Development of Joint Angle Measurement System for the Feedback Control in FES Locomotion

FES보행중의 피드백제어를 위한 관절 각도계측 시스템 개발

  • 문기욱 (건국대 의료생명대 의학공학부) ;
  • 김철승 (고려대학교) ;
  • 김지원 (건국대 의료생명대 의학공학부) ;
  • 이재호 (건국대 의료생명대 의학공학부) ;
  • 권유리 (건국대 의료생명대 의학공학부) ;
  • 강동원 (건국대 의료생명대 의학공학부) ;
  • 강곤 (경희대 전자정보대 동서의료공학과) ;
  • 김요한 (건국대학교 충주병원) ;
  • 엄광문 (건국대 의료생명대 의학공학부, 건국대 의공학실용기술연구소)
  • Published : 2009.01.01


The purpose of this study is to develop a minimally constraint joint angle measurement system for the feedback control of FES (functional electrical stimulation) locomotion. Feedback control is desirable for the efficient FES locomotion, however, the simple on-off control schemes are mainly used in clinic because the currently available angle measurement systems are heavily constraint or cosmetically poor. We designed a new angle measurement system consisting of a magnet and magnetic sensors located below and above the ankle joint, respectively, in the rear side of ipsilateral leg. Two magnetic sensors are arranged so that the sensing axes are perpendicular each other. Multiple positions of sensors attachment on the shank part of the ankle joint model and also human ankle joint were selected and the accuracy of the measured angle at each position was investigated. The reference ankle joint angle was measured by potentiometer and motion capture system. The ankle joint angle was determined from the fitting curve of the reference angle and magnetic flux density relationship. The errors of the measured angle were calculated at each sensor position for the ankle range of motion (ROM) $-20{\sim}15$ degrees (dorsiflexion as positive) which covers the ankle ROM of both stroke patients and normal subjects during locomotion. The error was the smallest with the sensor at the position 1 which was the nearest position to the ankle joint. In case of human experiment, the RMS (root mean square) errors were $0.51{\pm}1.78(0.31{\sim}0.64)$ degrees and the maximum errors were $1.19{\pm}0.46(0.68{\sim}1.58)$ degrees. The proposed system is less constraint and cosmetically better than the existing angle measurement system because the wires are not needed.


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