Truck & Off-Highway Engineering - June 2024 - 16

TECHNICAL INNOVATIONS
REE found during its testing that
once load begins to reach the top of
Class 4, it is helpful to vary the rear
steering ratio to provide more stability
during lane changes. " Rear steer will be
active up to 20 mph (32 km/h) and
then we blend it out as we reach that
plateau. We also have the ability to select
what we call anti-swipe, " Dow explained.
" If you're in a parking bay
where you don't want the rear steer to
be active, we don't engage the rear
steering until you've traveled at least
one vehicle length. Then the rear steering
is brought online again to ensure
that a driver does not tail swipe anyThe
P7 was designed principally for Class 3 and 4 configurations but can be outfitted for Class 5
duty should a customer desire.
thing next to them. "
" Once we go to higher speeds, say
50-60 mph (80-96 km/h), we actually
then bring the rear steering back in parallel
for instances such as high-speed
cornering and lane change maneuvers, "
he added. " So we really use our algorithms
and control strategies of the rear
steer to provide maneuverability at low
speed and stability at high speed. "
Active rear toe is via rear steer.
Active camber control could also be
added. " Because we are truly independent
across all four corners, there's no
linkage across corners like anti-roll
bars, " Dow said. " We have a reasonably
stiff suspension at each corner
that we can work with. We are then
looking at the control software to manage
that roll motion of the vehicle depending
on load. "
Dow's team also had to ensure the
" We're trying to dual source as many options as possible in the system, " said Peter Dow,
REE's VP of engineering.
the steering angle or it may also come
from the traction or torque vectoring. "
Safety (and stability) first
The P7 features a full suite of advanced
safety systems such as active yaw control.
REE has performed extensive testing
to ensure the P7 will remain surefooted
even in the worst conditions including
testing at the Artic Circle in Sweden.
" On the low mu ice lakes with our
active yaw system, we were able to
eliminate any form of oversteer, " Dow
16 June 2024
said. " If you try and oversteer, we have
the ability to use torque vectoring as
well as the rear steer to keep the vehicle
from spinning. Which means we
have a very stable truck. "
Dow also explained the control strategy
for the drive system. " We're predominantly
front-biased to start with in terms
of drive, " he said. " We actually have a
suspension travel sensor which allows us
to understand what sort of load we have
in the vehicle, which enables us to shift
power to the rear as we gain load there. "
P7's suspension provided enough clearance
to fit components such as snow
chains. " We have enough ability to get
up to 32 degrees of steering angle on
this unit, " he said.
Dollars and sense
The beauty of REE's approach to the
P7's suspension system is that it's an
existing technology that can easily be
modified based on what corner the unit
is being mounted on and what load the
truck will be carrying.
" We were looking at how we can get
volume to achieve a price point while
using the least amount of materials, "
Dow said. " We have the capacity to
TRUCK & OFF-HIGHWAY ENGINEERING
ALL IMAGES: REE

Truck & Off-Highway Engineering - June 2024

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