Two weeks ago, I highlighted how Tesla moved from waves to bits in our motor and charge controller in the PEM. You might have left with the impression that as of June 2007, when the DMC replaced the analog controller, our work as DMC firmware engineers was complete. Fortunately for us (this is fun, remember!), that was far from true. Although the inner control loops of the DMC were tuned and functioning well at that point (the motor torque-producing loop and line-voltage syncing charge control loop, for instance), outer loops like cruise control, traction control, and optimal charge profiles were still to be implemented.
Traction control implementation and validation soon became my highest priority, as it was considered to be safety critical. To do so, starting in June 2007, I embarked on a side project, building on Greg Solberg’s former algorithm development in Sweden with EP10. Fundamentally, traction control systems are relatively simple to describe: their goal is to maintain the driven wheel speeds at or near the speeds of the un-driven wheels. The difference between front and rear speeds is referred to as wheel slip. Properly controlling wheel slip can avoid wheel slip-induced yaw while accelerating in turns, or rear-wheel lockup due to regenerative braking (in an EV) or engine compression (in an ICE) on slick road conditions.
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