Overview of the Car-in-the-Loop concept


Mechatronic systems are one of the biggest drivers of innovation in automotive engineering. During the last decades, various mechatronic systems in the field of powertrain, chassis or car body have been successfully introduced in series vehicles. In the early development phase of such mechatronic systems, hardware-in-the-loop is a well-established method.

To this time point, different control units are tested in component test bench individually. The following development phase and accordingly the calibration work are mainly performed with the vehicle in test terrain or on road.

Nowadays, with the constant development of advanced driver assistance systems, the focus on autonomous driving and the stricter regulation on vehicle emission, the complexity of mechatronic systems in vehicle is increasing significantly. At the same time, the automobile industry sees a demand for more vehicle model variety and a shorter vehicle development time. In this respect, it is necessary to establish a model-based development process and front-loading the development work from vehicle to earlier development phases. Since tests with the vehicle in test terrain are expensive and effort for correction is extremely high. To close the gap between the component tests and tests with the vehicle in test terrain, one needs test bench that allows the testing of function and interaction of various mechatronic systems in longitudinal, lateral and vertical freedom degrees on complete vehicle level under realistic driving situations. This is the main motivation to develop the so-called Car-in-the-Loop concept.

The Car-in-the-Loop test bench is a further development of today's experimental set-ups. The most important part of the research lies in the development of control strategy and the reproduction of realistic driving situations, in other words, coping with the complexity of test bench system due to the consideration of longitudinal, lateral and vertical dynamics. The concept has to be proved with a physical prototype. Based on that, methodology should be developed for quick set-up time in the sense of change of test specimen, adaption of control strategy and project take-over from other development phases. To achieve this, the Car-in-the-Loop test bench should be modularized, have the capability of automated system identification and needs to be coupled with integration platform in closed-loop. Test automation and easy integration into existing test bench are other two important features. By this means, it supports the model-based development process and allows for a front-loading of vehicle development work. It is attractive especially when simultaneous engineering is required to shorten the development cycle time.

The application of Car-in-the-Loop covers a wide spectrum in the development of mechatronic systems. To name a few:

  • Front-loading of mechatronic system calibration from vehicle to test bench
  • Study of interaction between various mechatronic systems in different domains (powertrain, chassis, steering etc.)
  • Fail-safe testing of innovative driver assistance systems and self-driving vehicles
  • Investigations on the energy consumption of hybrid or electric vehicles by replicating different routes with consideration of active steering and active chassis
  • Analysis of driving emission with consideration of lateral dynamic

Current Development State:

  • Thorough system modeling and dynamic analyse
  • Quarter-vehicle prototype (see also the video below)
  • Validated vehicle simulation model capable for real-time application
  • Validated control strategy benchmark for longitudinal and lateral dynamics (see also the video below)

Current Research Focus:

  • Validation of control strategy of vertical dynamic on extended quarter-vehicle prototype
  • Closed-loop coupling with virtual vehicle prototype to achieve universal environment in development process
  • Development of methodology for adaptive control strategy based on automated system identification
  • Software and hardware modularization for easy integration into existing and future test bench

The current state of development is described in the following videos:

This video shows a sinusoidal steering movement of the demonstrator.

This video shows the illustration of a highly dynamic test drive on the demonstrator. The software CarMaker was used for the real-time simulation of the Mini Countryman.