trucksim 2022

Powertrain Improvements
Series and Parallel Hybrid Models
The powertrain model adds two types of hybrid electric models to an existing hybrid model: one is
Series Hybrid (also known as “REEV: Range-Extended EV) and the other is Parallel Hybrid. The
series hybrid system involves an engine directly connected with a generator which charges the
electric battery whereas separate motor(s) drive the wheels. On the other hand, in the parallel hybrid
system, an engine and motor(s) are parallel structure that the engine and motor(s) drive the wheels
through the transmission when a clutch is engaged while the wheels are driven by only motor(s)
when the clutch is disconnected.
The existing hybrid model which involves a planetary gear is renamed as Power-Split Hybrid
(OPT_HEV = 1) as distinguished with the new series hybrid (OPT_HEV = 3) and parallel hybrid
(OPT_HEV = 4.)
Powering trailer axles
Articulated busses and some other combination vehicles are powered by driving trailer axles, rather
than axles on the lead unit. When a powertrain is defined in a combination vehicle, a new parameter
POWERTRAIN_UNIT specified which unit contains the powertrain. The default value is 1 (the lead
unit), and the parameter is hidden from the Echo file and ignored if the vehicle does not include a
trailer.
Trailers with Moving Parts
New options were added to support two kinds of connections for trailers that involve moving parts.
One is for a ball or pintle hitch connected to a trailer with a hinged tow bar. These are used for
truck dollies to avoid hitch loads on the pintle. Another is for articulated busses, which use an
articulation system with a hinge connecting to the lead unit from a structure that is attached to the
trailing unit with an articulation joint.
In support of these new connection options, the calculations made for hitch connections were
redone. A new command OPT_HITCH_TYPE sets the type of hitch to 1 (generic or fifth wheel),
2 (ball or pintle hitch), 3 (ball/pintle connected to a massless tow bar, or 4 (articulation system).
The first option (OPT_HITCH_TYPE = 1) provides the same model and associated outputs that
were available in past versions.
Generic and fifth-wheel hitches (OPT_HITCH_TYPE = 1)
The generic hitch calculates rotations that occur on a fifth wheel in which a pitch hinge (Y rotation)
is attached to the leading unit, an articulation hitch (Z rotation) is attached to the trailing unit, and
the intermediate roll direction (X rotation) is defined by the vector cross product Z x Y. These
angles, based on the rotation sequence Y-X-Z (also called 2-1-3) are not the same ones defined by
ISO and SAE for defining sprung mass orientations; those start with yaw (Z rotation), pitch (Y
rotation), and finally, roll (X rotation).
The generic hitch model calculates the 2-1-3 hitch angles based on differences in the sprung mass
3-2-1angles, then calculates moments based on those angles and their rates, applies the moments
to the leading and trailing bodies using the hitch 2-1-3 axes.
Ball and pintle hitches (OPT_HITCH_TYPE = 2)
Ball and pintle hitches apply forces to connect a point in the rear of the leading unit with a point in
the front the trailing unit. No moments are calculated from the angles. When the new type 2 hitch
is specified, the moment calculations are skipped. Also, parameters, tables, and output variables
associated with those calculations are not added to the VS Math Model.
Hinged tow bars (OPT_HITCH_TYPE = 3)
A new option (type 3) was added to support the simulation of trailers with hinged tow bars. This
option adds a massless tow bar that is hinged in pitch, such that the vertical force (perpendicular to
the bar) is zero. With this option, the VS Math Model calculates a relative pitch angle of the bar
such that the normal (vertical) force is zero. The hitch still applies forces laterally and in the
longitudinal axis of the hinged bar.

An additional parameter is defined with this option (LX_TOW_BAR) and outputs are generated as
needed to animate the moving tow bar.
Articulation systems (OPT_HITCH_TYPE = 4)
Another new option (type 4) was added to support the simulation of articulated busses, where the
hitch geometry is set to reduce the vertical space needed to separate the pitch and articulation joints.
The distance is horizontal (rather than vertical as with most heavy-truck fifth wheels). This distance
might be significant.
This option adds a massless structure to the trailer that articulates and connects to the leading unit
with a hinge that allows relative pitch. The origin of the sprung mass coordinate system is moved
in the X-Y plane of the trailer sprung mass such that the articulation point remains behind the hitch
point the leading unit by the distance LX_ART (a new parameter for this type of hitch).
Along with the new parameter, new outputs are generated as needed for this type of hitch. All the
2-1-3 moments calculation for the generic (type = 1) hitch are also applied with this type.
Wheel Center and 3-1-2 Definitions for the Independent Suspension
There is a new option for the generic/independent suspension model, keyword OPT_IND_KIN,
available from a checkbox on the Suspension: Independent System Kinematics library screen.
When OPT_IND_KIN is on (=1), the longitudinal movement, lateral movement, dive, and camber
kinematics tables are interpreted with definitions more closely matching physical measurements or
general simulation outputs. Specifically, the wheel carrier is oriented relative to the sprung mass
by a 3-1-2, steer-inclination-dive rotation sequence, where the steer and inclination are given by
the toe and camber input tables. The wheel carrier is then translated by the translational input data,
meaning that data gives the wheel center displacement. The option works by generating another set
of kinematics tables which allow the model to match the position and orientation given by the input
tables’ alternate definitions. This capability is enabled by the built-in Independent Suspension
Kinematics Utility (IKU), which handles the conversion calculations.
OPT_IND_KIN off (=0, the default) retains the previous behavior exactly. The effects of the option
are readily compared with four new examples in the “* Independent Suspension Kinematics”
category:
• Kinematics: Bounce (OPT_IND_KIN=0)
• Kinematics: Bounce (OPT_IND_KIN=1)
• Kinematics: Roll (OPT_IND_KIN=0)
• Kinematics: Roll (OPT_IND_KIN=1).
For more information, refer to the updated help file, Help > Suspension Systems, especially the
new “Suspension Kinematics in the Math Models” section.
GPS Calculations
GPS coordinates are calculated and provided as output variables for the first vehicle unit and for
moving objects. The conversion from global X and Y coordinates in the simulation model

coordinate system to GPS have been based on the starting location of the vehicle, with updates
occurring when there is a significant change in GPS latitude. Several improvements were made to
accommodate simulations involving multiple vehicles and moving objects that might be separated
by significant distances.
1. Simulations involving more than one vehicle running within a single VS Solver now
include GPS outputs for all vehicles, rather than just the first vehicle.
2. The GPS conversion parameters GPS_REF_LAT, GPS_REF_LONG, GPS_REF_X, and
GPS_REF_Y now retain their initial value, reflecting the value associated with the creation
of the road or scene. Instead, when any reference point is reset for a vehicle or moving
object, the run’s log file will contain a line indicating the vehicle or moving object ID and
the latitude/longitude at the reset.