• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.59 no.4
• /
• pp.401-404
• /
• 2010

In multibit Sigma-Delta Modulator, DWA(Data Weighted Averaging) among the DEM(Dynamic Element Matching) techniques was widely used to get rid of non-linearity that caused by mismatching of unit capacitor in feedback DAC path. this paper proposed the improved DWA architecture by adjusting clock timing of the existing DWA architecture. 2n Register block used for output was replaced with 2n S-R latch block. As a result of this, MOS Tr. can be reduced and extra clock can also be removed. Moreover, two n-bit Register block used to delay n-bit data code is decreased to one n-bit Register. In order to confirm characteristics, DWA for the 3-bit output with the proposed DWA architecture was designed on 0.18um process under 1.8V supply. Compared with the existing architecture. It was able to reduce the number of 222 MOS Tr.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.57 no.6
• /
• pp.1081-1086
• /
• 2008

This paper presents the $3^{rd}$ 4bit sigma delta modulator with the block and timing diagrams of DWA(Data Weighted Averaging) to optimize a operating time. In the modulator, the proposed DWA structure has a stable operation and timing margin so as to remove three latches and another clock. Because the modulator with proposed DWA structure improve timing margin about 23%. It can increase sampling frequency up to 244MHz. Through the MATLAB modeling, the optimized coefficients are obtained to design the modulator. The fully differential SC integrators, DAC, switch, quantizer, and DWA are designed by considering the nonideal characteristics. The designed $3^{rd}$ order 4bit modulator has a power consumption of 40mW and SNR(signal to noise ratio) of 77.2dB under 1.2V supply and 64MHz sampling frequency.

• Journal of Institute of Control, Robotics and Systems
• /
• v.13 no.7
• /
• pp.624-630
• /
• 2007

The dynamic window approach(DWA) is a well known technique for reactive collision avoidance. It shows safe and efficient performance in real-world experiments. However, a robot can get stuck in local minima because no information about the connectivity of the free space is used to determine the motion. The global DWA can solve this problem of local minima by adding a navigation function. Even with the global DWA, it is still difficult for a robot to execute an abrupt change in its direction, for example, entering from the corridor to a doorway. This paper proposes a modified global DWA using the included angles of waypoints extracted from an optimal path. This scheme enables the robot to decelerate in advance before turning into the doorway. Therefore the robot can reach the goal position more safely and efficiently at high speeds.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.48 no.5
• /
• pp.18-24
• /
• 2011

In multibit Sigma-Delta Modulator, one of the DEM(Dynamic Element Matching) techniques which is DWA(Data Weighted Averaging) is widely used to get rid of non-linearity caused by mismatching of capacitor that is unit element of feedback DAC. In this paper, by adjusting clock timing used in existing DWA architecture, 2n Register block used for output was replaced with 2n S-R latch block. As a result of this, MOS Tr. can be reduced and extra clock can also be removed. Moreover, two n-bit Register block used to delay n-bit data code is decreased to one n-bit Register. After designing the 3rd 3-bit SC(Switched Capacitor) Sigma-Delta Modulator by using the proposed DWA architecture, 0.1% of mismatching into unit element in input frequency 20 kHz and sampling frequency 2.56 MHz. As a consequence of the simulation, It was able to get the same resolution as the existing architecture and was able to reduce the number of MOS Tr. by 222.

• Journal of the Korean association of regional geographers
• /
• v.3 no.1
• /
• pp.1-12
• /
• 1997

The climatic characteristics of Korea are analized with the data observed from 1972 to 1995 in 66 stations, using the climatic year method expressed by the $K{\ddot{o}}ppen's$ system of climatic classification. The climate of Korea is composed of the six climatic year types : Cfa, Cwa, Cwb, Dfa, Dwa and Dwb type. The Cwa and Dwa type occupy 95% occurrence frequency. The Cwa climatic year type predominates in the greater part of the Southern Area, the east slopes of the Taebaek Range and Cheju-do, the Dwa type does in Yongso Area and the northeastern part of Kyonggi Province. and the Cfa type does in Ullung-do. Such dominant climatic year regions become the stable climatic regions, while the regions where the various climatic types appear become the unstable climatic regions which are distributed in the northern part of the Southern Area and in the southern part of the Central Area owing to the shifts of the border between C type and D type. The border between C and D type is located in the Central Inland Area in the first half of the 1990's which the Cwa type predominates most. On the other hand the border is located in the middle part of the Southern Area in the first half of the 1980's which the Dwa type prevails most. Therefore the extents of the climatic year regions vary each year. In the interannual change of the main climatic year types, the Cwa type shows the increasing trend, while the Cfa and Dwa type reflets the decreasing tendency. The extending trend of the Cwa climatic year region appears during the period of the first half of the 1970's and the period between the latter half of the 1980's and the first half of the 1990's centering around the Southern Area. The Dwa climatic year region which was predominant in the Central Area in the first half of the 1980's has been reduced up till the recent years.

• IEMEK Journal of Embedded Systems and Applications
• /
• v.12 no.5
• /
• pp.295-301
• /
• 2017

Recently, autonomous navigation technology, obstacle recognition, and obstacle collision avoidance technology are actively being developed for an unmanned surface vehicle (USV). The path to move from the current location to the destination should be planned, in order for an USV to autonomously operate safely to its destination. The dynamic window approach (DWA) is a well-known navigation scheme as a local path planning. The DWA algorithm derives the linear velocity and angular velocity by evaluating the destination direction, velocity, and distance from the obstacle. However, because DWA algorithm does not consider tracking the path, when using only the DWA algorithm, the ship may navigate away from the path line after avoiding obstacles. In this paper, we propose an improved DWA algorithm that can follow path line. And we implemented the simulation and compared the existing DWA algorithm with the improved DWA algorithm proposed in this paper. As a result, it is confirmed that the proposed DWA algorithm follows the path line better.

• Proceedings of the KIEE Conference
• /
• 2003.11b
• /
• pp.75-78
• /
• 2003

In this paper, a second-order 3-bit DSM using DWA(Data Weighted Averaging) algorithm is designed for bluetooth Zero-IF Receiver. The designed circuit has two integrators using a designed OTA, nonoverlapping two-phase clerk generator, 3-bit A/D converter, DWA algorithm and 3-bit D/A converter An ideal model of second-order lowpass DSM with a 3-bit quantizer was configured by using MATLAB, and each coefficients and design specification of each blocks were determined to have 10-bit resolution in 1MHz channel bandwidth. The designed second-order 3-blt lowpass DSM has maximum SNR of 74dB and power consumption is 50mW at 3.3V.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.2
• /
• pp.389-397
• /
• 2011

The global dynamic window approach (DWA) is widely used to generate the shortest path of mobile robots considering obstacles and kinematic constraints. However, the dynamic constraints of robots should be considered to generate the minimum-time path. We propose a modified global DWA considering the dynamic constraints of robots. The reference path is generated using A* algorithm and smoothed by cardinal spline function. The trajectory is then generated to follows the reference path in the minimum time considering the robot dynamics. Finally, the local path is generated using the dynamic window which includes additional terms of speed and orientation. Simulation and experimental results are presented to verify the performance of the proposed method.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.41 no.9
• /
• pp.107-114
• /
• 2004

This paper presents block and timing diagrams of the DWA(Data Weighted Averaging) to optimize a feedback time delay of the sigma-delta modulator. Through the MATLAB modeling, the optimized coefficients of the integrators are obtained to design the modulator. The fully differential SC integrators, feedback DAC, 9-level quantizer, and DWA are designed by considering the nonideal characteristics of the modulator. The designed third-order multibit modulator is fabricated in a 0.35${\mu}{\textrm}{m}$ CMOS process. The modulator achieves 75dB signal-to-noise ratio and 74dB dynamic range at 1.2Vp-p 825kHz input signal and 52.8MHE sampling frequency.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.24 no.1
• /
• pp.61-69
• /
• 2021

Recently, autonomous navigation technology is actively being developed due to the increasing demand of an unmanned surface vehicle(USV). Local planning is essential for the USV to safely reach its destination along paths. the dynamic window approach(DWA) algorithm is a well-known navigation scheme as a local path planning. However, the existing DWA algorithm does not consider path line tracking, and the fixed weight coefficient of the evaluation function, which is a core part, cannot provide flexible path planning for all situations. Therefore, in this paper, we propose a new DWA algorithm that can follow path lines in all situations. Fixed weight coefficients were trained using reinforcement learning(RL) which has been actively studied recently. We implemented the simulation and compared the existing DWA algorithm with the DWA algorithm proposed in this paper. As a result, we confirmed the effectiveness of the proposed algorithm.