Figure 1. WTI developed a flexible HIL system able to test and simulate real-world conditions for many types of Lear automotive ECMs.
Designing a hardware-in-the-loop (HIL) test system flexible enough to test multiple types of automotive electronic control modules (ECMs) and capable of scaling to future products.
Creating a custom test automation platform – based on National Instruments VeriStand real-time testing software and a combination of multi-vendor test equipment – that provides expanded module capabilities, increased testing throughput, and higher precision results.
“We selected WTI as our HIL test system partner because of the flexibility and superiority of their test control software environment. The WTI HIL tester allows us to completely validate our modules in less time and with higher reliability than our previous system.”
– Jason G. Bauman, Lear Corporation - Electrical & Electronics Division
At Lear Corporation, the Electronics division designs and produces ECMs that control the many electrical systems in a motor vehicle, such as sound systems, door locks, and interior lighting. Given the wide variety of signals and communication buses in an ECM, testing these components is complex and involves analog and digital signals, pulse width modulation (PWM), CAN, and LIN. An HIL test system uses these signals to simulate the ECM’s environment in a vehicle, and then evaluates the ECM for proper responses to different situations.
Integration into a Single Test Software Platform
To provide a lifelike environment, the tester and its software must possess great flexibility in deterministic signal generation and acquisition, real-time model execution, real-time fault simulation, and pass/fail analysis. We selected the NI VeriStand control and simulation software because it met all of these requirements in a single, off-the-shelf package.
Our system uses both NI PXI and CompactRIO platforms, which NI VeriStand natively supports in its System Explorer configuration utility. To add non-NI hardware such as the Pickering programmable resistor card and Gopel LIN cards, custom drivers were written in NI LabVIEW code and integrated into the NI VeriStand environment to create a cohesive and flexible test system.
Figure 2. The hardware set-up includes a real-time controller, FPGA reconfigurable I/O, data acquisition, and vehicle network interfaces.
Extensive I/O and Bus Configuration
The HIL test platform provides over 200 digital, 80 analog, and 32 PWM I/O points, along with 4 CAN buses, 2 LIN buses, 64 fault insertion channels, and 10 programmable load channels. To expand the functionality of the system beyond the standard I/O interfaces, we used custom FPGA personalities on NI reconfigurable I/O boards to implement user-definable analog and digital channels, 200 kHz function generation, and control of WTI’s fault insertion chassis.
CAN and LIN both are popular communication protocols used by ECMs to communicate with the many different components in a vehicle. For CAN bus communication, the application required the ability to monitor CAN traffic, compose and send CAN messages, manage fault CAN messages, as well as view and log all raw CAN frames. We used the CAN database import utility in NI VeriStand, along with NI-XNET vehicle bus cards, to meet these requirements of rapidly configuring, reading, and updating the unit under test. The system automatically decodes each CAN message into its component channels and has the ability to programmatically and deterministically enable, disable, or trigger the message.
Real-time script or procedure execution is another important capability during the configuration of the HIL tester. We used a National Instruments (NI) PXI-8106 real-time controller with deterministic timing to control most aspects of the system. Scripts were created to monitor safety limits and, in the case of system failure, to disconnect I/O, disable the main breaker, and command control voltages to zero. These text-formatted scripts are completely generated via dialog boxes and user selection, so minimal programming knowledge is required. For future updates to the system, the software also provides extensive real-time calculations, alarm monitoring, and model execution capabilities.
Powerful HIL Testing and Analysis
A flexible graphical user interface (GUI) environment for the HIL system was needed to quickly and easily adapt to the various devices under test. Using the NI VeriStand dynamic user interface environment, controls and indicators ranging from simple numeric to automotive-style gauges and graphs can be placed on any one of the user windows during run-time and then linked to any channel in the system.
Figure 3. The flexible GUI allows controls and indicators to be added during run-time.
To test the ECM with the HIL system, a variety of analog, digital, CAN and LIN profiles are generated and the ECM’s responses are compared to the expected results. We also use fault channels to force signal values that simulate a failure in the system and then monitor the reaction of the unit under test to that failure. The test profile editor compares the ECM’s response signals with the expected value at each specific time interval until all the values have been evaluated. The test editor also provides special entries for faulting channels and for performing real-time pass/fail analysis on response signals.
For pass/fail analysis, the HIL software implements a real-time windowing function that can track a signal. The upper limit, lower limit, and time lag parameters are combined to form a window for the desired response around a particular signal. For example, between 0.42 and 0.56 seconds into the test, the ECM is expected to output a certain PWM input signal at 0.1 ±0.01 V with a maximum of 50 ms lag, and the test software analyzes all of these parameters to evaluate the ECM’s performance. The pass/fail engine also includes settings for recording any failures that occur, such as the maximum number of failures and whether or not to record pass and fail values.
Conclusion – HIL Testing for Today and in the Future
Designing a flexible, powerful HIL test system presented many challenges, including diverse I/O requirements, multiple industrial communication buses, real-time stimulus generation, signal faulting, and real-time pass/fail analysis. We addressed these challenges by using NI VeriStand software coupled with a multi-vendor mix of data acquisition and control products. The resulting HIL tester provided a system capable of performing the required testing on the customer’s current control modules, as well as enough flexibility for testing future products. With this solution, the customer’s testing capabilities: