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Gravity Removal and Vector Rotation Algorithm for Step counting using a 3-axis MEMS accelerometer

3축 MEMS 가속도 센서를 이용한 걸음 수 측정을 위한 중력 제거 및 백터 전환 알고리즘

  • Kim, Seung-Young (Dept. of Computer Information and Science, Inha University) ;
  • Kwon, Gu-In (Dept. of Computer Information and Science, Inha University)
  • 김승영 (인하대학교 컴퓨터정보공학과) ;
  • 권구인 (인하대학교 컴퓨터정보공학과)
  • Received : 2014.01.09
  • Accepted : 2014.04.15
  • Published : 2014.05.31

Abstract

In this paper, we propose Gravity Removal and Vector Rotation algorithm for counting steps of wearable device, and we evaluated the proposed GRVR algorithm with Micro-Electro-Mechanical (MEMS) 3-axis accelerometer equipped in low-power wearable device while the device is mounted on various positions of a walking or running person. By applying low-pass filter, the gravity elements are canceled from acceleration on each axis of yaw, pitch and roll. In addition to DC-bias removal and the low-pass filtering, the proposed GRVR calculates acceleration only on the yaw-axis while a person is walking or running thus we count the step even if the wearable device's axis are rotated during walking or running. The experimental result shows 99.4% accuracies for the cases where the wearable device is mounted in the middle and on the right of the belt, and 91.1% accuracy which is more accurate than 83% of commercial 3-axis pedometer when worn on wrist for the case of axis-rotation.

최근, 다양한 형태의 웨어러블 컴퓨팅 디바이스와 이에 따른 응용 프로그램이 개발되고 있으며, 이들 중에서 헬스 케어의 한 영역으로 웨어러블 컴퓨팅 디바이스를 이용하여 개인의 운동량은 측정하는 다양한 연구가 진행되고 있다. 본 논문에서는 가장 기초적인 운동인 걸음걸이 측정 알고리즘으로 중력 제거 및 백터 회전(Gravity Removal and Vector Rotation) 알고리즘을 제안하고, 이를 위한 실험으로 보행 또는 주행 중인 개인의 다양한 위치에 부착한 웨어러블 디바이스에 장착된 3축 MEMS 가속도 센서로부터 획득된 가속도 값을GRVR 알고리즘을 이용하여 걸음 수를 측정한다. GRVR은 가속도 센서로 획득된 3축 가속도 값으로 부터 중력에 의한 가속도 분은 저대역 필터를 이용하여 제거 하고, 이 후 각각의 가속도 값에서 직류 성분 제거 및 센서 축 회전 보상인 GRVR 알고리즘으로 보행 혹은 주행 중에 순수하게 걸음걸이에 의하여 발생하는 가속도 변화분 만을 추출한다. 실험 결과로 웨어러블 디바이스를 개인의 허리 중앙 혹은 우측에 부착한 경우 GRVR 알고리즘을 이용한 걸음 수 측정은 99.4%의 정확도, 또한 손목에 부착한 경우 상용 3축 가속도 만보계의 83%보다 정확한 91.1%의 정확도를 확인하였다.

Keywords

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