• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.22 no.1
• /
• pp.1-6
• /
• 2014

In this paper, controller propose to prevent compressor surge and improve the transient response of the fuel flow control system of turbojet engine. Turbojet engine controller is designed by applying Artificial Neural Network PID control algorithm and make an inference by applying Levenberg-Marquartdt Error Back Propagation Algorithm. Artificial Neural Network inference results are used as the fuel flow control inputs to prevent compressor surge and flame-out for turbojet engine for UAV. High Gain Observer is used to estimate to compressor rotation speed of turbojet engine. Using MATLAB to perform computer simulations verified the performance of the proposed controller. Response characteristics pursuant to the gain were analyzed by simulation.

• Journal of the Korean Society for Precision Engineering
• /
• v.19 no.11
• /
• pp.37-45
• /
• 2002

This paper presents the field-dependent Bingham characteristics and damping force control of an electro-rheological (ER) fluid under squeeze mode operation. The squeeze force of the ER fluid due to the imposed electric field is analyzed and an appropriate size of the disk-type electrode is devised. On the basis of the theoretical model of the ER fluid under squeeze mode operation, the yield stress and response speed of the ER fluid are distilled from the time responses of squeeze force to the step electric potentials. Measured squeeze forces under various excitation conditions are compared with the predicted ones from Bingham model and time constant obtained at the transient response test. In addition, the controllability of the field-dependent damping force of the ER fluid under squeeze mode is experimentally demonstrated by implementing simple PID controller.

• 제어로봇시스템학회:학술대회논문집
• /
• 1990.10a
• /
• pp.145-148
• /
• 1990

In this paper, the problem of designing a feedback controller for a robotic manipulator, which is activated by a D.C. motor through a gear train and a flexible shaft or chain, is considered. When the response of the closed loop control system is relatively slow, a satisfactory controller may be designed as a PID controller. As the speed of the control system increases, however, the spring effect of the linkage becomes profound, and as a result, the transient response exhibits a substantial oscillation. To eliminate this oscillation, it is necessary to design the controller based on at least a fourth order system model. This, in turn, requires the feedback of the entire state variables. In practice, however, only the position of the manipulator and the velocity of the motor are readily measurable. The state variable reconstruction method or a state observer cannot be used because of the system nonlinearities such as the Coulomb frictions. In this study, an alternative controller, which is based on delayed feedback of the output variable only, is proposed, and a successful delayed feedback controller is designed and implemented on an actual experimental manipulator.

• Journal of Power Electronics
• /
• v.18 no.3
• /
• pp.736-745
• /
• 2018

This paper presents an extended state observer (ESO) based direct torque control (DTC) for use in induction motor systems to handle the issues of time delays, load torque disturbances and parameter uncertainties. Direct torque control offers an excellent torque response and it does not require a proportion integration (PI) controller in the current loop. However, a PI controller is still adopted in the outer speed loop to generate the torque reference value, which is a slow method. An ESO based compound control scheme is proposed to improve the response rate and accuracy of the torque reference signal, especially when load torque is injected. In addition, the time delay problem is analyzed and compensated for in this paper to reduce torque ripples. The proposed disturbance compensation technique based direct control scheme is shown to have good performance both in the transient and stable states via simulations and experimental results.

• Proceedings of the KIEE Conference
• /
• 1995.07b
• /
• pp.751-753
• /
• 1995

Practical controllers of industrial systems are usually designed and realized in continuous time domain. However, due to the programmable and flexible nature of digital computers and the speed and stability superioity of digital components over analog ones, it seems more effective to adapt digital controllers. When an existing analog controller performs satisfactory, it is often advantageous to use the digital redesign techinque to obtain an equlivalent digital controller which substitutes the analog one. One method of the digital redesign is to use a periodic gain. This method gives a riffle effect on the steady state response, although it's transient response is satisfactory. This paper suggests a method which eliminates or deminishes periodic ripples generated by the periodic function.

• Journal of Electrical Engineering and Technology
• /
• v.2 no.2
• /
• pp.263-266
• /
• 2007

We report a nickel optical MEMS switch, being able to rotate through a large angle and to accommodate multiple channels. The proposed optical switch consists of a thin nickel mirror and two torsion springs supporting the mirror. The torsion springs are designed using a finite element method (FEM) such that plastic deformation of the thin nickel is avoided during the large torsion actuation. For switching speed improvement, transient vibration of the released mirror is suppressed by optimizing the mirror design and a fast switching response of $200\;{\mu}s\;(pull-down)/300\;{\mu}s\;(pull-up)$ is demonstrated.

• International Journal of Automotive Technology
• /
• v.6 no.2
• /
• pp.149-159
• /
• 2005

A full nonlinear finite element P185/70Rl4 passenger car radial-ply tire model was developed and run on a 1.7-meter-diameter spinning test drum/cleat model at a constant speed of 50 km/h in order to investigate the tire transient response characteristics, i.e. the tire in-plane free vibration modes transmissibility. The virtual tire/drum finite element model was constructed and tested using the nonlinear finite element analysis software, PAM-SHOCK, a nonlinear finite element analysis code. The tire model was constructed in extreme detail with three-dimensional solid, layered membrane, and beam finite elements, incorporating over 18,000 nodes and 24 different types of materials. The reaction forces of the tire axle in vertical (Z axis) and longitudinal (X axis) directions were recorded when the tire rolled over a cleat on the drum, and then the FFT algorithm was applied to examine the transient response information in the frequency domain. The result showed that this PI 85/70Rl4 tire has clear peaks of 84 and 45 Hz transmissibility in the vertical and longitudinal directions. This result was validated against more than 10 previous studies by either theoretical or experimental approaches and showed excellent agreement. The tire's post-impact response was also investigated to verify the numerical convergence and computational stability of this FEA tire model and simulation strategy, the extraordinarily stable scenario was confirmed. The tire in-plane free vibration modes transmissibility was successfully detected. This approach was never before attempted in investigations of tire in-plane free vibration modes transmission phenomena; this work is believed to be the first of its kind.

• Nuclear Engineering and Technology
• /
• v.56 no.5
• /
• pp.1584-1602
• /
• 2024

It is vital to output the required electrical power following various task requirements when the space reactor power supply is operating in orbit. The dynamic performance of the closed Brayton cycle thermoelectric conversion system is initially studied and analyzed. Based on this, a load tracking power regulation method is developed for the liquid metal cooled space reactor power system, which takes into account the inlet temperature of the lithium on the hot side of the intermediate heat exchanger, the filling quantity of helium and xenon, and the input amount of the heat pipe radiator module. After comparing several methods, a power regulation method with fast response speed and strong system stability is obtained. Under various changes in power output, the dynamic response characteristics of the ultra-small liquid metal lithium-cooled space reactor concept scheme are analyzed. The transient operation process of 70 % load power shows that core power variation is within 30 % and core coolant temperature can operate at the set safety temperature. The second loop's helium-xenon working fluid has a 65K temperature change range and a 25 % filling quantity. The lithium at the radiator loop outlet changes by less than ±7 K, and the system's main key parameters change as expected, indicating safety. The core system uses less power during 30 % load power transient operation. According to the response characteristics of various system parameters, under low power operation conditions, the lithium working fluid temperature of the radiator circuit and the high-temperature heat pipe operation temperature are limiting conditions for low-power operation, and multiple system parameters must be coordinated to ensure that the radiator system does not condense the lithium working fluid and the heat pipe.

• Journal of Korean Society of Transportation
• /
• v.29 no.3
• /
• pp.115-122
• /
• 2011

This paper investigates the accuracy of the vehicle pre-braking speed estimated based upon measured skidding distance. Driver ordinarily takes sudden braking when urgent situation is developed in the front or when the driver is involved in an unexpected situation, and the driver may be inflicted upon an accident depending on the required stopping distance. Among factors influencing the stopping distance of vehicle such as recognition response time of driver, performance of vehicle's braking device, and state of road surface etc, pre-braking speed is seemingly the most important influencing factor. Currently, in the investigating section of traffic accidents, the state of overspeed is determined by the pre-skidding speed calculated based on the length of skid mark. In order to identify the accurate cause of the accident, it is strongly recommended that estimation of pre-braking speed should be estimated taking into account speed reduction during transient time. In this study, we propose a method for estimating more accurate exact speed information of vehicle at the time of traffic accident. The outcomes from this study potentially help better understanding of the characteristics of vehicle for traffic safety in the future.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.41 no.3
• /
• pp.39-46
• /
• 2004

This paper is proposed adaptive fuzzy-neural network(FNN) controller for the speed control of interior permanent magnet synchronous motor(IPMSM) drive. The design of this algorithm based on FNN controller that is implemented by using fuzzy control and neural network. This controller uses fuzzy rule as training patterns of a neural network. Also, this controller uses the back-propagation method to adjust the weights among the neurons of neural network in order to minimize the error between the command output and actual output. A model reference adaptive scheme is proposed in which the adaptation mechanism is executed by fuzzy logic based on the error and change of error measured between the motor speed and output of a reference model. The control performance of the adaptive FNN controller is evaluated by analysis for various operating conditions. The results of analysis prove that the proposed control system has strongly high performance and robustness in parameter variation, steady-state accuracy and transient response.