AUTOMATIC CAR STEERING USING
ROBUST UNILATERAL DECOUPLING
Jšurgen Ackermann 1 Wolfgang Walter
Tilman Bšunte
German Aerospace Center
Institute of Robotics and Mechatronics
D-82234 Oberpfaenhofen
Germany
Abstract: In this paper a steering controller is derived using robust unilateral
decoupling control. By this method automatic car steering can be split into two
subtasks: a) good lane tracking of a point mass for stepwise change of the curvature
of the lane reference and for lateral force disturbances and b) good yaw stabilization
in the presence of yaw torque disturbances. In the design process the track following
controller and the controller stabilizing the yaw rate are designed separately. A
Daimler Benz City Bus O 305 used in the Prometheus program and a Pontiac 6000
STE Sedan used in the PATH program give the practical background. In the latter
case with higher velocities gain scheduling by the velocity is used. Simulations for
these two cars illustrate the advantages of the developed structure.
Keywords: Automatic Steering, Automotive/Robust Control, Robust Decoupling
1. INTRODUCTION
Various controller structures and design approaches
have successfully been applied to automatic
car steering (see e.g. Ackermann and Sienel, 1990,
or Guldner, et al., 1999). These two projects are
used to evaluate the idea of robust unilateral decoupling
(Ackermann, et al., 2002). By this approach
it is possible to split automatic car steering
into two independent subtasks: lane tracking and
stabilization of the yaw rate which are discussed
in sections 3 and 4, respectively. As the main
focus of this work lies on the development of
the track following controller, rear wheel steering
is assumed for assuring enough damping of the
yaw motion. To be able to judge the capability
of robust decoupling the simulations based on a
Daimler Benz City Bus 0 305 and a 1986 Pontiac
1 Tel.: ++49-8153-28-2423
E-mail: juergen.ackermann@dlr.de
6000 STE Sedan are compared in sections 5 and
6 with the results presented in (Ackermann and
Sienel, 1990) and (Guldner, et al., 1999). For the
development of the mentioned controller structure
a model for the car is needed first. In this paper
the linearized single track model in combination
with the bar bell model for the mass distribution
is used. Combining these equations with the decoupling
controller is content of the next section.
2. STEERING DYNAMICS AND ROBUST
UNILATERAL DECOUPLING
The basic idea of robust decoupling is to make
the lateral acceleration of the car independent of
its yaw rate for one single location which is called
decoupling point DP. In this context the term
“robust” implies that varying parameters like the
velocity of the car (v 2 [v-; v+]), its mass (m 2 [m-;m+]) or the friction coecient (” 2 [”-; 1])
.....