20 CONTROL SOFTWARE
Gain
control Vehicle dynamics engineer, Paul Beever, explores the principles
that should be implemented in control software to
achieve enhanced driver control
WORDS BY PAUL BEEVER
›The objective of vehicle control software is to
help drivers make a vehicle move or slow as
they want it to, ensuring that vehicles feel
safe, predictable and enjoyable to drive. To further
clarify this objective, I have often heard engineers
talking about needing to prevent drivers from doing
‘something bad’, such as locking the wheels when
they apply excessive brake-pedal force. Even though
the driver could still choose to do ‘a bad thing’, like
steering straight into a wall, for software engineers the
driver must be considered as being in ultimate control
of the vehicle, and responsible for its fate.
If an electronic system were to inhibit the driver’s
control, then that system would potentially be
responsible for any accident attributable to its action.
As such it seems unreasonable for any system to
override the driver, unless that system has access to
a much better quality and quantity of data than is
available to a competent and alert human driver.
I therefore prefer to consider that electronic systems
should change the input/output relationships of the
driver’s controls. Taking the brake pedal as an example,
in logical terms a mechanical brake simply interprets
the driver’s brake pedal effort as a demand for a
proportionate braking torque at the wheels.
However, with ABS I would say that the electronic
system changes that interpretation of driver demand.
The braking torque at the wheels is still required to
be proportional to the pedal force, except where it
needs to be limited due to the higher priorities of
vehicle stability and steerability. While ABS limits
total brake torque, it is understood that the objective
of ABS is to maximise braking, whilst maintaining
steerability and stability. The driver of a car with
modifi ed control responses will need to be informed
of, or learn, the control responses in order to be
able to make maximum use of the vehicle’s dynamic
capabilities.
VehicleDynamicsInternational.com • May/June 2020
/VehicleDynamicsInternational.com