• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.168-170
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• 1997

This paper presents the dynamic analysis of a reciprocating actuation system based on moving magnet actuator for gas compression. For the analysis of the linear actuator, an axisymmetric finite element method (FEM) considering the saturation effect of the magnetic material is used, and electrical circuit equation, mechanical dynamic equation and pressure dynamics are coupled. In the FE analysis, we adopt a moving line technique. The pressure dynamics of the gas in the compressor is modeled by using the law of thermodynamics. The analysis results are compared fairly well with experimental ones.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.93-94
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• 2007

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1812-1818
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• 2005

Even though SMA actuators have high power to volume ratio, there exist disadvantages such as hysteresis and saturation. So the model identification for SMA actuators is very difficult. For the qualitative model identification, we described the behavior of SMA actuators using a so-called diagonal model, which can readily expect the turning point of an incomplete phase transformation. For the quantitative model identification, we developed the general dynamics of SMA actuators using the modified Liang's model. Using this dynamics we can describe the hysteresis and the saturation very well. It is also very important to notice that the modified Liang's model maintains a continuous martensite fraction at the change of the phase transformation but the original model cannot.

• International Journal of Control, Automation, and Systems
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• v.6 no.3
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• pp.327-338
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• 2008

A fault tolerant control system design technique has been proposed and analyzed for managing performance degradation in the presence of multiple faults in actuators. The method is based on a control structure with a model reference reconfigurable control design in an inner loop and command input adjustment in an outer loop. The reduced dynamic performance requirements in the presence of different actuator faults are accounted for through different performance reduced (degraded) reference models. The degraded steady-state performances are governed by the reduced levels of command input. The reconfigurable controller is designed on-line automatically in an explicit model reference control framework so that the dynamics of the closed-loop system follow that of the performance reduced reference model under each fault condition. The reduced command input level is determined to prevent potential actuator saturation. The proposed method has been evaluated and analyzed using an aircraft example against actuator faults subject to constraints on the magnitude and slew-rate of actuators.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.665-666
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• 2015

In this paper, it is proposed to substitute the tilting operation device of hybrid multi-D.O.F system from three phase SPM to single phase torque actuator. When using tilting operation with three phase SPM which is appropriate for continuous rotary operation, there are disadvantages that electricity availability rate is low and controllability is difficult. On the other hand when using a single phase torque actuator instead of SPM, it is appropriate for sequential tilting, electricity availability rate is high, and it is easy to control. Thus this will have a great influence on the development and practical use of the system. This study designed a single phase torque actuator in consideration of the magnetic saturation. Also, this was verified with comparative analysis with SPM through FEM(finite element method) analysis values of the design model and test values of the manufactured model.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.7
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• pp.1332-1340
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• 1992

A novel approach based on a nonlinear compensator is prposed to prevent 'windup', which is caused by the saturation of the acutator and the integral action of the controller. The anti-windup compensator is located between the conventional linear controller, designed neglecting the saturation, and the actuator. It was proven based on the describing function method that, if the closed loop control systems are stable assuming no saturation, then there may exist a range of compensator gain which prevents any limit-cycle. The computer simulation results show that the compensator proposed in the manuscript can eliminate the limit cycle and improve the transient response.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.1
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• pp.46-55
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• 2006

This paper presents the control method for the hybrid actuator comprising a DC motor and an MR brake. Generally, a DC motor as an active actuator has a small power to weight ratio and goes unstable with higher force control gain due to its saturation limit. In order to cope with this instability and make the transparency higher, this paper proposes a hybrid actuator which consists of a DC motor and an MR brake as a passive actuator and its force control method based on network theory. A DC motor actively produces the output corresponding to the signs of the input currents. On the other hand, an MR brake passively resists against the external load independent of the sign changes of the input currents. This characteristics is widely known as 'passive' This paper suggests a force control method based on passivity concept in network theory for the hybrid actuator and verified its performance and stability through the experiments.

• Smart Structures and Systems
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• v.22 no.1
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• pp.95-103
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• 2018

Active vibration control via inertial mass actuators has been shown as an effective tool to significantly reduce human-induced vertical vibrations, allowing structures to satisfy vibration serviceability limits. However, a lot of practical obstacles have to be solved before experimental implementations. This has motivated simple control techniques, such as direct velocity feedback control (DVFC), which is implemented in practice by integrating the signal of an accelerometer with a band-pass filter working as a lossy integrator. This work provides practical guidelines for the tuning of DVFC considering the damping performance, inertial mass actuator limitations, such as stroke and force saturation, as well as the stability margins of the closed-loop system. Experimental results on a full scale steel-concrete composite structure (behaves similar to a footbridge) with adjustable span are reported to illustrate the main conclusions of this work.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.330-335
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• 1995

The actuator's response delay, disturbance and measurement noise can often cause a significant error in the target tracking of an underwater vehicle. The first purpose of this paper is error analysis about motion of an underwater vehicle when the closed loop system has actuator and disturbance and noise. The underwater vehicle is simulated for cases of various disturbances. The second purpose is robust controller design for the underwater vehicle with parameter uncertainty. So, two robust control methods are applied for the underwater vehicle. One is standard $H_{\infty}$ control, and the other is time-varying sliding mode control with modified saturation function. Suboptimal design parameters for $H_{\infty}$ control, and design parameters for time-varying switching surfaces are provided Simulations for the two controllers are carried out and their performances are analyzed.lyzed.

• Proceedings of the KIEE Conference
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• 1995.07b
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• pp.777-780
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• 1995

Accounting for actuator nonlinearities in control loops has often been perceived as an implementation issue and usually excluded in the design of controllers. Nonlinearities treated in this paper are saturation, and they are modelled as an inequality constraint. The CRHPC(Constrained Receding Horizon Predictive Control) with inequality constraints algorithm is used to handle actuator rate and amplitude limits simultaneously or respectively. Optimum values of future control signals are obtained by quadratic programming. Simulated examples show that predictive control law with inequality constraints offers good performance as compared with input clipping.