49
C H A P T E R 5
Active Control for Vehicle
Rollover Avoidance
Rollover avoidance control is another important subject for the study of rollover stability. With
the development of advanced control technology and cost reduction of electronic and control
equipment, various active control systems have been widely used in the automotive industry in
the design of anti-rollover control systems. At present, five main actuators have been proposed
and widely studied to prevent vehicle rollover: active anti-roll bar, active suspension, differential
braking, active steering, and combinations of these different techniques. Based on these actua-
tors, many researchers proposed advanced control algorithm to realize the vehicle’s anti-rollover.
5.1 ANTI-ROLL BAR SYSTEM
e anti-roll bar can adjust its deformation according to the vehicle motion by adding hydraulic
or electric actuator, and thus to control the posture of vehicle body. As shown in Figure 5.1, a stiff
U-shaped anti-roll bar is connected to the trailing arms directly and to the vehicle frame by a pair
of double-acting hydraulic actuators. e position of the anti-roll bar is therefore determined by
both the wheel positions and the actuator positions. By extending one actuator and retracting
the other, it is possible to apply a roll moment to the sprung mass and tilt the vehicle body.
First, Electronic Control Unit (ECU) collects relevant sensor signals including steering wheel
angle sensor, vehicle speed sensor, vehicle roll angle sensor, etc. According to control algorithm,
ECU calculates required roll moment of anti-roll bar, then the displacement of actuators can
also be determined. ECU controls the elongation or contraction of the actuators on both sides
through the drive circuit, the corresponding anti-roll moment is generated to prevent vehicle
rollover [43].
Many control algorithms have been proposed to determine roll moment of active anti-roll
bar. Huang et al. [2] and Vu et al. [44] present the application of Linear Quadratic Regulator
(LQR) algorithm for rollover prevention of heavy articulated vehicles with active anti-roll bar
control. Muniandy investigated a self-tuning fuzzy proportional-integral -derivative controller
to for active anti-roll bar [45]. H1 approach [46] and sliding-mode control method [28] are
also used to design active anti-roll bars.
50 5. ACTIVE CONTROL FOR VEHICLE ROLLOVER AVOIDANCE
Figure 5.1: Active anti-roll bar general arrangement.
5.2 ACTIVE SUSPENSION SYSTEM
e basic idea is that the equivalent roll damping and equivalent roll stiffness of active suspen-
sion can be adjusted. erefore, the handing stability and ride performance are improved. e
schematic diagram of active suspension is shown in Figure 5.2. Active suspension should have
three conditions: power producer which can generate acting force; actuating element which can
transfer the acting force; and sensors for collecting data and ECU for operation. When the vehi-
cle loads, speed, road condition, and so on, changes the sensors collect the status signal of vehicle
and feed back to ECU. ECU controls the power producer to generate the corresponding acting
force, the damping and stiffness of suspension can be adjusted automatically. e equation of
roll motion of a vehicle with an active suspension is shown as follows:
R
D
1
I
x
c
P
k
mgh
C ma
y
h C M
RC
C : (5.1)
Among the intelligent safety technologies for road vehicles, active suspensions controlled
by embedded computing elements for preventing rollover have received a lot of attention. Sarel
et al. presented the possibility of using slow active suspension control to reduce the body roll
and thus reduce the rollover propensity [47]. Zhu and Ayalew focuses on the application of
active suspensions to vehicles with solid-axles for medium and light duty trucks [48]. e active
suspension is also used in heavy-duty vehicles [33]. Active suspension can effectively resolve
the contradictions between vehicle ride comfort and stability. However, a new contradiction
between the active suspension performance and efficiency is aroused. Active suspension with
excellent performance requires high actuation power and force in an aggressive condition, which
is usually an excessive capacity for normal conditions. Sun et al. investigated on the efficiency
and utilization rate of vehicle active suspension based on a 7-DOF full vehicle mode with a
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