The Biomechanics of Brake Pedal Feel

Brake pedal feel is arguably the most important driver-facing characteristic of a vehicle’s brake system, as it represents the main interaction between the brake system and the driver and is experienced by the driver in every trip taken. It has traditionally been characterized by three fundamental curves - deceleration versus force at the pedal pad, deceleration versus travel at the pedal pad, and travel at the pedal pad versus force (which is derivable from the other two curves). These characterizations, while useful, stop short of describing what the driver actually experiences - felt through the force in and contraction of his or her leg muscles. When brake pedal feel is traced away from the brake pedal pad and into the driver’s leg, a complex new system emerges, containing the brake system and the biomechanics of the driver. This expanded system is now subjected to - but can also help explain - influences such as seating position, foot position, brake pedal geometry, and the driver’s own biometrics (such as leg lengths and foot dimensions). The present research covers the creation of a simplified biomechanical model of the driver and the brake system, and the use of this model to illustrate the influence of these new elements of the system and human-machine interactions on the driver’s perception of brake pedal feel. Observations are corroborated, to the extent possible while respecting propriety, to human driver feedback from clinics and from the field.