• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1925-1930
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• 2010

For high-speed/high-accuracy position control of a gantry-moving-type linear motor, we propose a nonlinear adaptive controller including a synchronization algorithm. Linear motors are easily affected by force ripple, friction, and parameter variations because there is no mechanical transmission to reduce the effects of model uncertainties and external disturbances. Synchronization error is also caused by skew motion, model uncertainties, and force disturbance on each axis. Nonlinear effects such as friction and ripple force are estimated and compensated for. The synchronization algorithm is used to reduce the synchronous error of the two side pillars. The performance of the controller is evaluated via computer simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.3
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• pp.506-515
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• 2015

In this paper, we propose a group playback synchronization method using adaptive synchronization delay time by the bit rate of media to synchronize a play position of streaming media between mobile smart devices. This method consists of streaming server-side and client-side synchronization algorithms based on synchronization delay time which includes connection time, control packet transmission time, streaming data buffering time, and synchronization processing time. We implement the Android media player application with synchronization support using the proposed algorithms and present the result of performance evaluation.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.6
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• pp.527-534
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• 2016

The non-rail mobile rack, which is used for cargo storage, can improve the storage capacities of logistics centers. Furthermore, it has the advantage that it can be used in traditional logistics centers without making any changes or renovation, such as installing rails. However, when the rack is operated by separated drive actuators mounted on the left and the right wheels, precise position control of the wheels is necessary even if the unbalanced cargo weight on the rack would affect the control. Therefore, internal synchronization control for position tracking between the left and right wheels on the non-rail mobile rack is necessary in this study. In addition, external synchronization control for realizing the same straight movements between mobile racks is necessary. For the internal and the external synchronization control, we propose a synchronization control algorithm based on the repetitive control theory. An internal synchronization control algorithm with repetitive control theory requires the application of the robust servo control method owing to parameter variations. In this case, we can set up the gains for the robust servo control system by considering the cargo variations on the mobile rack. Furthermore, for developing the external synchronization control algorithm, we use a double repetitive control system to perform synchronization control between mobile racks. The efficiency of the proposed control algorithm will be verified by simulation and experimental results. The proposed algorithm can be easily applied in the industry.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.487-489
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• 2005

This paper proposes a symbol timing recovery method that is simple in structure and can provide high speed symbol synchronization. Transmitter and receiver are not synchronized in communication systems using digital modulation. Receiver should search the timing variation of transmitter continuously. The proposed timing recovery method searches sample position by comparing previous sample value with next sample value. This method can be applied to digital and optical transceivers with high data rate.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1866-1870
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• 2005

Typical small desktop robots have limied application due to their intrinsic feaures like friction, backlash, etc. However, a newly developed small gantry desktop robot needs smaller footprint and shows better performance in position accuracy, velocity, and acceleration. In order to achieve such results, synchronization control of two axes, position compensation methods in plane are suggested.

• KIPS Transactions on Computer and Communication Systems
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• v.8 no.8
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• pp.191-200
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• 2019

In an Ad-hoc network, a method of time synchronizing all the nodes in a network centering on one reference node can be used. A representative algorithm based on a reference node is Flooding Time Synchronization Protocol (FTSP). In the process of sending and receiving messages, predictable and unpredictable delays occur, which should be removed because it hinders accurate time synchronization. In multi-hop communications, hop delays occur when a packet traverses a number of hops. These hop delays significantly degrade the synchronization performance among nodes. Therefore, we need to find a method to reduce these hop delays and increase synchronization performance. In the FTSP scheme, hop delays can be greatly increased depending on the position of a reference node. In addition, in FTSP, a node with the smallest node ID is elected as a reference node, hence, the position of a reference node is actually arbitrarily determined. In this paper, we propose an optimal reference node election algorithm to reduce hop delays, and compare the performance of the proposed scheme with FTSP using the network simulator OPNET. In addition, we verify that the proposed scheme has an improved synchronization performance, which is robust to topology changes.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.2
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• pp.206-215
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• 2013

In this paper, a synchronization control technique of dual-servo motor driven press system is proposed. An independent cascade PID control technique has been applied to the conventional press system for advancement of control stability. However, it is not easy to reduce synchronous error using the independent cascade PID control technique when some different load disturbances are involved in each motor. The eccentric error of the slide caused by the problem degrade the control performance of the BDC(Bottom Dead Center). In order to achieve reduction of the synchronous error between two servo motors and accurate position control simultaneously, a new control scheme comprised with cascade PID control loop and cross-coupling loop is proposed. In simulation using Matlab SIMULINK, the AC servo system is designed. The control performance of proposed technique is compared with conventional control technique to the model of AC servo system. Also, the sub-scale model of dual-servo motor driven press system which can replicate the slide motion is constructed for experimental verification for the performance of the proposed control technique. The cross-coupling control technique reveals more precise and stable performances in the position and synchronization controls.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.6
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• pp.27-32
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• 2008

Impulse Radio Ultra Wide Band (IR-UWB) system can be used to wireless position location system because of its unique very short pulse in the order of nanosecond. A few algorithms have been proposed to calculate location of sensors or tags. In this paper, we compare these algorithms and propose 'TDoA with wireless synchronization' as practical solution. Earlier algorithms need special logic to fix the duration to receive and send pulse or assume synchronization with wire. In proposed method, beacons synchronize each other using impulse and nodes can be made simple and cheap. We evaluated the performance and it shows 50% improved accuracy at the error range of 50cm.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1858-1862
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• 2005

Stepping motor normally operates without feedback and may loss the synchronization. This problem can be prevented by using positional feedback. This paper introduces one method for closed loop control of stepping motor and a method for combining full-step control and micro-step control. This combination controlling apparatus can perform position control with high accuracy in a high speed, so that it will not suffer from vibration (or hunting) problem when stopping motor. Controlling apparatus contains a position counter block for detecting rotor position of stepping motor, a driving block for supplying current to windings of stepping motor, a control block for comparing output signal of position counter block with command position (desired position) and outputting current command signal based on deviation between current position and command position of rotor. To output current command signal, the control block refers to a sine wave data table. This table contains value of duty cycle of Pulse Width Modulation signal. As the second object of this paper, the process of building this data table is also presented.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.5
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• pp.486-496
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• 2013

Time synchronization in underwater environment is challenging due to high propagation delay and mobility of sensor nodes. Previous researches do not consider practical issues affecting on the accuracy of time synchronization such as high-channel access delay and relative position between sensor nodes. Also, those protocols using bidirectional message exchange shorten the network lifetime and decrease the network throughput because numerous transmission, reception and unnecessary overhearing can be occurred. Therefore, in our research, we suggest enhanced time synchronization based on features of underwater environment. It controls the instant of transmission by exploiting the feature of an oceanic movement and node deployment. Moreover, the protocol uses more accurate time information by removing channel access delay from the timestamp. The proposed scheme is also practical on the underwater sensor network requiring low-power consumption because the scheme conducts time-synchronization with smaller transmission and reception compared with previous works. Finally, simulation results show that the proposed protocol deceases time error by 2.5ms and 0.56ms compared with TSHL and MU-Sync respectively, reducing energy consumption by 68.4%.