Electric vehicles (EV) and electric drive design are all the rage these days, but do you ever wonder what motivates drivers to purchase one? The top three reasons why people buy an electric car over a conventional gasoline car are:

• No pollution with zero emissions compared to gasoline car toxic emissions
• Lower maintenance costs
• Electricity is still cheaper than gasoline

These reasons are causing an increase in the interest of electric vehicles. According to some research, there’s been an 18% growth in searches for the term “hybrid” and a 20% spike in “electric vehicle” searches globally during the first six months of 2020, compared to 2019. Electric Vehicles, which accounted for 2.6% of global car sales in 2019, saw a 40% increase over the 1.9% share in 2018. Companies like General Motors and EVgo recently announced plans to add more than 2,700 new fast charging stations over the next five years in an effort to accelerate widespread electric vehicle adoption.

Electric vehicles have an electric motor instead of an internal combustion engine. These vehicles have large battery packs which are typically mounted under the car floor. As it runs on electricity, the vehicle does not emit exhaust gas. The centerpiece component of the EV is an electric drive which consists of an electric motor, battery pack, power modulator and control system, which controls the torque and speed of car as per the load requirements.

The competition among electric motor manufacturing companies is fierce. They are all trying to provide an optimum design in a short span of time to launch new EVs in the market. For this, it is very important to reduce the overall design cycle time for an electric drive and this is one of the biggest challenges Electric Drive Design Engineers are facing today.

So let’s design an electric car with:

• Driving range of 440 km!
• E-Drive efficiency of 93%!
• Clocking 0-100 kmph in just 6 seconds!

Using the RFLE framework on the 3DEXPERIENCE Platform, one can systematically go through the end-to-end process of designing an electric drive.

RFLE is a framework for Model Based Systems Engineering, which includes 4 pillars:

R – Requirements Engineering; gather, elicit and manage requirements

F – Functional Architecture; define the system services and interfaces

L – Logical Architecture; build the system based on the model

E – Design/Engineering; build the model-based design

Concept Development:

The requirements manager captures the vehicle range requirement of 440 km, time to peak acceleration from 0 to 100kmph < 6 sec and efficiency of > 90% in the ENOVIA requirements management tool on 3DEXPERIENCE Platform. These are mainly marketing and regulatory requirements based on the global electric car market and geographical analysis. Each department further comes up with their own department-level requirements based on these high-level requirements.

System Architecture:

The Systems Architect takes these high level requirements and creates an initial system model using the CATIA Behavior Modeling App on 3DEXPERIENCE Platform. This model consists of the standard sub systems, such as electric drive, battery pack, power electronics and other systems which consume power during the driving of the car. The Architect’s objective is to find the electric motor specifications needed to meet these requirements using a systems simulation. These systems models are run on variety of benchmark drive cycles. The drive cycles are drive paths which cover a variety of turns, ascent and descent, and road conditions to evaluate speed and power requirements, while driving a car on these roads. After solving this initial system model for the above requirements, the Systems Architect takes the decision that he will need an electric motor which will produce a power of 150 KW with a torque of 400 Nm over a range of 15000 motor rpm.

Solution Design:

Going further, the Systems Architect has to finalize the configuration of the motor. He needs to decide if the motor should be single drive i.e., with a single electric motor in front; or dual drive i.e., with two motors, one in front and one in the rear of the car. A single drive reduces the vehicle weight, which reduces the time to reach peak acceleration. A dual drive is energy efficient, however the additional weight reduces the range. To arrive at the design decision involves trade-off between the range and performance parameters.

By performing the trade-off analysis and comparing the parameters of both configurations, a decision is taken to go ahead with a single drive configuration with a range of 443 km, vehicle weight of 1800 kg while achieving a peak acceleration from 0 to 100kmph in 5.73 sec.

Detailed Design and Implementation:

Using the systems model, we are able to determine the torque and configuration requirements of the electric motor. As a next step, we now find out the exact dimensions of the electric motor’s stator and rotor components. These components produce the designed motor torque and speed. The Electrical Engineer runs a design of experiments using the stress and electromagnetic simulations which are executed on the master model in Process Composer on 3DEXPERIENCE Platform. The target is to find the motor geometry configuration which produces a torque of 400 Nm with the stress in the motor shaft to be below 400 MPa. In the DOE, more than 150 design iterations are evaluated for an optimum design of stator and rotor. This study also led to a design where the mass of the rotors was reduced by 10% compared to the initial baseline design.

This master model is further used by other engineers to evaluate other engineering parameters using structural and fluid apps on 3DEXPERIENCE Platform.

• A Thermal Engineer uses this geometry for cooling jacket simulation and to vary the cooling channel turns about the stator to maintain the maximum stator temperature target below 70^o

• The Fluid Engineer changes the number of injectors in this master model to improve the wetted area of the end winding coils to 53% in 3 sec from the baseline of 40% achieving the improvement in cooling of end coils.

• The Lubrication engineer uses the model to visualize the lubrication around the gears and evaluate the shaft churning losses.

This avoids creating multiple geometry models for each design change and in turn multiple import and export issues in different storage systems.

The Noise and Vibration Engineer re-uses the same original model to change the number of casing ribs to meet the surface acceleration requirement. The original mesh gets automatically updated on the changed electric drive design. All originally created simulation features like material data, loads, contact and boundary conditions are automatically updated.

The Structural Engineer has a target to reduce the mass of the bracket and to ensure the same strength and stiffness to keep the stresses within allowable limits. Using the Topology optimization app, the mass of the existing bracket is reduced while making sure that stresses are still within the limits – this is done while ensuring that the location of the bolts for the brackets are still the same. The new bracket design is 18% lighter.

The new design is thus easily replaced, and we are able to compare the new simulation results simultaneously with the baseline design.

Orchestration:

By performing all the detailed engineering simulations and multiple design iterations to achieve targets set by each design department, the System Architect now has a much deeper insight. Based on this data, the Initial system model is updated with the detailed and exact design and result parameters while verifying that the initial requirements are still intact. By running the detailed system model, the final targets are achieved – a new vehicle range of 443 km (requirements >440km), time to achieve peak acceleration as 5.5 sec (against requirement of <6 sec) and electric drive efficiency of 93% compared to requirement of >90%.

The System Architect also creates a traceability matrix which shows how high level requirements are connected to each sub-system design parameter. This provides an insight into the design parameter that needs to be recomputed in case of any change in the high level requirements and vice-versa – i.e., if a design parameter is changed, one can easily compute the impact of this change on the high level requirements.

Design Review and Collaboration:

For a design review and collaboration, the entire project team can view the simulation data through a web browser using 3DDashboard and 3DSWYM tools on 3DEXPERIENCE Platform. The Electric Drive engineer can see the basic report and results using a lightweight Design Review App. The results are shared with the project team through a dedicated community. This helps to get immediate feedback comments from the stakeholders and avoids the need for multiple review meetings.

Project Management:

The Project Management app on 3DEXPERIENCE Platform is used to plan and track all the tasks and also evaluate the dependencies between the different departments. This leads to an effective utilization of the resources while executing the project.

Conclusions:

• The 3DEXPERIENCE Platform provides a complete end to end solution right from requirements gathering to design performance validation
• The Integrated Modeling and Simulation approach on the 3DEXPERIENCE Platform to design the Electric Drive helped us reduce the re-work loops by 80%, which in turn reduced the development cost by >30%
• The time to market is reduced by > 20%
• The number of physical prototypes are reduced by 50%
• Ensures premium quality of products and lowers the warranty costs

With the Electric Drive Engineering industry process experience, one is able to create designs better and faster on the 3DEXPERIENCE Platform. True to our mission of harmonizing Product, Nature and Life!

*Reference IPE:

• Electric Drive Design
• Electric Drive Engineering

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