HiL Self-Test: Automatic validation of HiL systems

Hardware-in-the-loop (HiL) simulators have the challenging task of testing electronic control units (ECUs) for vehicles and ensuring their reliable functioning. The HiL systems themselves are correspondingly complex and are expected to provide highly accurate input and output signals for precise test results.

Validating the functionality of the HiL system before starting a series of tests is therefore essential and serves the purpose of quality assurance. In addition, the documented correct functioning of a test system is also relevant in connection with functional safety​​​​​​​ requirements. 

The HiL simulators from MicroNova’s NovaCarts family have various channels for electrical excitations and measurements. A self-test checks the function and compliance with accuracy of these channels. When validating ECUs, test automation solutions are usually used to increase efficiency, for example EXAM.

The same procedure is used to validate the HiL itself, offering the advantage that the self-test can be integrated into the test suites of the existing automation. This means it is a simple task for the user to add individual special tests.

• Quick test
• Limit value test
• Ramp test
• Full test
• Calibration test
• Qualification test

All tests included in the above validation scenarios can be performed separately or compiled into a custom configuration – depending on the desired focus and reporting.

The quick test checks the response of all channels installed in the HiL system and performs a back measurement of the control unit I/Os. This simple check of the basic functionality of the system allows the test operator to assess the readiness of the test bench. A quick test is usually carried out after ECU conversions or before tests with a very long runtime. Its focus is a quick statement about the basic system status.

This test extends the scope of the quick test by checking the limit values of the channel specifications. This means it takes longer, but in return is also more informative. Customizations can be implemented by MicroNova’s consultants or by the client.

The ramp test includes all checks from the quick test and limit value test. In addition to the channel limit values, the value range defined in the data sheet is tested with previously defined interpolation points. The required behavior of the slew rate of individual signals is demonstrated. Individual customer requirements, such as a lower bandwidth or resolution, can also be implemented here.

In the full test, the value ranges of the channels are sampled in full. This allows for a comprehensive test of the resolution and the slew rate. In addition, different signals are combined with each other in order to test and document any cross-influence.

The calibration test uses the information from the full test to generate as much data as possible for calibration of the HiL system under test. The extent to which this is possible depends on the available instrumentation and the calibration requirements.

The qualification test is the highest standard: It uses all tests of the validation scenarios described above. The result is an automatically generated qualification report that can be used to provide evidence in the assessment according to ISO 26262.

All the system tests mentioned can optionally be carried out with various measuring devices already available or included in the HiL system. If required, external measuring hardware can be connected via an additional interface to provide independent values.

The reports on the individual validation scenarios are generated automatically and stored in the customer’s respective test data management system, or they can be exported in various formats.