Alma Automotive has been in support of Ducati Motor Holding for over twenty years, developing calibration and control strategies and conducting test activities for motorsport engines.

Ducati Motor Holding has found in Alma Automotive a solid technical partner to embrace the new challenges of global mobility. Over the past years Alma Automotive has gained extensive expertise in electrification, thanks to significant investment in research and development with a particular focus on dedicated testing solutions for electric vehicles.

With the ability to internally develop control and test equipment, power electronics and hardware-in-the-loop (HIL) systems, the group can support manufacturers in the full development and testing of hybrid, electric, and traditional powertrains. The availability of internal test cells and collaboration with qualified engineers allow Alma Automotive to be a comprehensive partner in supporting the most innovative powertrain development activities.

#Thermal Modelling

Battery pack performances are widely affected by the temperature of the cells. It is basically all related to their chemical and physical nature. Moreover, cell temperature relies on several factors such as cell internal resistance and cell heat exchange.

An accurate battery pack thermal model implies a deep knowledge on thermo and fluid dynamics of the system components, not only inside the battery but also in all the sub-systems working with the heat transfer medium.

The figure below shows the results of an experiments carried out during our validation activities of a racing electric powertrain with a liquid cooled battery pack. Cell and coolant temperatures are modeled with a maximum error of ±1.5°C.

Model inputs:

• battery cell thermal model calibration;
• vehicle speed;
• electric motor torque;
• thermal management system (air cooling, heat pumps or customer based cooling system).

The model is able to simulate the temperature of each cell inside the battery pack, keeping the computational effort low, and allowing the use of the model even in Real-Time applications. The model is flexible and easily tunable to cover the whole range of thermal management solutions.

#Voltage Modelling

Compact models with accurate results is the main goal we aim to accomplish.

In this case, a brief comparison between simulated battery pack voltage and State of Charge with experimental data is shown. Our battery pack model is an easly tunable model that can be used to simulate the electrical performances of HV battery packs composed with different Li-ion cell types.

Thanks to several calibration activities, our model allows us to simulate the battery pack voltage with a relative error lower than 1% with respect to the experimental data and the battery State of Charge with an absolute error even lower than 1%.

The variety of applications in which the model has been deployed enables us to check simulations reliability and precision, verifying the goodness of the results in 800V automotive powertrains architectures and many other.

What distinguishes us from existing solutions:

• Precision and flexibility;
• Complete emulation of electrical and thermal flows;
• Ability to drive any power supply on the market.

Alma Automotive provides electrified test cells and its expertise to offer testing services dedicated to electric powertrains. Our test engineers are ready to supervise the tests and create accurate reports at the end of each one, following the customers in every step.

The company has developed a model capable to perfectly simulate the battery pack, starting from the characterization of the cells used or supposed to be used. The system can emulate the electrical and thermal behavior of the device under test. Having the ability to drive power electronics from several suppliers, our system is very flexible and accurate. The common 600V DC bus is used to drive a 200kW battery emulator up to 1050V.

The electric machine to be used as a dynamometer is chosen according to the specific needs of the test: this can be supplied directly from the Borghi&Saveri catalog or purchased ad hoc from our selected suppliers.

Various tests can be performed for the characterization of the electric powertrain, including:

• Performance verification of the electric motor in specific operating points and in regeneration/brake mode
• Motor electrical check and Back EMF (before and after the test)
• Performance characterization of the electric motor in various operating modes (locked rotor, regeneration, max torque)
• Endurance, duty cycle and speed test
• Complete inverter calibration

Each test cell is equipped with an acquisition system based on the National Instruments platform, featured with temperature, pressure and accelerometer sensors. The test management system can directly or remotely control every component of the test cell, such as ventilation, power supplies, safety systems and it can digitize any type of test cell transducer.

Thanks to our custom-made thermal management system, we are able to simulate and reproduce the thermal management of the electric motor and inverter. We are able to perform motor and inverter tests by managing the coolant temperature in real time, emulating the temperature profile that would actually occur in the driving cycle or by testing the components at a desired temperature.

The system installed in the test room allows to the mechanical characterization of the system, by measuring:

• Torque and cogging torque
• Speed
• Vibrations
• Temperatures
• Flow rates and pressures (H2O/Glycol cooling system)

Drag tests can be conducted to measure mechanical losses and we are able to electrically characterize the system under test, using precision power analyzers.

• Accurate measures of efficiency
• AC/DC Current and Voltage measurement
• Motor winding resistance

We can also supply our Predictive Maintenance tool to determine deviations from healthy conditions of the device under test in working conditions.
The A.I. based system uses input data to estimate expected indicators levels (plant model) and then compares them with actual indicators intensities. The approach can be extended to estimate the remaining useful life or optimal maintenance intervals.