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Health-checking electric bus fleet

Kvaser’s CAN-based Memorator data loggers are used to health check Nobina’s electric bus fleet.

The data loggers used in the bus are attached to the vehicle network using a J1939 connector (Photo: Kvaser)

When Nobina, public transport provider in the Nordic countries, added hybrid electric buses to its bus fleet, it became imperative to understand their in-service behavior: Especially when bearing in mind the sheer volume of passengers that rely on the service and thousands of kilometers travelled per day. For this reason Nobina employed a control systems expert as Operating Engineer for its electric vehicles. Typically, in-depth software and hardware expertise aren’t top of the list for new recruits of a bus company, but Mattias Rosengren’s new position might well change that view, said the company.

Nobina’s hybrid buses use a parallel electric powertrain coupled to a diesel engine. The lithium battery enables the buses to drive in full electric mode from standstill up to 20 km/hr, while electronic features a stop-start system that cuts off the engine when the bus is stationary, provides fuel consumption efficiencies and lower carbon emissions. By accessing the vehicle’s CAN, useful data can be gleaned from the tens of connected ECUs (Electronic Control Unit) that make up the bus’s electronic control system, such as the engine, transmission, electronic stability, and battery management systems.

Whether it is the analysis of charging cycles, monitoring driver behavior, or examining battery health, there are plenty of ways in which this data can be used to optimize vehicle efficiency, for the benefit of the environment and the company’s ‘bottom line’.

Another reason for introducing logging capabilities is security. Security-related incidents and driver claims, or intermittent faults caused by individual components, can all be investigated by placing a data logger on the vehicle’s electronic network for an extended period of time and evaluating the results.

Rosengren has put together a test tool chain to study the performance of Nobina’s electric bus fleet and plans to expand the program to the associated charging infrastructure. He explains: “We use an open source engineering tool to simulate, analyze, and test data bus systems, as well as Kvaser’s free Canking CAN monitor and general-purpose diagnostic tool to check the CAN connections. Apart from that, all the software has been developed by myself in-house. For the hardware, we turned to Kvaser, whose CAN interfaces I have used for more than ten years. This time the requirement was for data loggers, so we have opted for the Memorator Pro and Memorator Light models, which are proving very easy to use.”

The Memorator Light has a FIFO function, whereby data is held in a circular buffer and the oldest data is overwritten when the buffer becomes full. This means that the device can be left on the vehicle for a prolonged period and if something happens that requires further investigation, the most recent information is available for analysis. Rosengren notes: “We use the Memorator Pro to capture a particular behavior when we try to replicate the conditions that bring it about.“

The data loggers are attached to the vehicle network using a J1939 connector and is placed in a compartment at the front of the bus. Occasionally, it is necessary to simultaneously gather data from a J1587 network alongside the J1939 one, so a Kvaser Linx J1587 adapter is attached. The data loggers are ‘listen only’, meaning that their presence on the vehicle’s network has no impact on the messages being sent and received. All Nobina’s Kvaser devices has been supplied by Kvaser’s technical associate, Accurate Technologies Sweden, an independent global supplier of control system development tools.

For Rosengren, public transport is someway from his previous role as electrical architecture lead at Swedish supercar manufacturer, Koenigsegg Automotive. At Koenigsegg, where he was responsible for developing the hardware and software for the sportscar’s control systems. Change beckoned for personal reasons; Nobina’s head offices are located closer to Rosengren’s home. According to Kvaser, with a background in vehicle engineering and his R&D experience, Rosengren is well placed to help prepare Nobina’s fleet for the future, whether that fleet is diesel, hybrid or fully-electric, driven, or autonomous.


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