Powertrain Test Facility Design and Construction
A.J. Martyr, M.A. Plint, in Engine Testing (Fourth Edition), 2012
Full Powertrain Test Rigs
Powertrain test rigs can now be built to be capable of using either the
engine as the prime mover, or an electric motor simulating the engine.
The evolution of such cells has been made possible by the
comparatively recent development of permanent magnet
motors (PMMs) and their associated controls in the automotive power
ranges. These units are capable of engine simulation including that of
most driveline dynamics and combustion pulses.
The same motor technology has produced dynamometers having low
inertia yet capable of absorbing high torque at low speeds, thus
providing road wheel load simulation that, with customized controllers,
includes tire-stiffness and wheel-slip simulation.
An important logistical justification for such “all-electric” powertrain
cells, besides not having to install and maintain all the cell services
required by running an IC engine, is that the required engine may not
be available at the time of the transmission test.
One cost-effective arrangement that suffers from similar logistical
problems of unit availability but which overcomes several rig design
problems is shown in Figure 4.12, where a complete (dummy or
modified production) vehicle is mounted within either a two-wheel or
“four-square” powertrain test rig.
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FIGURE 4.12. A “wheel dynamometer” system installed within a garage
workshop space having a simple exhaust gas extract system and being used to
carry OBD tests. A large cooling fan would be needed in front of the car radiator
when running under power.
(Photo courtesy of Rototest Ltd.)
It should be noted that, in spite of advances in motor and
drive technology, flywheels still have a valuable part to play in
transmission and powertrain testing and are often fitted to the free end
of “wheel” dynamometers, a position that allows
various flywheel masses to be fitted according to the demands of the
test and UUT (see Chapter 11 for a discussion of flywheels).
Powertrain rigs have to be designed to be able to take up different
configurations on a large bedplate, as required by the UUT layout. A
large tee-slotted test floor, made up of sections of cast-iron bedplates
bolted together and mounted on “air springs” (see Chapter 9), is the
usual way to enable the various drive-motor or dynamometer units to
be moved and aligned in typical powertrain configurations. However, a
cheaper alternative for multiconfiguration transmission test rigs, which
usually experience lower vibration levels than engine rigs, is shown
in Figure 4.13, where steel slideways set into the concrete floor allow
relative movement, albeit restricted, of the major dynamometer
frames.
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FIGURE 4.13. The five-axis transmission test rig fitted with an electric motor
as the engine simulator and a gear-change robot.
To allow fast transition times the various test units should be pallet
mounted in a system that presents a common height and alignment to
the cell interface points.
Powertrain and transmission
Powertrain systems solidified electronic control technology in vehicles,
from motorcycle engines to the latest high-end powertrain technology
in diesel, spark ignition, hybrid and electric vehicles.
The transmission system ensures that engine torque output is
efficiently transferred to the road, providing the traction and control the
driver requires. Today, most vehicle manufacturers are turning to
electronically controlled transmission systems to provide the precise
control necessary for new-generation automated manual dual-clutch
transmissions and fully automatic transmissions with up to eight
different speeds. Electronically controlled transmissions help improve
fuel efficiency and reduce driver workload. Designing powertrain and
transmission applications that meet government regulations and
consumers’ requirements for cleaner, more fuel-efficient vehicles while
delivering best-in-class engine control performance for an
uncompromised driving experience are the key trends that are driving
today’s powertrain and transmission systems.
The gasoline engine is the most common drive technology in the
world. Modern gasoline engines are able to meet very stringent
CO2 regulations, are cost-effective to manufacture and remain the
primary choice for urban driving. Common-rail fuel-injection
technology has dramatically improved the performance and efficiency
of diesel engines. Consequently, public perception of diesel engines
has changed, due to improved performance and fuel efficiency,
reduced noise and lower smoke emissions. High-pressure injection
systems and efficient exhaust-gas treatment modules will guarantee
even more eco-friendly and fuel-efficient driving in the future. The
gasoline direct injection (GDI) technology, with its potential 20%
improvement in fuel savings, is expected to grow significantly in the
coming years.
Consumer demand for mobility in emerging markets is leading the
motorcycle manufacturers to move from mechanically to electronically
controlled systems to meet stricter emissions regulations. In the west,
the vehicle makers see engine downsizing as an opportunity to reduce
CO2 levels significantly and to boost the fuel economy.
Hybrid vehicles combine an internal combustion engine and a battery-
powered electric motor to power the drivetrain, improving fuel
economy and reducing harmful emissions. In addition to the internal
combustion engine control unit, other modules are required to control
the electric traction motor, recharge the battery and manage the
energy used to run the start/stop system, fuel and water pumps. The
start/stop system is the first step in the vehicle electrification. Also
referred to as micro-hybrid technology, this system turns the engine
off when it would normally idle in neutral and restarts it instantly when
the accelerator is pressed. This is a particularly effective system in
urban “stop and go” driving conditions where fuel consumption and
CO2 emissions can be improved by up to 15%. Electronically
controlled fuel and water pumps can more precisely deliver accurate
fuel and coolant flow and pressure within the engine environment and
operate only when required. This helps ensure not only economical
fuel management but also that the engine runs at optimum
temperatures for the most efficient operation. Electronic control is
essential for vehicle makers to develop a beltless engine and to
remove all-engine driven loads, such as electric power steering and
the A/C compressor, which need to operate even when a hybrid
vehicle has its engine off. Distributed systems incorporate smart
actuators where networked mixed-mode control devices are directly
mounted on the actuator to help reduce the ECU developer’s design
effort. Figure 22.7 is a map of all the powertrain and transmission
systems in a standard vehicle.
