For some time now, a number of anti-skid brake systems have been
on the market which are characterized by their location between the
master cylinder and the wheel brakes, and separate from the brake
power-assist unit. At the present time, integrated systems are
being prepared for introduction. In these systems, the hydraulic
brake power-assist unit takes over both power-boost and ABS
pressure-modulation. The various concepts regarding ABS-integrated
brake power-assist units exhibit considerable differences in their
pedal characteristics when the ABS function comes into operation,
and with respect to the possibility of improving the behavior of
conventional brake systems.
It is the object of this article to present the various types of
ABS pressure-modulation in combination with brake power-assist
units, and to emphasize the advantages and disadvantages of the
individual concepts. In addition to the constructional outlay
involved, the aspects regarding anthropotechnical safety are taken
into consideration as criteria when the asessment is made.
The braking behavior during partial and panic braking in
cooperation with the anti-skid system is described with the aid of
curves demonstrating pedal force against pedal travel. These curves
show clearly how similarly, or how differently, the brake pedal
feels when the brakes are applied with, and without, ABS. With this
information, it is possible to draw conclusions on the quality of
the brake systems ability to adapt to the driver.
Using elementary diagrams, the hydraulic systems for the various
brake power-assist units with ABS are demonstrated.