OVERVIEW
An industry-leading Electric Vehicle Test Cell Control and Data Acquisition open platform that provides the ultimate in modularity, flexibility, model integration and custom sensors:
- Quick and easy to deploy, configure and replicate.
- Reduce cost and complexity with a future-proof platform
- Achieve complete test coverage with a flexible platform
- Enable accurate and innovative powertrain test systems
- Achieve faster development times with automation and collaboration
- Adaptable to rapidly accommodate changing project requirements.
- Integration with existing systems.
- Supports multiple models including MATLAB/Simulink, AVL Boost and Cruise, TechnaliaDynaCar, IPG CarMaker, LabVIEW, C.
- Intuitive test sequencing and scripting via Python scripting engine.
Challenge
As WMG already has an existing test cell infrastructure, the solution had to address a number of key issues:
- Meet the demanding technical requirements of the system for multiple e-machine axis control and data acquisition.
- Provide cost-effective reuse of the existing test equipment and cell infrastructure by integrating directly with it.
- Integrate with a wide range of equipment, sensors and protocols.
- Provide flexibility to easily add new equipment in the future.
- Make the platform accessible and easy to use for as many operators as possible with varying levels of expertise.
- Ensure the safety of all operators and equipment is paramount at all times.
- Provide management and integrity of data acquired from multiple axes.
System Requirements
Control
Each axis of the test system is required to provide control outputs for the equipment to which the axis under test is connected:
- DC source
- Test inverter
- Thermal regulator (supplied with chilled water from an external cooling plant), capable of heating or cooling the machine under test coolant medium (e.g. water, oil) to maintain a set temperature
- Dynamometer inverter
Since the equipment used to implement the control functions may vary from axis to axis, it is necessary to ensure compatibility with a wide range of devices. Each of the control outputs need to be capable of operation using multiple serial data interface standards:
- High Speed CAN bus up to 1 Mbits/sec
- Ethernet up to 1000base-t
- Generic RS-232
- EtherCAT
- CANopen
The message protocols are dependent on the equipment that is connected to the control interface. Similarly, the drive parameters that are controlled during a test (e.g. current demand, torque demand, speed demand, etc.) depend on the configuration of the inverter being used to drive the e-machine/device under test (DUT). Since the protocols and parameters are defined by the DUT, it is critical that the control system provides software functionality that allows an appropriate data exchange with the inverter to be configured. Each axis must be capable of standard dynamometer test functions, such as:
- Open circuit test: DUT open-circuited, load machine at set speed (tested e-machine generating only, but could be driven in either direction of rotation)
- Short circuit test: DUT short-circuited, load machine at set speed (tested e-machine generating only, but could be driven in either direction of rotation)
- Set speed at load machine, variable torque at DUT (tested e-machine under motoring or generating, either direction of rotation)
- Set speed at DUT, variable torque at load machine (tested e-machine motoring or generating, either direction of rotation)
In all tests, the temperature of the DUT is managed by setting the coolant temperature using the thermal regulator.
Data Acquisition
Each axis of the test system is required to provide data acquisition functions that meet or exceed the specifications as stated below:
| Ambient temperature range for all transducers: | +5 °C to +40 °C |
| Current measurement: | 7 channels (+/-1,000 A) @ 100 kHz |
| Voltage measurement: | 7 channels (+/-1,000 V) @ 2 MHz |
| Power calculation: | Standard power measurement data (e.g. Irms, Vrms, phase angle, power factor) Current and voltage frequency analysis with data up to the 50th harmonic based upon a fundamental frequency of 50 Hz. |
| Temperature measurement: 16 channels, each with the following capability: | Thermocouple compatibility: J, K, T Thermistor compatibility: NTC (10 Ω to 10 kΩ), Pt50, Pt100, Pt200, Pt500, Pt1000, JPT100, Ni100, Ni120, Ni1000, CU10, Cu50 (4-wire and 2-wire configurations) Measurement temperature range: -40 °C to +250 °C |
| Noise and vibration measurement: | 8 x IEPE accelerometer or microphone channels Bandwidth: up to 200 kHz |
| Uncommitted additional analogue measurement channels: | 4 x 16bit channels for use with pressure sensors, flow sensors, etc. Bandwidth: up to 200 kHz |
| Torque measurement (from external torque sensor): | Voltage interface: ±5 V and ±10 V ranges Frequency interface: 10±5 kHz, 60±30 kHz and 100±40 kHz ranges To be compatible with HBM T12 series and Kistler 4503 and 4551 type torque sensors |
| Speed / Angle measurement (from external torque sensor or additional encoder): | Measurement range: -50,000 rpm to + 50,000 rpm Voltage interface: ±10 V range Encoder: 2 x fully differential channels inc. index pulse A/B/Z. The encoder implementation is a hybrid approach which allows detection of instantaneous speeds, even with an encoder frequency of over 1 MHz (and all the way down to 0 rpm). |
Test Sequence Definition and Data Capture
Having acquired the data, the management and integrity of data acquired from multiple axes is critical. A key requirement for the test system is to provide a means to define test sequences in terms of the controllable parameters of each axis, the data to be captured, and any timing requirements that go with this. Typically, pre-defined sequences such as standard vehicle test cycles can be imported and then converted to axis control and measurement parameters. Once a test sequence is defined, it must be storable so as to be available for re-use or modification at a later date.
Test Cell Supervisory Control
Due to the potential danger associated with rotating machinery and possibly hazardous voltages at the DUT, the test cell must offer full containment for the protection of personnel and assets. Therefore, in addition to each test axis, the test controller is required to manage the shared aspects of the test facility. These consist of:
- Load machine temperature management
- Axis over-speed fault protection, with options to define the fault containment behaviour (e.g. braked stop, coast down)
- AC mains failure detection
- Fire detection and suppression
- Test chamber temperature control
- Test chamber ventilation
- Safety door interlocks
- Emergency stops (manual push buttons and signals from equipment in the facility)
Solution
To ensure that the solution is able to integrate the existing equipment and test cell control system, the Austin Consultants team proposed a solution based on (NI) PXI modular hardware platform with a VeriStand deterministic real-time test engine at its heart. Able to run high-speed models and close the loop with real sensor data at rates of 1 kHz, the Test Cell Control and Data Acquisition System offers a cost-effective solution to accommodate the current test and integration requirements, combined with the extensibility to adapt to future hardware and test requirements.
It is flexible to accommodate new technologies and offers an extendable chassis for increased demands.
New sensors or bespoke protocols can be added via a simple low-cost, ‘plug-in’ (or ‘custom device)’ upgrade.
The modular system comprises:
- EVolution EV Test Software
- Test Cell Control and Data Acquisition System
- Test Cell Management Unit
- Power Analyser Rack and Remote Patch Panel
EVOLUTION EV TEST CELL CONTROL AND DATA ACQUISITION SOFTWARE
Design Goals
To ensure the software met all the demands of the system before architecting the solution, the team created a number of design goals that the system had to fulfil:
- To provide a cutting-edge EV test system that gives the users ultimate flexibility in a safe and managed environment.
- To provide standardised scripting tools to configure the system for not only anticipated tests but also future test requirements.
- Provide an easy-to-use management interface that expertly navigates the complexity of a highly flexible system, yet allows the user to be guided by it.
- To allow the user to focus on their research not how the test system works.
The resulting software is able to balance and address the unique demands of both system complexity and configuration with an intuitive and safe user experience for all operators across a range of expertise.
POWERFUL EVOLUTION FEATURES
Software Approach
To provide the level of flexibility required to integrate with the existing systems and accommodate new technologies for increased demands, the Austin Consultants team created a services-orientated architecture that allows new sensors, or bespoke protocols via a simple low-cost, ‘plug-in’ upgrade.
This features a System Management layer for configuring the system integration and tests, a deterministic real-time test engine for running models at 1kHz, and a device management layer that utilises device categories and validation to add new sensors.
SYSTEM MANAGEMENT INTERFACE
Ready to use off the shelf, the dynamic management interface handles system configuration without the need for extensive low-level system setup, allowing immediate deployment of tests and scripts.
The system is designed to allow a high level of flexibility and usability, without the need for high-level programming knowledge or experience whilst permissions-based user-level access allows adaptable low-level configuration for advanced users.
USER LEVEL-BASED ACCESS
In order to balance the need to make the platform accessible and easy to use for as many operators as possible, with varied levels of expertise, as well as safeguard personnel and equipment, the EVolution Control and Data Acquisition System can be configured to restrict users’ access. They are able to only utilise areas of the software that they have the expertise to use safely. For example, suggested access levels include Facility Manager, Test Engineer and Operator. However, the software itself operates with an access matrix that allows each individual login to have a custom set of access permissions as decided by the owner of the system. This allows for complete control and flexibility to build a user privilege system that is best suited to the particular needs.
The EVolution software links the access level of a user to the Microsoft account that they use to access the PC, the user account also contains all their individual settings and configurations saved to their user area.
CONFIGURATION
System Settings are high-level settings that apply globally and as such should only be accessed by facility managers. The software provides the system owner control over the main data storage areas of the system, as well as defining the IP addresses and network folders of key system addresses, specifically for the Test Cell management unit and the axis.
Administration limits are immutable settings in order to ensure that the system does not exceed safe limits at any time. Facility managers should set the values to ensure operation is always within safe limits. This is particularly useful when the ratings of two devices are different such that one can be run at a rate that would cause damage to another.
CHANNEL MAPPING WITH CALIBRATION AND ALARMING.
When first configuring, the system allows specific physical channels to be assigned to in ports and out ports in models. Users can name channels appropriately for their specific test, and apply scaling and calibration to ensure that channels are giving results in the correct units for their sensors.
ADVANCED WORKFLOWS
The advanced workflows process guides users through the required steps for loading models, channel assignments with scaling and calibration data, sensor databases, and test profile creation. A Profile Builder for generating new profiles means that the system can be configured for new tests without any programming.
The advanced workflows support the user to:
- Set up physical channels – calibration, sensor allocation, comms setup
- Add models
- Add calculated channels
- Map channels – I.e. model output to physical output
- Build configurable UIs
- Script tests
- Add alarms and setup background logging
- Deploy configuration to Real-Time Hardware
- Select whether multi-axis control is needed
HIGH-SPEED DETERMINISTIC MODELLING AND CONTROL (HIL)
Based on NI’s VeriStand engine, the system provides the ability to run many different types of complied models, ranging from MATLAB/Simulink, AVL Boost and Cruise, Technalia DynaCar, IPG CarMaker to simple models built in LabVIEW or pure C-code.
TEST MANAGEMENT
The test interface offers multiple flexible features to support the user whilst running tests including time-saving in-test modifications whilst also maintaining critical safety monitoring:
- Hardware configuration is locked
- Automated tests are run through scripts
- Manual control can be taken through operating the user interface
- The primary control loop is running (including any specified models)
- User Interface can still be modified – channels can be allocated to UI ‘widgets’
- Multi-axis control facilitates deterministic communications between two or more axis controllers
- Data is streamed to the specified location, which can be a server.
DYNAMIC USER INTERFACE
The dynamic user interface provides widgets to allow the user to configure and save interface profiles specific to the requirements, in the test, without the need to restart a test, thereby saving time.
The range of available widgets includes a series of fixed functionalities designed for control and indication of a specific area of the system and a range of more generic widgets allowing any combination of data in the system to be viewed together. Fixed widgets include Dyno Control, DUT Control, Battery Simulator Control, DUT Temperature Control, Power Analyser Control, Power Analyser Harmonics, Power Analyser Scope, Log Triggers, Safety System Feedback, Script Control, Script Terminal, Script Editor, Script Parameters, Cell Services Feedback. Generic Widgets include: Graph, Table, Dial, LED, Buttons, XY Graph, Sliders, Model Input, Model Parameters.
INTUITIVE TEST SEQUENCING AND SCRIPTING VIA PYTHON SCRIPTING ENGINE
In addition to the Dynamic UI, the system also offers a Python Scripting Engine which does not require high-level programming experience, allowing the platform to be accessible to a wider range of operators.
The integrated Python scripting tool allows new steps to be created for applying calculations to channels, importing new file formats and other requirements.
The fully-featured Python scripting engine allows users to write their own tests, and automate anything that they can do via the UI.
The support library makes interaction with the test system easy, with simple get/set calls, but also more powerful abstractions like “get_harmonic_data” (from the power analyser). Full Python3.x support is provided with syntax checking and high-level parameter extraction (passing parameter sets into your script) and the ability to create and use your own favourite packages/libraries, which allows advanced users to integrate analysis into the tests.
MULTI-LINK CAPABILITY
As well as being able to operate independently, up to 5 EVolution racks can be connected together and synchronised via a deterministic high-speed data sharing bus. This offers maximum flexibility when working with multi-axis/multi dyno configurations for any given scenario, the system is designed to effectively manage axes and resource allocation to ensure safety and data integrity are maintained and that one operator cannot influence the activities being carried out by another if multiple test sessions happen to be running concurrently.
DATA-LOGGING
Background logging runs throughout the test. The user is able to set various different rates. All the channels, including those that are capable of higher speed datasets, are also available for shorter ‘burst’ logging, configurable during runtime. These higher speed channels include e-machine current (LEM signals), encoder, torque, frequency, analogue channels and IEPE accelerometer channels. Log sets can also be setup prior to entering operational mode, and are triggered on the fly or by the scripting engine.
All datum is synchronised, time-stamped and logged to an industry-standard, compact, efficient file format called TDMS.
Datum is partitioned and stored separately for each test situation (e.g. dynamometer axis or combination of axes) and is controlled via permissions-based user-level access to ensure data confidentiality. The TDMS data is also compatible with the NI Systemlink Platform and DataFinder module that allows organisations to efficiently manage, search, access, and analyse measurement data. There are free plug-ins available for both MATLAB, Microsoft Excel and Python.
External Connectivity and Monitoring
The system offers two methods of external control over CAN. The first is to allow external users to “control” the dyno from their own system. The second is to allow 2-way communications to an external deterministic system that is running its own models. Both protocols are connected via the systems internal protection models to ensure safe operation at all times.
Remote monitoring of the current status of the system by key personnel is provided via a secure web interface.
TEST CELL CONTROL AND DATA ACQUISITION SYSTEM
The main control system consists of an 18-slot NI PXIe chassis fitted with a quad-core 2.6 GHz i7 processor running a real-time operating system, for maximum determinism. Both can be upgraded to increase system bandwidth and processing power if required in the future. This system allows high-speed models to be run at 1kHz. Data acquisition channels run at the same speed as the model (typically 1 kHz) with the exception of some high-speed channels, including speed, current and accelerometer measurements, which include a snapshot mode for acquiring signals at 200kHz for short bursts.
TEST CELL CONTROL AND DATA ACQUISITION RACK
A requirement for the system is that the equipment for each axis is provided in a self-contained form, allowing units to be positioned within the test cell(s) and connected to the test controller and data storage supervisory system as required. To ensure that the system is able to adapt to changing test cell configurations, the Test Cell Control and Data Acquisition system is mounted in a 29-unit rack with heavy duty castors to allow the test equipment to be moved around on rough and uneven floors safely. To ensure flexibility to accommodate potential future expansion requirements, the premium quality rack offers spare capacity with excellent options for additional mounting and wire routing.
DUT IO is on the front of the rack, and cell infrastructure IO is on the back, creating a clear logical separation between the two.
The front of the rack features an Emergency stop that is integrated into the full test cell safety infrastructure and LEDs that provide a clear indication of the safety status of the rack.
The system offers four high-speed analogue inputs and four outputs, frequency and encoder inputs, all of which log synchronously to high speed logs (including high-speed current measurement if selected). The communications buses offer EtherCat, CANbus, PROFIBUS, RS232, CANopen, XNET and are customised to the specific need using NI PXI cards. The Test Cell network allows multiple test racks to be controlled as one, for maximum flexibility.
Noise, vibration, and harshness (NVH) measurements are captured via IEPE inputs for high quality, using NI Dynamic Signal Acquisition card, at rates up to 200kHz.
The thermocouple and RTD inputs for temperature measurement are acquired through an NI EtherCAT RIO expansion chassis, so the data is acquired deterministically.
DIO can be provided in a combination of 12V and 24V options depending on requirements.
The remote IO interface allows all temperature inputs and DIO be broken out to an external patch panel, so they can be passed into a full environmental chamber.
An EtherCAT expansion port allows for additional EtherCAT devices to be added to the chain where required, and communicated with deterministically.
A custom power distribution unit provides easy access to MCBs for quick resetting, and power distribution at the required voltage levels around the rack. An auxiliary 12V or 24V output is also available.
EVolution Electric Vehicle Test Cell Control and Data Acquisition System and Power Analyser Rack – REAR
The cell infrastructure IO on back features:
- Safety Integration
- Test Infrastructure Comms
- Dyno Temps
- Power Analyser HS Inputs
- Data Sharing Network
The rear of the rack offers connectivity to the internal Windows gateway PC and RT PC, for commissioning and debugging as well as a useful storage drawer which provides storage space for sensors, manuals, spare connectors, current probes, accelerometers, cables, etc. used with the data acquisition for that axis.
There is a primary dynamometer encoder input, and additional DUT encoder input that can be synchronised with other channels for monitoring test inverter and motor performance.
The high-speed power analyser (PA) connection houses both the communications bus to the PA(s), and the high-speed current feedback, which is synchronised directly with other high-speed measurements such as torque, speed, position, and NVH.
Dyno bearing temperature inputs allow logical separation of test infrastructure temperature inputs, which can remain in place permanently.
The cell infrastructure and test equipment control are connected via dedicated buses.
Ports for high-speed data network sharing between control racks allows set points and values to be shared directly between primary control loops on up to five racks.
Harting connections to the Test Cell Management Control Unit, that manages the safety circuit integration, allows the racks to be connected into the test cell safety infrastructure, and also for multiple racks to be connected to the same safety circuit.
POWER ANALYSER RACK
Power Analyser Rack side panel removed
Housed in a rugged 24U 600W 600D (mm) rack the Power Analyser Rack contains three N4L power analysers and provides direct current feedback to the main rack FPGA for synchronisation to angular position. Direct programmatic communication with these units provides the power and accuracy of a benchtop power analyser, but with the convenience of viewing this information from the control room, and integrating the data into single time-aligned data sets.
CELL PATCH PANEL
Cell Patch Panel
Cell patch panels have been provided to allow quick and easy test set-up and connections to services and resources that are outside of the test cell. These are connected via rugged looms, that can be stored away when not in use to reduce the risk of damage.
TEST CELL MANAGEMENT UNIT
Due to the potentially dangerous nature of the tests being undertaken, the cell needs to offer full containment including safety management. The VEF already had a self-contained Test Cell for ICE testing, Austin Consultants were able to integrate the existing infrastructure via the Test Cell Management Unit (TCMU) which is based on an NI CompactRIO to provide deterministic, low-latency integration with the test Cell Control and Data Acquisition. The TCMU is responsible for controlling the existing Test Cell ventilation by communicating with the ABB Inverters that drive the ventilation fans. Replacement ambient pressure sensors were installed to allow the TCMU to have closed-loop control and maintain a negative air pressure in the cell.
The TCMU also controls the existing contactors for driving fire dampers and other auxiliary services and serves as a link between the existing safety circuit and the EVolution rack safety and new door interlock systems that Austin Consultants installed.
This reuse of much of the existing infrastructure resulted in a much lower overall cost.
SAFETY INTEGRATION
The system is integrated within the existing WMG rated safety system via the TCMU and has dual-channel inputs and outputs to prevent a single fault causing the loss of the safety function. As well as providing inputs into the safety system for software faults and alarms, the Austin Consultants team provided SIL3/PLd rated upgrades to existing safety systems to allow access control for the test cells via system keys, key exchange door locks and personnel keys.
Installation and Training
Following the completion of commissioning and installation, our team provided on-site training in operating the system as well as producing a video user guide that provides a step by step guide to the system configuration, operation and safety features.
Outcome
The flexible system is able to integrate with existing test cell infrastructure and equipment to maximise resource utilisation whilst at the same time incorporating the latest test cell features and requirements.
The software management layer provides safeguarding of equipment and people whilst providing easy-to-use workflows to guide both advanced system administrators and operators through the system configuration relevant to their level of expertise.
With the NI PXI platform and VeriStand engine at its heart, it is flexible and can accommodate new technologies and future demands. New sensors or bespoke protocols can be added via a simple low-cost, ‘plug-in’ upgrade.
- Maximised value from existing resource re-utilisation and increased extensibility to meet future requirements.
- Delivered savings through innovation and integration.
- Demonstrated return on investment on the cell transformation initiative to increase utilisation.
- Improved data management including access, use of data and quicker data analysis.
- Adaptable to accommodate new/changing technologies and test requirements.
- More effective use and reuse of technology.
- Enabling advances in engineering through design and build of innovative systems.
