Deceleration and compensation for low vacuum levels in a brake-by-wire braking system

The present invention relates generally to a regenerative brake-by-wire braking system that utilizes a vacuum booster. More specifically, the present invention relates to a braking system that compensates for low vacuum levels in the hydraulic brake booster due to the loss of a vacuum source. A system or method for compensating for low vacuum levels in a brake-by-wire system includes continually monitoring the level of vacuum in a vacuum booster. The state or condition of the vacuum source is also monitored to determine whether it is on or off. When the vacuum source is off, the level of vacuum is measured to determine whether it is at or below a critical level. If the level of vacuum is critically low, the vacuum source is turned on. If the vacuum level is not critically low, the hydraulic boost gain is modified in order to provide more braking pressure in response to brake force exerted at the brake pedal.