Electronics takes the blame for Mercedes F1 team’s Canadian stumble
The Canadian Grand Prix, run on Sunday 8th June in Montreal, was expected to place heavy demands on braking systems and was run in hot weather, with high track temperatures. According to team officials, the failures occurred in the high-voltage power electronics package switching power between the on-board battery pack and the axle-mounted motor-generator.
What makes the incident particularly interesting from the electronic systems point of view is the remarkable consistency between two race cars – despite all the other variables in the equation, both units failed within seconds of each other.
This season’s F1 cars are, effectively, assisted hybrids – previously known as KERS (kinetic energy recovery system), a regenerative braking generates power that is stored in a battery pack and is available to boost the 600-plus-HP of the internal combustion engine by around a further 160HP for short durations. This year, the system is called ERS-K, with a separate acronym for MGU-K – the kinetic motor-generator unit.
To minimise weight, with the contribution of the regenerative braking taken into account, designers have reduced the conventional disc brakes on the cars’ rear axles; with the ERS-K offline, extra stress was placed on the regular braking. One of the factors that got Rosberg to the finish line was that the teams adjusted the brake balance from rear to front – not only would Rosberg have had to cope with losing his 160-HP boost-on-demand facility, but the car’s handling would also have been different.
The team’s website commented; “At almost exactly the same time on both cars, we had a failure of the MGU-K control system. Both drivers has the same power units, were racing at the same pace and running at the same temperatures. These temperatures, around the power supply to the MGU-K in particular, were higher than expected. What we didn’t expect is that it would have such a significant impact. The MGU-K shut down on both cars and unfortunately we couldn’t reset it. We keep these things under constant observation and are aware of the points at which they should become critical. In this case it was something we hadn’t experienced before. We’ve been so diligent with this new technology, but then you have one small glitch that can shut down an entire system.”
F1 teams are well used to major revisions between races, if not overnight in some cases; Mercedes may be somewhat constrained by the fact that the electronics package is “standard” across the race teams, according to a specification laid down in the FIA’s rules. It seems a safe guess that as soon as the race was over, a sample MGU-K control system was in an environmental chamber, at the Mercedes team’s base in Brackley, UK – or a contracted test house – being subjected to the same thermal profile the failed units encountered.
It’s not likely that Mercedes will disclose the exact root cause of the system’s errant behaviour, but F1 fans – especially those who are also EEs – will be watching the sport’s rumour mill with interest.
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