• Journal of Institute of Control, Robotics and Systems
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• v.10 no.11
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• pp.1028-1036
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• 2004

Ultrasonic sensors are widely used in mobile robot applications to recognize external environments by virtue that they are cheap, easy to use, and robust under varying lighting conditions. In most cases, a single ultrasonic sensor is used to measure the distance to an object based on time-of-flight (TOF) information, whereas multiple sensors are used to recognize the shape of an object, such as a comer, plane, or edge. However, the conventional sequential driving technique involves a long measurement time. This problem can be resolved by pulse coding of ultrasonic signals, which allows multi-sensors to be emitted simultaneously and adjacent objects to be distinguished. Accordingly, this paper presents a new simultaneous coded driving system for an ultrasonic sensor array for object recognition in autonomous mobile robots. The proposed system is designed and implemented. A micro-controller unit is implemented using a DSP, Polaroid 6500 ranging modules are modified for firing the coded signals, and a 5-channel coded signal generating board is made using a FPGA. To verify the proposed method, experiments were conducted in an environment with overlapping signals, and the flight distances fur each sensor were obtained from the received overlapping signals using correlations and conversion to a bipolar PCM-NRZ signal.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.2
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• pp.164-170
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• 2013

The latest vehicle yields a superior safety and reduction of driving burden by monitoring the driving state of vehicle and its environment with various sensors. To detect other vehicles and objects of the rear left and right-side blind spot area of driver, provide the information about a existence of objects inside the blind spot, and give a signal to avoid collision, this study proposes the intelligent outside rear-view mirror system. This study proposes SILS system with PreScan and Matlab/Simulink to verify practical applicability of developed BSDS. PreScan yields realistic driving environments and road conditions and vehicle model dynamics and collision warning is controlled by Matlab/Simulink.

• International Journal of Automotive Technology
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• v.8 no.2
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• pp.249-258
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• 2007

This paper proposes a method that can be used for the resistance estimation of a PWM (Pulse Width Modulation)-driven solenoid. By using estimated solenoid resistance, the PWM duty ratio was compensated to be proportional to the solenoid current. The proposed method was developed for use with EHB (Electro-Hydraulic Braking) systems, which are essential features of the regenerative braking system of many electric vehicles. Because the HU (Hydraulic Unit) of most EHB systems performs not only ABS/TCS/ESP (Electronic Stability Program) functions but also service braking function, the possible duration of continuous solenoid driving is so long that the generated heat can drastically change the level of solenoid resistance. The current model of the PWM-driven solenoid is further developed in this paper; from this a new resistance equation is derived. This resistance equation is solved by using an iterative method known as the FPT (fixed point theorem). Furthermore, by taking the average of the resistance estimates, it was possible to successfully eliminate the effect of measurement noise factors. Simulation results showed that the proposed method contained a sufficient pass-band in the frequency response. Experimental results also showed that adaptive solenoid driving which incorporates resistance estimations is able to maintain a linear relationship between the PWM duty ratio and the solenoid current in spite of a wide variety of ambient temperatures and continuous driving.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.9
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• pp.129-134
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• 2016

This paper studies the high frequency PWM (pulse width modulation) driving technique to increase an optical efficiency and to prevent an optical color quenching of blue laser for head up display on vehicles using digital micro mirror device (DMD) panel and yellow phosphor wheel. The proposed approach adaptively drives the current pulse width modulated signals of high optical power of blue laser to increase the lifetime and to decrease the stem temperature of laser. This method stabilizes the temperature of laser according to the driving environment and the forward current capacity. By the proposed method, the brightness of blue laser is improved by about 37% compared to the continuous waveform current driving method.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.582-587
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• 2004

Ultrasonic sensors are widely used in mobile robot applications to recognize external environments, because they are cheap, easy to use, and robust under varying lighting conditions. However, the recognition of objects using a ultrasonic sensor is not so easy due to its characteristics such as narrow beam width and no reflected signal from a inclined object. As one of the alternatives to resolve these problems, use of multiple sensors has been studied. A sequential driving system needs a long measurement time and does not take advantage of multiple sensors. Simultaneous and pulse coding driving system of ultrasonic sensor array cannot measure short distance as the length of the code becomes long. This problem can be resolved by multi-frequency driving of ultrasonic sensors, which allows multi-sensors to be fired simultaneously and adjacent objects to be distinguished. Accordingly, this paper presents a simultaneous and multi-frequency driving system for an ultrasonic sensor array for object recognition. The proposed system is designed and implemented using a DSP and FPGA. A micro-controller board is made using a DSP, Polaroid 6500 ranging modules are modified for firing the multi-frequency signals, and a 5-channel frequency modulated signal generating board is made using a FPGA. To verify the proposed method, experiments were conducted in an environment with overlapping signals, and the flight distances for each sensor were obtained from filtering of the received overlapping signals and calculation of the time-of-flights.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.7
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• pp.13-19
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• 2007

This study relates to a new high-speed drive method for the full-HD PDP with 1080 horizontal scanning lines. The characteristics of the new drive method is evaluated considering the characteristics of the display discharge by the high-speed addressing. In this drive method, if the width of the address pulse narrows, the relati0[V]e discharge strength and the discharge time lag of the first display discharge are received the influence of it. Though the change in the applied position of the address pulse is unrelated to the discharge strength, it influences at the discharge time lag. However, the stable display discharges can be induced regardless of the address pulse position and width if the address pulse position is within [$6{\mu}s$] and the width is up to [$0.7{\mu}s$]. From the experiments, it has been understood that the high-speed drive technique with the address pulse of narrow width is sensitively influenced by the space charge because of the insufficiency of wall charge.

• Proceedings of the KIEE Conference
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• 2008.04c
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• pp.134-136
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• 2008

In recent years, the switched reluctance motor have been used many industrial application because of its cost advantage. SRM drivers are accomplished by switching the phase currents on and off synchronously with the rotor position which is fed back to the controller by position may deteriorate in harsh environments and increase the size and cost of the SRM drive system. This paper proposes a position sensorless method that is based on impressed pulse voltage using impressed at unenergised phases to estimate the rotor position. The current value by impressed pulse voltage compare with the threshold value. The rotor position can be estimated by observing the current value. Finally, simulation results compare with the sensor type SRM and confirm the proposed method to be useful.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.261-265
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• 2001

In this paper, a current-source type parallel indudor compensated load resonant high-frequency soft switching inverter using IGBTs for driving the newly-produced silent discharge type ozone generating tube and excimer lamp for UV generation which incorporate a single switched capacitor resonant snubber between the port in DC busline side is presented, together with its pulse modulated unique output power regulation characteristics.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.3
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• pp.485-501
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• 1997

Pressure control is possible driving a simple ON/OFF 3-way valve of hydraulic servo system by pulse width modulation signal. But the pressure varies according to the duty ratio and carrier frequency and repeated on-off action induces pressure fluctuation. So equations for mean pressure and ripple amplitude are theoretically derived as a function of on/off time, the system parameters which decide the pressure characteristics are arranged and they are verified by experimental study. As the result selection criteria for the major design parameters are established and the basic strategy to suppress the unnecessary fluctuation can be provided for a hydraulic pressure control system using these type of valves.

• Journal of the Optical Society of Korea
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• v.14 no.2
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• pp.137-141
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• 2010

We report, for the first time to our knowledge, observation of polarization bistability from 1.55-${\mu}m$ wavelength single-mode VCSELs of a conventional cylinder-shape under control of their driving current, and demonstration of all-optical flip-flop (AOFF) operations based on the bistability with optical set and reset pulse injection at a 50 MHz switching frequency. The injection pulse energy was less than 14 fJ. The average on-off contrast ratio of the flip-flopped signals was about 7 dB. These properties of the VCSELs will be potentially useful for future high-speed all-optical signal processing applications.