French construction machinery manufacturer uses Simcenter Amesim to develop first electric wheeled excavator

Innovation comes to light

The Paris city council adopted the Territorial Air Energy Plan in 2018 to reduce pollution, protect its citizens’ health and fight climate change. Through this plan, Paris hopes to be a carbon neutral city by 2050, and before then expects to be diesel free by 2024 and rid of gasoline engines by 2030.

Cognizant of these ambitions, the Mecalac Group (Mecalac) has designed and built machinery to align with the city’s clean air desires, with the Mecalac e12, an innovative, fully electric wheeled excavator, representing the company’s shining jewel in that initiative. Unveiled at the INTERMAT 2018 trade show, the Mecalac e12 earned the event’s Energy Transition Award, which recognizes technological and environmental performance.

“We have reached what we consider to be a crucial milestone with the launch of the first 100 percent electric excavator, which will help attain the zero diesel objective by 2024,” says Max Boni, research and development director, Mecalac. “With zero emissions of carbon dioxide and other harmful pollutants, this new excavator heralds a new era in Mecalac’s history. It ties in perfectly with our innovation strategy for urban work sites that are increasingly compact, high performance and environmentally friendly.”

Three major design challenges, one breakthrough innovation

To develop its electric excavator, Mecalac defined an optimal architecture to meet three underlying requirements: range, performance, and compactness. To accomplish this, accurately sizing the battery was a primary challenge. This meant solving a difficult equation with a number of parameters, but one that was attainable.

“For us, this was about developing an initial working prototype while anticipating future serial production,” says Thomas Schaep, mechatronic systems engineer, Mecalac. “We were not looking for a specific, tailormade battery solution. Instead, we sought to combine off-the-shelf battery modules while optimizing the machine’s overall range, cost and footprint.”

Selecting Simcenter Amesim

To research its new electric excavator model, Mecalac’s research and development (R&D) team sought to adopt a modeling and simulation solution capable of analyzing and predicting system performance on the mechanical, hydraulic, thermal and electrical levels.

The company chose Siemens Digital Industries Software’s Simcenter Amesim™ software for its ease of use, openness and extensive range of readyto-use multiphysics libraries. Schaep was familiar with the solution and ready to use it. The modeling phase was completed in a three-step process and lasted approximately three months.

The first step was mechanical modeling, where the dimensions taken on the 2D plans were fed into Microsoft Excel spreadsheet software. The synchronous, two-way connection between Simcenter Amesim and Excel used the values entered in it as the simulation parameters for Simcenter Amesim. When/if these parameters are changed in Simcenter Amesim, they are automatically updated in Excel, allowing both data sources to update simultaneously. This method allows a larger number of users to use the information in Excel without having familiarity with Simcenter Amesim. In addition, the computer-aided design (CAD) import function in Simcenter Amesim makes it possible to automatically generate the kinematic/mechanical model of the excavator in just a few clicks from any CAD file.

Hydraulic modeling was the next step in the process. Hydraulic distribution is modeled using super components and is continuously repeated. Considering the high cost of hydraulics for construction equipment, this step required very granular, detailed modeling. To ensure the model’s optimal representativeness, the results obtained by simulation were compared with real, physical measurements. An approved correlation was observed.

The final step was electrical modeling, where a detailed model of the permanent magnet synchronous motor (PMSM) is associated with its controller, an inverter and the battery.

Creating a first time right prototype of the e12

Using the Simcenter Amesim model, Mecalac simulated various architecture options and analyzed multiple parameters to size the electrical power system and produce a first time right prototype. This represented a significant gain in terms of cost and time. In fact, Mecalac believes that without Simcenter Amesim they would have needed two or three prototypes to create an optimized architecture in terms of range, performance and congestion.

“The Mecalac e12 battery offers a record capacity of 146 kilowatt hours with an unequaled range duration of 8 hours and possesses a battery life three times greater than that of conventional batteries,” says Boni. “These performances were widely acclaimed by professionals at the INTERMAT 2018 trade show.”

A creativity boost

Simcenter Amesim made an immediate impression on Mecalac’s R&D department through its ease of use and rapid implementation thanks to its proven libraries, easy adoption and robustness.

“We now have a better understanding of certain phenomena such as energy losses, where previously we were unable to quantify something like that; now we can put our finger on it,” says Schaep. “We can quickly perform several simulations with a high level of confidence as to the predictability of the models. This frees up time to examine more creative solutions and devise options which we would not otherwise have had time to explore. In short, Simcenter Amesim boosts our creativity.”

An open door to new concepts

Mecalac is already using an advanced version of the Simcenter Amesim model as it works on the e12’s serial production phase. In fact, the engineering department plans to combine the Simcenter Amesim model with control law models to ensure proper behavior. The next step for this Simcenter Amesim model will be to validate the battery’s cyclic and calendar aging. Finally, the use of an optimization solution such as HEEDS™ software from Siemens Digital Industries Software will help automate and accelerate the design exploration process.

“Simcenter Amesim allows us to proactively explore new innovative designs,” says Boni. “This first study with the e12 is like a suggestion box to trigger new ideas for future developments. We are very much a source of proposals for the marketing and purchasing teams.”

This approach keeps with the genesis of the Mecalac Group which, for the past 40 years, has adapted to the needs of the urban work sites of the future and provided innovative solutions.