A control system for a hybrid's electric rear axle
Seven months employed full time in Volkswagen's longitudinal and lateral vehicle dynamics R&D department, writing a bachelor thesis inside a hybrid powertrain pre-development project.
This did not come from an application. It came from a conversation at Ehra Camp, where I was testing the launch control I had written for the Formula Student car and ended up explaining it to a Volkswagen engineer.
What followed was an employment contract: 16 September 2019 to 24 April 2020, full time in Wolfsburg, in the longitudinal and lateral vehicle dynamics R&D department. That distinction matters to me. I was not a student attached to a department for a semester; I was hired, sat inside a pre-development project for a new hybrid powertrain concept, and wrote the thesis out of the work rather than beside it.
Two power sources, one road
The thesis was the design of a control system for the all-wheel drive of a plug-in hybrid with an electric rear axle.
The phrase “all-wheel drive” is doing something unusual there. In a conventional four-wheel-drive car the axles are mechanically coupled — a driveshaft, a centre differential, and physics doing the arbitration. In this architecture there is no shaft. The combustion engine drives one axle, an electric motor drives the other, and nothing connects them except software.
Which means the split is no longer a mechanical consequence. It is a decision, made continuously, between two actuators that could hardly be less alike: an engine that responds in the tens of milliseconds with a torque you can only approximately know, and a motor that responds almost immediately with a torque you know precisely. Getting a car to feel like it has all-wheel drive, when the all-wheel drive is an opinion held by a controller, is a genuinely interesting problem.
I had met its sibling a year earlier. Torque vectoring across four wheel-hub motors on the race car is the same question — not how much torque, but where — with four actuators instead of two and nobody’s comfort to consider.
The work also meant building and running the test procedures, in simulation and on real vehicles, to show the controller did what it claimed. That is the first time I remember the verification half of the job being as much of the work as the design half, which is something I have never since been able to unsee.
The half of my education that happened in industry
Both my degrees ended in a thesis and the two could hardly have been more different.
This one was written inside a company, on a product concept, to a department’s needs, with colleagues who had opinions about it. The master’s thesis four years later was written at TUM’s Chair of Automotive Technology — an academic setting, where the standard is the method and the contribution rather than whether anyone can build with it.
I am glad it happened in that order, and glad it was not the same both times. The industry thesis taught me what a requirement feels like when someone downstream is waiting for the answer. The academic one taught me to defend a method on its own terms.
A patent application came out of this one too — for detecting when a wheel has begun to spin — but that is its own story.