• 제목/요약/키워드: Hopping

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An Evolutionary Optimization Approach for Optimal Hopping of Humanoid Robots

  • Hong, Young-Dae
    • Journal of Electrical Engineering and Technology
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    • v.10 no.6
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    • pp.2420-2426
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    • 2015
  • This paper proposes an evolutionary optimization approach for optimal hopping of humanoid robots. In the proposed approach, the hopping trajectory is generated by a central pattern generator (CPG). The CPG is one of the biologically inspired approaches, and it generates rhythmic signals by using neural oscillators. During the hopping motion, the disturbance caused by the ground reaction forces is compensated for by utilizing the sensory feedback in the CPG. Posture control is essential for a stable hopping motion. A posture controller is utilized to maintain the balance of the humanoid robot while hopping. In addition, a compliance controller using a virtual spring-damper model is applied for stable landing. For optimal hopping, the optimization of the hopping motion is formulated as a minimization problem with equality constraints. To solve this problem, two-phase evolutionary programming is employed. The proposed approach is verified through computer simulations using a simulated model of the small-sized humanoid robot platform DARwIn-OP.

Methods of generating Hopping Patterns Based on Permutation Frequency Hopping SSMA System (치환방법을 이용한 주파수 도약 확산 시스템의 주파수 도약 패턴 발생 방법)

  • Choon Sik YIM;Ryuji KOHNO;Hideki IMAI
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.16 no.12
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    • pp.1357-1365
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    • 1991
  • This paper proposes the generation of several classes of frequency hopping patterns. which are derived by permutation, for an asynchronous frequency hopping spread spectrum multiple accecss system (FH/SSMA). The first class of hopping patterns is obtained by using a Latin square. The second class of hopping patterns is derived by generalizing the first class which is designed by using a permutation technique. The third class of hopping patterns is designed by using a rotational base of elements. We evaluate the hit property of the proposed classes of hopping patterns when these patterns are nutually shifted in an FH/SSMA system. Compared to the Reed Slolmon sequences generated by the conventional method, the sequence obtained by the permutation technique can reduce the number of hits among hopping frequencies in asynchronous time/frequency shift.

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A NEW FAMILY OF FREQUENCY HOPPING PATTERNS WITH GOOD HAMMING AUTOCORRELATION AND CROSSCORRELATION (우수한 해밍 자기상관성 및 타 상관성을 갖는 새로운 주파수 도약 패턴 군)

  • 노종선
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.18 no.11
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    • pp.1735-1741
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    • 1993
  • New family of frequency hopping patterns with long period and good Hamming autocorrelation and Hamming crosscorrelation properties which can be used for frequency hopped multiple access communication systems is introduced. Period of frequency hopping patterns is qk-1, the alphabet size of frequency hopping patterns is q, and the size of family of frequency hopping patterns is q, where k is arbitrary integer and q is power of prime number. The maximum value of out-of-Phase Hamming autocorrelation function of any frequency hopping pattern and Hamming crosscorrelation function of any two frequency hopping patterns in the family is qk-1, which corresponds to optima1 Hamming correlation properties. And the average number of hits per q*q square in one frequency hopping pattern and its time shifted version or two frequency hopping patterns in the frequency hopped multiple access communication systems is less than 1.

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A Study of Anti-Jamming Performance using A-NED(Adaptive NED) Algorithm of SFH(Slow Frequency Hopping) Satellite Communication Systems in PBNJ (부분 대역 재밍 환경에서 SFH(Slow Frequency Hopping) 위성 통신 방식을 사용하는 A-NED(Adaptive NED) 알고리즘 항재밍 성능 분석)

  • Kim, Sung-Ho;Shin, Kwan-Ho;Kim, Hee-Jung;Kim, Young-Jae
    • Journal of the Korea Institute of Military Science and Technology
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    • v.13 no.1
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    • pp.30-35
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    • 2010
  • As of today, Frequency Hopping techniques are widely used for over-channel interference and anti-jamming communication systems. In this paper, analysis the performance of robustness on the focus of some general jamming channel. In FH/SS systems, usually SFH(Slow Frequency Hopping) and FFH(Fast Frequency Hopping) are took up on many special communication systems, the SFH, FFH are also combined with a channel diversity algorithm likes NED(Normalized Envelop Detection), EGC(Equal Gain Combines) and Clipped Combines to overcome jammer's attack. This paper propose Adaptive-NED and shows A-NED will be worked well than the others in the some general jamming environments.

An Adaptive Frequency Hopping Method in the Bluetooth Baseband

  • Moon, San-Gook
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • v.9 no.1
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    • pp.785-787
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    • 2005
  • In the Bluetooth specification version 1.0, one specific frequency in one piconet was created depending upon the device clock and the Bluetooth native address at one specific time slot in the frequency hopping method. The basic hopping pattern was arranging the 79 ISM frequency band in pseudo-random fashion. Possible problem is the chance of collision of ownership of one specific frequency by more than 2 wireless devices when they are within the communication-active range. In this paper, we propose the adaptive frequency hopping method in order to resolve the possible problem so that more than 2 wireless devices communicates with their own client devices without being interfered. The proposed method was implemented with HDL later to be synthesized with an automatic EDA synthesizer and verified as well. The implemented adaptive frequency hopping circuit operated normally at 24MHz which will be the target clock frequency of the target Bluetooth device.

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A Study on Interference Cancellation of Adaptive Frequency Hopping System (적응형 주파수도약 시스템의 간섭신호 제거에 관한 연구)

  • Cho, Hyun-Seob
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.10 no.5
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    • pp.396-401
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    • 2017
  • In this paper, we propose a solution for interference with Bluetooth when connecting Bluetooth and other devices. The random frequency hopping technique is a technique of generating a hopping pattern using the entire Bluetooth channel without considering the interference of the wireless LAN. The proposed adaptive frequency hopping technique is a technique for generating a hopping pattern of Bluetooth channel considering periodic carrier sensing of Bluetooth and considering WLAN interference. Simulation results show that the use of adaptive frequency hopping reduces the packet error rate as the Bluetooth carrier sensing interval decreases even in the congestion of WLAN interference. Especially, the frequency hopping technique improves the average packet error rate by about 13% compared to the adaptive frequency hopping technique.

Synthesis Method for Frequency-Hopping Sequences (주파수 도약 수열의 합성 기법)

  • Jo, Dongsik;Chung, Jin-Ho
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2021.10a
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    • pp.472-473
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    • 2021
  • The frequency-hopping sequence is a type of user-specific code that has been used in various ways in military communication, Bluetooth, and ultra-wideband communications. In a practical communication environment, a frequency-hopping sequence with an alphabet and a length suitable for the number of available frequencies and transmission period is required. Therefore, the design of the frequency-hopping sequence having various parameters is a very important problem in frequency-hopping spread-spectrum communication. To this end, this paper explores a method of synthesizing a sequence of a new length through the synthesis of existing frequency-hopping sequences. As a result, it is possible to present the possibility of frequency-hopping sequences applicable to various environments of communications.

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Effects of Preparatory Movements on Performance of Sideward Responsive Propulsion Movement (사전동작이 좌우 반응 추진운동의 수행력에 미치는 영향)

  • Kim, Yong-Woon;Yoon, Te-Jin;Seo, Jung-Suk
    • Korean Journal of Sport Biomechanics
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    • v.15 no.3
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    • pp.9-19
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    • 2005
  • The purpose of this study was to analyze the effects of three different types of preparatory movement(squat, countermovement and hopping) in sideward responsive propulsion movement. 7 healthy subjects performed left and right side movement task by external output signal. 3D kinematics were analyzed The results were followed First, performance time in the countermovement and hopping conditions was shorter(10-20%) than that in the squat condition. The hopping condition that is more related to pre-stretch showed excellent performance. Second, time difference between after turned on the external signal and until take off was the primary factor in performance results among movement conditions. The preparatory phase before the propulsive phase in the squat condition produced more time than that in other conditions. The hopping condition showed the most short time in both the preparatory and the propulsive phase, therefore it was advantage for performance result Third, significant difference was not found in take-off velocity among movement conditions although there was difference of the time required in the propulsive phase. The maximum acceleration in the propulsive phase was larger in order of the hopping. countermovement, and squat condition. The countermovement and hopping conditions showed high take-off velocity although the propulsive phase in those conditions was shorter than that in squat condition. The pre-stretch by preparatory countermovement was considered as the positive factor of producing power in concentric contraction. Fourth, the hopping condition produced large angular velocity of joints. In hopping condition, large amount of moment for rotation movement was revealed in relatively short time and it was considered to cause powerful joint movements. In conclusion, the hopping movement using countermovement is advantage of responsive propulsion movement. It is resulted from short duration until take off and large amount of joint moment and joint power in concentric contraction by pre-stretch.

A Study on Frequency Hopping Signal Detection Using a Polyphase DFT Filterbank (다상 DFT 필터뱅크를 이용한 도약신호 검출에 관한 연구)

  • Kwon, Jeong-A;Lee, Cho-Ho;Jeong, Eui-Rim
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.17 no.4
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    • pp.789-796
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    • 2013
  • It is known that the detection of hopping signals without any information about hopping duration and hopping frequency is rather difficult. This paper considers the blind detection of hopping signal's information such as hopping duration and hopping frequency from the sampled wideband signals. In order to find hopping information from the wideband signals, multiple narrow-band filters are required in general, which leads to huge implementation complexity. Instead, this paper employs the polyphase DFT(discrete Fourier transform) filterbank to reduce the implementation complexity. This paper propose hopping signal detection algorithm from the polyphase DFT filterbank output. Specifically, based on the binary image processing, the proposed algorithm is developed to decrease the memory size and H/W complexity. The performance of the proposed algorithm is evaluated through the computer simulation and FPGA (field programmable gate array) implementation.

Blind Hopping Phase Estimator in Frequency-Hopped FM and BFSK Systems

  • Kim, Myungsup;Seong, Jinsuk;Lee, Seong-Ro
    • ETRI Journal
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    • v.37 no.1
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    • pp.1-10
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    • 2015
  • A blind hopping phase estimator is proposed for the demodulation of received signals in frequency-hopping spread spectrum systems. The received signals are assumed to be bandwidth limited with a shaping filter, modulated as frequency modulation (FM) or binary frequency shift keying (BFSK), and hopped by predetermined random frequency sequences. In the demodulation procedure in this paper, the hopping frequency tracking is accomplished by choosing a frequency component with maximum amplitude after taking a discrete Fourier transform, and the hopping phase estimator performs the conjugated product of two consecutive signals and moving-average filtering. The probability density function and Cramer-Rao low bound (CRLB) of the proposed estimator are evaluated. The proposed scheme not only is very simple to implement but also performs close to the CRLB in demodulating hopped FM/BFSK signals.