Genetic Optimization of Fuzzy Adaptive Cruise Control for Urban Traffic - Fuzzy Modeling and Control: Theory and Applications - page 257

Table 14.1 Consequents of the obtained controller
speed_mf_0 speed_mf_1 speed_mf_2

distance_mf_0 − 39.35 − 85.63 − 62.76

distance_mf_1 99.99 − 0.57 − 90.35

distance_mf_2 40.61 99.97 4.04

Fig. 14.8 Control surface for the best individual in the last population. Distances are in meters and
speeds in meters per second

it is intended that the vehicle controlled is capable of following the vehicle ahead
without colliding, even in the worst possible case. This produces strong variations in
the output of the controller at the instants of the changes in the speed. Moreover, it is
observed how the controlled car adapts its speed to that of the vehicle ahead, while
keeping below the legal limit of 50km/h.
Graph (c) shows the distance between cars (blue), the distance measured by the
sensor (green), which saturates at 15m., and the safety distance (red). It is observed
that due to the first term in the definition of the cost function in expression ( 14.20 ), the
distance between vehicles remains greater than the safety distance, except for some
short moments, when the car controlled suddenly brakes. From this point of view,
when necessary, the control system acts as an emergency braking system, although
this is not the purpose.
Finally, in graph (d) the difference between the measured distance and the safety
distance is shown. In absolute value, this difference reaches higher values during
accelerations that for braking, which is due to the different dynamics in these cases.