Page 449 - Automotive Engineering Powertrain Chassis System and Vehicle Body

CHAP TER 1 4. 2 Decisional architecture

Fig. 14.2-20 Motion and control commands in the parallel parking scenario: (a) motion, (b) steering angle and (c) velocity controls applied.
the parking place (e.g. the values of T; f max and v max obstacles. The basic motion planning problem is readily
differ for the first and last iterative motion). illustrated with the concept of configuration space that
was introduced in robotics in the late 1970s by Udupa
14.2.4.4 Experimental run of the (1977) and Lozano-Perez and Wesley (1979a). The
platooning manoeuvre configuration of a robot is a set of independent para-
meters representing the position and orientation of every
An experimental run of the platooning SBM in a street is part of the robot. In its configuration space, a robot is
shown in Fig. 14.2-21. The linear camera and the infrared represented as a point, stationary obstacles are repre-
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target is shown in Fig. 14.2-22. During the execution of sented as forbidden regions and motion planning
a platooning manoeuvre, the linear camera operates at between a start and a goal configuration is reduced to
a frequency of 1000 Hz for providing the relative finding a path, i.e. a continuous sequence of configura-
position/orientation parameters of the two vehicles; the tions, that avoids the forbidden regions.
accuracy of the measurement has been estimated at The basic motion planning problem is essentially
a value of 1 mm for a distance of 10 m. It has experi- geometric, it deals with collision avoidance of stationary
mentally been shown that the system is robust according obstacles and it computes a path, i.e. a geometric curve in
to various lighting and light reflecting conditions (thanks
to the camera characteristics, to the pulsing infrared
target, and to the used filters). Experiments have been
conductedatspeedsupto60km/h,withdecelerationsupto
2
2m/s . The distance between the vehicles is proportional to
the speed (see Section 14.2.3.6), with a gap of 0.3 s.

14.2.5 Motion planning for car-like
vehicles

14.2.5.1 Introduction

The purpose of every robot is to perform actions in its
workspace (grasping and mating parts, moving around to
explore or survey, etc.). Carrying out a given action Fig. 14.2-21 A platoon of two vehicles: a leader Ligier and
usually implies that a motion be made by the robot hence a following Cycab.
the importance, in robotics, of motion planning, i.e. the
determination of the motion that is to be performed in
order to achieve a given task. This importance is naturally
reflected in the number and variety of research works
that have dealt with motion planning in the past 30 years.
Latombe’s (1991) book is undoubtedly the reference
book for robot motion planning. Its table of contents
reveals the importance of what Latombe refers to as the
basic motion planning problem. Six out of ten chapters are
dedicated to this problem, which is to plan a collision- Fig. 14.2-22 Experimental setup for platooning: (a) the linear
free path for a robot moving freely amidst stationary camera, (b) the first experimental infrared target.

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The set of configurations yielding a collision between the robot and the obstacle.

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