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 - Steady State tests Dynamic tests

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