Setup of the Cruden DIL simulator. Picture credits: Cruden
Hardware-in-the-loop (HIL) simulators play a crucial role in automotive research and development. OEMs, suppliers, and the academic institutions use them extensively to test sensors, controllers, actuators, and parts in the lab as if the vehicle was being driven on the road or track. However, engineers can achieve even more accurate and relevant results by combining the HIL test rig with a driving-in-the-loop (DIL) simulator. To have a human driver allows for subjective scoring methods to support subjective-objective assessments.
HIL setups often rely on synthetic or prerecorded input signals that lack the typical closed-loop behavior of a human driver. DIL simulators, on the other hand, have interactive drivers but might not provide precise models of the actual hardware, because specific components are too complex to be simulated in full detail. Another reason might be that controllers have many unknown variables, because suppliers provide them as black boxes. Merging HIL and DIL helps eliminate these shortcomings and can be achieved relatively easily when combining a Cruden DIL simulator and a dSPACE HIL set-up that includes the open and real-time capable simulation tool suite ASM (Automotive Simulation Models). An additional advantage is the ability to integrate peripheral hardware (such as instruments or other HMI equipment) via standard interfaces, for example, CAN.
To make this integration a success, the core of the simulation has to run in real-time. In other words, simulated time steps have to be very well synchronized with the real-world time steps. An ECU expects precisely timed updates from, for instance, the vehicle state. Test rigs are also not very forgiving if the next setpoint update is received later than expected. dSPACE is the leading producer of engineering tools for developing and testing mechatronic control systems. The product portfolio includes real-time systems used by most international OEMs and suppliers. “dSPACE essentially allows you to integrate any piece of hardware into a DIL simulator,” highlights Martijn de Mooij, technical development manager at Cruden. “Our new solution combines Panthera’s open architecture and flexibility with the almost unlimited hardware interfacing capabilities of dSPACE systems to create the ultimate development and testing system.”
The idea for this quick and simple integration came from Professor Liu-Henke of the Ostfalia University of Applied Sciences. She used a Cruden driving simulator together with a dSPACE real-time simulator and the ASM simulation tool suite. The university wanted its students to have the possibility to integrate hardware with a driving simulator. This has now been achieved thanks to Cruden’s and dSPACE’s solution.
To effectively integrate a dSPACE system into a DIL simulator, the only required hardware change is to replace the conventional Windows-based computer (which sends output to the motion, audio, and visual systems) with a dSPACE system. “dSPACE hardware running ASM becomes the third point in a triangle where it has direct communication with the motion system and our Panthera Master software, which is the main simulation engine,” says Martijn.
Cruden’s Panthera ePhyse HRT includes a Simulink blockset that targets the dSPACE system. It is an integrated solution to set up I/O interfaces between the dSPACE platform and the simulator environment. Initializing the simulator session is as simple as selecting the ASM model of choice and clicking a start session button in the user interface, which activates all relevant subsystems in the setup.
“We have worked hard on the usability of this system. We haven’t proverbially duct-taped the motion system to the dSPACE box, we have ensured seamless integration throughout the entire system,” continues Martijn. “Before, companies would have to buy a simulator and then buy an off-the-shelf dSPACE system and integrate the two. We’ve done all the hard work for them to provide a complete functional setup that works straight out of the box.”
System setup of the DIL simulator at the Ostfalia University. Picture credits: Ostfalia University
Ostfalia University of Applied Sciences uses the dSPACE-Cruden system for both educational and research purposes within its Mechanical Engineering department and Institute for Measurement and Automation Technology. The development cycle of any mechatronic component consists of three main stages: model in the loop, software-in-the-loop, and hardware-in-the-loop simulation. “For us, there was a gap because the driver is not involved in any of these three stages,” highlights Marian Göllner, research assistant at the Ostfalia University of Applied Sciences and member of Professor Liu-Henke’s research group for control engineering and automotive mechatronics. “We feel that the only way to achieve a complete and valid simulation is to receive the driver’s feedback throughout the development process. To do this, we purchased a Cruden DIL simulator, which now represents the fourth and final stage of our simulation cycle.”
In addition, the university uses the simulator in another non-traditional way. By changing the simulator’s top platform with an interchangeable driver cell supplied by Cruden, the simulator can also be used for frequency domain tests.
“Thanks to the open controller environment of the simulator, which allows us to manipulate every setpoint of the motion platform, we can use the electric linear drive to generate controlled harmonic vibration. This can then be used to measure the response of the system in the frequency domain.”
DIL simulators are increasingly being used for the final stages of the ADAS controller development process, where an essential step is observing and optimizing the interaction between humans and cars, for example, for Level 3 autonomous driving handover moments.
The Panthera ADAS Toolbox allows for easy integration with the traffic module from ASM and feeds Simulink-based controllers with environmental awareness that either comes directly from ASM Traffic via the Panthera interface or links to dSPACE MotionDesk sensor simulation.” Controller action can be directly fed back to the ASM model or to the driver by using actuated controls, the instrument panel, the audio system, or any available system.
Cruden engineers have combined their in-depth understanding of the entire simulator environment with their knowledge of HIL simulations to achieve a fully integrated solution. Their extensive experience of building complex vehicle models whilst maintaining the usability of the overall system has allowed Cruden to develop a fit-for-purpose simulator. By using all these skills combined under one roof, Cruden’s efficiency supports customers to get up and running quicker. Thus, they can start development testing sooner to receive the all-important driver feedback faster.
Martijn concludes: “Cruden’s focus is to develop simulators, so its customers can focus on their own job. Too often we see engineers who should be focusing on developing cars struggle to do their own integration work as they are trying to combine various systems into one test rig. This is what we specialize in. We can provide you with a better test rig in less time, allowing you to actually work on the vehicle.”
The dSPACE simulation platforms are dedicated to development and test tasks with strong real-time requirements and low latencies. The hardware is a combination of powerful processors with flexible I/O solutions. On these hardware platforms, the Automotive Simulations Models (ASM) from dSPACE offer a realistic representation of real-life events. In the context of driving simulations, ASM realistically represents the dynamic behavior of a vehicle within a certain environment. The environment ranges from roads with changing conditions, such as rain, snow and ice, to complex traffic scenarios with a multitude of vehicles at different speeds and trajectories. Thus, ASM is the perfect choice for developing and testing controllers for ADAS and autonomous driving.
Real traffic scenario simulation with the Automotive Simulations Models (ASM) from dSPACE. Picture credits: dSPACE