• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.240-243
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• 2001

A conventional PID controller does not provide a proper response in face of various kinds of load variation. In this paper, Fuzzy-PID Control scheme are proposed in order to improve the performance of the PID Controller. The proposed control schemes are applied to the speed controller of AC servo motor systems. The effectiveness of the proposed methods is shown by implementation and the advantage of each control scheme is discussed.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10b
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• pp.964-968
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• 1988

In mechanical systems in which the dynamics of armatures is dominated by electrostatic forces, motions will generally be unstable. This paper deals with the control problems of this kind of micro electrostatic device systems. In these systems, the mass of micro mechanical parts is so small that the inertia term in the equation of motion is negligible. However, nonlinear terms, such as friction and driving force, become dominant. The purpose of this paper is to realize the stable motion without delay and, overshoot etc. A micro-mechanical system used in this paper consists of a plane wafer with striped electrodes converted with an insulation layer and thin cylindrical roller is placed over on it. The performance of motions is confirmed by some simulations.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.199-204
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• 2006

In this paper, we propose an adaptive control algorithm to improve the position accuracy and reduce the nonlinear friction effects for linear motion servo system. Especially, the considered system includes not only the variation of the mass of the mover but also the friction change by the normal force. To adapt to these problems, we designed the controller with the mass estimator and the compensator by observing the variation of normal force. Finally, the numerical simulation results are presented in order to show the effectiveness of the proposed method to improve the position accuracy compared to other control methods.

• Journal of Drive and Control
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• v.16 no.4
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• pp.56-64
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• 2019

Recently, as the environmental regulation for earth moving equipment has been tightened, advanced systems using electronic control have been introduced for energy savings. An IMV(Independent Metering Valve), which consists of four 2-way valves, is one of the electro-hydraulic control systems that provides more flexible controllability and potential for energy savings in excavators, when compared to the conventional 4-way spool valve system. To fully realize an IMV, a two-stage bi-directional flow control valve which can regulate the large amount of flow in both directions, should be developed in advance. A simple design that allows proportional flow control to apply the pilot pressure from the current-controlled solenoid to the spring loaded flow control spool and thus valve displacement, is proportional to the solenoid current. However, this open-loop type valve is vulnerable to flow force which directly affects the valve displacement. Force feedback servo of which the position loop is closed by the feedback spring which interconnects the solenoid valve and flow control spool, could compensate for the flow force. In this study, linearity for the solenoid current input and robustness against load pressure disturbance is investigated by linear analysis of the static nonlinear equations for the IMV proportional flow control valve with feedback spring. Gains of the linear system confirm the performance improvement with the feedback spring design.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.895-898
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• 2003

The higher precision is demanded in modem manufacturing and it requires the more accurate servo controller. Cross-coupling control (CCC) has been developed to improve contouring motion. In this paper we introduce a new nonlinear CCC that is based on contour-error-vector using a parametric curve interpolator. A vector from the actual tool position to the nearest point on the desire path is directly adopted. The contour-error-vector is determined by constructing a tangential vector of nearest point on desired curve and determining the vector perpendicular to this tangential vector from the actual tool position. Moreover, the vector CCC can apply directly and easily to free-form curves include convex and concave form. The experimental results on a three-axis CNC machine center show that the present approach significantly improves motion accuracy in multi-axis motion

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.229-229
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• 2000

Conventional gain-tuning methods such as Ziegler-Nickels methods, have many disadvantages that optimal control ler gain should be tuned manually. In this paper, modified PID controllers which include self-tuning characteristics are proposed. Proposed controllers automatically tune the PID gains in on-1ine using neural networks. A new learning scheme was proposed for improving learning speed in neural networks and satisfying the real time condition. In this paper, using a nonlinear mapping capability of neural networks, we derive a tuning method of PID controller based on a Back propagation(BP)method of multilayered neural networks. Simulated and experimental results show that the proposed method can give the appropriate parameters of PID controller when it is implemented to DC Motor.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.971-976
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• 1996

A flexible pointing system mounted on top of a vehicle suffers from performance degradation due to bending vibrations as the vehicle runs on a bump course. In order to improve the pointing performance, the pointing structure's vibrations should be suppressed. In this paper, a nonlinear controller is designed to control the tip position of the pointing system while actively suppressing the vibrations. To cope with high order dynamics and nonlinearities of the plant and hydraulic actuating system, a two-stage sliding mode controller is devised. The desired actuating pressure is obtained in the first stage and then the in put current In the hydraulic servo system is computed to generate the pressure. The simulation results show the effectiveness of this scheme and improvements in pointing accuracy.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.283-286
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• 2002

This paper presents the straightness compensation system which is a device for improving the machining accuracy of ultra-precision machines by synchronizing the position of diamond tool tip with machine error motion. Sine it is actuated by piezoelectric actuator with highly nonlinear hysteresis characteristics, the feedback control schemes such as Proportional Integral(PI), are required and realized by measuring the displacements of diamond tool tip. for the better tracking performance, the controller was implemented using TMS320C32 32bit floating-point DSP which is fast so that the real-time control is possible. In addition, stand alone type DSP board was chosen fur the easy assembly into the ultra-precision machines. The experimental results show good command tracking performance and the motion error of the machine is satisfactorily compensated during the machining process.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.5
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• pp.44-51
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• 2008

In this paper, the optimal tuning of a cross-coupled controller linked with the feedforward controller is studied to reduce contouring and tracking errors of a bi-axial servomechanisms by using the previously developed integrated tuning method. The CCC system for an arbitrary curve, which is combined with the feedforward controller, is formulated by a state-space based on a series of linear motion trajectories. An optimal tuning problem is formulated as a nonlinear constrained optimization problem including relevant controller parameters of the servo. To verify the effectiveness of the proposed optimal tuning procedure, linear and circular motion experiments are performed on the xy-table. Experimental results confirm that both tracking and contouring errors are significantly reduced by applying the proposed control and tuning system.

• International Journal of Aeronautical and Space Sciences
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• v.11 no.3
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• pp.167-174
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• 2010

The design, dynamics, and control allocation of tri-rotor unmanned aerial vehicles (UAVs) are introduced in this paper. A trirotor UAV has three rotor axes that are equidistant from its center of gravity. Two designs of tri-rotor UAV are introduced in this paper. The single tri-rotor UAV has a servo-motor that is installed on one of the three rotors, which enables rapid control of its motion and its various attitude changes-unlike a quad-rotor UAV that depends only on the angular velocities of four rotors for control. The other design is called 'coaxial tri-rotor UAV,' which has two rotors installed on each rotor axis. Since the tri-rotor type of UAV has the yawing problem induced from an unpaired rotor's reaction torque, it is necessary to derive accurate dynamic and design control logic for both single and coaxial tri-rotors. For that reason, a control strategy is proposed for each type of tri-rotor, and nonlinear simulations of the altitude, Euler angle, and angular velocity responses are conducted by using a classical proportional-integral-derivative controller. Simulation results show that the proposed control strategies are appropriate for the control of single and coaxial tri-rotor UAVs.