MAHA LPS 3000, Operating Instructions Manual, Page: 73 / 115

BA052301-en
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9.1.4 Driving Simulation
The driving simulation reenacts a road drive and/or a certain load which can be set with the
drive cycles based on specific drive resistances. The test stand range relates primarily to the
maximum speeds of the normal statutory driving cycles from 0 km/h to max. 120 km/h and ac-
celerations in the range of 1 m/s
2 .
Large masses can be simulated during the acceleration with double and single roller dynamom-
eters.
With deceleration, that is coastdown, only the mechanically existing inertia of ca.
250…300 kg
(LPS 3000); ca. 280/320 kg (MSR 500) and ca. 700 kg (MSR 1000) act per axle with the double
roller set. A higher inertia is not possible with coastdown. In the cycle this results in shorter
coastdown times as those given.
With single dynamometers with drive the possibility arises to simulate electrically between
600…700 kg per axle due to existing drives and an acceleration (deceleration) of 1 m/s² .
Consequently, drive simulations in the small speed ranges are possible. Another advantage is
that because of the drives the inherent dyno losses can be identified and stored at any time. The
accuracy of the load is increased significantly.
Influence of Various Factors
The simulation on the roller set is mainly influenced by the factors rolling and flexing resistance.
On/in a roller set these can be very different as opposed to the road depending on roller diame-
ter and concept (double or single roller).
Especially at low speeds < 50 km/h the flex and roll resistances of the rollers are larger than the
total resistance on the road. Vehicle weight and tire pressure also play a role. These losses
cannot be compensated without electric motor.
Consequently, there are large deviations in the driving simulation especially in low speed range
with the double roller.
Load Adaption
Using the option "Load Adaption" the street coefficients can be adapted to the rollers. As al-
ready mentioned, an adequate adaption can only be done in conjunction with an electric motor.
The MAHA MSR dynamometers with drive can conduct this kind of adaption under the above-
named limits. However, these do not correspond with the industrial standards of emission dy-
namometers.
Simulation Model
The operation mode Drive Simulation (Road load simulation) is generator- and motor-driven. The
vehicle-specific drive resistance characteristic including mass simulation is described by the
following simulation model:
) sin (
d
d
) (
m ech
1
ref
3
ref
2
2

  + − +

+

+

+ =
+
g Masse
t
v
m Masse
v
v Koeff D
v
v Koeff C
v
v Koeff B
v
Koeff A
F
Exp D
Exp D
ref ref
F Tractive force target value
Koeff. A Rolling resistance coefficient (constant)
Koeff. B Flexing resistance coefficient (linear)
Koeff. C Drag coefficient (square with n

2)
Koeff. D Drag coefficient (exponential with n being variable)
Exp. D Exponent D (1

n

3, one decimal place)
Masse Vehicle mass
m
mech
Mechanical mass
V Roller speed
dv/dt Roller acceleration