Production fault diagnostics in an M560 used as a hybrid electric vehicle powertrain control module.
A customer using Pi Innovo’s OpenECU platform software and M560 ECU as the hybrid control unit (HCU) for their specialty application, also wanted Pi to develop the supervisory control strategy including comprehensive diagnostics using the J1939 protocol. Pi was responsible for implementing algorithms for system fault detection and maintaining and storing the DTC life-cycle including relevant diagnostic information such as freeze-frames. Fault and diagnostic information reporting to authorized service tools was also implemented in response to diagnostic messages (DMs) as per the J1939-73 standard. All the above needed to be developed inside a Matlab/Simulink environment in compliance with customer's software implementation guidelines.
Pi worked with the customer to determine all the top-level system requirements, including safety goals and functional safely requirements (FSRs). Based on FSRs and technical safety requirements (TSRs), a list of critical system faults that needed to be diagnosed for functional safety and reliable system operation of the HCU was created. For each fault, conditions were identified for detecting, setting and clearing DTCs along with the type of data to be acquired when the fault was set (freeze frame). Remedial action was determined for each fault and implemented.
Some examples of the type of faults diagnosed include:
- Out-Of-Range check, Out-Of-Bound check, Slew-Rate check for analog inputs
- Open and short circuit detection on M560 output pins
- Diagnostics for CAN communication faults like communication errors between other ECUs on the CAN buses
- Redundancy checks of safety critical signals
- Rationality checks for redundant signals
The OpenECU platform provides an extended diagnostics library in a Simulink environment based on J1939 and ISO-15765 standards. The library blocks significantly reduce the development time for implementing the J1939 diagnostics interface in the hybrid vehicle control model. By using the extended diagnostics library, the application developer can focus on implementing the fault detection algorithms without having to worry about the DTC lifecycle maintenance, diagnostic information storage and fault reporting, all of which is entirely handled automatically by the OpenECU platform.