As vehicles are getting more complex as integrated mechatronic systems, approaches which are cross-disciplinary using simulation are now vital. Development processes need to be able to capture and understand all the permutations of each design change or choice, which cannot be easily discretised into singular studies, whether physical or virtual. Systemic interactions, and the ramifications at local and whole vehicle level, need to be understood.
Consider a modern automotive innovation: active aerodynamics. It is inherently multi-physics; control software triggers electrical automation of hydraulic systems, to change the aerodynamic profile of a component, which then impacts the thermal performance of the vehicle, as well as energy efficiency and the ultimate handling balance. Looking at one element of this system in isolation will never lead to a robust understanding of the full system dynamics.
Simulation; what is it?
Simulations of various kinds have long been an established part of engineering process to provide more detail and understanding of complex phenomena. Be it Finite Element Analysis (FEA), Computation Fluid Dynamics (CFD) or Multibody Dynamics (MBD), all engineers are familiar with the concept of Computer Aided Engineering (CAE). Traditionally, CAE has covered the targeted application of specialist techniques. Over the past decade however, the holistic term simulation has developed, covering modelling of the vehicle as a combined system. So, what does the term simulation mean in the modern context, and how is it revolutionising the way vehicles are being developed and built in the present day?
To really grapple with simulation as a concept, we first must consider what it is. At heart, it is describing the physical world in numerical terms, enabling the recreation of results from real world testing. Immediately, the dividend of repeatability and repetition can be grasped. But moving beyond that, the real benefit of full vehicle simulation is it enables engineers to ask, and answer, “what if” questions quickly and easily with models detailed enough to be predictive. Questions which would otherwise be impossible, or impractical, to answer.
In the 20th century, answering such existential questions to further understanding required decades of research to develop parametric analytical equations capable of providing an answer to “what if”, when a single parameter is changed. Even then, such analytical approaches are only of limited use in predicative studies, able to answer only the broadest of questions. Therefore, unsuitable to guide modern design decisions.
If the origins of simulation tools are considered, then the judgement of them as tools to understand the unknown makes perfect sense. Motorsport, such as F1 or NASCAR, are often cited as roots of complete vehicle simulation packages, as is the case of VeSyMA from Claytex. Such tools developed out of motorsport engineers needing to understand a rapidly changing and very complex collection of technological details and physical circumstances. All whilst physical testing options were being simultaneously reduced.
Utilizing the acausal Dymola simulation environment, complete vehicle simulation with VeSyMA provides an innovation over a traditional targeted CAE approach. Each physical or software component the vehicle is built from is modelled from first physics principles and combined into a full vehicle model. These simulation models therefore directly resemble the actual system they are simulating at an intrinsic physical level. Such an approach means if component models are validated correctly, then they can be inserted into full vehicle simulations and be used for predictive studies with confidence.
Evolving beyond a niche
As great as those benefits sound, the jump between simulation being a great idea in theory and a practical tool is quite a large one. F1 and NASCAR teams are minute compared to OEMs and Tier 1 suppliers. Regulatory oversight of final product and product development is also vastly reduced, as are the financial constraints.
But the reality is that simulation is an inherently flexible tool, adaptable for your specific needs. Not all simulation is the same, or for the same purpose. For instance, in motorsport, you would not use the most detailed fully compliant vehicle model for computing 10,000 strategy permutations the night before a race. Similarly, simulation for automotive applications can be adapted to specific roles within the existing development process, delivering benefits without needing to reorganise the existing deployment of labour.
Flexibility of simulation can be thought of as comprising of two opposite poles. At the one end, are simple, easy to parameterise, not overly detailed models; at the other are the most complex models, with all the detail possible included. All permutations exist between these two poles, with the detail level scaled to the specific function or job required. What provides the efficiency benefit is that both those poles are realised in the same package, sharing the same inherent architecture.
Rather than dealing with multiple packages or maintaining different legacy tools, VeSyMA can provide a core singular backbone of a simulation strategy, underpinning all aspects of vehicle system engineering. Detailed data from subject specific detail packages, such as FEA or CFD can be integrated into the core simulation package of VeSyMA. This then enables highly complex interactions between components to be modelled.
Have confidence in answering “What if?”
The effect of a design change, on say a cabin door insert can be understood in all aspects desired; impact of mass change on vibration response when driving over rough roads, impact of mass change on thermal performance of the cabin in various weather conditions, impact of mass change on vehicle handling, impact of mass and heating/cooling changes on vehicle range. All aspects which either would take painstaking time to run through various specialist simulation packages or require physical prototyping and testing.
Whole ranges of design specifications and permutations can be simulated at the push of a button, enabling the engineer to see the ramifications of design changes at a vastly quicker rate than with traditional targeted simulation tools. Individual component bench test simulations can be conducted alongside full vehicle testing. The unknown can be rapidly mapped by considering an extremely large number of permutations quickly.
Closing remarks
Being able to understand, map out the unknown and answer “what if” questions, is the advantage of using a simulation package such as VeSyMA. Ideas are liberated from the constraints of what can be tested and quantified in the physical world.
Written by: Theodor Ensbury – Project Engineer
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