• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.20 no.6
• /
• pp.1154-1162
• /
• 2016

This paper proposes a fast-transient digital LDO(Low dropout) regulator with binary-weighted current control technique. Conventional digital LDO takes a long time to stabilize the output voltage, because it controls the amount of current step by step, thus ringing problem is generated. Binary-weighted current control technique rapidly stabilizes output voltage by removing the ringing problem. When output voltage reliably reaches the target voltage, It added the FRZ mode(Freeze) to stop the operation of digital LDO. The proposed fast response digital LDO is used with a slow response DC-DC converter in the system which rapidly changes output voltage. The proposed digital controller circuit area was reduced by 56% compared to conventional bidirectional shift register, and the ripple voltage was reduced by 87%. A chip was implemented with a $0.18{\mu}F$ CMOS process. The settling time is $3.1{\mu}F$ and the voltage ripple is 6.2mV when $1{\mu}F$ output capacitor is used.

• Proceedings of the KIEE Conference
• /
• 1990.11a
• /
• pp.10-14
• /
• 1990

Variable Structure System(VSS) la being extended to a new control system of ac servo machines for its merits of simple mechanism and robustness. This paper has studied about applying VSS to position control for brushless servo motor. But VSS has the chattering problem of control input. This chattering phenomenon cause acoustic noises, torque ripple and increase harmonics of the current. One of the useful way to eliminate this defect of VSS, linearlizing the switching function is discussed here. Though the conventional method of linearizing the switching function diminishes the chattering, it may degrade the robustness of the system. In this paper, new linearized switching function which shows robust performance to the parametric variation and reduces chattering simultaneously is introduced and assured by simulation.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.260-264
• /
• 2005

This paper describes the ultra precise position control of servo motor using sinusoidal encoder based on 'Arcsine Interpolation Method'. First, the paper theoretically analyzes and verify throughout experiments, the relationship between A/D converter input ripple and the total resolution to measure the precise position. Second, this paper presents a way to compensate the total gain and offset error by utilizing a low cost programmable differential amp, by which without any special expensive equipments they are easily on-line tuned and effectively compensated. Lastly, it was compared to servomotor position control characteristics using digital incremental 50,000ppr encoder. The test results show that, with much cheaper sinusoidal encoder, the proposed method exhibits better performance both in position control and ASD applications than the 50,000ppr optical encoder.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.11 no.2
• /
• pp.113-119
• /
• 2006

This paper studies the torque characteristics of CDTP controlled BLDCM with various back-EMF waveforms. We propose a CDTP method to suppress torque pulsation due to commutation time and point. It is adopted to control the BLDCM with real back-EMF waveforms through the Hague's method for minimizing torque ripple. Real back-EMF waveforms are produced with a magnetic fringing factor and crest width of back-EMF. The performance and characteristics of the proposed control method are analyzed by simulation and verified through experimental results.

• Proceedings of the KIPE Conference
• /
• 2004.07b
• /
• pp.985-987
• /
• 2004

Switched Reluctance Motor(SRM) drive system is known to provide good torque characteristics and high efficiency drive. However, speed variation caused by higher torque ripple is one of main drawback. The Phase-Locked Loop (PLL) technique in conjunction with dynamic dwell angle control has good speed regulation characteristics. In this paper, appropriate advance angle control for high efficiency drive and PLL technique for accurate speed control is proposed. A TMS320F240 DSP is used to realize this drive system. Test results show that the system has good dynamic and precise speed control ability as well as high efficiency.

• Proceedings of the KIPE Conference
• /
• 1998.07a
• /
• pp.447-454
• /
• 1998

This paper describes a modeling and current control techniques of Distribution static condenser (D-STATCON) for power factor compensation. The current control is based on the predictive and the space vector PWM scheme. The predictive current controlled PWM D-STATCON can maintain its performance with power factor compensation and fixed switching frequency. By using the space vector control low ripple and offset in the current and the voltage as well as fast dynamic responses are achieved with a small DC link capacitance employed.

• Proceedings of the KIPE Conference
• /
• 1998.10a
• /
• pp.464-469
• /
• 1998

In the conventional wire feeder drives of welding machine, one thyristor or MOSFET device was used for half-wave phase control circuit and direct EMF measurement was used for sensing the wire feed rate. But the method using one switching device has poor response for sudden disturbance and it has latent speed ripple. It can affect some welding performance such as spatter generation and irregular bead formming. Therefore, the welding performance using full-bridge PWM speed control scheme was compared with conventional driving scheme was compared with conventional driving scheme and experimented in this paper. The results of experiment confirm the posibility of welding performance improvement by proposed constant speed control scheme in wire feeding drive of welding machine.

• Proceedings of the KIPE Conference
• /
• 1998.07a
• /
• pp.212-216
• /
• 1998

For a Switched Reluctance Motor(SRM) drive, the important things are 1) reducing torque ripple, 2) improving efficiency, 3) sensorless speed control, 4) accurate position. The position information impotant for the efficiency and smoothness drives. Since SRMs characteristics are nonlinear. It is difficult to estimated phase current in saturation region. This paper describes a method for indirect sensing of the rotor position in SRM which use both voltage and current. The method obtains rotor position by using unconducting phase. The information about the rotor position is achieved by differentiating the unconducting phase current or the voltage gradient. And then, this paper presents a torque control with indirect rotor position detection methods. This torque control is achieved by developing a detailed nonlinear model of the motor.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.05a
• /
• pp.153-156
• /
• 2006

The vibration isolation system is a system that attenuates the vibration transmitted from surroundings by using external energy supply like electricity and feedback and/or feedforward functions. Such a system needs stiff structure to make precise positioning without ripple within a certain bandwidth. So, a horizontal and rotary arrangement of the actuation module is suggested by using lever linkage. Modeling and kinematic formulation are completed and system identification is accomplished to tune the design variables accurately. The vibration isolation control is performed by mu-synthesis with the uncertainties in design variables. Low frequency signal enhancement circuit and saturation proof integration algorithm are devised to use seismic sensors for displacement control. This overall system shows good disturbance rejection performance.

• Journal of Institute of Control, Robotics and Systems
• /
• v.13 no.6
• /
• pp.589-595
• /
• 2007

This paper presents a new method on controller design of brushless dc motors. In such drives the current ripples are generated by motor inductance in stator windings and the back EMF. To suppress the current ripples the current controller is generally used. To minimize the size and the cost of the drives it is desirable to control motors without the current controller and the current sensing circuits. To estimate the motor CUlTent it is modeled by a neural network that is contigured as an output-error dynamic system. The identified model is essentially a one step ahead prediction structure in which past inputs and outputs are used to calculate the current output. Using the model, a state feedback controller to compensate the effects of disturbance has been designed. The controller is implemented by a 16-bit microprocessor and the effectiveness of the proposed control method is verified through experiments.