Load measurement: The total four torque of front and rear
driving axles was measured as shown in Fig. 1. The strain-gauge
for front driving axle was attached on the king pin which was
connected between final drive shaft and wheel as in Fig. 1(a).
The rear driving axle torque was measured at the final drive shaft
which was connected to the wheel as in Fig. 1(b). The torque
was measured with four elements full-bridge strain-gauge (CEA-
06-250US-350, Micro Measurement Co., USA) which was
mounted on 45 degree from the axial direction to minimize the
influence of bending moment 7
. The signal was detected using
slip ring (SK6, HBM Co., Germany). Also, a guard case was mounted
on the front and rear driving axles to protect the slip ring and wire
connection.