15 09 16

Page 1

TECHNOLOGIES FOR MOTOR BEHAVIOUR ANALYSIS AND VIRTUAL MODELLING September 15, 2016 EXERCISE 1 An Ag-AgCl electrode is placed on the skin in order to measure a biological signal. Considering a condition of saturated solution where the activities α of cations and anions are equal and constant, estimate the contact potential at equilibrium con dition given a skin (reaction) temperature of 35°C and a dissociation constant at 35°C equal to Kd = 6,34x10-10 (consider EOAg/Ag+ = +0.78 V, gas constant R = 8.31 J, Faraday constant F=96500 C/mole) EXERCISE 2 A parallelepiped-shaped force platform has a thickness of d=5cm and a rectangular base. Four load cells, displaced as shown in Fig.1, are longitudinally spaced by a distance a equal to 70cm and transversally spaced by b=50cm. The data collected by the platform, representing the force reactions during walk, are the following: Given that all the reaction forces refer to the lower base of the platform, with the xz plane of the reference frame laid over the lower base and the origin of the axis placed over the second load cell (see Fig.1), calculate: 1.1 The location (xS, yS, zS) of the point S, as the intersection point of the reaction force vector R and the sensor plane (the lower base) 1.2 The location (xcp, ycp, zcp) of the center of pressure cp as the intersection point between the reaction force vector R and the upper surface of the platform Figure 1. Force platform The reactions components generated by the platform and reported above correspond to the situation of a subject in toe-off phase (just before the swing, see Fig. 2). Considering the angle between the foot and the platform surface θ equal to 45° and the accelerations measured at the feet COM (which lies exactly on the mid- foot) equal to az = 3m/s2, ay=1m/s2 ,…