Real-Time CAN FD Communication for E-Drive and Inverter Test Benches

The Challenge: Many Buses, High Real-Time Requirements, Clear System Separation 

Each inverter is connected to the automation system via CAN FD. In addition, measurement, diagnostic, and calibration data are exchanged with the control units via XCP on CAN FD. Depending on the task, other participants such as battery simulators, conditioning units, sensors, actuators, and water cooling are integrated via CAN, EtherCAT, and analog or digital interfaces.
Modern test benches for electric drives don‘t test isolated components. Inverters and control units expect a realistic vehicle and system environment. They require cyclic CAN FD messages, respond to simulated operating states (residual bus simulation), and simultaneously deliver measurement and diagnostic data.

At the same time, battery, cooling, conditioning, sensors, and actuators must be reliably integrated into the test program. For this reason, the CAN-based real-time communication must maintain typical cycle times of 100 Hz, and in many applications even 1 kHz. This corresponds to reaction and processing cycles of 10 ms and 1 ms, respectively. To achieve this, ATESTEO splits the PDES system into two computers. The PDES SIU serves as the Windows front end for operation, visualization, and configuration. The PDES RTU is the isolated real-time unit that executes the test programs. On the RTU, ATESTEO uses Kithara RealTime Suite to run real-time routines under Windows, exchange data via EtherCAT, and perform CAN FD communication via the PEAK cards. User interactions, remote access, and unwanted Windows processes remain separate from the RTU.
 

The Solution: Integrated PEAK CAN FD Hardware as the Interface Between RTU and DUT

In the test bench, the six inverters are located in the climate chamber. CAN FD lines run from the automation cabinet to the test environment, connecting the RTU to the inverters‘ control units. The PDES SIU and the PDES RTU communicate via a peer-to-peer network. The SIU can be connected to the corporate network, while the RTU, as an isolated working machine, executes the test program logic deterministically. The PCAN-PCI Express FD card serves as the RTU‘s central CAN FD interface. In typical test benches, ATESTEO uses up to four four-channel cards, providing up to 16 CAN nodes. For the inverter setup described here, three sets of four CAN FD nodes are provided. Communication includes cyclic CAN FD messages, residual bus and environment simulation, as well as XCP-based data transmission.

For testing specialists, three key characteristics of the PCAN-PCI Express FD card are particularly relevant: high-performance CAN FD communication with up to 64 data bytes per frame, support for both CAN FD and classic CAN, and galvanic isolation between the PC and CAN sides. This allows both existing and new generations of control units to be operated within the same automation architecture. At the same time, the galvanic isolation increases robustness in an environment with power electronics, inverters, and extensive test bench peripherals. The PEAK hardware is also an important building block for Kithara. Kithara RealTime Suite requires a reliable low-level connection to the CAN interface so that real-time communication can be integrated directly into the Windows-based automation environment.
 

The Future: CAN XL Already in Pole Position

The current application demonstrates what is already being achieved productively with CAN FD: parallel communication with multiple inverters, XCP data exchange, deterministic execution of test programs, and integration of additional test bench components. At the same time, the requirements for future generations of control units are increasing. Higher data rates, larger payloads, and more powerful communication structures are becoming more important. This is why PEAK, Kithara, and ATESTEO are already working on integrating CAN XL. ATESTEO plans to incorporate CAN XL into PDES in order to test upcoming generations of control units under realistic test bench conditions. Kithara RealTime Suite is being extended with new CAN standards such as CAN XL and CAN FD light. PEAK provides the hardware foundation, low-level documentation, and interface technology for this. All three companies are thus positioning themselves as pioneers for CAN XL in test bench automation.
 

• Kithara Website
• ATESTEO Website
• PCAN-PCI Express FD Product Page