Automated Virtual Test Driving

by Joseph A. Juricic

Originally printed in Vehicle Dynamics International Magazine - May 2004

Smart vehicles require smart testing methods. A smart vehicle, in this context, is one which is equipped with intelligent systems designed to improve safety, comfort and handling. When considering these vehicles and systems, smart testing methods which incorporate vehicle dynamics simulation, as well as Hardware/ Software/ Model "In-the-Loop" testing, have been shown to produce fast and accurate results, and to significantly reduce development time and project costs. However, while this type of simulation testing, referred to as virtual test driving, is a significant time and resource saver, it still requires an engineer to be present and to manually operate the system. Test automation solves this problem. It can be used to run any number of predefined tests - unaided and unattended. Automating the testing processes minimizes the time and effort required by the testers, which allows them to focus on other important engineering tasks, and replace manual testing methods with a predefined, efficient and more systematic approach.

For this type of simulation testing, IPG Automotive's CarMaker vehicle dynamics and In-the-Loop simulation environment is currently being used by many OEMs and suppliers who produce intelligent, as well as traditional, vehicles and systems. In fact, one group from PSA Peugeot Citroën, the successful and innovative French automaker, has been using virtual test driving and simulation methods in their development process for a number of years, and recently started using IPG's test automation tools in an attempt to increase productivity. The improvements PSA observed with automated virtual test driving and simulation were impressive, reducing the testing time from two months to only two days.

The PSA engineers using CarMaker focused on testing stability and traction control systems. Their aim was to use automated testing to perform overnight, or "lights out", testing by executing a series of approximately 300 standard simulation tests and generating a report based on the simulation results. Once the IPG test automation tools were installed, PSA was able to achieve this goal. Each night the tests were started and every morning the results were made available - nicely formatted as HTML - on the department's Intranet site.

"With a real car it would take two months to perform the tests. With In-the-Loop testing it was reduced to two weeks. Now, with fully automated simulation testing, it only takes two days. The results are impressive." J.P. Nivoix, the PSA chief project engineer, stated.

The first requirement when automating dynamic control systems testing is to use an effective In-the-Loop simulation system. The CarMaker system not only includes the necessary vehicle environment models and I/O interface mechanism, but also comes with many advanced tools to view, control and analyze the simulation and to process the simulation results. It is also possible to use the tightly coupled Matlab/Simulink interface to run, control and analyze the simulation.

All maneuvers that can be driven in the real world can be simulated in the CarMaker virtual vehicle environment. This includes simple open-loop maneuvers, such as braking on a straight track, all the way to complex closed-loop race driving on digitized race courses, such as Hockenheim, LeMans or the Indianapolis Speedway.

Once the simulationenvironment is chosen and validated, the next step is to go beyond interactive testing only. This is where the real benefits of using a computer become apparent. By using a computer to simulate the dynamic interaction needed by the controller under test, the testing process can be fully automated.

Figure 3 shows an example of an automatically generated simulation test report resulting from the automated execution of a predefined simulation test sequence. In this case, the simulation test sequence includes, among others, a double lane-change, lateral transient response and sensitivity to sidewind maneuvers. The dynamics are compared for a car with and without stability control, and the results displayed as an HTML document with hyperlinks to the more detailed information. Clicking on the hyperlinks opens the summaries of the individual simulation tests and displays the important information for the respective test. The report is automatically archived so that the entire simulation test process and results can be reviewed as needed.

The importance of using test automation can also be seen when a project requires modifications to the parameters in the control algorithm or vehicle model. Test automation only requires the user to press a single button to run all the predefined regression tests, verifying correct vehicle or system behavior. In addition, when the latest version of a controller is delivered from a supplier, test automation enables the execution of predefined release tests to automatically check if the system behavior is still correct.

With test automation the user can systematically investigate, evaluate and optimize the behavior of the system, not only with different vehicle variants but also by using any number of specifically tailored maneuvers. Working manually, as opposed to automatically, takes more time and is, in general, less systematic. Using test automation lets the user define a systematic test process with an appropriate structure, which leads to increased test depth, test breadth, test coverage and more trusted quality claims. In addition, once different simulation test sequences have been defined they can be used throughout the development process, beginning in the early phase of algorithm development and finishing with controller validation for the production run. This is possible because the simulation tests can be managed and test libraries generated and reused, not only in different development phases but also in different projects.

Having used the CarMaker test automation and simulation environment developed by IPG Automotive, PSA was able to reduce their testing time from 2 months to 2 days. As companies push to increase productivity, decrease project costs and reduce development time, a few methodologies will emerge and enable those who embrace them the best chance to succeed. In a dynamic world, simulation and test automation are methods worth adopting, and with CarMaker, success is closer than ever before.