Adaptable Test Stands Facilitate Complex Testing for EV Drivetrain

May 29, 2024 - Author: Matt Thiel - Director, Integration Engineering, Matt Rodgers - Senior Integration Engineer, Mechanical

Project Features:
E-axle Drivetrain Test Stands, Load Absorber Dynamometers, Open Architecture Real-Time Automation Framework, EV Drivetrain Components


Ev drivetrain and electric dyno assembly

The Challenge

A leading automotive manufacturer needed custom-engineered test stands to develop and validate a new EV drivetrain system. The manufacturer wanted the test stand to accommodate different vehicle track widths to fit front and rear wheel drive configurations and have a two-hour changeover period to switch out the Unit Under Test (UUT).

The company’s initial test procedures targeted durability testing and analysis of power flow and consumption. During the project, they decided they wanted to run more complex testing that replicates a variety of road conditions to enhance their R&D capabilities. This significant scope expansion required the ACS software engineers to redesign the EV testing software to a more sophisticated automated solution.

The manufacturer was also facing personnel shortages and high turnover among the team tasked with operating the complex EV drivetrain test system.

The Solution

ACS initially provided one drivetrain test stand for end-of-line and durability test scenarios, which included a custom-built set of dynamometers and risers, a Data Acquisition (DAQ) interface cabinet, and a control rack with a real-time NI™ PXI processor and customizable test automation software.

A second, identical drivetrain test stand was delivered as part of an additional order, along with an integrated battery emulator power supply system. The end-user supplied the battery emulator for the first test stand. That equipment was aging and suffering significant downtime. Due to the breadth of in-house expertise at ACS, our engineers were able to design and integrate the new equipment with both drivetrain test stands for improved performance.

Due to the company’s evolving requirements for more advanced road simulations and staffing shortages, ACS engineers collaborated closely with their team and engaged in a contract to provide onsite test stand operation support for three years.

Flexibility of ACS Framework Enables Complex Test Automation

To control the test stand and acquire the highly sought product performance data, ACS provided a custom test automation system using ACS’ real-time framework. This framework was designed by ACS engineers to be a modular, flexible platform for real-time test applications. The open architecture of the ACS framework enabled the rapid evolution of the test automation application in response to the manufacturer’s changing needs.

The team integrated a secondary controller to handle the client’s increasingly complex test schedules that outgrew the original architecture’s capabilities. ACS engineers developed drivers to integrate the test stand with the company’s vehicle sub-system controllers, which allowed for the collection of a comprehensive and integrated set of real-world performance data from the road simulations.

For example, the data acquisition system was adapted to collect gigabytes of high-resolution measurement data from uniquely configured torque transducers, one on the electric dyno and one installed between the electric motor and gearbox to isolate torque measurements at specific points in the drivetrain components system. Coordinating the acquisition of the dynamic torque inputs while controlling the electric dyno motors required ACS to develop complex software modifications to handle the logic, math, and input/output mappings in real-time. This customized solution provided visibility of the granular torque data that the client needed to analyze and improve their EV drivetrain configuration.

Physical Design and Capabilities

To enable the test stand to accommodate varying wheel widths, ACS fabricated a linear rail and bearing carriages that allow each electric dyno motor to travel up to 12 inches. Using the adjustment handwheel and lead screw, the operator can easily move the dynos to a different UUT track width within minutes.

The ACS team designed an above-ground bedplate supported by air spring dampeners to achieve proper vibration isolation for precision testing. By using an above-ground design, ACS saved the manufacturer the costly and lengthy demolition and construction project associated with an in-ground bedplate/inertia mass design.

The test stand also includes a variety of mechanical features, including a system of quick-release locks and instrumentation connections that allow the company to achieve a 2-hour turn-around time to switch out the UUT.

The Outcome

The manufacturer received a highly adaptable and robust EV drivetrain test stand solution that seamlessly evolved alongside their changing needs and maturing electric vehicle development process.

A hallmark of the engagement was the highly collaborative relationship between ACS and the manufacturer, with ACS engineers providing onsite technical expertise and support. Initially slated for a 3-6 month commissioning period, the ACS onsite presence was lengthened for the full three years to help the manufacturer as an extension of its staff to help bridge its manpower shortages.

The user-friendly EV testing software and intuitive interfaces designed by ACS allowed the company to onboard test operators quickly and empowered them to take full advantage of the scalable and configurable solution architecture to optimize testing throughout the product design process.

Key Features

  • Two e-axle drivetrain test stands, each with load absorber dynamometers capable of 125kW absorption per wheel, for a total test stand power capability of 250kW.
  • Adjustable wheel track widths with 12-inch dyno travel on linear rails enabling two-hour changeover time.
  • Open architecture real-time automation framework, based on NI LabVIEW software and modular application design.
  • Seamlessly integrated with third-party vehicle control systems, including Speedgoat, dSpace, and single-axis DC controllers such as PI USA positioning systems.

ACS Services

  • Design and fabrication of customized test stand
  • Test automation controls software development
  • Data acquisition integration
  • Long-term onsite technical support and knowledge transfer