    • 1995
  • Linear pulse motor(LPM) has been used in a wide range of application due to many advantages for the precision position and speed control system for the bidirectional linear motion. In this study, the hybrid, single-side type LPM was designed and examined for characteristics of position detection. Precision position detection signals could be sensed by synchrnous rectifier method from the LPM stator scale. Experimental results show that the position precisions are good enough to perform the LPM position control.

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A Simulation Study of Position Control Performance of a Shape Memory Alloy-Actuated Flow Control Valve (형상기업합금을 이용한 유량제어밸브의 위치제어 적용 시뮬레이션)

  • Choi, Su-Hyun;Lee, Han-Suk;Kuk, Kum-Hoan
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.8
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    • pp.79-87
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    • 1999
  • In this study, a new type of flow control valve which is SMA actuated flow control valve is presented. The flow control valve is actuated by a small motion of shape memory alloy. The performance of this valve as a position control component is analyzed by computer simulation. A variable structure control technique is applied for the position control by the flow control valve. The position control performance of the valve is evaluated on the step responses of a PID control by a electrohydraulic servo valve. For the simulation study, first, the mathematical model of a hydraulic system, which is consisted of the flow control valve and a hydraulic cylinder, is formulated. This mathematical model and the designed variable structure control algorithm are then combined by the MATLAB software. The same sequence of work is carried out for the PID position control system with a electrohydraulic servo valve. The simulation results show the validity of the new type of flow control valve as a variable position control component.

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Position and Pressure Control Using Hydraulic Axis Digital Controller (유압단축제어기(HACD)를 사용한 위치 및 압력제어)

  • Kim, D.H.;Huh, J.Y.
    • Transactions of The Korea Fluid Power Systems Society
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    • v.8 no.2
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    • pp.29-35
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    • 2011
  • These days the injection molding work and press work are in the trend of needing the precision control of position and pressure in a high speed. On the other hand the digital computer technology is developing rapidly. And recently the digital servo controller using micro controller become to be used more broadly, because of the merit of digital communication. In this study the sequential control of hydraulic system switching from position to pressure and to position is tried using the HACD(Hydraulic Axis Controller Digital for electrohydraulic drives) which is manufactured by BoschRexroth. Through this, the possibility of the precision sequential control using the digital servo controller HACD is examined.

Control Method for the Tool Path in Aspherical Surface Grinding and Polishing

  • Kim, Hyung-Tae;Yang, Hae-Jeong;Kim, Sung-Chul
    • International Journal of Precision Engineering and Manufacturing
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    • v.7 no.4
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    • pp.51-56
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    • 2006
  • This paper proposes a control algorithm, which is verified experimentally, for aspherical surface grinding and polishing. The algorithm provides simultaneous control of the position and interpolation of an aspheric curve. The nonlinear formula for the tool position was derived from the aspheric equation and the shape of the tool. The function was partitioned at specific intervals and the control parameters were calculated at each control section. The position, acceleration, and velocity at each interval were updated during the process. A position error feedback was introduced using a rotary encoder. The feedback algorithm corrected the position error by increasing or decreasing the feed speed. In the experimental verification, a two-axis machine was controlled to track an aspherical surface using the proposed algorithm. The effects of the control and process parameters were monitored. The results demonstrated that the maximum tracking error with tuned parameters was at the submicron level for concave and convex surfaces.