Page 448 - Automotive Engineering Powertrain Chassis System and Vehicle Body

Decisional architecture C HAPTER 14.2

14.2.4.3 Experimental run of the parallel the bay. The change in the environment is detected and
parking manoeuvre taken into account. The range data shows that the nec-
essary ‘depth’ in the bay has not been reached, so further
An experimental run of the parallel parking SBM in iterative motions are carried out until it has been
a street is shown in Fig. 14.2-19. This manoeuvre can be reached. Then, the Ligier moves to the middle between
carried out in environments including moving obstacles, the rear and front vehicles, as shown in Fig. 14.2-19(d).
e.g. pedestrians or some other vehicles (see the video The parallel parking manoeuvre is completed.
Paromtchik and Laugier (1997)). In this experiment, the The corresponding motion of the vehicle is depicted in
Ligier was manually driven to a position near the parking Fig. 14.2-20(a) where the motion of the corners of the
place, the driver started the autonomous parking mode vehicle and the midpoint of the rear wheel axle are
and left the vehicle. Then, the Ligier moved forward plotted. The control commands (Equations 14.2.9 and
autonomously in order to localize the parking place, 14.2.10) for parallel parking into a parking place
obtained a convenient start location and performed situated at the right side of the vehicle are shown in
a parallel parking manoeuvre. When, during this motion Fig. 14.2-20(b) and (c) respectively. The length of the
a pedestrian crosses the street in a dangerous proximity vehicle is L1 ¼ 2.5 m, the width is L2 ¼ 1.4 m, and the
to the vehicle, as shown in Fig. 14.2-19(a), this moving wheelbase is L ¼ 1.785 m. The available distances are
obstacle is detected, the Ligier slows down and stops to D1 ¼ 4.9 m, D2 ¼ 2.7 m relative to the start location of
avoid the collision. When the way is free, the Ligier the vehicle.
continues its forward motion. Range data are used to The lateral distance D4 ¼ 0.6 m was measured by the
detect the parking space. A decision to carry out the sensor unit. The longitudinal distance D3 ¼ 0.8 m was
parking manoeuvre is made and a convenient start posi- estimated so as to ensure the minimal safety distance
tion for the initial backward movement is obtained, as D5 ¼ 0.2 m. In this case, five iterative motions are
shown in Fig. 14.2-19(b). Then, the Ligier moves back- performed to park the vehicle. As seen in Fig. 14.2-20, the
wards into the parking space, as shown in Fig. 14.2-19(c). duration T of the iterative motions, magnitudes of the
During this backward motion, the front human-driven steering angle f max and locomotion velocity v max corre-
vehicle starts to move backwards, reducing the length of spond to the available displacements D1 and D2 within

Fig. 14.2-17 Snapshots of trajectory following with obstacle avoidance in a roundabout: (a) following the nominal trajectory, (b) lane
changing to the right and overtaking, (c) lane changing to the left, (d) catching up with the nominal trajectory.

Fig. 14.2-18 Motion and control commands in the "roundabout" scenario: (a) motion, (b) steering angle and (c) velocity controls applied.

Fig. 14.2-19 Snapshots of parallel parking: (a) localizing a free parking place, (b) selecting an appropriate start location, (c) performing
a backward parking motion; (d) completing the parallel parking.

455