Truck & Off-Highway Engineering - June 2024 - 15

TECHNICAL INNOVATIONS
also be outfitted for Class 5 duty should
a customer desire. " The only thing we
change for Class 5 is the springs, " Dow
said. " We went with the twin damper
setup because we wanted to reduce the
travel height of the suspensions. In order
to use coil springs, we needed to
get the static height as low as possible. "
Cornering the market
All four corners of the P7's suspension
are identical, which according to REE
reduces cost and complexity in manufacturing
while also allowing for greater
control over chassis behavior. " Certain
things will change with the location of
the corner, " Dow explained. " You will
have a leading or trailing caliper for
brakes depending on which side of the
truck it is installed on, but our software
compensates for that. "
Dow continued, " The whole premise
is really about one part number for
each corner that can be interchanged
on and off the truck within a one-hour
window. We have a multi-connector
that connects the high- and low-voltage
systems automatically, which means we
have no high-voltage connections at
the corners themselves. We're trying to
keep this outboard section of the truck
as conventional as possible with the
components we're choosing. For example,
the brake calipers, rotors and
park brake system are all off-the-shelf
pieces from Brembo. "
The P7's brake system is 100% brakeby-wire,
with various components supplied
by Brembo including part of its
Sensify system (www.sae.org/
news/2022/08/brembos-sensify-aimsto-revolutionize-braking).
" It has elements
of the Sensify technology, " Dow
said. " We have their system managing
the pressure to disc and pad, and on
top of that our application code assists
to manage the ABS and other systems. "
The system uses a Brembo braking
actuator with a 48V system that then
drives up to 115 bar (1,668 psi) of pressure
through the braking system. " Using
this system means we get flexibility in
terms of how we control the system.
We can brake independently on all four
corners, " Dow explained.
TRUCK & OFF-HIGHWAY ENGINEERING
TOHE Smalley Ad 0624.indd 1
" We have a lot of control over the
motion of the vehicle, " he said. " We
have independent control over the
drive, brake and steering of all four corners
of the truck simultaneously. The
way our control strategy works is each
corner has its own ECU which manages
the steering, braking and traction. We
then have a central control unit that
manages each corner in terms of action.
For example, a driver will ask for a yaw
command and that yaw may come from
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Truck & Off-Highway Engineering - June 2024

Table of Contents for the Digital Edition of Truck & Off-Highway Engineering - June 2024
