4.2 Measurement and Analytical Methods 4.2.1 Test Procedure and Sensor Arrangement Figure 4.1 illustrates the experimental arrangement along with the coordinate system. A set of data consisted of ground force and torque measured with a force plate, knee vibration measured with a vibration sensor attached to the inner side of the knee, and EMG (Electromyography) signal measured with a set of EMG sensors. The xyz-coordinate axes are affixed to the force plate as shown in Fig. 4.1. The test subjects performed two types of activities; marching and squatting, with one foot on the force plate at a time. Prior to any testing procedures, the test subjects were requested to fill out an Informed Consent and Medical History form, and a questionnaire regarding daylily activities they find difficulties with [3]. Although the testing procedures were stated in the inform consent form, each test subject was briefly informed of the procedures again. On completion of all these steps, the sensors were attached to the subject. The force plate and vibration sensor signals were acquired by a BiopacTMpackage [4], and the EMG signals were acquired with a DelsysTMpackage [5]. 4.2.1.1 Measurement with BiopacTMSystem The acoustic sensor was attached to the subject’s knee between the medial condyle of the tibial bone and the medial condyle of the femur. An electrode gel was used on the surface of the sensor. Once the sensor was in place, it was secured with a medical tape wrapped around the knee. The vibration sensor was attached to the leg that was placed on the force plate. This completed the attachment of the vibration sensor. After testing the first knee, the vibration sensor was switched over to the other leg that was placed on the force plate for the second round of the test. The force plate measured the x-, y- and zcomponents of the force and torque vectors. 4.2.1.2 Measurement with DelsysTMSystem Ten EMG sensors (five per leg) and two goniometers (one per leg) were attached to the subject. The goniometer was used to assure that the subject bend knee properly. The five EMG sensors were attached to the belly of the vastus lateralis, vastus medialis, rectus femoris, biceps fermoris, and the anterior tibialis muscle. Once all EMG sensors were in place, the goniometer was attached being lined up with the greater trochanter of the femur bone and the lateral malleolus of the fibula Fig. 4.1 Force plate and other sensor arrangement 26 S. Yoshida et al.
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