Virtual testing methods and 3D simulations are becoming increasingly important in the development of industrial trucks

The smart glasses are in place and the image the engineer sees is sharp and clear. Wherever they look, the simulated panoramic 3D view represents the typical view seen by a forklift driver. They can see attachment components, the cab, and the mast and assess in a virtual test if the truck’s field of vision needs to be improved. This test is based on CAD data and provides a comprehensive simulation of the visual conditions from inside the cab of a Linde or STILL forklift truck—a test process which is now entirely virtual.

VR tools like these smart glasses and virtual testing methods are a huge help for the truck developers, and enable the engineers to check designs and approaches in real time. These tools provide clarity about whether the model will meet the requirements or not, long before the components or trucks go into production. It is an anticipatory tool and a process that reveals a lot about how much innovation goes into testing and KION Group’s development processes.

Anyone who read part 1 of our story on testing will recall the images of extensive test routes and real-world endurance tests that STILL and Linde forklift trucks are subjected to in Hamburg and Aschaffenburg during the development phase. The demands of testing methods like this in terms of materials, resources, and time are huge. However, in the future, virtual testing could become a permanent fixture alongside physical testing. Dirk Scharr, Vice President Product Validation & Testing, sees the situation developing as follows: “In the long term, we intend to replace time-consuming physical testing procedures with simulations, which will not only reduce costs but also yield results at an earlier point in time, thus shortening the overall development period.” The fact that this is even a possibility is, first and foremost, due to the fact that physical testing provides an abundance of data—and KION Group is making good use of this. The virtual tests that result not only bring huge potential for savings, they also have some very specific advantages over physical testing.

Picture the scene: a forklift truck doing its rounds and bumping over obstacles. But this time it’s without the usual loud noises echoing around cavernous warehouses. That’s because this is a digital twin, represented by countless geometrical, virtual elements. The calculation engineers’ screens show a simulation of a physical testing procedure, in which forklift trucks navigate obstacles on a virtual test track. During the test process, the program reads forces that could only be captured in reality using expensive physical sensors. This includes data relating to critical connection points between individual components. Virtual testing provides transparency where physical testing may not be able to.

However, transparency is far from the only advantage. Mohamed Ben Ayed, Head of Calculation/Simulation at KION, produces a paper clip to demonstrate another of these advantages. He uncoils the metal wire further and further and applies force to it in various places. “The material is wearing down,” he demonstrates. How much can it withstand? In order to figure this out, in reality, in addition to material, one thing above all else is required: time. Virtual stress and lifespan calculations help here as they enable lifespan requirements for components to be checked quickly, even if, for example, the material composition is to be changed. This is because this can be achieved by changing certain parameters, instead of having to rebuild components. All this significantly shortens the development process and conserves resources.

The development process relies on answering certain key questions: Will this concept work in real life? Can the materials withstand the stresses they will be exposed to? Answers to these questions are largely provided by stress and lifespan calculations. No measurement, no prototype construction—first of all, simulation engineers from STILL and Linde MH calculate the properties of the components. If their calculations and the results they provide are satisfactory, a prototype is then constructed. So, the concept phase is no longer a phase that is solely dedicated to identifying ideas: It generates valid data, which is indispensable in the development process. A good example of this is the Impact Drop Test. The picture should be familiar from part 1 of our series: extremely heavy bundles of wood are dropped onto the truck’s roof and provide clarity about the cab’s durability. However, instead of having to damage roof after roof, calculations are carried out in advance to determine the deformation of this component.

So, the job of a simulation engineer involves some detective work, i.e., finding out where the potential weak points in the materials are before they are used. This not only involves assessing external forces but also temperature distribution inside the forklift truck. CFD flow simulations are used in advance to ensure that the components do not overheat. This mainly affects ventilation within the trucks. Does the air conditioning function as it should? What temperatures occur and when? Virtual testing can provide answers to these questions.

Virtual testing is now also playing an important role in checking energy sources. The inner life of a lead-acid battery is not without its pitfalls: for one, hydrogen is produced during charging. If it is not properly dispersed, small, potentially dangerous accumulations of gas can form. The solution is to simulate the gas currents beforehand and test how they are distributed within the housing and how they escape. Different color densities show the gas concentrations, and illustrate the distribution and density. Incidentally, a similar process is used for the fuel cell: the cleaning processes within the energy source are also simulated in advance, exactly like the heat distribution within the lithium-ion battery. Thermal analysis is used here as it is essential that the energy sources don’t overheat.

All this shows that, in almost all phases of the development process, virtual testing now plays a pivotal role, and that trend seems set to continue. Does this mean that we will soon no longer see forklift trucks rushing around the test site or being placed on the lifting platforms? The answer, at least according to Mohamed Ben Ayed, is no: “The big challenge for us is to ensure we have validated models. Ultimately, the models we build need to adequately reflect reality. And this is not yet the case everywhere.“ A final, physical validation of the tests is therefore still essential and will remain so for the time being. This means we will continue to use the test track and the lifting platforms for some time to come, to ensure we achieve the best level of safety possible.