• 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.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.2
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• pp.215-220
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• 1988

The oscillatory hydraulic servosystem and the stable hydraulic servosystem under proportional control were feedback-controlled respectively using the estimated states of the observer. The observer was constructed in the analog computer and then it was interfaced with the real hydraulic servosystem to excute the experiment. As a result of experiment, the system that had been stable under proportional control responded more rapidly than before and the system that had shown oscillatory phenomenon under proportional control became stable with the same maximum acceleration and velocity that it had started under proportional control.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10a
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• pp.206-209
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• 1988

For feedback control of a linear dynamic system the optimum linear slace regulator (OLSR) can be implemented only if all state are available for feedback. This work demonstrates that when only the output state is available for feedback, a nonlinear controllers can be improved performance over that obtained by a proportional controller. This paper found the optimal control law by well-known dynamic programming and principles of optimality. Thus, performance of both proportional and nonlinear controllers is compared with performance of optimum linear state regulator.

• Journal of Biomedical Engineering Research
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• v.5 no.2
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• pp.133-142
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• 1984

The EMG signal can be considered as a signal source that expresses the intention of man because it is a electrical signal generated when the man contracts muscles. For proportional control of prostheses, the control signal proportional to the mousle contraction level must be estimated. Typically a foul-wave rectifier and low-pass filter are used to estimate the proportional control signal from the EMG signal. In this paper, it is proposed to use a logarithmic transformation and a linear minimum mean square error estimator. A logarithmic transformation maps the myoelectric signal into an additive control signal-plus-noise domain and the Kalman filter is used to estimate the control signal as a linear minimum mean square error estimator. The performance of this estimator is verified by the computer simulation and the estimator is applied to the EMG obtained from the biceps brachii muscle of normal subjects.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2753-2756
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• 2007

In the present study, we reduce the drag and lift fluctuations of the sphere by providing a linear proportional control. For this purpose, we measure the radial velocity along the centerline in the wake and provide blowing and suction at a part of sphere surface based on the measured velocity. Zero-net mass flow rate is satisfied during the control. This control is applied to the flow over a sphere at Re=300 and 425. We vary the sensing location at $0.8d{\leq}X_s{\leq}1.3d$ and find that the most effective sensing region coincides with the location at which minimum correlation between the lift and sensing-velocity directions occurs. As a result, the lift and drag fluctuations are significantly reduced.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.12-14
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• 1999

Recently, the electromagnetic proportional valve has been widely used in order to control pressure and flow in such systems as NC machine and automatic facility. The linear electromagnetic solenoid used for proportional control valve ought to have hysteresis characteristic because of control the thrust force proportionably by input current. Therefore, in this study, we analysis the thrust force characteristics and established design for practical use, which allows Linear Pulse Motor(LPM) to be used as a driving system for electromagnetic proportional control valves.

• Journal of Power Electronics
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• v.15 no.1
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• pp.177-189
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• 2015

The output of the controller is said to exceed the input limits of the plant being controlled when a control system operates in a non-linear region. This process is called the windup phenomenon. The windup phenomenon is not preferable in the control system because it leads to performance degradation, such as overshoot and system instability. Many anti-windup strategies involve switching, where the integral component differently operates between the linear and the non-linear states. The range of state for the non-overshoot performance is better illustrated by the boundary integral error plane than the proportional-integral (PI) plane in windup inspection. This study proposes a PI controller with a separate closed-loop integral controller and reference value set with respect to the input command and external torque. The PI controller is compared with existing conventional proportional integral, conditional integration, tracking back calculation, and integral state prediction schemes by using ScicosLab simulations. The controller is also experimentally verified on a direct current motor under no-load and loading conditions. The proposed controller shows a promising potential with its ability to eliminate overshoot with short settling time using the decoupling mode in both conditions.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.482-485
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• 1996

We design a homing guidance law based on the proportional navigation for the fast-rolling, single-axis control missiles and analyse the misdistance of the designed guidance system. The guidance law includes a compensation scheme which compensates for the phase-shift between the commanded and achieved acceleration which is peculiar to the fast rolling airframe with single-axis control. In the error analysis of the guidance system, we calculate the misdistance with respect to the target maneuver on the 3-dimensional space via direct simulations. Also, we conduct adjoint simulation on the 2-dimensional plane in case that phase-shift is perfectly compensated. Finally we approximate the linear time-varying dynamics of the missile with autopilot to a linear time-invarient system, and as a result we can find the misdistance as a closed-form.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.7
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• pp.84-91
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• 2012

In this paper, design by magnetic analysis software and proportional control of solenoid for pressure valve for electric pressure cooker is described. The validation of design was proved by 3D finite element analysis results. Also the efficiency of an air ventilation mechanism was considered when pressure was happened by fluid analysis results. The linear proportional control system by AVR was manufactured and its validation was proved by pressure control of solenoid.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.5
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• pp.781-788
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• 1987

The state variables estimated in an observer were useed in feedback control of a hydraulic servosystem to increase the system stability and to enhance the system performance. The nonlinear hydraulic servosystem with the inherent nonlinearities due to the square root function of flow equation, the Coulomb friction and so on, was modelled as a fourth order linear hydraulic servosystem. Also, a second order linear system was derived for the observer-controller design. For these models, a fourth order linear observer and a second order linear observer were constructed respectively to evaluate the performance of the observer-based hydraulic servosystem. The results obtained from series of simulation showed that the system which had shown oscillatory phenomenon under proportional control became stable with the same maximum acceleration and velocity that it had started under proportional control.