22 Design of an Inertial Measurement Unit for Enhanced Training 277 • Adidas Catapult: an IMU able to return several information about the test. In particular, among the others, the three accelerations (forward, sideway and up) and the three angular velocities will be collected for the benchmark. Data are collected with a sampling frequency equal to 100 Hz. • GPS Sport: a GPS system returning information about the athlete’s position, elapsed time, covered distance: : : Data are collected with a sampling frequency equal to 5 Hz. 22.3 The Experimental Results 22.3.1 Experimental Setup Experimental tests have been carried out at the AC Milan training centre (Milanello). Figure 22.2 shows the satellite map of the facility as well as the base of the measurement campaign. Three different tests have been performed: • Test 1: the GPS system has been calibrated by walking along the football pitch and stopping for few seconds at the four corners (Fig. 22.3). Moreover a soft running along the reference trajectory reported in Fig. 22.3 has been carried out. • Test 2: four reverse direction exercises have been performed, (reference trajectories are shown in Fig. 22.4) considering a change of the sprint direction respectively of 135ı, 90ı, 45ı and180ı. • Test 3: a bike tour around the training centre. For tests 1 and 2, the IMUs are placed on the athlete back. The reference system is shown in Fig. 22.5. In test 3, instead, the IMUs are placed on the rear luggage rack of the bike and the reference system is shown in Fig. 22.5. 8.829 45.704 45.7045 45.705 45.7055 45.706 45.7065 45.707 45.7075 45.708 45.7085 45.709 latitude 8.83 8.831 8.832 8.833 longitude 8.834 8.835 8.836 8.837 Fig. 22.2 The AC Milan training centre (Milanello)
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