Milli-scale crawling robots have been widely studied due to their maneuverability in confined spaces. For successful crawling, the crawling robots basically required to fulfill alternating gait with elliptical foot trajectory. The alternating gait with elliptical foot trajectory normally generates both forward and upward motion. The upward motion makes the aerial phase and during the aerial phase, the forward motion enables the crawling robots to proceed. This simultaneous forward and upward motion finally results in fast crawling speed. In this paper, we propose a novel alternating mechanism to make a crab-inspired eight-legged crawling robot. The key design strategy is an alternating mechanism based on double four-bar linkages. Crab-like robots normally employs gear-chain drive to make the opposite phase between neighboring legs. To use the gear-chain drive to this milli-scale robot system, however, is not easy because of heavy weight and mechanism complexity. To solve the issue, the double-four bar linkages has been invented to generate the oaring motion for transmitting the equal motion in the opposite phase. Thanks to the proposed mechanism, the robot crawls just like the real crab with the crawling speed of 0.57 m/s.

Abstract
1. 서 론
2. 디자인
    2.1 다리 디자인
    2.2 동력전달 디자인
    2.3 제작
3. 다리 경로 분석
4. 실험 및 결과
    4.1 발 궤적 분석
    4.2 주행 테스트
    4.3 다리 궤적 모양에 관한 고찰
5. 결 론
References

• 차은엽(SeoulTech) | Eun-Yeop Cha
• 정순필(Arotech Inc.) | Sun-Pil Jung
• 정광필(Mechanical and Automotive Engineering, Seoul National University of Science and Technology) | Gwang-Pil Jung Corresponding author