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Award-Winning Simulation System Takes Electric Motor Testing to a New Level

August 2014: Electric motors are paving the road to sustainable transportation. With their long list of highly-desirable benefits – including energy savings, better controllability, less noise and improved air quality – electric motors have been embraced by the vehicle manufacturing industry as a core technology.

According to a report by IHS Technology, over 2.4 billion electric motors were sold to the automotive industry in 2013. Automobiles now have between 25 and up to 100 electric motors on board and that number is only growing.

“Electrification is a key innovative topic not only in the automotive industry, but across the commercial vehicle and aerospace industries,” said Kevin Kott, president of dSPACE Inc., a global producer of engineering tools for developing and testing mechatronic control systems. “Engineers are developing control systems which increasingly rely on electric motors to deliver performance and efficiency. They are converting systems that were previously pneumatic, hydraulic or mechanical due to the efficiency and tight control associated with electric motors.”


It is often noted, though, that this move towards electric actuation increases complexity due to the integration of electrical hardware, software and mechanical systems. This complexity, added with fast response time of the actuation, leads to complexity in the development of controls technology − not only at the actuator level, but also at the system level.

Model-based design (MBD) has proven to be the technology to manage complexity in system design. The advantages of using MBD to increase efficiency in development and reduce costs are quite well known. Combining the advantages of MBD together with advances in powerful semiconductor technology with flexible, fast-computing Field Programmable Gate Arrays (FPGA) opens up a new field of possibilities, with very fast execution speeds leading to precision controls.

 

Simulating Electric Drives

The operational characteristics and overall efficiency of electric motors are defined by electric drive systems. These systems − and in particular their electronic control units (ECUs) and software – determine, with very precise control, how an electric motor will operate by adjusting such things as speed torque, speed current, loading conditions and motor power consumption.

Hardware-in-the-loop (HIL) simulation has become the standard tool for developing and testing electric drives (and their ECUs and software). HIL simulation is highly attractive to developers because it is less costly and time-intensive than test benches and prototype vehicles, and it is capable of testing individual software functions, whole ECUs and even entire ECU networks.
However, the process of testing electric drives is very complex due to the highly-dynamic elements of powertrain electrification.

To meet these challenges, dSPACE recently unveiled a new solution that enables users to test electric drive control systems in a more realistic environment by emulating the real electric motor and generator currents.

 

Emulating Real Motor and Generator Currents

dSPACE has established a virtual, high-fidelity environment for electric motor controller testing that includes a dSPACE SCALEXIO hardware-in-the-loop simulator, a DS2655 field-programmable gate array (FPGA) base module and a scalable electronic load system. This simulation environment was unveiled at the SAE 2014 World Congress in Detroit last April and was recognized with the SAE Tech Award by the editorial staff of Automotive Engineering International magazine.

“Our solution features a robust hardware platform that comes with a wide variety of sensor and actuator signal conditioning that can be directly connected to electric motors,” said Jace Allen, Lead Technical Specialist Simulation & Test Systems, dSPACE Inc. “It uses the latest FPGA technology and enables engineers to test control systems with precision by running electric drive simulations at very fast rates. With this solution, development engineers can simulate not only the normal behavior of an electric motor, but also the abnormal and failure conditions easily and safely in the lab.”
dSPACE’s simulation solution also solves the problem of testing ECUs that come from different suppliers, where there is limited access to all of the internal control signals.

“This reduces the need for expensive prototype hardware and accelerates the development process,” Allen said.

 

 

Advanced Hardware-in-the-Loop Simulation Technology

 

One of the key components of dSPACE’s electric motor controller testing solution is the new hardware-in-the-loop (HIL) simulation technology capabilities that are offered through a dSPACE SCALEXIO® system.

SCALEXIO is a new HIL simulator platform from dSPACE that offers greater versatility, more I/O flexibility and is completely software-configurable.
SCALEXIO systems can be configured and modified quickly and easily to meet the precise demands required for electric motor controller development and testing. SCALEXIO systems can be configured to simulate all the components such as Li-Ion battery pack, Inverter, IC or Jet Engines, Transmission, Driveline, etc. of an electrified propulsion system. This HIL system can be utilized for unit testing of a component of electric drive system or integrated testing of entire subsystem or vehicle. The modular nature of this system allows for scaling of the system to match application requirements. Additionally, capability to introduce electrical failure conditions, such as short to ground, open wire, short to power etc., make it possible to validate software robustness in a variety of abnormal conditions.

These systems can test different variants and types of electronic control units (ECUs), and can be used to test one component or multiple components (e.g. engine or transmission) on a vehicle platform.

And because configuration is completely software-based, system setup or redesign changes are very easy to make.

 

FPGA Programming Made Easy

 

The SCALEXIO DS2655 FPGA base module is user-programmable to define custom models for simulating complex, highly-dynamic systems. It is designed for applications that require very fast, high-resolution signal processing (short simulation cycles, fast calculations and quick I/O access) such as hybrid vehicle applications, electric drive applications, wind energy converters, processor-based motor simulation and FPGA-based motor simulation.

Modules can be added to the DS2655 base board to provide the necessary number of I/O channels. Failure simulation can also be added for each I/O module.

What also makes the SCALEXIO DS2655 FPGA base module unique is that it includes a completely graphically-programmable solution for FPGA-based simulations of electric drives. This dSPACE XSG Electric Components Library features essential function blocks for FPGA programming that are ready-to-use and easy to adapt, making the implementation of FPGA programming easy for developers and users of FPGA applications.

The DS2655 provides the fast reaction times required for simulating electrical machines in closed-loop operation with a controller.

 

Scalable Electronic Load System

 

Electric motors are generally tested using one of three methods: 1) the motor can be put on a dyno, 2) it can be tested completely at the signal level, or 3) you can test the motor on a hardware-in-the-loop simulator and add actual power into the loop, simulating the inverter load.

“This is as close as you can get to testing an actual motor connected to an actual vehicle, but doing it safely in a lab,” Allen said.

dSPACE’s electric motor controller testing solution includes an Electronic Load Module that emulates motor and generator currents at up to 60 V for the HIL simulation of electric motors. The module is ideal for vehicles with 48Velectrical systems or with numerous electric components running in parallel.
The Electric Load Module can be operated in three modes:

  • Current control mode (typically used for motor appli¬cations, not BLDC motors)
  • Voltage control mode (general-purpose applications)
  • Mixed current and voltage control mode (BLDC motor applications)

Typical test application areas are electrically supported steering, starter and generator systems, and mild hybrid drives. Several loads can be operated in parallel to achieve higher electric currents.

 

Conclusion

Developing modern, electrified actuation systems requires sophisticated simulation capabilities in the tool chain to effectively develop and validate control strategies. Advanced high-speed computation of control algorithms and plant models on FPGA-based platforms are true enablers for advancing the actuator technology. dSPACE hardware platforms and software enable easy programming of these models through model-based design and can expedite your controls development project, while saving time and costs.