Dynamic
Engine and Transmission Test Cell control & acquisition
Upgrade specification
Introduction
The dynamic engine and transmission test
cell at Bath has evolved over a number of years to allow dynamic powertrain
investigations. Data acquisition and control systems are in the main operated
manually and are not integrated. This makes operation of the cell time
consuming and requires much operator training.
Cell
Schematic
Cell
Photo
Requirement:
To move from our current position in an
organised manner towards a fully integrated test environment. This is likely
to happen in a series of key stages -
Stage 1
Replace current data
acquisition system with a modern, distributed system.
Stage 2
Incorporate test cell integration to bring
existing slave systems under co-ordination of host
where possible
Stage 3
Ongoing replacement of slave
systems as required. We anticipate that this will take a number of
years so the system developed for stage 2 needs to be sufficiently open
for us to add new devices using established protocols with reference to
the appropriate documentation.
Host System
The purpose of the host system is to communicate
with and where necessary instruct the slave systems.
This will often take the form of a sequence of operations
which build up to form a test sequence. Different test sequences will be
required for the various operating modes of the rig. The host will also
gather data from the various sub-systems and archive locally or across
a network for later reporting. We currently use an Excel based reporting
tool developed in-house. The format of the data required to input to this
tool is flexible but is essentially comma or tab delimited Ascii.
Slave systems
A number of dicreet devices or groups
of devices are termed here as slave systems. They are -
Data acquisition
Test cell operator
data display
Emissions Analysers
Dyno control
Fluid temp control
Transmission control
& Driver Emulation
Rig start and run/shutdown
controls
Data acquisition
One important requirement is that the
data acquisition system is distributed around the test environment. It
is hoped that the current situation, where many individual signal cables
carry low level signals to remote signal conditioning and digitisation
systems, can be avoided.
Analogue and Digital
112 a/d channels max. - to be
reduced as more digital comms are implemented. These would comprise -
16 general 0-10v
16 Pressures
32 Temperatures
8 shaft speeds
8 positions
32 digital
12 PWM duty cycle measurements if available
Maximum data acquisition rate of around
200Hz per channel would be required with configurable digital filters (principally
low pass).
CAN
The ability to read CAN
messages from one or two busses and display/store in the same manner analogue
data. Typically these data would be generated by the engine or transmission
controller on test but possibly by dedicated modules running control and/or
acquisition tasks autonomously in the test cell.
GBIP
Some Test cell equipment uses
the GPIB bus for control and data output. As before this data needs to
be handled after acquisition in the same way as the A/D channels
AK serial protocol
Other (mainly German) test cell
equipment uses the automotive AK serial protocol
RS232 / 485
General test instruments (e.g.
Torque meters) use a variety of RS232 based protocols.
ECU Communications
Other than by CAN, the most usual
method of communicating with engine ECUs is via the ASAP
family of serial comms developed by a consortium of Automotive manufacturers.
Sequences
A number of individual commands will be
built up by the user to form sequences common in everyday operation. These
need to be user definable, an desirable enhancement would be the ability
to record a sequence of manual actions for later use in the way that Excel
allows macros to be recorded.
Some common sequence types would be -
Initialise - set all devices to
a known operating state and wait for confirmation where appropriate (temperature
limits etc.)
Auto Calibration
Manual Calibration
Test
Report generation - probably handled by
Bath Excel macro.
Some other activities which should go on in
the background, transparent to the user where possible are -
Export data
Archive data
Archive test cell configuration
Generate documentation of test cell configuration
Record errors at run time (post mortem
log)
Generate Processed variables
Data validation
Tests
Auto sequence,. typically -
-
Check analysers for errors
-
Configure analysers
-
Calibrate analysers
-
Perform test - maybe a series of demands or
actions for slave controllers to implement
-
Check analysers for errors
-
Check analyser calibration
-
Report
Steady State tests
-
Automated test sequence, possible optimisation
features i.e. identify control settings which return minimum measured value
on another channel
-
Manual test sequence
Dynamic tests
-
Steps, possible optimisation features as above
-
Drive cycles
Analysers
Gas analysers - MEXA
9000
MEXA 1220 EGR
Particulates -
TEOM
Opacimeter - Celesco,
will be AVL in time
Smoke Meter - AVL
415
Indicating system - Indiskop,
may be updated to Indimeter or similar
Fuel Meter -
AVL730/733
Torque meters -
HBM
Fluid temperature
control
Currently done on EMPS, could be
done by host in future
Controlled variables -
Engine coolant
Engine Oil
Fuel
Inlet Air
Charge Air
Driver Emulation
Currently done on EMPS, could be transferred
to dSpace in future
Principal outputs -
Accelerator demand
Brake demand
Gear demand
Clutch demand
Start and run/shutdown
Currently stand-alone - could be
combined with host system in future
Fuel pump 12v
12v
single phase
three phase
air
pond water
Test cell services
Test cell operator
data display
Currently a series of panel meters and
manual controls - could be combined with host system in future
Brief overview of functions -
Engine Speed
Engine Torque
Dyno Speed
Dyno Torque
Exhaust temperature
Coolant temperature
Gear status
Clutch status
Throttle demand pot
Dyno demand pot
Gear selector
Clutch control
Dyno control
In house hydrostatic dynamic dyno. Control
currently performed on DSP card running in PC. Future control to be performed
on EMPS or dSpace. Eventual replacement with Electric dyno according to
funding.
Functions to be provided by any new controller-
Speed control
Vehicle emulation
Calibration
Coastdown
Torque cal
Losses cal
MEXA 9000
GPIB comms
Measure
Purge
Calibrate
Zero
Span
MEXA 1220EGR
Digital Comms
Measure
Purge
Zero
Span
Data Out - 1 analogue channel
TEOM
Digital Comms
Pumps on/off
Data out - 3 analogue channels
Smoke
Meter
AK serial Protocol
Measure
Retrieve result
Fuel Balance
AK serial Protocol
Fill
Set measure time
Measure
Retrieve result
Opacimeter
AK serial protocol
Measure
Retrieve data
Indiskop/Indimeter
Serial Protocol
Set mode
Record Data
Torque
Meter
Serial Comms
Set filter bandwidth
Tare
Record Data