The transportation industry is continuously evolving, incorporating advanced technologies to improve efficiency, reduce costs and minimize environmental impacts. One key technological advancement is Model-in-the-loop (MIL) testing, a process that is revolutionizing how engineers approach engine development and testing. This article explores the concept of model-in-the-loop testing and dives into the various benefits as well as challenges. 

What Is the Meaning Of Model-In-The-Loop Testing?

MIL testing is a simulation technique used in all stages of a product’s controller development cycle. It involves testing a controller model at the component, composition, or system level within a simulation environment, before downloading the code into a physical Electronic Control Unit (ECU) and testing on a vehicle. Imagine you are designing a smart algorithm for trucks that helps them automatically adjust their speed in traffic. Now, before you commit the algorithm to code and put it in a real truck, you want to make sure it works perfectly. That is where model-in-the-loop testing comes in.

MIL testing is like a virtual practice for your product or system. So, instead of testing controller algorithms directly in a real truck, you create a computer model of your smart algorithm for trucks and simulate different driving situations on a computer. For example, if you were developing advanced adaptive cruise control systems for trucks, MIL can be particularly beneficial in simulating a model of the cruise control system in virtual driving environments. This will allow engineers to evaluate its performance when encountering real-world scenarios like changing traffic densities and weather conditions. This allows for early identification and resolution of potential issues, ensuring the system's safety and efficiency.

By integrating MIL into the development process, engineers can gain valuable insights into the system’s behavior early on, allowing for timely error detection and correction. This will lead to reduced development time and development costs along with an overall better product. Employing MIL testing streamlines the development process, enhances reliability and reduces the need for extensive physical road tests, offering a cost-effective solution for improving crucial trucking technologies.

Difference Between Model-In-The-Loop Testing vs Software-In-The-Loop Testing?

When understanding MIL testing, it is also important to understand software-in-the-loop (SIL) testing. In SIL testing, we check if the software that controls the smart algorithm behaves as it should without downloading the code into a physical ECU and testing on a vehicle. However, in this case, the focus is more on how the software reacts and makes decisions, which is a step closer to the real-world environment.

So, continuing our truck example from model-in-the-loop testing, imagine you have the software that controls the adaptive cruise control. Instead of testing it in a virtual truck, you run it on a computer to see if it behaves correctly. You create a simulated environment where the software thinks it is in a real truck, dealing with traffic and adjusting speed accordingly.

SIL testing is like making sure your video game character (the software) moves the way you want it to without worrying too much about the details of the virtual world (the truck and its surroundings). Engineers use SIL testing to check if the software can handle different situations and scenarios in a controlled, computer-based environment.

In our trucking example, SIL testing would involve running the cruise control software on a computer and observing how it responds to simulated traffic changes. It is a way to make sure the brain of the system (the software) is working correctly before putting it into a physical truck.

In summary, MIL testing looks at the controller in a virtual modelling environment to ensure that the algorithms function properly, while SIL testing is a step closer to the real world by zooming in on the generated software from those same models but still tested in a simulated world to ensure the controller behaves correctly.  Both methods are part of the chain of development in making sure the actual controller on the truck is safe and efficient.

How Can Model-In-The-Loop Testing Reduce Environmental Impact?

MIL testing has benefits associated with the environment, efficiency and reliable testing that ensures safety and quality in testing. 

MIL testing can help reduce reliance on test cells: 

The adoption of MIL testing significantly reduces the reliance on physical test cells. A test cell is a controlled environment used for testing the performance, durability and emissions of engines, vehicles, or other components. This environment is designed to simulate real-world operating conditions in a repeatable and consistent manner, allowing engineers to conduct precise measurements and make performance adjustments. A test cell typically includes equipment for measuring power output, fuel consumption, exhaust emissions and other critical performance metrics. 

MIL testing does not completely do away with the need for test cells, but significantly shortens the time and resources needed in these environments. Tasks such as OBD-tuning, optimizing and data analysis, which have been conventionally done in test cells, can now be performed virtually. This shift from physical to virtual testing environments is not just a matter of convenience but also a stride towards environmental sustainability.

MIL testing can be better for the environment: 

The environmental advantages of MIL testing are notable. First, it reduces the need for fuel consumption associated with test cell operations. By conducting tests in a virtual environment, the frequency and duration of tests in physical test cells, which involve burning fuels and consequently emitting greenhouse gases, are significantly decreased.

This efficiency contributes to a smaller carbon footprint, aligning with global efforts to reduce carbon and greenhouse gas emissions and combat climate change. Additionally, MIL testing is highly scalable, meaning that it can be adapted and expanded to meet the growing demands of modern automotive testing without creating negative environmental effects.

Challenges with Model-In-The-Loop Testing

MIL testing needs physical hardware: Despite its numerous benefits, MIL testing is not without its challenges. One primary concern is its validity as it cannot be relied upon entirely in isolation. Physical hardware testing remains an essential part of the development process to validate the findings of MIL testing. This requires a balanced approach to testing components, integrating both MIL and traditional testing methods.

MIL testing might require substantial investments: Furthermore, implementing MIL testing requires substantial technical resources. This investment includes not only the initial setup but also the ongoing maintenance and updates necessary to keep the simulation environment accurate and relevant to the ever-evolving automotive and transportation technology landscape.

MIL testing represents a significant leap forward in automotive testing and development. By allowing engineers to simulate and analyze components in a virtual environment, it offers a more efficient, cost-effective and environmentally friendly approach to vehicle and component development. 

Cummins Inc.'s adoption of this technology reflects its commitment to innovation and sustainability, aligning with broader industry trends towards cleaner and more efficient technologies. While challenges exist, the potential of MIL testing to revolutionize engine testing while reducing environmental impact is undeniable. As the transportation industry continues to evolve, technologies like MIL testing will play an increasingly pivotal role in shaping a more sustainable and efficient future. Cummins is dedicated to developing next generation technology for our customers.