257 3.2.1 Angle between tractor-trailer
258 The results of the angle between the tractor and the trailer() at the hitch point also showed the difference
259 in the tractor-trailer with and without the SHB unit. Because () was the angle between the longitudinal axis
260 of the tractor and the trailer, a positive value indicated that the trailer was directed towards the left side of
261 the tractor's longitudinal axis while a negative value indicated that the trailer was directed towards the
262 right side (figure 19.). During turns, the magnitudes of the angle between the tractor-trailer with Hitch-
263 Adj control mode were smaller those from the Hitch-Fix control mode. Moreover, the differences were
264 negligible during the straight trajectories. this indicates that the hitch-point was translated out away from
265 the turning direction, widening the trailer's turn in the curves.
266 The real-time calculation of the steering angle changed when landmarks were detected, which in turn
267 changed the position of the hitch-point because it depended on the steering angle. The total response of the
268 system was also considered. During the beginning of a tight turn or a U-turn, the steering angle was large,
269 which increased speed of the change in the hitch-point position and caused the trailer to turn farther from
270 the inside of the curve. On the other hand, some of the landmarks were not detected. However, only a very
271 few were missed during the experiments and they did not have much of an effect on the position of the
272 tractor and trailer
273 3.2.2 Instantaneous Centre of Radius
274 The distance between ICR and P R was the instantaneous turning radius of the trailer measured at the
275 trailer wheels. the results of R from the Hitch-Adj and Hitch-Fix experiments showed the different
276 behaviour of the trailer during experiments. During the straight trajectories, when the tractor-trailer was
277 not navigated to turn, the observed values of R observed were generally high. therefore, only the results
278 during the curves were considered, which were indicated by a thick line(Figure 20.). Theoretically,
279 shifting the hitch position away from the turning direction should reduce R However, the factors affecting
280 R were not just the position of the hitch-point but also () and (). In the experiments because the SHB
281 controlled the position of the hitch-point but not (), the position of the trailer during Hitch-Adj and Hitch-
282 Fix were not the same, resulting in a fluctuation in the difference of R (Figure 21.,22.).
283 In summary, the presented position of the trailer, the angle between the tractor-trailer and the turning
284 radius indicated that the navigation system cause the trailer to be turned farther from the inside of the curve.
285 If the position of the trailer was controlled instead of it being freely towed, the trailer could be navigated
286 with the tractor with greater efficiency.