Some Considerations for Brake-Based Park Systems, Including Residual Drag Impact 2023-01-1878

Brake-based park systems, where an electric parking brake system becomes fully responsible for vehicle immobilization and enables elimination of the traditional driveline-based parking pawl, has increased in popularity, especially in full Electric Vehicles. At face value, the promise of saving mass, cost, and critical packaging space in an electric drive unit is compelling. However, this must be weighed carefully against less obvious impacts, which include engineering in added redundancy, significant changes in “real world” duty cycle of EPB components, risk of brake pad and rotor crevice corrosion, and perhaps most acutely because it affects every drive cycle, the impact to residual drag and therefore vehicle energy use. The present work endeavors to present a balanced view of the considerations, both advantages and tradeoffs, for brake-based park systems, with a special focus on the residual drag behavior because it is perhaps the most difficult to characterize, most variable in its behavior, but most impactful to the vehicle effect.